Methods and apparatus for use in a wireless communications system that uses a multi-mode base station

ES 2 339 976 T3

DESCRIPTION

Procedures and apparatus for use in a wireless communication system using a multimode base station.

Field of the invention

The present invention relates to methods and apparatus for implementing wireless communication systems where the apparatus may include, for example, base stations that support multiple modes of operation and / or wireless terminals for interacting with base stations that support multiple modes of operation.

Background of the invention

Typically, in a wireless communication system, the base stations are on and continuously operate in an active mode of operation. In this active mode of operation, the base station is operated according to a downlink frequency and timing structure, eg, a repetitive frequency and timing structure. Synchronization signals, such as beacon signals and pilot signals, are transmitted in a scheduled manner at associated predetermined power levels. Typically, the power levels and the transmission rate of these sync signals do not vary regardless of the number and / or status of the users that the base station is currently serving. In areas of cellular coverage with a high population density, this is not an important consideration as there are usually at least one or more active users at any given time who are using the base station as their network connection point and communicating data from Username. These active wireless terminals require the full level of sync signals to maintain accurate time synchronization and maintain accurate current channel estimates.

However, in some areas of cellular coverage, such as remote rural areas that have low population densities and / or areas that have charging requirements that vary widely based on time or planning, it would be advantageous to develop procedures and devices that allow to operate a base station, at a certain time and / or under certain conditions, in order to reduce the transmission power and / or reduce the interference generated by the base station. For example, consider that a base station, for example a base station along a railroad in a rural area, may have significant time slots where the base station does not have any registered wireless terminals that need to communicate user data, for example, receive and / or transmit user data. In this situation, during such a time interval, the base station power is wasted as the full set of sync signals is transmitted at normal power levels. In addition, neighboring cells, which can have high population densities and typically have many active users, will be adversely affected by interference from unnecessary sync broadcast signaling. By reducing the level of interference experienced in an adjacent cell, the data throughput in that adjacent cell can be increased, for example, by increasing the coding rate for a given transmit power level and modulation scheme.

It would be desirable for methods and apparatus to be developed that allow broadcast timing signals to be reduced in response to varying system conditions. It would be beneficial if such procedures and apparatus supported at least some of: rapid transition back to full level of sync signals when required, easily detectable wake-up signaling, seamless handover operations, and the ability to switch between different levels of timing. timing signaling based on scheduling information. It would also be advantageous if the methods and apparatus developed to support multiple levels of synchronization signaling were also capable of supporting wireless terminals registered in a wireless terminal sleep state regardless of the level of synchronization signaling. In addition, it would be beneficial if the low level of sync signaling further provide a wireless terminal with the ability to detect the presence of a base station and / or compare the received signal strength from the base station with other adjacent base stations that may be used. potentially as network connection points.

In view of the foregoing, there is a need for new methods and apparatus to implement and support multimode base station operations.

Summary

The present invention relates to methods and apparatus for implementing wireless communication systems where the apparatus may include, for example, base stations that support multiple modes of operation and / or wireless terminals for interacting with base stations that support multiple modes of operation.

In various embodiments of the invention, a base station supports multiple modes of operation, for example, a first mode such as a fully active mode, and a second mode such as a sleep mode. More than two modes of operation may be, and in some embodiments are, supported by the base station, each mode corresponding to, for example, different signaling rates of at least one periodic signal and / or different power levels used to transmit some particular periodic signals such as a group of beacon signals or pilot tones.

ES 2 339 976 T3

By supporting multiple modes of operation, base station control signal transmissions can be reduced when the highest level of signaling is not required, for example, when there is no active wireless terminal in the cell. By reducing base station transmissions in terms of frequency and / or power level, interference with communications in neighboring cells can be reduced. This allows for better performance in a multi-base station system where transmissions by adjacent base stations can interfere with each other. Depending on the particular mode of operation, the base station may support downlink signaling, for example broadcast data transmission but not uplink data transmission which may require a higher level of control signaling. The modes that support downlink and uplink user data communication, for example text data, image data, audio data, and / or user application data, between wireless terminals and a base station typically correspond to one. or more higher modes, eg fully active, of base station operation.

During the different base station operating modes, different signaling levels and / or rates and / or transmit output power are supported depending on the operating mode. For example, in some embodiments, pilot signals and / or various control signals that are not normally transmitted at a first periodic rate in a fully active state are transmitted at a reduced rate during a base station sleep mode of operation compared to a fully active base station mode of operation. In some embodiments, the number of pilot signals transmitted during a sleep mode is reduced during individual symbol transmission time periods during sleep mode of operation compared to fully active mode of operation. In some embodiments, the number of individual symbol transmission time periods during which pilot signals are transmitted during the sleep mode of operation is reduced from the number of individual symbol transmission time periods during which pilot signals are transmitted. in fully active mode of operation, with respect to the same number of OFDM symbol transmission time periods, for example, the same number of successive OFDM symbol transmission time periods representing a grouping in a repetitive downlink timing structure. In some embodiments, during a sleep or partially active mode of operation, the power level at which particular signals are transmitted is reduced compared to the power level used during the fully active mode of operation.

The base station transition between modes of operation can be initiated in a number of ways. The base station can operate in different modes according to a predetermined schedule, for example a train schedule, a switch schedule, or another type of schedule. This scheduling can be designed so that the base station operates in the fully active state at particular known instants of time that typically correspond to periods of wireless terminal data communication activity. As an alternative, or in addition to the scheduled base station modes of operation, in some embodiments, the base stations monitor the activity of the wireless terminals in the cell they serve and adjust the mode of operation to match the detected level of communications data activity. For example, a base station may go from a fully active state to a reduced activity mode of operation with less control signaling in response to the detection of a period when no user data, for example, text, voice or other. user application data types, has been transmitted for a predetermined period of time or when it is determined that the cell does not include any registered or active wireless terminals.

Transitions from a base station sleep mode of operation to a fully active mode of operation are initiated, in some embodiments, by receiving a wake-up signal from a mobile node. Wireless terminal registration signals and / or mobile node requests to go from a mobile node sleep mode of operation to a mobile node active mode of operation in which the mobile node can transmit user data on an uplink , they can serve as trigger signals and / or control signals that are used to cause a change in base station operation from a less active base station mode of operation to a more active base station mode of operation.

The methods and apparatus of the present invention support base stations with different modes of activity. While conservation of transmit power is a benefit of supporting multiple base station modes of operation, the reduced level of signal interference achieved by supporting reduced base station activity modes of operation can increase overall system performance. by decreasing interference to neighboring cells when operating in a dormant state or in another mode of operation with reduced base station activity.

Numerous additional features, benefits, and embodiments of the present invention are discussed in the following detailed description.

Brief description of the figures

Figure 1 is a drawing of an exemplary communication system implemented in accordance with the present invention and utilizing methods of the present invention.

Figure 2 is a drawing of an exemplary base station implemented in accordance with the present invention and using methods of the present invention.

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Figure 3 is a drawing of an exemplary wireless terminal implemented in accordance with the present invention and using methods of the present invention.

Figure 4 is an exemplary time and frequency grid drawing depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the base station that uses those resources during active mode operation.

Figure 5 is an exemplary time and frequency grid drawing depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the a base station that uses those resources during operation in the transmission standby mode, for an exemplary embodiment.

Figure 6 is an exemplary time and frequency grid drawing depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the base station using those resources during transmission standby operation, for another exemplary embodiment.

Figure 7 is an exemplary time and frequency grid drawing depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the a base station that uses those resources during operation in the transmission standby mode, for yet another exemplary embodiment.

Figure 8 is a drawing illustrating an exemplary base station, implemented in accordance with the present invention, currently in an active base station mode of operation, where the base station cell includes active wireless terminals.

Figure 9 is a drawing illustrating an exemplary base station, implemented in accordance with the present invention, currently operating in the transmission standby mode of operation, where the base station cell includes wireless terminals that are disabled, but it does not include any wireless terminals in the sleeping state or in the active state.

Figure 10 is a drawing illustrating an exemplary base station, implemented in accordance with the present invention, currently operating in the transmission standby mode of operation, where the base station cell includes a wireless terminal that is disabled and a wireless terminal that is in the sleep state, but does not include any wireless terminal in the active state.

FIG. 11 is a table drawing illustrating characteristics of base station active mode of operation and base station standby transmission mode of operation for an exemplary embodiment in accordance with the present invention.

Figure 12 is a drawing illustrating an exemplary communication system that includes a train traveling through wireless cells and scheduling information used in switching base station operating modes, the communication system being implemented in accordance with the present invention and using methods of the present invention.

Figure 13 comprising the combination of Figure 13A, Figure 13B and Figure 13C is a flow chart of an exemplary method for operating a base station in accordance with the present invention.

Figure 14 is a drawing of a state diagram for an exemplary base station implemented in accordance with the present invention.

Figure 15 is an exemplary time and frequency grid drawing depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the base station that uses those resources during operation in the standby transmission mode, for yet another exemplary embodiment.

Figure 16 is a drawing illustrating a series of time-sequential operations in an exemplary embodiment of the present invention, the operations including a base station wake-up signaling communicated over a wireless link.

FIG. 17 is a drawing illustrating a portion of an exemplary OFDM uplink frequency and timing structure explaining exemplary base station wake-up signaling in accordance with various embodiments of the present invention.

Figure 18 is a drawing illustrating exemplary access slot uplink air link resources, exemplary segments, and exemplary signaling corresponding to one mode of access.

ES 2 339 976 T3 active base station operation and a base station standby transmission mode of operation, according to some embodiments of the present invention.

Figure 19 is a flow chart of an exemplary procedure for operating a wireless terminal in accordance with the present invention.

Detailed description

Figure 1 is a drawing of an exemplary communication system 100 implemented in accordance with the present invention and utilizing methods of the present invention. Exemplary communication system 100 may be, for example, an orthogonal frequency division multiplexing (OFDM) multiple access wireless communication system. Exemplary system 100 includes a plurality of base stations (BS 1 106, BS M 108), with each BS (106, 108) presenting a corresponding cell coverage area (cell 1 102, cell M 104). The BSs (106, 108) are implemented in accordance with the present invention and support (i) an active mode of operation and (ii) a transmission standby mode of operation. The BSs are connected to each other through a backhaul network. System 100 also includes a network node 110, for example, a router. The network node 110 is connected to (BS 1 106, BS M 108) via the network links (120, 122), respectively. Network link 124 connects network node 110 to other network nodes, eg, other BSs, routers, authentication, authorization, and billing (AAA) nodes, home agent nodes, etc., and / or the Internet. The network links (120, 122, 124) can be, for example, fiber optic links, cable links and / or high capacity radio links such as directed microwave links.

System 100 also includes a plurality of wireless terminals (WT 1 112, WT N 114, WT 1 '116, WT N' 118). At least some of the WTs (112, 114, 116, 118) are mobile nodes that can roam the entire communication system and establish a network connection point through the base station of the cell in which they are currently located. . The WTs (112, 114, 116, 118) can be, for example, cell phones, mobile data terminals, personal digital assistants (PDAs), laptop computers and / or other wireless communication devices that support voice, video, communication. text, messages and / or files. The WTs (112, 114, 116, 118) are implemented in accordance with the present invention to support signaling of wireless communications with the multimode base stations (106, 108).

The WTs (112, 114) are currently located in cell 1 102 and can be connected to BS 1 106 via wireless links (126, 128), respectively. WTs (116, 118) are currently located in cell M 104 and can be connected to BS M 108 via wireless links (130, 132), respectively. The WTs (112, 114, 116, 118) can operate in different states, for example an active state or a sleep state. In some embodiments, the active state of a WT can be further modified so that the WT supports an active operational state and an active standby state.

Figure 2 is a drawing of an exemplary base station 200 implemented in accordance with the present invention and utilizing methods of the present invention. The exemplary BS 200 can be any of the BS (106, 108) of the system 100 of Figure 1. The exemplary BS 200 includes a receiver 202, a transmitter 204, a processor 206, an I / O interface 208, and a memory 210 connected to each other via a bus 212 through which the various elements can exchange data and information. . Receiver 202 is connected to a receiving antenna 203 through which base station 200 can receive uplink signals from a plurality of wireless terminals. The received uplink signals may include, for example, access signals, base station activation signals, handover signals, WT status change signals, resource requests, user data, power control information signals. , time control information signals, reception confirmation signals. Receiver 202 includes decoder 214 for decoding received uplink signals, which have been previously encoded by a WT prior to transmission, for example, to decode an encoded block of user data communicated on a link traffic channel segment. upward. Transmitter 204 is connected to a transmitting antenna 205 through which the BS can transmit downlink signals to the WTs. Downlink signals can include, for example, beacon signals, pilot signals, power control signals, time control signals, registration signals, radiolocation signals, assignment signals, and user data signals. Transmitter 204 includes an encoder 216 for encoding downlink data / information, eg, for encoding a block of user data in a downlink traffic channel segment. In different base station modes of operation, different sets of downlink signals may communicate, different power levels may be used for the same type of downlink signal, and / or the transmission frequency of different signals may be different. The I / O interface 208 provides the BS 200 with an interface to the backhaul that connects the BS 200 to other network nodes and / or the Internet. The signals communicated via the I / O interface 208 may include, for example, scheduling information pertaining to the BS 200 operating mode switching, BS activation signals, forced BS mode switching signals and WT handover signals.

Memory 210 includes routines 218 and data / information 220. Processor 206, eg, a CPU, executes routines 218 and uses data / information 220 from memory 210 to control the operation of base station 200 and implement procedures. of the present invention. Routines 218 include communication routines 222 and base station control routines 224. The communication routines 222 implement the various communication protocols used by the BS 200. The base station control routines 224 include a module.

2 339 976 T3 scheduling module 226, a base station mode transition module 228, an active mode module 230, a transmission standby module 232, a receiver control module 234, a module 236 transmitter control and an I / O interface control module 238.

The scheduling module 226, eg, a scheduler, schedules uplink and downlink segments for the WTs. Planning is a function of the BS 200 operating mode. In some embodiments, when the BS is in the active mode of operation, the BS can schedule uplink and downlink traffic channel segments for the WTs, while when the BS is in the transmit standby mode of operation , the BS does not schedule any uplink or downlink traffic channel segments for the WTs.

The base station mode transition control module 228 controls the transition of the BS 200 between the active mode of operation and the transmission standby mode of operation. Base station mode transition control module 228 uses data / information 220 from memory 220 including mode transition criteria 270, mode transition planning information 269, number of active users 253, time

254 inactivity, access signals 255 received, activation signals 256 received, handover signals 257 received, status change signals 258 received, mode change signals 249 received and / or the current mode 252 to decide whether to carry out perform a transition, and at what time, between the base station operating modes, for example, from active mode to transmission standby mode or from transmission standby mode to active mode. As part of the mode transition process, the mode transition module 228 activates one of the active mode module 230 and the transmit standby module 232, while deactivating the other.

The active mode control module 230 controls BS operations in the active mode of base station operation. Active mode module 230 includes a 1^er synchronization signaling module 240, a traffic channel signaling module 242 and a 1^er radiolocation module 244. The first sync signaling module 240 uses the data / information 220 including active mode sync signal information 272 to control the power level and speed of the sync signals, the sync signals including beacon signals and pilot signals. . In the active mode of operation, at least some of the sync signals are controlled to be transmitted at at least one of: (i) a higher power level and (ii) a higher speed, when the base station is operating in the mode. transmission standby operation. In active mode of operation, base station 200 supports uplink and downlink traffic channel signaling with scheduling module 226 scheduling uplink and downlink traffic channel segments to activate the WTs to which serves BS 200, for example, WTs currently registered with BS 200, operating in an active mode of operation, and currently presenting an active WT user identifier assigned by BS. The uplink and downlink traffic channel segments are used to transmit user data / information. The traffic channel signaling module 242 controls the operations pertaining to the encoding, modulation, and transmission of downlink traffic channel signals and controls the operations pertaining to the decoding, demodulation, and recovery of traffic channel signals from uplink. The 1^er paging module 244 controls paging operations in the active base station mode of operation.

The standby transmission mode control module 232 controls BS operations in the base station standby transmission mode of operation. The transmission standby module 232 includes a second sync signaling module 246 and a second paging module 244. The second sync signaling module 246 uses the data / information 220 including transmission standby sync signal information 279 to control the power level and speed of the sync signals, the sync signals including at least one between beacon signals and pilot signals. In the transmit standby mode of operation, at least some of the sync signals are controlled to transmit at at least one of: (i) a lower power level and (ii) a lower speed, when the base station is operating in active operating mode.

Receiver control module 234 controls the operations of receiver 202; the transmitter control module controls the operations of the transmitter 204; the I / O interface control module controls the operations of the I / O interface 208. In some embodiments, modules 234, 236 and / or 238 co-operate with module 230 in active mode or with transmitting standby module 232 depending on the current mode 252 of operation of the BS.

Data / information 220 includes WT data / information 250, system data / information 251, current mode 252, number of active users 253, idle time 254, and current transmit power information 259. On certain occasions, the data / information 220 may include one or more of the following: information

255 received access signal, received activation signal information 256, received handover signal information 257, received status change signal information 258 and received mode change signal information 249.

The WT data / information 250 includes different information sets at different times depending on the WTs currently served by the BS 200. On certain occasions, the BS may not present any users in the sleeping or active state that are currently logged in. and who is being served. At other times, the BS may present one or more users served by the BS 200, and the data / information 250

WT ES 2 339 976 T3 includes (WT 1 data / information 260, WT N data / information 261), each data / information set corresponding to a WT user currently being served. The WT 1 data / information 260 includes user data 262, WT identification information 264, device / session / resource information 263, and WT user status information 265. User data 262 includes, for example, voice, video, text, data file data, and information intended for WT 1 and / or intended to be sent to a counterpart node of WT 1 in a communications session with WT 1. The WT identification information 264 includes identifiers associated with the WT1, eg, a unique device identifier, a registered user identifier assigned by base station, and / or an active user identifier assigned by base station. The device / session / resource information 263 includes information that identifies the type of WT device, for example, mobile phone, data terminal, model, class, level, etc., session information including, for example, information of routing, peer node identification information, session time information, etc., and resource information including, for example, assigned uplink and / or downlink traffic channel segments, allocated dedicated control channel segments, allocated resources for a paging directed to WT 1, etc. The WT user status information 265 includes information identifying the current operational status of the WT 1, for example, a sleep status, an active operational status, or an active standby status.

The current mode 252 includes information identifying the current operating mode of the BS 200, active mode or standby transmission mode. The number of active users 253 identifies the number of WTs currently registered with the BS 200 in an active operating state. The idle time 254 is a time counter maintained by BS 200 about the amount of time since at least one WT was active from the perspective of BS 200. When the idle time 254 exceeds a threshold of the mode transition criteria 270, the mode transition module 228 causes the BS to go from active mode to transmission standby mode.

The received access token information 255 represents a received request detected for access by a WT, eg, a registration request. In some embodiments, under certain conditions, the received access signal 255 may be used by the transition module 228 to initiate a transition from the standby transmission mode to an active mode of operation. For example, a WT may have entered the BS 200 cell and wish to communicate user data, the BS may be in a standby transmission mode, the Wt may send an uplink access signal during a contention based on access slots, and this received signal can be used as a trigger by the transition module 228 to initiate the transition from the BS 200 to active mode.

The received wake-up signal information 255 represents a detected received request to move the base station from the standby transmission mode to the active mode. For example, a wireless terminal, by monitoring the power level and / or speed of the downlink broadcast sync signals, determines that the BS 200 is in the transmission standby mode but decides that it wants to become a user. active; therefore, the WT sends a wake-up signal to the BS. For example, in some embodiments, a tone or tones at predefined times, within the timing / frequency structure, may be reserved for receiving the trigger signal. In some embodiments, the same air link resources reserved for access signals can also be used for trigger signals. In some embodiments, the activation signal has a different characteristic than an access signal. In some embodiment, the activation signal is the same as the access signal, with the BS 200 treating the received signal differently depending on its current mode 252.

The received handover signal 257 includes information associated with a handover operation. In some embodiments, at certain times, the handover signal can communicate over a wireless link with a WT. In some embodiments, at certain times, the handover signal may communicate over the backhaul via the I / O interface 208, for example, allowing faster and / or more seamless handover operations. The received handover signal information 257 can be used by the BS 200 to update the WT data / information and the number of active users 253. For example, if the received handover signal information 257 indicates that the last current active user is handover to an adjacent base station, the information can be used to update the number of active users 253 and start the inactivity timer 254. As another example, if the received handover information 257 indicates that the last user currently logged into BS 200, for example, a user in a sleeping state, is handover to an adjacent base station, the handover signal information 257 may used to initiate a transition from active mode to transmitting standby mode without waiting for the inactivity delay timer to reach a transition criterion. As yet another example, if the received handover information 257 indicates that an active WT is to be handed over from a BS adjacent to the BS 200, and the BS 200 is currently in the standby transmission mode, the information can be used to initiate a base station 200 transition to active mode, for example, so that BS 200 will operate in active mode when the WT executes handover, providing a more seamless handover operation.

The received mode change signal information 249 includes information received in a forced mode change message, for example, from a central management command node, which commands a base station mode change to be executed. For example, a central management node can order mode changes based on a schedule or based on overall interference levels, load patterns, priority issues, emergency considerations, and so on. As another example, an adjacent base station may send a forced mode change message to BS 200.

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The received state change signal information 258 includes information received from a WT indicating a request for a state change, eg, from sleep to active or from active to user. The operating mode of the BS is consequently affected. For example, if the BS is currently in the transmission standby mode and the BS receives a signal indicating that one of the WTs currently registered but in the sleeping state requests to go to the active state, the transition module 228 can make the station base 200 go to active mode. As another example, if the BS is currently in the active mode, with only one active WT, and that active WT requests to go to sleep, then the BS sets the number of 253 active users to zero and starts the inactivity counter. , which can result in a base station transition to the standby transmission mode if no other WTs become active before a time limit criterion is met.

The current transmission power information 259 is information pertaining to the current transmission of the BS. According to the invention, the average BS transmit power associated with transmitting non-traffic channel signals during the standby transmit mode of operation is reduced compared to the average transmit power associated with transmitting non-traffic signals. non-traffic channels during active operation mode. For example, by reducing the power level of each pilot signal during the transmit standby mode of operation, the average transmit power is reduced. Alternatively, by reducing the number of pilot signal tones per OFDM symbol transmission time interval, for example, from four to one, the average transmission power is reduced. Alternatively, by skipping OFDM symbol transmission time slots during which the pilot signals are transmitted, the average transmission power is reduced.

System data / information 251 includes active mode information 266, transmission standby information 267, uplink and downlink frequency and timing structure information 268, scheduling information 269, transition criteria information 270 mode and power information 271.

Active mode information 266 includes timing signal information 272 including characteristic information associated with timing signals that are generated and transmitted by the BS during active mode of operation. The timing signal information 272 includes beacon signal information 273 and pilot signal information 274. Beacon signal information 273 includes power information 275, for example, a reference power level associated with the beacon signal tone or tones of each beacon signal, and speed information 276, for example, information that identifies the transmission speed of the beacon signal, during active mode. Pilot information 274 includes power information 277, for example, a reference power level associated with pilot tones, and rate information 278, for example, information that identifies which OFDM transmission time slots are used to transmit pilot tones and how many pilot tones are communicated simultaneously in each OFDM transmission time slots where pilot tones are communicated during active mode.

The transmission standby information 267 includes timing signal information 279 including characteristic information associated with the timing signals that are generated and transmitted by the BS during the transmission standby mode of operation. The timing signal information 279 includes beacon signal information 280 and pilot signal information 281. Beacon signal information 280 includes power information 282, for example, a reference power level associated with the beacon tone (s) of each beacon signal, and speed information 283, for example, information identifying speed. beacon signal transmission during the transmission standby mode. Pilot information 281 includes power information 284, for example, a reference power level associated with pilot tones, and rate information 285, for example, information that identifies which OFDM transmission time slots are used to transmit pilot tones and how many pilot tones are communicated simultaneously in each OFDM transmission time slots where pilot tones are communicated during transmission standby mode. In accordance with the present invention, at least some of the synchronization signals transmitted by the base station in the transmission standby mode of operation are transmitted at at least one of: (i) a reduced power level and (ii) a reduced speed , with respect to the active operating mode. This results in a lower average transmit power supplied by the base station during the standby transmit mode of operation, resulting in reduced interference levels from the perspective of adjacent cells that are using the same frequencies.

The uplink and downlink frequency and timing structure information 268 includes, for example, uplink carrier frequency, uplink tone block, downlink carrier frequency, downlink tone block, information uplink tone hopping, downlink tone hopping information, segment definitions in a repetitive frequency and timing structure, beacon signal information, pilot information, OFDM symbol transmission time information, and grouping of OFDM symbols into, for example, half-slots, slots, super-slots, beacon signal slots, ultra-slots, etc. The scheduling information 269 includes stored scheduling information that identifies when to switch the base station from active mode to transmission standby mode. In various embodiments, the schedule information 269 includes data, time, and information correspondingly for a plurality of different times. The planning information 269 may include predetermined schedules and / or schedules that can be adjusted. For example, the BS 200 may be located in a remote region with a low population density and the scheduling information 269 may be based on train schedules or coordinated schedules to result in the base station being in a mode.

ES 2 339 976 T3 active coinciding with the expected presence of a train in the base station cell. Adjustment information can be transmitted to account for delays, canceled trains, and / or unanticipated trains that have been added.

The mode transition criteria information 270 includes information such as the idle time limits used by the base station mode transition control module 228 to determine if and when a mode switch is to be performed. Power information 271 includes BS power information, for example, a reference BS nominal baseline power level, and specific power levels or offsets from the baseline level associated with each of the different types of signals to be transmitted by the BS, eg beacon signals, pilot, quick assignment, regular assignment, radiolocation, traffic channel at various data transmission rates, etc.

Figure 3 is a drawing of an exemplary wireless terminal (WT) 300 implemented in accordance with the present invention and utilizing the methods of the present invention. The exemplary WT 300 can be any of the Wt (112, 114, 116, 118) of the exemplary system 100 of Figure 1.

The exemplary WT 300 includes a receiver 302, a transmitter 304, a processor 306, user I / O devices 308, and a memory 310 connected to each other via a bus 312 through which the various elements can exchange data and information. Receiver 302 is connected to receiving antenna 303 through which WT 300 can receive downlink signals from BS 200.

When base station 200 is in the transmit standby mode of operation, the downlink signals include timing signals, eg, beacon signals and pilot signals at a reduced speed and / or power level. When the base station 200 is in the active mode of operation, the downlink signals include the timing signals, for example, beacon signals and pilot signals at a higher speed and / or power level compared to the mode. transmission standby. Uplink and downlink traffic channel signaling is supported in the active BS mode of operation and the downlink signals also typically include allocation signals and traffic channel signals. Receiver 302 includes a decoder 314 that decodes received downlink signals that have been encoded by the base station prior to transmission.

Transmitter 304 is coupled to transmitting antenna 305 through which the WT 300 can transmit uplink signals to BS 200. In some embodiments, the same antenna is used for both the receiver and the sender. The uplink signals can include access signals, BS activation signals, WT status change request signals, uplink traffic channel segment resource requests, handover signals, power control signals, and time, and user data signals. Transmitter 304 includes an encoder 316 that encodes at least some of the uplink signals prior to transmission.

The I / O devices 308 include, for example, switches, microphone, speaker, display device, numeric keypad, keyboard, touch screen, mouse, camera, etc., and provide an interface for entering user data / information and for transmit data / information received from user. The I / O devices 308 also allow the operator of the WT 300 to control at least some operations of the WT, for example, initiating a call, initiating a request for a mode change, accessing stored information, disconnecting, deactivating, etc.

Memory 310 includes routines 318 and data / information 320. Processor 306, eg, a CPU, executes routines 318 and uses data / information 320 from memory 310 to control the operation of the wireless terminal and implement procedures herein. invention. Routines 318 include communication routines 322, which implement the communication protocols used by the WT 300, and wireless terminal control routines 324. WT control routines 324 include a base station mode determination module 326, an activation signaling module 327, an access signaling module 328, a handover signaling module 330, a state transition module 332 of WT, a timing / synchronization module 333, a base station identification module 334, a receiver control module 336, a transmitter control module 338, and a user I / O module 339.

The base station mode determination module 326 uses the data / information 320 from memory 310 to determine the mode of operation in which the BS that transmitted the received sync signals being evaluated, for example beacon signals and / or or pilot, is currently operating, for example, transmission standby mode or active mode. For example, in some embodiments, a reduced pilot tone signaling rate indicates that the BS is in transmitting standby mode, and the detected rate of received pilot tones is used by module 326 to determine the BS mode. . As another example, in some embodiments, a reduced pilot signal power level indicates that the base station is in the transmission standby mode, and the level of the received pilot signals can be compared to the level of the received beacon signals to carry out the determination. In some embodiments, a detected level variation in the received pilot tones may be indicative of a base station mode change. The BS mode determination module 326 includes one of more than a relative power level determination module 327 and a speed analysis module 329. The BS mode determination module 326 processes received sync signals to evaluate at least one of sync signal power levels and a rate of at least some sync signals. The relative power level determination module 327 determines the level of

ES 2 339 976 T3 relative power between at least two types of received synchronization signals, eg pilot tone signals and beacon signals. Rate analysis module 329 distinguishes between received sync signal rates corresponding to different modes of operation. For example, in some embodiments, the base station uses a different rate of pilot tone signals for the transmit standby mode of operation and the base station active mode of operation, and the rate analysis module 329 measures the rate of received pilot tones and identifies the rate of received pilot tones with a base station mode of operation. In some embodiments, an accurate measurement of the pilot tone rate is not performed, but rather the received signals are processed by rate analysis module 329 to be able to associate a sync signaling level with one of the different modes of operation of Base station. The relative power level determination module 327 and / or the speed analysis module 329 uses as input the information 341 of received synchronization signals and outputs information 347 of processed synchronization signals.

The base station mode decision module 331 determines the base station mode of operation based on the relative power level of at least two different sync signals and / or the rate of at least one type of sync signal. For example, the processed timing signal information 347 transmitted from the relative power level determination module 327 and / or from the rate analysis module 329 is used by the base station mode decision module 331 in conjunction with the BS mode detection information 372 to determine the current operating mode of the base station.

In some other embodiments, the base station mode determination module 326 determines the mode of operation based on a downlink signaling level and / or the omission of one or more of certain types of signals. For example, in some of these embodiments, the base station mode determination module 326 determines the base station mode of operation based on the presence or absence of mapping signals corresponding to link traffic channel segments. upward.

Trigger signaling module 327 controls the generation and transmission of trigger signals to a BS 200, for example, a BS 200 detected by the determination module 326 that is in the transmit standby mode of operation, when the WT 300 wants to wake up the base station, for example to register with the base station, switch to the active state from the sleep state so that the WT can send uplink traffic channel data, etc.

The access signal module 328 controls the generation and transmission of access signals to a BS 200, for example, during predetermined access intervals using predetermined tones in the uplink frequency and timing structure, not requiring the access signals accurate time synchronization and being used to initiate a registration request with a base station. The handover signaling module 330 controls handover operations pertaining to the WT 300 including controlling the generation and transmission of handover request signals to a BS. The state transition module 332 controls the state transition operations of the WT 300 and requests transitions to be communicated with the BS 300, for example, transitions from the sleep state of WT to the active state of WT and from the active state of WT to the sleeping state of WT. In some embodiments, the WT active state is further enabled by including a standby active state and an operational active state. The request for state transitions may include state change request signals and uplink air link resource requests which may be considered, in some embodiments, as a state change request. In some embodiments, the WT state transitions are tracked by the BS and used by the BS to determine the BS mode transitions.

Timing / synchronization module 333 performs time synchronization and frequency synchronization operations, for example, by synchronizing the uplink transmissions of the WTs to synchronize with other WT transmissions according to a timing and frequency structure. uplink that is being maintained by the BS and that is being referenced with respect to downlink signaling timing signals. In some embodiments, the WT obtains an approximate level of synchronization based on received pilot and / or beacon signals and communicates BS trigger signals and / or access signals without the need for a high level of time synchronization. The timing / synchronization module 333 achieves a high level of synchronization, for example, in a cyclic prefix duration, for regular uplink signaling that includes uplink traffic channel signals that are communicated when the base station is in active mode of operation. The base station identification module 334 identifies the base station transmitting the synchronization signals, eg, beacon signals, and the identification may involve determining a network connection point associated with a base station, sector, and / or frequency. carrier. The receiver control module 336 controls the operations of the receiver 302; transmitter control module 338 controls the operations of transmitter 304, and user I / O module 339 controls user I / O devices 308. Some of the WT control modules can act together to carry out a specific operation. For example, the transmitter control module 338 may act in conjunction with the trigger signaling module 327 at certain times.

Data / information 320 includes wireless terminal data / information 336, access signal information 338, base station activation signal information 340, handover signal information 342, state change signal information 344, received sync signals, processed sync signal information, and system data / information 350. WT data / information 336 includes user data 352, device / session / resource information 354, WT identification information 356,

ES 2 339 976 T3 WT user status information 358, base station identification information 360 and base station mode information 362.

User data 352 includes, for example, data corresponding to voice, video, text, files to be communicated to WT 300 peers or to be received from WT 300 peers. The device / session / resource information 353 includes identification information of a WT 300 peer in a communication session with the WT 300, routing information, and air link resource information corresponding to the WT 300, for example, information that identifies downlink and uplink traffic channel segments assigned to the WT 300, when its currently connected BS is in the active mode of operation. The WT identification information 356 includes identifiers associated with and / or assigned to the WT 300 including, for example, a registered user identifier assigned by base station, an active user identifier assigned by base station, paging identifier information, and / or group identifier information. The WT user state information 358 includes information that identifies whether the WT is in a sleeping state or in an active state. In some embodiments, the WT user status information 358 also includes information that further identifies whether the WT is in an operational active state or in an active standby state. The base station identification information 360 includes information that identifies the base station being used as the current network connection point of the WT and / or information that identifies a BS with which the WT wishes to register and use as a point of connection. network connection. For example, base station ID information 360 can be derived from received beacon signals and / or received pilot signals. Base station mode information 360 includes information identifying the mode of operation of base stations, eg, identified base stations. For example, at any given time, a base station may be in the transmit standby mode of operation, for example, a sleep mode of operation that features reduced output signals, lower output power, and generates less interference, or the The base station may be in an active mode of operation, for example, representing a fully operational mode and supporting uplink and downlink traffic channel signaling.

Access signal information 338, including access signal specifications such as, for example, signal characteristics including power level information, modulation signal value information, and extension part information, is used by the access signal module 328 for generating access signals used to register the WT 300 with a base station. The BS drive signal information 340, which includes drive signal specifications such as, for example, signal characteristics including power level information, modulation signal value information, and extension part information, is used by trigger module 328 to generate trigger signals used to trigger a base station that is in a transmit standby mode of operation. The handover signal information 342 includes information used to generate handover signals and information extracted from received handover signals. The state change signal information 344 includes information pertaining to the state changes of the WT 300, for example, information for state change request messages and information indicating that the BS has authorized a WT state change, for example, by assigning the WT an active user identifier.

Information 341 of received timing signals includes information 343 of received beacon signals and information 345 of received pilot signals corresponding to downlink timing signals received by receiver 302. Information 343 of received timing signals is used as input for the relative power level determination module 327 and / or for the speed analysis module 329. Processed timing signal information 347 includes power level information 349 and speed information 351. Processed timing signal information 347 includes information transmitted from the relative power determination module and / or from the rate analysis module 329, which is used as input by the base station mode decision module 331. Power level information 349 includes, for example, a determined power level associated with received beacon signals, a determined power level associated with received pilot tone signals, and a relative power relationship between the two types of received signals. The rate information 351 includes, for example, a determined rate of a type of received signals. In some embodiments, a determined rate of pilot tone signals is, for example, an identified number of pilot tone signals communicated simultaneously in an OFDM symbol transmission time slot. Another example of a given rate of pilot tone signals is, for example, a ratio of a first number of OFDM transmission time slots including pilot tone signals to a second number of OFDM transmission time slots during the which no pilot tone signal is transmitted.

The received beacon signal information 343 in combination with the processed sync signal information 347 includes information pertaining to and / or derived from received beacon signals, for example, the power level of the received signal, tones associated with the received beacon, the time in a timing structure associated with the received beacon signal, the base station, sector and / or carrier associated with the received beacon signal. The received pilot signal information 345 in combination with the processed timing signal information 347 includes information pertaining to and / or derived from received pilot signals, for example, the power level of the received pilot signals, the signaling rate of received pilot signals including the number of pilot signals per OFDM symbol transmission time interval and / or OFDM symbol transmission time intervals including pilot signals, the relative power of received pilot signals with respect to signals beacon numbers received, and / or base station identification information obtained from pilot signals, for example, a base station identifier obtained from a pilot slope.

ES 2 339 976 T3

The system data / information 350 includes a plurality of base station information sets (BS 1 information 364, BS N information 366). BS 1 information 364 includes active mode information 368, standby transmission mode information 370, base station mode detection information 372, uplink / downlink frequency and timing structure information 374, and uplink / downlink information 376. base station identification.

The uplink / downlink frequency and timing structure information 374 includes, for example, uplink carrier frequency, uplink tone block information, uplink tone hopping sequence information, segment information. uplink, downlink carrier frequency, downlink tone block information, downlink tone hop sequence information, OFDM symbol transmission time slot information, OFDM symbol transmission time slot grouping information in half slots, slots, super slots, beacon slots, ultra slots, etc. Active mode information 368 includes information pertaining to active mode relevant segments, signals and functions, eg, traffic channel signals and segments, segments and dedicated control channel signals. The standby transmission mode information 370 includes information pertaining to segments, signals, and functions relevant to the standby transmission mode, eg, signals associated with base station wake-up signaling and wake-up operations. The base station mode detection information 372 includes information used by the base station determination module 326 to evaluate received beacon signals and / or pilot signals to determine the BS mode of operation. The BS mode detection information 372 includes, for example, speed information and / or power level information associated with each BS station mode of operation that can be used to distinguish the different base station modes of operation. For example, the information 372 may include the speed of the pilot signals in each mode and / or the relative power level of the pilot signals with respect to the beacon signals in each mode.

The base identification information 376 includes information that allows the BS ID module 334 to determine the BS corresponding to the received signals, for example, a set of beacon tones that occur at predefined frequencies and / or times within the structure. downlink frequency and timing associated with BS 1 and identifying BS 1 from a plurality of base stations in the system. The identification may include identification of cell, sector and / or carrier frequency used.

Figure 4 is an exemplary time and frequency grid drawing 400 depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the base station that uses those resources during active mode operation. The vertical axis 402 represents the tone index number (0, 1, 2, ..., 15) in the tone block used for downlink signaling by the base station. The horizontal axis 404 represents time, each unit representing an OFDM symbol transmission time interval. Each small square on the grid represents a basic transmission unit, an OFDM tone symbol, corresponding to a tone for the duration of an OFDM symbol transmission time interval. A modulation symbol can be transmitted corresponding to each OFDM tone symbol on the grid. Legend 406 indicates that the total shading of a square on the grid, as shown in legend item 408, means that a beacon tone signal at a power level P_B occupies the tone symbol. Legend 406 also indicates that vertical line shading of a square on the grid, as shown in legend item 410, means that a pilot tone signal at a power level P_P occupies the tone symbol.

Figure 5 is an exemplary time and frequency grid drawing 500 depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the base station using those resources during operation in the transmission standby mode, for an exemplary embodiment. The base station can be the same base station corresponding to the description in Figure 4, but operating in this case in the standby transmission mode instead of in the active mode. The vertical axis 502 represents the tone index number (0,1,2, ..., 15) of the tone block used for downlink signaling by the base station. The horizontal axis 504 represents time, each unit representing an OFDM symbol transmission time interval. Each small square on the grid represents a basic transmission unit, an OFDM tone symbol, corresponding to a tone for the duration of an OFDM symbol transmission time interval. A modulation symbol can be transmitted corresponding to each OFDM tone symbol on the grid. Legend 506 indicates that the total shading of a square on the grid, as shown in legend item 508, means that a beacon tone signal at a power level PB occupies the tone symbol. Legend 506 also indicates that horizontal line shading of a square on the grid, as shown in legend item 510, means that a pilot tone signal at power level P_PR occupies the pitch symbol, where P_PR <P_P. In this exemplary embodiment, reducing the power level of each communicated pilot signal reduces the total average transmit power of the base station in the standby transmit mode of operation relative to the active mode of operation.

Figure 6 is an exemplary time and frequency grid drawing 600 depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the base station using those resources during operation in the standby transmission mode, for another exemplary embodiment. The station

ES 2 339 976 T3 base can be the same base station corresponding to the description in Figure 4 but operating in this case in the transmission standby mode instead of in the active mode. The vertical axis 602 represents the tone index number (0,1,2, ..., 15) of the tone block used for downlink signaling by the base station. The horizontal axis 604 represents time, with each unit representing an OFDM symbol transmission time interval. Each small square on the grid represents a basic transmission unit, an OFDM tone symbol, corresponding to a tone for the duration of an OFDM symbol transmission time interval. A modulation symbol can be transmitted corresponding to each OFDM tone symbol on the grid. Legend 606 indicates that the total shading of a square on the grid, as shown in legend item 608, means that a beacon tone signal at a power level P_B occupies the tone symbol. Legend 606 also indicates that vertical line shading of a square on the grid, as shown in legend item 610, means that a pilot tone signal at power level P_P. 28 successive OFDM symbol transmission time slots are shown in Figure 4. In Figure 4, three of the OFDM symbol transmission time slots include one beacon tone signal and no pilot signals, while the other 25 OFDM symbol transmission time slots each include 4 pilot tone signals. In comparison, in Figure 6, the three beacon signal OFDM symbol transmission time slots remain unchanged; however, the pilot signaling has been reduced. In Figure 6, seven OFDM symbol transmission time slots each include 4 pilot signals, while the other 18 OFDM symbol transmission time slots include zero pilot signals. In this exemplary embodiment, by reducing the speed of the pilot signaling, the total average transmit power of the base station is reduced in the standby transmit mode of operation relative to the active mode of operation.

Figure 7 is an exemplary time and frequency grid drawing 700 depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the base station using those resources during operation in the transmission standby mode, for yet another exemplary embodiment. The base station can be the same base station corresponding to the description in Figure 4 but operating in this case in the standby transmission mode instead of in the active mode. The vertical axis 702 represents the tone index number (0, 1, 2, ..., 15) in the tone block used for downlink signaling by the base station. The horizontal axis 704 represents time, with each unit representing an OFDM symbol transmission time interval. Each small square on the grid represents a basic transmission unit, an OFDM tone symbol, corresponding to a tone for the duration of an OFDM symbol transmission time interval. A modulation symbol can be transmitted corresponding to each OFDM tone symbol on the grid. Legend 706 indicates that the total shading of a grid square, as shown in legend item 708, means that a beacon tone signal at the PB power level occupies the tone symbol. Legend 706 also indicates that vertical line shading of a square on the grid, as shown in legend item 710, means that a pilot tone signal at power level P_P. 28 successive OFDM symbol transmission time slots are shown in Figure 4. In Figure 4, three of the OFDM symbol transmission time slots include one beacon tone signal and no pilot signals, while the other 25 OFDM symbol transmission time slots each include 4 pilot tone signals. In comparison, in Figure 7, the three beacon signal OFDM symbol transmission time slots remain unchanged; however, the pilot signaling has been reduced. In Figure 7, 25 OFDM symbol transmission time slots each include only one pilot tone signal. In this exemplary embodiment, by reducing the speed of the pilot signaling, the total average transmit power of the base station is reduced in the standby transmit mode of operation relative to the active mode of operation.

Figure 15 is an exemplary time and frequency grid drawing 1500 depicting downlink air link resources available to a base station, implemented in accordance with the present invention, and indications of time synchronization signals transmitted by the base station using those resources during operation in the transmission standby mode, for yet another exemplary embodiment. The base station can be the same base station corresponding to the description in Figure 4 but operating in this case in the standby transmission mode instead of in the active mode. The vertical axis 1502 represents the tone index number (0, 1, 2, ..., 15) in the tone block used for downlink signaling by the base station. The horizontal axis 1504 represents time, with each unit representing an OFDM symbol transmission time interval. Each small square on the grid represents a basic transmission unit, an OFDM tone symbol, corresponding to a tone for the duration of an OFDM symbol transmission time interval. A modulation symbol can be transmitted corresponding to each OFDM tone symbol on the grid. Legend 1506 indicates that the total shading of a square on the grid; as shown in legend item 1508, it means that a beacon tone signal at a power level P_Boccupies the tone symbol. 28 successive OFDM symbol transmission time slots are shown in Figure 4. In Figure 4, three of the OFDM symbol transmission time slots include a beacon tone signal and no pilot signals, while the other 25 OFDM symbol transmission time slots each include 4 pilot tone signals. In comparison, in Figure 15, the three beacon signal OFDM symbol transmission time slots remain unchanged, however the pilot signaling has been removed. In this exemplary embodiment, by reducing the pilot signaling rate to zero, the total average transmit power of the base station is reduced in the standby transmit mode of operation relative to the active mode of operation.

ES 2 339 976 T3

Figures 4-7 and 15 have been provided to explain the concepts of sync signaling speed and / or power reduction in accordance with the present invention. The characteristics of the air link resources, the types of synchronization signaling, the amounts of power reduction and / or the amounts of speed reduction may vary depending on the type of system and the specifications of the system.

In an exemplary OFDM wireless communication system for a base station operating in the active mode, for example, a transmission time interval of OFDM symbols has a duration of about 100 microseconds, a block of downlink tones comprises 113 contiguous tones, a beacon signal occupies one tone for two successive OFDM symbol transmission time slots, beacon signals are generated once during a beacon slot of 912 OFDM symbol transmission time slots and 4 pilot tone signals can communicate during each of 896 OFDM symbol transmission time slots during a beacon slot , and the pilot signals account for about 18% of the base station transmit power. In some of these exemplary systems, a base station operating in a standby transmission mode has a reduced level of pilot signaling, for example, one pilot tone signal for every eight OFDM symbol transmission time slots where In active mode, there were previously transmitted pilot tone symbols. This exemplary base station standby mode of operation corresponds to a pilot tone signal for each of 112 OFDM symbol transmission time slots in a beacon slot. In some of these exemplary embodiments, the beacon signaling remains unchanged between the two base station modes of operation. Although the beacon signal is normally transmitted at a power level much higher than that of a pilot signal, it communicates much less frequently and the energy is concentrated in one or a few tones, thus limiting disturbances due to interference. However, the pilot signals communicate much more frequently and consume a significant portion of the base station transmit power during active mode; therefore, reducing or limiting pilot signaling in the standby transmission mode can achieve further beneficial interference reductions. Furthermore, in some of these embodiments, the base station does not transmit downlink traffic signals while operating in the transmit standby mode of operation, thereby further lowering the base station transmit power and interference levels.

In another type of wireless communication system, for example, a CDMA system, spreading code synchronization signals may be used, with the power level and / or the number of spreading code synchronization signals being reduced during operation in the mode. transmission standby operation compared to active operation mode.

Figure 8 is a drawing 800 illustrating an exemplary base station, BS K 804, with a cellular coverage area, cell K 802. Cell K 802 includes two wireless terminals (WT A 806, WT B 807) by way of example coupled to the BS K 804 via wireless links (808, 809), respectively. The BS K 804 may correspond to the exemplary BS 200 of Figure 2, while the WT A and WT B may correspond to the exemplary WT 300 of Figure 3. The BS K 804 is currently in an active base station mode of operation; the WT A 806 is in a WT operational active run state; the WT B 807 is in an active WT standby operating state.

Figure 9 is a drawing 900 illustrating an exemplary base station, BS L 904, with a cellular coverage area, cell L 902. Cell L 902 includes two wireless terminals (WT C 906, WT D 908) as an example. The BS L 904 may correspond to the exemplary BS 200 of Figure 2, while the WT C 906 and WT D 908 may correspond to the exemplary WT 300 of Figure 3. The WT C 906 and the WT D 908 are currently in a deactivated state. There is no WT in the L cell currently serving the BS L 904, and the base station L 904 is currently operating in the transmit standby mode of operation.

Figure 10 is a drawing 1000 illustrating an exemplary base station, BS P 1004, with a cellular coverage area, cell P 1002. Cell P 1002 includes two wireless terminals (WT E 1006, WT F 1008) as an example. The BS P 1004 may correspond to the exemplary BS 200 of Figure 2, while the WT E 1006 and WT F 1008 may correspond to the exemplary WT 300 of Figure 3. The BS P 1004 is currently operating in a transmission standby mode of operation. The WT E 1006 is currently deactivated and is not receiving service via the BS P 1004. The WT F 1008 is currently in a sleep state of operation and is connected to the BS P 1004 via a wireless link 1010. There is currently no WT in cell P 1002 that is being served by BS P 1004 and that is in an active operating state.

FIG. 11 is a drawing of a table 1100 illustrating characteristics of the base station active mode of operation and the base station standby transmission mode of operation for an exemplary embodiment according to the present invention. The first information column 1102 shows information pertaining to the active base station mode of operation. The second information column 1104 shows information pertaining to the base station standby transmission mode of operation. The first row 1106 indicates that in the base station active mode, the BS can serve the WTs that are in the active mode and the WTs that are in the sleep mode, while in the transmission standby mode of operation. BS, the BS can service WTs that are in the sleep mode of operation.

ES 2 339 976 T3

The second row 1108 indicates that the beacon signals are communicated in both the active mode of operation and the transmission standby mode of operation in this exemplary embodiment. In this embodiment, the beacon signaling is the same regardless of the base station mode of operation. In some embodiments, the beacon signal is a relatively high power signal occupying one or a few, eg, two, three, or four tones for some, eg, one, two, or successive OFDM symbol transmission time slots. In some of these embodiments, the other tones in the downlink tone block are left unused during the transmission of beacon signals. In some embodiments, the beacon signaling may be different in the two modes such that power and / or speed is reduced in the standby transmission mode compared to the active mode. In some embodiments, a beacon signal may include one or a few high-power tones and a large number of low-power tones, for example, 25 to 75 tones of a 113-tone block of tones, communicating during the same OFDM symbol transmission time interval (s). In some of these embodiments, in the transmit standby mode of operation, the high power tone may remain unchanged, but the speed and / or power level of the lower power tones may be reduced relative to the active mode.

The third row 1110 indicates that the pilot signals are communicated in both the active mode of operation and the transmission standby mode of operation; however, the transmission rate of the pilot signals and the power level of the pilot signals are reduced in the standby transmission mode relative to the active mode, in this exemplary embodiment. In some embodiments, one of: (i) the pilot signal power level and (ii) the pilot signal rate is reduced in the transmission standby mode of operation relative to the active mode of operation.

Fourth row 1112 indicates that the uplink and downlink traffic channel data are communicated in the base station active mode but not in the base station standby transmission mode of operation, in this exemplary embodiment. .

The fifth column 1114 indicates that the paging signals are communicated in both the active mode of operation and the transmission standby mode of operation. In some embodiments, the radiolocation signaling can communicate at different speeds and / or have different characteristics depending on the base station mode of operation. For example, in active mode, paging opportunities may occur more frequently than in standby transmission mode. In addition, in some embodiments the paging signals in the active mode may convey more information and / or be structured to allow faster response from the WT to which the paging is directed.

Figure 12 is a drawing 1200 illustrating an exemplary communication system implemented in accordance with the present invention and utilizing methods of the present invention. Figure 12 includes a plurality of base stations (BS 1 1210, BS 2 1212, BS 3 1214), each corresponding to an area (cell 1 1216, cell 2 1218, cell 3 1220) of cellular coverage, respectively. Railroad track 1202 is shown with an exemplary train 1204 located on track 1202. In general, more than one train can be running at the same time in the area covered by the communication system. Exemplary stream 1204 includes a plurality of mobile nodes (MN 1 1206, MN N 1208).

The exemplary communication system also includes a network node 1222 connected to (BS 1 1210, BS 2 1212, BS 3 1214) via wireless links (1226, 1228, 1230), respectively. Network node 1222 is coupled to other network nodes and / or the Internet via network link 1232. The network links (1226, 1228,1230, 1232) can be, for example, fiber optic links, cable links and / or high capacity wireless links such as directed microwave links. Network node 1222 includes scheduling information 1224.

The scheduling information 1224 includes train scheduling information, for example, which identifies when a train or trains will be within each BS cellular coverage area. The network node 1222, by communicating the planning information and / or the information obtained from the planning information to the BSs, can influence the switching of the base stations from the standby transmission mode to the active mode and from active mode to transmission standby mode. For example, the network node 1222 can send scheduling information to each BS and the BS can switch accordingly. Alternatively, the network node can use the scheduling information to determine when to issue mode switch command signals to each base station to order base station mode switch operations.

In some embodiments, information obtained from train position detection and / or train tracking mechanisms such as track sensors, for example, already in place and used to prevent collisions, is used to monitor the transition of base stations from active mode to transmission standby mode and from transmission standby mode to active mode. In some embodiments, a controlled base station mode transition of base stations occurs along track 1202, for example, controlled by network node 1222 taking into account the current position of train 1204, direction of train 1204, and train speed 1204.

Consider, as an example, that the area of ​​pathway 1202 that runs through cells 1216, 1218, and 1220 is a fairly remote rural area with a very low population density. In such an embodiment, when train 1204 is not in a cell (1216,1218,1220), it may be advantageous to put the base station (1210,1212,1214) in a

ES 2 339 976 T3 transmission standby mode of operation, thereby reducing transmission power and reducing interference; however, when the train is about to enter or is in the cell (1216, 1218, 1220), it may be advantageous for the base station to be operating in the active mode. In some embodiments, there may be a connection along the track with adjacent base stations that switch between modes as the MN trains (1206,1208) pass from one base station to the next. Reduced interference can be particularly beneficial in cell boundary areas, for example in a cell boundary area bordering a higher population region where another adjacent base station can normally operate continuously in the active mode of operation.

In some embodiments, under certain conditions the base stations are commanded to switch to the standby transmission mode when a train is at or near a specific location, eg, a bridge or tunnel, eg, for security reasons.

The procedures described with respect to the train embodiment of Figure 12 can also be applied to other transport networks. For example, base stations can be located along flight paths and the base station operating mode transition can be coordinated with flight planning information.

Figure 13 comprising the combination of Figure 13A, Figure 13B and Figure 13C is a flow chart 1300 of an exemplary method for operating a base station in accordance with the present invention. The exemplary base station may be base station 200 of Figure 2. The exemplary procedure begins at step 1302, where the base station is activated and initialized. The process proceeds from step 1302 to step 1306, step 1308, and through connection node A 1303 to step 1304.

At step 1306, the base station is set to the active mode and then, at step 1310, the base station is operated in the active mode of operation. The operations of step 1310 include for a first period of time transmitting synchronization signals at a first rate. For example, the timing signals can include a combination of beacon signals and pilot signals. In some embodiments, the active mode of operation can be viewed as a fully operational base station operation state that can support one or more active users and support uplink and downlink traffic channel signaling. The first sync signaling rate may be a rate that supports relatively fast synchronization and channel estimation for the WTs that the base station is serving. The process proceeds from step 1310 to step 1312.

In step 1312, the base station is operated to check if there are any WTs being served in an active state. For example, WTs can register with a base station that they want to use as their network connection point. An exemplary registered wireless terminal may be in different states at different times, eg, a sleep state or an active state; the active state can further be trained to include an active standby state and an active operational state. The BS may control the transition of the WTs to the active state, and the control operations may include assigning active user identifiers to the WTs. The BS can keep track of the number of users that are currently in the active state. If it is determined in step 1312 that there is no WT being served in an active WT state, for example, if no WT currently registered with the BS being served is currently in the active state, then the process proceeds to step 1314; otherwise, the process proceeds to step 1316. In step 1316, the base station, having determined that there is at least one registered WT in the active state, resets the inactivity timer. The process backtracks from step 1316 to step 1312, where the base station again checks to see if there are any WTs being served in the active mode.

In step 1314, the inactivity timer is increased. The process proceeds from step 1314 to step 1318. In step 1318, the base station checks if the idle timer has exceeded a predetermined limit. If the timer has exceeded the predetermined limit, the process proceeds to step 1320; otherwise, the process returns to step 1312, where the base station again checks whether or not there are any WTs being served in an active state.

In step 1320, the base station is operated so that the base station goes into a transmission standby mode of operation. The transmission standby mode of operation is a base station operating state in which the base station does not serve active users but can serve users in a sleep state, and in which the base station is switched off. operates to present a lower average output power than in active mode, thereby creating less interference in the system. The process proceeds from step 1320 to step 1322. In step 1322, the base station is operated in a transmission standby mode of operation that includes a second period of time during which timing signals are transmitted, the timing signals being transmitted to at least one of: (i) a lower speed than in the active mode of operation and (ii) a lower power level than in the synchronization signals transmitted in the active mode. In some embodiments, some of the timing signals, for example the beacon signals, may be the same in both base station modes of operation, while other timing signals, for example the pilot signals, may have a level of lower power and / or speed during transmission standby mode of operation.

ES 2 339 976 T3

Returning to step 1304, at step 1304 the base station is operated to keep track of the current time. The process proceeds from step 1304 to step 1324. In step 1324, the base station checks whether the current time indicates that the base station should change modes based on scheduling information. For example, the BS may be located in a remote rural area and may switch between modes depending on whether a train including mobile wireless terminals is currently close to its cellular coverage area based on train planning information stored in and / or communicated. to the base station. If the current time does not indicate that the base station should change modes, the process goes back from step 1324 to step 1304. However, if the current time indicates that a mode transition should be made based on the scheduling information, then the process proceeds from step 1324 to step 1326.

In step 1326, the base station is operated to determine whether the transition should go to an active mode, in which case the process advances to step 1328, or to a standby transmission mode, in which case the process advances to step 1330. In step 1328, the base station checks if the BS is already in an active state, in which case no further action is required regarding this transition. However, if at step 1328 it is determined that the BS is not in an active mode, then the process proceeds from step 1328 to step 1332, where the base station is operated to go into an active mode. The process proceeds from step 1332 through connection node F 1334 to step 1310, where the base station is operated in an active mode.

Returning to step 1330, in step 1330 the base station checks if the BS is already in a standby transmission mode, in which case no further action is required regarding this transition. However, if in step 1330 it is determined that the BS is not in a standby transmission mode, then the process proceeds from step 1330 through the connection node G 1336 to step 1320, where the base station goes operate to enter the transmission standby mode.

Returning to step 1308, at step 1308 the base station is operated to receive signals over the wireless links and the backhaul interface continuously. The process proceeds from step 1308 to steps (1340, 1348, 1354, 1366, 1367) through connection nodes (B 1338, C 1346, D 1352, E 1364, J 1365), respectively.

In step 1340, the base station monitors access signals from WTs that wish to register with the BS to use the base station as its network connection point. The process proceeds from step 1340 to step 1342, where the base station checks whether or not an access signal has been received. If no access signal has been received, the process returns to step 1340; otherwise, the process proceeds through connecting node H 1344 to step 1328, where the BS checks whether or not the BS is currently in the active mode.

Returning to step 1348, in step 1348 the base station monitors trigger signals, for example, over wireless links from the WTs and / or through the backhaul. An activation signal through the backhaul network may originate from a WT, from a centralized command node, or from another network node such as an adjacent base station. For example, a wireless terminal currently connected to another adjacent BS, which expects to implement handover operations in a short time that will result in a handover to the base station it wishes to activate, can initiate the activation signal and communicate the signal to through your current network connection point. The WT can initiate this wake-up signal to obtain uninterrupted user data communications, and the wake-up signal information is ultimately communicated to the BS in the standby transmission mode over the backhaul network. As another example, a centralized network control node may send a trigger signal to the BS through the backhaul network, for example, the centralized control node that implements the control according to the train scheduling information. As another example, another base station, for example an adjacent base station, realizing that active mobile users are approaching the outer cell perimeter of the BS can send the BS a wake-up signal through the backhaul network, so that the BS can go into active mode and be ready for active mobile users when they arrive at its cell. As yet another example, a WT in the base station cellular coverage area, recently activated or in a dormant state, may have detected that the BS is in a transmission standby mode, so the WT generates and sends a signal of activation to the BS through a wireless channel. The process proceeds from step 1348 to step 1350, where the base station checks whether or not an activation signal has been received. If no trigger signal has been received, the process returns to step 1348; otherwise, the process proceeds through connecting node H 1344 to step 1328, where the BS checks whether or not the BS is currently in the active mode.

Returning to step 1354, in step 1354 the base station monitors handover signals, for example, over wireless links from the WTs and / or through the backhaul network. The process proceeds from step 1354 to step 1356, where the base station checks whether or not a handover signal has been received. If no handover signal has been received, the process returns to step 1354; otherwise, the process proceeds to step 1358. In step 1358 the base station determines whether or not an operational mode change should be implemented as a result of the received handover signal. For example, consider that the received handover signal is transmitted over a wireless link from the last currently registered wireless terminal that is being served by the base station, then after handover is complete the base station can go into the handshake mode of operation. transmission on hold. However, if such a received handover signal was received when the other registered WTs were still in an active state within the cell, a base station mode change would not be appropriate. As another example, consider that the handover signal is transmitted through the backhaul network, indicating that a terminal

The active wireless ES 2 339 976 T3 is desiring to hand over to the base station and that the base station is currently in a transmission standby mode of operation. Under such conditions, it would be appropriate to put the base station into active mode. However, if the base station was already in an active mode when such a handover signal was received through the backhaul, no base station mode transition would be necessary. If at step 1358 the base station determines that a mode change must be performed, the process proceeds to step 1360; otherwise, no further operation is performed to initiate a mode change in response to this received handover signal.

In step 1360, the base station acts depending on the mode transition direction. If the mode transition is to the active mode, the process proceeds from step 1360 to step 1332 through connection node I 1362. If the mode transition is to the standby transmission mode, the process proceeds from step 1360 to step 1320 through the connection node G 1336.

Returning to step 1366, at step 1366 the base station monitors state change signals, for example, over wireless links from currently registered WTs. For example, a registered WT may request to go from the sleep state to the active state so that it can transmit and receive user data. The process proceeds from step 1366 to step 1368, where the base station checks whether or not it has received a state change request signal. In some embodiments, a request for additional air link resources, eg, a request for a traffic channel segment, can be considered as a state change request signal. If no state change signal has been received, the process returns to step 1366; otherwise, the process proceeds to step 1370. In step 1370, the base station determines whether or not an operational mode change should be implemented as a result of the received WT status change signal. For example, consider that the state change signal is from a currently registered wireless terminal being served by the base station in the sleep state requesting a change to the active state and the base station is currently in the transmission standby mode, then the BS must implement a mode change to the active state. However, if such a received WT status change signal was received when the base station was already in the active mode, a base station mode change is not necessary. If at step 1370 the base station determines that a mode change must be performed, the process proceeds to step 1360; otherwise, no further operation is performed to initiate a base station mode change in response to this received WT status change request signal.

Returning to step 1367, at step 1367 the base station monitors mode change signals, for example, a command through the backhaul indicating that the BS should change its operating mode. For example, a network control node or adjacent base station node may have decided to order the BS to temporarily switch from active mode to transmission standby mode due to any of a number of conditions such as interference tests, standby conditions. loading, planning, safety considerations, etc. The process proceeds from step 1367 to step 1369, where the base station checks whether or not a mode change request signal has been received. If no mode change signal has been received, the process returns to step 1367; otherwise, the process proceeds to step 1371. In step 1371, the base station determines whether or not an operational mode change should be implemented as a result of the received base station status change signal. For example, different criteria may be applied for a mode change depending on the source of the mode change signal and the current conditions of the base stations. Some received mode change signals are considered commands that the base station implements without further consideration, while other received mode change signals are considered requests, in which case the station has judgment regarding the mode change. For example, if the mode change command was created by a centralized control node and was issued for security reasons, the mode change can be implemented without additional considerations. Alternatively, if the mode change signal was a suggestion to go into transmission standby mode, based on a schedule, for example a train schedule, and there are additional active registered users outside the train, the base station can ignore the command. If at step 1371 the base station determines that a mode change must be performed, the process proceeds to step 1360; otherwise, no further operations are performed to initiate a mode change in response to this received BS mode change signal.

Figure 14 is a drawing 1400 of a state diagram for an exemplary base station implemented in accordance with the present invention. The exemplary base station may be base station 200 of Figure 2. The exemplary base station includes an exemplary state 1 1402, also referred to as the base station active mode of operation, and an exemplary state 2 1404, also referred to as the transmission standby mode of operation. base station. Arrows indicate conditions to cause a state transition. A state transition from base station active mode of operation 1402 to base station standby mode of operation 1404 may be a response to: a detected idle period 1406, scheduling information 1408, a received base station mode change signal 1409, a detected transition of at least one wireless terminal from the active state to the sleep state 1410, for example, resulting in the transition that all handsets currently registered with the base station are in a sleep mode. A state transition from base station standby transmission mode 1404 to base station active mode 1402 may be a response to: scheduling information 1412, a received access signal 1414, a received activation signal 1416, a received handover signal 1418, a received WT status change signal 1420, for example, a status change request signal, or a received base station mode change signal 1422.

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Figure 16 is a drawing 1600 illustrating a series of time sequential operations in an exemplary embodiment of the present invention. The diagrams (1601, 1603, 1605, 1607, 1609 and 1611) each represent successive time sequential operations for an exemplary A 1602 cell. Diagram 1601 illustrates that cell A 1602 includes exemplary base station A 1604, operating in a transmission standby mode of operation sometimes referred to as a base station sleep mode of operation. For this example BS 1604, when operating in the transmit standby mode of operation, the BS 1604 transmits beacon signals 1606 but does not transmit pilot signals.

Diagram 1603 illustrates that WT A 1608 has entered the cell or activated the cell and has received beacon signal 1606. The WT 1608 identifies the BS A 1604 from the recovered beacon signal information and recognizes that the BS 1604 is in the transmission standby mode, for example, due to the absence of pilot signals.

Diagram 1605 illustrates that the WT 1608 sends a drive signal 1610 to the BS A 1604. The drive signal 1610 is implemented to be easily detected without the need for precise time synchronization, for example, a relatively high power signal in a known location in the uplink frequency and timing structure with a duration of two OFDM symbol transmission time slots. In some embodiments, the trigger signal 1610 is implemented to be easily detected without the need for any timing synchronization between the WT 1608 and the BS 1604, for example, with the BS in the transmission standby mode continuously monitoring certain predetermined tones for a activation signal. In some embodiments, the activation signal 1610 has the same characteristics as an access signal normally used for registration with an active base station.

Diagram 1607 indicates that the base station 1604 has recognized the wake-up signal 1610 and has entered the active mode of operation, for example, by re-activating the normal channels used for signaling user and control data including pilot signals 1612. Diagram 1609 indicates that Wt 1608 has recognized that BS 1604 is in active mode of operation and that WT 1608 has transmitted an access request signal 1614, for example, during one of the access intervals in the structure of Uplink frequency and timing using a contention-based access segment. Diagram 1611 indicates that the conventional registration of the WT A 1608 has been completed and that the BS A 1604 has accepted the WT A 1608 as an active user. BS A 1604 is assigning WT A uplink and downlink traffic channel segments through which user data signals 1616 are communicated.

Figure 17 is a drawing 1700 illustrating a portion of an exemplary OFDM uplink frequency and timing structure. At the base station, the uplink timing may be referred to with respect to the downlink timing, for example with respect to a downlink beacon signal. Vertical axis 1702 indicates uplink tones and includes a block 1701 of uplink tones, eg, 113 contiguous tones. The horizontal axis 1704 represents time. The uplink timing structure includes access slots 1706, 1706 'and regular uplink signaling slots 1708. Access slots, eg, access slot 1706, can be used for access signals, eg, registration request signals and base station activation request signals. In some embodiments, depending on the base station mode of operation, at least some of the access slot tone symbols are used for different purposes. At least some of the signals transmitted by a WT during the access interval need not be precisely time synchronized with respect to the base station, while the signals transmitted by a WT during the regular uplink signaling interval 1708 exhibit usually a precise time synchronization, for example, for a cyclic prefix duration. In some embodiments, the signaling during the access interval uses contention-based segments, while the signaling during the regular uplink signaling interval uses allocated or granted segments. Regular uplink signaling slots can be used for various signalings including assigned uplink traffic channel segment signaling and uplink dedicated control channel signaling.

Figure 18 is a drawing 1800 illustrating exemplary access slot uplink air link resources, exemplary segments, and exemplary signaling corresponding to an active base station mode of operation and a mode base station standby transmission operation according to some embodiments of the present invention. The time and frequency grid 1802 includes 48 tone symbols, each tone symbol represented by a block of small squares and each tone symbol representing the uplink air link resources of a tone for a transmission time interval of OFDM symbols. The time and frequency grid 1802 includes a block 1804 of uplink tones of 16 contiguous tones (tone 0, tone 1, ..., tone 15), and has a time duration of an access interval 1806, where the access slot includes three consecutive OFDM symbol transmission time slots (1808, 1810, 1812). In some embodiments, the access interval has a different duration, for example 8 consecutive OFDM symbol transmission time intervals.

Time and frequency grid 1814 represents time and frequency grid 1802 divided, during active base station mode of operation, to include two access segments. In some embodiments, a portion of the uplink air link resources during the access interval is reserved for access segments. Legend 1816 indicates that the tone symbols that are an element of the 1^er access segment are indicated

ES 2 339 976 T3 by a crosshatch 1820 of diagonal lines, while the tone symbols that are an element of the 2nd access segment are indicated by a shading 1822 of vertical and horizontal lines. During the active base station mode of operation, a wireless terminal wishing to register with the base station and use the base station as its network connection point uses one of the access segments to transmit an access request signal. In some embodiments, the WT randomly selects one of the access segments to be used to communicate its uplink access registration request signal. The time and frequency grid 1814 'represents the time and frequency grid 1814, but also includes an additional access request signal represented with a diagonal line shading 1824. Access request signaling is transmitted at a P level_AC of power per tone and the WT does not need to time synchronize precisely with respect to the base station, for example, the time synchronization error may be greater than an OFDM symbol cyclic prefix duration, but it is small enough such that the access request signal can be recognized by the base station and must be received at the base station within time limits of the access segment.

Frequency grid 1826 represents time and frequency grid 1802 during base station standby transmission mode of operation; grid 1826 includes at least one trigger segment. Legend 1828 indicates that tone symbols that are an element of the activation segment are represented by a hatch 1830 of dots. During the base station standby transmission mode of operation, a handset wishing to activate the base station, resulting in the base station switching from the standby transmission mode to the active mode, uses the activation segment to transmit a signal activation. The time and frequency grid 1826 'represents the time and frequency grid 1826 but further includes an additional trigger signal represented with a shading 1832 of vertical lines. Trigger signaling is transmitted at a P level_Wu for power per tone, where P_Wu> P_AC for the same WT, at the same location with the same beacon signal detected and presenting the same amount of battery power remaining. The WT does not need to be time synchronized precisely with respect to the base station, for example, the time synchronization error may be greater than a cyclic OFDM symbol prefix duration, but small enough that the signal of Activation can be recognized by the base station and must be received by the base station within time limits of the activation segment. According to some embodiments of the present invention, the number of tones currently used for the activation signal is reduced, for example, to one, from the number of tones used simultaneously for an access request signal, allowing the WT to increase significantly. the transmit power per tone of a wake-up signal increasing the chance that a base station will successfully detect a wake-up signal.

In some embodiments in the transmit standby mode of operation, the base station disables all transmit signaling except a minimal set of signaling that the wireless terminals can use to detect the presence of the base station and / or determine a synchronization level. approximate. In some of these OFMD embodiments, this minimum set of signaling is beacon signaling, and the beacon signals can be communicated at the same power levels or at reduced power levels relative to the active mode of operation. In some OFDM embodiments, this reduced set of signals may be beacon signals and pilot signals, the pilot signals being transmitted at a reduced power and / or speed relative to signaling in the active mode. In some embodiments, a wireless terminal after having detected the base station, for example through a received beacon signal, and wishing to activate the base station, sends an activation signal to the base station; the base station, upon detecting the activation signal, reactivates the normal channels by causing the base station to go into an active mode of operation. In various embodiments, the drive signal is designed to be easily detected without the need for time synchronization or precise time synchronization. For example, in an exemplary OFDM embodiment, the trigger signal may be a two symbol tone at a known location in the uplink frequency and timing structure. In some embodiments, the trigger signal may be a signal communicated at a relatively high uplink transmit power level, the signal having a longer duration than the normal modulation symbol value intended for a single OFDM tone symbol and communicating the signal in two or more consecutive OFDM symbol transmission time slots. In some embodiments, a regular access signal may be considered a wake-up signal if the base station receiving the signal is in a transmit standby mode of operation. In some embodiments, the same air link resources reserved for the access signals can be reserved and used for the activation signals. In some of these embodiments, the access signals may be different from the trigger signals.

Figure 19 is a flow chart 1900 of an exemplary method for operating a wireless terminal, eg, a mobile node, in accordance with the present invention. The exemplary operating procedure including establishing a user data channel with a base station for uplink data transmission begins at step 1902. For example, a wireless terminal may have been activated and initialized in step 1902 and wish to establish an uplink communication link with a base station network connection point corresponding to the cellular coverage area in which it is located. As another example, a wireless terminal may currently be registered with a base station in whose cell it is located, but may be in a WT sleep state, and at step 1902 it begins to initiate operations to transition to a WT active state. As another example, a wireless terminal may currently be an active user with a base station network connection point, located adjacent to the new base station with which it wishes to establish a user data channel, and the wireless terminal enters in a border region. The process proceeds from step 1902 to step 1904.

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In step 1904, the wireless terminal determines whether the base station with which it wishes to establish a user data channel is in a low activity operating state. Step 1904 includes a substep 1906 and a substep 1908. In substep 1906, the wireless terminal receives synchronization signals from the base station. Then, in sub-step 1908, the wireless terminal determines the base station mode of operation based on the received sync signals.

In some embodiments, sub-step 1908 includes sub-step 1910, where the wireless terminal evaluates signal power levels to determine a base station mode of operation. In some embodiments, higher signal power levels of at least some types of sync signals are indicative of a fully active base station mode of operation, while lower signal power levels of the same type of sync signals are indicative of a reduced timing signaling mode of operation, eg, a base station sleep mode of operation. In various embodiments, the timing signals include at least two types of signals and the relative power of the two types of signals is indicative of a base station mode of operation. In some of these embodiments, the at least two types of signals include a first type of signal that is an OFDM beacon signal and a second type of signal that is a pilot tone signal, and the beacon tone signal has a power per tone of at least three times the signal strength per tone of a pilot tone signal. In some of these embodiments, the transmit power level per OFDM beacon signal tone is the same in both the base station sleep mode and the base station active mode; however, the transmit power per pilot signal tone is reduced in the base station sleep mode of operation relative to the active base station mode of operation.

In some embodiments, substep 1908 includes substep 1912 in which the wireless terminal determines the rate at which a first type of sync signals is received and correlates the determined rate to a corresponding base station mode of operation. In some of these embodiments, the first type of timing signals are pilot tone signals. In some of these embodiments the base station is determined to be in a reduced sync signaling mode of operation, eg, a base station sleep mode of operation, when the determined speed is below a predetermined threshold.

The process proceeds from step 1904 to step 1914. In step 1914, operation of the wireless terminal continues along different paths depending on whether or not the base station is in a low activity state of operation. If the station is in a reduced activity state, for example, a base station sleep operating state, then the process proceeds from step 1914 to step 1916; however, if the base station is not in a reduced activity state, eg, the base station is in a fully active base station mode of operation, then the process proceeds from step 1914 to step 1926.

In step 1916, the wireless terminal transmits a signal used to cause the base station to go into a more active mode of synchronization signaling, for example, transmits an activation signal, an access request signal, an activation signal. handover or a state transition request signal.

In some embodiments, a signal used to move the base station into a more active mode of timing signaling is a wake-up signal. In some of these embodiments, the characteristics of the wake-up signal are to provide easy detection by a base station in the sleep mode. In some embodiments, the trigger signal includes less than 5 OFDM tones. In some of these embodiments, the trigger signal uses a single OFDM tone. In various embodiments, the drive signal is transmitted for a continuous period of time that lasts longer than one OFDM symbol transmission time period. In various embodiments, the trigger signal is transmitted such that the signal occupies more than a single OFDM transmission time slot, for example, 2 successive OFDM symbol transmission time slots, and the wireless terminal does not need to be synchronized in the time accurately relative to the base station, for example, the time synchronization error may be larger than a cyclic OFDM prefix but is small enough that the trigger signal can be detected by the base station, for example the handset is synchronized with the base station in a time interval transmission of OFDM symbols. In some embodiments, a predetermined set of tones is used for the trigger signal. In some embodiments, the predetermined set of tones includes at most one tone. In various embodiments, the activation signal is transmitted by the wireless terminal at a power level per tone that is higher than the average power level used by the wireless terminal to transmit user data. In some of these embodiments, the activation signal is transmitted by the wireless terminal at the highest power level per tone used by the wireless terminal. In some embodiments, the activation signal is communicated using one of the tones used for signaling access requests.

In some embodiments, a signal used to move the base station into a more active synchronization signaling mode of operation is an access request signal, and the wireless terminal operates differently after transmission of the access request signal if the transmission of the access request signal was for a base station in a reduced mode of sync signaling than if the transmission was for a base station in a fully active sync signaling mode of operation. In such an embodiment, the base station implements different processes in response to the received access request signal depending on the current operating mode of the base station.

ES 2 339 976 T3

In some embodiments, where the wireless terminal is currently connected as an active user via a wireless link to a current base station located adjacent to the base station that the wireless terminal wishes to activate and with which it wishes to establish a channel user data, a signal used to move the base station into a more active sync mode of operation is transmitted through the current base station as part of a handover operation. For example, a wireless terminal may be in a cell boundary sector or region and anticipate switching base station network connection points and therefore transmit such a signal to its current network connection point, and the signal can be forwarded, for example, through the backhaul network to the base station that needs to be activated. In this way, handover delays can be minimized.

In some embodiments, where the wireless terminal is already registered with the base station that the wireless terminal wishes to transition to a more active synchronization signaling mode and where the wireless terminal is in a wireless terminal sleep mode in that the wireless terminal does not transmit user data, the signal used to cause the base station to go into a more active synchronization mode of operation is a state transition request signal, for example, a request from the wireless terminal to switch from a sleep mode of WT to an active mode of WT.

The process proceeds from step 1916 to step 1918. In step 1918, the wireless terminal waits for a period of time for the base station to go into an active state. In some embodiments, the wireless terminal monitors a change in base station signaling, for example, with respect to the speed and / or power level of the base station signaling to confirm that the base station has entered the state active operation. In some embodiments, the wireless terminal repeats the expected signal to cause the transition if a base station mode transition has not been observed in a predetermined period of time, for example, in a number of OFDM symbol transmission time slots, or at an expected point in the timing structure, for example, the beginning of the next slot in the downlink timing structure after allowing signaling transmission times and base station mode transition operations.

Then, in step 1920, the wireless terminal transmits access request and / or registration signals to the base station, for example, access request signals using a contention-based access segment in a timing and frequency structure. uplink associated with the base station. For example, for a wireless terminal new to the cell, a complete registration sequence and access request signaling can be generated. However, for a handset currently registered with the base station, but in WT sleep mode, the WT may have a registered user ID but may wish to acquire an active user ID and can initiate a closed loop time synchronization. .

The process proceeds from step 1920 to step 1922, where the wireless terminal performs closed loop time control based on feedback signals from the base station. In some embodiments, where the wireless terminal is handover between two base station network connection points corresponding to the same cell, for example, two sector connection points of the same base station or two frequency connection points of corresponding to the same sector of the same base station, some or all of the time synchronization operations may be omitted. In some embodiments, a closed-loop power control pertaining to the wireless terminal transmit power level is also performed.

Then, in step 1924, the wireless terminal initiates transmission of user data to the base station. For example, the wireless terminal may have previously been assigned a base station active user identifier, for example, in step 1920, the base station scheduler may have assigned one or more uplink traffic channel segments to the terminal. wireless, and the wireless terminal transmits user data using the assigned uplink traffic channel segments.

Returning to step 1926, in step 1926, the wireless terminal initiates registration and / or access operations and then, in step 1928, the wireless terminal performs closed-loop time control based on feedback signals. from the base station. The process proceeds from step 1928 to step 1930. In step 1930, the wireless terminal initiates transmission of user data to the base station.

Although described in the context of an OFDM system, many of the methods and apparatus of the present invention can be applied to a wide range of communication systems including many non-cellular and / or non-OFDM systems.

In various embodiments, the nodes described in this document are implemented using one or more modules to carry out the steps corresponding to one or more procedures of the present invention, for example, the transition between two base station modes of operation, the operation in a base station active mode of operation, operation in a base station standby transmission mode of operation, determining a base station mode of operation, signaling to cause a mode transition, processing signaling related to mode transition, deciding whether or not to implement a mode transition, and so on. In some embodiments, various features of the present invention are implemented using modules. Such modules can be implemented using software, hardware, or a combination of software and hardware. Many of the procedures or procedural steps described above can im

ES 2 339 976 T3 be implemented using machine-executable instructions, such as software, included on a machine-readable medium such as a memory device, for example, RAM, floppy disk, etc., to control a machine, for example, a general purpose computer with or without additional hardware, to implement all or part of the procedures described above, for example, in one or more nodes. Accordingly, among other things, the present invention is directed to a machine-readable medium that includes machine-executable instructions for causing a machine, for example, a processor and associated hardware, to perform one or more of the steps of the ( of the) procedure (s) described above.

Numerous additional variations of the methods and apparatus of the present invention described above will be apparent to those skilled in the art in light of the foregoing description of the invention. Such variations should be considered within the scope of the invention. The methods and apparatus of the present invention can be used, and in various embodiments are used, with CDMA, orthogonal frequency division multiplexing (OFDM), and / or various other types of communication techniques that can be used to provide wireless communication links. between access nodes and mobile nodes. In some embodiments, the access nodes are implemented as base stations that establish communication links with mobile nodes using OFDM and / or CDMA. In various embodiments, the mobile nodes are implemented as calendar-size computers, personal data assistants (PDAs), or other portable devices that include receive / transmit and logic circuits and / or routines, to implement the methods of the present invention.