KR100668666B1 - Method for access point traffic processing in harq mobile communication system - Google Patents

Abstract

A method for access point traffic processing in a HARQ(Hybrid Auto Repeat reQuest) mobile communication system is provided to support an HARQ operation by performing a resource management operation and a transmission control operation in a base station scheduling process. A frame synchronization process is managed to perform a clock synchronization process when a clock for synchronizing a downstream traffic is lost. A scheduling process for the downstream traffic is performed. The downstream traffic is transmitted to a user terminal by performing a wireless band allocation process for transmitting the downstream traffic data to the user terminal and a resource allocation process for hybrid auto-retransmission. Data for upstream are processed and a response for hybrid auto-retransmission is processed.

Description

A method for processing base station traffic in a mobile Internet system supporting hybrid automatic retransmission {Method for access point traffic processing in HARQ mobile communication system}

1 is a structural diagram of a radio frame of a portable Internet system.

2 is a diagram illustrating HARQ operation in a portable Internet system.

3 is a schematic structural diagram of a portable internet system according to an embodiment of the present invention.

4 is an operation diagram of a base station in a portable Internet system according to an embodiment of the present invention.

5 is a downlink scheduling structure considering HARQ according to an embodiment of the present invention.

6 is a flowchart of a downlink scheduling considering HARQ according to an embodiment of the present invention.

7 is a flowchart illustrating HARQ ACK / NAK processing according to an embodiment of the present invention.

8 is a flowchart of a frame synchronization maintaining procedure during downlink scheduling according to an embodiment of the present invention.

The present invention relates to a base station traffic processing method in a portable Internet system supporting hybrid automatic retransmission, and more particularly, to a base station traffic processing method capable of supporting HARQ when scheduling a base station for traffic processing.

Wireless Broadband (WiBro) based on the IEEE 802.16 Wireless Metropolitan Area Network (WiBro) uses various types of IP provided by the wired Internet by using a wireless transmission technology that guarantees spectrum usage efficiency in the 2.3 GHz frequency band. It is a 3.5 generation mobile communication system that provides video and high-speed packet data transmission of based wireless data services (e.g., streaming video, FTP, mail, chat, etc.).

Such a portable Internet system is called an access terminal, an access point supporting wireless access and network connection of a terminal, and a packet access router (hereinafter referred to as a packet access router) that performs mobility control and packet routing functions of each terminal. Refer to).

The portable Internet system performs data transmission / reception on a frame-by-frame basis to support high-speed packet data transmission in a wireless section, and operates based on an OFDM / FDMA / TDD wireless transmission scheme. In the portable Internet system, the OFDM / FDMA / TDD wireless transmission method transmits and receives data in subchannel units composed of subcarrier groups, and transmits a MAP message including frame configuration information at the beginning of each frame. A data burst is sent. The radio frame structure of data transmitted and received in the portable Internet system will be described in detail with reference to FIG. 1.

1 is a structural diagram of a radio frame of a portable Internet system.

Referring to FIG. 1, a portable internet system is generally divided into a downward section and an upward section. The base station (FIGS. 2, 100 and 100 ') transmits data to be transmitted to the terminal (FIG. 2) 200 through the downlink data section among the down sections, and each terminal 200 transmits each downlink data section. Through the map data transmitted at the beginning of the data, the data corresponding to itself can be identified and received. Accordingly, the scheduler performing radio management allocates or manages a subchannel required for transmission of each user data every frame, and forms a map message based on the information.

Even in the case of the uplink which wants to transmit data from the terminal 200 to the base station 100, the terminal 100 checks whether there is a bandwidth (also referred to as bandwidth, or radio resource) allocated to itself using the map data. If there is an allocated bandwidth, the data frame may be transmitted to the base station 100 in the allocated section. In this case, the entire data frame period divided into the downlink data section 10 and the uplink data section 20 is set to be longer than the uplink data section 20 due to the asymmetry of general web data. It can be seen that.

In a portable Internet system, a hybrid auto repeat request (HARQ) is used to increase transmission efficiency, that is, transmission throughput, in a wireless channel in which channel conditions are severely changed and traffic channels for different kinds of services coexist. Automatic retransmission). HARQ is a technology that combines ARQ and forward error correction, and improves throughput and reliability in data transmission in systems that prepare packet data services with burst characteristics such as wireless internet packets. It is a way to improve. An operation procedure of HARQ in the portable Internet system will be described with reference to the HARQ operation diagram in the portable Internet system of FIG. 2.

Referring to FIG. 2, one frame is divided into a downlink and an uplink, and map data is included in the front end of each frame. The data burst to be transmitted by the transmitter is encoded during the downlink period.

After that, one subpacket of a plurality of subpackets generated by dividing a bit stream is transmitted, and a receiver corrects an error of received data within a limit that can be corrected, and falls outside the receiver's error correction capability. Resend the transmitter. The transmitter that is requested to retransmit adjusts the modulation and coding level (MCS) level, which is a level for a predefined modulation and channel coding combination, transmits another subpacket, and adjusts the MCS level to perform retransmission for the data requested to be retransmitted. Perform.

In the case of downlink HARQ, the retransmission request from the receiver is transmitted through an encoded signal of HARQ ACK channel interval. For data burst delivery in HARQ mode, the channel identifier (ACID), which allows other data bursts to be transmitted before waiting for the HARQ response, the subpacket identifier (SP_ID) indicating the order of the subpackets, and the sequence that is toggled each time a new coded packet is sent Identifier (AI_SN: ARQ Identifier Sequence Number) information is added to the burst allocation information.

In order to drive HARQ in the portable Internet system, in addition to the operation of the physical layer for HARQ processing, additional consideration is required in the base station traffic processing apparatus. This is because radio resource management in the frame is performed by the scheduler in the base station traffic processing apparatus, and information about this is transmitted through a map message. That is, determination of whether to retransmit the HARQ burst and resource management for the retransmission burst should be considered in the scheduler in the base station traffic processing apparatus.

In addition, burst buffer management for burst retransmission should be considered when HARQ burst transmission fails (ie, NAK reception). In addition, if a base station traffic device operating by a clock interrupt fails to perform HARQ response processing due to a clock interrupt fluctuation, a deadlock state in which a data service cannot be maintained and a release of a burst resource waiting for a response is impossible. deadlock) problem.

Accordingly, the present invention is to solve the problems of the prior art as described above, to manage the radio resources through the implementation of the base station traffic processing apparatus considering the HARQ in the portable Internet system and to manage the software resources for smooth operation of HARQ By providing a base station scheduling and HARQ processing method for the stable transmission of user data.

In the portable Internet system for transmitting and receiving data on a frame-by-frame basis, which is a feature of the present invention for achieving the technical problem of the present invention, a method for processing downlink traffic and uplink traffic of a base station supporting wireless connection and network connection of a user terminal,

(a) managing a frame synchronization operation to perform synchronization processing of the clock when it is confirmed that the clock for synchronizing the downlink traffic is lost; (b) performing scheduling for the downlink traffic; (c) performing radio band allocation for transmitting data for the downlink traffic to the user terminal and resource allocation for hybrid automatic retransmission to transmit the downlink traffic to the user terminal; and (d) transmitting the downlink traffic to the user terminal. Processing data and performing response processing for the hybrid automatic retransmission.

Here, the step (a), (i) "current frame number-1" and already stored frame number-the frame number is present in the map message containing the configuration information of the frame, the scheduler in the base station is operated Determining whether the data stored in the scheduler each time matches; (ii) performing an acknowledgment (ACK) process by an inconsistent difference when the " current frame number-1 " and the frame number already stored in step (i) do not match; (iii) determining whether the stored frame number matches the "current frame number-1" in response to the hybrid automatic retransmission; and (iv) the frame already stored with the "current frame number-1" in the step (iii). If the numbers do not match, then processing the burst waiting for a response to the hybrid automatic retransmission, the burst being a combination of protocol data units, as an acknowledgment.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

3 schematically shows the structure of a portable Internet system according to an embodiment of the present invention.

The portable Internet system basically includes a base station 100, 100 ', a terminal 200 which is a mobile terminal device for wireless communication with the base station, routers 300 and 310 connected through a gateway and a base station, and an internet network. In the present embodiment, for convenience of description, the mobile terminal device is referred to as a user terminal.

Here, the base station 100 performs functions such as access control of a user terminal, packet matching between a wired section and a wireless section, wireless transmission and reception control, and radio band management, and in particular, traffic processing and packet scheduling, radio link control, and radio resource. It performs functions such as management, packet matching between wired section and wireless section, and HARQ control.

In the portable Internet system, even when the terminal 200 illustrated in FIG. 3 moves from a cell managed by one base station 100 to a cell managed by another base station 100 ′, the terminal 200 provides a data communication service that is not interrupted by ensuring its mobility. The mobile station supports handover of the terminal 200 like the mobile communication service, and performs dynamic IP address allocation according to the movement of the terminal 200.

Here, the wireless portable Internet terminal 200 and the base station 100 may perform communication in an orthogonal frequency division multiple access (OFDMA) scheme, but is not limited thereto. The OFDMA scheme is a multiplexing scheme combining a frequency division scheme using a plurality of orthogonal frequency subcarriers as a plurality of subchannels and a time division scheme. The OFDMA scheme is inherently resistant to fading occurring in multipath, and has a high data rate.

IEEE 802.16e is an adaptive modulation coding scheme (AMC: adaptive modulation and coding scheme in which modulation and coding schemes are adaptively selected by request / acceptance between the terminal 200 and the base station 100). and Coding).

4 is an operation diagram of a base station in a portable Internet system according to an embodiment of the present invention.

Referring to FIG. 4, in a portable Internet system, a base station traffic processing apparatus performs scheduling according to frame synchronization and configures a map message to maintain frame-based wireless transmission. The base station traffic processing apparatus uses a hardware clock as an apparatus for synchronizing operation. For example, assuming a frame synchronization of 5 msec, an operation is triggered by a 1 msec clock interrupt by dividing a frame into five sections, and uplink / downlink traffic processing and scheduling are performed.

In detail, when the clock interrupt number 0 occurs in the base station traffic processing apparatus and the scheduler, the scheduler of the base station 100 performs downlink traffic scheduling, and accordingly, a MAC-PDU (Media Access Control Protocol Data Unit), frame data, and the like. A map message is generated and delivered to the base station transmitter. The base station transmitter, which has received the MAC-PDU, map message and frame data, transmits the radio section in accordance with the next frame synchronization through the encoder and the modulator.

In this case, the frame data includes a combination of downlink user bursts classified according to each user's MCS and a map message including up / down burst information in the current frame. Here, the user burst is composed of a combination of MAC-PDUs that split or compress downlink traffic.

The HARQ response signal and the uplink data received in the uplink frame in the radio section are subjected to decoding and demodulation. Subsequently, when the clock interrupt 3 occurs, the base station traffic processing apparatus reads uplink data and HARQ ACK / NAK signals from the base station receiver, processes the data, and transmits the service data unit (SDU) to the network and processes the HARQ ACK / NAK signals. Perform.

The processing operation for the uplink frame received from the base station transmitter is performed from clock interrupt 3. The uplink MAC-PDUs received from the base station transmitter are transmitted to the network after combining or decompressing the SDU with the SDU. If there is an allocation request, the band request is forwarded to the uplink scheduling part. The uplink frame processing method related to this will be described in detail with reference to FIG. 7.

When the uplink processing is completed as described above, the scheduling is performed by the base station scheduler and the frame data including the retransmission burst is transmitted to the base station radio transceiver. The downlink traffic scheduling operation at this time will be described in detail with reference to FIGS. 5, 6, and 8.

5 is a downlink scheduling structure considering HARQ according to an embodiment of the present invention, FIG. 6 is a downlink scheduling flowchart considering HARQ according to an embodiment of the present invention, and FIG. 8 is a downlink according to an embodiment of the present invention. A flowchart of a frame synchronization management procedure during scheduling.

As shown in FIG. 5, the scheduler of the base station generates a burst of MAC-PDUs by allocating a radio band according to the order of items queued in the transmission waiting queue, determining the actual transmittable data size, and forming a burst of a plurality of bursts. Generate data. The frame data generated as described above is transmitted to the radio section through the physical layer.

In general, the specification of the mobile Internet system does not define a scheduling structure. For initial transmission, one burst can be made by packing or fragmenting data packets according to the amount of resources in a frame, but retransmission of the already transmitted burst has the same data burst size. Should be used. In addition, multiple HARQ channel transmissions are required to maintain burst information only with a general initial transmission data queue, which complicates buffer management.

Therefore, the packets received from the network are first stored in the initial transmission data queue, and the radio scheduling is performed and combined into PDUs and bursts and transferred to the retransmission burst queue after the transmission to the radio section is completed. When the packet is moved to the retransmission burst queue, the packets may be separately managed according to the HARQ ACK response, thereby simplifying the buffer management and scheduling operations according to the HARQ operation. In this case, the scheduling of the retransmission burst queue is given priority because the retransmission burst queue has a high priority due to retransmission, and since the required radio resources are already determined, the flexibility of band management is reduced.

A scheduling procedure performed in the downlink scheduling structure as shown in FIG. 5 will be described in detail. The scheduling procedure triggered from the clock 0 interrupt is performed from the frame synchronization management (S500) procedure of checking and processing clock loss as shown in FIG. 8. The frame synchronization control procedure determines whether "(current frame number-1)% 2048" is equal to a previously stored frame number (S501). At this time, the frame number is present in the map message including the configuration information of the frame, and stored in the scheduler whenever the scheduler in the base station 100 operates.

If the result is different from the previously stored frame number gPrevFN, the burst is regarded as omitted and the burst transmitted for a frame equal to the difference from the current frame number from the previous operation frame is abandoned the transmission confirmation and processed as an ACK (S502). do. After the ACK processing of the burst transmitted for the frame corresponding to the difference from the current frame number, it is determined whether or not the frame number gAckRxFN stored in the HARQ response processing and the current frame number minus% 2048 are different (S503). . If it is determined to be different, the HARQ response cannot be processed due to a clock omission or reception failure. Therefore, the current frame number-1 waits for a response to the previous frame as if% 2048 is different from the previously stored frame number. All of the bursts are processed as ACK (S504).

Through such a frame management procedure, a buffer overflow due to skipping HARQ response processing and service suspension or restriction on user data due to exhaustion of ACID resources can be solved. In order to solve the problem caused by skipping HARQ response processing, a response wait timer may be driven for each transmission burst, but a processing load due to timer operation in a portable Internet system in which a large number of transmission bursts are sustained due to high-speed traffic transmission. It can seriously affect the whole operation.

When the frame synchronization management procedure S500 described with reference to FIG. 5 is completed, scheduling for downlink traffic is started as shown in FIG. 6. Scheduling for the downlink traffic is first performed burst allocation for HARQ retransmission, and performs scheduling for the initial transmission data for the remaining frame resources, that is, subchannels.

HARQ retransmission wait queue is used for retransmission burst allocation. The queue stores items including the user ID and retransmission burst information according to the retransmission request order.

The scheduler performs band allocation in accordance with the First-Come First-Service (FCFS) rule, which first processes data items stored in the queue first from the retransmission wait queue. After retransmission burst allocation is completed, scheduling of initial transmission traffic is performed. Packet scheduling, MCS level setting, radio band allocation, and HARQ ACID allocation are performed according to FCFS, Round-Robin, or a specific algorithm that can improve system performance. The downlink scheduling procedure is completed by constructing a MAP message based on the combination of bursts and the radio band allocation information generated according to the scheduling result and delivering the MAP message to the base station transmitter.

Here, the user information used in the base station traffic processing apparatus further allocates a memory region having the structure shown in Table 1 below to support HARQ.

When the frame synchronization management procedure S500 described above with reference to FIG. 8 is completed, the number of subchannels RCtotal (i) that can be allocated to the current frame i is defined as the same as the number of remaining subchannels RCrest. The number of subchannels RCtotal in the radio frame required for transmitting data to be serviced is calculated (S510). In this case, the number of subchannels that can be allocated means the number of necessary subchannels that can be allocated according to extra radio resources.

The required number of subchannels means the number of subchannels that are fixedly calculated for retransmission of a retransmission burst, and can be defined as in the following formula: "Allocated data size / ((modulation method factor * coding rate) * 6)" It is not limited. If the number of remaining subchannels is larger than the number of subchannels necessary for retransmission (S520), the remaining subchannels are updated after allocating a retransmission burst.

That is, if the number of subchannels is greater than the number of remaining subchannels in the current frame (S520), the size of service data that can be transmitted to the currently available subchannel is calculated. Data corresponding to the calculated size among the data to be serviced is allocated to the available subchannel (S530), and the remaining data is processed to be serviced in the next frame.

When the number of remaining subchannels is less than the number of necessary subchannels for retransmission, it is determined whether or not there are no remaining subchannels at all in order to process the remaining data to be serviced in the next frame (S540). If not at all, a downlink map is constructed and frame data is transmitted. However, if there is a remaining number of subchannels, the scheduling for the downlink is performed, a packet to be transmitted is selected (S550), and a subchannel to which a packet is to be allocated is calculated (S560).

When the calculation of the subchannel to be allocated is completed, the number of remaining subchannels and the required subchannels are again compared (S570). If the number of remaining subchannels is less than the required number of subchannels, a MAP is formed and frame data is transmitted to the transmitter of the base station. However, if the number of remaining subchannels is larger than the required number of subchannels, the scheduler generates PDUs by providing PDU generation information to the PDU generating apparatus to generate MAC-PDUs for radio segment transmission for the allocated data (S580). The number of channels is updated as a result of "number of remaining subchannels-number of required subchannels" (S590).

The scheduler repeats steps S550 to S590 until there are no remaining subchannels in the current frame. That is, when there is no number of " RCrest-RCmargin " after updating the remaining number of subchannels (S600), MAP is configured and frame data is transmitted (S610). However, if "RCrest-RCmargin" is greater than zero, the process is performed again from step S550. Here, RCmargin means the minimum allocation unit of resources that can not send even the header of the MAC.

Downlink processing is performed in this manner, and the uplink processing method of the base station scheduler operation illustrated in FIG. 4 will be described in detail with reference to FIG. 7.

7 is a flowchart illustrating HARQ ACK / NAK processing according to an embodiment of the present invention.

The uplink frame processing operation starts from clock interrupt 3, and performs uplink MAC-PDUs received from the base station transmitter to the network after performing combination or decompression to the SDU and uplink scheduling when there is an uplink allocation request. The band request for the part is forwarded to the base station. After processing the HARQ response signal, the corresponding burst information of the received ACK or NAK is obtained (S700), and in the case of ACK (S710), the pending burst resource is released (S740), and in the case of NAK, the maximum number of retransmissions is determined. Increase (S720).

When the maximum number of retransmissions is increased and the number of increased retransmissions is compared (S730), when the increased number of retransmissions does not exceed the maximum number of retransmissions, the SPID is changed and set (S760) and stored in the HARQ retransmission wait queue, which is a retransmission request list (S770). . If the maximum number of retransmissions is exceeded, in order to abandon the transmitted burst and continue the next data transmission, the ACID is released (S740), and the buffered transmission data burst is released (S750) and processed as an ACK.

In this case, when the clock interrupt 3 is omitted, such as when the external hardware clock reception fails or when the clock read cannot be performed in time according to task scheduling of the traffic processing module of the base station, the upward described above The frame processing procedure cannot be performed. In such a case, an abnormal accumulation of burst resources is caused and it is difficult to continue the wireless data transmission service for the user. However, the base station traffic processing apparatus according to the embodiment of the present invention can solve the abnormal operation problem because the frame synchronization management procedure described with reference to FIG. 8 is performed.

Since the HARQ response signal for the frame data transmitted to the base station receiver can be processed by the base station traffic processing apparatus several frames later according to the system parameter, the base station traffic processing apparatus stores the transmission frame information and then receives the corresponding burst and Extract the user from the storage frame information. The frame information stored in the base station traffic processing apparatus is stored as the number of frames (HARQ_ROUND_TRIP_FRAM) from HARQ burst transmission to HARQ response reception, and the frame number when processing the HARQ response signal is calculated in HARQ_ROUND_TRIP_FRAM, and the corresponding frame information is obtained. Search for. Frame information at this time is shown in the following [Table 2].

Here, a program for realizing a function corresponding to the configuration of the above-described embodiment of the present invention or a recording medium on which the program is recorded is also included in the scope of the present invention.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the above-described embodiment, smooth HARQ operation can be supported by performing resource management and transmission control for HARQ operation when scheduling a base station, and can solve a problem of deadlock caused by loss of frame synchronization or failure of HARQ ACK / NAK reception. I can solve it.

Claims (9)

In the portable Internet system for transmitting and receiving data on a frame-by-frame basis, a method for processing downlink and uplink traffic of a base station supporting wireless access and network connection of a user terminal, (a) managing a frame synchronization operation to perform synchronization processing of the clock when it is confirmed that the clock for synchronizing the downlink traffic is lost; (b) performing scheduling for the downlink traffic; (c) performing radio band allocation for transmitting data for the downlink traffic to the user terminal and resource allocation for hybrid automatic retransmission to transmit the downlink traffic to the user terminal; And (d) processing data for the uplink traffic and performing response processing for the hybrid automatic retransmission; Base station traffic processing method comprising a. The method of claim 1, In step (a), (i) "current frame number-1" and already stored frame number, where the frame number is present in a map message containing the configuration information of the frame and stored in the scheduler whenever the scheduler in the base station operates; Determining if-matches; (ii) performing an acknowledgment (ACK) process by an inconsistent difference when the " current frame number-1 " and the frame number already stored in step (i) do not match; (iii) determining whether the frame number stored in the scheduler and the "current frame number-1" match in response to the hybrid automatic retransmission; And (iv) if the " current frame number-1 " and the frame number already stored in step (iii) do not match, a burst awaiting response to the hybrid automatic retransmission, where the burst is a combination of protocol data units; Step into the response Base station traffic processing method comprising a. The method of claim 1, In step (b), (i) calculating a number of subchannels in a radio frame required for retransmission after allocating a burst for hybrid automatic retransmission of the downlink traffic; (ii) if the number of subchannels in the calculated radio frame is greater than the remaining number of subchannels in a current frame, calculating a size required for the hybrid automatic retransmission that can be transmitted to a currently available subchannel; (iii) allocating a frame corresponding to the calculated size to the available subchannels among the transmission frames requiring hybrid automatic retransmission, and then performing scheduling for initial transmission data on the remaining frames; And (iv) generating a map message based on the combination of the bursts generated according to the scheduling and the radio band allocation information; Base station traffic processing method comprising a. The method of claim 3, In step (b), Packet scheduling, level setting of modulation and channel coding combinations, radio band allocation, and automatic retransmission channel identifiers from either a first come first service (FCFS) or Round Robin algorithm from a retransmission wait queue to allocate bursts for the hybrid retransmission. Base station traffic processing method for performing assignment. The method of claim 1, In step (d), (Iv) decompressing after combining data for uplink traffic for transmission to the user terminal and hybrid automatic retransmission signal into an SDU; (Ii) determining whether the hybrid automatic retransmission response signal included in the downlink traffic is a positive response; And; (Iii) releasing the resources of the burst waiting for a response to the hybrid automatic retransmission response signal when determined to be a positive response. Base station traffic processing method comprising a. The method of claim 5, If it is determined in step (ii) that the response is not affirmative, Increasing the number of retransmissions for the hybrid automatic retransmission; Decoding and then decoding the data for the uplink traffic; Changing a subpacket identifier indicating an order of subpackets generated by dividing the decrypted data; And Storing the hybrid automatic retransmission response signal in a retransmission waiting queue Base station traffic processing method comprising a. The method of claim 6, And acknowledging the hybrid automatic retransmission response signal when the number of retransmissions exceeds a predetermined maximum number of retransmissions. The method of claim 1, And the frame data includes a map message including a combination of downlink user bursts classified according to a modulation and channel coding combination and up / down burst information within a current frame. The method of claim 1, The clock is a base station traffic processing method, characterized in that for using the hardware clock for the transmission and reception of data in synchronization every frame.

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