KR20100017045A - Method of transmitting data block in wireless communication system - Google Patents

Abstract

PURPOSE: A data block transmitting method is provided to improve the reliability and overall system performance of wireless communications by efficiently operating ARQ(Automatic Repeat request). CONSTITUTION: A base station generates a first lower data block including a first sub header for the upper block and a upper block(S110). The base station transmits a first lower data block to a terminal(S120). The terminal transmits a first ARQ feedback message for the upper block to the base station(S130). The base station generates a second lower data block including a second sub header for the upper block and the upper block(S140). The base station transmits a second lower data block to the terminal(S150). The terminal transmits the second ARQ feedback message for a upper block retransmitted to the base station(S160).

Description

Data block transmission method in wireless communication system {METHOD OF TRANSMITTING DATA BLOCK IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to wireless communication, and more particularly, to a data block transmission method in a wireless communication system.

Wireless communication systems are widely deployed to provide various kinds of communication services such as voice and data. The purpose of a wireless communication system is to enable a large number of users to communicate reliably regardless of location and mobility. However, a wireless channel is a Doppler due to path loss, noise, fading due to multipath, intersymbol interference (ISI), or mobility of UE. There are non-ideal characteristics such as the Doppler effect. Various techniques have been developed to overcome the non-ideal characteristics of the wireless channel and to improve the reliability of the wireless communication.

There is an automatic repeat request (ARQ) among the techniques for improving the reliability of wireless communication. ARQ is a retransmission of data by the transmitter when data reception at the receiver fails. The receiver may inform the transmitter through a feedback message whether the data reception was successful or failed.

In order to increase the reliability of wireless communication while supporting high-speed data services, the wireless communication process is preferably implemented in a plurality of independent vertical layers rather than one single layer. A plurality of vertical hierarchies is called a protocol stack. The protocol stack may refer to an open system interconnection (OSI) model, which is a model for protocol structures well known in communication systems.

A protocol data unit (hereinafter referred to as PDU) is a block of data that a corresponding layer sends and receives with a peer layer through a lower layer. That is, the layer transfers the protocol data unit to the lower layer or receives from the lower layer. A service data unit (hereinafter referred to as SDU) is a data block that a corresponding layer receives from an upper layer or delivers to an upper layer. The PDU may include at least one SDU (or a fragment of the SDU). In this case, an efficient data block transmission method is problematic in relation to a PDU generation method and an ARQ execution method.

An object of the present invention is to provide a data block transmission method in a wireless communication system.

In one aspect, a method of data block transmission in a wireless communication system is provided. The method includes generating a lower data block comprising an upper block which is one of an upper data block and an upper data block and a subheader for the upper block, and transmitting the lower data block.

In another aspect, a method of transmitting an ARQ feedback message in a wireless communication system is provided. The method may further include receiving a lower data block including an upper block which is one of an upper data block and a fragment of the upper data block and a subheader for the upper block, and transmitting an ARQ feedback message for the upper block. Include.

In another aspect, a radio frequency (RF) unit for generating and transmitting a radio signal and an RF block connected to the RF unit may include an upper block, which is one of an upper data block and a fragment of an upper data block, and a subheader for the upper block. It provides an apparatus for wireless communication comprising a processor for generating a lower data block including, and transmitting the lower data block.

Provided is an efficient data block transmission method in a wireless communication system. Thus, overall system performance can be improved.

The following technologies include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier-frequency division multiple access (SC-FDMA), and the like. Such as various wireless communication systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of an Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. IEEE 802.16m is an evolution of IEEE 802.16e.

For clarity, the following description focuses on IEEE 802.16e / IEEE 802.16m, but the inventive concept is not limited thereto.

1 illustrates a wireless communication system.

Referring to FIG. 1, the wireless communication system 10 includes at least one base station 11 (BS). Each base station 11 provides a communication service for a particular geographic area (generally called a cell) 15a, 15b, 15c. The cell can in turn be divided into a number of regions (called sectors). The mobile station (MS) 12 may be fixed or mobile, and may include a user equipment (UE), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA), It may be called other terms such as a wireless modem and a handheld device. The base station 11 generally refers to a fixed station communicating with the terminal 12, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like. have.

Hereinafter, downlink (DL) means communication from the base station to the terminal, and uplink (UL) means communication from the terminal to the base station. In downlink, a transmitter may be part of a base station, and a receiver may be part of a terminal. In uplink, a transmitter may be part of a terminal, and a receiver may be part of a base station.

2 shows an example of a method for performing an automatic repeat request (ARQ). This shows the case where the base station transmits downlink data to the terminal, but may also be applied to the case where the terminal transmits uplink data to the base station.

Referring to Figure 2, the base station transmits an ARQ block to the terminal (S11). The ARQ block is a data unit on which ARQ is performed. The terminal transmits an ARQ feedback message to the base station (S12). The ARQ feedback message includes acknowledgment (ACK) / not acknowledgment (NACK) information for the ARQ block. If the ARQ block is successfully received at the terminal, the ARQ feedback message includes ACK information. If the ARQ block is not successfully received at the terminal, the ARQ feedback message includes NACK information. If the ARQ feedback message includes the NACK information, the base station retransmits the ARQ block to the terminal (S13).

3 is a block diagram illustrating a protocol stack.

Referring to FIG. 3, the protocol stack is composed of a plurality of layers (Layer N-1, N, N + 1). Layer N + 1 is an upper layer of layer N, and layer N-1 is a lower layer of layer N. (lower layer).

A protocol data unit (PDU) is a block of data that a layer sends and receives with a peer layer through a lower layer. That is, the layer transfers the PDU to the lower layer or receives from the lower layer. Hereinafter, a PDU is also called a lower data block. A service data unit (SDU) is a data block that a corresponding layer receives from a higher layer or delivers to a higher layer. Hereinafter, the SDU is also called an upper data block.

Data blocks move between layers through service access points (SAPs). Layer N SAP is an SAP between the N + 1 and Nth layers, and an N-1 layer SAP is between the N and N-1 layers. SAP.

The protocol stack may refer to an open system interconnection (OSI) model, which is a model for protocol structures well known in communication systems. For example, layer N-1 may be a physical layer, layer N may be a medium access control (MAC) layer, and layer N + 1 may be a network layer. The MAC layer performs physical layer control, MAC PDU generation, and ARQ. The physical layer receives the MAC PDU from the MAC layer, generates and transmits a radio signal from the MAC PDU.

Hereinafter, the structure of the PDU and the method of generating the PDU will be described in detail. For example, the PDU may be a MAC PDU and the SDU may be a MAC SDU.

4 shows an example of a PDU structure.

Referring to FIG. 4, the PDU 10 includes a header 11 and a payload 12. The header 11 contains general information of the PDU. The header 11 may include a length of the PDU 10, whether the payload 12 is encrypted, a connection identifier (CID), and packing / fragmentation information of the SDU. have. The CID is an identifier for identifying each connection in the terminal. In IEEE 802.16m, a terminal ID (identifier) for identifying a terminal and a flow ID for distinguishing each connection flow in the terminal are defined. The terminal ID is used for physical layer control signaling, and the header 11 of the PDU 10 may include a flow ID rather than a CID.

Payload 12 includes at least one ARQ block. An ARQ block is an SDU or SDU fragment.

5 shows an example of a PDU generation method.

Referring to FIG. 5, each of the first SDU and the second SDU is virtually fragmented into ARQ blocks according to an ARQ block size value. Each ARQ block is assigned a block sequence number (BSN) in order. Here, the first SDU is fragmented into three ARQ blocks having BSNs of 0, 1, and 2. The second SDU is fragmented into three ARQ blocks with BSNs of 3, 4, and 5.

The ARQ block size value is set by negotiation. The ARQ block size value may be set by exchanging a dynamic service addition request (DSA-REQ) / dynamic service addition response (DSA-RSP) between the base station and the terminal. The DSA-REQ may be transmitted by the base station or the terminal to generate a new service flow. The DSA-RSP is sent in response to the DSA-REQ.

ARQ blocks fragmented according to the ARQ block size value from the SDU are mapped to the payload of the PDU. When the PDU is generated, padding is performed on the remaining space that cannot be mapped because the ARQ block is smaller than the ARQ block size. Here, the payload of the first PDU includes ARQ blocks having BSNs of 0, 1, 2, and 3, and padding is performed in the remaining space. The payload of the second PDU includes ARQ blocks with BSNs of 4 and 5.

If the ARQ block size is large, padding is more likely to occur during PDU generation. This wastes limited radio resources, which can reduce system efficiency. On the contrary, when the ARQ block size value is small, the number of ARQ blocks included in the PDU increases. This allows the ARQ window to quickly advance. The receiver may have a problem of frequently sending an ARQ feedback message. The value of the ARQ block size is known to both the receiver and the transmitter. Therefore, the transmitter signaling the length of the ARQ block to the receiver every time may cause overhead. Subheader management method is required for efficient ARQ performance.

It is not easy to set an appropriate ARQ block size value. In addition, the constant size of the ARQ block makes the use of radio resources inflexible. Therefore, the ARQ block size can be flexibly determined according to a radio resource when generating a PDU.

6 shows another example of a PDU structure.

Referring to FIG. 6, the PDU 100 includes a header 110, a plurality of higher blocks 130-1, 130-2,..., 130 -N, and N are natural numbers, and a subheader 120 corresponding to each higher block. -1,120-2, ..., 120-N). Upper blocks and subheaders correspond one-to-one. The first upper block 130-1 or the Nth upper block 130 -N may be an SDU fragment. The upper block is an SDU or SDU fragment. The SDU fragment is the SDU fragmented during the PDU creation process. When the payload 12 includes a plurality of higher blocks, information for distinguishing each higher block and performing ARQ is required. To this end, the PDU 10 may further include a subheader containing information for identifying each upper block for each upper block.

The structure of the PDU is only an example, and the position of the subheader or the number of subheaders included in the PDU may be variously changed. Here, each subheader is located in front of the corresponding upper block, but this is merely an example. Each subheader may be placed consecutively following the header apart from the corresponding upper block.

7 shows an example of a subheader structure included in a PDU.

Referring to FIG. 7, the subheader 120 includes a sequence number field 121, a fragmentation information field 122, a re-fragmentation information field 123, a length field 124, and an optimized length indicator ( optimized length indicator, 125). Subheader 12 may further include a flow ID. The structure of the subheader is merely an example, and the fields may be omitted in the subheader. The structure of the subheader may vary depending on the corresponding upper block. For example, the 1-bit flag may indicate whether a specific header includes a subheader. For example, if the flag is 0, the specific field may not be included in the subheader. If the flag is 1, the specific field may be included in the subheader.

The sequence number field 121 indicates the sequence number of the corresponding higher block. The sequence number may correspond to the transmission order of higher blocks. Fragmentation information field 122 indicates information about the SDU fragment. The fragmentation information field 122 may explicitly or implicitly indicate whether the upper block is an SDU fragment and the number of fragments of the upper block. The fragmentation information field 122 may be a single field or a complex field composed of a plurality of subfields. For example, the fragmentation information field 122 may explicitly indicate one of no fragment, first fragment of SDU, medium fragment, and last fragment. . For example, when the fragmentation information field 122 indicates an intermediate fragment, it means that the upper block is an intermediate fragment of the SDU. In this case, the fragmentation information field 122 may be a single field of 2 bits. As another example, the fragmentation information field 122 may be a complex field consisting of an offset subfield and a last fragment indicator. The offset subfield indicates how many pieces of the SDU the upper block is. The last fragment indicator indicates whether the upper block is the last fragment in the SDU. The receiver may reconstruct the SDU by placing the SDU fragment using the offset subfield until the last fragment indicator is triggered.

If the initially transmitted SDU fragment included in the PDU is not successfully received at the receiver, the SDU fragment may be included in another PDU and retransmitted. However, if the length of the initially transmitted SDU fragment is different from the length of the retransmitted SDU fragment, additional signaling is required to inform this. The refragmentation information field 123 is used for the case where the length of the initially transmitted SDU fragment and the length of the retransmitted SDU fragment are different. The refragmentation information field 123 may be used in combination with the fragmentation information field 122.

The length field 124 indicates the length of the corresponding higher block. The length may be expressed in units of bits or bytes. The optimized length indicator 125 indicates whether the size of the length field 124 is an optimized length. If the length of the upper block is not long and there is no need to use an unnecessarily long length field, the size of the length field 124 is an optimized length.

Hereinafter, the sequence number field included in the subheader will be described in detail.

The sequence number field indicates the sequence number of the corresponding higher block. However, a sequence number allocation method for SDUs and SDU fragments is problematic.

First, sequence numbers may be allocated for each SDU. In this case, all SDU fragments divided from the same SDU have the same sequence number.

8 shows an example of a PDU generation process.

Referring to FIG. 8, the sequence number of the first SDU is p and the sequence number of the second SDU is p + 1. The first PDU is an upper block and includes the first piece of the first SDU and the second SDU. The second PDU is the upper block and contains the last piece of the second SDU. Both the first piece of the second SDU and the last piece of the second SDU have a sequence number p + 1.

Assume that the receiver succeeds in receiving the first piece of the first SDU and the second SDU but fails in receiving the last piece of the second PDU. The receiver may inform the transmitter of the successful reception of the SDU having the sequence number p and the failure of the reception of the SDU having the sequence number p + 1 through the ARQ feedback message. The transmitter will retransmit the second SDU with sequence number p + 1. In this case, the receiver fails to receive the last piece of the second SDU, but may retransmit the entire second SDU. This results in a waste of limited radio resources. To prevent this, it is necessary to distinguish between SDU fragments divided from the same SDU.

Second, the sequence number may be allocated for each SDU fragment. In this case, all SDU fragments divided from the same SDU have different sequence numbers. If the SDU is not divided, one sequence number is assigned to the SDU. When an SDU is divided into three SDU fragments, three consecutive sequence numbers are assigned to the three SDU fragments in sequence.

9 shows another example of a PDU generation process.

Referring to FIG. 9, the sequence number of the first SDU is p, the sequence number of the first piece of the second SDU is p + 1, and the sequence number of the last piece of the second SDU is p + 2. The first PDU is an upper block and includes the first piece of the first SDU and the second SDU. The second PDU is the upper block and contains the last piece of the second SDU.

Assume that the receiver succeeds in receiving the first piece of the first SDU and the second SDU but fails in receiving the last piece of the second PDU. The receiver may inform the transmitter of the success of reception of the first fragment of the first and second SDUs of sequence numbers p and p + 1 and the failure of reception of the last fragment of the second SDU of sequence number p + 2 through the ARQ feedback message. . The transmitter will retransmit the last piece of the second SDU with sequence number p + 2. In this case, the transmitter may retransmit only the failed SDU fragment to the receiver. Through this, limited radio resources can be efficiently utilized. In addition, ARQ can be efficiently performed. The reliability of the wireless communication can be increased, and the overall system performance can be improved.

As such, the sequence number may be allocated for each SDU or for each SDU fragment. Whether the sequence number is allocated per SDU or SDU fragment is determined by exchanging DSA-REQ / DSA-RSP or SS-basic capability request (SBC-REQ) / SS-basic capability response (SBC-RSP) between the base station and the terminal. Can be set.

10 is a flowchart illustrating a data block transmission method according to an embodiment of the present invention. This is an example of the case where the base station transmits a data block, or may be applied as it is when the terminal transmits the data block.

Referring to FIG. 10, the base station generates a first lower data block including an upper block and a first subheader for the upper block (S110). The upper block is one of an upper data block and a fragment of the upper data block. The base station transmits the first lower data block to the terminal (S120).

The terminal transmits a first ARQ feedback message for an upper block to the base station (S130). The ARQ feedback message may indicate that it is for a higher block by using a sequence number. If the ARQ message indicates a reception failure for the higher block, the base station may retransmit the higher block. To this end, the base station generates a second lower data block including an upper block and a second subheader for the upper block (S140). In this case, the first subheader and the second subheader may include a sequence number field indicating the same sequence number. The terminal transmits a second ARQ feedback message for the upper block retransmitted to the base station (S140).

As such, an efficient data block transmission method can be provided in a wireless communication system. Limited radio resources can be utilized efficiently. In addition, ARQ can be efficiently performed. The reliability of the wireless communication can be increased, and the overall system performance can be improved.

11 is a block diagram illustrating an example of an apparatus for wireless communication. The apparatus 50 for wireless communication may be part of a terminal. The device 50 for wireless communication includes a processor 51, a memory 52, an RF unit 53, a display unit 54, a user interface unit, 55). The RF unit 53 is connected to the processor 51 and transmits and / or receives a radio signal. The memory 52 is connected with the processor 51 to store driving systems, applications, and general files. The display unit 54 displays various information of the terminal, and may use well-known elements such as liquid crystal display (LCD) and organic light emitting diodes (OLED). The user interface unit 55 may be a combination of a well-known user interface such as a keypad or a touch screen. The processor 51 performs all the methods related to data block generation, transmission and ARQ performance described above.

12 is a block diagram illustrating an example of a base station. The base station 60 includes a processor 61, a memory 62, a scheduler 63, and an RF unit 64. The RF unit 64 is connected to the processor 61 and transmits and / or receives a radio signal. The processor 61 may perform all the methods related to data block generation, transmission, and ARQ execution described above. The memory 62 is connected to the processor 61 and stores information processed by the processor 61. The scheduler 63 may be connected to the processor 61 to perform all methods related to scheduling for data block transmission, such as sequence number assignment and subheader management described above.

All the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 illustrates a wireless communication system.

2 shows an example of a method of performing ARQ.

3 is a block diagram illustrating a protocol stack.

4 shows an example of a PDU structure.

5 shows an example of a PDU generation method.

6 shows another example of a PDU structure.

7 shows an example of a subheader structure included in a PDU.

8 shows an example of a PDU generation process.

9 shows another example of a PDU generation process.

10 is a flowchart illustrating a data block transmission method according to an embodiment of the present invention.

11 is a block diagram illustrating an example of an apparatus for wireless communication.

12 is a block diagram illustrating an example of a base station.

Claims (10)

In the data block transmission method in a wireless communication system, Generating a lower data block comprising an upper block which is one of an upper data block and a fragment of the upper data block and a subheader for the upper block; And Transmitting said lower data block. The method of claim 1, And the subheader includes fragmentation information indicating whether the upper block is the upper data block or a fragment of the upper data block. The method of claim 1, Wherein the upper data block is a medium access control (MAC) service data unit (SDU) and the lower data block is a MAC protocol data unit (PDU). The method of claim 1, The subheader may include a sequence number field indicating a sequence number of the upper block. The method of claim 4, wherein The sequence number is characterized in that corresponding to the transmission order of the upper block. The method of claim 1, Receiving an automatic repeat request (ARQ) feedback message for the higher block. The method of claim 6, Wherein the ARQ message indicates a reception failure for the higher block. The method of claim 6, Generating a second lower data block comprising the upper block and a second subheader for the upper block; And Transmitting the second lower data block. In the ARQ feedback message transmission method in a wireless communication system, Receiving a lower data block including an upper block which is one of an upper data block and a fragment of the upper data block and a subheader for the upper block; And Transmitting an ARQ feedback message for the higher block. RF (radio frequency) unit for generating and transmitting a radio signal; And In connection with the RF unit, And a processor configured to generate a lower data block including an upper block which is one of an upper data block and an upper data block and a subheader for the upper block, and to transmit the lower data block. Device for.

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