KR20110077745A - Method for synchronous harq in wireless communication system - Google Patents

Method for synchronous harq in wireless communication system Download PDF

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Publication number
KR20110077745A
KR20110077745A KR1020090134395A KR20090134395A KR20110077745A KR 20110077745 A KR20110077745 A KR 20110077745A KR 1020090134395 A KR1020090134395 A KR 1020090134395A KR 20090134395 A KR20090134395 A KR 20090134395A KR 20110077745 A KR20110077745 A KR 20110077745A
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KR
South Korea
Prior art keywords
harq
base station
time
repeater
subframes
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KR1020090134395A
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Korean (ko)
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김상하
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엘지에릭슨 주식회사
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Priority to KR1020090134395A priority Critical patent/KR20110077745A/en
Publication of KR20110077745A publication Critical patent/KR20110077745A/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The present invention relates to a wireless communication system, and more particularly, to a wireless communication system for performing synchronous HARQ communication between a base station and a repeater. In a wireless communication system according to the present invention, a frame having a length equal to the HARQ round-trip time, which is a time difference between the point in time at which the repeater first transmits the HARQ packet to the base station and the point in which the HARQ packet is retransmitted, the frame includes a plurality of subframes. And a MBSFN subframe allocator operative to allocate a multicast broadcast single frequency network (MBSFN) subframe among the plurality of subframes for use in communication between the base station and the repeater. The time interval between two MBSFN subframes is half of the HARQ round trip time.

Description

METHOD FOR SYNCHRONOUS HARQ IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a wireless communication system, and more particularly, to a wireless communication system for performing synchronous HARQ communication between a base station and a repeater.

Recently, communication standards for improving performance in terms of throughput, latency, and coverage in wireless communication systems have been developed. A widely used standard is the Universal Mobile Telecommunications System (UMTS), which was developed as part of the Third Generation (3G) wireless communications system and is maintained by the Third Generation Partnership Project (3GPP). Among them, 3GPP LTE is a communication standard driven by 3GPP to achieve high data rate, low latency, packet optimized system performance and wide coverage in UMTS system.

In LTE mobile communication systems, in order to support higher data rates and expand serviceable coverage, not only a direct communication method between a base station and a terminal but also a signal transmission method using multi-hop has been studied. Multi-hop technology uses a repeater to relay data to reduce path loss, enabling high-speed data communication, and extending service areas by transmitting signals to mobile terminals far from the base station.

In the LTE mobile communication system, a base station performs communication by transmitting a subframe including control information and data signals to a repeater and a terminal. In particular, multicast broadcast single frequency network (MBSFN) subframes are used in the backhaul subframe to prevent self interference and to reduce channel quality indicator (CQI) measurement errors for the mobile station. Can be used for communication with the repeater.

In addition, in the LTE mobile communication system, the base station transmits and receives data according to a repeater and a HARQ scheme. HARQ is a technique of increasing reception success rate by soft-combining retransmitted data without discarding previously received data. Specifically, the HARQ receiving side determines whether there is an error in the received packet and transmits an ACK (positive acknowledgment) signal or a negative acknowledgment (NACK) signal to the transmitting side according to the presence of the error. The transmitter performs retransmission of the HARQ packet or transmission of a new HARQ packet according to the ACK / NACK signal, and the HARQ receiver soft-combines the retransmitted HARQ packet with the previously received HARQ packet to reduce the probability of error occurrence.

In HARQ, there is a synchronous HARQ scheme in which a retransmission for a specific HARQ packet is always performed after a predetermined time elapses from the completion of a previous transmission, and an asynchronous HARQ scheme in which retransmission of a HARQ packet is performed irrespective of the time at which the previous transmission is completed. In general, in the LTE mobile communication system, a synchronous HARQ method is used for data transmission between a base station and a repeater to reduce the burden of control message exchange. However, as described above, since the backhaul subframe used for communication between the base station and the repeater is limited to a predetermined MBSFN subframe to prevent self interference, when using the conventional synchronous HARQ method between the downlink and the uplink When a packet is transmitted and received at regular time intervals, whether or not the subframe at which the packet should be transmitted corresponds to the MBSFN subframe is determined whether transmission is possible in the corresponding subframe. If the frame is not an MBSFN subframe, transmission of the packet should be deferred until the MBSFN subframe becomes available. That is, when the conventional synchronous HARQ method is used, retransmission of data may occur, resulting in a waste of resources and a decrease in throughput. Therefore, there is a need for the development of an optimized synchronous HARQ method that can prevent such inefficient resource utilization and increase the overall processing efficiency of the system.

The present invention proposes an optimized synchronous HARQ method and a transmission / reception method through the same, which can prevent inefficient resource utilization in a wireless communication system and increase processing efficiency of the entire system.

According to an aspect of the present invention, there is provided a wireless communication system for performing synchronous hybrid automatic retransmit request (HARQ) communication between a base station and a repeater. In a wireless communication system according to the present invention, a frame having a length equal to the HARQ round-trip time, which is a time difference between the point in time at which the repeater first transmits the HARQ packet to the base station and the point in which the HARQ packet is retransmitted, the frame includes a plurality of subframes. And a MBSFN subframe allocator operable to allocate two multicast broadcast single frequency network (MBSFN) subframes for use in communication between the base station and the repeater among a plurality of subframes. The time interval between two MBSFN subframes may be half of the HARQ round trip time.

According to an embodiment of the present invention, the time interval between two MBSFN subframes is a time difference between when the base station receives the HARQ packet and when the HARQ acknowledgment packet indicating whether there is an error in the HARQ packet is transmitted to the relay. It may be equal to the HARQ processing time.

According to an embodiment of the present invention, the HARQ round trip time may be 10 ms.

According to an embodiment of the present invention, HARQ processing time may be 5ms.

Through the use of the optimized HARQ method in a wireless communication system, it is possible to induce efficient resource utilization and increase the stability and overall system performance of the system.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following, when it is determined that there is a risk of unnecessarily obscuring the gist of the present invention, a detailed description of already known functions and configurations will be omitted. In addition, it will be understood that the contents described below are only related to one embodiment of the present invention, but the present invention is not limited thereto.

1 is a diagram schematically showing an example of an LTE mobile communication system 100 to which the present invention may be applied.

Specifically, FIG. 1 schematically illustrates the configuration of the LTE mobile communication system 100. As shown, the LTE mobile communication system 100 of FIG. 1 includes a base station 102, repeaters 104a, 104b, 104c and mobile terminals 106a, 106b, 106c. Base station 102 provides a wireless link for repeaters 104a, 104b, 104c and mobile terminals 106a, 106b, 106c in a coverage region or cell where the base station 102 provides network access services. It can provide a communication service.

The repeaters 104a, 104b and 104c may extend the communication coverage area of the LTE system by relaying signals between the base station 102 and the mobile terminals 106a, 106b and 106c. In general, since the base station 102 has a fixed position, the flexibility of the configuration of the wireless communication network is low, and thus, it is difficult to provide an efficient communication service in a wireless environment in which traffic distribution or call demand is severely changed. In order to overcome this drawback, the LTE mobile communication system 100 is a fixed relay node (104a, 104c) fixedly located at one point or a mobile relay (mobile relay) having a mobility mounted on a train or a large bus, etc. By configuring a wireless communication network in a multi-hop manner using the node 104b, the communication service area of the LTE mobile communication system 100 can be expanded and system capacity can be increased.

As shown, the base station 102 transmits data directly or through the repeater 104a to the mobile terminals 106a and 106c included in the communication coverage area of the base station 102, and the communication coverage of the base station 102. The mobile terminal 106b, which is located outside the area and cannot communicate directly, transmits data through the repeater 104c. In addition, the mobile terminal 106b located outside the communication coverage area of the base station 102 cannot directly communicate with the base station 102 due to the limitation of the transmission power, thereby transmitting data to the base station 102 through the repeater 104c. .

Mobile terminals 106a, 106b, 106c may include any type of portable wireless communication device or system, including, for example, a mobile phone, a portable computer with wireless communication capability, a PDA with wireless communication capability, or other device. . 1 also shows that one base station 102 supports only three repeaters 104a, 104b, 104c and three mobile terminals 106a, 106b, 106c, but more base stations 102 It can be appreciated that it can support a larger number of repeaters and mobile terminals.

2 is a diagram illustrating the structure of an exemplary frame 202 that may be used for synchronous HARQ communication between a base station and a repeater in accordance with the present invention.

In FIG. 2, one frame 202 is composed of subframes each having a subframe number (SF #) of 0 to 9. According to an embodiment of the present invention, the base station and the repeater recognizes any given time point by the frame number and the subframe number in the process of performing communication. Also, in FIG. 2, the length of one frame 202 is 10 ms and the length of each subframe is illustrated as 1 ms. However, the present invention is not limited thereto, and the present invention is not limited thereto. Many times can be allocated.

 In one embodiment, as shown in FIG. 2, subframes 204a and 5b 204b are allocated as MBSFN subframes and used as backhaul subframes for communication between the base station and the repeater. In synchronous HARQ communication between a base station and a repeater according to the present invention, one packet transmission and its feedback transmission may be regarded as one transaction. In consideration of the data transmission throughput of the base station and the repeater, it is preferable that a backhaul subframe is allocated so that one transaction can be processed in one frame. The time taken to complete one transaction between the base station and the repeater is called HARQ round trip time. That is, HARQ round trip time refers to the time difference between initial transmission and retransmission of the HARQ packet. This is determined by the HARQ processing time, which is the time difference between the time point at which the receiver receives the signal and the time point at which the received signal is analyzed and the configuration of the packet to be transmitted to the transmitter is completed. For example, the HARQ round trip time may be determined to be twice the HARQ processing time. In the synchronous HARQ communication according to the present invention, the HARQ round-trip time is a time length of one frame 202 to prevent transmission delay that occurs when the subframe at which the packet should be transmitted is not the MSBSFN subframe. That is, 10 ms), the HARQ processing time to be half of that time (that is, 5 ms) and MBSFN subframes should be allocated to have the same time interval as the HARQ processing time. In FIG. 2, for example, subframes 204a and 5b 204b are allocated as MBSFN subframes and used as backhaul subframes, but the present invention is not limited thereto and is equal to the HARQ processing time. Any two subframes having a time interval can be allocated as MBSFN subframes and used as backhaul subframes.

FIG. 3A is a diagram illustrating an exemplary embodiment of forward synchronous HARQ communication in which data is transmitted from a base station to a repeater using the frame 202 structure of FIG. 2.

Specifically, the base station selects MSBSFN subframes 0 and 5 allocated at intervals equal to the HARQ processing time (for example, 5 ms) as a backhaul subframe for communication with the repeater, and the repeater performs the base station during initial startup. It is possible to recognize the backhaul subframe numbers (ie, 0 and 5) selected by. The base station transmits HARQ packet data to the repeater through the data channel of the 0 downlink subframe. If there is an error in the HARQ data packet received from the base station, the repeater transmits a NACK signal to the base station through the control channel of the 5th uplink subframe after HARQ processing time has elapsed from the time when the HARQ data packet is received. The base station receiving the NACK signal from the repeater retransmits the HARQ data packet through the control channel of the downlink subframe 0 after the HARQ processing time elapses again from the reception time. The above process may continue until the base station receives the ACK signal from the repeater.

FIG. 3B is a diagram illustrating an exemplary embodiment of reverse synchronous HARQ communication transmitting data from a repeater to a base station using the frame 202 structure of FIG. 2.

As shown in FIG. 3 (a), the base station selects MSBSFN subframes 0 and 5 allocated at intervals equal to the HARQ processing time (for example, 5 ms) as a backhaul subframe for communication with the repeater. The backhaul subframe number (ie, 0 and 5) selected by the base station may be recognized during the startup process. The base station transmits resource allocation information of a specific frequency band for data packet transmission of the repeater through the control channel of the 0 downlink subframe. The repeater transmits the HARQ data packet through the data channel of the fifth uplink subframe using the allocated resource after the HARQ processing time has elapsed from the time of receiving the resource allocation information from the base station. If there is an error in the HARQ data packet received from the repeater, the base station transmits a NACK signal to the repeater through the control channel of the 0 downlink subframe after the HARQ processing time elapses from the time when the HARQ data packet is received. The repeater, which receives the NACK signal from the base station, retransmits the HARQ data packet through 5 uplink subframes after the HARQ processing time elapses from the reception time. The above process continues until the repeater receives the ACK signal from the base station.

As described above, the downlink subframe having the same two subframe numbers (that is, 0 and 5) as a result of applying the synchronous HARQ method according to the present invention in the communication between the base station and the repeater in the wireless communication system; The uplink subframe may be used as a backhaul subframe for communication between the base station and the repeater. As a result, additional control information for the backhaul subframe allocation and the decoding process for the control information are not required, and retransmission of the HARQ packet is not delayed, thereby increasing the overall processing efficiency of the system.

The blocks shown in the drawings herein can be fully functional and do not require corresponding hardware components to correspond. For example, in one or more embodiments two or more blocks may be implemented in software within a single digital processing device. Digital processing devices may include, for example, general purpose microprocessors, digital signal processors (DSPs), reduced instruction set computers (RISCs), complex instruction set comptuers (CISCs), field programmable gate arrays (FPGS), and application specific integrated circuits (ASICs). And / or the like, including combinations thereof. In addition, the present invention can be implemented using hardware, software, firmware, and combinations thereof.

While the present invention has been described in connection with specific embodiments, those skilled in the art can understand that modifications and variations are possible without departing from the spirit and scope of the invention. Such modifications and variations are to be interpreted as being within the scope of the invention and the appended claims.

1 is a diagram schematically showing a configuration of a general LTE system.

2 illustrates the structure of an exemplary frame that may be used in the synchronous HARQ method according to the present invention.

3 (a) and 3 (b) illustrate an exemplary transmission and reception operation between a base station and a repeater via a synchronous HARQ method according to the present invention.

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

102: base station

104: repeater

106: mobile terminal

202: subframe

204: MBSFN subframe

Claims (4)

A wireless communication system for performing synchronous hybrid automatic retransmit request (HARQ) communication between a base station and a repeater, Configure a frame having a length equal to a HARQ round trip time, which is a time difference between the point in time at which the relay first transmits an HARQ packet to the base station and the point in which the HARQ packet is retransmitted, wherein the frame includes a plurality of subframes A frame configuration unit; And MBSFN subframe allocation unit operable to allocate two multicast broadcast single frequency network (MBSFN) subframes of the plurality of subframes for use in communication between the base station and the repeater. Including, Wherein the time interval between the two MBSFN subframes is half of the HARQ round trip time. The method of claim 1, The time interval between the two MBSFN subframes is HARQ processing time which is a time difference between the time when the base station receives the HARQ packet and the time when the HARQ acknowledgment packet indicating whether there is an error in the HARQ packet to the relay; Same wireless communication system. The method of claim 1, The HARQ round trip time is 10ms. The method of claim 2, The HARQ processing time is 5ms wireless communication system.
KR1020090134395A 2009-12-30 2009-12-30 Method for synchronous harq in wireless communication system KR20110077745A (en)

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