KR20030017953A - Transport method for data of radio link control layer - Google Patents

Abstract

PURPOSE: A data transfer method of wireless link control layer is provided to service an operation mode where data loss is not admitted and support a mode where the discard of RLC SDU is admitted and a mode at which the discard of the RLC SDU is not admitted. CONSTITUTION: An acknowledge mode of a wireless link control(RLC) layer confirms whether the discard of RLC SDU is admitted(701,702) and supports the first mode where a discard of RLC SDU is admitted and the second mode where the discard of the RLC SDU is not admitted(704). The first mode(703) is divided into three SDU discard mode(706) by limitation of a transfer number, SDU discard mode by timer end(707), and a no-discard mode(708) according to a discard condition(705). In case of setting of the SDU discard modes(706,707), when an SDU discard condition arises, the SDU is discarded and an MRW command is transferred to a receive side. In the case of the no-discard mode(708), when an SDU discard condition arises, initialization information instead of the MRS command is transferred to reset the RLC layer(710). When the RLC acknowledge mode operates at the no-discard mode, if RLC SDU is not transferred during a long time, the RLC layer is reset(710).

Description

Data transmission method of a radio link control layer {Transport method for data of radio link control layer}

The present invention relates to data retransmission of a radio link control layer and a structure of a transmission information message for supporting the same in a radio link control layer in a wireless communication system.

In detail, the present invention provides data transmission of the radio link control layer according to a predetermined operation mode of the radio link control layer when transmission and retransmission fail when providing a service requiring lossless data transmission to an upper layer. The data of the radio link control layer is changed to facilitate the retransmission of the data in the radio link control layer of the radio communication system by simplifying the structure of the information message for transmitting the retransmission information to the receiving side. It relates to a transmission method.

In order to prepare detailed specifications such as 3rd generation GSM network and W-CDMA access technology and terminals based on them, ETSI of Europe, ARIB / TTC of Japan, T1 of USA and TTA of Korea are third generation joint projects (Third Generation). Partnership Project (hereinafter abbreviated as 3GPP) is a project that is developing mobile communication system that can provide multimedia service such as voice, video and data in wireless environment through this joint project.

3GPP supports the activities of five Technical Specification Groups (hereinafter abbreviated as TSG) for fast and efficient project operation and technology development, and each TSG has a set of standards related to the assigned area. Responsible for development, approval, and management. Among them, the Radio Access Network (hereinafter, abbreviated as RAN) group aims to define a new radio access network in a third generation mobile communication system, and includes a terminal and a UMTS wireless terrestrial radio access network; Develop specifications for the functionality, requirements and interfaces of the UTRAN.

The TSG-RAN Group consists of a Plenary Group and four Working Groups. Working Group 1 (WG1) develops standards for the physical layer (first layer), while the second working group (WG2) is the data link layer (second layer) and network layer (third layer). Define the role of In addition, the third operation group (WG3) determines the standards for the interface between the base station, the radio network controller (hereinafter, abbreviated as RNC) and the core network in the UTRAN, and the fourth operation group (WG4). In this section, requirements for radio link performance and requirements for radio resource management are discussed.

1 is a wireless communication system showing the structure of a 3GPP UTRAN.

Referring to FIG. 1, the UTRAN is composed of one or more Radio Network Sub-systems (hereinafter referred to as RNS) 100, and each RNS 100 has one radio network controller (RNC: Radio). Network Controller 101 and one or more Node Bs 102.

In addition, the wireless network controller 101 is connected to a mobile switching center (MSC) 201 located in the core network 200 for circuit-switched communication with the GSM network, and with a general packet radio service (GPRS) network. Is connected with a Serving GPRS Support Node (SGSN) 202 for packet switched communication.

Each Node B 102 is managed by a corresponding RNC 101 and receives information sent from the physical layer of the UE 300 as an uplink and downlinks. The role serves as an access point of the UTRAN for transmitting data to the terminal 300.

The radio network controller 101 is responsible for the allocation and management of radio resources. The radio network controller 101, which is in charge of the direct management of the Node Bs 102 and 103, is called a control RNC (ControlRNC). It is in charge of management. In addition, a radio network controller that manages dedicated radio resources allocated to each terminal is called a serving RNC.

Here, the control RNC and the responsible RNC may be the same, but when the terminal 300 moves out of the area of the responsible RNC to the area of another RNC, the control RNC and the responsible RNC may be different. In addition, the RNS in which the responsible RNC is located is called a responsible RNS.

2 shows a structure of a radio interface protocol according to the 3GPP radio access network standard.

The air interface protocol between the user equipment and the UTRAN consists of a physical layer, a data link layer, and a network layer horizontally, and the protocol structure vertically includes a control plane for transmitting control signals and data information. It is divided into user planes for transmission.

More specifically, the control plane includes a radio resource control layer (hereinafter referred to as "RRC layer") as a third layer, and the second layer includes a radio link control layer (Radio Link Control Layer); Hereafter referred to as "RLC layer" and Medium Access Control Layer (hereinafter referred to as "MAC layer"), the first layer is referred to as physical layer (hereinafter referred to as "PHY layer"). There is).

Meanwhile, in the user plane, a packet data convergence protocol (hereinafter, referred to as PDCP) layer, a second layer include an RLC layer and a MAC layer, and a first layer includes a PHY layer.

The PHY layer provides information transfer service to the upper layer by using various wireless transmission technologies, and is connected to the upper MAC layer through a transport channel, and the MAC layer through the transport channel. Data moves between the physical layer and the physical layer.

These transport channels are divided into a dedicated transport channel and a common transport channel, respectively, depending on whether the terminal can be used exclusively or shared by multiple terminals.

The MAC layer provides reallocation services of radio resources and MAC parameters. This service is performed when the RRC layer requests reallocation of radio resources or requests for MAC parameter change. The MAC layer is connected to the RLC layer through a logical channel, and various logical channels are provided according to the type of information transmitted.

In general, a control channel is used for transmitting control plane information, and a traffic channel is used for transmitting user plane information.

The RLC layer provides a radio link establishment and release service. In addition, it performs a segmentation and concatenation function related to an RLC Service Data Unit (hereinafter, abbreviated as SDU) from an upper layer of the user plane.

The RLC SDU is sized to fit the processing capacity in the RLC layer and then header information is added to the MAC layer in the form of a Protocol Data Unit (hereinafter, abbreviated as PDU). At this time, the RLC layer has an RLC buffer for storing RLC SDUs or RLC PDUs from the upper layer.

The PDCP layer is located above the RLC layer and enables data transmitted through a network protocol such as IPv4 or IPv6 to transmit data in a form suitable for the RLC layer. In addition, to reduce unnecessary control information used in the wired network can be efficiently transmitted over the air interface, it has a header compression (Header Compression) function, it can be used to reduce the amount of header information for TCP / IP.

The RRC layer provides an information broadcast service for broadcasting information to all terminals located in an arbitrary area. It is also responsible for control plane signal processing for control signal exchange in the third layer, and has a function of setting, maintaining, and releasing radio resources between the terminal and the UTRAN.

In particular, the RRC layer has a function of setting, maintaining, and releasing a radio access bearer, and a function of allocating, relocating, or releasing radio resources required for radio resource access. In this case, the radio access carrier means a service provided by the second layer (RLC layer, MAC layer) for data transmission between the terminal and the UTRAN. That is, setting up one radio carrier means a process of defining protocol layer and channel characteristics necessary for providing a specific service and setting each specific parameter and operation method.

In the meantime, the RLC layer will be described in detail as follows.

The RLC layer is divided into three operation modes according to a function to be performed, and each of the RLC layer is a transparent mode, an unacknowledged mode, and an acknowledgment mode.

First, when operating in the transparent mode, no header information is added to the RLC SDU from the upper layer. In general, the transparent mode does not use the division and reassembly of the RLC SDU, but in some cases it is determined whether to use the division and reassembly function when setting the radio access carrier.

Second, in the non-response mode, retransmission is not supported even if the transmission of the RLC PDU fails. Therefore, even if data is lost or a problem occurs during transmission, the receiving side does not require retransmission and discards related data. Services that can use the non-response mode include a cell broadcast service and a voice over IP.

Finally, when the RLC operates in the response mode, retransmission is supported when a packet fails to be transmitted. That is, the transmitting side RLC layer receives the status information from the receiving side to determine the success of the transmission and retransmits the RLC PDU that needs retransmission. In addition, while operating in the response mode, the RLC SDU received from the upper layer by the RLC layer is divided into predetermined sizes by segmentation or concatenation as necessary, and then header information including a sequence number. Is added to become an RLC PDU, and these RLC PDUs are stored in the RLC buffer according to the serial number. The stored RLC PDUs are delivered to the MAC layer as many as required by the MAC layer, and are basically transmitted in the serial number order.

In this way, since the first RLC PDU transmitted from the transmitting RLC layer is transmitted in the order of serial numbers, the receiving RLC layer observes the received serial number and requests retransmission to the transmitting RLC layer for the data that failed to be transmitted. For example, if the serial number of the received RLC PDU was # 23, # 24, # 25, # 32, # 34, the RLC PDU having the serial numbers # 26 to # 31 and # 33 of the RLC PDU was lost during transmission. can do.

Accordingly, the status information of the receiving side buffer transmits a status PDU to the transmitting side, and the transmitting side can know the RLC PDU to be retransmitted and the serial number of the successfully transmitted RLC PDU according to the contents included in the status PDU. .

On the other hand, the transmitter manages various state variables and timers for smooth data transmission. Examples of some state variables are shown in FIG. 3.

The state variable shown in FIG. 3 is a state variable managed by the transmitter, and VT (S) indicates a serial number of a new RLC PDU to be transmitted next among RLC PDUs, and VT (A) is used for sequential transmission. Represents the smallest serial number of the RLC PDU that is expected to receive the next positive response. In addition to these state variables, a counter (VT_DAT) that counts the number of times a particular RLC PDU is sent, a VT_RST that counts the number of times a RESET command has been sent, and a Move Receiving Window (hereinafter referred to as MRW) command There are various sender state variables such as VT_MRW which count the number of transmissions.

On the other hand, there are various state variables related to the transmission of the RLC PDU at the receiving side. In general, their initial value is zero.

In addition, examples of timers used include a timer timer (Timer_Discard) for measuring the time they stay in the RLC layer for each of the RLC SDUs transmitted from the upper layer, an MRW timer (Timer_MRW) which is driven immediately after sending an MRW command, There is an RST timer (Timer_RST) that is driven immediately after the initialization command is transmitted.

At this time, when the discard timer (Timer_Discard) expires, the corresponding RLC SDU is discarded or the RLC layer is initialized, and when the MRW timer (Timer_MRW) and the RST timer (Timer_RST) expire, the same MRW command or initialization command is retransmitted. .

That is, the transmitting side RLC layer of the wireless communication system needs to discard the SDUs in order to prevent the overload of the transmission buffer when the down RLC SDUs are not transmitted to the wireless communication system corresponding to the receiving side.

In general, the RLC layer of the transmitting side and the receiving side has a transmission window and a receiving window, respectively, and the transmitting window indicates a range of RLC PDUs that can be sent at one time from the transmitting side and is within the transmission window. Only PDUs with the corresponding serial numbers can be transmitted. Similarly, the receiving side can receive only the PDU having the corresponding serial number in the receiving window, and immediately discards the PDU having the serial number outside the receiving window.

In the transmitting RLC layer, if a specific SDU is not transmitted smoothly during a predetermined state variable threshold, the transmitting SDU is discarded. However, depending on the mode, the MRW command, which is the information of the closed SDU, is transmitted to the receiving side, and the receiving side receives the MRW command and moves the receiving window.

At this time, as a method of determining that a specific SDU is not smoothly transmitted by the transmitting side, there are two cases by a timer and a transmission frequency.

(A). Method by timer (based on SDU)

When the RLC SDUs are descended from the upper layer to the transmitting RLC layer, a discard timer (Timer_Discard) is driven to measure the time of staying in the RLC layer for each RLC SDU. If the SDU is not successfully transmitted until the time setting of the discard timer expires, all PDUs containing the SDU are discarded and the corresponding MRW command is transmitted to the receiver.

(B). Method by number of transmission (based on PDU)

When the RLC layer operates in the response mode, the RLC SDUs that are sent down to the transmitting RLC layer are converted into RLC PDUs and stored in a buffer. At this time, a state variable counter (VT_DAT) that calculates the number of transmissions for each of the RLC PDUs generated is operated, and is incremented by one each time the corresponding RLC PDU is transmitted. If the counted value of the state variable counter is equal to or larger than the set maximum variable MaxDAT, all the SDUs included in the corresponding PDU are discarded, and the receiving window is moved by sending an MRW command to the receiving side.

In this time-based and transmission-based method, the sender sends an MRW command to the receiver after discarding the SDU. In other words, if it is determined that the data is not transmitted for a long time, the transmitting side transmits an MRW command to the receiving side to move the receiving window, and discards the SDU which is not transmitted for a long time.

In addition to the method of discarding such an SDU, a method of initializing the RLC layer of the transmitting side and the receiving side by performing a reset procedure of the RLC layer at the transmitting side, and then transmitting new data, that is, a novice card ( NO_DISCARD), and the no-card mode does not send an MRW command to the receiving side.

Then, when the RLC layer operates as a NO_DISCARD, if the transmission of a specific SDU is not smoothly transmitted for a long time, the RLC layer may be initialized without transmitting an MRW command.

On the other hand, when the sender sends the discarding information of the SDU to the receiving side, the SDU discarding information is transmitted through a status PDU (Status PDU) for transmitting the control information, "receive window movement," which is one of the information that the status PDU may include (MRW) Super Field "(hereinafter referred to as SUFI).

4 shows the structure of a conventional MRW SUFI.

Referring to FIG. 4, the Type field means that the following information is MRW SUFI, and the LENGTH field indicates the number of discarded SDUs and is represented by 4 bits. SN_MRW _i (i = 1, 2, ..., LENGTH-1, LENGTH) fields are each represented by 12 bits. Since the SN_MRW _i field indicates the serial number of the last PDU among PDUs containing SDUs, the SN_MRW _i field includes all parameters indicating serial numbers of all PDUs indicating the ends of the discarded SDUs.

The N _LENGTH field is represented by 4 bits and indicates the number of SDUs discarded in a PDU having a serial number of SN_MRW _LENGTH . This indicates which SDUs are discarded in a situation where multiple SDUs can be included in one PDU.

The RLC layer receiving the MRW SUFI moves the reception window according to the value of SN_MRW _LENGTH in the MRW SUFI, and sends a response of MRW_ACK in response. That is, part of the discard information is information necessary for moving the reception window on the receiving side, and indicates the position information of the SDU that was finally discarded.

A structure included in the MRW SUFI will be described with reference to FIG. 5 as follows. This shows the MRW SUFI structure that the RLC SDUs delivered to the RLC layer transmit to the receiver when discarding the RLC SDUs due to the expiration of the sender timer or the limit of the number of transmissions.

As shown in (a) of FIG. 5, although the SDU10 to SDU13 are transmitted from the transmitting RLC layer to the receiving side, the SDU10 to SDU13 cannot be successfully transmitted due to loss of or no positive acknowledgment during transmission. Then, the discarding information is loaded on the MRW SUFI as shown in FIG. 5 (b) and transmitted to the receiving side.

In FIG. 5 (b), since MRW SUFI includes location information of each discarded RLC SDU, a total of four RLC SDU information from RLC SDU10 to SDU13 is included, so the value of the LENGTH field is 4, and includes each SDU. Add a SN_MRWi value that indicates the sequence number of the last PDU. Parameters corresponding to the serial number (SN = 1) of PDU 1 indicating the end of SDU10 and SDU11 SN_MRW ₁ = 1 and SN_MRW ₂ = 1 and parameter corresponding to the serial number (SN = 3) of PDU2 indicating the end of SDU12 SN_MRW ₃ = 3 and the parameter SN_MRW = 7 corresponding to the serial number (SN = 7) of the PDU7 indicating the end of SDU13. And since SDU13 is the first SDU discarded in PDU7, N _LENGTH = 1.

After receiving the MRW SUFI, the receiving side transmits the MRW_ACK SUFI as a positive response to the transmitting side, discards the RLC PDUs according to the contents included in the MRW SUFI, and moves the receiving window to the serial number (SN = 7) of the PDU. . Then, the upper layer transfers the information of each discarded RLC SDU at the transmitting side.

On the other hand, when the RLC layer is set to NO_DISCARD and operates, when an SDU is not transmitted for a predetermined threshold value, the RLC layer may be initialized without transmitting an MRW command. The initialization process of is to initialize the transmitting and receiving RLC layer.

The initialization process of the RLC layer is performed when one of the following three conditions is satisfied.

(1) When a protocol error occurs in the RLC layer:

Protocol error when the serial number of the received RLC PDU is out of range of the receiving window or receives conflicting status information for the same RLC PDU, and when a PDU of a different type from the preset PDU structure is received. Assuming that has occurred, perform the initialization process of the RLC layer.

(2) When the number of times of receiving window movement command is equal to or greater than MaxMRW:

When the RLC layer operates in a mode that allows the discarding of SDUs and informs the receiving side of the RLC layer, the MRW command is transmitted. When the MRW command is continuously transmitted, the total number of transmissions is equal to or greater than the maximum variable (MaxMRW). It is assumed that the transmission of the MRW command has failed, and the processing thereof is performed through the initialization of the RLC layer.

(3) When set to NO_DISCARD mode:

When the RLC layer operates in the nodeless mode and the number of transmissions of a specific PDU is equal to or greater than the maximum variable MaxDAT, the RLC layer performs initialization of the RLC layer.

The initialization process of the RLC layer is described in detail as follows.

6A and 6B illustrate an initialization process of a conventional RLC layer of a receiving side and a transmitting side, which is performed by an RLC layer of a receiving side by transmitting a reset information (RESET PDU). Here, an RLC layer for transmitting initialization information is defined as a transmitter and an RLC layer for receiving initialization information is defined as a receiver. In addition, since the RLC layer communicates in both directions, the transmitting side and the receiving side each have a transmitting buffer and a receiving buffer.

Referring to FIG. 6A, when the receiving side RLC layer transmits data (RLC SDU) (S601) and successfully receives initialization information (RESET PDU) transmitted from the transmitting side RLC layer (S602, S603), the receiving side initializes. The process will be carried out.

In the initialization process, the receiving side transmits the initialization response information (RESET ACK PDU) to the transmitting side (S603), and initializes the state variables of the receiving and transmitting buffers that are managed (that is, most of the state variable values are “0”). Set to). In operation S604, the current timers are stopped and all data in the reception buffer is discarded. Also, among the data in the transmission buffer, all data transmitted before the initialization information (RESET PDU) is received are discarded.

Here, the initialization of the state variable and the stopping of the currently running timers in the initialization process are the default values that are basically performed during the initialization.

Then, transmission starts from the data remaining in the transmission buffer (S606). At this time, the RLC PDUs remaining in the transmission buffer after initialization of the RLC layer are allocated by reassigning a serial number from "0". If there is no RLC PDU remaining in the transmission buffer during the initialization process, an additional RLC SDU is received from the upper layer and allocated from the serial number "0".

Similarly, the transmitting side that transmits the initialization information from the receiving side and receives the reset response information (RESET ACK PDU) from the receiving side goes through the process of S611 ~ S616 as shown in Figure 6b.

As described above, in the operation of the conventional RLC layer, when the transmitting side transmits the RLC SDU to the receiving side, and the specific RLC SDU is not transmitted for a long time and the timer expires or the transmission time limit is reached, the corresponding SDU is discarded and the MRW command is sent to the receiving side. Send or perform the initialization of the RLC layer.

However, in the conventional data transmission method as described above, the RLC SDUs descended from the upper layer to the RLC layer may be discarded as described above during the transmission. That is, the upper layer of the receiving side receiving the RLC SDU through the receiving side of the RLC layer causes a problem that some data is lost due to the discarding of the SDU of the RLC layer.

To this end, there is a need for a new mode that can be delivered to the receiver without discarding RLC SDUs from higher layers. This new mode is similar to the conventional "lossy wireless carrier" concept that allows loss of SDUs. Is defined as "Lossless Radio Bearer."

The lossless radio carrier retransmits the RLC SDU without discarding it even if it is not transmitted for a long time, so that there is no discard of the RLC SDU and no MRW instruction is required.

However, if a particular RLC SDU has not been transmitted for a long time, continuous retransmission of the data in the same environment may be caused by a failure in transmission between the sender and the receiver or an error between other RLC layers. Because it can occur, it may not be good in terms of efficiency.

Thus, if a particular RLC SDU is not successfully transmitted for a long time, it is necessary to initialize the transmitting and receiving RLC layers. That is, if the data is not transmitted for a long time and the threshold value based on the timer or the number of transmissions is exceeded, further retransmission is stopped and the initialization information is transmitted to the receiving party for initialization. It receives the data again, converts it into PDUs, and retransmits it.

At this time, the initialization process for the lossless wireless carrier is similar to the case of operating in the NO_DISCARD mode. It is similar to initializing the RLC layer instead of MRW command when data is not transmitted during the reference threshold when operating in nodiscard mode.However, in nodiscard mode, the data transmitted during the initialization process is basically discarded. You will not be able to support the carrier. Therefore, an initialization process is needed to support a lossless wireless carrier.

In addition, in the conventional MRW SUFI which transmits the discard information of the RLC SDU in the lossy wireless carrier, all the SDUs discarded by the transmitter are included. As such, as an example of transmitting all discarded SDU information, an RLC layer may support “Lossless SRNS Relocation (hereinafter abbreviated as LSR) of the PDCP layer.

The LSR is a process of moving all radio resources to the moved RNS for shorter path establishment with the core network when the RNS is different from the responsible RNS after the soft handover of the terminal. The LSR allows PDCP PDUs that were being transmitted through the former Delegate RNS to be transferred to the new Delegated RNC without loss. In order to support LSR, PDCP PDUs are assigned serial numbers similarly to RLC PDUs, and for their management, PDCP layers on the sender and receiver sides are referred to as "Send PDCP Sequence Number (hereinafter referred to as SPSN). ) "And" Receive PDCP Sequence Number (hereinafter abbreviated as RPSN) ".

The SPSN is increased by 1 each time the PDCP sends down one PDCP PDU (= RLC SDU) to the RLC, and the RPSN receives or receives one normal PDCP PDU (= RLC SDU) from the RLC layer. It is incremented by 1 only when the signal indicating that the signal is discarded is received from the RLC layer. Therefore, when the LSR is supported, the SPSN and the RPSN must always be in synchronization with each other. For this purpose, when the transmitting RLC layer discards the RLC SDU received from the PDCP, the receiving RLC layer for each discarded RLC SDU. Send all that information.

In practice, however, PDCPs that support LSRs no longer accept revocation of RLC SDUs. That is, since the operation for the LSR itself does not allow the discard of the RLC SDU, the RLC layer should not discard the RLC SDU as in the prior art.

Therefore, when the PDCP supports the LSR, the RLC layer is set to support a lossless wireless carrier, so that no further RLC SDU discard occurs. In addition, when the RLC layer supports the lossy wireless carrier, it does not support the LSR of the PDCP, and thus it is not necessary to inform the receiving side of all discarded RLC SDU information.

At this time, since transmitting the discarded RLC SDU information only wastes radio resources, the transmitting side only needs to discard the SDU and transmit only the information capable of moving the receiving window to the receiving side.

The information needed to send a command to move the receiving window requires only a serial number indicating where the receiving window is to be moved and some additional information, so that much less capacity can be used than the current MRW SUFI structure. Therefore, when the RLC layer supports a lossless wireless carrier, the conventional MRW SUFI structure transmits information on all discarded SDUs, which wastes a lot of radio resources.

The present invention has been made to solve the above-described problems, the present invention is to provide an operation mode that does not allow the loss of data received from the upper layer in the RLC layer of the operation mode of the RLC layer of the wireless communication system A data transmission method of a radio link control layer is provided.

Another purpose is that the RLC layer supports a mode allowing disallowing the RLC SDU according to the type of service in the automatic retransmission mode and a mode not allowing the RLC layer, and operates the two modes separately. The purpose of the present invention is to provide a data transmission method.

Another object of the present invention is to allow the RLC layer to discard data. The RLC layer allows the data to be discarded by the number of transmissions, the timer expiration, and the no-card. In addition, it is an object of the present invention to provide a data transmission method of the radio link control layer to transmit data discard information indicating only the position information of the last discarded data in the data discard mode.

Another object of the present invention is to provide a data transmission method of a radio link control layer in which an RLC initialization process is performed differently from a nodcard initialization process according to a data transmission delay when the RLC layer is in a mode that does not allow discarding of data. The purpose is to provide.

1 is a structure of UTRAN in 3GPP radio access network standard.

2 is a structure of a general radio interface protocol according to the 3GPP radio access network standard.

3 is a diagram illustrating an example of state variables managed by an RLC layer of a wireless communication system.

4 is a structure of an MRW instruction in an RLC layer of a conventional wireless communication system.

FIG. 5A is a diagram for illustrating an example of a SDU discard method for discarded SDUs in an RLC layer of a conventional wireless communication system. FIG.

FIG. 5B is a diagram illustrating the format and parameters of the MRW SUFI representing the discard information in FIG. 5A.

6A is a flowchart illustrating a receiving side RLC layer reset procedure of a conventional wireless communication system.

6B is a flowchart illustrating a transmitting side RLC layer reset procedure of a conventional wireless communication system.

7 is a diagram illustrating an RLC layer operation mode of a wireless communication system according to an embodiment of the present invention.

8 is a flowchart illustrating a receiving side RLC layer initialization process of a wireless communication system according to an exemplary embodiment of the present invention.

9 is a flowchart illustrating a process of initializing a transmitting side RLC layer of a wireless communication system according to an exemplary embodiment of the present invention.

10 is a structure of MRW SUFI showing the diskette information according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100 ... RNS101 ... Wireless Network Controller

102 Node B 200 Core Network

201 ... MSC202 ... SGSN

300 ... terminal

In order to achieve the above object, the data retransmission method of the radio link control layer according to the present invention,

The radio link control layer of the transmitting side of the wireless communication system that transmits data to the receiving side, receives the data transmission acknowledgment, and retransmits the data, supports a mode allowing data to be discarded and a mode not allowing data to be discarded. It features.

Preferably, the transmitting side radio link control layer is characterized in that the operation is divided into a mode that allows discarding data and a mode that does not allow discarding.

Preferably, when setting the transmitting-side radio link control layer, a specific indicator for setting each mode is set according to whether to discard data, and an operation mode of the radio link control layer is set according to the command of the indicator. It is done.

Preferably, when the radio link control layer operates in a mode that permits discarding of data, and when the transmitting and receiving RLC layers need to be initialized in the mode operation, the data transmitted before initialization is deleted from the data in the transmission buffer. It is characterized by deleting all data in the transmission buffer.

Preferably, when deleting the data transmitted before the initialization process among the data in the transmission buffer, receiving new data from the transmission or higher layer from the remaining data according to the presence or absence of data to be transmitted in the transmission buffer after initialization to the receiving side. Characterized in that the transmission.

Preferably, when the radio link control layer operates in a mode that does not allow discard, and when the transmitting side and the receiving side RLC layer must be initialized during the mode operation, all data in the transmission buffer is deleted.

Preferably, when all the data in the transmission buffer is deleted, the data to be transmitted to the receiving side after the initialization process receives new data from the upper layer and transmits the new data to the receiving side.

In the mode in which the radio link control layer allows data to be discarded, a mode for notifying the receiving radio link control layer of the SDU information discarded by the transmitting radio link control layer and the initialization information of the radio link control layer without notifying the receiving side. It is characterized by operating in a mode that transmits.

In this case, when setting the radio link control layer, the discarded SDU information is informed to the receiving radio link control layer and a mode indicator for setting a non-notifying mode is provided, and the operation mode of the radio link control layer according to the command of the indicator. Characterized in that set.

Preferably, when the radio link control layer operates in a mode, the discard information of the discarded data includes only position information of the last discarded data among a plurality of discarded data in the transmitting link radio layer. .

Preferably, the data is a service data unit (SDU), the radio transmission is made in the PDU state in the radio link control layer, the discard information of the discarded SDU is through the receive window movement superfield (MRW SUFI) in the state PDU Characterized in that the transmission to the receiving side.

Preferably, when transmitting the discarded data information to the receiving side radio link control layer, a first parameter indicating the serial number of the last PDU including the last SDU to be discarded, and the last SDU is the serial number of the first parameter And discarding information including a second parameter indicating the number of SDUs in the PDU having a third parameter and a third parameter indicating whether the discarded last SDU exceeds the moving range of the transmission window.

Herein, the discard information of the data includes a 4-bit type field indicating subsequent information, a 1-bit LENGTH field indicating whether the SDU indicated by the last information discarded by the receiving side exceeds the transmission window. A 12-bit SN_MRW field indicating the last SDU transmitted or the serial number of the last PDU among the discarded SDUs, and a 4-bit N field indicating the number of SDUs from the PDU having the serial number of SN_MRW. It is characterized by including.

In detail, the value of the LENGTH field is set to LENGTH = 0 when the discarded last SDU exceeds the transmission window range, and LENGTH = 1 when not exceeding the transmission window range.

The data transmission method of the radio link control layer according to the present invention will be described below.

7 is a diagram illustrating an RLC layer operation mode of a wireless communication system according to an exemplary embodiment of the present invention, and FIGS. 8 and 9 are flowcharts illustrating a receiving side and a transmitting side RLC layer initialization process of a wireless communication system according to an exemplary embodiment of the present invention. FIG. 10 is a structure of MRW SUFI representing the discard information according to the embodiment of the present invention.

The RLC layer has a transparent mode, an unacknowledged mode, and an acknowledgment mode according to a function to be performed. The present invention provides a response that supports retransmission when a packet fails in the above mode. It operates in mode and includes a mode that does not allow loss of SDU in the RLC layer.

If the RLC layer is a response mode, the mode that does not allow the loss of the SDU in the RLC layer, a mode that does not allow loss in the concept of a wireless carrier is a lossless wireless carrier that is contrary to the concept of a lossy wireless carrier. That is, the lossless radio carrier retransmits the RLC SDU without discarding it even if it is not transmitted for a long time. In addition, since there is no discard of the RLC SDU, the lossless radio carrier no longer needs a receive window shift (MRW) command and does not selectively retransmit data.

Referring to FIG. 7, the acknowledgment mode 701 of the RLC layer checks whether the discard of the RLC SDU is allowed (702), and then allows a discard of the RLC SDU (hereinafter referred to as "disposal allowed mode"). 703 and a mode that does not allow the discard of the RLC SDU (hereinafter referred to as a "non-disposal mode") 704 are supported and operate in two modes.

On the other hand, the discard allowance mode 703 is the SDU discard mode 706 by the limit of the transmission frequency, the SDU discard mode 707 by the timer expiration, in accordance with the discarding conditions such as the criteria to discard and the method of discarding (705), and It is further divided into three modes of the NO_DISCARD mode 708.

In this case, the RLC layer has a mode setting indicator for dividing the operation of the response mode into a discard allow mode and a discard allow mode when setting the RLC layer, and an operation mode of the RLC layer is set according to the command of the mode setting indicator. . In addition, a mode setting indicator for each SDU discard mode and a no-card mode based on time-based and number-of-transmissions in a discard allowance mode is set, and an operation mode of the RLC layer is determined according to the command of the indicator.

The mode setting indicator for setting the operation mode, when the RLC layer is configured for data transmission, the operation mode setting information comes down from the RRC layer to the RLC layer. For example, whether the transparent mode, the non-responsive mode, the response mode, and the size of the window, the timer expiration threshold, etc., the operation mode setting information comes down.

Such a mode setting indicator is transmitted in an RRC message to the terminal when the RLC layer is set in the RRC message. In addition, the criteria for setting the revocation allowance mode and the revocation allowance mode are transmitted through the RRC message when the RLC layer is initially set or reset at the request of a higher layer.

In addition, not only the mode setting indicator of whether to operate in the revocation allowance mode or the revocation allowance mode, but also the mode setting indicator of whether or not to transmit the revocation information. It may be different, and there may be a service that should not discard the SDU among the various services, and if there is a service that does not need to notify the other party when discarding, it can support the appropriate mode for each service.

When the RLC layer operates in the SDU discard mode 706 by limiting the number of transmissions and the SDU discard mode 707 by the timer expiration, these SDUs are discarded and received when a discard condition of the SDU occurs. Send MRW command (MRW SUFI) to the side. In this case, the transmitted MRW command only needs to transmit information necessary for moving the reception window. The MRW information message structure is shown in FIG.

In case of operating in the no-card mode 708, when the SDU discard condition occurs, the initialization information (RESET PDU) is transmitted without transmitting a receiving side MRW command and initialization of the RLC layer is performed (710).

When the RLC response mode operates in the discard allow mode 704, when a specific RLC SDU is not transmitted for a long time, the initialization process 710 of the RLC layer is performed like the node card mode 708. The RLC layer initialization process is different from the initialization process operating in the no-card mode.

Therefore, the initialization process in the RLC layer is performed in the discard allow mode 704 and the no-card mode 708 in the discard allow mode, so that the initialization process in each mode discards all data in the transmission buffer or The data is classified according to whether only the transmitted data is discarded among the data in the transmission buffer. In addition, depending on whether there is data remaining in the transmission buffer, the operation is divided into whether to transmit from the remaining data or to receive and transmit a new RLC SDU from a higher layer.

In detail, the initialization method of the RLC layer according to the mode will be described with reference to FIGS. 8 and 9.

FIG. 8 is a flowchart illustrating a method of initializing a receiving side RLC layer. When the RLC layer operates in a no-use allowance mode, the RLC SDU is not discarded by the initialization process. Therefore, not only the reception buffer but also the RLC PDUs in the transmission buffer are deleted, and the unsent RLC SDUs are received from the upper layer and transmitted to the receiver.

In detail, after transmitting the RLC SDU (S801), the receiving side RLC layer determines whether the initialization information has been successfully received (S802), and when successfully receiving the initialization information, transmits the initialization response information to the transmitting side (S802). S803).

The receiving side RLC layer initializes the state variables of the receiving and transmitting buffers, stops the driving of the currently running timers, and discards all data in the receiving buffer (S804). The RLC SDU is set to the discard non-allowable mode (S805), thereby discarding all data in the transmission buffer (S808). Thereafter, the RLC SDU is received from the upper layer and transmitted to the RLC SDU on the receiving side (S809).

On the contrary, when the reception side RLC layer is set to the discard allow mode, the above-described operation is performed (S801 to S805), the data transmitted in the transmission buffer is discarded (S806), and the data remaining in the transmission buffer is transmitted first. (S807). Of course, there may not be data left in the transmission buffer.

Meanwhile, the transmitting side RLC layer operates as shown in FIG. 9. When the initialization information is transmitted to the transmitting side (S812) and successfully receives the initialization response information (RESET ACK PDU) (S813), the initialization default variables are initialized (eg, , Buffer status variable, timer driving stop), and discards all data in the reception buffer (S815). If the sender RLC layer is set to the SDU discard allow mode, all data in the send buffer is discarded and new data is received and transmitted to the receiver (S818, S819). The data is discarded and data is transmitted from the data remaining in the transmission buffer (S816 and S817).

In addition, when the RLC layer operates in the discard allow mode, an existing initialization method may be used, and an initialization method as shown in FIGS. 8 and 9 may be applied according to the setting mode of the RLC layer. That is, since the discard allow mode is basically a mode in which the RLC layer discards the RLC SDU, there is no significant problem in operation. Therefore, discarding the RLC PDU that is not transmitted in the buffer through the initialization process is not a big problem.

Here, the reference threshold for initializing the transmitting side or the receiving side in a mode that allows discarding of the radio link control layer and a mode that does not allow discarding may be different depending on the mode.

Meanwhile, in the SDU discard mode 707 and 708 due to the limited number of transmissions or the expiration of a timer in the discard allow mode 703, the SDU discard information structure transmitted to the receiving RLC layer when the transmission is delayed is shown in FIG. As shown.

When the SDU discard condition occurs in the RLC layer in the discard allow mode, the SDU is discarded by transmitting the MRW command to the receiving side as shown in FIG. 4 or by transmitting the RESET PDU to initialize the RLC layer. At this time, the transmitted MRW command informs the receiver of the location information of each SDU discarded by the transmitter. The RLC layer supporting the wired wireless carrier no longer sends each RLC SDU discarded by the RLC layer to the receiver. There is no need to inform.

Therefore, when transmitting the MRW command in the RLC layer, only the information necessary for the movement of the receiving side receiving window needs to be transmitted. Therefore, when the RLC layer supports the discard allowance mode and transmits the discard information of the SDU to the receiver by using the MRW command, the content of the MRW command only needs to include location information necessary for the movement of the reception window.

In detail, the RLC layer operates in the discard allow mode and transmits the discarded SDU information to the receiver by using an MRW command. Therefore, only the position of the last SDU to be discarded by the receiver is specified among the SDUs discarded by the transmitter. In other words, it is set in the data discard allowance mode so that the receiver may indicate the serial number of the last PDU and the number of SDUs from the last PDU among the PDUs containing the last SDU to be discarded.

Accordingly, MRW SUFI can be configured as shown in FIG. 10, and MRW SUFI is transmitted as a parameter consisting of only a type field, a LENGTH field, a SN_MRW field, and an N field, and the type field indicates that the information following is MRW SUFI and is expressed in 4 bits. do.

The LENGTH field no longer means the number of discarded SDUs. The LENGTH field is a parameter represented by 1 bit that checks whether the SDU indicated by the last information discarded by the receiver exceeds the transmission window, and is located in the transmission window. Set to "1" and set to "0" when the corresponding PDU exceeds the range of the transmission window.

The SN_MRW field indicates the serial number of the last PDU containing the last transmitted SDU among the discarded SDUs and is represented by 12 bits. The N field indicates the number of SDUs in the PDU having the serial number of SN_MRW and 4 bits. do.

Therefore, since MRW SUFI, which is SDU discard information, is transmitted to the receiving side RLC layer with a total of 21 bits, it can be used using less bits than before.

Therefore, in the data retransmission mode of the RLC layer, when the sender operates in a mode that allows discarding of the RLC SDU and transmits the discarded SDU information to the receiver by using an MRW instruction, the sender discards the discarded SDU information. Only some of the information of the SDUs, particularly the discarding information of the last SDU, is transmitted to the receiving side, and the receiving side needs to move the receiving window according to the discarding information of the SDUs sent from the transmitting side.

In addition, when the sender operates in a mode that does not allow discarding, the sender discards all data of the receiving and transmitting buffers through the initialization process, receives new data, and transmits the data again.

As described above, according to the data transmission method of the radio link control layer according to the present invention, the transmitting side RLC layer supports both a mode that allows the discarding of data and a mode that does not permit the data, thereby transmitting data to the receiving side RLC layer. There is an effect that can solve the problem that occurs when supporting a lossless wireless carrier that transmits without loss.

In addition, the RLC layer allows the discarding of data. The RLC layer is divided into a receive window move command and an initialization mode of the RLC layer according to data discarding conditions. A mode that does not allow discarding of data supports initialization of the RLC layer. By differentiating the initialization operation of the RLC layer in the data discard allowance mode, the RLC layer can support the lossless wireless carrier as well as the lossless wireless carrier without error of the system.

In addition, when it is not necessary to transmit all the information of the SDU discarded by the transmitting side RLC layer to the receiving side, by sending a smaller amount of control signal, it can perform the same role as the conventional method, and limited radio There is an effect that resources can be used efficiently.

Claims (17)

In a wireless communication system that transmits data to a receiving side, receives a data transmission acknowledgment, and retransmits the data, the transmitting radio link control layer supports a mode allowing data to be discarded and a mode that does not allow data to be discarded. A data transmission method of a radio link control layer, characterized in that. The method of claim 1, And transmitting the radio link control layer into a mode that allows discarding of data and a mode that does not allow discarding of data. The method according to claim 1 or 2, When setting the transmitting-side radio link control layer, a mode setting indicator for setting each mode is set according to whether to discard data, and an operation mode of the radio link control layer is set according to the command of the indicator. Data transmission method of a radio link control layer. The method of claim 1, If the radio link control layer operates in a mode that allows data to be discarded, and the transmitting and receiving RLC layers need to be initialized during the mode operation, the data transmitted before the initialization is deleted from the data in the transmission buffer or the data is stored in the transmission buffer. A data transmission method of a radio link control layer, wherein all data are deleted. The method of claim 4, wherein In the case of deleting the data transmitted before the initialization process among the data in the transmission buffer, receiving new data from the remaining data or from the higher layer according to the presence or absence of data to be transmitted in the transmission buffer after initialization and transmitting the new data to the receiving side. A data transmission method of a radio link control layer, characterized in that. The method of claim 1, If the radio link control layer operates in a mode that does not allow discarding and the transmitter and the receiver RLC layers need to be initialized during the mode operation, all data in the transmission buffer is deleted. Data transmission method. The method according to claim 4 or 6, If all data in the transmission buffer is deleted, the data to be transmitted to the receiving side after the initialization process receives the new data from the upper layer and transmits to the receiving side, characterized in that the data transmission method of the radio link control layer. The method of claim 1, The mode in which the radio link control layer allows data to be discarded includes a mode for notifying the receiver radio link control layer of data information discarded at the transmitter radio link control layer, and the radio link control layer without informing the receiver side of the discard information. A data transmission method of a radio link control layer, characterized in that the operation is divided into modes for transmitting the initialization information. The method of claim 8, When setting the radio link control layer, a mode setting indicator for setting a mode for notifying the discarded SDU information to a receiving side radio link control layer and a mode for not informing, and operating mode of the radio link control layer according to the command of the indicator. And a data transmission method of a radio link control layer. The method of claim 8, The data discard information notified to the receiver by the radio link control layer includes only the position information of the last discarded data among a plurality of data discarded at the transmitter radio link control layer. The method of claim 8, The data is a service data unit (SDU), and the radio transmission is performed in a PDU state in a radio link control layer, and the discard information of the discarded SDU is transmitted to a receiver through a reception window moving superfield (MRW SUFI) in a state PDU. A data transmission method of a radio link control layer, characterized in that. The method of claim 8, When transmitting the discarded data information to the receiving side radio link control layer, a first parameter indicating the serial number of the last PDU including the last SDU to be discarded, and the last SDU PDU having the serial number of the first parameter Data of the radio link control layer, characterized in that for transmitting the discarding information including a second parameter indicating the number of SDU in the second parameter and a third parameter indicating whether the discarded last SDU has exceeded the movement range of the transmission window. Transmission method. The method according to claim 10 or 11, wherein The discard information of the data includes a type field indicating subsequent information, a LENGTH field indicating whether data indicated by the last information discarded by the receiver exceeds a transmission window, and a last transmitted one of the discarded SDUs. And an SN_MRW field indicating the serial number of the last PDU or the N field indicating the number of SDUs from the PDU having the serial number of the SN_MRW. The method of claim 13, The LENGTH field is set to LENGTH = 0 when the discarded last SDU exceeds the transmission window range, and LENGTH = 1 when the discarded SDU does not exceed the transmission window range. Method of data transmission. The method of claim 10 or 13, The discard information of the data is a total data transmission method of the radio link control layer, characterized in that 21 bits. The method of claim 10 or 13, The data discard information is transmitted in a structure including a 4-bit type field, a 1-bit LENGTH field, a 12-bit SN_MRW field, and a 4-bit N field. The method of claim 8, And a reference threshold for initializing a transmitting side or a receiving side in a mode that permits discarding of the radio link control layer and a mode that does not permit discarding of the radio link control layer.