KR101873554B1 - Method and Apparatus Radio Link Control in Small Cell Base Station - Google Patents

Abstract

The present invention relates to a radio link control method and apparatus for a small cell base station for shortening retransmission data cancellation time.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a radio link control method and apparatus for a small-

The present invention relates to a radio link control method and apparatus for a small cell base station for shortening retransmission data cancellation time.

In general, small cell base stations are being developed based on low-cost hardware. For this reason, the software of the small cell base station should be designed considering the limitations on memory and execution time. The RLC (Radio Link Control) protocol corresponding to the base station communication protocol function provides a retransmission function which is an error control function of the radio link. Upon receipt of the ACK information (STATUS PDU) indicating that the transmission is successful, the transmitting side deletes the data information from the PDU memory for the PDU (Protocol Data Unit). Therefore, the data deletion in the PDU memory occurs randomly instead of sequentially in the order of transmission. Since a small cell base station using low-cost hardware has a memory limitation, it is effective to configure the buffer structure in the form of a linked list instead of an array type. At this time, it is required to reduce the time required to find the corresponding PDU and the time required to find the SDU (Service Data Unit) constituting the PDU.

It is an object of embodiments of the present invention to provide a radio link control method and apparatus for a small cell base station for shortening retransmission data cancellation time.

The technical problems of the present invention are not limited to the above-mentioned technical problems, and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

A radio link control method according to an aspect of the present invention includes: storing PDU data including PDU configuration information on a PDU transmitted from a base station and SDU configuration information on a fragmented SDU corresponding to each PDU in a buffer memory; And determining whether to ACK or NACK from the STATUS PDU information fed back from the receiver in response to the transmitted PDU and managing a bit value corresponding to the corresponding sequence number in the bitmap of the buffer memory.

Wherein the PDU configuration information includes a PDU data length for each PDU to be transmitted, an index of the first SDU configuration information, a number of SDUs constituting the PDU, and an index of the fragmented SDU, The SDU data length for each fragmented SDU, the memory address for the SDU, the size of the transmitted SDU, and the bitmap information of the PDUs corresponding to the SDU transmission.

The managing step may include searching PDU data corresponding to a corresponding sequence number having a bit value of '1' in the bitmap according to an ACK of the STATUS PDU information for the transmitted PDU and releasing the PDU data from the buffer memory .

In the managing step, if consecutive ACKs are received for the transmitted PDUs, processing of intermediate PDUs is skipped and PDU information having the lowest sequence number and PDU information having the highest sequence number are processed for fast processing The SDU having the smallest index and the SDU having the largest index among the SDUs set to '0' among the bitmap information are extracted, and based on the extracted SDU, It is possible to transmit the success information to the upper protocol and manage release, thereby shortening the retransmission data cancellation time.

The radio link controller according to another aspect of the present invention stores PDU data including PDU configuration information for a PDU transmitted from a base station and SDU configuration information for a fragmented SDU corresponding to each PDU, A buffer memory in which information includes bitmap information for the transmitted PDU; And determining whether ACK or NACK is received from the STATUS PDU information fed back from the receiver in response to the transmitted PDU, and managing a bit value corresponding to the corresponding sequence number in the bitmap of the buffer memory storing the bitmap information And a control unit.

Wherein the PDU configuration information includes a PDU data length for each PDU to be transmitted, an index of the first SDU configuration information, a number of SDUs constituting the PDU, and an index of the fragmented SDU, The SDU data length for each fragmented SDU, the memory address for the SDU, the size of the transmitted SDU, and the bitmap information of the PDUs corresponding to the SDU transmission.

The controller may search PDU data corresponding to the corresponding sequence number having a bit value of '1' in the bitmap according to the ACK of the STATUS PDU information for the transmitted PDU and release the PDU data from the buffer memory.

The control unit may omit the processing of the intermediate PDUs when receiving successive ACKs for the PDUs to be transmitted, and for the fast processing, based on the PDU information having the lowest sequence number and the PDU information having the highest sequence number, Extracts the SDU having the smallest index and the SDU having the largest index among the SDUs set to '0' among the bitmap information, extracts the transmission success information of the SDU based on the extracted SDU, It is possible to shorten the retransmission data cancellation time by transmitting to the upper protocol and managing release.

According to the radio link control method and apparatus of a small cell base station according to an embodiment of the present invention, when a small cell base station is developed with low-cost hardware, there is a restriction on the memory of the hardware, the speed and the number of the CPU (Central Processing Unit) And a radio link control (RLC) method for satisfying a processing time required in a base station communication protocol, thereby reducing retransmission data cancellation time in a hardware condition with a small memory capacity and a low CPU processing speed It is possible to process necessary functions such as radio link control within a required processing time through efficient link control.

1 is a diagram for explaining STATUS PDU information transmitted from a receiving side of a BS in an embodiment of the present invention.
2 is a diagram for explaining a radio link control apparatus of a base station according to an embodiment of the present invention.
3 is a diagram for explaining a bitmap management method in a controller of a radio link control apparatus according to an embodiment of the present invention.
4 is a diagram for explaining a bitmap managed in a buffer memory by a controller of a radio link controller of a base station in order to identify ACK information in an embodiment of the present invention.
5A is a diagram for explaining an example of usage of PDU configuration information and SDU configuration information in a radio link control apparatus according to an embodiment of the present invention.
5B is a diagram illustrating an example of a method in which fragmented SDUs are transmitted through a PDU in a radio link control apparatus according to an embodiment of the present invention.
6 is a flowchart illustrating an operation of performing quick release of a buffer memory when a continuous ACK is received in a controller of a radio link control apparatus according to an exemplary embodiment of the present invention.
7 is a view for explaining an example of a method of implementing components of a radio link control apparatus of a base station according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the difference that the embodiments of the present invention are not conclusive.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. Also, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

The present invention manages a buffer structure in the form of a linked list in the management of a downlink buffer memory which is managed separately for each user and within a user in a mobile communication (e.g., WCDMA, LTE, etc.) I suppose. The base station can store packets received from a mobile communication network (e.g., WCDMA, LTE, etc.) network in a corresponding connection list buffer in the order received according to user and bearer information.

When a base station communication protocol is operated in a retransmission mode for recovering an error of a wireless link, a PDU processing unit that performs a retransmission function and processes an RLC protocol generates an ACK / ACK from a data receiving side, such as a user terminal, based on a PDU SN (Sequence Number) NACK (Acknowledgment / No-acknowledgment). The PDU processing unit, in the buffer memory managing the SDU information constituting each PDU according to the RLC protocol, is configured to transmit the corresponding PDU data (SDU data constituting the PDU including the RLC header) Release (data deletion). If the receiving side, such as a user terminal receiving data transmitted by the base station, succeeds in receiving data, the PDU information can be fed back as a STATUS PDU as shown in FIG.

1 is a diagram for explaining STATUS PDU information transmitted from a receiving side of a BS in an embodiment of the present invention.

As shown in FIG. 1, the STATUS PDU corresponds to feedback information in the form of a cumulative ACK (accumulative ACK) and a selective NACK (selective NACK). The STATUS PDU consists of octet-aligned (Oct1,2,3 ..) D / C (Data / Control), CPT (Control PDU Type), ACK_SN (Sequence Number), NACK_SN, E (Extension) Segment Offset Start), and SOend (Segment Offset End).

That is, the STATUS PDU includes feedback information for a PDU within an ACK_SN length, and includes a specific SN (Sequence Number) only for NACK and length information of the PDU. All other SNs that are not NACKs should be treated as ACKs. The accumulative ACK scheme is a method for reducing the amount of feedback information by transmitting only the largest SN (Sequence Number) among consecutive ACKs. The disadvantage of this scheme is that the duplicated ACK information must be distinguished from the transmitting side . To this end, a base station (e.g., using software) defines a bitmap according to a TX PDU (a transmitting PDU). In order to distinguish ACK information, the number of bit values or bit map information (bits) indicating the transmission / reception position of the corresponding PDU in the base station is equal to the number of SNs in the PDU. Therefore, when this bitmap has a maximum SN size (for example, 1024), it needs only 1024/8 = 128 bytes of memory size when stored in the buffer memory.

2 is a diagram for explaining a radio link control apparatus 100 of a base station according to an embodiment of the present invention.

2, the radio network controller 100 according to an exemplary embodiment of the present invention includes a controller 110 that controls overall control, a PDU buffer memory 120 having a buffer structure in the form of a linked list, . The PDU buffer memory 120 includes a bitmap 121, an SDU buffer 122, and a PDU buffer 123.

For example, the PDU buffer memory 120 stores PDU configuration information for a PDU transmitted from a base station in the PDU buffer 123, and stores SDU configuration information for the fragmented SDU corresponding to each PDU in the SDU buffer 122 ). SDU configuration information including bitmap information (PDU_ACK_BitMap) of PDUs corresponding to SDU transmission is stored in the SDU buffer 122, and bitmap information (PDU_ACK_BitMap) is stored and managed in the bitmap 121 .

In response to the PDU transmitted from the base station, the control unit 110 determines whether ACK or NACK is received from the STATUS PDU information fed back from the receiver, and transmits the ACK or the NACK to the bitmap 121 of the buffer memory 120, The bit value (0 or 1) corresponding to the sequence number can be managed. For example, the controller 110 transmits PDU data (PDU configuration information, SDU configuration information) corresponding to a corresponding sequence number having a bit value of '1' according to an ACK of STATUS PDU information for a PDU transmitted from a base station, And release it from the buffer memory 120.

In the present invention, a base station may be a user terminal (e.g., a smart phone, a wearable device, a tablet PC, a notebook PC, a desktop PC, etc.) and a core A relay apparatus such as a relay station, an NB (Node B), an evolved NB, a home-eNB, a RRH (Remote Radio Head), and an AP (Access Point) And may be in the form of a small cell or a pico cell or a femto cell.

3 is a diagram illustrating a method of managing a bitmap 121 in the controller 110 of the RLC 100 according to an embodiment of the present invention.

3, when generating a PDU from a base station and transmitting it to a receiver such as a user terminal (S110), the controller 110 checks the bitmap (S111) and sets the bit of the corresponding SN to 1 (S112 ). The controller 110 processes the STATUS PDU information fed back from the receiver and, when the corresponding ACK is received, sets the bit of the corresponding SN to '0'. When the bitmap is checked (S111), the control unit 110 returns an error if the SN bit is already 1 due to duplication of the SN of the PDU or the like. In case of such an error, the control unit 110 may change the bit value to a different value for the corresponding PDU.

On the other hand, when the base station generates and transmits the PDU, the control unit 110 receives the STATUS PDU information (status PDU information) fed back from the receiving side (S120). The control unit 110 extracts the ACK_SN from the STATUS PDU information (S121), checks the bit of the corresponding SN in the bit map (S122), and if it is '0', recognizes that the PDU has already been processed as ACK and does not retrieve the PDU data ). On the other hand, if the bit of the corresponding SN is checked in the bit map (S122), the controller 110 sets the bit of the corresponding SN to '0' (S124) and searches the buffer memory for the corresponding PDU data S125). The PDU data such as the searched PDU configuration information may be transferred to another unit or block for subsequent processing and deleted from the buffer memory 120 (S126).

4 is a diagram for explaining a bitmap 121 managed in the buffer memory 120 by the control unit 110 of the radio link controller 100 of the base station in order to distinguish ACK information according to an embodiment of the present invention .

4, an ACK corresponding to PDUs (e.g., fragmented PDUs) (0 to 3), (n-3 to n + 2), and (n + 5 to n + 6) (For example, reception of a NACK), the corresponding bits of the bitmap are maintained at '1'.

5A is a diagram for explaining an example of using PDU configuration information 410 and SDU configuration information 420 in the radio link control apparatus 100 according to an embodiment of the present invention.

Generally, because there is a limit in the memory size that can be used by the base station, it is not necessary to re-copy the packet received from the network, store the received packet in only one memory, A zero-copy structure can be used. In such an environment, the RLC protocol should provide the ability to configure PDUs by segmenting and concatenating SDUs. In addition, when SDUs divided over multiple PDUs are transmitted, SDU data should be deleted from the memory only when all the PDUs are successfully transmitted.

5A, the control unit 110 of the radio link control apparatus 100 stores and manages the PDU configuration information 410 and the SDU configuration information 420 constituting the PDU data in the buffer memory 120 .

The PDU configuration information 410 includes a PDU data length for each PDU transmitted (e.g., PDU (x), PDU (x + 1), ...), an index of the first SDU configuration information, . In addition, the PDU configuration information 410 may further include a fragmented SDU index (FI) of the fragmented SDU. For example, if the number of SDUs is 1 and the PDU configuration information 410 includes any one of 0x3, 0x1, etc., it can be judged to be valid.

The SDU configuration information 420 includes SDU data lengths for each fragmented SDU (e.g., SDU (i), SDU (i + 1), ...) corresponding to each PDU, a memory address for the SDU, The bitmap information (PDU_ACK_BitMap) of the PDUs corresponding to the SDU transmission, and the like.

FIG. 5B is a diagram illustrating an example of a method in which fragmented SDUs are transmitted through a PDU in the radio link control apparatus 100 according to an embodiment of the present invention.

As described above, the size of the bitmap 121 can be determined according to which SDU is divided into a maximum number of PDUs to be transmitted. In the SDU division and concatenation transmission scheme, the BS configures a PDU, sets a PDU bitmap corresponding to the configuration information of fragmented SDUs to '1' in each bit corresponding to each SN, and transmits PDUs , The bit of the corresponding PDU is set to '0' in this bitmap. If all ACKs for all fragmented and transmitted PDUs are received, the corresponding PDU data (PDU configuration information, SDU configuration information) corresponding to the bitmap is deleted from the memory 120.

For example, a plurality of SDUs (e.g., SDU (i), SDU (i + 1) of a predetermined size) are transmitted through one PDU (x) having a predetermined size It is possible. In this case, the PDU configuration information 410 may include an index i of the first SDU configuration information, a number 2 of SDUs constituting the PDU, and the like.

5, one SDU (i + 3) having a predetermined size is divided into a fragmented SDU (i + 1) through a plurality of PDUs (e.g., SDU May be transmitted separately. Each PDU is transmitted with an RLC header, followed by each fragmented SDU.

6 is a flowchart illustrating an operation of performing quick release of the buffer memory 120 when a continuous ACK is received by the controller 110 of the RLC 100 according to an exemplary embodiment of the present invention. That is, when the first consecutive ACK is received for the PDUs to be transmitted, the bitmap information is collectively processed by the PDU information having the smallest SN and the PDU information having the largest SN (For example, PDCP, Packet Data Convergence Protocol), and transmits the transmission success information of the SDU to the buffer memory 120 in a short period of time FIG.

Referring to FIG. 6, a BS transmits PDUs, and receives STATUS PDU information fed back from a receiver, such as a user terminal, in response thereto (610).

Accordingly, the controller 110 searches 611 the SN of the first fragmented SDU and the SN of the fragmented SDU that were transmitted most recently among the PDUs (the PDUs that received the ACK) that do not include a NACK in the STATUS PDU, . Thereafter, the controller 110 searches PDU information having the corresponding SN (s) in the PDU buffer 123 (612), and determines whether the fragmented SDU corresponding to the corresponding PDU is one (613).

For example, if the number of fragmented SDUs is 1 in the PDU information and the fragmented SDU index FI is 0x3, 0x1, etc., it is valid (620) The bit corresponding to the fragmented SDU index of the fragmented SDU in the bitmap information (PDU_ACK_BitMap) of the information is set to '0' (621). If the fragmented SDU index of the fragmented SDU is not valid, only the last bit of the bitmap information (PDU_ACK_BitMap) of the corresponding SDU is set to '0' (622).

If the number of fragmented SDUs corresponding to the PDU is plural (1 to numSDN) (613), the fragmented SDU index FI (eg, 0x0, 0x1, 0x2, 0x3) of the fragmented SDU of the PDU information The controller 110 may manage bitmap information (PDU_ACK_BitMap) as follows (630).

First, for example, if FI = 0x1 (e.g., valid from the first SDU to the numSDU-1), the bit corresponding to the index of the corresponding SDU in the bitmap information (PDU_ACK_BitMap) of the SDU from the first SDU to the numSDU- To '0', and sets only the last bit of the bitmap information (PDU_ACK_BitMap) of the last SDU (numSDU) to '0' (631).

For example, if FI = 0x0 (e.g., all of the first SDU to numSDU are valid), the bit corresponding to the index of the corresponding SDU in the bitmap information (PDU_ACK_BitMap) of the SDU from the first SDU to the last numSDU is set to ' 0 " (632).

For example, when FI = 0x3 (e.g., valid from the second SDU to the numSDU-2), the largest bit is set to '0' in the bitmap information (PDU_ACK_BitMap) of the first SDU, and numSDU The bit corresponding to the index of the SDUs is set to '0' in the bitmap information (PDU_ACK_BitMap) of the SDU up to -2 and only the last bit of the bitmap information (PDU_ACK_BitMap) of the last SDU (numSDU) is set to '0' (633).

For example, when FI = 0x2 (e.g., valid from the second SDU to numSDU-1), the largest bit is set to '0' in the bitmap information (PDU_ACK_BitMap) of the first SDU, and numSDU The bit corresponding to the index of the corresponding SDUs in the bitmap information (PDU_ACK_BitMap) of the SDUs up to -1 is set to '0' (634).

If the bitmap information (PDU_ACK_BitMap) of the corresponding SDU (s) is set according to the received PDU information, the controller 110 selects one of the SDUs set in the mode '0' among the bitmap information (PDU_ACK_BitMap) SDUs having the smallest SDU index (min_index) and the largest SDU index (max_index) are extracted (640) and stored in a memory or the like (641), and the received SDU list, min_index, max_index, PDCP, Packet Data Convergence Protocol) (processing means) (642). At this time, the controller 110 can delete the corresponding information from the buffer memory 120 through releasing data corresponding to min_index to max_index and the corresponding SDU configuration information 420.

FIG. 7 is a view for explaining an example of a method of implementing the elements of the radio link control apparatus 100 of a base station according to an embodiment of the present invention. The radio link control apparatus 100 according to an embodiment of the present invention may be implemented by hardware, software, or a combination thereof. For example, the radio link control apparatus 100 according to an embodiment of the present invention may be implemented in the computing system 1000 as shown in FIG.

The computing system 1000 includes at least one processor 1100, a memory 1300, a user interface input device 1400, a user interface output device 1500, a storage 1600, And an interface 1700. The processor 1100 may be a central processing unit (CPU) or a memory device 1300 and / or a semiconductor device that performs processing for instructions stored in the storage 1600. Memory 1300 and storage 1600 may include various types of volatile or non-volatile storage media. For example, the memory 1300 may include a ROM (Read Only Memory) 1310 and a RAM (Random Access Memory)

Thus, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by processor 1100, or in a combination of the two. The software module may reside in a storage medium (i.e., memory 1300 and / or storage 1600) such as a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, You may. An exemplary storage medium is coupled to the processor 1100, which can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integral to the processor 1100. [ The processor and the storage medium may reside within an application specific integrated circuit (ASIC). The ASIC may reside within the user terminal. Alternatively, the processor and the storage medium may reside as discrete components in a user terminal.

As described above, according to the radio link control apparatus 100 according to an embodiment of the present invention, when a small cell base station or the like is developed with low-cost hardware, restrictions on the memory, CPU (Central Processing Unit) It is possible to provide a radio link control (RLC) method for satisfying the processing time required in the base station communication protocol, thereby enabling the retransmission data to be transmitted in a hardware condition with a small memory capacity and low CPU processing speed It is possible to process necessary functions such as radio link control within the required processing time through efficient link control such as shortening of the release time.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. For example, although LTE is described as an example of mobile communication above, it is an example only and can be similarly applied to various wireless communication field based MBMS services instead of LTE.

Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

The controller 110,
PDU buffer memory 120,
In the bitmap 121,
SDU buffer 122,
PDU buffer 123,

Claims (5)

Storing PDU data including PDU configuration information for a PDU transmitted from a base station and SDU configuration information for a fragmented SDU corresponding to each PDU in a buffer memory;
Transmitting the PDU to a receiver;
Identifying a bitmap for the PDU;
Setting the bit value to '1' when the bit value of the sequence number of the PDU is '0', and returning an error to the receiving side when the bit value of the sequence number of the PDU is '1'; And
Determining whether ACK or NACK is received from the STATUS PDU information fed back from the receiver in response to the transmitted PDU and managing a bit value corresponding to the corresponding sequence number in the bitmap of the buffer memory
/ RTI >
The managing step may include setting a corresponding sequence number having a bit value of '1' as '0' according to ACK of the STATUS PDU information for the transmitted PDU
Wireless link control method. The method according to claim 1,
Wherein the PDU configuration information includes a PDU data length for each PDU to be transmitted, an index of the first SDU configuration information, a number of SDUs constituting the PDU, and an index of the fragmented SDU, The SDU data length for each fragmented SDU, the memory address for the SDU, the size of the transmitted SDU, and the bitmap information of the PDUs corresponding to the SDU transmission. The method according to claim 1,
Wherein the managing comprises:
Searching PDU data corresponding to a corresponding sequence number having a bit value of '1' in the bitmap according to an ACK of the STATUS PDU information for the transmitted PDU and releasing the PDU data from the buffer memory
Wherein the radio link control method comprises the steps of: The method according to claim 1,
In the managing step,
When receiving successive ACKs for PDUs to be transmitted, processing of intermediate PDUs is skipped and based on PDU information having the lowest sequence number and PDU information having the highest sequence number for fast processing, Extracts the SDU having the smallest index and the SDU having the largest index among the SDUs set to '0' among the bitmap information, and transmits the transmission success information of the SDU to the upper protocol And the retransmission data release time is shortened by managing the transmission and release. The PDU includes PDU data including PDU configuration information for a PDU transmitted from a base station and SDU configuration information for a fragmented SDU corresponding to each PDU, the SDU configuration information including a bitmap information for the transmitted PDU Memory; And
Sets the bit value to '1' when the bit value of the sequence number of the PDU is '0', and transmits the bit of the sequence number of the PDU to the receiving side, And if the value is '1', returns an error to the receiving side, determines whether ACK or NACK is received from the STATUS PDU information fed back from the receiving side in response to the transmitted PDU, A control unit for managing bit values corresponding to the corresponding sequence numbers in the bit map,
/ RTI >
Wherein the control unit sets a corresponding sequence number having a bit value of '1' to '0' according to an ACK of the STATUS PDU information for the transmitted PDU.

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