KR101075613B1 - Method and apparatus for transmitting/receiving flush indication for reordering of data packets in uplink packet data service - Google Patents

Abstract

The present invention relates to an uplink packet data service, and more particularly, to a method and apparatus for smoothly performing realignment in a HARQ scheme. The base station (Node B) transmits a flush indicator together with the packet to the radio network controller (RNC) indicating that more than a predetermined number of uplink packets received from the terminal are discarded continuously. The wireless network controller stores the received packet in the reordering buffer, runs a timer, and performs a reordering operation on the packets stored in the reordering buffer. When the timer expires, packets stored in the reordering buffer containing the received packet are reordered in the order in which they were originally sent and output from the reordering buffer. This invention prevents the malfunction of packet reordering that can occur in the radio network controller.

EUDCH (Enhanced dedicated channel), reordering, MAC-e, HARQ

Description

METHOD AND APPARATUS FOR TRANSMITTING / RECEIVING FLUSH INDICATION FOR REORDERING OF DATA PACKETS IN UPLINK PACKET DATA SERVICE}             

1 is a diagram illustrating a protocol structure of a mobile communication system supporting E-DCH.

2 is a diagram illustrating the operation of the MAC-e structure and HARQ of the terminal.

3 is a structural diagram of a terminal and a network to which a preferred embodiment of the present invention is applied;

4 shows an example of packets delivered from the Node Bs to the RNC in a soft handover situation.

5 is a flow diagram illustrating operation of Node B in accordance with a preferred embodiment of the present invention.

6 illustrates a transmission format of an event A occurrence indicator transmitted with a MAC-e PDU.

7 is a flowchart illustrating the operation of a serving RNC in accordance with a preferred embodiment of the present invention.

The present invention relates to an uplink packet data service using an enhanced uplink dedicated channel (hereinafter, referred to as "E-DCH"), and in particular, to a hybrid automatic retransmission request (HARQ). Reordering in the technique (hereinafter referred to as reordering) is performed smoothly.

Third, based on the European mobile system Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), using a wideband Code Division Multiple Access (CDMA) technology The Universal Mobile Telecommunication Service (UMTS) system, a generational mobile communication system, also known as a Wideband Code Division Multiple Access (WCDMA) system, is designed to provide packet-based text, digitized voice or video, It provides a consistent service that can transmit multimedia data at high speed of 2 Mbps or more. UMTS uses the concept of virtual access, which is a packet-switched connection that uses a packet protocol such as Internet Protocol (IP), and can always be connected to any other end in the network.

The WCDMA system uses an enhanced uplink dedicated channel (E-DCH) to improve the performance of packet transmission in uplink communication in an asynchronous code division multiple access communication system. E-DCH maximizes the efficiency of uplink transmission by using fast scheduling and HARQ.                         

In the fast scheduling scheme, a base station, that is, a Node B, reports a channel state and a buffer state of a user equipment (UE), and controls uplink transmission of UEs based on the received state information. In other words, a large amount of data is transmitted to UEs having a good channel state, and data transmission for UEs having a poor channel state is minimized, thereby enabling efficient use of limited uplink transmission resources. In addition, by performing HARQ between the UE and the Node B, the transmission success rate relative to the transmission output is increased. That is, the UE performs soft combining with the retransmitted data block without discarding the data block in which the error occurs through the HARQ technique, thereby increasing the reception probability of the data block.

1 illustrates a protocol structure of a mobile communication system supporting E-DCH.

Referring to FIG. 1, the UE 405 includes a physical layer 425, a medium access control (MAC) -e layer 420, a MAC-d layer 415, and other upper layers 410. The upper layer 410 includes an application in which actual user data is generated, and a radio link control (RLC) layer for reconfiguring user data to a size suitable for wireless channel transmission. The MAC-d 415 layer plays a role of inserting multiplexing information into data received from the upper layer 410 to form a MAC-d protocol data unit (hereinafter referred to as a 'MAC-d PDU'). do.

The MAC-e layer 420 stores the MAC-d PDU received from the MAC-d layer 415 in a priority queue (hereinafter referred to as 'PQ') (not shown) according to priority. . In addition, the MAC-e layer 420 transmits a buffer status report and a channel quality report to the Node B 430 in consideration of the state of the PQ. The MAC-e layer 420 receives scheduling information, including the maximum allowable transmission rate, transmission timing, and the like, allocated from the Node B 430, and lowers the data stored in the PQ according to the scheduling information. To pass. At this time, the MAC-e layer 420 is an acknowledgment (ACK) signal or a negative acknowledgment signal which is a response signal received from the Node B 430 with respect to the uplink data transmitted to the lower layer 425. HARQ operation is performed in consideration of a non-acknowledge (NACK) signal.

The physical layer 425 processes the data transmitted by the MAC-e layer 420 to be transmitted to the Node B 430 through a wireless channel.

The Node B 430 includes a MAC-e layer 435 and a physical layer 440, and also manages radio resources of the Node B 430 and the UE 405. Layer 1 (Layer 1: L1) / 2 layer (Layer 2: L2) 445 to communicate with 450. The physical layer 440 processes and transmits a signal transmitted through the physical layer 425 of the UE 405 to the MAC-e layer 435.

The MAC-e layer 435 transmits the data transmitted from the physical layer 440 to the L2 / L1 445 and performs an HARQ operation of transmitting an ACK signal or a NACK signal according to whether there is an error of the data. In addition, the MAC-e layer 435 performs scheduling for a plurality of UEs based on the buffer status report and the channel quality report transmitted by the UE 405, and transmits scheduling information to the UEs.

The RNC 450 includes an upper layer 470, a MAC-d layer 465, and a MAC-e layer 460, and an L2 / L1 455 for receiving data transmitted by the Node B 430. It is provided.

The MAC-e layer 460 included in the RNC 450 further includes additional functions that are difficult to provide in the MAC-e layer 435 of the Node B 430. For example, it may be a function of classifying packet data transmitted by a plurality of UEs including the UE 405 by PQ and rearranging the order within the PQ.

As described above, the UE 405 has a PQ and stores data to be transmitted through the E-DCH according to priority. The PQ is configured in the MAC-e layer 420 of the UE 405 when a call of the E-DCH is established, and a plurality of PQs may be configured according to the number of applications to be serviced through the E-DCH.

When the UE 405 performs a buffer status report, the UE 405 notifies the Node B 430 of the total data stored for each PQ, and the Node B 430 includes the UE 405 to the E-DCH. The scheduling is performed in consideration of the channel quality of the UEs performing the service and the priority of the data stored in the PQs.

The operation of the MAC-e structure and HARQ of the terminal will be described with reference to FIG. 2.

As shown, priority buffers (PQs) 505 and HARQ entity 510 are provided in the MAC-e layer of the terminal. The priority butters 505 store the priority butters 505 according to priorities before transmitting the data received from the upper layer. One terminal may have a plurality of PQs, and data having the same priority is stored in one PQ. Priority is typically assigned per logical channel or for multiple logical channels having the same priority. The logical channel is a channel configured between the RLC layer and the MAC layer, and a user application is often mapped to one logical channel. Therefore, one PQ may be connected to one logical channel or multiple logical channels having the same priority.

The HARQ entity 510 controls the operation of HARQ processors 515, 525, 530, 535. The HARQ processors 515 to 535 are responsible for initial transmission / retransmission determination through interpretation of an ACK / NACK signal, and the HARQ entity 510 controls transmission and reception of each HARQ process. The HARQ processors 515 to 535 each have a soft buffer 520 and are responsible for HARQ operation on the wireless channel. HARQ operation is a technique for maximizing retransmission gain by performing retransmission and soft combining on data processed in the physical layer.

In the E-DCH service, the transmitting HARQ processors 515 to 535 transmit data to the receiving HARQ processors 540, 545, 550, and 555 and store the already transmitted data in the soft buffer 520. . Receive side HARQ processors 540 through 555 likewise have a soft buffer for HARQ operation. The receiving HARQ processors 540 to 555 determine whether an error occurs in the received data, and transmits an ACK signal if an error does not occur. The corresponding transmitting HARQ processor that receives the ACK signal discards the data stored in the soft buffer.

On the other hand, if an error occurs in the received data, the receiving HARQ processors (540 to 555) transmits a NACK signal. The corresponding transmitting HARQ processor receiving the NACK signal reconfigures and retransmits the data stored in the soft buffer if necessary. The receiving HARQ processor generating the NACK signal soft-combines the retransmitted data with data stored in its soft buffer, thereby maximizing the retransmission gain.

In the conventional E-DCH service operating as described above, the reordering of packets includes a transmission sequence number (TSN) of the packets and a time stamp (TS) indicating when the packets are first received. It is done using information. The RNC first stores the received packets in order according to the time stamp, and checks whether there is an empty TSN or gap among the stored packets. If there is a gap, the packets before the gap are output in the order in which they were stored.

However, the UE communicates with Node B controlled by another RNC (ie Serving RNC: SRNC) rather than the first RNC (ie, Drift RNC: DRNC) that initiated the call, or two or more nodes controlled by different RNCs. In case of simultaneous communication by the Bs and the soft handover, reordering may not be performed normally due to a delay difference between the Iub interface between the RNC and the Node B and the Iur interface between the RNCs.

For example, if the first node B communicating with the UE continuously flushes more than the maximum number of retransmissions, and the packet transmitted from the second Node B communicating with the UE arrives significantly late in the RNC, the RNC The reordering buffer of may misinterpret the packet from the second Node B to be the same as the packet at the first Node B. Accordingly, there is a need for an efficient method for reordering packets received by an RNC in an E-DCH supporting HARQ in the order in which the UE transmits them.

Accordingly, an object of the present invention, which was devised to solve the problems of the prior art operating as described above, is that the Node B notifies the RNC when a number of flushes consecutively corresponds to the maximum value of the TSN at the Node B. It is to provide a method and apparatus for preventing the malfunction of the rearrangement.

It is another object of the present invention to provide a method and apparatus in which the RNC is informed from the Node B that a number of flushes has occurred in succession corresponding to the maximum number of TSNs.

In order to achieve the above object, an embodiment of the present invention provides a method for transmitting packet discard information for reordering packets in an uplink packet data service, wherein a base station receives packets for an uplink packet data service from a terminal. And determining, by the base station, whether or not more than a predetermined number of packets are consecutively discarded, and if the base station is continuously discarding more than the predetermined number of packets, continuous flushing occurs. And transmitting a flush indicator to the radio network controller.

According to another embodiment of the present invention, in the uplink packet data service, the method for delivering packet discard information for packet reordering may be configured to continuously discard more than a predetermined number of packets received to the base station for uplink packet data service. Receiving a data frame including a first flush indicator and a time stamp of the first received packet after the flush indicator and the predetermined number or more of the packets are successively discarded, and reordering the received packet to the base station. Driving a timer stored in the controller and set to a predetermined value, and when the timer expires, rearranging the packets stored in the reordering buffer including the packets received by the base station in the order in which they were originally transmitted, and outputting them from the reordering buffer. It includes.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

3 illustrates a structure of a terminal and a network to which a preferred embodiment of the present invention is applied.

As shown, the terminal includes a plurality of PQs 720-1, 720-2, and 720-3, and the system includes a plurality of reorder buffers (RQs) 745-1, 745-2, and 745-3. ). PQs 720 store data having the same priority, and RQs 745 rearrange the order of the data having the same priority. PQs 720 and RQs 745 have a one-to-one relationship.

A plurality of RLC entities 705-1, 705-2, 705-3, 705-4, and 705-5 are provided in a terminal, and the RLC entities 705 are control / traffic multiplexers. 710-1, 710-2. The C / T multiplexers 710 correspond to the C / T demultiplexers 750-1 and 750-2 on the receiving side, and the C / T demultiplexers 750 receive from the RQs 745. Insert multiplexing information called a C / T field into the data packet so that the data packets can be delivered to the appropriate RLC entities 755-1, 755-2, 755-3, 755-4, 755-5. C / T multiplexers 710 and PQs 720 are connected via PQ dividers 715-1, 715-2. The relationship between the C / T multiplexers 710 and the PQs 720 is determined during the call setup process, and one PQ is not connected to multiple C / T multiplexers.

PQs 720 store data from RLC entities 705 having the same priority. The C / T multiplexers 710 insert the C / T field into the data output from the RLC entities 705, and the PQ dividers 715 refer to the C / T field to refer to the C / T multiplexer. Data from 710 is properly passed to PQs 720. The relationship between the PQs 720 and the RLC entities 705 is determined during the call setup process.

In FIG. 3, three RLC entities 705-1, 705-2, and 705-3 are connected to a first C / T multiplexer 710-1 and two RLC entities 705-4, 705- 5) is connected to the second C / T multiplexer 710-2. The data output from the RLC entities 705-1, 705-2, and 705-3 are PQs 720-1 according to the priority of the RLC entities 705-1, 705-2, and 705-3. , 720-2). Since the RLC entities 705-4 and 705-5 have the same priority, the RLC entities 705-4 and 705-5 are connected to one PQ 720-3.

The data packets stored in the PQs 720 are delivered to the HARQ entity 725, and the HARQ entity 725 is transferred to the HARQ entity 735 of the Node B according to the HARQ operation. The HARQ entity 725 performs parallel HARQ operation by HARQ processors (not shown). Data transmitted and received between the HARQ entities 725 and 735 is called a MAC-e Protocol Data Unit (PDU).

The MAC-d PDUs stored in the PQs 720 are stored in the MAC-e PDU 730, and the identifier of the PQ to which the corresponding MAC-d PDUs belong is included in the header of the MAC-e PDU. id) and a Transmission Sequence Number (TSN) to be used for reordering the MAC-e PDUs, a Size Index (SID) indicating the size of the corresponding MAC-d PDUs, and a corresponding MAC-d PDU. Number information N and the like are stored.

When the HARQ entity 735 of Node B successfully receives the MAC-e PDU, it forwards the MAC-e PDU to the RNC's Reordering Queue Distributor 740 via the Iub interface. In this case, the HARQ entity 735 attaches a TS to the MAC-e PDU.

The reorder buffer distributor 740 refers to the PQ id of the MAC-e PDU, and transfers the MAC-e PDU to one of the RQs 745. The RQs 745 rearrange the order based on the TSNs and TSs of the MAC-e PDUs delivered from the reorder buffer distributor 740. The reordered MAC-e PDUs are divided into MAC-d PDUs and delivered to the C / T demultiplexers 750-1 and 750-2, and the C / T demultiplexer 750 receives the MAC-d PDUs. The RLC entities 755-1, 755-2, 755-3, 755-4, and 755-5 are properly transmitted based on the C / T field.

4 shows an example of packets delivered from the Node Bs to the RNC in a soft handover situation. Here, two bits of TSN are used, which can have values from 1 to 4.

Referring to FIG. 4, when the UE 810 transmits MAC-e PDUs through an E-DCH, the Node Bs 820 and 830 communicating with the UE 810 may receive the MAC-e PDUs and include reorder buffers. To the RNC 840. Here, the first Node B (Node B 1) 820 correctly receives the first PDU 821, then loses 4 PDUs 822 to 825 consecutively and correctly receives the last PDU 826. The second Node B 2 830 also correctly received the second PDU 832. However, the second PDU 832 from the second Node B 830 has reached the RNC 840 later than the last PDU 826 of the first Node B 820 because of the Iub / Iur delay. For example, this situation is when the first Node B 820 is directly connected to the RNC 840 and the second Node B 830 is connected to the RNC 840 via a serving RNC (not shown). This can happen.

When the RNC 840 first receives the PDU 826, the TSN value of the PDU 826 is 2, and n + 5 is greater than the time stamp value n of the PDU 821 previously received. In fact, the PDU 826 is misunderstood as the desired second PDU 822.

As described above, if a soft handover occurs, the number of flushes that occur more than the maximum number of times that the TSN can have in one node B continuously, and if the packet transmitted from the other node B arrives significantly late in the RNC, the reordering buffer May misunderstand the received packet as another packet.

According to a preferred embodiment of the present invention for solving the above problem, when using k-bit TSN and ^2k flushes occur continuously, Node B informs the RNC of the indication information indicating the situation, and the RNC When receiving the indication information, the timer is started to buffer the received packets until a certain time elapses.

In the example of FIG. 4, the first Node B 820 communicates with the PDU 826 to the RNC 840 an indication that the flush has occurred four consecutive times. Receiving the indication information, the RNC 840 drives a predetermined timer to wait for the next PDU 832 from the second Node B 830 instead of directly delivering the PDU 826 to the higher system. When the timer expires, the PDUs having completed the reordering of the reordering buffer are delivered to the upper system.

In order to facilitate the explanation of the present invention, the following event A is defined.

Event A refers to a situation in which packets are discarded as many times as a malfunction may occur in the rearrangement by the TSN. That is, the number of retransmissions exceeds a predetermined maximum number of retransmissions or a situation in which the event of discarding the packet occurs ^2k consecutively due to the interruption of the HARQ operation due to the flush command of the UE. Where k is the number of bits used for the TSN.

5 is a flowchart illustrating the operation of a Node B according to a preferred embodiment of the present invention. First, Node B continuously receives a plurality of packets from a terminal and checks TSNs and time stamps of the packets to determine whether the event A has occurred.

As shown, when event A occurs in step 900, in step 910, node B transmits an 'event A occurrence indicator' to the serving RNC (SRNC) together with the packet that generated the event A. In this case, the packet generating the event A refers to a packet first received after ^2k or more packets are discarded continuously.

6 shows a transmission format of an event A occurrence indicator transmitted with a MAC-e PDU.

As shown, the event A occurrence indicator is sent to the RNC in a Iub / Iur data frame with a time stamp and a MAC-e PDU. Herein, as an example of a bit of an event A occurrence indicator, a flush indicator is illustrated.

7 is a flowchart illustrating the operation of a serving RNC according to a preferred embodiment of the present invention.

As shown, in step 950 the serving RNC receives an event A occurrence indicator with a packet of TSN = x. The SRNC then drives a timer T set to a predetermined value for the packet in step 960 and continues to reorder within the reorder buffer without delivering the packet with TSN = x to the upper layer until the timer T expires. . When the timer T expires in step 970, the packet with TSN = x is output from the reordering buffer and delivered to the higher layer. The timer is appropriately selected according to the delay of the Iub / Iur interface.

Referring to the example of FIG. 4 mentioned above, preferably, the packet 826 from the first Node B 820 is RNC until at least packets 832 to 835 from the second Node B are received. 840 is left in the reorder buffer. Until the timer for the packet 826 expires, the RNC 840 includes the packets 826 from the first Node B 820 and the packets 832-835 from the second Node B. Do the work. When the timer expires, the packets 826, 832 through 835 are output from the reorder buffer according to the order in which they were originally transmitted, 832, 833, 834, 835, 826.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative of the disclosed invention are briefly described as follows.

According to the present invention, in soft handover, when a flush occurs more than the maximum number of times that a TSN can have in one Node B, and a packet transmitted from another Node B arrives significantly late in the RNC, the RNC reordering buffer. Solves the problem of misinterpreting packets. This invention has the effect of preventing the error of packet data in the higher-level system by avoiding the rearrangement malfunction.

Claims (7)

A method for delivering packet discard information for reordering packets in an uplink packet data service, Receiving, by the base station, packets for uplink packet data service from the terminal; Determining, by the base station, whether more than a predetermined number of packets among the received packets are continuously discarded; And transmitting, by the base station, a flush indicator indicating that a continuous flush has occurred, to the radio network controller, if more than the predetermined number of packets have been discarded continuously. The method of claim 1, wherein the determining is performed. And determining a transmission serial number (TSN) included in the received packets and a time stamp indicating a time at which the received packets are received. The method according to claim 2, wherein the predetermined number is And discards the packet discard information corresponding to the maximum value of the transmission serial number. The method of claim 1, wherein the transmitting of the And transmitting the flush indicator to the radio network controller together with the first received packet and the time stamp of the first received packet after the predetermined number of packets are continuously discarded. A method for delivering packet discard information for reordering packets in an uplink packet data service, A flush indicator indicating that more than a predetermined number of packets received to the base station for uplink packet data service are continuously discarded, and a packet first received after the predetermined number or more packets are successively discarded and the first received. Receiving a data frame including a timestamp of the dropped packet, Storing a packet received by the base station in a reordering buffer and driving a timer set to a predetermined value; And when the timer expires, reordering the packets stored in the reordering buffer including the packets received by the base station in the order in which they were originally transmitted, and outputting them from the reordering buffer. The method of claim 5, wherein the reordering process, And reorder packets stored in the reordering buffer with reference to a transmission serial number (TSN) of the packets stored in the reordering buffer and a time stamp indicating a time at which the packets are received by the base station. The method according to claim 6, wherein the predetermined number is And discards the packet discard information corresponding to the maximum value of the transmission serial number.

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