WO2013020506A1

WO2013020506A1 - Method and device for handling time alignment timer in multi-carrier communication system

Info

Publication number: WO2013020506A1
Application number: PCT/CN2012/079819
Authority: WO
Inventors: 万璐; 陈中明; 黄亚达
Original assignee: 中兴通讯股份有限公司
Priority date: 2011-08-08
Filing date: 2012-08-08
Publication date: 2013-02-14
Also published as: CN102932900A; CN102932900B

Abstract

Provided in the present invention are a method and device for handling a time alignment timer (TAT) in a multi-carrier communication system. The method comprises: under the premise of having multiple groups, a UE maintaining TAT time intervals respectively for each group, where cells using a same TA belong to one group; and the UE maintaining an uplink synchronization state for the cells in the group on the basis of if the TAT corresponding to each group has expired. The present invention solves the problem in the related art, where the TAT is maintained only for a primary cell, thereby causing the incapability of UE of knowing directly the uplink synchronization state of an auxiliary cell group, of a base station-side being incapable of receiving normally uplink signals of these cells as the UE may perform an uplink transmission when the auxiliary cell group is in a desynchronized state. The solution adapts to the requirements of the multi-carrier communication system for multiple TA and for multiple groups.

Description

TECHNICAL FIELD The present invention relates to the field of communications, and in particular to a method and apparatus for processing a time alignment timer in a multi-carrier communication system. BACKGROUND OF THE INVENTION Long Term Evolution Advance (LTE-Advanced) introduces many new technologies to meet the basic needs of IMT-Advanced. One of the most important technologies is carrier.

Due to the current shortage of wireless spectrum resources, IMT-Advanced requires higher peak rate indicators (100 Mbps for high mobility and 1 Gbps for low mobility). The maximum 20 MHz bandwidth of the current LTE standard cannot meet IMT-Advanced. Required, so need to expand to higher bandwidth, such as 40MHz, 60MHz, or even higher. One of the methods to increase the bandwidth and peak rate is to expand the frequency domain. For example, the bandwidth of several 20MHz-based LTE bands is expanded by "carrier aggregation", which is the essence of carrier aggregation technology. Therefore, the LTE-Advanced system also belongs to a multi-carrier system. In the LTE-Advanced system, the carrier that participates in the aggregation is called a component carrier, and the user equipment (User Equipment, UE for short) can transmit and receive with the eNB on multiple component carriers at the same time. The component carrier can use the frequency band already defined by LTE, or it can also use the frequency band specially added for LTE-Advanced. Based on the current situation of tight spectrum resources, it is impossible to always allocate a continuous component carrier in the frequency domain to the operator, so the component carrier may be continuous or discontinuous in the frequency band. The concept of a primary cell and a secondary cell is introduced in the carrier aggregation. The primary cell refers to a cell in which the UE initiates an RRC connection establishment or an RRC connection reestablishment or is designated as a primary cell in the handover process; the secondary cell refers to a frequency point different from the primary cell, and Configured after the UE enters the RRC connected state, it is used to provide additional radio resources. In a carrier aggregation system, a serving cell includes a primary serving cell and a secondary serving cell. After the carrier aggregation technology is introduced, the UE can transmit and receive on multiple serving cells simultaneously in the RRC connection state (RRC_CO NECTED), but for the idle state (RRC_IDLE) UE, like the LTE-like, can only reside on one cell. After the UE successfully accesses the cell, that is, after the UE establishes an RRC connection on the cell, the base station may allocate a new cell to the UE through dedicated RRC signaling according to the service requirement, and after allocating the new cell, the base station and the UE The data is not immediately transmitted and received on the newly added cell, that is, the base station does not send service data to the UE on the newly added cell, and the UE saves the configuration information on the cell, and does not send the base station to the base station. Send service data and wait for further action by the base station. The subsequent base station can activate the cell according to the service requirement, and after the cell is activated, the base station and the UE can perform data transmission and reception on the cell. In the LTE system, in order to implement and maintain uplink synchronization between the user equipment and the base station, the base station sends a timing advance (Timing Advance, abbreviated as TA) to each user equipment according to the transmission delay between the base station and each user equipment. The device advances or delays the timing of the respective uplink transmission according to the timing advance sent by the base station, thereby compensating for the transmission delay of the user terminal to the base station, so that the uplink signals of different user equipments reach the base station within the receiving window of the base station. If the transmission delay between each cell in a cell configured for a certain UE is large and the same TA cannot be used, the concept of multiple TAs needs to be introduced in the carrier aggregation system. Depending on the use of the TA, UEs using the same TA can be placed in the same group, thus introducing the concept of grouping. In the previous carrier aggregation system, all carriers use the same TA, the primary cell serves as the cell that receives the TA control element, and also serves as the cell that maintains the time alignment timer (TAT). However, when the concept of packet and multi-TA is introduced, since there are different packets and different TAs, if the primary cell is still only used as the cell for maintaining the TAT, the requirements of the packet and the multiple TA cannot be satisfied. If the UE is unable to directly receive the uplink synchronization status of the secondary cell, the UE may perform uplink transmission when the secondary cell is in the out-of-synchronization state, causing the base station side to fail to receive the uplink signals of the cells. , causing the loss of uplink data. SUMMARY OF THE INVENTION The present invention provides a method and apparatus for processing a time alignment timer in a multi-carrier communication system to at least solve the above problems. An aspect of the present invention provides a method for processing a time alignment timer in a multi-carrier communication system, including: in a case where a plurality of packets exist, the UE maintains a duration of a respective TAT for each packet, where the same is used. The cells of the time advance TA belong to the same packet; the UE maintains the uplink synchronization state of the cells in the packet according to whether the TAT corresponding to each packet times out. Preferably, the TAT of the packet including the primary cell is started or restarted at a time when the UE receives the time advance command TAC related to the packet of the primary cell. Preferably, the TAT of the packet including only the secondary cell is started or restarted at a time when the UE receives the TA of the packet including only the secondary cell; or the UE receives the packet including only the secondary cell The moment of the TA control element. Preferably, after all the secondary cells in the packet including only the secondary cell are deactivated, if the TAT of the packet including only the secondary cell has not timed out, the TAT is continuously maintained. Preferably, before the TAT timeout of the packet including only the secondary cell, if the secondary cell is activated in the packet including only the secondary cell, the activated secondary cell is still in a synchronized state, the activated The secondary cell does not need to perform an uplink synchronization process. Preferably, in an operation phase of the TAT of the packet including only the secondary cell, after all the secondary cells in the packet including only the secondary cell are deactivated, the UE adopts a method of continuing to send the SRS on the deactivated predetermined secondary cell. Acquiring the TA, the predetermined secondary cell includes one of the following: a secondary cell configured with a duration of the TAT, and any one of the secondary cells. Preferably, after the UE sends the SRS on the predetermined secondary cell in the packet that only includes the secondary cell, the method further includes: after receiving, by the UE, the TA adjustment value of the packet where the secondary cell is sent by the primary cell by the primary cell Restarting the TAT of the packet, where the time adjustment required for the secondary cell is determined by the base station by detecting the SRS. Preferably, the TAT of the packet including the primary cell maintains the original operating state when: the cell in the packet including the primary cell receives the TA control element sent by the base station to the packet containing only the secondary cell In the case where the UE receives the activation or deactivation command of the secondary cell in the packet including the primary cell and executes, at least one cell in the packet including the primary cell is in an active state; and/or In the case where the TAT in the packet containing only the secondary cell times out. Preferably, the timeout processing of the TAT of the packet including the primary cell includes at least one of the following: when the TAT of the packet including the primary cell fails but the TAT of the packet including only the secondary cell does not time out, the packet including only the secondary cell is defaulted. TAT timeout; when the TAT of the packet containing the primary cell is timed out but the TAT of the packet containing only the secondary cell has not timed out, all the secondary cells in the activated state are deactivated according to the indication of the base station. Preferably, the timeout processing of the TAT of the packet including only the secondary cell includes at least one of: stopping the TAT when the TAT of the packet including only the secondary cell expires, if the packet containing only the secondary cell exists The activated secondary cell, according to the indication of the base station, the UE initiates a random access procedure in a certain secondary cell activated in the packet including only the secondary cell to establish uplink synchronization of the packet including only the secondary cell, where the UE After the TA is obtained, the TAT of the packet including only the secondary cell is started; When the TAT of the packet including only the secondary cell times out, stopping the TAT, deactivating all the secondary cells in the packet including only the secondary cell according to the indication of the base station; when the TAT of the packet including only the secondary cell When the timeout expires, the TAT is stopped, and the base station and the UE default that all the secondary cells in the packet including only the secondary cell have been deactivated; when the TAT of the packet including only the secondary cell times out, deleting the secondary only included secondary cell The configuration of all the secondary cells in the packet; when the TAT of the packet containing only the secondary cell times out, clearing the HARQ memory of all the secondary cells in the activated state only the secondary cell, the UE stops at the Sending an SRS on all the secondary cells in the packet including only the secondary cell, releasing or retaining the SRS resources of all the secondary cells in the packet including only the secondary cell; when the TAT distance of the packet including only the secondary cell expires If the predetermined time length is left, if the secondary cell still exists in the packet including the secondary cell, the secondary cell is activated according to the indication of the base station. All the secondary cells in the packet stop the TAT when the TAT of the packet including only the secondary cell times out; and when the TAT distance of the packet including only the secondary cell has a predetermined time remaining, the base station and the UE By default, all the secondary cells in the packet including only the secondary cell have been deactivated, and when the TAT of the packet including only the secondary cell times out, the TAT is stopped; when the TAT distance of the packet containing only the secondary cell expires If the predetermined duration is left, all the secondary cells in the packet including only the secondary cell are deactivated according to the indication of the base station, and the HARQ memory of all the secondary cells in the activated state is cleared. The UE stops transmitting SRS on all the secondary cells in the packet including only the secondary cell, and releases or reserves the SRS resources of all the secondary cells in the packet including only the secondary cell, when the packet includes only the secondary cell When the TAT times out, the TAT is stopped; when the TAT distance of the packet including only the secondary cell has a predetermined time remaining, the base station and the UE default to include only the auxiliary small All the secondary cells in the packet have been deactivated, and the HARQ memory of all the secondary cells in the active state only packet is cleared, and the UE stops on all the secondary cells in the packet containing only the secondary cell. The SRS is sent, and the SRS resources of all the secondary cells in the packet including only the secondary cell are released or reserved, and when the TAT of the packet including only the secondary cell expires, the TAT is stopped. Preferably, before maintaining the duration of the respective time alignment timer TAT for each packet, the method further includes: receiving, by the base station, the duration of the TAT configured for each packet, wherein the durations of the TATs of different packets are the same or different. Preferably, the duration of the TAT is configured in the cell configuration information, and the cell in which the cell configuration information is configured is used as a cell that manages the TAT in the packet. Preferably, cells using the same TA and time reference belong to the same packet. Another aspect of the present invention provides a processing apparatus for a time alignment timer in a multi-carrier communication system, including: a TAT duration maintenance module, configured to maintain a respective TAT for each packet in the presence of multiple packets The duration, where the cells using the same timing advance TA belong to the same group; the uplink synchronization state maintenance module is configured to maintain the uplink synchronization state of the cells in the packet according to whether the TAT corresponding to each packet times out. Preferably, the uplink synchronization state maintenance module and the TAT duration maintenance module are located on the base station side or the UE side. Preferably, the apparatus further includes: a configuration module, located at the base station side, configured to configure a duration of the respective TAT for each packet, wherein the durations of the TATs of different packets are the same or different. Preferably, cells using the same TA and time reference belong to the same packet. According to still another aspect of the present invention, a method for processing a time alignment timer in a multi-carrier communication system includes: in the case where a plurality of packets exist, the user equipment UE maintains a respective time alignment timer TAT for each packet The duration of the time, wherein the cells belonging to the same group meet at least one of the following conditions: use the same timing advance TA, use the same time reference; the UE maintains the packet according to whether the TAT corresponding to each packet times out The uplink synchronization status of the cell. According to still another aspect of the present invention, a processing apparatus for a time alignment timer in a multi-carrier communication system includes: a time alignment timer TAT duration maintenance module, configured to be configured for each packet in the case where a plurality of packets exist Maintaining the duration of the respective TATs, wherein the cells belonging to the same group satisfy at least one of the following conditions: use the same timing advance TA, use the same time reference; the uplink synchronization state maintenance module, set to correspond to the TAT according to each group Whether to time out, maintain the uplink synchronization status in the packet. With the present invention, it is configured to configure and manage the respective TATs for each packet, and solve the related art that the TAT is only maintained in the primary cell, and thus the UE cannot directly know the uplink synchronization status of the secondary cell packet, and the UE may be in the UE. When the secondary cell group is in an out-of-synchronization state, uplink transmission is performed, and the base station side cannot normally receive the cells. The problem of the uplink signal, the scheme adapts to the demand for multiple TAs and multiple packets in the multi-carrier communication system, and can provide more accurate uplink synchronization control for each packet, thereby reducing the error probability of uplink transmission, thereby improving the entire system. Service performance. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, In the drawings: FIG. 1 is a schematic diagram of a processing method of a time alignment timer in a multi-carrier communication system according to an embodiment of the present invention; FIG. 2 is a processing apparatus for a time alignment timer in a multi-carrier communication system according to an embodiment of the present invention; 3 is a schematic diagram of coverage of carrier aggregation according to an embodiment of the present invention; FIG. 4 is a detailed flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to Embodiment 1. FIG. FIG. 6 is a detailed flowchart of a processing method of a time alignment timer in a multi-carrier communication system according to Embodiment 3; FIG. 7 is a detailed flowchart of a processing method of a time alignment timer in the multi-carrier communication system according to Embodiment 3. FIG. FIG. 8 is a detailed flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to Embodiment 5; FIG. A detailed flowchart of a method of processing a time alignment timer in the multi-carrier communication system of Example 6; and FIG. 10 is another embodiment of the present invention A schematic diagram of a method of processing a time alignment timer in a multi-carrier communication system. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. In the previous carrier aggregation system, all carriers use the same TA, the primary cell serves as the cell that receives the TA control element, and also serves as the cell that maintains the time alignment timer. When the concept of packet and multi-TA is introduced, only the primary cell is used. It is not enough to maintain a TAT cell. Different packets need to maintain different TA timers according to the time of receiving TAs in their respective groups. At this point you need to maintain a TAT in each group. In the packet including the primary cell, the primary cell can continue to be used as the cell that maintains the TAT. After the TAT is introduced in a group that includes only multiple secondary cells, it is necessary to consider how the TAT will be maintained, and what operations the UE needs to perform when the TAT times out. 1 is a flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to an embodiment of the present invention. The method includes: Step S102: In case multiple packets exist, the UE maintains a respective TAT for each packet. The duration of the cell in which the same TA is used belongs to the same packet. In step S104, the UE maintains the uplink synchronization state of the cell in the packet according to whether the TAT corresponding to each packet times out. With this method, when there are multiple packets, the UE manages one TAT in each packet, that is, the TBT including the primary cell and the TTP containing only the secondary cell can be separately managed, and the method solves the related art only in the related art. The primary cell maintains the TAT, and the UE cannot directly learn the uplink synchronization status of the secondary cell group. The UE may perform uplink transmission when the secondary cell packet is in an out-of-synchronization state, and the base station side cannot receive the uplink signal of the cell normally. The scheme adapts to the demand for multiple TAs and multiple packets in a multi-carrier communication system, and can provide more accurate uplink synchronization state control for each packet, thereby reducing the error and loss probability of uplink transmission, thereby improving the service of the entire system. performance. As a preferred manner, in step S102, cells using the same TA and time reference belong to the same packet. As a preferred manner, while the UE maintains the duration of the TAT of each packet on the UE side for each packet, the base station may maintain the corresponding duration of the TAT on the base station side for each of the foregoing packets, so that the UE side The TAT is consistent with the processing of the TAT on the base station side. In addition, it is also convenient for the base station to know the TAT operation state of the UE side (although the TAT on the UE side and the TAT on the base station side are two different TATs, but if the same manner is adopted and The same configuration to maintain the two TAT, the results should be nearly identical), in order to In the case where the TAT of the side is partially triggered (in this case, the TAT on the base station side should also have a matching trigger action), the base station performs corresponding processing.

The duration of the TAT may be configured using RRC signaling, and the duration of the TAT corresponding to the packet including only the secondary cell may be different from the duration of the TAT of the packet including the primary cell, or may be configured only in one of the cells in the group. The TAT duration is, for example, the length of the TAT configured in the cell configuration information, and the cell in which the cell configuration information is configured is used as the cell managing the TAT in the packet. The UE may receive the length of the TAT configured by the base station for each packet, and the duration of the TAT of the different packets may be the same or different. In addition, the duration of the TAT may be based on the current cell included in the packet corresponding to the TAT. The configuration or reconfiguration, that is, when the base station performs the addition, deletion, and reconfiguration of a certain cell in the packet, the TAT duration maintained by the UE may be reconfigured according to the latest component cell status in the packet. When all the secondary cells in the packet are deleted, the UE no longer maintains the TAT of the packet. The following describes the maintenance of the TAT of the packet including only the secondary cell and the TAT maintenance procedure of the packet including the primary cell, respectively. For a packet containing only a secondary cell (1) Startup or restart processing: When the UE receives the TA value in the packet, it starts or restarts the TAT in the group. The TAT is started or restarted whenever the cell in the group receives the TA Control Element.

(2) Processing when the cell activation state changes in the packet: After all the cells in the packet including only the secondary cell are deactivated, if the TAT does not time out at this time, the TAT is continued to be maintained until the TAT times out; before the TAT expires, If the secondary cell in the packet is activated, uplink synchronization is not required to be performed, and the activated secondary cell in the packet is considered to be in a synchronized state.

(3) The acquisition of the sounding reference signal (SRS) in the TAT operation phase and the processing of the subsequent base station: After the uplink synchronization is completed only for the packet including the secondary cell, the UE may be in the packet during the operation phase of the TAT. The SRS is transmitted on the secondary cell that is in the active state, or the SRS is also transmitted on the deactivated secondary cell in the running phase of the TAT. After all the secondary cells in the packet are deactivated, the UE may send the SRS in the cell configured with the TAT duration, or may send the SRS in any one of the cells. After the SRS is sent by the UE, the base station detects whether the UE needs to perform time adjustment by detecting the SRS. When the secondary cell needs to perform time adjustment, the base station may send the TA adjustment value of the secondary cell packet to the UE through the primary cell. After receiving the TA adjustment value of the secondary cell group, the UE restarts the TAT of the group.

For a packet containing a primary cell (1) Startup or restart processing: When the UE receives a time advance command (TAC) related to a packet including a primary cell, it starts or restarts the TAT of the packet.

(2) The case of maintaining the original operating state: when the TA control element sent by the base station to the packet including only the secondary cell is received in the packet including the primary cell, the TAT maintains the original state; After the activation or deactivation command of the cell is executed and executed, the TAT maintains the original state as long as one cell in the packet is in an active state; and if the TAT in the packet including only the secondary cell times out, the packet including the primary cell is included. The TAT remains in its original state. The TAT timeout processing of a packet including only the secondary cell and the TAT timeout processing of the packet including the primary cell will be described below. For a packet containing only the secondary cell, TAT timeout processing of the packet including only the secondary cell may be performed by any of the following timeout processing methods:

(1) When the TAT in the packet containing only the secondary cell times out, the TAT is stopped. The base station selects a secondary cell in the packet, instructs the UE to initiate a random access procedure in the secondary cell, obtains uplink synchronization of the packet, and obtains a TA value in the synchronization process to start the TAT. Specifically, if there is an activated secondary cell in a packet including only the secondary cell, the UE initiates a random access procedure in a certain secondary cell activated in a packet including only the secondary cell according to the indication of the base station, and establishes a packet including only the secondary cell. Uplink synchronization, after the UE acquires the TA, it starts the TAT of the packet containing only the secondary cell.

(2) Stop TAT when the TAT in the packet containing only the secondary cell times out. The MAC control element is deactivated according to the secondary cell sent by the base station, and all the secondary cells in the packet are deactivated, that is, explicitly deactivated.

(3) Stop TAT when the TAT in the packet containing only the secondary cell times out. The base station does not send the secondary cell to activate the MAC control element to activate all the secondary cells in the packet. The UE and the base station consider that the secondary cell in the packet has been deactivated, that is, implicitly deactivated.

(4) After the TAT expires, delete the configuration of all cells in the group. (5) when the TAT corresponding to the packet including only the secondary cell times out, clearing the HARQ memory of all the secondary cells in the active state in the group; the UE stops transmitting the SRS on the cell of the secondary cell group, and releases all the assistants in the group. SRS resources configured by the cell. (6) When the TAT corresponding to the packet containing only the secondary cell times out, the HARQ memory of all the secondary cells in the active state in the group is cleared; the UE only stops transmitting the SRS on the cell of the secondary cell group, and still retains the SRS resource.

(7) When the TAT is about to time out, if the secondary cell still exists in the packet containing only the secondary cell, the secondary cell sent by the base station deactivates the MAC control element to activate all the secondary cells in the group. Stop TAT after TAT times out.

(8) When the TAT is about to time out, the base station does not send the secondary cell to activate the MAC control element to activate all the secondary cells in the packet, and the UE and the base station consider that the secondary cell in the packet has been deactivated, that is, implicitly deactivated. . Stop TAT after TAT times out. (9) When the TAT is about to time out, the MAC control element is deactivated according to the secondary cell sent by the base station, all secondary cells in the group are deactivated, and the HARQ memory of all active secondary cells in the packet containing only the secondary cell is cleared. The UE stops transmitting SRS on all the secondary cells in the packet including only the secondary cell, releases or reserves the SRS resources of all the secondary cells in the packet including only the secondary cell, and stops the TAT after the TAT expires.

(10) When the TAT is about to time out, the base station does not send the secondary cell to activate the MAC control element to activate all the secondary cells in the packet. The UE and the base station consider that the secondary cell in the packet has been deactivated, that is, implicitly deactivated. Clearing the HARQ memory of all the secondary cells in the active state in the packet containing only the secondary cell, the UE stops transmitting the SRS on all the secondary cells in the packet including only the secondary cell, and releases or reserves the packet including only the secondary cell. SRS resources of all secondary cells in the middle, stop TAT after TAT times out.

For a packet including a primary cell (1) When a TAT in a group including a primary cell fails but a TAT in a group including only a secondary cell does not time out, it is considered that the TAT in the group including only the secondary cell times out, and the above may be followed. The TAT timeout processing mode of the packet including only the secondary cell is processed, for example, the TAT in the group of the secondary cell is stopped. The UE considers that all secondary cells in the group of the secondary cell are in a deactivated state at this time. Clearing the HARQ memory of all the secondary cells in the active cell in the group of the secondary cell; the UE notifying the upper layer, such as the RRC, to release the SRS resources configured in all the cells in the group of the secondary cell. (2) When the TAT in the group containing the primary cell is to time out but the TAT in the group containing only the secondary cell does not time out, according to the MAC control element sent by the base station, all activation states in the packet including only the secondary cell are deactivated. Secondary cell. After the TAT expires in the packet including the primary cell, it is considered that the TAT in the packet including only the secondary cell expires, and the TAT is stopped. The UE clears the HARQ memory of all the secondary cells in the packet including only the secondary cell; the UE notifies the RRC to release the SRS resources configured for these secondary cells. The configuration, maintenance, and timeout processing of the TAT in the packet including only the secondary cell in the carrier aggregation system of the multiple TA is provided in the above method. Based on this core idea, in the actual application process, the RRC protocol of the UE may be modified, and the configuration parameter is added to configure the TAT of the packet including only the secondary cell; the MAC protocol may also be modified to explicitly include only the secondary cell. The description of the group's TAT startup time, maintenance, and timeout processing. FIG. 10 is a schematic diagram of a method for processing a time alignment timer in a multi-carrier communication system according to another embodiment of the present invention. As shown in FIG. 10, in another embodiment of the present invention, a time alignment timer in a multi-carrier communication system The processing method includes: Step S1002: In the case that there are multiple packets, the UE maintains a duration of the respective TAT for each packet, where the cells belonging to the same group satisfy at least one of the following conditions: use the same timing advance TA, using the same time reference; Step S1004, the UE maintains the uplink synchronization state of the cell in the packet according to whether the TAT corresponding to each packet times out. In the processing method of the time alignment timer in the multi-carrier communication system in this embodiment, cells using the same TA belong to the same packet, or cells using the same time reference belong to the same packet, or use the same TA and time. The referenced cells belong to the same group. With this method, when there are multiple packets, the UE manages one TAT in each packet, that is, the TBT including the primary cell and the TTP containing only the secondary cell can be separately managed, and the method solves the related art only in the related art. The primary cell maintains the TAT, and the UE cannot directly learn the uplink synchronization status of the secondary cell group. The UE may perform uplink transmission when the secondary cell packet is in an out-of-synchronization state, and the base station side cannot receive the uplink signal of the cell normally. The scheme adapts to the demand for multiple TAs and multiple packets in a multi-carrier communication system, and can provide more accurate uplink synchronization state control for each packet, thereby reducing the error and loss probability of uplink transmission, thereby improving the service of the entire system. performance. It should be noted that, in this method, the startup, restart, timeout processing, and other related processing manners of the TAT can be referred to the foregoing method embodiments, and details are not described herein again. 2 is a structural block diagram of a processing apparatus for a time alignment timer in a multi-carrier communication system according to an embodiment of the present invention. The apparatus includes: a TAT duration maintenance module 22, configured to, for each packet, in the presence of multiple packets Maintaining the duration of the respective TATs, wherein the cells using the same TA belong to the same group; the uplink synchronization state maintenance module 24 is configured to maintain the uplink synchronization state of the cells in the packet according to whether the TAT corresponding to each packet times out. The above TAT duration maintenance module 22 and uplink synchronization state maintenance module 24 may be located at the base station side or UE.

As a preferred embodiment, cells using the same TA and time reference belong to the same packet. In addition, the apparatus may further include: a configuration module, located at the base station side, configured to configure a duration of each TAT for each packet, and the durations of the TATs of different packets may be the same or different. 2 is a structural block diagram of a processing apparatus for a time alignment timer in a multi-carrier communication system according to an embodiment of the present invention. As shown in FIG. 2, in another embodiment of the present invention, a time alignment timer in a multi-carrier communication system The processing device includes: a TAT duration maintenance module 22, configured to maintain a duration of the respective TAT for each packet in the case where there are multiple packets, wherein the cells belonging to the same packet satisfy at least one of the following conditions: The time advance TA is the same time reference; the uplink synchronization state maintenance module 24 is configured to maintain the uplink synchronization state of the cell in the packet according to whether the TAT corresponding to each packet times out. In the processing apparatus of the time alignment timer in the multi-carrier communication system in this embodiment, cells using the same TA belong to the same packet, or cells using the same time reference belong to the same packet, or use the same TA and time. The referenced cells belong to the same group. 3 is a schematic diagram of coverage of carrier aggregation in accordance with an embodiment of the present invention. As shown in Figure 3, the serving cell 1

(downstream frequency point fl, uplink frequency point fl '), referred to as CC1 (DL fl , UL fl '); serving cell 2 (downstream frequency point £2, uplink frequency point £2'), referred to as CC2 (DL £2) , UL £2'); Serving cell 3 (downlink frequency β, uplink frequency point β') can perform carrier aggregation. The user equipment UE camps on CC1 and initiates an RRC connection procedure on CC1, CC1 is considered to be the primary serving cell of the UE, and CC1 is in group 1. The serving cells CC2 and CC3 are secondary cells, in group 2. The cell IDs of CC1 to CC3 are 1~3 respectively. The following takes the scenario shown in FIG. 3 as an example. The time alignment of the multi-carrier communication system provided by the embodiment of the present invention is described in detail by using a frequency division duplex mode (FDD) as an example. The processing scheme of the timer, Embodiment 1-6 combines the technical solutions of the above plurality of preferred embodiments. Embodiment 1 FIG. 4 is a detailed flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to Embodiment 1. As shown in FIG. 4, the method includes the following steps: Step 401: A UE initiates an RRC connection on CC1, and the base station The information of CC2 and CC3 and the packet information are configured to the UE in the RRC Connection Reconfiguration message. CC1 is the main serving cell, which is composed of group 1, supplemented by CC2 and CC3. The serving cell, which is group 2; the TAT duration of group 1 is 1280 ms. The base station configures the TAT duration of the group 2 in the RRC connection reconfiguration message to be 750 ms. The base station configures the secondary cell deactivation timer to be infinite. Step 402: The base station sends a secondary cell activation MAC control element, and activates CC2 and CC3. Step 403: The UE initiates a random access procedure on the CC2 to establish uplink synchronization of the group 2. When the TA in the random access response message received by the UE, the TAT of the group 2 is started. After the uplink synchronization of group 2 is completed, the UE may send the SRS on CC2 and CC3 during the TAT operation phase. Step 404: The base station sends a TA control element on the CC of the group 2 to perform time adjustment of the group 2. Step 405: The UE restarts the TAT of the group 2 when receiving the TA control element of the group 2 sent by the base station. Step 406: After the period of time, the TAT of the group 2 times out. At this time, the CC2 and the CC3 are still in the active state, and the CC2 and the CC3 clear the respective HARQ memories, and notify the RRC to release the configured SRS resources. Step 407: The base station instructs the UE to initiate an uplink synchronization process on CC2. Step 408: CC2 re-initiates the random access process and performs uplink synchronization. In the uplink synchronization process, the group 2 receives the TA value carried in the random access response, and the TAT maintained by the group 2 is started; after the uplink synchronization of the group 2 is completed, In the TAT operation phase, the UE may send the SRS on CC2 and CC3. Step 409: After the period of time, the TAT is still in operation, and the base station deletes CC2 in group 2 at this time. The TAT duration of the CC3 is 1280 ms. Therefore, the TAT duration of the group 2 is set to 1280 ms in the RRC connection reconfiguration message of the CC2. Step 410: After receiving the RRC connection reconfiguration message, the UE applies the message content to continue the maintenance. TAT. Embodiment 2 FIG. 5 is a detailed flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to Embodiment 2. As shown in FIG. 5, the method includes the following steps: Step 501: A UE initiates an RRC connection on CC1, and the base station The information of CC2 and CC3 and the packet information are configured to the UE in the RRC Connection Reconfiguration message. CC1 is the primary serving cell, which is group 1, CC2 and CC3 are the secondary serving cells, which constitute group 2; the TAT duration of group 1 is 1280 ms. The base station configures the TAT duration of the group 2 in the RRC connection reconfiguration message to be 750 ms. The base station configures the secondary cell deactivation timer to be infinite. Step 502: The base station sends a secondary cell activation MAC control element, and activates CC2 and CC3. Step 503: The UE initiates a random access procedure on the CC2 to establish uplink synchronization of the group 2. When the TA in the random access response message received by the UE, the TAT of the group 2 is started. After the uplink synchronization of the group 2 is completed, the UE may send the SRS on the CC2 and the CC3 in the TAT operation phase; Step 504: The base station sends the TA control element on the CC of the group 2 to perform the time adjustment of the group 2; Step 505: The UE is in the When receiving the TA control element of the group 2 sent by the base station, restarting the TAT of the group 2; Step 506: After the period of time, when the TAT of the group 2 is 950 ms, the timeout is about to expire, and CC2 and CC3 are still activated. State, the base station sends a secondary cell to activate the MAC Control element to activate CC2 and CC3. Step 507: After the CC2 and P CC3 are deactivated, the HARQ memory of the two cells is cleared, and the UE stops transmitting the SRS signal on the two cells. Group 2 TAT did not stop after CC2 and CC3 deactivation. After a period of time, TAT times out and stops TAT. At this time, CC2 and CC3 are not activated again, and the RRC is notified to release the configured SRS resource. Step 508: After the segment time, the base station sends the secondary cell activation MAC control element to activate CC2 and CC3. Step 509: After the UE applies the MAC control element, the UE needs to The CC2 of group 2 initiates a random access procedure to complete the uplink synchronization of group 2. Group 2 applies the TA value in the random access response, and the TAT of Group 2 restarts. After the uplink synchronization of group 2 is completed, the UE may send the SRS on CC2 and CC3 during the TAT operation phase. Embodiment 3 FIG. 6 is a detailed flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to Embodiment 3. As shown in FIG. 6, the method includes the following steps: Step 601: The UE initiates an RRC connection on CC1, and the base station The information of CC2 and CC3 and the packet information are configured to the UE in the RRC Connection Reconfiguration message. CC1 is the primary serving cell, which is group 1, CC2 and CC3 are the secondary serving cells, which constitute group 2; the TAT duration of group 1 is 1280 ms. The base station configures the TAT duration of the group 2 in the RRC connection reconfiguration message to be 750 ms. The base station configures the secondary cell deactivation timer to be infinite. Step 602: The base station sends a secondary cell activation MAC control element, and activates CC2 and CC3. Step 603: The UE initiates a random access procedure on the CC2 to establish uplink synchronization of the group 2. When the UE receives the TA in the random access response message, Group 2 TAT starts. After the uplink synchronization of the group 2 is completed, in the TAT operation phase, the UE may send the SRS on the CC2 and the CC3; Step 604: The base station sends the TA control element on the CC of the group 2 to perform the time adjustment of the group 2; Step 605: The UE restarts the TAT of the group 2 when receiving the TA control element of the group 2 sent by the base station. Step 606: When the TAT does not time out, the base station sends a secondary cell deactivation control element to activate CC2 and CC3. Step 607: After CC2 and CC3 are deactivated, the UE continues to maintain the TAT, at which time the SRS is stopped on CC2 and CC3. Step 608: After a period of time, the base station sends a secondary cell activation control element to activate CC2 and CC3. Step 609: The UE applies the control element to activate CC2 and CC3. At this time, the TAT has not expired. The UE does not need to initiate the random access procedure to establish the uplink synchronization of the group 2, but may continue to use the current TAT of the group 2; Step 610: After the period of time The TAT of group 2 times out, and CC2 and CC3 are still active. CC2 and CC3 are deactivated after the UE defaults TAT timeout. After the TAT times out, the TAT stops, and the HARQ memory corresponding to CC2 and P CC3 is cleared, releasing the configured SRS resources of CC2 and CC3. Embodiment 4 FIG. 7 is a detailed flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to Embodiment 4. As shown in FIG. 7, the method includes the following steps: Step 701: The UE initiates an RRC connection on CC1, and the base station The information of CC2 and CC3 and the packet information are configured to the UE in the RRC Connection Reconfiguration message. CC1 is the primary serving cell, which is group 1, CC2 and CC3 are the secondary serving cells, which constitute group 2; the TAT duration of group 1 is 1280 ms. The base station configures the TAT duration of the group 2 in the RRC connection reconfiguration message to be 750 ms. Step 702: The base station sends a secondary cell activation MAC control element, and activates CC2 and CC3. Step 703: The UE initiates a random access procedure on the CC2 to establish the group 2 Uplink synchronization, when the UE receives the TA in the random access response message, the TAT of group 2 is started. After the uplink synchronization of the group 2 is completed, the UE may send the SRS on the CC2 and the CC3 in the TAT operation phase; Step 704: The base station sends the TA control element on the CC of the group 2 to perform the time adjustment of the group 2; Step 705: The UE is in the When receiving the TA control element of the group 2 sent by the base station, restarting the TAT of the group 2; Step 706: - After the period of time, the TAT of the group 1 times out, and the TAT of the group 2 does not time out, and both CC2 and CC3 are activated. State, at this time, the UE defaults that all activated secondary cells are deactivated. At this time, consider the TAT of group 2. Timeout to stop the TAT. The UE and the base station respectively clear the HARQ buffers corresponding to the secondary cells. The UE notifies the RRC to release the SRS resources of these secondary cells. Embodiment 5 FIG. 8 is a detailed flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to Embodiment 5. As shown in FIG. 8, the method includes the following steps: Step 801: A UE initiates an RRC connection on CC1, and the base station The information of CC2 and CC3 and the packet information are configured to the UE in the RRC Connection Reconfiguration message. CC1 is the primary serving cell, which is group 1, CC2 and CC3 are the secondary serving cells, which constitute group 2; the TAT duration of group 1 is 1280 ms. The base station configures the TAT duration of the group 2 in the RRC connection reconfiguration message to be 750 ms. Step 802: The base station sends the secondary cell activation MAC control element, and activates the CC2 and the CC3. Step 803: The UE initiates a random access procedure on the CC2 to establish the group 2 Uplink synchronization, when the UE receives the TA in the random access response message, the TAT of group 2 is started. After the uplink synchronization of the group 2 is completed, the UE may send the SRS on the CC2 and the CC3 in the TAT operation phase; Step 804: The base station sends the TA control element on the CC of the group 2 to perform the time adjustment of the group 2; Step 805: The UE is in the When receiving the TA control element of the group 2 sent by the base station, restarting the TAT of the group 2; Step 806: - After the period of time, the TAT of the group 1 is 980 ms, that is, the TAT is about to time out, and the TAT of the group 2 is 200 ms, Timeout; both CC2 and CC3 are active. At this time, the base station considers that the TAT of the group 1 is about to time out, and the sending secondary cell deactivates the MAC control element to activate all currently activated secondary cells. Step 807: After the TAT of the group 1 times out, it is considered that the TAT of the group 2 times out, and the TAT is stopped. The UE and the base station respectively clear the HARQ buffer corresponding to the secondary cell deactivated due to the TAT timeout of the group 1. The UE notifies the RRC to release the SRS resources of these secondary cells. Embodiment 6 FIG. 9 is a detailed flowchart of a method for processing a time alignment timer in a multi-carrier communication system according to Embodiment 6. As shown in FIG. 9, the method includes the following steps: Step 901: A UE initiates an RRC connection on CC1, and the base station Configuring to the UE in the RRC Connection Reconfiguration message

CC2 and CC3 information and grouping information. CC1 is the main serving cell, which is composed of group 1, supplemented by CC2 and CC3. The serving cell, which is group 2; the TAT duration of group 1 is 1280 ms. The base station configures the TAT duration of the group 2 in the RRC connection reconfiguration message to be 750 ms. The base station configures the secondary cell deactivation timer to be infinite. Step 902: The base station sends a secondary cell activation MAC control element, and activates CC2 and CC3. Step 903: The UE initiates a random access procedure on CC2 to establish uplink synchronization of group 2. When the UE receives the TA in the random access response message, Group 2 TAT starts. After the uplink synchronization of group 2 is completed, the UE may send the SRS on CC2 and CC3 during the TAT operation phase. Step 904: The base station sends a TA control element on the CC of the group 2 to perform time adjustment of the group 2. Step 905: The UE restarts the TAT of the group 2 when receiving the TA control element of the group 2 sent by the base station. Step 906: When the TAT does not time out, the base station sends a secondary cell deactivation control element to activate CC2 and CC3. Step 907: After CC2 and CC3 are deactivated, the UE continues to maintain the TAT, and at this time, the SRS continues to be sent on CC2 and CC3. Step 908: The base station determines whether the group 2 of the UE needs to perform time adjustment by detecting the SRS sent on CC2 and CC3. Step 909: The base station sends the time adjustment MAC control element of group 2 on CC1. Step 910: The UE applies the time adjustment of the group 2 of the group 2 sent by the base station, and the TAT of the group 2 is restarted. Step 911: After a period of time, the base station sends a secondary cell activation control element to activate CC2 and CC3. Step 912: The UE application control element activates CC2 and CC3. At this time, the TAT has not expired. The UE does not need to initiate a random access procedure to establish uplink synchronization of the group 2, but may continue to use the current TAT of the group 2. Step 913: - After the period of time, the TAT of group 2 times out, and CC2 and CC3 are still active. CC2 and CC3 are deactivated after the UE defaults TAT timeout. After the TAT times out, the TAT stops, the HARQ memory corresponding to CC2 and P CC3 is cleared, and the UE does not send the SRS on CC2 and CC3. From the above description, it can be seen that the solution provided by the embodiment of the present invention solves the related art that only the primary cell maintains the TAT, and thus the UE cannot directly know the uplink synchronization status of the secondary cell packet, and the UE may be assisted by the UE. When the cell packet is in an out-of-synchronization state, the uplink transmission is performed, and the base station side cannot receive the uplink signal of the cells normally. The solution is adapted to the demand for multiple TAs and multiple packets in the multi-carrier communication system, and may be used for each sub-group. The group provides more accurate uplink synchronization control, which reduces the probability of error in uplink transmission, thus improving the service performance of the entire system. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device so that they may be stored in the storage device by the computing device, or they may be separately fabricated into individual integrated circuit modules, or Multiple modules or steps are made into a single integrated circuit module. Thus, the invention is not limited to any specific combination of hardware and software. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

A method for processing a time alignment timer in a multi-carrier communication system, comprising:

In the case where there are multiple packets, the user equipment UE maintains the duration of the respective time alignment timer TAT for each packet, wherein the cells using the same timing advance TA belong to the same packet; the UE corresponds to each packet according to each packet Whether the TAT expires and maintains the uplink synchronization status of the cells in the packet.

2. The method according to claim 1, wherein the TAT of the packet including the primary cell is started or restarted at:

The UE receives the time of the time advance command TAC related to the packet of the primary cell.

3. The method according to claim 1, wherein the TAT of the packet containing only the secondary cell is started or restarted at the following moment:

And a time when the UE receives the TA of the packet including only the secondary cell; or the time when the UE receives the TA control element of the packet including only the secondary cell.

4. The method according to claim 1, wherein, after all secondary cells in a packet including only a secondary cell are deactivated, if the TAT of the packet including only the secondary cell has not timed out, continuing to maintain the TAT.

The method according to claim 4, wherein, before the TAT timeout of the packet including only the secondary cell, if the secondary cell is activated in the packet including only the secondary cell, the activated secondary cell is activated. Still in the synchronization state, the activated secondary cell does not need to perform an uplink synchronization process.

6. The method according to claim 1, wherein, in an operation phase of a TAT of a packet including only a secondary cell, after all secondary cells in the packet including only the secondary cell are deactivated, the UE adopts deactivation. The method of continuing to send the SRS on the secondary cell to acquire the TA, where the predetermined secondary cell includes one of the following: a secondary cell configured with a duration of the TAT, and any one of the secondary cells.

The method according to claim 6, wherein, after the sending, by the UE, the SRS on the predetermined secondary cell in the packet that only includes the secondary cell, the method further includes: The UE restarts the TAT of the packet after receiving the TA adjustment value of the packet in which the secondary cell is sent by the primary cell, where the time adjustment required for the secondary cell is determined by the base station by detecting the SRS. The method according to claim 1, wherein the TAT of the packet including the primary cell maintains the original operating state in the following cases:

When the cell in the packet including the primary cell receives a TA control element sent by the base station to the packet including only the secondary cell; and/or

After the UE receives and activates the activation or deactivation command of the secondary cell in the packet including the primary cell, at least one cell in the packet including the primary cell is in an active state; and/or

In the case where the TAT in the packet containing only the secondary cell times out. The method according to claim 1, wherein the timeout processing of the TAT of the packet including the primary cell includes at least one of the following:

When the TAT of the packet containing the primary cell is timed out but the TAT of the packet containing only the secondary cell does not time out, the TAT of the packet containing only the secondary cell is timed out by default;

When the TAT of the packet containing the primary cell is timed out but the TAT of the packet containing only the secondary cell has not timed out, all the auxiliary secondary cells in the packet containing only the secondary cell are deactivated according to the indication of the base station. The method according to claim 1 or 9, wherein the timeout processing of the TAT of the packet including only the secondary cell includes at least one of the following:

When the TAT of the packet including only the secondary cell expires, the TAT is stopped, and if the activated secondary cell exists in the packet including only the secondary cell, according to the indication of the base station, the UE includes the secondary cell only Initiating a random access procedure in a certain secondary cell activated in the packet to establish an uplink synchronization of the packet including only the secondary cell, and after the acquiring the TA, the UE starts the TAT of the packet including only the secondary cell;

When the TAT of the packet including only the secondary cell expires, the TAT is stopped, and all the secondary cells in the packet including only the secondary cell are deactivated according to the indication of the base station;

When the TAT of the packet including only the secondary cell expires, the TAT is stopped, and the base station and the UE acquiescence that all the secondary cells in the packet including only the secondary cell have been deactivated;

Deleting a configuration of all the secondary cells in the packet including only the secondary cell when the TAT of the packet including only the secondary cell expires; When the TAT of the packet including only the secondary cell times out, clearing the HARQ memory of all the secondary cells in the activated state only the secondary cell, the UE stops all in the packet including only the secondary cell Sending an SRS on the secondary cell, releasing or retaining the SRS resources of all the secondary cells in the packet including only the secondary cell;

If the TAT distance of the packet including only the secondary cell has a predetermined duration, if the secondary cell still exists in the packet including only the secondary cell, the active cell is activated according to the indication of the base station. All the secondary cells in the packet of the cell stop the TAT when the TAT of the packet including only the secondary cell times out;

In a case where the TAT distance of the packet including only the secondary cell has a predetermined time remaining, the base station and the UE default that all the secondary cells in the packet including only the secondary cell have been deactivated, when the secondary cell only includes the secondary cell When the TAT of the packet times out, the TAT is stopped;

When the TAT distance of the packet including only the secondary cell has a predetermined duration, the all the secondary cells in the packet including only the secondary cell are deactivated according to the indication of the base station, and the packet including only the secondary cell is cleared. In the HARQ memory of all the secondary cells in the active state, the UE stops transmitting SRS on all the secondary cells in the packet including only the secondary cell, and releases or reserves all the secondary cells in the packet including only the secondary cell. SRS resource, when the TAT of the packet containing only the secondary cell times out, stopping the TAT;

When the TAT distance of the packet including only the secondary cell has a predetermined duration, the base station and the UE default that all the secondary cells in the packet including only the secondary cell have been deactivated, and the secondary only includes the secondary cell. The HARQ memory of all the secondary cells in the active state in the packet, the UE stops transmitting the SRS on all the secondary cells in the packet including only the secondary cell, and releases or reserves all the secondary cells in the packet including only the secondary cell. The SRS resource stops the TAT when the TAT of the packet containing only the secondary cell times out.

The method according to any one of claims 1 to 9, wherein before maintaining the duration of the respective time alignment timer TAT for each packet, the method further includes:

Receiving, by the base station, the duration of the TAT configured for each packet, where the durations of the TATs of different packets are the same or different.

The method according to claim 11, wherein the duration of the TAT is configured in the cell configuration information, and the cell in which the cell configuration information is configured is used as a cell managing TAT in the packet.

The method according to any one of claims 1 to 9, wherein cells using the same TA and time reference belong to the same packet.

14. A processing device for a time alignment timer in a multi-carrier communication system, comprising:

The time alignment timer TAT duration maintenance module is configured to maintain the duration of the respective TAT for each packet in the case where there are multiple packets, wherein the cells using the same timing advance TA belong to the same packet; The maintenance module is configured to maintain an uplink synchronization state in the packet according to whether the TAT corresponding to each packet times out.

The apparatus according to claim 14, wherein the uplink synchronization state maintenance module and the TAT duration maintenance module are located at a base station side or a UE side.

16. The apparatus of claim 14, further comprising:

The configuration module, located at the base station side, is configured to configure a duration of the respective TAT for each packet, where the durations of the TATs of different packets are the same or different.

The apparatus according to any one of claims 14-16, wherein cells using the same TA and time reference belong to the same packet.

18. A method of processing a time alignment timer in a multi-carrier communication system, comprising:

In the case where there are multiple packets, the user equipment UE maintains the duration of the respective time alignment timer TAT for each packet, wherein the cells belonging to the same packet satisfy at least one of the following conditions: using the same timing advance TA, Use the same time reference;

The UE maintains the uplink synchronization state of the cell in the packet according to whether the TAT corresponding to each packet times out.

19. A processing device for a time alignment timer in a multi-carrier communication system, comprising:

The time alignment timer TAT duration maintenance module is configured to maintain the duration of the respective TAT for each packet in the case where there are multiple packets, wherein the cells belonging to the same packet satisfy at least one of the following conditions: use the same time Advance TA, use the same time reference;

The uplink synchronization state maintenance module is configured to maintain an uplink synchronization state in the packet according to whether the TAT corresponding to each packet times out.