Timing advance enhancements for cellular communications

Advance timing enhancement for cellular communication

This application is related to files with file numbers 2558.054EP1 (37466-FR-EPA), 2558.055EP1 (37738-FR-EPA), 2558.053EP1 (37760-FR-EPA), 2558.057EP1 (37760-1-FR-EPA), The patent application of 2558.058 EP1 (37760-2-FR-EPA) and the full texts thereof are incorporated into this application by reference, and all of these applications are filed at the same time as this application.

A cellular wireless communication system (such as a cellular wireless communication system defined by General Packet Radio Service (GPRS) and its successors) connects to a base station (BS) of a service provider's core network (its etc.) Communication (relayed to or from the MS via a wireless link) provides communication to a mobile system (MS) (for example, a phone, a computer, or other portable devices) via the core network or network backbone. The geographic area over which a particular BS can perform wireless communication (that is, via the air interface) is composed of one or more radio coverage areas called cells. In order to perform a data transmission, an MS connects to a network in the serving cell that is hosted by a specific BS within the range of a serving cell . When a handover procedure is used to guarantee conditions (for example, a location changes as the MS moves from one cell to another), the connection can be moved to other cells served by the same BS or by a different BS.

A BS can provide uplink channels and/or downlink channels for multiple MSs through time division multiplexing and frequency division multiplexing. In a GPRS system, for example, the BS can periodically broadcast via one or more channels (which divide time into discrete segments called frames and contain time slots for data transmission between BS and MS) A bundle of control data on a defined broadcast control channel (BCCH). The time slot of each frame on each defined channel constitutes a physical channel, and data transmission between an MS and a BS occurs through these physical channels. The logical channel defined by the type of information carried by the channel can be further defined as corresponding to a specific physical channel and used to carry traffic (ie, voice or packet data) and control data in the uplink and downlink directions. The MS monitors the control signals broadcast by the BS and maintains synchronization with the control signals to receive and transmit data via a specific logical channel.

In order for an MS to initiate access to the network (initiate a data transmission or respond to a paging sent from a BS via a paging channel), it is possible to define a specific channel for this purpose (called in GPRS) To obtain media access by transmitting an access request message to the BS on a random access channel (RACH). If the access request message is successfully received, the BS responds via an access grant channel and assigns downlink and/or uplink channels for transmitting data between the BS and the MS. The assigned downlink or uplink channel constitutes a virtual connection between the BS and the MS (referred to as a temporary block flow (TBF)), and the virtual connection lasts for data transmission in the cell where the MS is to be connected duration.

Although the MS can maintain synchronization with the downlink frame received from the BS, the synchronization of the uplink frame transmitted by the MS with the BS requires that the propagation delay be taken into account. Therefore, the MS can use a designated timing offset (called timing advance (TA)) to transmit its data. The designated timing offset corresponds to the time it takes for a signal to reach the BS. At the MS, TA is basically a negative offset between the start of a received downlink frame and the start of a transmitted uplink frame. The BS can free the MS to use a predetermined TA (for example, corresponding to a TA value of 0 or some other predetermined TA value without timing advance) to determine the appropriate TA and transmit this information to the MS.

In the GPRS/EDGE system, RACH is a logical channel (which is a bidirectional common control channel (CCCH) uplink part). Access to RACH is based on competition, which means that a device autonomously chooses when to transmit on that channel and there is a possibility of conflict between transmissions from different devices. The contention-based access permission device triggers a request for one of the uplink resources based on a requirement instead of, for example, a scheduled periodic uplink resource that cannot be used. When transmitting data to the BS, the MS can transmit the data in the form of a so-called normal packet (which is almost as long as a time slot). Due to the propagation time from the MS to the BS, an MS that transmits a normal packet must use an appropriate TA value. However, during the initial access phase when transmitting via RACH, the MS does not know the appropriate TA value. Therefore, the current GSM/EDGE procedure requires the MS to use the access cluster instead of the normal cluster on the RACH. The access packet has a protection time interval long enough to replace the unknown propagation delay traveling to the BS and must carry less than a normal packet of information. After the initial access procedure, the network assigns an appropriate TA value to the MS, which can be referred to as the initial timing advance estimation procedure. The network can also use the packet timing advance control channel (PTCCH channel) to update the TA value based on, for example, the timing variation of the training sequence of the access packet sent on the uplink PTCCH. This can also be called continuous Update the program ahead of schedule. Both procedures are additional signaling overhead. If the MS knows the appropriate TA value before the initial access and/or can assume that the TA value has not changed, it can be expected to avoid the overhead.

In the current GPRS/EDGE system, the appropriate TA value of an MS is calculated by the BS and passed to the MS after each initial access via the MS's network in order to consider the possible movement by the MS. It is also possible to update the TA continuously during a TBF by requesting the mobile station to access the cluster for uplink transmission at a specified time and requesting the network to estimate the timing variation of these clusters on the PTCCH or PACCH. However, for MSs that are fixed at a specific location or whose movement is expected to be restricted to a specific area, these current initial timing advance estimation procedures and continuous timing advance update procedures are not effective and may not be needed. The following describes the modifications to the operating behavior of the BS, MS, and/or the network, and these modifications narrow the scope of the TA update procedures for these fixed MSs. The MS can be configured to operate in a mobile mode or in a stationary mode, where the current TA update procedure is followed in the mobile mode and the current TA update procedure is modified in the stationary mode. Although the description refers to a GPRS/EDGE system, these modifications can be incorporated into other similar services as needed.

1. Fixed TA value used for MO transmission in static mode

In the stationary mode, as performed in the mobile mode, the initial timing advance procedure is not performed for each initial access to radio resources in a given cell. In the context of this content, "initial access" means the first transmission associated with the data transmission from the MS to the network in the cell when no other data transmission is performed. For example, one of the transmissions on the RACH used as part of the TBF establishment in response to receiving data from the higher protocol layer used for transmission is an initial access. An initial access can also occur during contention-based data transmission in which no TBF is established. The fact is that in the static mode, the MS stores the TA value received during an earlier access period in one of the cells and uses this TA value for subsequent data transmissions on the cell. In addition to executing the initial timing advance estimation procedure during the initial access period, additional triggers for executing this procedure can also be defined, such as device reset and power cycling or receiving a trigger signal via a specific user interface (which is Provided to allow the user to trigger the initial timing advance estimation procedure when needed. If the threshold number of attempts to access resources on a cell (using a stored TA) fails, normal initial TA estimation can also be performed. It should also be noted that the modification to the TA estimation and update procedure described here is not intended to modify the existing procedure for maintaining or obtaining synchronization with the cell (for example, by monitoring the appropriate synchronization channel).

Because the TA is associated with a given cell, it is necessary to perform the normal initial TA estimation procedure (with access to the cluster) after the cell reselection before the data is transmitted (that is, any transmission other than the use of the existing access cluster). RACH, etc.). Due to the possibility of the device moving between the cell reselection time and the data transmission time, TA is estimated only after the device is ready to start data transmission. However, for an MS operating in the static mode, the TA decision can be performed in advance to avoid the extra delay and signalling associated with the TA decision that usually immediately precedes the data transmission. Additionally or alternatively, a periodic TA estimation (e.g., by RACH with access to the cluster) can be performed to update the TA (e.g.) due to changes in channel conditions or radio environment or when the MS moves Without losing synchronization with a given cell. It is also possible to execute a TA estimation procedure only when a data transmission is initiated but the final TA estimation is longer than a specified time interval, so as to avoid accessing RACH just to obtain a new TA value. By making the TA available before the data needs to be transmitted, the knowledge of using the TA when transmitting the data (such as using the normal packet on the RACH to transmit the data or using the modified access) can be incorporated into the system.

2. Fixed TA value used for MT transmission in static mode

In the GMM ready state, the network knows the cell to which the mobile machine is to be connected, and can therefore immediately transmit an assignment message in the cell (it can immediately assign the downlink channel to the MS). Figure 1 shows the old-style situation that is also applied when the MS is operating in mobile mode. In response to the immediate assignment message, the MS transmits and accesses the cluster message on the RACH to obtain a TA value and respond to the assignment. The MS can then request an uplink channel on which the MS can use the normal packet with the acquired TA value for transmission. Figure 2 shows the situation when the MS operates in a static mode with a stored TA value. Because the MS requests an uplink channel using the normal cluster with its stored TA value, it can skip the TA acquisition step using the access cluster. In the GMM standby state, the network only knows the routing area/location area where the device is located, and therefore it must be paged in multiple cells. Figure 3 shows the old-type situation that also corresponds to the MS operating in mobile mode. The MS responds to a paging request by requesting a downlink channel and a valid TA value using the access cluster on the RACH. Figure 4 shows the situation when the MS uses a paging operation in the static mode to receive an immediate assignment of one of the downlink channels and responds with a normal packet using the stored TA value to receive the assignment of an uplink channel. In this case, the paging procedure can be modified to include the data in the paging channel, and the response (which can respond to downlink data and/or request uplink resources) is sent using the stored TAs normal packet . Because the response information sent by the MS cannot be transmitted until the TA is known in the old case, avoiding TA update signaling in these cases can reduce the time for uplink TBF establishment and/or complete the transmission for downlink data TBF time.

In the ready state or the standby state of the action termination transmission, if the network realizes (for example, based on the knowledge that the device only responds to short data transmission operations that are always answered by a peer-to-peer entity), a two-way data transmission is required (for example, by uplink Link and downlink TBF), then one of the immediate assignments as shown in FIG. 5 can be used to assign both the uplink and downlink channels. Furthermore, there is no need for resource requests and subsequent assignments before the uplink data can be transmitted.

Because a non-mobile MS may not have to perform as many cell reselections as a fully mobile MS and the power constraints may be less stringent, one of the MSs in the stationary mode can be configured to perform cell reselection even in the standby state A cell update procedure. This will allow the network to always know which cell the MS is to be connected to, so that the network can use the aforementioned downlink assignment procedure even in the standby state. As a fallback procedure, if the MS does not answer the immediate assignment for any reason, the network can be backed up to a normal paging agency. Alternatively, one of the MSs in the stationary mode can be configured to operate only in the ready state and not in the standby state, in order to perform cell update in the usual manner according to the current GPRS/EDGE specifications.

3. Return from static mode to mobile mode

An MS can be configured to decide to execute the above-mentioned optimized procedure or execute the procedure as currently defined (if it determines that the TA value has changed from its last known value). That is, the MS can be configured to recover from static mode if it determines that its stored TA value may be incorrect (or if it cannot determine that the stored TA value may be correct) and a new TA value is needed. Mobile mode. The technique used to determine the change of the correct TA value can be based on the elapsed time and/or measurement by a sensor indicating the movement of the MS. A rough estimate of whether the correct TA value has changed can be made based on the time of the start of data transmission relative to the time when the stored TA value was last updated or the time when the last successful data transmission occurred to make the stored TA value valid. The strength measurement of the received signal from the neighboring cell can be used as a location "fingerprint", so that if it has not changed (within a certain tolerance), there is a higher possibility: The device has not moved until the correct TA of the device is changed. An example algorithm can be executed by MS as follows:

1. MS successfully establishes TBF (and therefore knows that the timing is ahead)

2. At the end of the TBF, the MS stores the TA plus the ID of the serving cell plus one or more of the following: a) a list of neighboring cells with corresponding signal strength measurements and b) a timestamp

3. When new data is to be transmitted; the MS queries the serving cell ID in its stored list. If it does not exist, the MS uses the normal RACH procedure. If it exists and "time_now-timestamp<threshold" and/or the neighboring cell and signal measurement list is within the threshold of the stored list, the MS uses the stored TA

Another technique for detecting movement by the MS can use an accelerometer to detect whether the device has moved significantly enough to possibly cause the stored TA value to become invalid. For example, the MS can use an accelerometer to determine whether at least a certain movement has occurred, so that if a certain movement is detected, the previous TA value is considered invalid. Alternatively, an accelerometer input can be used to trigger further evaluation (such as based on neighbor cell measurements, GPS, etc.) to determine whether the TA has changed. Alternatively, GPS or other satellite-based navigation can be used to determine the location of the device when the TA is determined and when the subsequent data transmission is to be initiated.

In addition to restoring to the mobile mode to obtain a new TA before a data transmission, the MS can perform this restoration and can perform TA update when convenient. Furthermore, because the MS can perform cell reselection without actual movement, it can store multiple valid items for different serving cells at the same time.

4. Low rate PTCCH

Currently, the PTCCH channel is used for the MS in the packet transmission mode to receive continuous timing advance updates. In the uplink, on a periodic designated frame in the PTCCH (that is, on a designated PTCCH sub-channel), the MS transmits an access packet. In response to this, the network indicates whether TA needs to be increased or decreased. For MS operating in static mode, the network can provide fewer PTCCH sub-channels to appear. The network is not almost certain that MSs in packet transmission mode have not moved between consecutive PTCCH sub-channels as specified by the existing standard. However, it is still allowed to provide TA updates as time changes. One of the MSs in the static mode and the packet idle mode can use a similar (but possibly less frequent) PTCCH sub-channel to allow the MS to validate or modify the stored TA value. This will be beneficial because it can increase the possibility that an effective TA is available, and therefore allow the use of optimized solutions, such as sending data on a RACH-like channel without setting a TBF.

5. Extra concepts

The use of an optimized procedure for the use of a stored TA value by one of the MSs described above can be performed depending on the network license (for example, such as broadcast system information reception or peer-to-peer transmission). An MS can indicate its ability to use these procedures in its ability to signal to the network. For example, the MS can indicate to the network that it can operate in a static mode, and then the network will apply any or all of the above procedures to a device that can utilize a stored TA value. In another example, these MSs can be further classified as "zero mobility" devices (their location is fixed) or as "low mobility" devices (their maximum speed and/or movement range is less than a certain A designated threshold). According to this solution, zero-mobility devices in stationary mode can use more optimized timing advance procedures as described above than low-mobility devices (which can sometimes operate in stationary mode). For example, when the MS transmits its classification to the network, the network can omit the use of the existing continuous timing advance procedure for the MS indicating zero mobility, but apply the procedure or one of the procedures for devices with low mobility The optimized form of low-rate PTCCH.

If the optimized procedure using one of the stored TAs fails so that no valid response occurs within a certain period of time and/or in response to a certain number of attempts, the MS can be configured to return to the non-stationary mode to make the old procedure be utilized. An MS can also autonomously determine that its TA value is no longer valid. In this case, if the network attempts an optimized resource assignment, the MS can respond according to the old paging procedure (that is, using the access cluster on the RACH).

A new reason code can be used in the corresponding request message sent on the RACH to indicate that the corresponding request message is a response to an optimized assignment. After the MS has received a TA in response to the RACH transmission, the MS can then use the assigned resources to continue execution.

In the embodiments described herein, conventional methods (for example, as calculated by the BS) can be used by other procedures (for example, such as using a combination of a cell location database (and thus the calculation from the device to the BS) A combination of location information (for example, GPS), manual configuration or static configuration) of distance) determines a stored TA value. It should also be understood that the stored TA value thus determined may not be as accurate as the TA value obtained by the conventional procedure, but may be a less accurate estimate. That is, the optimized timing advance procedure described in this article should be interpreted as including the following two situations: where the TA value is accurately known (within the accuracy limits of the existing TA representation/signaling) and the stored value The TA value is a less accurate estimate of the actual propagation delay compensation (for example, within a certain degree of error), because even when the TA is not accurately known, many benefits can still occur. For example, if the MS does not have TA information at all, the clusters transmitted by the MS must be very short to ensure that the clusters are installed in a time slot at the BS. However, even with an estimated (but not necessarily accurate) TA value, the length of the cluster can be increased (and therefore more data can be transmitted). In other words, even when the accuracy of the determined TA is insufficient to ensure that a conventional normal packet (when the determined TA is used for transmission) will be received by the BS in a single time slot, the experience described in this article can be applied. Optimized timing advance program. The degree of error allowed in the TA estimation depends on the length of the packet being sent (and vice versa). In some embodiments, the length of the cluster (or equivalently, the maximum allowable TA estimation error) is specified by the network. In some embodiments, the MS adjusts the length of the packet according to one of the possible accuracy of its estimated TA (for example, based on the time since the last known TA is the accurate value (for example, in the conventional knowledge of determining TA) Within the accuracy of the method), based on the distance moved or based on the difference in signal strength measurements of the serving cell and/or neighboring cells).

Exemplary embodiment

FIG. 6 shows the components of an exemplary mobile station 100. A processor 10 is coupled to an associated memory 12 and controls the operation of a wireless transceiver 20 to communicate with the network via an air interface. An exemplary base station 200 contains similar components plus a network subsystem for communicating with the network core 300. The processor and memory can be implemented as a microprocessor-based controller and memory for data and program storage, and can be implemented with dedicated hardware components such as ASICs (for example, finite state machines), or as such One combination. The MS can also be equipped with additional components, such as an accelerometer or GPS unit. As the term used herein, a specific device (such as MS or BS) is used to perform various functions or is configured to perform various functions. One of the descriptions means program code executed by a processor or means for execution Specific configuration of hardware components with specific functions.

The MS may include a processor coupled to a radio transceiver for accessing a base station (BS) via an air interface to communicate with the network, wherein the processor is configured to be from the BS The transmission is received and synchronized with the BS, and is further configured to use a specified timing advance (TA) to transmit the packet to compensate for the propagation delay, where the specified TA value can be zero (ie, no timing advance) or Obtain a value by various methods. In one embodiment, the processor is configured to operate in a static mode. In the static mode, when the packet is autonomously transmitted on a random access channel (RACH) or other control channel (e.g., when When establishing a connection with one of the BSs), these clusters are transmitted using the previously stored TA value.

In another embodiment, the MS processor is configured to: 1) receive from the BS the transmission of a frame containing time slots, which can be defined as being used in the uplink or downlink direction A specific logical channel for transmitting traffic or control information between BS and MS; 2) A normal cluster or an access cluster is used for transmission during the time slot of a specific channel, and the access cluster has a longer Guard time intervals and shorter data fields, and use a specified timing advance (TA) relative to the frame to transmit the packet to compensate for the propagation delay; and 3) operate in a moving mode or a static mode and change it The current operating mode is passed to the BS. In the mobile mode, the MS uses one of the TA values with a zero TA value or other designated TA values on a random access channel (RACH) or other control channel defined by the BS to access the cluster (for example) one The channel request message is transmitted to the BS to initiate access to the network. In the case where the transmission is a channel request message, the MS receives an access grant message with a calculated TA value from the BS and the assignment of one or more logical channels for further communication; storing the calculated The TA value; and using the stored TA value to continue communication via the assigned channel with normal cluster communication. In the static mode, the MS processor initiates access to the network by transmitting (for example) a channel request message to the BS on the RACH or other control channel using a previously stored TA value. In the case where the transmission is a channel request message, the MS receives an access grant message from the BS and the assignment of one or more logical channels for further communication; and uses the stored TA value through the normal cluster The designated channel of the news continues to communicate. The MS processor can also be configured to store multiple TA values for use in different cells.

If the MS processor is in static mode or mobile mode and after receiving an access grant message from the BS, the MS processor can use the assigned logical channel to establish a virtual connection with the BS (referred to as a temporary block stream). (TBF)) To continue uplink or downlink data transmission in a non-contention-based manner. The MS processor can be further configured to transmit data to the BS in a contention-based manner on a RACH or other control channel using the normal cluster with the stored TA if it is in the static mode.

The MS processor can be configured to operate in the static mode in preference to the mobile mode when a calculated TA value has been previously stored; and when the specified number of attempts to access the network in the static mode have failed And/or return to the mobile mode when a specified time interval has elapsed since the TA value was stored or the last successful data transmission occurred to make the stored TA value valid. The MS processor can also be configured to: 1) Periodically initiate an uplink access procedure for the BS on a RACH or other control channel to update its TA value (for example, by sending a specific One of the channel request reasons. The channel request message or any other message that can be used or defined to obtain an updated TA value by initiating a cell update procedure may cause the timing of the update by one of the networks to be advanced. Provide any program) and receive an updated TA value, the cycle in which the uplink access can be started is predefined, configured or controlled by the network; 2) If the currently stored TA is saved After a specified time interval has elapsed since the value, a TA request message is transmitted to the BS on a RACH or other control channel and an updated TA value is received; 3) Access to the next network after reset or power cycle And switch to mobile mode to receive an updated TA value; and/or 4) switch to mobile mode for the next network access after receiving a command from a user interface to receive an updated TA value.

The MS processor can also be configured to take precedence over the movement mode when a calculated TA value has been previously stored, and to operate in the stationary mode and resume movement after detecting an indication of movement relative to the BS. model. After returning to the mobile mode, the MS processor can transmit a TA request message to the BS on a RACH or other control channel, receive an updated TA value, and switch to the static mode. The movement relative to the BS can be detected by: 1) a measurement of the strength of the signal transmitted by a neighboring cell, 2) an accelerometer, and/or 3) a GPS unit. In one embodiment, the MS includes a GPS unit and is configured to determine its location from the GPS unit when storing a TA value and before starting a network access to determine whether a movement has occurred. In another embodiment, the MS includes an accelerometer and a global positioning system (GPS) unit and is configured to determine its position from the GPS unit when storing a TA and determine whether it is instructed to move accelerometer signals and/ Or the measurement of neighboring cell transmission is triggered to determine whether a movement has occurred.

The MS processor can be configured to receive one of the downlink channels immediately assigned from the BS when it is in a static mode and is attached to the BS in a ready state and use a normal packet transmission pair with a stored TA value A request for one of the uplink channels. The MS processor can be configured to receive a paging message with one of the downlink channels immediately assigned from the BS when it is in a static mode and is attached to the BS in a standby state and use the one with the stored TA value A normal packet transmission requests one of the uplink channels. The MS processor can be configured to receive one of the downlink channel and the uplink channel from the BS for immediate assignment while in static mode and attached to the BS. The MS processor can be configured to perform periodic cell update procedures by communicating with the BS in a ready state or a standby state when in a static mode.

In one embodiment, the MS processor is configured to store a TA value received from the BS and the ID of the serving cell in a TA table (which associates the ID with the stored TA value). When transmitting data to the BS, if there is the ID of the serving cell in the TA table, the MS uses the associated TA value to operate in the stationary mode, otherwise it operates in the mobile mode. In another embodiment, the MS processor is configured to store a TA value received from the BS and the ID of the serving cell in a TA table (it associates the ID with the stored TA value and is associated with each success data Send to reset a time stamp associated). If the ID of the serving cell exists in the ID list and a specified maximum time interval has not elapsed since the associated timestamp, the MS processor uses the associated TA value to operate in static mode, otherwise it operates in mobile mode . In another embodiment, the MS processor is configured to store a TA value received from the BS and the ID of the serving cell in a TA table (it associates the ID with the stored TA value and is related to the self-serving cell and neighboring cells). The stored signal measurements received by one or more of the cells are associated with). When transmitting data to the BS, if there is the ID of the serving cell in the TA table and if the current signal measurement from the serving cell and/or neighboring cells and the stored signal measurement (they are associated with the ID) One of the comparisons is within a specified threshold, then the MS processor operates in the static mode using the associated TA value, otherwise it operates in the mobile mode.

The MS processor can be configured to transmit an access packet on the cycle designated frame of a packet timing advance control channel (PTCCH) in a packet transmission mode and receive from the BS in response to whether it needs to be increased or decreased One of the stored TA values indicates that compared to the mobile mode, the transmission and access packet rate on the PTCCH can be reduced for the static mode. The MS processor can be further configured to periodically transmit an access packet on a packet timing advance control channel (PTCCH) cycle designated frame in the static mode and receive from the BS in response to whether or not it needs to be increased. Increase or decrease one of the stored TA values indicates. The MS processor can be further configured to return to the mobile mode when in static mode and attached to the BS in response to an immediate assignment from one of the downlink or uplink channels from the BS (if detected One of the indications that the stored TA value is no longer valid).

It should be understood that the various embodiments described above can also be combined in any manner that is considered advantageous. Furthermore, ordinary technicians will easily know many alternatives, changes and modifications. I want to make other such alternatives, changes and modifications fall within the scope of the attached patent application below.

<p>10. . . processor</p><p>12. . . Memory</p><p>20. . . Wireless transceiver</p><p>30. . . Network subsystem</p><p>100. . . Action Station (MS)</p><p>200. . . Base Station (BS)</p><p>300. . . Network core</p>

Figure 1 illustrates the initiation of transmission by one of the actions in the mobile mode;

Figure 2 illustrates the initiation of transmission by one of the actions in the static mode;

Figure 3 schematically illustrates the termination of transmission in one of the actions in the mobile mode;

Figure 4 graphically illustrates the termination of transmission in one of the actions in the static mode;

Figure 5 graphically illustrates the termination of transmission by one of the actions with immediate assignment of downlink channels and uplink channels in static mode; and

Figure 6 shows the components of an exemplary mobile station.