Methods and apparatus for selecting between multiple carriers using a single receiver chain tuned to a single carrier

METHODS AND APPARATUS FOR SELECTING BETWEEN MULTIPLE CARRIERS USING A SINGLE RECEIVER CHAIN TUNED TO A SINGLE CARRIER

FIELD OF THE INVENTION The present invention relates to communication systems, particularly methods and apparatus for selecting between multiple carriers in wireless communication systems using a single receiver tuned to a single carrier.

The use of different carriers in different parts of the communication system may be advantageous in terms of feasibility as it may advantageously minimize signal interference through the use of different carriers. A spread spectrum wireless communication system may use different carriers throughout the system, and each carrier is associated with a different frequency band. In some wireless communication systems, different cells and/or sectors use different frequency carriers. In some systems the same sector or the same cell uses different carriers each having an associated frequency, where the available bandwidth in one cell or sector is divided into different frequency bands, for example individual frequency bands.

Wireless Terminals (WTs), e.g. mobile nodes, can move throughout the communication system and can establish connections with a given sector/cell base station, e.g. using a specific carrier frequency and associated band for downlink signaling. have. As conditions change, e.g. due to changes in loading conditions, an increase in users on carrier frequencies, changes in interference levels, or WT movement, cell/sector boundaries, the WT transfers to another carrier and uses other carriers corresponding to the base station transmitter. Reaching a cell/sector/carrier frequency combination is advantageous or necessary. In generally known systems, many wireless terminal receivers use a single receiver chain and the wireless terminal maintains the same carrier until forcibly switched over, for example, by loss of communication with the base station. This approach is undesirable. This is because as the WT moves across the system, it experiences loss of communication at the boundary and changes in reception quality, for example, fading. Other known receivers use a single receiver chain, where the receiver interrupts communication with an attached base station transmitter and switches from the active carrier in order to search for and evaluate other potential carriers. In this way, the WT disconnects normal communication sessions during the search period and spends time re-tuning a filter, e.g. an RF filter, for tuning for each frequency selection, waiting for a detected carrier, e.g. with pilot signals and It is not desirable because it consumes time to collect and evaluate some received signals, and then to re-tune to the original carrier setting.

As noted above, it is apparent that there is a need for an improved method and apparatus that provides for the efficient design and operation of a wireless terminal receiver. It would be advantageous if such an apparatus and method allowed an estimate of the quality of two different channels simultaneously using many different carrier frequency bands without disrupting the communication session. In addition, such a method provides continuous tracking for different carriers and allows the wireless terminal to select a carrier frequency/cell/sector base station attachment point, to switch before loss of communication, and to ensure that switchover occurs at a convenient point in time, other considerations e.g. For example, it would be advantageous to allow switching based on system load conditions.

Various embodiments of the present invention relate to wireless communication systems, such as spread spectrum OFDM and/or CDMA systems, that use multiple carriers, for example, in a system in which the total available bandwidth is divided into different frequency bands, wherein each band is associated with the carrier frequency. Different cells in the system may use different carrier frequencies, and different sectors of the same cell may use different carrier frequencies. In some embodiments, the same sector of a cell may use different carrier frequencies, such as different power levels, which provides additional diversity and additional base station connection alternatives, such as alternative attachment points for traffic channel signaling.

The present invention provides a method according to the present invention in multi-cell multi-sector wireless communication systems using multiple carrier frequencies. to wireless terminal receivers accommodating the carrier frequency selection methods . According to the present invention, the WT may comprise a single receiver chain, for example with a single RF module, alternatively as a carrier and associated band used by the WT to receive downlink specific signaling in relation to a specific base station transmitter. It can process information about multiple alternative carriers that can be selected. Although the wireless terminal receiver is tuned to a single band at a particular time, an estimate of the channel quality corresponding to the currently used carrier and the alternative carrier is generated in accordance with the present invention without switching between carriers. This method of the present invention allows the WT to stop processing the normal downlink traffic channel signal for the currently selected carrier frequency, switch to a potential alternative carrier, monitor the signals, perform measurements used in evaluation, and switch back to the original carrier. This is in contrast to known search and evaluation techniques that use a single receiver chain. The present invention method can reduce disconnection during ongoing communication sessions, facilitate continuous WT tracking of alternative carriers, and eliminate the need for handoff before shorting of communication or degradation to an unacceptable level of WT. can inform the mobile station, can efficiently perform handoff with minimal disconnection in a timely manner between different base station access points as the wireless terminal moves throughout the system, and/or balance the system loading on other carriers. can be used to maintain

In some embodiments, base station transmitters in other cells and/or other sectors, such as other neighboring cells and/or other neighboring sectors, primarily transmit using different carrier frequencies but periodically using the carrier frequency of the neighboring sector. Mobile node receivers according to the present invention use a single chain with a removable filter, such as a controllable RF filter, for receiving and processing a signal, such as a composite signal, from a plurality of different transmitters within a first selected carrier band, said The signal includes two components: a first signal component identified in the first currently selected band and a second signal component identified in a second alternative band. Separate quality indicator values are obtained from the first and second signal components and compared, and a determination is made as to whether the controllable filter of the receiver should be switched to the second band.

Wireless terminals, such as mobile portable communication devices, implemented in accordance with various embodiments of the present invention include a receiver antenna; a controllable filter connected to the antenna, a first signal measuring device connected to the controllable filter, a second signal measuring device connected to the controllable filter, and a frequency band selection module. Each WT' receiver antenna is used to receive a signal, for example a composite signal comprising a first component and a second component. In some embodiments, a signal, such as a composite signal, is received over a period of time and the first and second signal components are received at different times. A controllable filter, e.g., an RF bandpass filter in a controllable RF module comprising a mixer, removes at least a portion of one of the first and second frequency bands while removing at least a portion of one of the first and second frequency bands. pass the signals of The first and second signal components are within a selected one of the first and second frequency bands. The first signal component is associated with the first frequency band, and the second frequency component is associated with the second frequency band. In some embodiments, the controllable filter is a passband filter, the first and second frequency components have a narrow frequency width compared to a width of the controllable filter, and the first and second signal components pass through the controllable filter It has a width less than 1/2 of the bandwidth. In some embodiments, for example in any OFDM embodiments in which the first and second signal components are received as high power signals, such as easily detectable beacon signals, the first and second signal components are It has a frequency width of up to 1/20 of the passband.

The first signal measuring device performs a first signal measurement on the first signal component to generate a first signal quality indicator, and the second signal measuring device performs a first signal measurement on the second signal component to generate a second signal quality indicator. A second signal measurement is performed. In some embodiments, the first signal measurement device may measure the signal energy SNR and determine an error rate for WT specific signals, such as downlink traffic signals intended for a specific WT, as well as broadcast signals. , for example assignment signals, pilot signals and/or beacon signals, wherein the second signal measuring device determines broadcast signals, eg beacon signals, pilot signals and/or assignment signals intended to be received by multiple devices. Energy detection and/or SNR detection are performed on the . The frequency band selection module selects between operation in the first frequency band and operation in the second frequency band as a function of the first and second quality indicator values, the first and second frequencies to be passed by the controllable filter. Generates a control signal used to control, eg, select, one of the bands.

A base station disposed in a communication cell according to various embodiments of the present invention includes a first transmitter for transmitting first signal components mainly transmitted in a first frequency band. The base stations may facilitate sectorized operations and may include a first transmit antenna coupled to a first transmitter and directed towards a first sector of a cell transmitting a first signal component. Moreover, such a sectorized base station includes a first transmitter coupled to a second transmit antenna. The first transmitter mainly transmits in the first frequency band, but during some time the first transmitter operates, the second transmitter transmits the second signal component in the first frequency band according to the present invention. The second transmitter corresponds to a different sector of the cell than the sector corresponding to the first transmitter. The second transmit antenna is directed to the second sector of the cell transmitting the first signal component. The first and second sectors are located in different physical areas of the cell, such as adjacent areas where some may overlap.

According to some embodiments of the present invention, a further base station, eg a second base station, is located in a corresponding second cell, eg a cell adjacent to and/or partially overlapping the cell corresponding to the first transmitter. This additional base station is used for transmitting signals primarily in its own primary frequency band, if necessary, for example in a frequency band periodically used as the primary band of an adjacent cell transmitter, eg in the primary band of the transmitter. It may include a transmitter and a transmit antenna. These temporary signals may be received by the WT and evaluated as a second signal component of the received signal.

In some embodiments, the first and second frequency bands are at least 1 MHz wide. For example, the first and second frequency bands may be 1.25 MHz frequency bands as part of 5 MHz using three or four other 1.25 MHz bands throughout the system. In various systems, using frequency bands of at least 1 MHz, the receiver's removable filter has a passband no more than 2 MHz wide.

In various embodiments, the controllable filter may be, for example, a baseband filter or an I/F filter. The filter may be a digital filter that receives information corresponding to a frequency range wider than the selected frequency band and discards, for example, does not process information outside the selected frequency band.

In some embodiments, the controllable filter used for band selection is implemented after FFT. In such cases, FFT results for frequencies outside the selected band may be computed as a result of filtering but will not be used. In such embodiments, the physical filter of the RF module may be fixed but not controllable, and signals from one or more bands are passed by the physical filter. In one such embodiment, after FFT, tones out of the selected band are removed by the digital signal processing module and/or other controllable module. In such embodiments, the module that removes information and/or tones outside the selected band is a controllable filter and operates in response to a band select control signal. Various embodiments of the present invention relate to communication methods of receiver operation used to select between multiple frequency bands. The receiver may be, for example, a receiver in portable mobile radio terminal communications devices.

A typical method according to the invention comprises the steps of receiving a signal, for example a composite signal comprising a first signal component and a second signal component, said first and second signal components being within a first frequency band; operating a passband filter to pass the first and second signal components; performing a first signal measurement on the first signal component to produce a first signal quality indicator value; performing a second signal measurement on the second signal component to produce a second signal quality indicator value; and selecting between operation in a first frequency band associated with a first signal component and operation in a second frequency band associated with the second signal component as a function of the first and second signal quality indicator values. do. In various embodiments, the first frequency band is outside the second frequency band, eg, the first and second frequency bands may be separate non-overlapping 1.25 MHz frequency bands within a 5 MHz communication system.

According to at least one exemplary method of the present invention, a first transmitter, eg a first base station transmitter transmitting primarily in a first frequency band, is operated to transmit a first signal component. The first signal component may be a downlink traffic signal, an assignment signal, a pilot signal and/or a beacon signal. The method further comprises operating a second transmitter, eg another base station transmitter, which transmits primarily in a second frequency band, for example to periodically transmit a second signal component in the first frequency band. The second signal component may be, for example, a broadcast signal, such as an assignment signal, a pilot signal, a beacon signal, or the like.

In some embodiments, the first transmitter and the second transmitter are disposed in different sectors of the same cell, the first signal component being transmitted using the first antenna corresponding to the sector of the same cell while the second signal component is transmitted using the second antenna corresponding to the second sector of the same cell. In some embodiments, the first transmitter and the second transmitter are arranged in different cells, wherein the first signal component is transmitted using a first antenna corresponding to the first cell, while the second signal component is transmitted in the second cell. is transmitted using the second antenna corresponding to .

In some embodiments, a signal, eg, a composite signal from two transmitters, is received over a period of time and the first and second signal components are received at different times.

The first and second signal components have a narrow frequency width compared to the width of the passband filter. For example, in some embodiments, the first and second frequency components have a frequency width of at most 1/20 the frequency width of the passband filter.

In some embodiments, the first and second frequency bands may be at least 1 MHz wide and the passband filter may have a bandwidth of 2 MHz wide or less.

In addition to a receiver, e.g., a WT receiver operable to receive, pass and measure the first and second signal components, the method may in some embodiments pass the second band instead of the first when the second frequency band is selected. The method further includes controlling the passband filter so as to When switched to the second frequency band, the method includes operating a passband filter to pass third and fourth signal components, the third and fourth frequency components being within the second frequency band; performing a third signal measurement on the third signal component to generate a third signal quality indicator; performing a fourth signal measurement on a fourth signal component to produce a fourth quality indicator; and selecting the operation in the first frequency band and the operation in the second frequency band as a function of the quality indicator values. Then, if the first frequency band is selected, the passband filter may be controlled to pass the first frequency band instead of the second frequency band.

In some embodiments, receiving the first and second signal components and measuring the first and second signal components may be repeated multiple times, and selecting the second frequency band comprises a second quality indicator value It may occur during this predetermined interval, for example after exceeding the first quality indicator value for a predetermined period or for a fixed number of signal measurements. This is done to prevent bands from switching in response to short-term or transient changes in conditions. Another criterion may be used to select between frequency bands, such as, for example, predetermined thresholds. For example, the selecting may include selecting a frequency band corresponding to a low signal quality value when the first and second quality indicator values exceed a predetermined threshold for a predetermined interval. Thus, when indicating that the signal components satisfy the conditions, a lower quality, eg, a lower power band, may be selected without a higher power band to be used by another mobile station. The selecting step may include selecting a frequency corresponding to a high signal quality value when one of the first and second signal quality values is below a predetermined threshold and selecting a good band when the signal quality is an issue. The selecting step is a sign indicating that the first signal quality value decreases with time and the second signal quality value increases with time and indicates that the wireless terminal is facing towards the transmitter of the second signal component and away from the transmitter of the first signal component. and selecting the second frequency band when the difference between the first and second quality values changes.

In some embodiments, the selection step is a function of a quality of service (QoS) to be provided to the user, the selection function changing in response to information indicating a change in the QoS to be provided to the user. This change may be implemented as a change in the threshold used by the selection module to select a frequency band.

In some embodiments, the selecting step is a function of communication system loading, and the method includes receiving information indicative of communication system loading, and modifying the selection function in response to an indicator of a change in communication system loading. including the steps of For example, when the wireless terminal detects the mass use of the first frequency band, the selection step may change the weight used in the selection decision to create a strong preference for the second frequency band. The received loading information is communicated from the base station to the device, eg, the WT receiving the signal.

In various embodiments, multiple alternative carriers may be evaluated before a selection decision is made and a change of carriers is initiated, eg, before a resetting of the controllable filter occurs. For example, in a typical 3 sector/cell system 5 MHz using 3 1.25 MHz carrier bands, the first signal components are signal from the currently connected base station sector transmitter used for downlink traffic signaling to the WT, e.g. beacon signals; Downlink traffic signals, pilot signals, assignment signals, etc., the second signal component being signals received from adjacent sectors/cells transmitters assigned carrier frequencies different from the primary carrier, e.g. It can alternate between different beacon signals. After the second set of signals received from the alternative base station sector transmitter attachment points have been evaluated and the second set of quality indicator values obtained, a comparison with the first quality indicator value is performed, and a decision regarding a change in the selected band is made. This is done.

1 is a diagram of an exemplary wireless communication system supporting multiple carriers implemented in accordance with the present invention and employing methods of the present invention;

2 is a diagram of an exemplary base station implemented in accordance with the present invention and employing methods of the present invention;

3 is a diagram of an exemplary wireless terminal implemented in accordance with the present invention and employing methods of the present invention;

4 is a receiver implemented in accordance with the present invention and employing the methods of the present invention, wherein at the same time it is capable of processing two components of one received signal from the same selected carrier band, each component providing different information, for example two different It is a diagram illustrating a representative embodiment of a receiver that carries information corresponding to one of the carrier bands.

5 is a diagram illustrating exemplary base station signaling associated with an exemplary wireless terminal embodiment using the exemplary embodiment of the single receiver chain receiver of FIG. 4 in accordance with the present invention;

6 is a flowchart illustrating an exemplary communication method for operating a communication system including an exemplary wireless terminal using the exemplary single receiver chain receiver of FIG. 4 in accordance with the present invention.

7 is a partial diagram of an exemplary wireless communication system including an exemplary wireless terminal implemented and operating in accordance with the present invention, and is used for further explanation of the present invention.

8 is a diagram illustrating another exemplary embodiment of a receiver implemented in accordance with the present invention and may be used in the wireless terminal shown in FIG.

FIG. 9 is a diagram illustrating exemplary base station sector transmitter signaling including beacons transmitted in multiple bands according to the present invention corresponding to one sector transmitter and may be transmitted from the exemplary base station shown in FIG. 7 .

FIG. 10 is a diagram illustrating a representative reception signal received by a receiver of a representative wireless terminal shown in FIG. 7 .

11 is a diagram illustrating representative wireless terminal receiver processing of the representative received signal of FIG. 10 and representative band selection according to the present invention.

12 is a representative example including beacons transmitted in multiple bands according to the present invention corresponding to one sector transmitter, which may be transmitted from the representative base station shown in FIG. 7 after the wireless terminal selects a new band and selects a connection device point; It is a diagram illustrating base station sector transmitter signaling.

13 is a diagram illustrating a representative beacon signal having a timing offset with respect to an adjacent sector, used for the purpose of additionally explaining features of the present invention.

1 illustrates an exemplary wireless communication system supporting multiple carriers and spectral signaling implemented in accordance with the present invention. System 100 uses the apparatus and method of the present invention. 1 includes a plurality of representative melt-sector cells, cell 1 102 , cell 2 104 , cell 3 106 . Each cell 102,104,106 provides a radio coverage area for one base station (BS) (BS1 108, BS2 110, BS3 112), respectively. In the exemplary embodiment, each cell 102,104,106 includes three sectors A,B,C. Cell 1 102 includes sector A 114 , sector B 116 , and sector C 118 . Cell 2 104 includes sector A 120 , sector B 122 , and sector C 124 . Cell 2 106 includes sector A 126 , sector B 128 , and sector C 130 . In other embodiments, other numbers of sectors per cell are possible, for example greater than 1 sector per cell, 2 sectors per cell, and 3 sectors per cell. Also, different cells may contain different numbers of sectors.

Wireless Terminals (WTs), e.g. Mobile Nodes (MNs), move throughout the system and communicate via radio links to Base Stations (BSs) to peer nodes e.g. other MNs. can communicate with In sector A 114 of cell 1 102 , WTs 132 and 134 are coupled to BS 1 108 via radio links 133 and 135 respectively. In sector B 116 of cell 1 102 , WTs 136 and 138 are coupled to BS 1 108 via radio links 137 and 139 respectively. In sector C 118 of cell 1 102 , WTs 140 and 142 are coupled to BS 1 108 via radio links 141 and 143 respectively. In sector A 120 of cell 2 104 , WTs 144 and 146 are coupled to BS 2 110 via radio links 145 and 147 respectively. In sector B 122 of cell 2 104 , WTs 148 and 150 are coupled to BS 2 110 via radio links 149 and 151 respectively. In sector C 124 of cell 2 104 , WTs 152 and 154 are coupled to BS 2 110 via radio links 153 and 155 respectively.

BSs may be connected together via a network, thus providing connectivity for WTs within a given cell to peers located outside of that cell. In system 100, BSs 108, 110, and 112 are coupled to network node 168 via network links 170, 172, and 174, respectively. A network node 168, for example a router, is connected to other network nodes (eg, other base stations, routers, home agent nodes, AAA server nodes, etc.) and the Internet via a network link 176 . Network links 170 , 172 , 174 , 176 may be fiber optic links, for example.

BSs 108, 110 and 112 include sector transmitters in accordance with the present invention, each sector transmitter using a specifically assigned carrier for conventional signaling, e.g., downlink traffic signals destined for a particular WT(s). Also, the assigned carrier frequency of the sector transmitter used for normal signaling carries broadcast signals such as assignment signals, pilot signals and/or beacon signals from the BS to the WTs. Further, according to the present invention, each base station sector transmitter transmits additional downlink signals such as pilot signals and/or beacon signals within carrier frequency bands allocated to adjacent cell/sector transmitters for normal signaling. do. Such downlink signals provide information to the WTs, e.g., WT 132, which information will be used to evaluate and decide which carrier frequency to select and which base station sector/cell to use as an attachment point. can The WTs e.g. WT 132 can be used for conventional communications e.g. downlink traffic channel signaling and from BSs 108, 110, 112 providing information on different carrier frequencies that can be selected by the WT. receivers with the ability to process the information of

2 shows an exemplary base station 200 implemented in accordance with the present invention, which is referred to as an access node. The BS is referred to as an access node because it serves as the point of the WT in the network connection device and provides WT access to the network. Base station 200 of FIG. 2 may be a more detailed diagram of any one of base stations 108 , 110 , 112 of system 100 shown in FIG. 1 . The base station 200 includes a processor 202, such as a CPU, coupled together via a bus 214 through which the various components may exchange data and information, a receiver 204 including a decoder 206, and a sector transmitter 208 ), a memory 210 and an I/O interface 212 . The receiver 204 is connected to the sector antenna 216 to receive signals from the wireless terminals 300 (see FIG. 3 ) in each sector covered by the base station 200 . The decoder 206 of the receiver decodes the received uplink signals to extract the information encoded by the WTs 300 prior to transmission. The sector transmitter 208 includes a sector 1 transmitter 218 and a sector N transmitter 220 as a plurality of transmitters. Each sector transmitter 218 and 220 includes encoders 222 and 224 for encoding downlink data/information and is coupled to antennas 226 and 228, respectively. Each antenna 226,228 corresponds to a different sector and is normally oriented and positioned to transmit to the corresponding sector. The antennas 226 and 228 may be separate components or may be different antenna components of a single multi-sector antenna with different antenna components for different sectors. Each sector transmitter 218,220 has one assigned carrier frequency band used for conventional signaling, e.g. downlink traffic signaling. Each sector transmitter 218,220 may transmit downlink signals, eg, assignment signals, data and control signals and/or beacon signals, in its assigned carrier frequency band. In addition, each center transmitter 218,220 transmits additional downlink signals, eg pilot signals and/or beacon signals, to different carrier frequency bands, eg to adjacent cells/sectors for normal signaling in accordance with the present invention. It transmits on the assigned carrier frequency bands. The base station I/O interface 212 connects the base station 200 to other network nodes, such as other access nodes, routers, AAA servers, home agent nodes and the Internet. The memory 210 includes routines 230 and data/information 232 . The processor 202 controls the operation of the base station 200 including the scheduling of users on different carrier frequencies using different power levels, power control, timing control, communication, signaling and beacon signaling in accordance with the present invention. Execute routines 230 in the memory 210 and use data/information 232 to control. Scheduling of a particular user, e.g., a particular WT 300, on a particular carrier frequency may be responsive to selections made by the WT 300 in accordance with the present invention.

The data/information 232 of the memory 210 includes, for example, data 234 that is user data transmitted to and received from the wireless terminal 300, carrier frequencies associated with each sector and its sector information 236 including data transmission power levels associated with each carrier frequency within the sector, a plurality of carrier frequency information (carrier 1 information 238 , carrier N information 240 ), beacon information 242 , and the system loading information 243 . The carrier frequency information 238 and 240 includes information defining a bandwidth related to the frequency of the carrier. The beacon information 242 includes, for example, tone information that is information related to beacon signals on specific frequencies and carriers in each sector, and sequence timing related to transmitting the beacon signals. The system loading information 243 includes composite loading information for each of several carrier bands supported by the base station 200 . System loading information 243 may, in some embodiments, be transmitted from base station 200 to WTs 300 which may use that information in the decision process of carrier band selection to establish within the WT receiver.

Further, the data/information 232 in the memory 210 includes a plurality of WT data/information 244 combinations, for each WT a combination of WT 1 data/information 246, WT N data/information (248). WT 1 data/information 246 includes user data of routes to and from the WT, a terminal ID associating the WT to base station 200, a sector ID identifying the sector in which WT 1 is currently located, the WT 1 contains carrier frequency information related to a specific carrier frequency used for typical signaling.

The base station routines 230 include communication routines 250 and base station control routines 252 . The communication routines 250 implement various communication protocols used by the base station 200 . The base station control routines 252 include a scheduler module 254 and signaling routines 256 . The base station control routines 252 control base station operations including receiver 204, transmitters 218 and 220, scheduling, signaling and beacon signaling in accordance with the present invention. The scheduling module 254, for example, a scheduler, is used to schedule an error link resource, for example, a bandwidth in time, to the wireless terminals 300 for uplink and downlink communication. The base station control routines 252 also include signaling routines 256 that control receiver 204, transmitters 218,220, encoders 222,224, conventional signal generation, data and control tone hopping, and signal reception. do. In addition, the beacon routine 258 included in the signal routines 256 uses the beacon information 242 to control the generation and transmission of beacon signals in accordance with the present invention. In some embodiments in accordance with the present invention, beacon signals (eg, relatively narrow high-power signals in terms of frequency) may be transmitted in each sector in each carrier frequency band used by that sector/cell or adjacent sector/cell. can These beacon signals are used by the WTs 300 to compare different available carriers in some embodiments.

Figure 3 shows an exemplary wireless terminal 300, e.g., a mobile node, implemented in accordance with the present invention and using a method in accordance with the present invention. The wireless terminal 300 of FIG. 3 may be a diagram showing any one of the WTs 132,134,136,138,140,142,144,146,148,150,152, 154,156,158,160,162,164,166 of the system 100 shown in FIG. 1 in more detail. The wireless terminal 300 includes a receiver 302, a transmitter 304, a processor 306 such as a CPU, and a memory with which the various components are associated together via a bus 310 through which data and information can be exchanged. (308).

The receiver 302 is coupled to an antenna 312 through which it receives downlink signals from a plurality of base station sector transmitters and corresponding sector antennas 226,228. The receiver 302 includes a single spread spectrum receiver chain 314 and a band select controller 316 . The spread spectrum receiver chain 314 includes an RF module (frequency synchronization circuit) 320 for performing filtering and other operations. The RF module 320 includes a controllable pass band filter 321 for rejecting frequencies outside the selected band while passing frequencies within the selected band, eg, a carrier signal. The receiver chain 314 also includes an additional module 322 together with a digital signal processing module 324 and an energy detection/SNR determination module 334 . The digital signal processing module 324 includes a decoder 326 and a signal quality detection module 328 .

The RF module 320, the receiver chain addition module 322, the digital signal processing module 324 and the energy detection/SNR detection module 334 use the currently selected first band associated with a specific first carrier frequency to obtain a plurality Receive, decode, measure and evaluate various signals communicated by cell/sector base station transmitters of is used for A band selection controller 316 outputs a signal to the RF module 320 and an adjustable filter 321 included therein to select a specific carrier frequency, and the RF module 320 is configured to select a specific carrier frequency within the selected carrier frequency band. Passes received signal components and rejects at least some signals outside the selected carrier frequency band. In addition, the RF module 320 performs additional processing of, for example, mixing signals to a baseband. The output signals passed by the RF module 320 are processed by the receiver chain addition module 322, for example, filtering by a baseband filter, analog-to-digital signal conversion, and additional filtering by a digital filter. . The signals are then output from the additional modules 322 and transmitted to the digital signal processing module 324 and the energy detection/SNR detection module 334 . Some signal components from the first base station cell/sector transmitter, for example corresponding to the currently selected band, are processed by the digital signal processing module 324, while for example the second cell/sector corresponding to a different carrier band. Other signal components from the transmitter are processed by the energy detection/SNR detection module 334 . The digital signal processing module includes a decoder 326 capable of decoding downlink traffic signals destined for a particular WT 300, whereas the energy detection/SNR detection module 334 does not include such decoding capability.

The outputs of the signal quality detection module 328 and the energy detection/SNR detection module 334 of the digital signal processing module 324, for example quality indicator values, are selected according to the present invention. It is input to the module 316 , and the band selection module 316 controls selection of a frequency band set by the RF module (frequency synchronization circuit) 320 .

Transmitter 304 includes encoder 336 and is coupled to transmitter antenna 338 . Blocks of data/information, eg, uplink data/information, may be encoded by encoder 336 and then transmitted to base station 200 via antenna 338 .

The memory 308 includes routines 340 and data/information 342 . The processor 306, for example a CPU, operates the WT 300 to execute the routines 340 and data/information 342 in the memory 308 to implement the methods of the present invention.

Wireless terminal data/information 342 includes user data 344, device/session resource information 346, currently selected carrier information 348, other carrier information 350, cell/sector information 352, carrier frequency information. 354 , detected signal information 356 and carrier selection information 358 .

User data 344 includes data and information files to be transmitted to or received from a peer node in a communication session using the wireless terminal 300 . The user/device/session resource information 346 includes, for example, terminal ID information, base station ID information, sector ID information, selected carrier frequency information, mode information, and identified beacon information. The terminal ID information may be an identifier that is assigned to the WT 300 by the base station 200 to which the WT 300 is connected and that the wireless terminal 300 is identified by the base station 200 . The base station ID information may be, for example, a slope value associated with the base station 200 and used in hopping sequences. The sector ID information includes information identifying the sector ID of the transmitter/receiver of the sectorized base station with which normal signaling is communicated, and may correspond to the sector of the cell in which the wireless terminal 300 is located. The selected carrier frequency information includes, for example, information identifying the carrier to which the RF module is tuned and used by the BS for downlink data signaling, for example traffic channel signals. The mode information identifies whether the wireless terminal is in an on/hold/sleep state.

The currently selected carrier information 348 includes information identifying the selected carrier to which the RF module 320 has been tuned by the band selection controller 316 . The other carrier information 350 includes information identifying another carrier to which the information evaluated by the energy detection/SNR detection module 334 corresponds. Cell/sector ID information 352 may include information used to construct hopping sequences used for processing, transmission, and reception of data, control signals, and beacon signals. The carrier frequency information 354 may include information associating each cell/sector of the base station with a specific carrier frequency or combinations of frequencies, frequency bands, beacon signals, and tones in a communication system. In addition, the carrier frequency information 354 includes quality indicator related information 355 for associating each quality indicator value with a specific carrier frequency, and the specific carrier frequency may be selected by the band selection controller 316 .

The detected signal information 356 includes signal energy information 360 , SNR information 362 , estimated error information 364 , a first quality indicator value 366 , and a second quality indicator value 368 . In addition, the detected signal information 356 includes synchronization information 370 and broadcast signal information 372 .

The detected signal information 356 includes information output from the signal quality detector 328 of the digital signal processing module 324 and the energy detection/SNR detection module 334 in the receiver 302 . Signal quality detection module 328 measures and records signal energy 360, SNR 362 and/or estimated error rate 364 for the signal component from the first transmitter, and the receiver 302 currently When using the established carrier band, a first quality indicator value 366 indicating the quality of a channel, for example, a downlink traffic channel, between the first transmitter and the WT 300 may be determined. Energy detection/SNR detection module 334 determines a second quality indicator value 368 indicating the quality of a channel, e.g., a downlink traffic channel, between the second transmitter and the WT 300 on a different carrier band. To do this, the signal energy 360 and/or the SNR 362 for the signal component from the second transmitter may be measured and recorded.

Synchronization information 370 may include, for example, pilot signal based timing synchronization information used and/or obtained by a receiver during processing of, for example, a CDMA pilot signal in some CDMA embodiments. In some OFDM embodiments, the synchronization information may include symbol timing recovery information. Broadcast information 372 may include, for example, broadcast related information used and/or acquired by a receiver while pilot or beacon signals are being processed.

Carrier selection information 358 includes predetermined threshold information 374 , preselected interval information 376 , rate of change information 378 , quality of service information 380 , and system loading information 382 . The carrier selection information 358 is used by the WT 300 to make a band selection decision when evaluating the detected signal information, for example, comparing the first quality indicator information 366 and the second quality indicator information 368 . It is information such as criteria, limits, etc. used, for example. The predetermined threshold information 374 includes the levels used to compare the quality indicator values 366 and 368 to make a band selection decision. The preselected interval information 374 includes fixed duration intervals and a fixed number of intervals of signal measurement, each of which changes the selection by the band selection controller 316 to the receiver RF module 320 . It may be used to define a predetermined interval in which a consistent condition exists before, for example, the second quality indicator value exceeds the first quality indicator value. The rate of change information 378 indicates that the second signal quality indicator value 368 increases with time while the first signal quality indicator value 366 decreases with time and the difference between the first and second signal quality indicator values. Contains criteria used to identify when a sign changes. Quality of service (QoS) information 380 includes information pertaining to the QoS provided to individual users, band selection as a function of the QoS level to be provided to the user, and changes in selection as a result of changes in QoS levels to be provided to the user. include System loading information 382 includes received information pertaining to system loading communicated by base station 200, which information may be used in a function to control decisions regarding band selection.

WT routines 340 include communication routines 384 and wireless terminal control routines 386 . The wireless terminal communication routine 384 implements various communication protocols used by the wireless terminal 300 . Wireless terminal control routines 386 perform functional control operations of wireless terminal 300 including power control, timing control, signaling control, data processing, I/O, receiver control and carrier band selection functions in accordance with the present invention. do. The WT control routines 386 include signaling routines 388 , a receiver controller module 390 and a carrier band selection module 392 . The signaling routines 388 use the data/information 342 of the memory 308 to control the signaling of the WT 300, eg, uplink and downlink communication signals. The receiver controller module 390 comprises decoding on the received signal, energy detection and/or SNR detection performed on the received signal, and generation of first and second quality indicator values 366,368 in accordance with the present invention. The operation of the receiver 302 is controlled by cooperating with the modules 324 and 334 . The carrier band selection module 392, together with the band selection controller 316, provides carrier selection information ( 358) as well as data/information derived from the received signal including first and second quality indicator values 366,368.

4 is an example of an exemplary wireless terminal receiver 501/antenna 502 combination 500 implemented in accordance with the present invention. The receiver/antenna combination 500 of FIG. 4 may be used as the receiver 302/antenna 312 combination in the WT 300 of FIG. 3 . The receiver 501 shows a representative embodiment of a receiver according to the present invention, and can simultaneously process two components of a received signal included in the same selected carrier band, and each component contains different information, for example, a different transmitter. and/or information corresponding to one of two different carrier bands transmitted by different transmit antennas. The two signal components may correspond to different sectors of a cell and/or different cells.

The receiver 501 of FIG. 4 uses a single RF processing chain including a single RF processing module (frequency synchronization circuit) 502 . The receiver 501 is coupled to an antenna 504 that receives downlink signals from a plurality of sector/cell base station transmitters. The antenna 504 is coupled to the RF processing module 502 . The RF processing module 502 includes a selectable RF filter 506 and mixer circuit 508 . The RF filter 506 may be implemented as a band pass filter and functions as a frequency lock circuit. The RF processing module 502 is tuned to the carrier frequency selected by the band selection controller 510 . The RF filter passes received signal components within a selected carrier band and rejects at least some signal components outside the selected carrier band.

The received passband signal from the antenna 504 is input to an RF filter 506 and processed by a mixer circuit 508 to become a baseband signal. The baseband signal is output from the RF processing module 502 and input to the baseband filter 512 . The filtered signal from the baseband filter 512 is input to the A/D converter module 514 to perform analog-to-digital conversion. The output digital signal is input to a digital filter 516 for additional filtering. Then, some output of the digital filter 516 and a first signal component 517 originally from for example a first base station cell/sector transmitter are input to a digital signal processing module 518 while the digital filter 516 ) and the second signal component 519 originally from the second cell/sector base station transmitter, for example, are output to the energy detection/SNR detection module 536 . The digital signal processing module 518 includes a timing synchronization module 522 , a decoder 523 and a signal quality detector 526 . The digital signal processing module 518 can thus fully decode WT specific information, eg, broadcast information as well as information destined for individual WTs rather than other WTs.

The timing synchronization module 522 is used for timing synchronization of processed received data, for example, received downlink signals. OFDM embodiments as well as CDMA embodiments are contemplated. In CDMA embodiments, the timing synchronization module 522 may be implemented using known de-spreading techniques. In OFDM embodiments, the timing synchronization module 522 may be implemented as a symbol recovery circuit using known techniques. The decoder 523 includes a broadcast module 524 for decoding received broadcast signals, for example, beacon signals, pilot signals, etc., and received downlink data/information, for example, the receiver 501 and a mobile specific module 525 for decoding downlink signals destined for a specific WT 300 to which it belongs.

The signal quality detector 526 includes a signal energy measurement circuit 528 , an SNR circuit 530 and/or an error estimator 532 . The signal quality detector 526 obtains a quality estimate for the channel used for downlink traffic channel signaling from the first base station cell/sector transmitter to the WT 300 . The quality estimate may be an output of the signal energy measurement circuit 528 (eg the quality estimate may be energy measured in a signal component such as a beacon tone or may be based on the energy of the signal or signal component), the measured Based on the measured or estimated error rate of the received data/information determined by the output of the SNR circuit 530 and/or the error estimator 532 as a function of the signal energy. The signal quality estimation information 533 , for example, a quality indicator value corresponding to the currently selected carrier band, is transmitted to the band selection controller 510 used to make a band selection decision.

In the implementation of FIG. 4 , the second signal component processing is performed by separate sets of receiver components, for example an optional timing synchronization module, an optional broadcast decoder 534 and an energy determination/SNR determination module 536 . is shown as However, the components of the digital signal processing module 518 may be used on a time sharing basis in which the first and second signal components are of the same type, for example OFDM signals. If the second signal component is a beacon signal or other signal for which timing synchronization and/or decoding is not required to generate a quality indicator value, the timing synchronization module 520 and the broadcast signal decoder 534 may be omitted. However, if the first signal component corresponds to a signal of a first type (eg OFDM signal) and the second signal component corresponds to a second type of signal (eg CDMA signal), the first and second signals Separate signals and/or modules for generating signal quality values for the components may be more cost effective than using circuitry, eg, a reconfigurable circuit that may be configured to process different types of signals.

In some embodiments, for example CDMA embodiments, the second signal component 519 is processed via a timing synchronization module 520 . In a CDMA embodiment, the timing synchronization module 520 may be implemented using known de-spreading techniques. Also, in some embodiments, for example various CDMA embodiments, the second signal component 519 is processed via a broadcast signal decoder 534 .

The second signal component, which may have been subjected to the selective processing described above, is input to the energy detection and/or SNR detection module 536 . The processed received signal component evaluated by the energy detection and/or SNR detection module 536 may be for example for the first cell/sector base station transmitter transmitting the first signal component in some OFDM embodiments. It may be a detection beacon signal transmitted from a second transmitter, for example a neighboring cell/sector base station transmitter. Accordingly, in some embodiments, the quality estimation information 537 is a value indicating energy detected in a beacon signal (eg, a beacon tone) or is based on the energy of the beacon signal. The processed received signal component evaluated by the energy detection and/or SNR detection module 536 is, in some CDMA embodiments, a second transmitter, e.g., a first cell/sector base station transmitter transmitting the first signal component. For example, it may be a detection pilot signal transmitted from an adjacent cell/sector base station transmitter. The energy detection and/or SNR detection module 536 may be used as a quality estimate for a potential downlink channel between the WT 300 and a second cell/sector base station transmitter corresponding to the second signal component being evaluated. In signal quality estimation information 537 is generated. The generated quality estimate is based on either a signal energy measurement or an SNT measurement as a function of the detected signal energy. Signal quality estimation information 537 is passed to a band selection controller 510 for use in making a band selection decision to select between first and second frequency bands corresponding to the first and second components, respectively.

In various embodiments, the energy detection and/or SNR detection module 536 is simpler in computational complexity compared to the digital signal processing module 518, for example in the number of gates or in executable instructions. This is possible because in many cases it is not necessary to decode the received signal component to generate the quality estimate information corresponding to the second signal component, where decoding is used compared to the case of mobile specific data. The decoding of broadcast data, which is generally easier to decode than mobile-specific data due to the type of coding, and/or the broadcast signal is intended to reach a plurality of mobile devices, so the power transfer level of the broadcast data is usually higher than that of the mobile-specific data. This is possible because it can be limited to the power transfer level.

The signal component quality information 533 and 537 transmitted from the digital signal processing module 518 and the energy detection and/or SNR detection module 536, respectively, are used by the RF processing module 502 to determine the setting of a carrier frequency band. is used by the band selection controller 502 to

In some embodiments, receiver 501 shown in FIG. 4 is a spread spectrum receiver that processes spread spectrum signals, eg, CDMA and/or OFDM. In some OFDM embodiments, the optional timing synchronization module 520 corresponding to the second component is not used. In some OFDM embodiments, the broadcast signal decoder 534 may be used, whereas in other OFDM embodiments, the broadcast signal decoder 534 is not needed and is omitted. In embodiments in which the second signal component is a CDMA signal, the timing synchronization module 520 is used, but the broadcast signal decoder 534 may or may not be used.

The receiver 501 of FIG. 4 includes a digital signal processing module 518, the energy detection/SNR detection module 536 and the band selection controller via a bus 509 through which various components may exchange data and information. I/O interface 507 coupled to 510 . In other embodiments, bus 509 may be coupled to other receiver components, such as broadcast signal decoder 534 and/or timing synchronization decoder 534 . The receiver 501 may communicate with other components of the WT 300 via an I/O interface 507 that connects the receiver 501 to a bus 312 . The decoded downlink traffic signals may be communicated via interface 507 to one or more external devices, such as, for example, a display and/or other WT components.

FIG. 5 is a diagram 600 used to illustrate an exemplary embodiment of the present invention using the single RF processing module receiver 500 of FIG. 4 . The two transmitters 602, 604 from adjacent sectors A and B of the cell transmit downlink signals including, for example, normal traffic channel signals, such as user data, optionally pilot signals and beacon signals. Transmitters 602 and 604 may use different antennas oriented to other sectors or cells. Signaling from each sector transmitter includes conventional signaling, eg allocation signals in its designated carrier frequency band, and optionally pilot signals and/or optionally beacon signals, and one used within one cell. The above example includes beacon signals in two different carrier frequency bands. The BS sector A transmitter 602 may transmit downlink signals 606 including, for example, sector A downlink traffic signals and sector A assignment signals, optionally sector A pilot signals and/or optionally sector A beacon signals. ) to the carrier frequency f<sb>0</sb>transmit in frequency band 618 with 624, sector A beacon signals 608 at carrier frequency f<sb>1</sb>transmit in frequency band 620 with 626, sector A beacon signals 610 at the carrier frequency f<sb>2</sb>Transmit in frequency band 622 with (628). The BS sector B transmitter 604 may provide downlink signals 612 including, for example, sector B downlink traffic signals and sector B assignment signals, optionally sector B pilot signals and/or optionally sector B beacon signals. ) to the carrier frequency f<sb>2</sb>Transmit in frequency band 622 with (628). In addition, the BS sector B transmitter 604 transmits sector B beacon signals to the carrier frequency f<sb>0</sb>transmit in frequency band 618 with 624, sector B signals 616 at the carrier frequency f<sb>1</sb>Transmit in frequency band 620 with (626).

A representative embodiment of a receiver 630, e.g., receiver 500 of FIG. 4, has a carrier frequency f<sb>0</sb>Assume that it is tuned to a carrier frequency band 618 with (624). The receiver 630 receives two signal components 632 , 634 , a first comprising, for example, conventional signaling, assignment signals, pilot signals and/or beacon signals from a sector A transmitter 602 . A signal component 632 is processed by the digital signal processing module 518, while a second signal component 634 comprising, for example, a beacon signal from the sector B transmitter 604 is the energy detection/SNR detection Processed by module 536 . Receiver 630 has a carrier frequency f<sb>0</sb>Quality prediction for the downlink traffic channel between receiver 630 in BS sector A transmitter using frequency band 618 and 623, from first component 632 and using digital signal processing module 518 to decide Receiver 630 has a carrier frequency f<sb>2</sb>Quality prediction for the downlink traffic channel between receiver 630 at BS sector B transmitter 604 using frequency band 622 and frequency band 622, from second component 634 and with energy detection/SNR detection module (536) is used to determine.

Beacon signals may not be used in some embodiments of the invention and other downlink signals may be received and processed for band selection decisions. For example, each sector and/or cell transmitter may transmit some downlink signals in the frequency band used by that transmitter for normal downlink traffic channel signaling, eg allocation signals, sector/cell base station identification signals and /or transmit pilot signals and also some additional downlink signals in other frequency bands used by other eg adjacent sector/cell transmitters for normal downlink traffic signal, eg sector/cell base station transmit identification signals and/or pilot signals. Transmissions to other frequency bands may occur at periodic intervals and may continuously correspond to a small amount of time proportional to the time the transmitter transmits signals to the corresponding sector.

In accordance with the present invention, a receiver such as the single RF chain receiver 500 of FIG. 4 is tuned to one frequency band, but receives downlink signal components from multiple cell and/or sector transmitters transmitting in that frequency band. The receiver receives and processes a composite signal, wherein the composite signal is within a tuned frequency band and includes first and second components from two different transmitters. Information can be generated from the first and second signal components that can be used and used to ascertain quality indication information about two different frequency bands, each corresponding to a different signal component.

One particular exemplary Orthogonal Frequency Division Multiplexed (OFDM) embodiment is implemented as a relatively high power signal transmitted as a narrow signal in terms of frequency using, for example, a single or a few tones. When a beacon signal is transmitted in the exemplary OFDM embodiment, most of the transmit power is concentrated on one or a few tones constituting the beacon signal. In some embodiments, the first signal component 632 includes one beacon signal component corresponding to the first transmitter, while the second signal component is one corresponding to another transmitter normally corresponding to a different section and/or cell. of beacon signals. In one such embodiment, carrier selection is made based on evaluation of beacon signals. In some embodiments, the beacon signals have a narrow frequency width compared to the band of the bandpass filter. For example, it is as narrow as about 1/20 of the frequency width of the band-pass filter.

According to the invention the first and second signal components can be transmitted simultaneously on different frequencies, for example within the currently selected band. Alternatively, the first and second signal components may be sequentially transmitted and received. 6 is a flowchart 700 illustrating an exemplary method of operating a communication system in accordance with the present invention. 6 is a combination of FIGS. 6A and 6B. Operation begins at step 702, where the communication system is initialized, e.g. base stations are reinitialized and mobile nodes are powered on. Operation proceeds from step 702 to step 704 .

In step 704, the first base station transmitter preferentially transmitting in the first frequency band is operated to transmit the first signal component in the first frequency band. Operation proceeds from step 704 to step 706 . In step 706, the second base station transmitter preferentially transmitting in the second frequency band is operated to transmit, for example, periodically, the second signal component in the first frequency band. In step 708, the first base station transmitter is operated to transmit, for example periodically, a signal in the second frequency band different from the first frequency band. Although in some embodiments the second frequency band is completely outside the first frequency band, in other embodiments the first and second frequency bands may partially overlap. In some embodiments the first transmitter and the second transmitter are located in different sectors of the same cell, and the first signal component is transmitted using a first antenna or antenna element corresponding to the first sector of the same cell. and a second signal component is transmitted using a second antenna or antenna element corresponding to the second sector of the same cell. In some embodiments, the first transmitter and the second transmitter are located in different cells. In such an embodiment a first signal component is transmitted using a first antenna or antenna component corresponding to a first cell and a second signal component is transmitted using a second antenna or antenna component corresponding to a second cell. . Operation proceeds from step 708 to step 710 .

In step 710 the receiver of the mobile node is operated to receive a signal comprising a first signal component and a second signal component. In some embodiments, the signal is received for one period of time and the first and second signal components are received at different times. In some embodiments the first and second signal components are simultaneously received, for example at different frequencies within the first frequency band.

Then, in step 712, a bandpass filter at the receiver of the mobile node is operated to pass the first and second signal components that are within one selected frequency band. The band pass filter rejects signals outside the first frequency band. In some embodiments, for example, OFDM embodiments in which the first and second signal components are beacon signals, the first and second signal components have a narrow frequency width compared to the width of the bandpass filter, for example, It is about 1/20 of the frequency width of the bandpass filter. In some embodiments where the width of the first and second frequency bands is approximately 1 MHz, the band pass filter has a pass band width of 2 MHz or less.

Operation proceeds from step 712 to step 714 . In step 714, the mobile node is operated to perform a first signal measurement on the first signal component to generate a first signal quality indicator. In step 716, the mobile node is operated to perform a second signal measurement on the second signal component to generate a second signal quality indicator. Operation proceeds from step 716 to step 718 . In step 718, the mobile node is operated to select between operation in a first frequency band and operation in a second frequency band associated with the second frequency component as a function of the first and second quality indicators. Operation proceeds from step 718 to step 720 .

In some embodiments, the receiving 710 , filtering 712 , and measuring steps 714 and 716 are repeated a plurality of times and the selection between the first and second frequency bands in step 718 is pre-selected. It is performed after the second quality indicator exceeds the first quality indicator for a predetermined interval, for example a time interval of a predetermined period or a fixed number of signal measurements. This is done to prevent band switching in response to short periods or instantaneous changes in conditions.

In some embodiments the selection is based on a predetermined threshold. For example, the selection includes selection of a frequency band corresponding to a lower signal quality value when both the first and second signal quality values exceed the predetermined threshold for a predetermined interval. Thus, a lower power band can be selected when all of the signal components indicate a satisfactory condition, excluding a lower quality, for example a higher power band to be used by another mobile.

The selecting may include selecting a frequency band corresponding to a higher quality value when the first and second signal quality values are lower than a predetermined threshold and thus selecting a superior band when signal quality is at issue. have. In addition, the selection is that the first signal quality value decreases with time, the second signal quality value increases with time, and the difference between the first and second quality values is such that the wireless terminal is directed toward the transmitter of the second signal component; and selecting the second frequency band when changing a sign indicating that the first signal component is moving away from the transmitter.

In some embodiments the selection step is expressed as a function of a quality of service (QoS) to be provided to a mobile node, for example a user, wherein the selection function changes in response to information indicative of a change in QoS to be provided to the user. This change may be implemented as a change in the threshold quality used by the selection module to select a frequency band.

In some embodiments, the selecting step is expressed as a function of communication system loading, the method comprising information indicating communication system loading and modifying the selection function in response to an indication of a change in communication system loading, for example from a base station. The mobile node further comprises a receiving mobile node. For example, in the case of detecting heavy use of the first frequency band, the selection may change the weight used for determining the selection so as to generate a stronger preference for the second frequency band.

In step 720, the direction of the operation is determined according to whether the first frequency band or the second frequency band is selected. If the first frequency band is selected, operation proceeds to step 704 via access node A 722 , but if the second frequency band is selected, operation proceeds to step 724 .

In step 724, the bandpass filter is controlled to pass the second band instead of the first band. Operation proceeds from step 724 to step 728 via connecting Node B 726 .

In step 728, the second base station transmitter preferentially transmitting the second frequency band is operated to transmit the third signal component in the second frequency band. In step 730, the first base station transmitter or the third base station transmitter that preferentially transmits the first frequency band is operated to transmit the fourth signal component in the second frequency band. In step 732, the second base station is operated to transmit a signal in the first frequency band. In step 734, the receiver of the mobile node is operated to receive a signal comprising a third signal component and a fourth signal component. Operation proceeds from step 734 to step 736 . In step 736, the band pass filter of the mobile node is operated to pass the third and fourth signal components in the second frequency band. In step 738, the mobile node is operated to perform a third signal measurement on the third signal component to generate a third signal quality indicator. In step 740, the mobile node is operated to perform a fourth signal measurement on the fourth signal component to generate a fourth signal quality indicator. Operation proceeds from step 740 to step 742 .

In step 742, the mobile node is operated to select between operation in a first frequency band and operation in a second frequency band as a function of the third and fourth signal quality indicators. Operation proceeds from step 742 to step 744 .

In step 744, operation proceeds depending on whether the first frequency band or the second frequency band is selected. If the second frequency band is selected, operation proceeds to step 728 via access node C 748 . However, if the first frequency band is selected, operation proceeds from step 744 to step 746, in which the bandpass filter of the mobile node passes the first frequency band instead of the second frequency band. controlled to make Operation proceeds from step 746 to step 704 via access node A 722 .

7-12 are used to illustrate representative signals and band selection by an exemplary wireless terminal receiver in accordance with the present invention.

7 illustrates a portion of an exemplary wireless communication system 800 that supports multiple carriers and spread spectrum OFDM signaling implemented in accordance with the present invention. System 800 may be an exemplary embodiment of the system shown in FIG. 1 . 7 includes a plurality of representative mini-cells, cell 1 802 , cell 2 804 , cell 3 806 . Each cell 802, 804, 806 represents a radio coverage area for a base station (BS) (BS 1 808, BS 2 810, BS 3 812), respectively. BSs 808 , 810 , 812 may be representative embodiments of BS 200 shown in FIG. 2 . The BSs 808,810 and 812 are connected together through a network and connected to other network nodes and the Internet. In the exemplary embodiment, each cell 802, 804, 806 includes three sectors A, B, C. Cell 1 802 includes sector A 814 , sector B 816 , and sector C 818 . Cell 2 804 includes sector A 820 , sector B 822 , and sector C 824 . Cell 3 806 includes sector A 826 , sector B 828 , and sector C 830 . 7 also includes an exemplary WT 801 implemented in accordance with the present invention. WT 801 may be an exemplary embodiment of WT 300 shown in FIG. 3 . The current attachment point of the exemplary WT 801 is the sector 3 818 transmitter of BS 1 808 . The WT 801 is moving towards BS 2 810 as indicated by arrow 803 .

8 is an example of an exemplary wireless terminal receiver 901/antenna 902 combination 900 implemented in accordance with the present invention. The receiver/antenna combination 900 of FIG. 8 may be used as the receiver 302/antenna 312 combination in the WT 300 of FIG. 3 or the WT 801 of FIG. 7 . The receiver 901 represents an exemplary embodiment of a receiver according to the present invention, wherein the receiver can process a plurality of components of a received signal included in the same selected carrier band, each component having different information, for example different It carries information corresponding to different frequency bands transmitted by transmitters and/or other transmit antennas. Figure 8 is well suited to the case where all of the signal components are communicated using the same technology, eg the same modulation type.

The receiver 901 of FIG. 8 uses a single RF processing chain including a single RF processing module (frequency synchronization module) 902 . The receiver 901 is coupled to an antenna 904 that receives downlink signals from a plurality of sector/cell base station transmitters. The antenna 904 is coupled to the RF processing module 902 . The RF processing module 902 includes a controllable RF filter 906 and a mixer circuit 908 . The RF filter 906 may be implemented as a band-pass filter and may function as a frequency synchronization circuit. The RF processing module 902 is tuned to the carrier frequency selected by the band selection controller 910 . The RF filter passes received signal components within the selected carrier band and rejects at least some signal components outside the selected carrier band.

The passband signal received from the antenna 904 is input to the RF filter 906 and processed by a mixer circuit 908 to become a baseband signal. The baseband signal is output from the RF processing module 902 and input to a baseband filter 912 . The filtered output from the baseband filter 912 is input to an A/D converter module 914 where analog-to-digital conversion is performed. The resulting output digital signal is input to a digital filter 916 for further filtering. Then, the output of the digital filter 916 is input to the digital signal processing module 918 . The digital signal processing module 918 includes a timing synchronization module 922 , a decoder, a beacon identification module 927 and a signal quality detector 926 . The digital signal processing module 918 is thus able to fully decode the broadcast as well as WT specific information, eg information intended for individual WTs and not other WTs.

The timing synchronization module 922 is used for timing synchronization of processed received data, for example, received downlink signals. The timing synchronization module 522 may be implemented using a known technique. The decoder 923 includes a broadcast module 924 for decoding received broadcast signals, for example beacon signals, pilot signals, etc., and received downlink data/information, for example, a receiver 901 and a mobile specific module 925 for decoding downlink signals destined for a specific WT 300 (or WT 801 ) to which it belongs.

The beacon identification module 927 identifies a received beacon signal that is processed by a specific base station sector transmitter associated with a specific carrier frequency used for its preferential downlink signaling. Each beacon signal may be, for example, a signal occupying a single OFDM symbol time with all or near-total-sector transmitter energy concentrated on one tone. Because of the characteristics of OFDM beacon signals, the beacon identification module 927 can identify the beacon signal without processing the signals through the timing synchronization module 922 or the decoder module 923 .

The signal quality detector 926 includes a signal energy measurement circuit 928 and an SNR circuit 930 . The signal quality detector 926 generates a quality estimate for another channel based on measurements of the identified beacon signals received from the WT 300 from a plurality of base station cell/sector transmitters. The quality estimate is based on the output of the signal energy measurement circuit 928 and/or the output of the SNR circuit 530 as a function of the measured signal energy. The signal quality estimation information 933 , 935 , 937 is passed to the band selection controller 510 , which is used to make a band selection decision, for example.

The signal component quality information 933, 935, 937 transmitted from the digital signal processing module 918 determines which carrier frequency band to be used by the RF processing module 902, e.g., which band and thus which base station sector transmitter is used. Used by the band selection controller 910 to determine whether it is being used to receive downlink communications.

The receiver 901 of FIG. 8 has an I/O interface 907 connected to the digital signal processing module 918 and the band selection controller 910 via a bus 509 through which various components can exchange data and information. includes In other embodiments, bus 509 may be coupled to other receiver components, such as digital filter 916 . The receiver 901 may communicate with other components of the WT 300 via an I/O interface 907 that couples the receiver 901 to a bus 312 . The decoded downlink traffic signals may be communicated via interface 907 to one or more external devices, such as, for example, a display and/or other WT components.

In FIG. 8 , the output of the band selection controller 910 is used to control the RF processing module 902 . In other embodiments, the band select controller 910 may be coupled to the digital filter 916 and/or a digital signal processing module 918 , and the band select controller 910 may be configured to perform digital filtering 916 and/or It can be used to control the digital signal processing module 918 . In such a case, the RF processing module 902 receives and passes a wide portion of the received signal, for example, a plurality of bands, and the digital filtering 916 and/or the digital signal processing module 918 is the band selection controller. Depending on the control signal or signals received from 910, a portion of the received signal is selected for further processing and filtering, or the remainder of the received signal is discarded.

9 is a diagram 1000 illustrating exemplary transmitter signaling in accordance with the present invention. Assume that an exemplary wireless terminal, e.g., a WT 801, uses a total system bandwidth (BW) 100 of 5 MHz in the exemplary three sector per cell multi-cell wireless communication system 800 shown in FIG. 7 . do. A wireless terminal 801 e.g. a mobile node is currently located in the system 800 and some signals from the BS cell 1 sector C transmitter 1002, some signals from the BS cell 2 sector B transmitter 1004 , and it is assumed that some signals from BS Cell 3 Sector A transmitter 1006 can be received. Assume that WT 801 was previously closest to transmitter 1002 but is now closest to transmitter 1004 .

BS cell 1 sector C transmitter 1002 has a carrier frequency f within 1.25 MHz BW band 1010<sb>0</sb>1008 is used to transmit download link signals 1020 . Signals 1020 include downlink traffic channel signals 1021 for WTs indicated by small rectangles and a beacon signal 1024 indicated by large rectangles. Beacon signals are shown at a larger size than conventional signals to show that they have a much higher transmit energy concentration on a per tone basis than conventional signals. Downlink traffic signals 1022, for example the spread spectrum OFDM signal intended for a particular WT 801, are shaded. In addition, the BS cell 1 sector C transmitter 1002 transmits the downlink signals 1026 to the carrier frequency f<sb>1</sb>1.25 MHz frequency band 1014 with 1012. Downlink signals 1026 include one beacon signal 1028 . In addition, the BS cell 1 sector C transmitter 1002 transmits the downlink signals 1030 to the carrier frequency f<sb>2</sb>1.25 MHz frequency band 1018 with 1016. Downlink signals 1030 include one beacon signal 1032 . In this exemplary embodiment, the beacon signals 1024 , 1028 , 1032 and the normal signaling 1021 are transmitted by the transmitter 1002 at different times. Most of the time the transmitter 1002 transmits the normal downlink signaling 1021 , but in some cases, for example, periodically, the transmitter 1002 will focus all or nearly all of the beacon signal at the location of the typical signaling. Transmits beacon signals 1024, 1028, and 1032 with sector transmit power. A timing sequence may be configured such that the transmitter 1002 cycles through beacon signals 1024, 1028, and 1032, respectively.

The BS cell 2 sector B transmitter 1004 has a carrier frequency f within the 1.25 MHz BW band 1014 .<sb>1</sb>1012 is used to transmit download link signals 1038 . Signals 1038 include downlink traffic channel signals 1040 for WTs indicated by small rectangles and beacon signal 1042 indicated by large rectangles. In addition, the BS cell 2 sector B transmitter 1004 transmits downlink signals 1034 in the frequency band 1010 . Downlink signals 1034 include one beacon signal 1036 . In addition, the BS cell 2 sector B transmitter 1004 transmits downlink signals 1044 in a frequency band 1018 . Downlink signals 1044 include one beacon signal 1046 . In an exemplary embodiment, beacon signals 1036 , 1042 , 1046 and conventional signaling 1040 are transmitted by transmitter 1002 at different times. Most of the time the transmitter 1004 transmits the conventional downlink signaling 1040, but in some cases, for example, periodically, the transmitter 1004 will focus all or nearly all of the beacon signal at the location of the typical signaling. Transmits beacon signals 1036, 1042, and 1046 with sector transmit power. The timing sequence may be configured such that the transmitter 1004 cycles through the beacon signals 1036 , 1042 , 1046 respectively.

BS cell 3 sector A transmitter 1006 has a carrier frequency f within 1.25 MHz BW band 1018<sb>2</sb>1016 is used to transmit download link signals 1056 . Signals 1056 include downlink traffic channel signals 1058 for WTs indicated by small rectangles and a beacon signal 1060 indicated by large rectangles. In addition, the BS cell 3 sector A transmitter 1006 transmits downlink signals 1048 in the frequency band 1010 . Downlink signals 1048 include one beacon signal 1050 . In addition, the BS cell 3 sector A transmitter 1006 transmits downlink signals 1052 in the frequency band 1014 . Downlink signals 1052 include one beacon signal 1054 . In the exemplary embodiment, beacon signals 1050 , 1054 , 1060 and conventional signaling 1058 are transmitted by transmitter 1006 at different times. Most of the time the transmitter 1006 transmits the normal downlink signaling 1058, but in some cases, for example, periodically, the transmitter 1006 will focus all or nearly all of the beacon signal at the location of the normal signaling. Transmits beacon signals 1050, 1054, and 1060 having sector transmit power. A timing sequence may be configured such that the transmitter 1006 cycles through beacon signals 1050, 1054, and 1060, respectively.

In this exemplary embodiment, each of the beacon signals 1024 , 1028 , 1032 , 1036 , 1042 , 1046 , 1050 and 1060 is transmitted at the same transmit power level. In other embodiments, different transmit power levels may be used for different beacon signals if the WTs know the transmit power assigned to each beacon signal or the relationship between the power transmit levels assigned to the different beacon signals.

10 is a diagram 1100 illustrating an exemplary composite signal 1002 and associated frequency information at a receiver antenna of a WT receiver 801 . Signal 1102 includes components 1104 , 1106 , 1108 , 1110 , 1112 , 1114 , 1116 . Components 1104 , 1108 , 1112 , 1116 represent noise signals outside of frequency bands 1010 , 1014 , 1018 .

Signals 1106 have a carrier frequency f<sb>O</sb>Represents a received composite signal copy of signals 1020 , 1034 , 1048 that were transmitted within band 1010 with 1008 , where signals 1106 also contain additional noise. The transmitted beacon signal 1024 and the conventional signaling 1021,1022 have been appropriately reduced in amplitude, for example due to channel gain, resulting in the received signals 1024', 1021', 1024'. The transmitted beacon signal 1036 has been slightly reduced in amplitude due to, for example, channel gain, resulting in the received beacon signal 1036'. The beacon signal 1050 is greatly reduced in amplitude due to, for example, channel gain, resulting in the received beacon signal 1050'. As described with respect to FIG. 9 , the signals 1024', 1022', 1021', 1050', and 1036' of FIG. 10 may be received at different times.

Signals 1110 have a carrier frequency f<sb>1</sb>represents a received composite signal copy of signals 1026 , 1038 , 1052 that were transmitted within band 1014 with 1012 , and signals 1110 also contain additional noise. The transmitted beacon signal 1042 and conventional signaling 1040 have been slightly reduced in amplitude, for example due to channel gain, resulting in received signals 1042', 1040'. The transmitted beacon signal 1028 has been appropriately reduced in amplitude due to, for example, channel gain, resulting in the received beacon signal 1028'. The transmitted beacon signal 1054 has been greatly reduced in amplitude due to, for example, channel gain, resulting in the received beacon signal 1054'.

Signals 1114 have a carrier frequency f<sb>2</sb>represents a received composite signal copy of signals 1030 , 1044 , 1056 that were transmitted within band 1018 with 1016 , and also signals 1114 contain additional noise. The transmitted beacon signal 1060 and conventional signaling 1058 have been greatly reduced in amplitude, for example due to channel gain, resulting in received signals 1060', 1058'. The transmitted beacon signal 1032 has been appropriately reduced in amplitude due to, for example, channel gain, resulting in the received beacon signal 1032'. The transmitted beacon signal 1046 has a slight decrease in amplitude, for example due to channel gain, resulting in the received beacon signal 1046'.

11 is a diagram 1200 illustrating exemplary processing by receiver 900 of FIG. 8 for the exemplary composite received signal 1102 of FIG. 10 in accordance with the present invention. WT 801, including receiver 900, is currently connected to BS 1 sector 3 using transmitter 1002 for downlink traffic signaling, so RF processing module 902 determines carrier frequency f<sb>0</sb>Controlled by signal 1202 from band controller 910 to select band 1010 with 1008. The RF processing module 902 extracts the baseband signal 1106 from the signal 1102 and extracts a filtered representation of the information contained in the signal 1106 . Signals 1106' are conventional signaling 1021" corresponding to signals 1021', 1022', 1024', 1036', and 1050', respectively, conventional signaling intended specifically for WT 801. 1022" and beacon signals 1024", 1036", 1050".

Arrow 1206 represents further processing by receiver chain components 912, 914, 916, such as baseband filtering, A/D conversion and digital filtering. Then, the signals are input to the digital signal processing module 918 . The beacon identification module 927 identifies the beacon signal as being associated with the cell 1 sector C transmitter 1002 using the carrier frequency f0 1008, and sets the band 1010 as a band allocated for downlink traffic channel communication. identify The beacon identification module 927 determines the carrier frequency f<sb>1</sb>Identifies beacon signal 1036" as associated with cell 2 sector B transmitter 1004 using 1012, and identifies band 1014 as allocated for downlink traffic channel communications. Beacon identification module ( 927 identifies beacon signal 1050" as associated with cell 3 sector A transmitter 1006 using carrier frequency f2 1016, and identifies band 1018 as allocated for downlink traffic channel communications. do.

The identified beacon information and beacon signals 1024", 1036", 1050" are passed to a signal quality detector 926, where energy content and/or SNR information is obtained and beacon signals 1024 Quality estimation information 933,935,937 corresponding to ",1036",1050") is generated. In this OFDM embodiment, beacon information, beacon signal measurement, and signal quality information generation are performed without using a timing synchronization module or without the need to decode modulation information from a beacon signal. In other embodiments, the beacon signals may be modulated and a broadcast decoding module may be used. Further, in other embodiments, additional information may be taken into account in generating a quality estimate. The error rate for information decoded from, e.g., received conventional signals 1022", e.g., downlink traffic channel signals intended for a particular WT 801, may be It may be considered when evaluating the quality of the channel. Also, the ratio between the beacon signals may be used to determine the interference level if different detected beacon signals may correspond to the same carrier, for example from different cells.

Quality estimation information 1 933 is based on the energy and/or SNR estimation of the processed beacon signals 1024", and the carrier frequency f<sb>0</sb>corresponds to the transmitter 1002 using Quality estimation information 2 935 is based on the energy and/or SNR estimation of the processed beacon signals 1036", and the carrier frequency f<sb>1</sb>corresponds to the transmitter 1004 using Quality estimation information 3 937 is based on the energy and/or SNR estimation of the processed beacon signals 1050", and the carrier frequency f<sb>2</sb>corresponds to the transmitter 1006 using

The band select controller receives the information 933,935,937 and determines that the quality of channel 2 is better than the quality of channel 1 and the quality of channel 1 is better than that of channel 3 and the WT 801 should change its attachment point. At an appropriate time, for example, to minimize service disruption, the band selection controller 910 sends a signal 1202' to the RF processing module 902 at the frequency f<sb>1</sb>to change the selection of

12 is a diagram 1300 illustrating exemplary transmitter signaling after WT 801 changes band selection and connection point. WT 801 sends some signals from BS Cell 1 Sector C transmitter 1002 , some signals from BS Cell 2 Sector B transmitter 1004 , and some signals from BS Cell 3 Sector A transmitter 1006 . can receive Assume that WT 801 was previously closest to transmitter 1002 but is now closest to transmitter 1004 .

BS Cell 1 Sector C Transmitter 1002 has a carrier frequency f within band 1010<sb>0</sb>1008 is used to transmit download link signals 1320 . Signals 1320 include downlink traffic channel signals 1321 for WTs indicated by small rectangles and a beacon signal 1324 indicated by large rectangles. In addition, the BS cell 1 sector C transmitter 1002 transmits the downlink signals 1326 to the carrier frequency f<sb>1</sb>Transmit in frequency band 1014 with (1012). Downlink signals 1326 include one beacon signal 1028 . In addition, the BS cell 1 sector C transmitter 1002 transmits the downlink signals 1330 to the carrier frequency f<sb>2</sb>Transmit in frequency band 1018 with (1016). Downlink signals 1330 include one beacon signal 1032 .

The BS cell 2 sector B transmitter 1004 has a carrier frequency f within band 1014 .<sb>1</sb>1012 is used to transmit download link signals 1338 . Signals 1338 include downlink traffic channel signals 1340 for WTs indicated by small rectangles and beacon signal 1042 indicated by large rectangles. In addition, the BS cell 2 sector B transmitter 1004 transmits downlink signals 1334 in the frequency band 1010 . Downlink signals 1334 include one beacon signal 1036 . The BS cell 2 sector B transmitter 1004 also transmits downlink signals 1344 in the frequency band 1018 . Downlink signals 1344 include one beacon signal 1046 .

BS Cell 3 Sector A transmitter 1006 has a carrier frequency f within band 1018<sb>2</sb>1016 is used to transmit download link signals 1356 . Signals 1356 include downlink traffic channel signals 1358 for WTs indicated by small rectangles and beacon signal 1060 indicated by large rectangles. In addition, the BS cell 3 sector A transmitter 1006 transmits downlink signals 1348 in the frequency band 1010 . Downlink signals 1048 include one beacon signal 1050 . The BS cell 3 sector A transmitter 1006 also transmits downlink signals 1352 in the frequency band 1014 . Downlink signals 1352 include one beacon signal 1054 .

FIG. 13 is a diagram 1400 of an exemplary beacon signal 1420 having a timing offset with respect to an adjacent sector, shown to illustrate additional features of the present invention. 13 includes an exemplary WT 1402 implemented in accordance with the present invention. It is assumed that the exemplary system is an OFDM spread spectrum frequency hopped system using beacon signaling in accordance with the present invention. Time line 1404 represents the time at WT receiver 1402, WT 1402 is currently coupled to a BS1 sector C transmitter, its carrier frequency band is currently being used for downlink traffic channel signaling, and WT ( 1402) has synchronized OFDM symbol timing for the BS 1 sector C transmitter. Three consecutive OFDM symbol time intervals 1406, 1408 and 1410 are shown for BS 1 sector C transmitter communication. Likewise, three consecutive OFDM symbol time intervals 1412, 1414, and 1416 are shown for BS 2 sector B transmitter communication. Each OFDM symbol time interval 1406, 1008, 1410, 1412, 1414, 1416 is approximately the same duration. However, there is a 10% offset 1418 between the start of the BS 1 sector C OFDM symbol time interval and the start of the BS 2 sector B OFDM symbol time interval. This timing offset may be due to, for example, differences between base station timing generators, such as different precise start times, and/or differences due to different distances between the WT 1402 and each base station transmitter.

The BS cell 2 sector B OFDM beacon signal 1420 communicated with the WT 1402 as indicated by arrow 1422 . During time interval 1414 BS cell 2 sector B OFDM beacon signal 1420 is present at WT receiver 1402 . However, since the WT is connected and synchronized to the BS 1 sector C transmitter, WT 1402 detects 90% of the energy for beacon signal 1420 and misses the last 10% of the signal. However, this relatively high energy detection and relatively small amount of associated uncertainty is in many cases satisfactory to support comparison of beacon signals from adjacent cells and/or sectors. Many OFDM embodiments in accordance with the present invention do not require the receiver to resynchronize with respect to the timing for each beacon signal being processed.

Although primarily described in the context of OFDM systems, the methods and apparatus of the present invention are applicable to a wide range of communication systems, including many non-OFDM and/or non-cellular systems.

In various embodiments, the nodes described herein perform steps corresponding to one or more methods of the present invention, for example, carrier band selection, digital signal processing, energy detection/SNR detection, decoding, timing synchronization, signal It is implemented using one or more modules that perform quality detection and the like. In some embodiments, various features of the invention are implemented using modules. Such modules are implemented using software, hardware, or a combination thereof. Many of the above methods or method steps may be used to implement all or part of the above method, i.e. one or more nodes, as a machine, i.e. a general purpose computer with or without additional hardware. It can be implemented using instructions that can be executed by the machine, such as software included in a machine-readable medium such as a memory device for controlling the , that is, RAM, floppy disk, and the like. Accordingly, the present invention above all relates to a machine readable medium comprising instructions executable by the machine to cause a machine, ie a processor and associated hardware, to perform one or more of the method steps described above.

It will be apparent to those skilled in the art in view of the foregoing aspects of the invention that many additional modifications to the various methods and apparatus of the invention described above will occur. Such modifications are within the scope of the present invention. The methods and apparatus of the present invention, in various embodiments, are used in various forms of CDMA, OFDM and/or communication technologies that may be used to provide a wireless communication link between an access node and a mobile node. In some embodiments, the access node is implemented as a base station that establishes a communication link with the mobile node using OFDM and/or CDMA. In various embodiments, the mobile node may be implemented as a notebook computer, PDA or other portable device comprising receiver/transmitter circuitry and logic and/or routines to implement the methods of the present invention.