KR20060074011A - Method of controlling data transmission for mbs in broadband wireless access system - Google Patents

Abstract

The present invention relates to a data transmission control method for multimedia and broadcasting service (MBS) in a broadband wireless access system. A method of controlling data transmission for a multicast and broadcast service in a broadband wireless access system according to the present invention includes: a first step of transmitting MBS data to at least one mobile subscriber station (MSS); Feedback information of the MBS data transmitted from a specific terminal belonging to the at least one or more terminals (identification information of the MBS data having a reception error and coding and modulation schemes suitable for the specific terminal to receive the MBS data having the reception error) Includes information about;) a second step of receiving; And a third step of retransmitting the MBS data having the reception error to the specific terminal by using the coding and modulation scheme.

MBS, Multimedia and Broadcast Services, Feedback, Transmission

Description

Method of controlling data transmission for multimedia and broadcasting service in broadband wireless access system {Method of controlling data transmission for MBS in broadband wireless access system}

1 illustrates a protocol hierarchy of a broadband wireless access system.

FIG. 2 exemplarily illustrates a process of mapping an FEC block to an OFDMA subchannel and an OFDM symbol.

3 illustrates a frame structure of an OFDMA physical layer in a broadband wireless access system.

4A illustrates the format of a MAC PDU.

4B shows an example of a band request header.

4c illustrates a structure in which a plurality of MAC PDUs are concatenated and transmitted in one uplink burst.

5A to 5C illustrate examples of configuring an ACK MAP for each type of ACK.

6 and 7 show an example of a reference model for the MBS of the broadband wireless access system.

8a and 8b are flowcharts illustrating the MBS operation of the broadband wireless access system.

9 and 10 are flow charts of the procedure of the preferred embodiment of the present invention.

11 illustrates the MBS feedback header defined for transmitting the MBS data feedback information according to an embodiment of the present invention.

12 illustrates an example of modifying and using a feedback header defined in the prior art to transmit MBS feedback information according to an embodiment of the present invention.

Figure 13 is a procedure flow diagram of another preferred embodiment of the present invention.

14 illustrates the MBS feedback header defined for transmitting the MBS feedback information according to another preferred embodiment of the present invention.

The present invention relates to a broadband wireless access system. More specifically, in the broadband wireless access system, the terminal feeds back burst profile information for receiving MBS data to the base station, and causes the base station to provide multimedia and broadcast according to the coding and modulation scheme selected based on the burst profile. The present invention relates to a data transmission control method for an MBS capable of guaranteeing the MBS data reception quality of a UE by enabling casting service (MBS) data to be transmitted.

The Broadband Wireless Access System (MAC) defines a protocol of a Media Access Control (MAC) layer and a Physical (PHY) layer for point-to-multipoint connection between a base station and a terminal. 1 illustrates a protocol hierarchy of a broadband wireless access system.

The physical layer of the broadband wireless access system is largely divided into a single carrier (Single Carrier) and a multi-carrier (OFDM / OFDMA). The multi-carrier method employs OFDM and introduces Orthogonal Frequency Division Multiple Access (OFDMA) as an access method for allocating resources in subchannel units in which a part of carriers is grouped.

Forward error correction encoding commonly uses concatenation code or block turbo code of RS code and convolutional code, and BPSK / QPSK / 16-QAM / 64-QAM. Use the modulation scheme of. Adaptive Modulation / Coding (AMC), which dynamically selects a modulation mode and a coding rate scheme according to channel conditions, is applied. Receive signal strength (RSSI), signal-to-noise ratio (CINR), or BER are used to measure channel quality for AMC.

In the OFDMA physical layer, active carriers are divided into groups and transmitted to different receivers for each group. The group of carriers transmitted to the receiver is called a sub-channel. Carriers constituting each subchannel may be adjacent to each other or spaced at equal intervals. As such, by allowing multiple accesses on a sub-channel basis, the degree of duplication in implementation is increased, but there is an advantage of efficiently performing frequency diversity gain, gain due to concentration of power, and forward power control.                         

The slot assigned to each user is defined by a data region of two-dimensional space, which is a set of consecutive subchannels allocated by bursts. In OFDMA, one data area is shown as a rectangle determined by time coordinates and subchannel coordinates. Such a data area may be allocated to an uplink of a specific user or a base station may transmit the data area to a specific user in downlink. To define such a data region in two-dimensional space, the number of OFDM symbols in the time domain and the number of consecutive subchannels starting at a position separated by an offset from a reference point in the frequency domain should be given.

The MAC data is divided according to the FEC block size, and each FEC block is extended to occupy three OFDM symbols in the time axis of each subchannel. For each FEC block, the mapping continues in sequence with increasing subchannel numbers, and when the end of the data area is reached, mapping continues from the next lower number OFDM symbol in the same way. 2 illustrates a process of mapping an FEC block to an OFDMA subchannel and an OFDM symbol.

3 illustrates a frame structure of an OFDMA physical layer in a broadband wireless access system. The downlink sub-frame begins with a preamble used for synchronization and equalization in the physical layer, and then defines the location and purpose of the bursts assigned to the downlink and uplink. The structure of the entire frame is defined through a downlink map (DL-MAP) message and an uplink map (UL-MAP) message.                         

The DL-MAP message defines the use allocated for each burst for the downlink period in the burst mode physical layer, and the UL-MAP message defines the use of the burst allocated for the uplink period. The information element constituting the DL-MAP is determined by the downlink interval usage code (DIUC), connection ID (CID), and location information (subchannel offset, symbol offset, subchannel number, symbol number) of burst. Downlink traffic intervals are divided into. On the other hand, the information elements constituting the UL-MAP message is determined by the Uplink Interval Usage Code (UIUC) for each CID (Connection ID), the location of the interval is defined by the 'duration'. Here, the use of each section is determined according to the UIUC value used in the UL-MAP, and each section starts at a point separated from the previous IE starting point by the 'duration' defined in the UL-MAP IE.

The DCD message and the UCD message are physical layer related parameters to be applied in the burst periods allocated to the downlink and the uplink, respectively, and include a modulation type and an FEC code type. In addition, it defines the necessary parameters (for example, K, R values of the R-S Code, etc.) according to various types of forward error correction codes. These parameters are given by the burst profile defined for each UIUC and DIUC in UCD and DCD, respectively.

The MAC layer of a broadband wireless access system is basically based on the DOCSIS specification, which is the cable modem standard of the MCNS consortium. Guaranteeing security according to the characteristics of the wireless system, support for various modulation schemes, and the core contents of the MAC except for other partial additions and revisions (MAC management, resource allocation methods and supported services, initialization procedures ) Is similar to the DOCSIS specification.

Service-Specific Convergence Sublayer (CS) is a layer above MAC Common Part Sublayer (CPS) that receives Protocol Data Units (PDUs) from higher layers, classification of higher layer PDUs, and higher levels based on this classification. Process the layer PDU, deliver the CS PDU to the appropriate MAC SAP and receive the CS PDU from the peer entity. In addition, the CS classifies higher layer PDUs by connection and provides a function of compressing information of a payload header or restoring the compressed header information as an optional feature.

MAC CPS maps each packet to the appropriate service flow in packet transmission between the terminal and the base station on a connection basis, and provides different levels of QoS according to the connection based service flow. The MAC PDU types defined in MAC CPS are as follows.

4A shows the format of a MAC PDU. MAC PDUs are largely divided into MAC management PDUs and user data MAC PDUs. The MAC management PDU is a payload of a predefined MAC management message for the operation of the MAC layer, and each payload is prefixed with a MAC header. And, the band request PDU required for each subscriber to dynamically request the required band in the uplink corresponds to a special type of MAC management PDU having only a header called a band request header without a separate payload. In addition, the band request header may be transmitted through a contention-based uplink band, thereby allowing a terminal not allocated an uplink band from a base station to request an uplink band. 4B shows an example of a band request header.

The packet PDU corresponding to the user data is mapped to the payload of the MAC SDU, and the MAC header and CRC (optional) are attached to form a MAC PDU. 4C illustrates a structure in which a plurality of MAC PDUs are concatenated and transmitted in one uplink burst. Each MAC PDU may be distinguished by a unique connection ID (CID), and may be concatenated with not only user PDUs but also MAC management messages and bandwidth request PDUs in the same burst.

The MAC management message consists of a field indicating the type of management message and a management message payload. Among the management messages, DCD, UCD, UL-MAP, DL-MAP, etc., as mentioned above, are representative management messages that directly define the structure, band allocation, and physical layer parameters of the frame.

The scheduling service is applied to improve the efficiency of the polling / transmission authorization process. By specifying the scheduling service and its associated QoS parameters, the base station can anticipate the required degree of delay and throughput of uplink traffic, thereby providing polling and transmit permission at appropriate times. Polling is a process in which a base station allocates bandwidth to each terminal for a bandwidth request. The types of scheduling services presented in the current specification are classified into unsolicited grant service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), and best effort (BE). Additional bandwidth allocation request is possible through piggybacking / polling, and for other types of scheduling services except UGS, bandwidth stealing of bandwidth allocated to other connections is possible within the entire band allocated for each terminal. Do.

In addition, the broadband wireless access system supports an optional Automatic Repeat Request (ARQ) protocol. The transmitted MAC SDU is transmitted in the form of a sliding window of a 'Selective Repeat ARQ' type as a plurality of ARQ fragments, and performs error detection by CRC for each fragment. For the sliding window protocol, ARQ_WINDOW_SIZE, ARQ_FRAGMENT_LIFETIME, ARQ_RETRY_TIMEOUT, etc. have parameters, and ACK or NACK is notified by the ARQ-Feedback message. The ACK is divided into 'Selective ACK', 'Cumulative ACK', and 'Cumulative with Selective ACK'. One of these three types of ARQ schemes can be defined and used by mutual agreement in a flexible manner for each connection. In the transmission of the ACK message, the ACK message may be transmitted in the form of a MAC message alone, or piggybacked on a data message transmitted from the receiver, and then transmitted to the transmitter. When the receiver receives the ARQ fragment, it sends the ACK feedback IE (Information Element) alone or in its own data to the transmitter in response.

Table 1 and Table 2 show an ARQ feedback message and an ARQ feedback IE included therein, respectively. The ACK feedback IE includes a plurality of ACK MAPs for indicating the type of ACK used and the ARQ fragment received without errors in practice. The three types of ACKs are distinguished by the form of ACK MAP for the ARQ fragment in error.

Syntax Size (bits) Notes ARQ_Feedback_Message_Format () {   Management Message Type = 33 8   ARQ_Feedback_Payload variable }

Syntax Size (bits) Notes ARQ_feedback_IE (LAST) { variable   CID 16 The ID of the connection being referenced.   LAST One 0 = More ARQ feedback IE in the list 1 = Last ARQ feedback IE in the list.   ACK Type 2 0x0 = Selective ACK entry 0x1 = Cumulative ACK entry 0x2 = Cumulative with Selective ACK entry 0x3 = Cumulative ACK with Block Sequence ACK entry   BSN 11   Number of ACK Maps 2 If ACK Type == 01, the field is reserved and set to 00.Otherwise the field indicates the number of ACK maps: 0x0 = 1, 0x1 = 2, 0x2 = 3, 0x3 = 4   if (ACK Type! = 01) {    for (i = 0; i <Number of ACK Maps + 1; i ++) {      if (ACK Type! = 3) {       Selective ACK Map 16      }      else { Start of Block Sequence ACK Map definition (16bits)      Sequence Format One Number of block sequences associated with descriptor. 0: 2block sequences 1: 3block sequences      if (Sequence Format = 0) {       Sequence ACK Map 2       Sequence 1 Length 6       Sequence 2 Length 6       Reserved One      }      else {       Sequence ACK Map 3       Sequence 1 Length 4       Sequence 2 Length 4       Sequence 3 Length 4      }     } End of Block Sequence ACK Map definition    }   } }

5A to 5C illustrate a method of configuring an ACK MAP for each type of ACK. In case of Selective ACK type, all ARQ fragments are indicated by 0 and 1 for error occurrence. In case of Cumulative ACK type, only FSN (frame sequence number) of last ARQ fragment received without error is reported. That's the way. Meanwhile, Cumulative with Selective ACK corresponds to a combination of Selective ACK and Cumulative ACK.

Next, a configuration of a multicast broadcast service (MBS) in a broadband wireless access system will be described.

Multicast Broadcast Service (MBS) is a point-to-multipoint service that transmits data from one source to multiple recipients. It provides a common radio channel for efficient use of radio resources. The same data is transmitted to multiple receivers.

6 and 7 show an example of a reference model for the MBS of the broadband wireless access system.

As shown in FIG. 6, the components for the MBS include an MBS content server, a MBS distribution server, a base station (BS), and a terminal (MSS). The MBS content server provides the MBS data to the base stations and performs authentication and distribution of the encryption key of the terminal for the MBS content. The MBS distribution server is responsible for scheduling MBS data delivered to a plurality of base stations. Optionally, the MBS distribution server can be omitted and the MBS content server can play a role of scheduling MBS data. The base station provides the MBS data received through the backbone network to the terminal through the air interface, the terminal receives the MBS data from the base station.

The MBS of the broadband wireless access system has the following characteristics.

1) Minimizing Power Consumption: The UE may minimize power consumption while receiving MBS data regardless of the current operation mode (eg, normal operation mode, sleep mode, or idle mode).

2) Mobility: The terminal is provided with a seamless MBS connection even when moving between base stations.

3) MBS Zone: MBS contents are transmitted through MBS Zones that are geographically divided, and MBS configuration information (for example, MBS connection identifier, encryption key, service identifier, etc.) can be configured differently between different MBS Zones.

4) Security: MBS content is delivered only to authorized users. The encryption key for the MAC PDU of the MBS data may be equally applied between base stations in the MBS Zone.

8A and 8B show the MBS operation of the broadband wireless access system.

(1) When the terminal tries to find the MBS contents in the idle mode, the terminal exits the idle mode and switches to the normal operation state.

(2) The terminal requests the MBS list from one or more MBS content servers through an HTTP request message.

(3) The MBS content server transmits an HTTP response message including the MBS list to the terminal. The MBS list included in the HTTP response message may include information such as the MBS content name, the multicast IP address, and the port number.

(4) The terminal acquiring the MBS information may switch to the idle mode or maintain the normal operation state.

(5) After the terminal acquires the MBS information, the terminal transmits a service generation request (DSA-REQ) message including a multicast IP address and a port number of a specific MBS content. The request message may be transmitted by the base station to the terminal.)

(6) The base station transmits a DSx-RVD message indicating the reception of the service request message to the terminal, and performs an authentication procedure for determining whether the user is suitable for receiving MBS content of the terminal.

(7) After performing the authentication procedure, the base station provides downlink service parameter information (eg, service identifier, multicast connection identifier, service quality parameter, security association identifier (SAID), etc.) to the corresponding terminal. It is included in the creation response message (DSA-RSP).

(8) The terminal transmits a key request message (PKM-REQ) to the base station to obtain an MBS key from the base station for decrypting the encrypted MBS PDU.

(9) The base station delivers a key response message (PKM-RSP) including the MBS key to the terminal.

(10) The terminal decrypts after receiving the encrypted MAC PDU for the MBS content through the key received from the base station.

Next, the MBS Zone will be described.

MBS related parameters (eg, security key, multicast connection identifier, etc.) may be set differently according to a region, and MBS content may be broadcast only within a limited area. Therefore, when the terminal receiving the MBS content moves to another base station or performs a handover, the terminal should determine whether the stored MBS information is valid and whether the terminal can continuously receive the MBS content. If the current base station provides the MBS through different parameters than the MBS information held by the terminal or does not transmit the MBS contents at all, the terminal should access the new base station to update the parameters for the MBS contents. In order to solve this problem, a broadband wireless access system operates an MBS zone in which one or more MBS providing base stations are grouped.

Base stations in the same MBS zone transmit MBS content to terminals using the same MBS parameter. Also, in order for the terminal to recognize the MBS zone, the MBS zone ID is transmitted to the terminal. The terminal can immediately check whether the current MBS parameter is valid through the MBS zone ID received from the base station, and if the terminal moves to another base station in the same MBS zone, resetting the MBS related parameter to receive the MBS data. There is no need to perform a procedure. In addition, the base stations in the same MBS zone transmits the MBS data using the same radio resources at the same time, thereby increasing the MBS data reception efficiency of the terminals through the macro diversity effect.

The following describes an operation for minimizing power consumption of a terminal receiving MBS data.

The terminal may reduce power loss during the period of receiving MBS data regardless of the current operation mode (eg, the normal operation mode, the sleep mode, or the idle mode). The DL-MAP IE included in the DL-MAP message is defined to indicate a burst transmitted in the current frame. However, the terminal must receive and decode every frame downlink map message in order to receive the broadcast type burst. In this case, power consumption cannot be reduced. However, the MBS map information element (MBS_MAP IE) tells the terminal how many frames after the MBS data burst will be delivered so that the terminal does not decode the downlink frame including the downlink map message for the frame where the MBS data is not transmitted. This allows the terminal to minimize power consumption. In particular, the MBS_MAP IE has a large power saving effect for the terminal in the sleep mode and the idle mode. Such scheduling information of the MBS data burst may be delivered through the MBS_MAP IE, which is one of the DL-MAP IEs, and may also be delivered in the form of a MAC management message such as an MBS MAP message. Tables 3 and 4 show examples of MBS_MAP IE and MBS MAP messages, respectively.

Syntax Size (bits) Notes MBS_MAP_IE {  Extended DIUC 4 MBS_MAP = 0x05  Length 4  Multicast CID 12 12 LSB of CID for multicast  MBS Zone identifier 7 MBS Zone identifier corresponds to the identifier provided by the BS at connection initiation  Macro diversity enhanced One 0 = Non Macro-Diversity enhanced zone, 1 = Macro-Diversity enhanced zone  If (Macro diversity enhanced = 1) {    Permutation 2 0b00 = PUSC permutation, 0b01 = FUSC permutation, 0b10 = Optional FUSC permutation, 0b11 = Adjacent subcarrier permutation    Idcell 6    OFDMA Symbol Offset 8 OFDMA symbol offset with respect to start of the MBS portion    Boosting 3 It is used to indicate whether boosting is used or not for MBS_MAP message 000: normal (not boosted; 001: + 6dB; 010: -6dB; 011: + 9dB; 100: + 3dB; 101: -3dB; 110: 09dB; 111: -12 dB    DIUC 4 DIUC for MBS_MAP message in MBS portion    NO. Subchannels 6 It is indicate the size of MBS_MAP message in MBS portion    NO. OFDMA symbols 2 It is indicate the size of MBS_MAP message in MBS portion   } else {    DIUC 4    OFDMA Symbol Offset 8 The offset of the OFDMA symbol in which the burst starts, measured in OFDMA symbols from beginning of the downlink frame in which the DL-MAP is transmitted.    Subchannel offset 6 The lowest index OFDMA subchannel used for carrying the burst, starting from subchannel 0.    Boosting 3 000: normal (not boosted); 001: +6 dB; 011: +9 dB 010: -6 dB; 100: +3 dB; 101: -3 dB; 110: -9 dB; 111: -12 dB;    NO. OFDMA Symbols 7    NO. Subchannels 6    Repetition Coding Indication 2 0b00-No repetition coding of 0b01-Repetition coding of 2 used 0b10-Repetition coding of 4 used 0b11-Repetition coding of 6 used

   Mext MBS Frame offset 8 The Next MBS frame offset value is lower 8 bits of the frame number in which the BS shall transmit the next BS frame.    Next MBS OFDMA Symbol offset 8 The offset of the OFDMA symbol in which the next MBs portion starts, measured in OFDMA symbols from the beginning of the downlink frame in which the MBS-MAP is transmitted.   }   if! (byte boundary) {    Padding nibble variable Padding to reach byte boundary   } }

Syntax Size (bits) Notes MBS-MAP Message Format () {  Management Message Type =? 4  Frame number 4 The frame number is identical to the frame number in the DL-MAP  MBS_DIUC_Change_Count 8  #MBS_DATA_IE 4 Number of included MBS_DATA_IE  For (i = 0; i <n; i ++) { 12 N = #MBS_DATA_IE    MBS_DATA_IE variable  } 8  #MBS_DATA_Time_Diversity_IE 4 Number of included MBS_DATA_Time_Diversity_IE  For (i = 0; i <m; i ++) { M = #MBS_DATA_Time diversity IE    MBS_DATA_Time_Diversity_IE variable  }  TLV encoding element  If (! Byte boundary) {    Padding_nibble  } 8

Table 5 shows an example of MBS_DATA_IE included in the MBS MAP message.

Syntax Size (bits) Notes MBS_DATA_IE {  MBS_MAP Type = 0 4  Multicast CID 12 12 LSB of CID for multicast  MBS_DIUC 4  OFDMA Symbol offset 8 OFDMA symbol offset with respect to start of the MBS portion  Subchannel offset 6  Boosting 3 000: normal (not boosted); 001: +6 dB; 011: +9 dB 010: -6 dB; 100: +3 dB; 101: -3 dB; 110: -9 dB; 111: -12 dB;  NO. OFDMA Symbols 7  NO. Subchannels 6  Repetition Coding Indication 2 0b00-No repetition coding of 0b01-Repetition coding of 2 used 0b10-Repetition coding of 4 used 0b11-Repetition coding of 6 used  Next MBS frame offset 8 The Next MBS frame offset value is lower 8bitgs of the frame number in which the BS shall transmit the next MBS frame  Next MBS OFDMA Symbol offset 8 The offset of the OFDMA symbol in which the next MBS portion starts, measured in OFDMA symbols from the beginning of the downlink frame in which the MBS-MAP is transmitted. } {

During the process of creating a service flow for data transmission in a broadband wireless access system, the UE and the base station establish a connection to the service flow, negotiate quality of service parameters, and determine whether to apply the ARQ protocol for the connection. Negotiate. In addition, when the transmission protocol is applied, parameters related to transmission are exchanged.

However, the prior art broadband wireless access system does not allow retransmission for the MBS connection. Therefore, there is no way to correct the UE even if the terminal environment does not receive some MBS data from the base station or an error occurs in the received data. In addition, as described in the operation description of the prior art, ARQ in the broadband wireless access system defines only transmission for the unicast connection between the terminal and the base station. This is because an appropriate burst profile (FEC coding type, modulation type) can be configured according to channel conditions based on the up-down signal quality state between the base station and the terminal, thereby increasing the reception probability upon retransmission.

However, in the case of MBS data, it is difficult to provide an appropriate burst profile to all terminals receiving MBS data because the base station transmits the broadcasted data to the corresponding terminals in the base station, not the data transmitted by the base station to the specific terminals. It is also difficult to always transmit the MBS data bursts in the most robust burst profile for efficient use of.

That is, although the base station should configure the appropriate downlink burst profile in order to deliver the MBS data to the terminal, since the feedback for the MBS connection is not defined in the prior art, the burst profile for MBS data transmission is properly configured. There was a problem that could not be. Therefore, there is a possibility that the case of not receiving MBS data according to the channel environment of each terminal may occur.

In the conventional retransmission (ARQ) scheme, when the terminal transmits feedback information to the base station, when the terminal uses an ARQ feedback MAC management message or transmits uplink data irrelevant to retransmission to the base station through another connection identifier. Piggybacked feedback information related to retransmission was delivered. In this case, the terminal should transmit the feedback information only when the base station requests the uplink band for transmitting the feedback information and receives the uplink band. Or, there is another uplink connection that is not related to retransmission, and an uplink band should be allocated to the connection. In this case, there is a problem that a procedure such as requesting an uplink band of a terminal, assigning an uplink band of a base station, and transmitting feedback information of the terminal through the allocated uplink band is required.

The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to provide a terminal with feedback on the reception of MBS data to the base station, the base station for the MBS data that the terminal has not received It is to provide a data transmission control method for the MBS that can guarantee the MBS data reception quality of the terminal by enabling the retransmission.

Another object of the present invention is to enable the terminal to transmit feedback information using a contention-based uplink slot without requesting a separate uplink band for transmitting feedback information, thereby uplink for transmitting feedback information related to retransmission. It is to provide a data transmission control method for MBS that can save radio resources and simplify the feedback process.

Yet another object of the present invention is to receive feedback information on a burst profile that a base station desires to receive from terminals receiving MBS data, for proper configuration of a burst profile (coding and modulation scheme) for MBS data transmission. Accordingly, the burst profile of the MBS data burst is appropriately configured to minimize the reception error of the MBS data of the terminal and to provide a data transmission control method for the MBS that can efficiently utilize radio resources.

In one aspect of the present invention, a method for controlling data transmission for a multicast and broadcast service in a broadband wireless access system according to the present invention includes a first step of transmitting MBS data to at least one mobile subscriber station (MSS); ; Feedback information of the MBS data transmitted from a specific terminal belonging to the at least one or more terminals (identification information of the MBS data having a reception error and coding and modulation schemes suitable for the specific terminal to receive the MBS data having the reception error) Includes information about;) a second step of receiving; And a third step of retransmitting the MBS data having the reception error to the specific terminal by using the coding and modulation scheme.

In another aspect of the present invention, a data transmission control method for a multicast and broadcast service in a broadband wireless access system according to the present invention includes: a first step of receiving MBS data transmitted from a base station; A second step of determining whether a reception error exists in the received MBS data; And identification information of the MBS data in which a reception error occurs, and information about a coding and modulation scheme suitable for the specific terminal to receive the MBS data in which the reception error occurs when a reception error exists in the received MBS data. And a third step of transmitting MBS feedback information to the base station.

In still another aspect of the present invention, a data transmission control method for a multicast and broadcast service in a broadband wireless access system according to the present invention includes a multicast broadcast service (MBS) in a broadband wireless access system. 12. A method for controlling data transmission for data, the method comprising: a first step of transmitting MBS data to at least one terminal; Receiving MBS data feedback information including information on a coding and modulation scheme suitable for receiving MBS data from at least one terminal belonging to the at least one terminal; Selecting a coding and modulation scheme suitable for transmitting the MBS data using the MBS data feedback information; And a fourth step of transmitting the MBS data to the at least one or more terminals using the selected coding and modulation scheme.

In still another aspect of the present invention, there is provided a data transmission control method for a multicast broadcast service (MBS) in a terminal of a broadband wireless access system, comprising: a first step of receiving MBS data transmitted from a base station; Determining whether to request a change in a coding and modulation scheme of the MBS data; And a request for changing the coding and modulation scheme of the received MBS data, the MBS feedback including identification information of the MBS data and information on a coding and modulation scheme suitable for the specific terminal to receive the MBS data. And a third step of transmitting information to the base station.

The construction, operation and other features of the present invention will be readily understood by the preferred embodiments of the present invention described below with reference to the accompanying drawings. 9 and 10 are flowcharts of a preferred embodiment of a data transmission control method for multicast and broadcast services in a broadband wireless access system according to the present invention.

The terminal acquires information on the corresponding MBS content from the MBS server, and obtains a connection identifier and an authentication / encryption key for the corresponding service from the base station through a service generation procedure and an authentication procedure [S10].

When the MBS service starts, the MBS server delivers MBS data to the base station, and the base station transmits the location of the MBS data burst in the current frame through an MBS MAP (MBS_MAP IE or MBS MAP message, see Tables 3 and 4). Information and coding / modulation scheme and scheduling information of the next MBS data burst are informed, and MBS data is transmitted to the terminal [S11]. The terminal receives the MBS data burst.

When the terminal receives the corresponding frame based on the scheduling information of the MBS data burst obtained from the MBS MAP, the terminal receives the MBS MAP and the MBS data as described above.

The base station continuously transmits MBS data transmitted from the MBS server to the terminal [S12]. After the terminal receives the MBS MAP [S13], it is determined whether there is a reception error in the MBS data received in the corresponding frame. If a reception error occurs, the terminal transmits feedback information of the MBS data in which the reception error has occurred to the base station. [S14].

The MBS data feedback information may include identification information of the MBS data in which a reception error occurs, information about a coding and modulation scheme suitable for the specific terminal to receive the MBS data in which the reception error occurs, and a connection identifier for transmitting the MBS data. CID: Connection ID). The MBS data may be transmitted in units of data blocks or in units of frames. When the data is transmitted in units of data blocks, a block sequence number (BSN) of the MBS data is used as identification information of MBS data in which the reception error occurs. In the case of transmission in units of frames, it is preferable to use a frame number as the identification information. FIG. 9 illustrates an example of the case in which the MBS data is transmitted in data block units, and FIG. 10 illustrates an example of the case in which the MBS data is transmitted in frame units.

The terminal feeds back information about a coding and modulation scheme suitable for receiving the MBS data in which the reception error has occurred, and the base station receives the MBS data with reference to the coding and modulation scheme fed back. By transmitting the MBS data by a coding and modulation scheme suitable for the following, the terminal can receive the transmitted MBS data without error.

The MBS data feedback information is preferably transmitted through an MBS feedback header. 11 illustrates the MBS feedback header defined for transmitting the MBS data feedback information according to an exemplary embodiment of the present invention. The following is a description of each field of the MBS feedback header shown in FIG.

1) HT (Header Type): This indicates the header type. If the value is 1, it indicates that the header is transmitted alone without payload.

2) Encryption Control (EC): Indicates whether the payload is encrypted. If the value is 0, it indicates that the payload encryption is not applied.                     

3) Type: This indicates the type of the header transmitted alone, and sets a value indicating that it is an MBS feedback header.

4) Block Sequence Number (BSN) or Frame Number (FN): This indicates a block sequence number or LSB 11 bits of the frame number of the last MBS data successfully received by the UE.

5) Selective ACK MAP: From the last MBS data block / frame successfully received, each MBS data block / frame received indicates whether there is an error, and each bit represents one MBS data block / frame. If the MBS data block / frame is received without error, the corresponding bit is set to 1.

6) Configuration Change Count (CCC): Configuration Change Count (CCC) of a Downlink Channel Descriptor (DCD) message that defines a burst profile related to 'Preferred DIUC' described below. In other words, it may be referred to as an identifier (ID) of the DCD message and may indicate a 4-bit LSB of the CCC value.

7) Preferred DIUC: This indicates a downlink burst profile (suitable coding and modulation scheme) suitable for the UE to receive.

8) Short CID: Represents an 8-bit LSB of a 16-bit connection identifier to which MBS data is delivered. Since the range of connection identifiers available for MBS data transfer is limited (for example, 0xA0 through 0xFE), LSB 8 bits can distinguish all MBS connection identifiers.                     

9) HCS (Header Check Sequence): Used to check the header for errors.

The MBS feedback header containing the MBS data feedback information is preferably transmitted to the base station through a contention based uplink band. That is, in a broadband wireless access system, there is a contention-based subchannel in which an uplink subframe can transmit a bandwidth request header in order to be allocated a channel for transmitting data in uplink. By transmitting the MBS feedback header instead of the band request header through the subchannel, the MBS data feedback information can be transmitted to the base station without requiring a separate uplink band.

As another method for transmitting the MBS data feedback information, a method of including the MBS data feedback information in a header of data transmitted by the terminal through an uplink data transmission channel allocated by the base station may also be considered.

Having received the MBS data feedback information from the terminal, the base station retransmits the MBS data blocks having a reception error to the terminal using an appropriate downlink burst profile (coding and modulation scheme) [S15]. In this case, it is preferable to use the DL_MAP IE of the general DL-MAP instead of the MBS MAP (MBS_MAP IE or MBS MAP message) as the MAP information for the retransmission data burst. The terminal receives the next MBS data by the above process.

The base station may inform the other terminal receiving the MBS data to be retransmission data by transferring the MAP information of the retransmitted MBS data to the general DL-MAP, not the MBS MAP. That is, by distinguishing the MBS data scheduled from the MBS server and the MBS data retransmitted from the base station, other terminals successfully receiving the MBS data are not affected by the retransmitted MBS data.

Hereinafter, another preferred embodiment of the present invention will be described. The embodiment described below relates to an example in which the base station allocates a dedicated uplink band capable of transmitting MBS data feedback information to the terminal. Table 6 and Table 7 show an example of an uplink map information element (UL-MAP IE) included in an uplink map (UL-MAP) to allocate an uplink band for the MBS feedback header transmission. The base station may allocate an uplink band for transmitting feedback information for each MBS connection identifier instead of a specific terminal, and the terminal may transmit MBS feedback information to the base station through the allocated contention-based uplink band.

Syntax Size (bits) Notes MBS_Feedback_IE {   Extended UIUC 4 0x0f   Length 4 Length in bytes   for (i = 0; i <N_CID; i ++) { N_CID can be derived from the value of the Length field.    CID 8 CID for MBS    UIUC 4 UIUC used for the burst    Duration 4 Indicates the duration, in units of OFDMA slots, of the allocation   } }

The following is a description of each field of the MBS feedback uplink map information element (MBS UL-MAP IE) of Table 6.

1) Extended UIUC: This indicates the type of UL Map Information Element (UL MAP IE). In the present invention, an example in which the MBS feedback information element is set by setting to 0x0f is given.

2) Length: indicates the size of uplink information element.

3) N_CID: This indicates the number of MBS connection identifiers for allocating an uplink band for transmitting MBS feedback information.

4) CID: Represents an MBS connection identifier.

5) UIUC: This indicates a burst profile (coding and modulation scheme) of an uplink burst transmitting MBS feedback information.

7) Duration: Indicates an allocated uplink slot.

However, the uplink band allocated to the burst for transmitting the MBS feedback information in the uplink map information element (UL-MAP IE) is allocated uplink slots in a cumulative form from the previous uplink map information element through 'duration'. Alternatively, by setting a symbol offset, a subchannel offset, the number of symbols, and the number of subchannels in the uplink map information element, uplink band allocation of the corresponding uplink burst is possible. .

Syntax Size (bits) Notes Feedback polling IE () {   Extended UIUC 4 0x0F   Length 4 Length in bytes of following fields   for (i = 0; i <Num_Allocations; i ++) {     CID 16     UIUC 4     Feedback type 6 Set 0b1001 for MBS Feedback     Duration 10 In OFDMA slots     Allocation_offset 3 The UL feedback shall be transmitted in the frame which is 0-8 frame delay relative to the current frame     Period (p) 2 The UL resource region is dedicated to the MSS in every 2pframe     Allocation Duration (d) 3 The allocation is valid for 10 x 2d frame starting from the frame defined by Allocation_offset If d == 0b000, the dedicated allocation is de-allocated If d == 0b111, the dedicated resource shall be valid until the BS commands to de-allocate the dedicated allocation   }   Padding bits Variable To align octet boundary }

The following is a description of each field of the feedback polling uplink map information element (Feedback polling IE) of Table 7.

1) CID: Except for transmitting MBS feedback information, 'Basic CID' of the UE is set. In case of uplink burst allocation for transmission of MBS feedback information, an MBS connection identifier is set.

2) Feedback type: Type value indicating MBS feedback is set.

3) UIUC: This indicates a burst profile (coding and modulation scheme) of an uplink burst transmitting MBS feedback information.

4) Duration: This indicates an uplink slot to be allocated.

5) Allocation_offset, Period (p), Allocation Duration (d): It is omitted when 'Feedback type' indicates MBS feedback.

Table 8 shows an example of each feedback type used in the feedback polling information element of Table 7.

12 illustrates an example of modifying and using a feedback header defined in the prior art to transmit MBS feedback information according to an embodiment of the present invention. In case that the mobile station transmits MBS feedback information through a feedback header defined in the prior art without using the MBS feedback header proposed by the present invention through an uplink slot allocated through the feedback polling information element, the feedback of FIG. Configuration Change Count (CCC) of a 'Preferred DIUC' and a Downlink Channel Descriptor (DCD) message indicating a downlink burst profile (suitable coding and modulation scheme) suitable for the UE to receive content. It can be delivered by including. In the prior art, the basic CID of the mobile terminal should be set in the CID field of the feedback header so that the feedback header can be transmitted to each mobile terminal. However, when the feedback type is MBS feedback, the corresponding MBS connection identifier is set in the connection identifier field of the feedback header instead of the basic CID of the mobile terminal.

The base station determines a downlink burst profile of MBS data transmitted thereafter based on information on a burst profile that the terminal desires to receive (in the present invention, for example, Preferred DIUC) among MBS feedback information received from the terminal. In this case, the MBS data reception error of the UEs can be reduced.

13 is a flowchart of another preferred embodiment of a data transmission control method for a multicast and broadcast service in a broadband wireless access system according to the present invention.

The terminal acquires information on the corresponding MBS content from the MBS server, and obtains a connection identifier and an authentication / encryption key for the corresponding service from the base station through a service generation procedure and an authentication procedure [S20].

When the MBS service starts, the MBS server delivers MBS data to the base station, and the base station transmits the location of the MBS data burst in the current frame through an MBS MAP (MBS_MAP IE or MBS MAP message, see Tables 3 and 4). Information and coding / modulation scheme and scheduling information of the next MBS data burst are informed, and MBS data is transmitted to the terminal [S21]. The terminal receives the MBS data burst.                     

When the terminal receives the corresponding frame based on the scheduling information of the MBS data burst obtained from the MBS MAP, the terminal receives the MBS MAP and the MBS data as described above.

The base station continuously transmits MBS data transmitted from the MBS server to the terminal [S22]. If the quality of the downlink signal received by the terminal from the base station is deteriorated [S23], if the base station transmits MBS data through a previous downlink burst profile (coding and modulation scheme), the terminal receives an error in receiving MBS data. Is generated [S24]. The terminal transmits MBS feedback information to the base station [S25].

However, even if the terminal does not receive a reception error, if the downlink burst profile of the MBS data to be received and the burst profile of the MBS data transmitted by the base station may transmit MBS feedback information to the base station. The base station transmits MBS data to one or more terminals through an appropriate burst profile based on MBS feedback information received from not only the terminal but also other terminals receiving MBS data [S26]. In the example of FIG. 13, while the UE is receiving MBS data by the burst profile with DIUC = 2, downlink signal quality (CINR) is deteriorated to inform the base station to transmit MBS data with the burst profile with DIUC = 3. Transmitting MBS feedback information [S25] and then receiving MBS data with a burst profile with DIUC = 3 [S26]. In this case, the base station may select an appropriate burst profile to transmit the MBS data by a predetermined specific algorithm according to the MBS feedback information transmitted from the terminals.                     

The MBS feedback information may include identification information of the MBS data, information about a coding and modulation scheme suitable for the specific terminal to receive the MBS data according to downlink signal quality, and a connection identifier (CID) for transmitting the MBS data. ID).

The MBS feedback information is preferably transmitted through an MBS feedback header or a feedback header of the conventional method illustrated in FIG. 12. 14 illustrates an example of the MBS feedback header defined for transmitting the MBS feedback information according to an exemplary embodiment of the present invention. The following is a description of each field of the MBS feedback header shown in FIG.

1) HT (Header Type): This indicates the header type. If the value is 1, it indicates that the header is transmitted alone without payload.

2) Encryption Control (EC): Indicates whether the payload is encrypted. If the value is 0, it indicates that the payload encryption is not applied.

3) Type: This indicates the type of the header transmitted alone, and sets a value indicating that it is an MBS feedback header.

4) RSVD (Reserved): It indicates 'Reserved' bit.

5) Configuration Change Count (CCC): Configuration Change Count (CCC) value of a Downlink Channel Descriptor (DCD) message that defines a burst profile associated with an index of a burst profile suitable for the UE to receive. Represents a 4-bit LSB.                     

6) Preferred DIUC: This indicates an index of a downlink burst profile (suitable coding and modulation scheme) suitable for the UE to receive.

7) Short CID: Represents an 8-bit LSB of a 16-bit connection identifier to which MBS data is delivered. Since the range of connection identifiers available for MBS data transfer is limited (for example, 0xA0 through 0xFE), LSB 8 bits can distinguish all MBS connection identifiers.

8) Header Check Sequence (HCS): Used to check header errors.

The operation and procedure of the UE for allocating an uplink band for the MBS feedback information transmission are the same as described in the previous embodiment.

If the base station allocates an uplink slot so that the terminal does not transmit the MBS feedback information in the form of the MBS feedback header and directly transmits only the feedback information, the terminal transmits a downlink burst suitable for the terminal to receive among the parameters of the MBS feedback header. A configuration change count (CCC) of a Preferred DIUC and a Downlink Channel Descriptor (DCD) message indicating a profile (proper coding and modulation scheme) may be directly transmitted.

In the present invention, the method of transmitting the feedback information of the terminal for transmitting the MBS data and the method of transmitting the MBS data of the base station can be applied regardless of the operation mode (normal operation mode, sleep mode, idle mode) of the mobile terminal.

It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

According to the present invention, when a terminal receiving MBS (multicast and broadcast service) data in a broadband wireless access system encounters a data reception error, the present invention transmits feedback information on the unreceived MBS data to the base station, and the base station based on this. By transmitting MBS data to the corresponding terminal using an appropriate burst profile, the terminal can increase the reception efficiency of the MBS data and ensure the quality of service.

In addition, by allowing the terminal to transmit feedback information to the base station through a dedicated header proposed by the present invention through a contention-based uplink band without requesting a separate uplink band to the base station, an uplink band for feedback By simplifying the request and allocation process to enable fast feedback, there is an effect that can save uplink resources.

In addition, the base station may refer to configuring the subsequent MBS data burst based on the burst profile (coding and modulation scheme) information desired by the terminal among the feedback information received from the terminal, through which the appropriate downlink burst By transmitting the MBS data through the profile, there is an effect of minimizing the MBS data reception error of the terminals in the base station and enabling efficient use of radio resources for the MBS data transmission.

Claims (24)

A method of controlling data transmission for a multicast broadcast service (MBS) in a broadband wireless access system, Transmitting MBS data to at least one mobile subscriber station (MSS); MBS data feedback information transmitted from a terminal belonging to the at least one terminal (includes identification information of the MBS data having a reception error and information on a coding and modulation scheme suitable for receiving the MBS data having the reception error). Receiving a second step; And And retransmitting the MBS data in which the reception error has occurred to the specific terminal using the coding and modulation scheme. A method of controlling data transmission for a multicast broadcast service (MBS) in a broadband wireless access system, A first step of transmitting MBS data to at least one terminal; Receiving MBS data feedback information including information on a coding and modulation scheme suitable for receiving MBS data from at least one terminal belonging to the at least one terminal; Selecting a coding and modulation scheme suitable for transmitting the MBS data using the MBS data feedback information; And And transmitting the MBS data to the at least one terminal using the selected coding and modulation scheme. The method according to claim 1 or 2, The feedback information of the MBS data further includes a connection identifier (CID: Connection ID) of the MBS data. The method according to claim 1 or 2, The feedback information of the MBS data is a configuration change count (CCC) of a downlink channel descriptor (DCD) message that defines a burst profile associated with information about a coding and modulation scheme suitable for receiving the MBS data. The data retransmission control method for a multicast and broadcast service, characterized in that it further comprises (Count). The method according to claim 1 or 2, The MBS data feedback information is transmitted through a MBS feedback header (MBS feedback header), characterized in that the data transmission control method for a multicast and broadcast service. The method of claim 5, And the MBS feedback header is transmitted through a contention-based uplink band. The method of claim 5, Allocating an uplink band for transmitting the MBS feedback header to the at least one terminal; And receiving the MBS feedback header through the allocated uplink band. The method of claim 1, In the second step, the MAP information on the MBS data is a data transmission control method for multicast and broadcast services, characterized in that the MBS MAP. The method of claim 8, In the third step, MAP information on the transmitted MBS data is a general DL MAP (download MAP) characterized in that the data transmission control method for the multicast and broadcast services. The method of claim 1, The identification information of the MBS data is a block sequence number (BSN: Block Sequence No.) of the MBS data, characterized in that the data transmission control method for the multicast and broadcast services. The method of claim 1, And identification information of the MBS data is a frame number of the MBS data. A method of controlling data transmission for a multicast broadcast service (MBS) in a terminal of a broadband wireless access system, A first step of receiving MBS data transmitted from a base station; A second step of determining whether a reception error exists in the received MBS data; And If a reception error exists in the received MBS data, the identification information of the MBS data in which a reception error occurs and information about a coding and modulation scheme suitable for the specific terminal to receive the MBS data in which the reception error occurs; And a third step of transmitting MBS feedback information to the base station. A method of controlling data transmission for a multicast broadcast service (MBS) in a terminal of a broadband wireless access system, A first step of receiving MBS data transmitted from a base station; Determining whether to request a change in a coding and modulation scheme of the MBS data; And When requesting to change a coding and modulation scheme of the received MBS data, MBS feedback information including identification information of the MBS data and information on a coding and modulation scheme suitable for the specific terminal to receive the MBS data. And transmitting the data to the base station. The method according to claim 12 or 13, The MBS data feedback information further comprises a connection identifier (CID: Connection ID) of the MBS data. The method according to claim 12 or 13, The feedback information of the MBS data is a configuration change count (CCC) of a downlink channel descriptor (DCD) message that defines a burst profile associated with information about a coding and modulation scheme suitable for receiving the MBS data. The data retransmission control method for a multicast and broadcast service, characterized in that it further comprises (Count). The method according to claim 12 or 13 The MBS data feedback information is transmitted through a MBS feedback header (MBS feedback header), characterized in that the data transmission control method for a multicast and broadcast service. The method of claim 16, And the MBS feedback header is transmitted through a contention-based uplink band. The method of claim 16, Receiving an uplink band for transmitting the MBS feedback header from the base station; And transmitting the MBS feedback header through the allocated uplink band. The method of claim 12, In the first step, the MAP information on the MBS data is a data transmission control method for multicast and broadcast services, characterized in that the MBS MAP. The method of claim 12, And receiving the MBS data retransmitted by the base station in accordance with the coding and modulation scheme. The method of claim 19, MAP information on the transmitted MBS data is a general DL MAP (download MAP) characterized in that the data transmission control method for a multicast and broadcast service. The method of claim 12, The identification information of the MBS data is a block sequence number (BSN: Block Sequence No.) of the MBS data, characterized in that the data transmission control method for the multicast and broadcast services. The method of claim 12, And identification information of the MBS data is a frame number of the MBS data. The method according to claim 12 or 13, The terminal is a data transmission control method for a multicast and broadcast service, characterized in that applied to the normal operation mode, sleep mode, idle mode.

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