KR20020088225A - Transmission method of SDU discard information between data link layers for a radio communications system - Google Patents

Abstract

PURPOSE: A method for transferring a service data unit(SDU) discard information between data link layers in a wireless communication system is provided to play a role equal to the amount of a conventional method by sending a small amount of control signals when a radio link control layer(RLC) of a transmitting end needs not to send all information of discarded SDU to an RLC of a receiving end, thereby efficiently utilizing a restricted wireless resource. CONSTITUTION: A method for transferring an SDU discard information between data link layers in a wireless communication system includes the steps of: transferring all or a portion of SDU information discarded at a transmitting end; and being operated by dividing an A mode and a B mode. The A mode represents that an RLC is capable of transferring all the SDU discarded information generated in a transmitting end to a receiving end and the B mode represents that only the portion of SDU discarded information required to a moving of the receiving window is transferred.

Description

Transmission method of SDU discard information between data link layers for a radio communications system}

The present invention relates to MRW SUFI (Move Receiving Window SUper FIeld), which is used by the sender to inform the receiver after discarding the SDU in the RLC layer of a 3GPP asynchronous (UMTS) mobile communication system. When the transmitting side discards SDUs, information on all discarded SDUs or only information necessary for receiving window movement is loaded into MRW SUFI to reduce radio resources used for sending discarding information. SDU disposal information transmission method.

That is, the present invention relates to a method for transmitting SDU discard information according to a mode of a data link layer in a wireless communication system.

In more detail, the RLC layer is divided into an A mode for transmitting all SDU discarding information generated from a transmitting side to a receiving side, and a B mode for transmitting only some SDU discarding information necessary for movement of a receiving window. It is characterized by putting MRW transmission setting indicator for mode setting of RLC layer. When the RLC layer is operated in A mode, all SDU discard information generated on the transmitting side is transmitted to MRW SUFI, and when operating in B mode, only the position information of the last SDU transmitted among the SDUs discarded by the transmitting side is received. To tell.

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 third-generation mobile communication system that can provide multimedia services such as voice, video and data in a wireless environment.

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 the third generation mobile communication system, and is a terminal (mobile station) and a UMTS wireless network (Universal Mobile Telecommunications Network Terrestrial Radio Access Network). Develop specifications for the functionality, requirements, and interfaces of the UTRAN.

The TSG-RAN Group is again composed of a Plenary Group and four Working Groups. Working Group 1 (WG1) develops standards for the Physical Layer (WG1), while the second Working Group (WG2) works with the Data Link Layer (2nd Layer) and Network Layer (WG2). Role of the third tier). In addition, the third operation group defines standards for interfaces between base stations, radio network controllers (hereinafter referred to as RNCs), and core networks in the UTRAN, and the fourth operation group relates to radio link performance. Discuss requirements and requirements for radio resource management.

Figure 1 shows the structure of the UTRAN. UTRAN 20 is composed of Node B and RNC as shown in FIG. Node B is managed by the RNC and is responsible for the access point of the UTRAN, which receives information from the physical layer of the terminal (mobile station) 10 in uplink and transmits data to the terminal in downlink. . The RNC is responsible for the allocation and management of radio resources. The RNC, which is in charge of Node B's direct management, is called Control RNC and is responsible for the management of public radio resources. A place that manages dedicated radio resources allocated to each terminal is called a serving RNC. The control RNC and the responsible RNC may be the same, but when the UE moves out of the area of the responsible RNC to another RNC, the control RNC and the responsible RNC may be different. The Radio Network Sub-System (hereinafter referred to as RNS) is composed of one RNC and several Node Bs as shown in FIG. In addition, the RNS in which the responsible RNC is located is called the responsible RNS.

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

The radio interface protocol between the user equipment and the UTRAN consists of a physical layer, a data link layer and a network layer horizontally, and vertically transmits a control plane and data information transmission for signaling. It is divided into User Plane.

More specifically, referring to FIG. 2, the control plane includes a Radio Resource Control Layer (hereinafter referred to as RRC), a Radio Link Control Layer (hereinafter referred to as RLC), a medium. Medium Access Control Layer (hereinafter referred to as MAC) and Physical Layer (Physical Layer), the user plane in the packet data convergence protocol (hereinafter referred to as PDCP) layer, RLC layer, There is a MAC layer and a physical layer.

The physical layer provides an information transfer service to an upper layer using various wireless transmission technologies. The upper MAC layer is connected through a transport channel, and data between the MAC layer and the physical layer moves through the transport channel. The transport channel is 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 a reassignment service of MAC parameters for allocating and reallocating radio resources. The RLC layer is connected to a logical channel, and various logical channels are provided according to the type of information to be 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, the RLC performs a segmentation and reassembly function of 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).

The PDCP layer is located above the RLC layer and allows data transmitted through a network protocol such as IPv4 or IPv6 to transmit data in a form suitable for the RLC layer. Also, It reduces unnecessary control information used in the wired network so that it can be efficiently transmitted through the air interface. This feature is called Header Compression and can be used to reduce the amount of header information for TCP / IP as an example.

The RRC provides an information broadcast service that broadcasts information to all terminals located in an arbitrary area. It is also in charge of 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 has a function of setting, maintaining, and releasing a radio bearer, and allocating, relocating, or releasing radio resources required for radio resource access. In this case, the radio bearer refers to a service provided by the second layer for data transmission between the terminal and the UTRAN. That is, one radio bearer is defined as a process of defining the protocol layer and channel characteristics necessary for providing a specific service and setting each specific parameter and operation method.

Hereinafter, the RLC layer will be described in more detail.

The RLC layer has three modes according to a function to be performed, and each of them is a transparent mode, an unacknowledged mode, and an acknowledgment mode.

First, when operating in transparent mode, no header information is added to the RLC SDU from the upper layer. In general, the division and reassembly of the RLC SDU is not used in the transparent mode, but in some cases, the use of the division and reassembly is determined when the radio bearer is configured.

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. Examples of services that can use the non-response mode include a cell broadcast service and a voice over IP.

Finally, when the RLC operates in response mode, it supports retransmission when a packet fails. 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. While operating in the response mode, the RLC SDU received from the upper layer by the RLC layer is made in a payload unit (hereinafter, abbreviated as PU), which is a predefined size by partitioning or concatenation as necessary. Each PU adds header information including serial numbers to form an RLC PDU, which is 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 serial number order. In the transmitting RLC layer, the first RLC PDU transmitted is transmitted in the order of the serial number. Therefore, 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, it can be said that the RLC PDU having the serial numbers of # 26 ~ # 31 and # 33 has been lost. In addition, since the retransmitted RLC PDU has a higher priority than the first RLC PDU transmitted, the transmitting side preferentially transmits the RLC PDU requiring retransmission.

In general, the RLC layer of the transmitting side and the receiving side has a transmission window and a receiving window, respectively. The transmission window means a range of RLC PDUs that can be sent at a time by the transmitter, and only PDUs whose serial number is in the transmission window can be transmitted. Similarly, the receiving side can receive only the PDU whose serial number is in the receiving window, and immediately discards the PDU having the serial number outside the receiving window.

If the RLC SDUs that have descended to the transmitting RLC layer are not properly transmitted to the receiving side, the transmitting side needs to discard them in order to prevent the transmission buffer from being overloaded. The conditions for discarding the SDU by the sender include a timer and a retransmission limit.

Hereinafter, each method of discarding the SDU by the transmitting side will be described.

(1) SDU disposal method by timer

When the RLC SDUs come down to the transmitting RLC layer, Timer_Discard, which is a timer measuring the time spent in the RLC layer, is driven for each RLC SDU. If the SDU is not sent successfully until this timer expires, all PDUs containing the SDU are discarded. However, if an SDU that should not be discarded is in the same PDU as the SDU to be discarded, the PDU is not discarded.

(2) SDU disposal method by the number of retransmission

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, VT (DAT), which is a counter that calculates the number of transmissions of each RLC PDU, is operated. The VT (DAT) is incremented by one each time the responsible RLC PDU is transmitted. However, the number of possible retransmissions is defined by a variable called MaxDAT. If the VT (DAT) value is greater than or equal to MaxDAT, all SDUs including the corresponding PDU are discarded.

The SDU information discarded by the transmitting side by the above method is sent to the receiving side to move the receiving window on the receiving side. This is to ensure that the receiving side no longer receives the discarded SDU. The SDU discard information sent by the sender is transmitted through a status PDU for transmitting control information, and is referred to as a "Move Receiving Window" (hereinafter referred to as MRW), which is one of the information that the status PDU may contain. ) Superfield (hereinafter referred to as SUFI).

3 shows the structure of MRW SUFI. The Type field means that the following information is MRW SUFI, and the LENGTH field (4 bits) indicates the number of SDUs to be discarded. However, if the value of LENGTH is set to "0000", only one SDU is discarded and it means that the serial number of the PDU containing the discarded SDU exceeds the range of the transmission window. The SN_MRW _i field (12 bits) indicates the serial number of the last PDU among the PDUs containing the discarded SDU. The N _LENGTH field (4 bits) indicates up to which SDU the PDU with the serial number of SN_MRW _LENGTH is discarded. This indicates which SDUs are discarded in a situation where several SDUs can be included in one PDU. In exceptional circumstances, if the value of N _LENGTH is set to 0, it is the case that the last SDU to be discarded ends exactly at the PDU with the serial number SN_MRW _LENGTH -1, in which case the value of SN_MRW _LENGTH is transmitted next. Set to the serial number of the PDU to be used. 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.

Let's look at the contents included in the MRW SUFI with reference to FIG. FIG. 4 is an example of a method of discarding an SDU by a timer, and illustrates a situation in which an RLC SDU down to an RLC layer of a transmitter is contained in an RLC PDU and delivered to a receiver. The timer Timer_Discard operates for each SDU from the moment the SDU descends from the upper layer. In FIG. 4, suppose that PDUs PDU0 to PDU3 including SDU0, SDU1, SDU2, and a part of SDU3 are transmitted, but Timer_Discards of SDU0 to SDU3 have expired because they are not lost or acknowledged during transmission.

Therefore, the transmitting side discards SDU0 to SDU3 and sends the MRW SUFI including all the SDU information to be discarded to the receiving side to move the receiving window. As shown in the MRW SUFI example of FIG. 4, since four SDUs must be discarded from SDU0 to SDU3, the value of the LENGTH field is 4, and an SN_MRWi value indicating the last PDU including each SDU is added. At this time, since SDU3 is exactly finished at PDU6, SN_MRW ₄ = 7 and N _LENGTH = 0, respectively.

Meanwhile, in the conventional MRW SUFI, information of all SDUs discarded by the transmitter is included. As an example of transmitting all discarded SDU information, the RLC layer supports "lossless SRNS relocation" (hereinafter referred to 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 similar 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 a "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 one normal PDCP PDU (= RLC SDU) from the RLC layer or the corresponding RLC SDU. Increment by 1 only when receiving the signal from the RLC layer.

Therefore, when the LSR is supported, the SPSN and the RPSN must always be in synchronization with each other. To this end, 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.

However, except for the case in which all SDU information discarded for synchronization of PDCP serial numbers, such as the LSR, needs to be informed, transmitting each discarded SDU information only wastes radio resources. You only need to discard the SDU and send only the information to move the receiving window to the receiving side. The information needed to send a command to move the receiving window requires only a serial number (12 bits) indicating where the receiving window is to be moved and some additional information, so that transmission using a much smaller capacity than the current MRW SUFI structure is possible.

The present invention has been made to solve the waste of radio resources, which is the conventional problem described above, and when the SDU information to be discarded needs to be informed to the receiving side, as in the case of the LSR, the MRW mode setting indicator is used. Accordingly, the RLC layer operates in A mode, which operates to inform all of the discarding information of the RLC SDU generated from the transmitting side, and B mode, which transmits only information necessary for moving the receiving window.

In particular, when the RLC layer operates in the B mode, the transmitting side does not need to inform the SDU of the SDUs to be discarded that are not transmitted to the receiving side. However, the transmitting side only needs to send the receiving window update information in consideration that the SDU information which has already been sent may be stored at the receiving side. Therefore, when operating in the B mode, the information contained in the MRW SUFI proposes a method of notifying only the position information of the last SDU transmitted among the SDU discarded by the sender.

1 is a UTRAN structure according to the 3GPP radio access network standard to which the prior art and the present invention is applied

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

3 is a conventional MRW SUFI structure

4 is an example of a timer-based SDU discard method according to the conventional method

5 is a proposed MRW SUFI structure (method 1)

6 is a proposed MRW SUFI structure (method 2)

In the method for transmitting SDU discard information in a wireless communication system according to the present invention, in the transmission system of a wireless communication for transmitting information of a transmitting side to a receiving side, all or part of SDU information discarded by a transmitting side is transmitted. The RLC layer is characterized in that the operation is divided into the A mode for transmitting all the SDU discard information generated in the transmitting side to the B mode for transmitting only the SDU discard information necessary for the movement of the receiving window.

In addition, in the present invention, the radio transmission is made in the SDU state in the RLC layer, the discard information of the SDU that failed to transmit is characterized in that to transmit to the receiving side through the reception window mobile superfield (MRW SUFI) in the status PDU.

In addition, the present invention is characterized in that when generating the RLC layer for the configuration of the radio bearer, the MRW transmission setting indicator for setting the RLC layer to operate in the A mode or B mode.

In addition, the present invention is characterized in that when the RLC layer operates in A mode, all SDU information discarded at the transmitting side is transmitted to the receiving side through the proposed MRW SUFI.

In addition, when the RLC layer is to operate in B mode and needs to inform the receiving side of the discarded SDU information necessary to move the reception window, only the location information of the last SDU transmitted among the SDUs discarded by the transmitter using the proposed MRW SUFI is proposed. It is characterized by informing the receiving side.

The objects and features according to the present invention will become apparent from the detailed description of the embodiments with reference to the accompanying drawings.

Hereinafter, a method of informing a receiving end of failed transmission data of a transmitter according to the present invention will be described with reference to the accompanying drawings.

When operating in the B mode of the present invention, the following two methods of notifying only the position information of the last SDU transmitted among the SDUs discarded by the transmitter will be described.

First, only part of the conventional MRW SUFI structure is used.

The proposed MRW SUFI is shown in FIG. In the structure of FIG. 5, a field used may vary according to an operation mode of the RLC layer.

If the RLC layer operating in the mode A should inform all the SDU discard information to the receiving side, because all fields _{(LENGTH, SN_MRW 1, SN_MRW 2} , .., SN_MRW LENGTH-1, SN_MRW LENGTH, N LENGTH) of Figure 5 use.

However, if the RLC layer operates in the B mode, only the information necessary for the movement of the reception window needs to be informed to the receiver, and thus only the position of the last SDU transmitted among the discarded SDUs is designated. This location information may indicate the serial number of the last PDU among the PDUs containing the last transmitted SDU and the number of SDUs from the last PDU.

Therefore, only the LENGTH, SN_MRW _{LENGTH, and} N _LENGTH fields are used in the structure of FIG. At this time, since the LENGTH field designates only one SDU, it checks whether one SDU to be discarded exceeds the transmission window. If it is located in the transmission window, it is "0001". If the corresponding PDU is out of the transmission window, "0000" Set to "."

The SN_MRW _LENGTH field indicates the serial number of the last PDU containing the last SDU transmitted among the discarded SDUs, and the N _LENGTH field indicates the number of SDUs of the PDU having the serial number of SN_MRW _LENGTH .

Second, the use of the new MRW instruction structure is described.

It is possible to configure an independent SUFI different from FIG. 5. That is, as shown in FIG. 6, a SUFI named MRW2 is defined to transmit only information necessary for moving the reception window. The MRW2 SUFI of FIG. 6 includes a LENGTH field, an SN_MRW field, and an N field, and these fields include the same contents as the LENGTH, SN_MRW _{LENGTH, and} N _LENGTH fields used when operating in the B mode in the first method.

As described above, in the present invention, in the wireless communication transmission system for transmitting the information of the transmitting side to the receiving side, all or part of the SDU information discarded by the transmitting side is transmitted, and the RLC layer is generated at the transmitting side. SDU discard information transmission between data link layers in a wireless communication system characterized in that the operation is divided into the A mode for transmitting all the SDU discard information to the receiving side and the B mode for transmitting only the SDU discard information necessary for the movement of the receiving window. It is about a method.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments.

Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, in the data transmission method according to the present invention, when it is not necessary to transmit all the information of the SDU discarded by the transmitting RLC to the receiving RLC, a smaller amount of control signal is sent to the conventional method. It allows you to play the same role. Therefore, the radio resource defined by the present invention can be efficiently used.

Claims (6)

In a wireless communication transmission system for transmitting information of a transmitting side to a receiving side, all or part of SDU information discarded by a transmitting side is transmitted, and the RLC layer transmits all SDU discard information generated at the transmitting side to the receiving side. A method for transmitting SDU waste information between data link layers in a wireless communication system, characterized in that the operation is divided into the A mode for transmitting and the B mode for transmitting only the SDU discard information required for the movement of the receiving window. The wireless communication of claim 1, wherein the wireless transmission is performed in an SDU state at the RLC layer, and the discarding information of the SDU that fails to be transmitted is transmitted to a receiving side through a receiving window superfield (MRW SUFI) in a status PDU. SDU waste information transmission between data link layers in system. The data link in the wireless communication system according to claim 1, wherein when generating an RLC layer for setting up a radio bearer, an MRW transmission setting indicator is provided to set the RLC layer to operate in the A mode or the B mode. SDU waste information transmission method between layers. [4] The wireless communication system according to claim 1 or 3, wherein when the RLC layer operates in the A mode, all the SDU information discarded at the transmitting side is informed to the receiving side using the MRW SUFI. Transmission method. The method according to claim 1 or 3, wherein when the RLC layer operates in the B mode, it is necessary to inform the receiving side of the discarded SDU information necessary for moving the receiving window. Notify the receiver of the location information of the last SDU transmitted among the SDUs discarded by the sender using MRW SUFI, or b) Notify another MRW SUFI including only the location information of the last SDU transmitted among the SDUs discarded by the sender. SDU waste information transmission method between data link layers in a wireless communication system, characterized in that. The LENGTH field according to claim 5, wherein a case in which the last SDU transmitted out of the last SDU discarded by the transmitter side exceeds or exceeds the transmission window range is classified into a LENGTH field, and a) LENGTH = 0000 when it exceeds the transmission window range. And b) LENGTH = 0001 if the transmission window does not exceed the transmission window range. SDU waste information transmission method between data link layers in a wireless communication system.