KR101255227B1 - Method for multiplexing of ack/nack bit - Google Patents

Abstract

The present invention relates to a method of transmitting a response character through frequency division multiplexing for ACK / NACK bit transmission. The present invention relates to a method of transmitting a response character in a mobile communication system supporting multiple input / output for a plurality of mobile stations. In the present invention, the mobile station using the same uplink resource block is multiplexed with only frequency division multiplexing, and the mobile station using different uplink resource blocks is multiplexed with code division multiplexing or frequency division multiplexing. In this paper, we propose an efficient ACK / NACK channel transmission method when using multi-user MIMO. When the proposed method is used, the downlink radio resource can be increased.

Cellular, Multi-user MIMO, HARQ, ACK / NACK Bits

Description

Method for transmitting response character through frequency division multiplexing for transmission of AC / NAC bit {Method for multiplexing of ack / nack bit}

1 is a diagram illustrating a cellular mobile communication system supporting multi-user MIMO in uplink according to an embodiment of the present invention.

2 is a diagram illustrating an uplink resource block according to an embodiment of the present invention.

3 is a diagram illustrating a QPSK modulation format on an ACK / NACK channel for multi-user MIMO according to an embodiment of the present invention.

4 illustrates a downlink OFDM resource unit according to an embodiment of the present invention.

5 is a diagram illustrating a method of repeatedly transmitting an ACK / NACK channel for obtaining diversity gain according to an embodiment of the present invention.

The present invention relates to an ACK / NACK transmission method for multi-user MIMO in a wireless communication system.

The present invention provides a method for efficiently using radio resources in downlink ACK / NACK transmission for uplink multi-user MIMO or uplink ACK / NACK transmission for downlink multi-user MIMO in a cellular system. .

In order to solve the above technical problem, a method for transmitting a response message through frequency division multiplexing proposed by the present invention is directed to a response message transmission method supporting an automatic retransmission request in a mobile communication system supporting multiple input / output for a plurality of mobile stations. In this case, the MSs are multiplexed with only frequency division multiplexing among mobile stations using the same uplink resource block, and the response characters multiplexed with code division multiplexing or frequency division multiplexing are transmitted between mobile stations using different uplink resource blocks.

In addition, uplink and downlink in a mobile communication system correspond to a cellular system based on an orthogonal multiplexing scheme, and the uplink resource block may include a pilot portion including data portion and channel estimation information for coherent demodulation of the data portion. Time-division multiplexed multiplexing, the mobile station using the same uplink resource block uses a sequence number of different pilots, and the channel frequency of the downlink for transmitting the response letter according to the sequence number of the pilot is different do.

In addition, the identification number of the uplink resource block used by the mobile station and the sequence number of the pilot included in the uplink resource block and the downlink code number and the resource number of the channel frequency of the downlink transmitted the response character It is characterized by implicit mapping.

Further, in the mobile communication system, an uplink resource block that can be used by the mobile station is divided into several resource block groups, and mapped to different frequencies for each uplink resource block group, and different uplink resource blocks in the uplink resource block group are used. The mobile station having the same sequence number of the pilot included in the UE maps downlink code numbers for transmitting the response signals differently, and the mobile station with different pilot sequence numbers maps the channel frequencies of the downlink channel for transmitting the response signal to each other. It is characterized by a different mapping.

The number of uplink resource blocks including pilots of the same sequence number in the uplink resource block group may be the same as the number of code numbers of the downlink.

In addition, when the maximum number of mobile stations simultaneously used in one uplink resource block on the mobile communication system is M, the identification number of the uplink resource block used by the mobile station existing on the mobile communication system and the sequence number of the pilot. Multiplexing the response signal for the M or less mobile station supporting multiple inputs and outputs according to a mapping table including mapping information of a downlink code number for transmitting the response character and a resource number of a channel frequency of the downlink; It is characterized in that the mapping to.

In addition, when the uplink resource block used by the mobile station does not support multiple inputs and outputs for a plurality of mobile stations, the uplink resource block that can be used by the mobile station in a mobile communication system is divided into a plurality of resource block groups. Each uplink resource block group may be mapped to different frequencies, and the mobile station using the uplink resource block may be differently mapped with a code number of a downlink through which the response signal is transmitted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In order to achieve this technical problem, a situation of transmitting a downlink ACK / NACK channel for uplink multi-user MIMO in a 3G LTE system will be described as an example.

In order to minimize packet error in the packet data transmission of the cellular system, the introduction of HARQ is essential. In this case, an ACK or NACK bit is transmitted on the opposite link, and an ACK is transmitted when there is no error in the received packet, and a NACK is transmitted when an error occurs.

If the NACK is received, the packet is retransmitted. If the ACK is received, the next packet is transmitted. This is called HARQ.

3G LTE provides a multi-user MIMO scheme in uplink and downlink. In this case, the same radio resource is used by a plurality of users, and the receiving end removes interference by using a well-known MIMO demodulation method and demodulates each data.

In more detail, an uplink multi-user MIMO scheme is described as an example. In a cellular system in which a plurality of antennas 101 are used in a base station 100 as shown in FIG. 1, a plurality of mobile stations use the same frequency resources when transmitting data in uplink. Send it.

1 is a diagram illustrating a cellular mobile communication system supporting multi-user MIMO in uplink according to an embodiment of the present invention.

In the case of FIG. 1, the case of two base station receiving antennas is given. In this case, the two mobile stations 110-A and 110-B transmit data using the same resources as in FIG. 2 when transmitting data to the uplinks 130-A and 130-B, respectively.

2 is a diagram illustrating an uplink resource block according to an embodiment of the present invention.

2 shows an example of radio resources when transmitting OFDMA or DFT spread OFDMA (hereinafter, referred to as DFT-S-OFDMA) scheme in uplink. The hatched portion in FIG. 2 is the time / frequency radio resource allocated to the two mobile stations.

That is, as shown in FIG. 2, two mobile stations 110-A and 110-B transmit the uplinks 130-A and 130-B using the same resource block, and the base station transmits the signals transmitted from the two mobile stations to the MIMO reception algorithm. Demodulate simultaneously using

As shown in FIG. 2, the resource block 160 (RB) includes 12 subcarriers and 14 OFDM symbol intervals in the uplink example of 3G LTE.

The resource block 160 is divided into a pilot part 140 and a data part 150. The base station transmits the scrambled pilot with different code sequences to the pilot 140 used by the two mobile stations, thereby allowing the base station to transmit the same resource from the two mobile stations. The signal received by the block can be demodulated.

The base station should transmit an ACK / NACK signal for the uplink Multi user MIMO signal, respectively. The method of the present invention provides a method of efficiently multiplexing an ACK / NACK signal for the multi-user MIMO signal.

The downlink ACK / NACK signal of the present invention is based on CDM / FDM hybrid type multiplexing, but both CDM and FDM may be used between mobile stations using different resource blocks in uplink, but using the same uplink resource block. The user MIMO mobile station is characterized in that the multiplexing only by FDM.

In addition, in the present invention, by implicitly mapping the code number and the used frequency resource number of the downlink ACK / NACK channel with the uplink resource block 160 number and the pilot sequence number, the base station needs to separately signal the mobile station. I suggest a way to not. The reason for doing so is to allow the base station system to efficiently allocate downlink ACK / NACK channel resources according to whether uplink MIMO is introduced.

3 is a diagram illustrating a QPSK modulation format on an ACK / NACK channel for multi-user MIMO according to an embodiment of the present invention.

3 shows an example of OFDM resource mapping for explaining CDM multiplexing for downlink ACK / NACK. When N is defined as the number of OFDM symbols for transmitting the ACK / NACK signal multplexed to the CDM, and M is defined as the number of subcarriers, in the example of FIG. 3, a total of NxM = 4 time-frequency symbols are used to transmit the signal. Can be used.

In FIG. 3, reference numeral 200 denotes an OFDM symbol interval and 210 denotes an OFDM subcarrier bandwidth. In the example of FIG. 3, when using different orthogonal code sequences, for example, Hadarmad codes having a length of 4, ACK / NACK signals for a total of four mobile stations can be combined and transmitted by CDM.

In the above example, four orthogonal codes are defined as C ⁽⁰⁾ = {1,1,1,1}, C ⁽¹⁾ = (1,1, -1, -1), and C ⁽²⁾ = {1 , -1, -1,1}, C ⁽³⁾ = {1, -1,1, -1}, four elements of each code are mapped to the time / frequency symbol of FIG. When four data users are used, the final transmitted signal may be represented by Equation 1 below.

In Equation 1, S _j is an ACK / NACK symbol for the j-th mobile station. For example, ACK may be a BPSK modulation symbol in which 1 Nack is transmitted as -1.

In addition, the CDM multiplexed ACK / NACK signal may be repeatedly transmitted 220 on the frequency axis to obtain a frequency diversity gain.

4 illustrates a downlink OFDM resource unit according to an embodiment of the present invention.

4 is an example of a structure repeated three times. In the example of FIG. 4, the downlink ACK / NACK channel occupies a total of 12 frequency / time OFDM symbols. In the example of FIG. 4, up to four users may be supported.

The mobile station estimates the channel using the pilot signal 210 and uses it for coherent demodulation of the ACK / NACK channel.

If the number of mobile stations exceeds four, downlink ACK / NACK multiplexing may be a hybrid form of CDM / FDM as shown in the example of FIG. 5.

5 is a diagram illustrating a method of repeatedly transmitting an ACK / NACK channel for obtaining diversity gain according to an embodiment of the present invention.

In the example of FIG. 5, a total of 16 mobile stations can be supported (assuming 3 repetitions are used as in FIG. 4).

The downlink ACK / NACK multiplexing method of the present invention is based on CDM / FDM hybrid type multiplexing, but both CDM and FDM can be used as ACK / NACK multiplexing between mobile stations using different uplink resource blocks. Multiplexing between multi-user MIMO mobile stations using FDM is characterized by multiplexing.

In addition, in the present invention, by implicitly mapping the code number and the used frequency resource number of the downlink ACK / NACK channel with the uplink resource block 160 number and the pilot sequence number, the base station needs to separately signal the mobile station. I suggest a way to not.

First, the case where the multi-user MIMO that the base station can support is 2x2 will be described. In this case, the uplink resource block is divided into a plurality of groups, and different downlink ACK / NACK frequency groups 300 to 330 are allocated to each uplink resource block group, and different resource blocks are used in the uplink resource block group. However, mobile stations having the same uplink pilot sequence number are divided into CDMs in downlink, and mobile stations having different uplink pilot sequence numbers in the uplink resource block group are divided into FDMs in downlink, that is, different downlink ACK / NACK. Allocate frequency groups (divided into 300 and 310 or 320 and 330).

The number of uplink resource blocks using the same uplink pilot sequence in the uplink resource block group is equal to the number of orthogonal codes that can be allocated to a downlink ACK / NACK channel.

Table 1 shows the code number of the ACK / NACK channel according to the present invention, assuming that 8 uplink resource blocks are available and the base station supports 2 receiving antennas, thereby enabling 2x2 multi-user MIMO per 1 uplink resource block. An example of an allocation method of a used frequency resource number, an uplink resource block 160 number, and a pilot sequence number is shown.

UL resource block group UL resource block number Uplink Pilot Sequence Number Downlink ACK / NACK Orthogonal Code Number Downlink ACK / NACK Frequency Group 0 0 0 0 A 0 One 0 C One 0 One A One One One C 2 0 2 A 2 One 2 C 3 0 3 A 3 One 3 C One 4 0 0 B 4 One 0 D 5 0 One B 5 One One D 6 0 2 B 6 One 2 D 7 0 3 B 7 One 3 D

On the other hand, there is a case where only one reception antenna exists for each base station. In this case, the corresponding cell cannot provide multi-user MIMO.

In this case, in Table 1, the base station and the mobile station only need to use a thick part. Table 1 shows a super set that can be applied to both a base station supporting 2x2 MIMO and a base station not supporting MIMO.

In this case, the ACK / NACK frequency groups C and D in FIG. 5 may be used for other channels in downlink.

As a result, both CDM and FDM may be used between mobile stations using different resource blocks in uplink, but multiplexing is performed using FDM only between multi-user MIMO mobile stations using the same uplink resource block as described above. Downlink frequency resources can be used efficiently.

On the other hand, if the multi-user MIMO that can be supported by the base station is 4x4 is shown in Table 2.

In this case, 8 uplink resource blocks are the same as in Table 1, but since 4x4 MIMO is assumed, twice the ACK / NACK frequency resources are required in the downlink than in the example of Table 1 above.

For convenience, the ACK / NACK frequency groups E to H are not shown in FIG. 5. If a base station supports only two reception antennas and uses up to 2x2 MIMO, only the bold part in Table 2 may be used.

That is, Table 2 becomes the super set of Table 1. After all, if you have only the mapping table in Table 2, you can apply to 1x1 (No multi-user MIMO), 2x2 Multi user MIMO, and 4x4 Multi-user MIMO.

UL resource block group UL resource block number Uplink Pilot Sequence Number Downlink ACK / NACK Orthogonal Code Number Downlink ACK / NACK Frequency Group 0 0 0 0 A 0 One 0 C 0 2 0 E 0 3 0 G One 0 One A One One One C One 2 One E One 3 One G 2 0 2 A 2 One 2 C 2 2 2 G 2 3 2 D 3 0 3 A 3 One 3 C 3 2 3 G 3 3 3 D One 4 0 0 B 4 One 0 D 4 2 0 F 4 3 0 H 5 0 One B 5 One One D 5 2 One F 5 3 One H 6 0 2 B 6 One 2 D 6 2 2 F 6 3 2 H 7 0 3 B 7 One 3 D 7 2 3 F 7 3 3 H

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission via the Internet) . The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

As described above, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

The method of the present invention proposes an efficient ACK / NACK channel transmission method when using multi-user MIMO, and when the proposed method is used, the efficiency of downlink radio resources can be increased.

Claims (8)

In a method of transmitting a response character supporting HARQ in a mobile communication system supporting multi-user MIMO for a plurality of mobile stations, A frequency division multiplexing multiplexing is performed between mobile stations using the same uplink resource block, and a coded multiplexing or frequency division multiplexed multiplexing response letter is transmitted between mobile stations using different uplink resource blocks. How to send a response message. The method of claim 1, Uplink and downlink of the mobile communication system corresponds to a cellular system based on orthogonal multiplexing, In the uplink resource block, a pilot portion including a data portion and channel estimation information for coherent demodulation of the data portion is time division multiplexed, A mobile station using the same uplink resource block uses sequence numbers of different pilots, and frequency division multiplexing is performed using different downlink channel frequencies for transmitting the response letters according to the pilot sequence numbers. How to send a response message. The method of claim 1, The identification number of the uplink resource block used by the mobile station and the sequence number of the pilot included in the uplink resource block are implied with the downlink code number where the response character is transmitted and the resource number of the channel frequency of the downlink ( method for transmitting a response message through frequency division multiplexing, characterized in that the mapping is implicit. The method of claim 3, wherein In the mobile communication system, the uplink resource blocks usable by the mobile station are divided into several resource block groups, and mapped to different frequencies for each uplink resource block group. A mobile station having the same sequence number of pilots included in different uplink resource blocks in the uplink resource block group maps downlink code numbers to which the response letter is transmitted differently, and among mobile stations having different pilot sequence numbers. And a method of transmitting a response character through frequency division multiplexing, characterized in that differently mapping channel frequencies of the downlinks through which the response character is transmitted. 5. The method of claim 4, And the number of uplink resource blocks including pilots of the same sequence number in the uplink resource block group is equal to the number of code numbers of the downlink. 5. The method of claim 4, When the maximum number of mobile stations simultaneously used in one uplink resource block on the mobile communication system is M, Mapping information for the identification number of the uplink resource block used by the mobile station existing on the mobile communication system, the pilot sequence number, the downlink code number for transmitting the response character, and the resource number of the channel frequency of the downlink And responsive to the response characters for the M or less mobile stations supporting multiple inputs and outputs according to the mapping table. The method of claim 3, wherein When the uplink resource block used by the mobile station does not support multiple input / output for a plurality of mobile stations, In the mobile communication system, the uplink resource blocks usable by the mobile station are divided into several resource block groups, and mapped to different frequencies for each uplink resource block group. A method of transmitting a response character through frequency division multiplexing, characterized in that the mobile station using the uplink resource block maps downlink code numbers to which the response character is transmitted. A computer-readable recording medium having recorded thereon a program for performing the method of any one of claims 1 to 7.

Images