Method for supporting various multi-antenna schemes in baseband wireless access system using multiple antennas

The present invention relates to a Broadband Wireless Access (hereinafter referred to as BWA) system, and more particularly, a system using an Orthogonal Frequency Division Multiple Access (hereinafter referred to as OFDMA) method. In, on methods to support a variety of multiplex antenna techniques.

Current wireless mobile communication systems are being actively realized or researched with the goal of multimedia services for high-quality, high-speed, and large-capacity data transmission. The wireless channel environment present in such a wireless mobile communication system is different from the wired channel environment in that it has multi-path interference, shadowing, radio wave attenuation, time-varying noise, and interference. The actual transmitted signal is distorted and received due to many factors such as. Here, the fading due to the multiple path interference has a close relationship with the mobility of the reflector and the user, that is, the user terminal, and is received in a form in which the actual transmission signal and the interference signal are mixed. Therefore, the received signal, unlike the actual transmitted signal, acts as a factor that eventually deteriorates the performance of the entire mobile communication system due to severe distortion.

Since the fading phenomenon can distort the amplitude and phase of the received signal, it is a main cause of interfering with high-speed data communication in a wireless channel environment, and solves the fading phenomenon. Much research is underway to do this. Therefore, in the mobile communication system, in order to transmit data at high speed, it is necessary to minimize the loss due to the characteristics of the mobile communication channel such as the fading phenomenon and the interference for each user. One of the technologies proposed to solve this is the Multiple Input Multiple Output (hereinafter referred to as "MIMO") technology.

The above-mentioned MIMO technology can be roughly classified as follows according to the data transmission method and the availability of channel information feedback (feedback).

First, there are two types of data transmission methods: Spatial Multiplexing (hereinafter referred to as'SM') technique and Spatial Diversity (hereinafter referred to as'SD') technique. The SM technique can transmit data at a higher speed without increasing the bandwidth of the system by simultaneously transmitting different data using multiple antennas of the transmitter and the receiver. It's a technique. On the other hand, the SD technique is a technique for obtaining transmission diversity by transmitting the same data with a multiple transmission antenna.

The above techniques can be classified into a closed loop method in which channel information is further fed back from a receiver to a transmitter and an open loop method in which channel information is not fed back.

On the other hand, the current standard document 802.16- of the Institute of Electrical and Electronics Engineers (hereinafter referred to as "IEEE") 802.11e, which is one of the international standardization organizations related to the above-mentioned broadband wireless connection system. With reference to REVd / D5 and REVe / D5-2004, only the plan for supporting the open-loop MIMO technology is described, but the plan for supporting the closed-loop MIMO technology is not described.

<p> In view of the above background, an object of the present invention is to provide a method for supporting various multiple antenna techniques based on MIMO technology in a wideband radio connection system using multiple antennas.</p><p> Another object of the present invention is to provide a method for constructing a MAP message capable of classifying MIMO techniques in a wideband radio connection system using multiple antennas to support various multiple antenna techniques. is there.</p><p> Another object of the present invention is to construct a downlink MAP message for efficiently providing multiple antenna technology, precoding or antenna coupling technology, antenna selection technology, etc., in which the terminal gives feedback, and various aspects are configured. The purpose is to provide a method to support the multiple antenna technique.</p>

<p> In order to achieve such an object, according to an embodiment of the present invention, various MIMO and precoding techniques are supported in a broadband wireless connection system to which a multiple input multiple output (MIMO) type antenna technique is applied. The method for this is to use the steps of constructing a downlink map message including a basic information field capable of indicating the above MIMO technology and an information field capable of indicating various precoding techniques, and using the above downlink map message. , The terminal is provided with a step of applying the above-mentioned MIMO technology.</p>

<p> According to the present invention, in a wideband wireless connection system, various basic MIMO technologies and various MIMO precoding technologies can be instructed to a terminal efficiently and with a small amount of data through a downlink map message. It has the effect of improving and increasing the cell capacity.</p>

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description, for the purpose of clarifying only the gist of the present invention, specific description of related known functions or configurations will be omitted.

The present invention proposes a method for using various Multiple Input Multiple Output (hereinafter, "MIMO") methods in a wideband wireless connection communication system using multiple antennas. In particular, the present invention proposes a new downlink map (DL-MAP) message for use in a closed loop MIMO system in an ultra-wideband communication system. The new DL-MAP message is the number of layers determined by the number of modulators and the number of output streams of the Space Time Coding (hereinafter referred to as "STC") encoder. Provide a method of selecting a transmission matrix (matrix) corresponding to (Mt). The above STC can be realized by a serial-to-parallel converter (S / P; serial-to-parallel). The transmission matrix is an IEEE 802.11 standard document with transmit diversity, vertical encoding, and horizontal encoding. It is determined in advance according to the encoding) method, and will be described in more detail below.

When the above-mentioned MIMO technology using the new DL-MAP message is applied to a broadband wireless connection communication system, it supports the closed-loop MIMO technology by using the channel quality information fed back from the mobile station, that is, the receiver. It can also be compatible with existing open-loop MIMO technology without feedback on channel quality information. Precoding can be performed using the closed-loop MIMO technique described above.

FIG. 1 shows a transmitter with a single encoder and a modulator capable of performing precoding using feedback information received from a mobile station in an ultra-wideband system according to an embodiment of the present invention. It is a figure which shows the structure.

Referring to FIG. 1, the transmitters include a encoder 102 that performs coding on the data 101 to be transmitted, a modulator 103 that maps the encoded data to a complex plane, and modulation. STC encoder 104 for applying basic MIMO technology to the data, and Mt precoding that receives Mt streams output from STC encoder 104 and performs precoding. It is equipped with a pre-coding block 105. Here, the pre-encoder 105 applies MIMO technology using the channel quality information fed back from the mobile station. The pre-encoder 105 includes a subcarrier mapping device 106 that maps the symbol output from the pre-encoder 105, and an Inverse Fast Fourier Transform for creating the mapped symbol as an OFDMA symbol. , "IFFT"), including device 107.

As mentioned above, as the transmitter has one encoder 102 and modulator 103, the number of layers will be 1 (ie L = 1) and the STC encoder 104 will output Mt symbols. To do. As described above, the MIMO technology for obtaining the diversity gain for one transmission signal in which all the above Mt output symbols are common is the transmission diversity technology. Then, for the transmission signal in which the above Mt output symbols are separated into two or more, the MIMO technology that obtains a gain in terms of the data transmission rate is vertically encoded (Vertical Encoding; VE) spatial multiplexing. It is called a chemical technology.

The pre-encoder 105 receives Mt input streams and performs an operation of multiplying by an Mt × Nt matrix. Here, the above Nt is the number of transmitting antennas.

The transmitter having such a configuration receives channel feedback information, generates a matrix value of the first encoder 105, and feedback destination coding (for example, SVD destination coding and beam formation destination coding). , Antenna grouping destination coding, and various MIMO algorithms such as antenna selection destination coding can be applied to operate.

The STC encoder 104 receives one input sequence and generates Mt output streams, and when applying the beam forming precoding technique, does not perform STC coding and leaves the Mt streams as they are. Can be output.

FIG. 2 shows a transmitter having a plurality of encoders and modulators capable of performing pre-coding using feedback information received from a mobile station in a wideband wireless connection system according to another embodiment of the present invention. It is a figure which shows the structure.

Referring to FIG. 2, the transmitter includes a plurality of encoders 202a-202n and modulators 203a-203n. Here, since the description of each function is the same as that described with reference to FIG. 1, a specific description will be omitted.

The MIMO transmission technique applied to a transmitter having a plurality of layers as described above is called a horizontally encoded (HE) spatial multiplexing (SM) technique.

On the other hand, the STC encoder 204 receives L input sequences, outputs Mt streams, and when applying the beam forming destination coding technique, does not perform STC coding and has Mt. The stream can be output as it is.

FIG. 3 is a diagram showing a method of applying a transmission matrix according to the number of layers and streams in the wideband wireless connection communication system according to the embodiment of the present invention.

Referring to FIG. 3, A, B, and C are transmission matrices. The STC encoders 104 and 204 of FIGS. 1 and 2 perform STC coding by selecting one transmission matrix in FIG. 3 according to the number of layers and the number of Mt. The row index of the transmission matrix matches the number of antennas, and the column index matches the OFDMA symbol time.

Equations (1) and (2) are sequential between the Transmit Diversity (TD) when Mt is 2 and the STC encoders 104 and 204 of Spatial Mutiplexing (SM). Indicates a matrix of input symbols.<maths num="1"><img file="JP2006141013A_D0001.tif" /></maths>

<maths num="2"><img file="JP2006141013A_D0002.tif" /></maths>

Equations (3) to (5) of the STC encoders 104 and 204 of transmit diversity (TD), hybrid (Hybrid (TD + SM)), and spatial multiplexing (SM) when Mt is 3. Shows a matrix of sequential input symbols.

<maths num="3"><img file="JP2006141013A_D0003.tif" /></maths>

<maths num="4"><img file="JP2006141013A_D0004.tif" /></maths>

<maths num="5"><img file="JP2006141013A_D0005.tif" /></maths>

Equations (6) to (8) are sequential of STC encoding units 104 and 204 of transmission diversity (TD), hybrid (Hybrid (TD + SM)), and spatial multiplexing (SM) when Mt is 4. Shows a matrix of typical input symbols.

<maths num="6"><img file="JP2006141013A_D0006.tif" /></maths>

<maths num="7"><img file="JP2006141013A_D0007.tif" /></maths>

<maths num="8"><img file="JP2006141013A_D0008.tif" /></maths>

Tables 1, 2 and 3 are the data formats of MIMO_Compact_DL-MAP messages proposed as an example in order to efficiently provide all MIMO-based techniques in accordance with embodiments of the present invention in a wideband wireless connection system. Is shown.

<tables num="1"><img file="JP2006141013A_D0009.tif" /></tables>

Table 2 shows the message fields following Table 1 separately for convenience of explanation.

<tables num="2"><img file="JP2006141013A_D0010.tif" /></tables>

Table 3 shows the message fields following Table 2 separately for convenience of explanation.

<tables num="3"><img file="JP2006141013A_D0011.tif" /></tables>

In Table 1, the first 8 bits of the MAP information element that provides control information based on MIMO indicates the type (Type) of the corresponding MAP information element of 3 bits and the sub-type (Sub-Type) of 5 bits, and the length is 4 bits. The Length field indicates the length of the control information based on the MIMO located in the next field in bytes.

Explaining the structure of the control information, the 2-bit MIMO type field is a field indicating the MIMO mode. That is, if the above MIMO type field value is '00', it means open-loop MIMO mode, and if the MIMO type field value is '01', it means antenna grouping MIMO mode, and the MIMO type field value is '10. If', it means antenna selection MIMO mode, and if the MIMO type field value is '11', it means MIMO mode that performs closed-loop destination coding.

Next, the Num_layer field is a field that indicates the number of layers, which is the number of signal branches (branch) input to the STC encoder. The Mt field is a field that indicates the number of output streams of the STC encoder. The transmitter uses the field values of the Num_layer field and the Mt field to determine the transmission matrix shown by A, B, and C in FIG. For example, if the value of the Num_layer field is '10' and the value of the Mt field is '10', the STC encoder will use an STC transmission matrix with vertical coding performed. Perform coding.

On the other hand, the Mode_Change field shown in Table 2 is a field that indicates whether or not the MIMO mode has been changed compared to before. For example, a Mode_Change value of '1' means to use a different MIMO mode than the previous MIMO mode. If the above Mode_Change value is '0', it means that the previous MIMO mode and the current MIMO mode are the same. At this time, since there is no changed information, the same MIMO type information as before Does not need to be included. Therefore, the size of the Compact DL_MAP message can be reduced.

Specifies the matrix used for open loops and the pre-coded matrix index used for closed loops when the MIMO type field values in Table 1 are specified as '00' or '11'.

Table 4 or Figure 3 below shows the possible combinations according to the number of layers and the number of streams (Mt). At the same time, among the closed-loop MIMO types, when the feedback destination coding technology is the specified MIMO type = 11, the above STC encoder is used and the index 6 bits for feedback destination coding is used. Indicates the feedback destination coding matrix. Here, the above-mentioned feedback destination coding matrix has a magnitude of Mt (number of streams) × Nt (number of transmitting antennas), and can have up to 64 mutually different matrices, and the value of the matrix is It can vary according to the generation algorithm, the number of layers, the number of streams, and the number of transmitting antennas.

<tables num="4"><img file="JP2006141013A_D0012.tif" /></tables>

When the antenna grouping technique is specified when the MIMO type field value in Table 1 is '01', the antenna destination coding matrix can be specified through the antenna grouping index 4 bits in Table 2.

Table 5 shows the matrix combinations that can be indicated by the antenna grouping index 4 bits in Table 2. Here, the number of layers and the number of streams (Mt) specified in Table 1 determine the MIMO technology to be applied preferentially in Fig. 3, and the antenna grouping index 4-bit field determines the MIMO technology to be finally applied. Is determined as shown in Table 5.

In this way, the STC coding technology of the STC coding units 104 and 204 to be applied via one 4-bit antenna grouping index field can be determined, and the analytic values of the leading coding units 105 and 205 can be known at the same time. , The overhead of the control information message can be efficiently reduced.

<tables num="5"><img file="JP2006141013A_D0013.tif" /></tables>

When the antenna selection technique is specified for the MIMO type field value of '10' in Table 1, the precoding matrix can be indicated through the 4 bits of the antenna selection index field in Table 2. This indicates the selected antenna by performing the same operation as the antenna grouping index.

In Table 2, the fields in which Nep or DIUC (Downlink Interval Usage Code) is specified are a set of encoders and modulators for the number of layers, and the coding rate and modulation method for each are indicated through 4-bit values. That is, when there are multiple layers, in the H-ARQ (Hybrid Automatic Request) additional information retransmission (IR) mode, the coding rate and modulation method are instructed by the Nep method, and the terminal is used. If there is an error in even one layer, NACK (Non ACK knowledgement) will occur, so the data in all layers will be combined so that the coding gain will be high, and the data will be retransmitted. The last field also points to CQICH channel allocation information so that if CQICH is assigned, one CQI feedback information can be placed on each layer. Each such layer uses different coding and modulation schemes and therefore requires its own CQI feedback information.

Table 3 is a field that the mobile station should refer to in order to feed back channel quality information in a structure having multiple antennas or multiple layers. CQICH_NUM, which indicates the number of feedback channels, indicates the number of feedback channels transmitted simultaneously by the mobile station. The CQI feedback type field indicating the type of feedback information transmitted in each of the feedback channels allows the mobile station to transmit different feedback information according to each assigned feedback channel. This allows MIMO technology to operate more efficiently by allowing mobile stations to transmit the diverse feedback information that base stations desire.

As described above, the transmitter, or base station, determines at least one or more of the plurality of transmission matrices, taking into account the channel quality information fed back by the receiver, ie, the mobile station. STC coding or pre-coding can be performed using the determined matrix, and the determined matrix information can be transmitted to the mobile station through the MIMO Compact DL-MAP message newly proposed in the present invention. it can. Here, the mobile station knows the above matrix information by referring to the layer value and Mt value information transmitted from the base station. Then, the mobile station can perform the decoding by using the transmission matrix corresponding to the information of the layer value and the Mt value in a state of recognizing the information as described in FIG. 3 in advance.

Although the details of the present invention have been described above based on specific embodiments, it is clear that various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention is not limited to the above-described embodiment, and should be defined by the description of the scope of claims and the equivalent of the description.

<figref num="1">It is a figure which shows the structure of the transmitter which has the single encoder and the modulator which can perform the pre-coding by using the feedback information received from the mobile station in the wide band wireless connection system by embodiment of this invention.</figref><figref num="2">FIG. 5 shows the configuration of a transmitter having a plurality of encoders and modulators capable of performing pre-coding using feedback information received from a mobile station in a wideband wireless connection system according to another embodiment of the present invention. is there.</figref><figref num="3">It is a figure which shows the method of applying the transmission matrix according to the number of layers and streams by embodiment of this invention.</figref>

Code description

101 Data 102 Coder 103 Modulator 104 STC Coder 105 Pre-Coder 106 Subcarrier Mappinger 107 Inverse Fast Fourier Transformer 202a ~ 202n Coder 203a ~ 203n Modulator 204 STC Coder