CN1229953C - Cross-area method without data loss in wireless communication system - Google Patents

Abstract

The present invention provides a method for ensuring data loss-free when a wireless communication system crosses regions. The wireless communication system includes a plurality of wireless network subsystems, including a service subsystem and a target subsystem. When a mobile communication unit moves from the effective communication area of the service subsystem to the effective communication area of the target subsystem, the service subsystem provides a transport message to the target subsystem, and the transport message includes a data unit that has not been reported by the mobile communication unit for confirmation of receipt, the sequence number of the first data unit that has not been confirmed for receipt, and the sequence number of the last data unit that has been transmitted but has not been confirmed for receipt.

Description

Cross-area method without data loss in wireless communication system

(1) Technical field

The invention provides a method applied in a wireless communication system, especially a wireless network subsystem cross-area method without data loss.

(2) Background technology

Please refer to Figure 1. FIG. 1 is a block diagram illustrating a conventional wireless communication network 10. The wireless communication network 10 includes a plurality of radio network subsystems (radio network subsystems, RNSs) 20, and a communication network capable of communicating with the plurality of radio network subsystems 20. Data core network (core network, CN) 30, each wireless network subsystem 20 includes a radio network controller (radio network controller, RNC) 22, and a plurality of base stations (nodes) that can transmit data with the radio network controller 22 B) 24. Each base station 24 includes a transceiver for transmitting and receiving wireless signals. The wireless communication network 10 can assign the communication data sending and receiving processing right of a mobile communication unit (mobile unit) 40 to a specific wireless network subsystem 20. At this time, the specific wireless network subsystem 20 is called the mobile communication unit 40 The serving subsystem (servingRNS, SRNS) 20s. The downlink data to be sent to the mobile communication unit 40 must first be sent to the service subsystem 20s via the core network 30, and the downlink data is first stored in the service subsystem 20s in the form of data units (service data units, SDUs) 28 Then the wireless network controller 22 will select an optimal base station according to the position of the mobile communication unit 40 in the effective communication area of the service subsystem 20s 24 transmits the data of the data unit 28 to the mobile communication unit 40 precisely. The mobile communication unit 40 transmits the uploaded data of the plurality of data units 48 to the wireless communication system 10 by wireless transmission. The service subsystem 20s first receives the data and then transmits the data to the core network 30 . Sometimes, the mobile communication unit 40 will move to a position close to the effective communication area of another wireless network subsystem 20. At this time, the wireless network subsystem 20 is called a temporary wireless network subsystem (drift RNS, DRNS) 20d, And a certain base station 24 in the temporary wireless network subsystem 20d can receive the data uploaded by the data unit 48 sent by the mobile communication unit 40, and then, the wireless network controller 22 of the temporary wireless network subsystem 20d will receive the received The data of the data unit 48 is sent to the service subsystem 20s, and the service subsystem 20s transmits all received data of the data unit 48 to the core network 30. Therefore, in this conventional communication system, all bidirectionally transmitted data between the mobile communication unit 40 and the core network 30 must pass through the service subsystem 20s.

Please refer to Figure 1 and Figure 2. FIG. 2 is a block diagram illustrating the wireless network controller 22 in the service subsystem 20s in FIG. 1, the data transmission between the mobile communication unit 40 and the wireless network controller 22 is via a multi-layer communication protocol (multi-layer communication protocol), the multi-layer communication protocol includes a packet data convergence protocol layer (packet data convergence protocol, PDCP) 22p, an upper layer 22u and a lower layer 22L. The packet data convergence protocol layer 22p can perform data conversion with the upper layer 22u and the lower layer 22L respectively. The PDCP layer 22p can receive a plurality of data units 28 from the upper layer 22u, and each data unit 28 includes a header 28h and a data area 28d. The main function of the data unit 28 is to transmit the data in the data area 28d to the destination specified by the header 28h. The function of the header 28h is similar to the header function of the Internet Protocol. The header 28h may contain some redundant data or contain some Data that duplicates headers 28h of other data units s28. The main function of the packet data convergence protocol layer 22p is to compress the data in the header 28h so that the communication bandwidth can be fully utilized, and the compression process is performed by a header compressor/decompressor 22c Finish. The title compression/decompression processor 22c receives the data of the data unit 28, and then generates a packet data convergence protocol layer communication protocol data unit (PDCP protocol data unit, PDCP PDU) 29, and the packet data convergence protocol layer data unit 29 includes a The packet data includes a protocol layer header 29h and a data area 29d, and the data area 29d further includes a compressed header 29x generated by the header compression/decompression processor 22c according to the header 28h. Each packet data convergence protocol layer data unit 29 is endowed with a 16-bit serial number (sequential number, serial number) 29s by the packet data convergence protocol layer 22p, for example, if a first packet data convergence protocol layer data The sequence number 29s assigned to the unit 29 is 62, and the sequence number 29s assigned to the second packet data convergence protocol layer data unit 29 following the first packet data convergence protocol layer data unit 29 is 63, and the rest By analogy. Each serial number 29s is not transmitted together with the packet data convergence protocol layer data unit 29, but is additionally stored and maintained inside the packet data convergence protocol layer 22p. The PDCP layer data unit 29 can then be transmitted to the lower layer 22L for further transmission processing. Because the packet data convergence protocol layer data unit 29 and the data unit 28 are one-to-one correspondence, and because each packet data convergence protocol layer data unit 29 has a designated sequence number 29s, each corresponding data The unit 28 also has its corresponding serial number 29s, that is to say, the serial number 29s corresponds to the packet data convergence protocol layer data unit 29 and the data unit 28 at the same time. Because the bandwidth can be fully utilized by compressing the header 28h, the data length of each packet data convergence protocol layer data unit 29 should theoretically be smaller than the data length of its corresponding data unit 28. In order to ensure that the above conditions are met, The packet data convergence protocol layer header 29h should be as small as possible. The header compression mode used by the header compression/decompression processor 22c is determined by the format of the header 28h. For example, if the header 28h is an IP header, the header compression mode must comply with the IP industry standard RFC 2507.

Similarly, the packet data convergence protocol layer data unit 27 data (sent from the mobile communication unit 40) transmitted from the lower layer 22L will also be sent to the header compression/decompression processor 22c to generate the corresponding data unit s48, Then the corresponding data unit 48 is sent to the upper layer 22u. Each received packet data convergence protocol layer data unit 27 has a 16-bit sequence number 27s assigned by the packet data convergence protocol layer 22p, similar to the case of the sequence number s29s, the 16-bit sequence number 27s also corresponds to to the corresponding data unit 48.

When the mobile communication unit 40 is getting closer to the effective communication area of the temporary wireless network subsystem 20d, more and more data units 48 will be received by the temporary wireless network subsystem 20d and sent out, so that the wireless communication network 10 Finally, a handover procedure will be started to process the data transmitted from the mobile communication unit 40 to the temporary wireless network subsystem 20d. This handover procedure is called a service subsystem handover procedure or a wireless network subsystem handover procedure. The program requires that there must be no data loss. The so-called no data loss means that there is no data loss in the downlink data unit 28 and the uplink data unit 48 in the transfer procedure.

Please refer to Figure 1, Figure 2, and Figure 3. Fig. 3 is a block diagram showing that the conventional mobile communication unit 40 experiences the transfer procedure of the service subsystem without data loss, wherein the temporary wireless network subsystem 20d becomes a target subsystem (target RNS, TRNS) 20t in Fig. After completing the service subsystem transfer procedure, the target subsystem 20t will become the new service subsystem 20s of the mobile communication unit 40 . In order to enable the target subsystem 20t to completely continue the work of the service subsystem 20s on the mobile communication unit 40, the old service subsystem 20s must deliver all key information to the target subsystem 20t (that is, the new service subsystem) System 20s). Please refer to Figure 2, Figure 3, and Figure 4. FIG. 4 is an information transmission diagram showing a transfer procedure of a conventional service subsystem without data loss. The service subsystem 20s in FIG. 4 transmits the delivery information 50 to the target subsystem 20t, and the delivery information 50 includes a downlink sending sequence number. number, DL Send_sequence number) 52, an uplink receiving sequence number (uplink receiving sequence number, ULReceive_serial number) 54, and all unacknowledged downlink data units (unconfirmed data units) 28. In this multi-layer communication protocol commonly used by the service subsystem 20s and the mobile communication unit 40, the mobile communication unit 40 can report and confirm that it has successfully received the packet data transmitted by the service subsystem 20s to converge the protocol layer The data unit 29, any PDCPL data unit 29 received by the mobile communication unit 40 but not acknowledged, is called an unconfirmed PDCPL data unit s29. Since there is a one-to-one correspondence between the data unit 28 and the packet data convergence protocol layer data unit 29, if any unconfirmed packet data convergence protocol layer data unit 29 occurs, it means that there is a corresponding unconfirmed The data unit 28 exists, and these unconfirmed data units s28 can be transported to the target subsystem 20t by the service subsystem 20s, wherein DL Send_sequence number 52 is the data unit 29 of the earliest unconfirmed downlink packet data convergence communication protocol layer The associated sequence number value is sequence number 29s. Since the sequence number 29s is not explicitly contained in the data unit 28, the downlinked transmission sequence number information enables the target subsystem 20t to correctly assign a sequence number 29a to the PDCPL data unit 29 corresponding to each transported data unit 28 . The upload receiving serial number 54 prepares for the service subsystem 20s to receive the packet data of the next upload data from the mobile communication unit 40, converges the serial number value serial number 27s associated with the communication protocol layer data unit 27, which will enable the target subsystem 20t to be correct Assign a sequence number 27s to each subsequent packet data convergence protocol layer data unit 27 uploaded from the mobile communication unit 40 . The target subsystem 20t transmits the upload receiving sequence number 54 to the mobile communication unit 40, so that the mobile communication unit 40 can determine which data unit 48 starts to transmit to the target subsystem 20t which becomes the new service subsystem 20s, and the mobile communication unit 40 Send a downlink receiving sequence number (DL Receive_sequence number) 58 to the target subsystem 20t, and the downlink receiving sequence number 58 is the packet data convergence of the next data that the mobile communication unit 40 prepares to receive from the target subsystem 20t The serial number associated with the protocol layer data unit 29 is the serial number 29s. Therefore, the service subsystem 20t can determine which unconfirmed data unit 28 starts to download data to the mobile communication unit 40 accordingly. For example, if the service subsystem 20s has sent the packet data with sequence number 29s from 0 to 99 in the PDL unit 29 to the mobile communication unit 40, it is assumed that the 100 transmitted packet data in the PDL unit s29 , only the part of the sequence number s29s from 0 to 50 is confirmed by the mobile communication unit 40, that is to say, the transmitted packet data convergence communication protocol layer data unit 29 of the other sequence number 29s from 51 to 99 has not been confirmed by the mobile communication unit 40 confirmed, and at the same time, each unconfirmed packet data convergence protocol layer data unit s29 has its corresponding unconfirmed data unit 28 . It is also assumed that the service subsystem 20s has received 200 packet data convergence communication protocol layer data units 27 with serial numbers 27s from 0 to 199 from the mobile communication order 40. Forty-nine data units 28 are transported from the service subsystem 20s to the target subsystem 20t. At this time, the value of the downlink sending sequence number 52 will be set to 51, the value of the upload receiving sequence number 54 will be set to 200, and The value of the downlink receiving sequence number will be between 51 and 100. This value range is determined by the number of packet data convergence protocol layer data units 29 received by the mobile communication unit 40 but not yet confirmed. For example, if The value of the downlink receiving sequence number 58 is 90, then the target subsystem 20t can discard the thirty-nine transport data units 28 with the sequence numbers 29s from 51 to 89, and start to transmit the transport data units 28 with the sequence numbers 29s above 90, Another situation that should not happen but may happen is that the downlink receiving sequence number 58 may be sorted before the downlink sending sequence number 52 or after the sequence number 29s of the last transported data unit 28. The occurrence of this situation indicates that the service subsystem 20s The sequence numbers 29s and/or 27s maintained by the radio network controller 22 of the wireless network controller 22 have lost synchronization with the corresponding sequence numbers maintained by the mobile communication unit 40 (out of synchronization). At this time, the target subsystem 20t will start a resynchronization program (re -synchronization), in this re-synchronization procedure, the target subsystem 20t will send a plurality of packet data convergence protocol layer data units s29 including the relevant sequence numbers 29s in a plurality of packet data convergence protocol layer headers 29h, and from corresponding to the sequence The earliest PDCPL data unit 29 of the transport data unit 28 starts to transmit, and once the mobile communication unit 40 has confirmed any one of the plurality of PDCPL data units 29, the target subsystem 20t will stop The sequence number 29s is included in the packet data convergence protocol layer header 29h. In general synchronous cases, it is unnecessary to include the sequence number 29s in the PDCP layer header 29h, because this will cause the PDCP layer header 29h to become larger. However, including the sequence number 29s in the PDCP layer header 29h is unnecessary. The layer header 29h has the function of synchronizing the internal serial number of the mobile communication unit 40 with the serial number of the service subsystem 20s.

However, the conventional service subsystem transfer procedure cannot detect every opportunity to perform the resynchronization procedure. Consider a certain initial condition that the service subsystem 20s contains 30 unacknowledged data units 28, wherein the first 20 unacknowledged data units 28 have been transmitted but have not yet been acknowledged, and the last 10 unacknowledged data units 28 It has not been sent out yet. During the transfer process of the service subsystem, all the 30 unconfirmed data units 28 are transported to the target subsystem 20t, assuming that the relevant serial number 29s of the first unconfirmed data unit 28 is 101, then the serial number 52 is sent down The value is 101. At this time, according to the value of the serial number 58 received in the download, there are four situations as follows:

Situation 1: If the value of the serial number 58 received in the downlink is less than 101, the resynchronization procedure must be executed, because all data units 28 are received and confirmed according to the order of serial numbers, so if the program is correct, all serial numbers less than 101 are earlier The receipt has been confirmed by the mobile communication unit 40 to the service subsystem 20s. At this time, the value should not be sent again. Therefore, it is determined that an out-of-synchronization situation occurs, and a resynchronization procedure should be performed.

Situation 2: If the value of the downlink receiving sequence number 58 is between 101 and 121, which is a typical situation, the mobile communication unit 40 can confirm that it has received part or all of the first 20 messages sent by the service subsystem 20s. As for the unconfirmed data unit 28, no resynchronization procedure needs to be performed at this time.

Situation 3: If the value of the downlink receiving sequence number 58 exceeds 131, it means that the mobile communication unit 40 has received the data unit 28 that the service subsystem 20s does not have, has not been transported, and is even less likely to be transmitted. This must be from In an out-of-sync condition, a resynchronization procedure is required.

Situation 4: If the value of the serial number 58 received by the download is between 122 and 131, this is the last and most important situation, because the service subsystem 20s has never transmitted data with the serial number 29s between 121 and 130 Unit 28, but some of them are considered to have been received by the mobile communication unit. This is obviously from an out-of-synchronization situation, and a resynchronization procedure should have been performed originally. However, since the target subsystem 20t is not provided enough information to infer that this has occurred. Therefore, as mentioned above, the multiple transported data units 28 corresponding to the sequence numbers 29 s sorted before the downlink receiving sequence number 58 will be discarded by the target subsystem 20 t, resulting in data loss.

(3) Contents of the invention

Therefore the main purpose of the present invention is to provide a service subsystem (S wireless network subsystem) handover method without data loss, so that the new service subsystem can detect when any possible occurrence of a mobile communication unit with the service subsystem In case of out-of-synchronization, a re-synchronization procedure needs to be performed to avoid any data loss and solve the above-mentioned problems.

In a wireless communication system of the present invention, a method for achieving lossless relocation of S wireless network subsystems in a wireless communication system includes (a) providing a plurality of wireless network subsystems, which exchange data with a core network together, The multiple wireless network subsystems include a service subsystem and a target subsystem. The service subsystem provides data units s to a mobile communication unit from the core network in a wireless communication manner. The service subsystem assigns each a serial number of the data unit, the mobile communication unit can report and confirm receipt of the data unit sent by the service subsystem, (b) the service subsystem provides a delivery data to the target subsystem, the delivery data includes the service subsystem unacknowledged data unit s, a first sequence number value that enables the target subsystem to interpret the sequence number corresponding to the first unacknowledged and untransmitted data unit in the serving subsystem, and (c) enables the The target subsystem replaces the serving subsystem and becomes a new serving subsystem of the mobile communication unit.

(4) Description of drawings

FIG. 1 is a block diagram of a conventional wireless communication system.

FIG. 2 is a block diagram of the radio network controller (RNC) of the serving subsystem (SRNS) of FIG. 1 .

FIG. 3 is a block diagram of the mobile communication unit in FIG. 1 undergoing the transfer procedure of the no-data-loss service subsystem.

FIG. 4 is an information transfer diagram of a transfer procedure of a conventional no-data-loss service subsystem.

FIG. 5 is a block diagram of a wireless communication system according to the present invention.

FIG. 6 is an information transfer diagram of the transfer procedure of the non-data loss service subsystem according to the present invention.

(5) specific implementation

In the following description, the mobile communication unit can represent a mobile phone (mobile phone), a handheld transceiver (handheld transceiver), a base station (base station), a personal digital assistant (personal digital assistant, PDA), a computer, or any other need Elements of wireless data transmission, that is, any mechanism that can affect wireless transmission at the physical layer and is applicable to the system disclosed in the present invention.

Please refer to Figure 5. FIG. 5 is a block diagram of a wireless communication system 50 according to the present invention. The wireless communication system 50 includes a core network (core network, CN) 60 that can communicate with a plurality of radio network subsystems (radio network subsystems, RNSs) 70, and each radio network subsystem 70 includes a network that can communicate with a plurality of base stations 74 A wireless network controller (radio network controller, wireless network controller) 72 for transmitting data, each base station 74 includes a transceiver (transceiver), used for transmitting and receiving wireless signals to a mobile communication unit 80 . Each wireless network controller 72 controls its individual multiple base stations 74 so as to have the best communication efficiency between it and the mobile communication unit 80 . In special cases, the communication data sending and receiving processing right of the mobile communication unit 80 can be given to a certain special wireless network subsystem 70. At this time, the wireless network subsystem 70 is called a serving subsystem (serving RNS, SRNS) 70s. Since the mobile communication unit 80 transmits data with the core network 60 via the service subsystem 70s, the service subsystem 70s is the main data transmission channel between the mobile communication unit 80 and the core network 60 .

The data transmitted to the mobile communication unit 80 via the service subsystem 70s is transmitted in the form of data units (service data units, SDUs) 78, and each data unit 78 is given a 16-bit sequence number (sequence number, SN) 78s, the sequence number s78s is assigned by the radio network controller 72 of the service subsystem 70s. The value of each sequence number 78s is determined according to the ordering of each downlink data unit 78 . Therefore, the sequence number 78s corresponding to the data unit 78 sorted earlier should be smaller than the sequence number s78s corresponding to the data unit 78 sorted behind. In the same way, the mobile communication unit 80 will assign a sequence number 88s to each upload data unit 88 received by the service subsystem 70s. For a downlink data unit 78 transmitted by the service subsystem 72, its sequence number 78s should be the same as The corresponding sequence number 88s of the downlink data unit 88 received by the mobile communication unit 80 is equal. This equal situation means that the service subsystem 70s is synchronized with the mobile communication unit 80. If the downlink sequence number 78s and the downlink sequence number 88s If there is no above-mentioned equal synchronization situation between the upload sequence number 78s and the upload sequence number 88s, the synchronization procedure must be started again.

When the mobile communication unit 80 successfully received a data unit 88 corresponding to the transmitted data unit 78, the mobile communication unit 80 had the function of reporting the successfully received information to the service subsystem 70s, and this reporting work is usually referred to as a response to The reception confirmation of the data unit 78, and the data unit 78 must be confirmed in order, that is to say, the mobile communication unit 80 cannot confirm the data unit 78 received after the sequence before confirming the data unit 78 sequenced in front, any data unit 78 It is called an unacknowledged data unit 78 before it is acknowledged by the mobile communication unit 80 . Therefore, there are two possible situations for the unacknowledged data unit 78. One is that the data unit 78 has been sent by the service subsystem 70s but has not been confirmed yet, and the mobile communication unit 80 may or may not have successfully received the data. unit 78, and the other is that the data unit 78 has not been sent out by the service subsystem 70s at all. Normally, the serial number 78s will not be sent out along with the data unit 78, but if the resynchronization procedure is activated, then the serial number 78s will be sent out along with the data unit 78, and when the mobile communication unit 80 receives the serial number 78s When the data unit 88 is selected, the mobile communication unit 80 will use the serial number 78s to assign the corresponding serial number value serial number 88s, and then, the mobile communication unit 80 can perform the confirmation of the corresponding data unit 78, and then terminate the resynchronization procedure.

When the mobile communication unit 80 gradually moves out of the effective communication area of the service subsystem 70s, it also means that the mobile communication unit 80 will gradually move into the effective communication area of another wireless network subsystem 70. At this time, it must be decided to prepare the mobile communication unit 80. The communication processing right is given to a target subsystem (target RNS, TRNS) 70t to make it a new service subsystem 70s, so it is necessary to implement a service subsystem without data loss for the service subsystem 70s and the target subsystem 70t Transfer program, after the program is completed, the target subsystem 70t replaces the old service subsystem 70s and becomes the new service subsystem 70s to execute the communication processing right to the mobile communication unit 80 . Please refer to FIG. 5 and FIG. 6. FIG. 6 is an information transfer diagram of the service subsystem transfer procedure without data loss according to the present invention. In order to ensure that the target subsystem 70t can completely replace the service subsystem 70s, it is sufficient to act as a new service subsystem. The system 70s, the service subsystem 70s will send all relevant information of the mobile communication unit 80 to the target subsystem 70t, and the delivery information 90 includes a first value 91 (hereinafter referred to as the first serial number 91), a second value 92 (hereinafter referred to as the second sequence number 92), a third value 93 (hereinafter referred to as the third sequence number 93), and all unacknowledged data units 78 regardless of whether they have been sent out by the service subsystem 70s. Target subsystem 70t can thus retrieve shipment data unit 78f from shipment information 90 . The first sequence number 91 is the last sending sequence number (downlink last_send sequence number, DLLast_sequence number) 91 for downlink, and its value is set to the next data of the last data unit 78 that has been sent out by the service subsystem 70s and has not been confirmed. The serial number of the unit 78 is the serial number 78s, that is, the serial number 78s of the unconfirmed data unit 78 that is ranked the earliest in the delivery information 90 and has not been sent out by the service subsystem 70s. The first sequence number 91 will thus enable the target subsystem 70t to distinguish between the transport data unit 78f that has been sent out by the service subsystem 70s and the transport data unit 78f that has not been sent out by the service subsystem 70s, and this is the method of the present invention main key. The second sequence number 92 is a downlink sending sequence number (DL Send_sequence number) 92, and its value is set to the sequence number 78s of the earliest unconfirmed data unit 78 sorted in the delivery information 90. Since each serial number 78s is not sent along with its corresponding data unit s78 in the shipping information 90, the second serial number 92 will enable the target subsystem 70t to assign a corresponding serial number 78fs to each shipping data unit 78f, Make each serial number 78fs equal to its corresponding serial number 78s. The third sequence number 93 is an upload receiving sequence number (uplink receiving sequence number, UL Receive_serial number) 93, and its value is equal to the next data unit 78r that the service subsystem 70s expects to receive from the mobile communication unit 80 and is received by the service subsystem 70s The set corresponding sequence number 78rs, the third sequence number 93 will therefore enable the target subsystem 70t to correctly assign the corresponding sequence number value to each upload data unit transmitted by the mobile communication unit 80 in the future. After receiving the shipping information 90, the target subsystem 70t sends the third serial number 93 to the mobile communication unit 80, and enables the mobile communication unit 80 to determine from which data unit to start uploading. In addition, the mobile communication unit 80 transmits a fourth value 94 (hereinafter referred to as the fourth sequence number 94) to the target subsystem 70t, the fourth sequence number 94 is a downlink receiving sequence number (DL Receive_sequence number) 94, And it is equal to the next data unit 88 that the mobile communication unit 80 expects to receive from the target subsystem 70t, and the mobile communication unit 80 is assigned a corresponding sequence number 88s, the fourth sequence number 94 will therefore allow the target subsystem 70t to determine which should be delivered from Which one of the data units 78f begins the transfer. Since the transport data units 78f sorted before the fourth serial number 94 have been successfully received by the mobile communication unit 80, no further transmission is required, and thus can be discarded by the target subsystem 70t. After the target subsystem 70t has the shipping information 90 and the fourth serial number 94, it has all the information needed to perform the work of the service subsystem 70s. Therefore, all the communication processing work related to the mobile communication unit 80 is transferred to the target subsystem 70t, and the target subsystem 70t becomes the new service subsystem 70s which handles the communication work of the mobile communication unit 80.

By providing the first sequence number 91 in the delivery message 90, the method of the present invention enables the target subsystem 70t to detect an out-of-sync condition between the downstream sequence number 88s and its corresponding downstream sequence number 78fs, and thus initiate the required resynchronization process. Still taking the aforementioned example as an example, assume the same initial condition, that is, the service subsystem 70s has 30 unconfirmed data units 78, among which the first 20 unconfirmed data units 78 have been sent out but have not been confirmed , and the last 10 unacknowledged data units 78 have never been sent out. In the serving subsystem transfer procedure, all of the 30 unacknowledged data units 78 are shipped to the target subsystem 70t to provide corresponding shipped data units 78f, assuming the associated sequence number 78s of the first unacknowledged data unit 78 is 101, then the value of the second serial number 92 in the shipping information 90 is 101. The value of the first sequence number 91 is 121 because 20 transported data units 78f have been sent out by the service subsystem 70s. As for the value of the third serial number 93, it is determined according to the serial number 78rs of the data unit 78r received by the service subsystem 70s from the mobile communication unit 80. For example, if the service subsystem 70s receives 100 data units from the mobile communication unit 80 unit 78r, and the value of the serial number 78rs of the 100 data units 78r is between 0 and 99, then the value of the third serial number 93 is 100. At this time, according to the value of the fourth serial number 94, the following four situations also occur similarly:

Situation 1: The value of the fourth serial number 94 is less than 101. Because the mobile communication unit 80 should not request the target subsystem 70t to retransmit the data unit 88 which has been confirmed to be received, the target subsystem 70t deduces that the serial number is out of sync. Therefore, the resynchronization procedure is executed, and all transport data units s78f are sent to the mobile communication order 80 .

Situation 2: If the value of the fourth serial number 94 is between 101 and 121, including 101 and 121, which is a typical situation, the mobile communication unit 80 can confirm that it has received some or all of the first 20 messages from the service subsystem. The unconfirmed data unit 78 transmitted by 70s does not need to execute the resynchronization program at this time, and the target subsystem 70t starts to transmit the data unit 78f whose sequence number 78fs is equal to the fourth sequence number 94 sequentially, and other sorts are in the fourth sequence number 94 The previous data units 78f are all discarded.

Situation 3: If the value of the fourth serial number 94 exceeds 131, it means that the mobile communication unit 80 has received the data unit 88 that the service subsystem 70s does not have, and certainly has never transmitted, which is impossible. Unless an out-of-sync condition occurs, the target subsystem 70t needs to execute the resynchronization process and send all transport data units 78f out from the target subsystem 70t.

Situation 4: If the value of the fourth serial number 94 is between 122 and 131, including 122 and 131, because the value of the fourth serial number 94 exceeds the value of the first serial number 91, the target subsystem 70t knows that the service subsystem 70s does not The transmission data unit 78f whose serial number 78fs is between 121 and 130 has been transmitted, but some of these serial number values are reported by the mobile communication unit 80 as confirmation of receipt, and it is determined that there must be an out-of-synchronization situation, so the target subsystem 70t needs to perform the resynchronization procedure, all transported data units 78f are transferred to the mobile communication unit 80 by the target subsystem 70t.

Although the definition and use of the first serial number 91 of the present invention have been disclosed above, other similar serial number information may also achieve the desired purpose. The system 70s transmits the serial number 78s of the last data unit 78 that was sent out. In short, no matter which definition is used, the purpose of the first sequence number 91 is to enable the target subsystem 70t to distinguish between the data unit 78f that has been transmitted by the service subsystem 70s and the data unit that has not been transmitted by the service subsystem 70s 78f, and this is the main key point of the method of the present invention. Similarly, the second sequence number 92 , the third sequence number 93 , and the fourth sequence number 94 can be deduced by analogy.

Compared with the conventional transfer method of the service subsystem, the present invention provides a first sequence number 91 to the delivery information 90, the first sequence number 91 can be used by the target subsystem 70t to distinguish the data unit 78f transmitted by the service subsystem 70s With the data unit 78f that has not been transmitted by the service subsystem 70s, all possible sequence number out-of-synchronization situations can be detected in this way, and a service subsystem transfer method that ensures no data loss is completed in the present invention.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes or equivalent replacements made according to the scope of the patent application of the present invention shall fall within the scope of the patent of the present invention.

Claims (7)

1. A method for completing interregional crossing without data loss in a wireless communication system, characterized in that it comprises: Provide a plurality of wireless network subsystems, which jointly transmit data with a core network. The plurality of wireless network subsystems include a service subsystem and a target subsystem. The service subsystem is transmitted from the core network by means of wireless communication providing a plurality of data units to a mobile communication unit, the service subsystem assigns a serial number to each data unit, and the mobile communication unit can report receipt of the data unit sent by the service subsystem; A shipment data is provided by the service subsystem to the target subsystem, the shipment data includes: unacknowledged data units for the service subsystem; and a first value that enables the target subsystem to decipher the sequence number corresponding to the first data unit in the transport data unit that has not been transmitted by the serving subsystem; and The target subsystem replaces the service subsystem and becomes a new service subsystem of the mobile communication unit. 2. The method of claim 1, wherein the shipping data includes all data units that have not yet been confirmed. 3 . The method of claim 2 , wherein the shipment data further includes a second value, which enables the target subsystem to read the sequence number corresponding to the top unacknowledged data unit in the shipment data. 4 . 4. The method according to claim 3, wherein the delivery data further includes a third value corresponding to the next data unit that the service subsystem is prepared to receive from the mobile communication unit serial number. 5. The method of claim 4, further comprising: The mobile communication unit provides a fourth value to the target subsystem, and the fourth value is the sequence number corresponding to the next data unit to be received by the mobile communication unit from the target subsystem; wherein, if the fourth The value is the number before the sequence number corresponding to the highest sorted unacknowledged data unit in the transport data, or if the fourth value is the number corresponding to the first unacknowledged data unit that has not been transmitted by the service subsystem For the number after the serial number, the synchronization procedure is performed again and again. 6. The method of claim 1, wherein the first value is a sequence number corresponding to the first unacknowledged data unit that has not been transmitted by the service subsystem. 7. The method according to claim 1, wherein the first value is a sequence number corresponding to the last unacknowledged data unit sent to the mobile communication unit by the service subsystem.

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