KR101070092B1 - Method and apparatus to improve performance in a multicarrier ｍｉｍｏ channel using the hadamard transform - Google Patents

Abstract

The Hadamard transform is used to spread data within a data block in a multicarrier MIMO system before transmission. In this way, the negative effects caused by clustering of poor subcarriers (i.e., subcarriers with low transmission coefficients due to fading) can be reduced. In at least one embodiment, a MAP-type detection technique is used to extract bit reliability from the received signal.

Multiple I / O, Hadamard Transform, Multicarrier, Wireless Communications

Description

METHOD AND APPARATUS TO IMPROVE PERFORMANCE IN A MULTICARRIER MIMO CHANNEL USING THE HADAMARD TRANSFORM}

TECHNICAL FIELD The present invention generally relates to wireless communication, and more particularly, to a technique for improving communication performance in a wireless channel.

Multicarrier communication is a data transmission technique in which data is divided into a plurality of portions and then the portions are transmitted through several narrow narrow band carriers. In multicarrier channels, due to multipath fading, the transmission coefficients associated with one or more subcarriers may be low, while the transmission coefficients associated with other subcarriers may be high. These low transmission coefficients can result in a low quality (ie low SNR) signal that can reduce the receiver's ability to reliably demodulate and decode the data at the subcarrier's receiver. In many cases, subcarriers undergoing bad fading are generated in the cluster.

One technique for reducing the effects of multipath fading is known as multiple inputs, multiple outputs, or MIMO. MIMO is a wireless communication technology that uses multiple antennas at each end (or at least one end) of a communication channel to provide a multi-space channel through which signals can pass. MIMO has a relatively independent fading characteristic and spreads the signal over multiple channels, thus reducing the negative effects of fading. However, even if MIMO is used, the bit error rate may still be too high due to impulse or frequency noise affecting part or all of the channel at the same time. There is a need for new techniques to effectively deal with fading in MIMO-based systems.

1 is a block diagram illustrating one example of a wireless transmitter system, in accordance with an embodiment of the invention.

2 and 3 illustrate two methods of dividing the symbols of a transmission vector into blocks according to an embodiment of the invention.

4 is a block diagram illustrating one example of a wireless receiver system in accordance with an embodiment of the present invention.

5 illustrates one example of a process for generating a list of estimated received signals for use in demodulating received signals in accordance with an embodiment of the present invention.

6 illustrates one example of a process for generating a bit probability for a received signal using a list of estimated received signals in accordance with an embodiment of the present invention.

7 is a flow diagram illustrating one example of a method for processing data transmitted on a MIMO channel in a multicarrier system in accordance with an embodiment of the present invention.

8 is a flow diagram illustrating one example of a method of processing received signals at a receiver in accordance with an embodiment of the present invention.

In the following detailed description, the invention is described with reference to the accompanying drawings, which illustrate by way of example specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. The various embodiments of the invention, although different, do not need to be mutually exclusive. For example, certain features, structures, or properties described herein in combination with one embodiment can be implemented in other embodiments without departing from the spirit and scope of the invention. Moreover, the position and order of individual elements within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, which are properly interpreted as the maximum scope of the claims and equivalents. In the drawings, like reference numerals refer to the same or similar functionality throughout the several views.

The present invention relates to a technique for performing multicarrier communication in a MIMO channel using a Hadamard transform. The Hadamard transform allows data to be spread across several subcarriers within a defined block. Since the transformation is orthogonal the data can always be extracted again. As described above, multipath fading generally affects subcarriers within the cluster. As is known, the use of the Hadamard transform can increase the likelihood that data can be extracted from a poor subcarrier because it spreads data across a group of subcarriers. In addition, effective techniques for demodulating and decoding Hadamard transformed signals at the receiver may also be provided. The techniques and structures of the present invention may be used in any multicarrier MIMO channel. In at least one embodiment, the techniques are implemented in a wireless network using a form of multicarrier communication such as orthogonal frequency division multiple access (OFDM) or orthogonal frequency division multiple access (OFDMA).

1 is a block diagram illustrating one example of a radio transmitter system 10 according to an embodiment of the present invention. The wireless transmitter system 10 may be used, for example, on a multicarrier wireless network using multiple input, multiple output (MIMO) techniques. In at least one embodiment, the wireless transmitter system 10 is used in a wireless network base station where many other applications also exist. As shown, the transmitter system 10 includes a coder 12, a modulator 14, an amadar modulator 16, a mapper 18, a space-time coder 20, first and second pilot inserters ( 22, 24, first and second inverse discrete Fourier transformers 26 and 28, first and second periodic precoding devices 30 and 32, and first and second RF transmitters 34 and 36. . One or more antennas 38, 40 may be combined with RF transmitters 34, 36 to facilitate signal transmission over a wireless channel. For example, any type of antenna may be used, including dipoles, patches, spiral antennas and / or other types of antennas, and the like. In the illustrated embodiment, two transmit antennas 38 and 40 may be used. In another embodiment, three or more transmit antennas are used in the transmission system. In at least one embodiment, one single transmitter is used.

의 벡터를 출력할 수 있다. 각 기호는 다중 반송파 신호의 하나의 부반송파를 통해 전송된다. A coder 12 receives a stream of input data bits and encodes the bits using a forward error correction (FEC) code. Any error correction code can be used. In some embodiments, FEC coding is not used. The modulator 14 receives the encoded bits (or unencoded bits if FEC is not used) and predetermined modulation techniques (e.g., binary phase shift keying (BPSK), four phase shifts). The bit is used to generate symbols according to modulation (QPSK), 16 quadrature amplitude modulation (16QAM), 64QAM, etc.). Modulator 14 is a symbol of size N

You can output a vector of. Each symbol is transmitted on one subcarrier of a multicarrier signal.

를 수신하고, 상기 기호들을 크기 M의 블록들로 나눈다. 그 다음에, 아다마르 변환기(16)는

아다마르 행렬을 이용해서 각 블록에 대해서 아다마르 변환을 수행한다. 크기 M의 블록

에 대해 아다마르 변환을 수행하면 동일한 크기의 변환 블록

가 생성된다. 그 다음에, 아다마르 변환기(16)는 각 변환 블록의 요소들을 해당 원 블록(original block)의 기호들이 차지했던 벡터

의 동일한 자리로 위치시킬 수 있다. 그 다음에, 맵퍼(18)는 아다마르 변환기(16)로부터 수신받은 기호들을 다중반송파 신호(multicarrier signal)의 톤(tones)으로 맵핑할 수 있다. Adama converter 16 receives the vector from modulator 14.

And divide the symbols into blocks of size M. Then, the adamard converter 16 is

Use the Hadamard matrix to perform Hadamard transform on each block. Block of size M

Performing a Hadamard transform on a transform block of the same size

Is generated. Then, the Adamar transformer 16 takes the elements of each transform block into a vector occupied by the symbols of the original block.

Can be placed in the same place as. The mapper 18 may then map the symbols received from the Hadamard transformer 16 to the tones of a multicarrier signal.

The space-time coder 20 receives signals output by the mapper 18 and performs MIMO-based space-time coding using the signals. Space-time coding is a technique of distributing information to be transmitted across space (ie, multiple antennas) and time, in order to achieve enhanced diversity without a significant increase in the required bandwidth. In the illustrated embodiment, the transmitter system 10 includes two transmit antennas 38 and 40, so the space-time coder 20 will use space-time codes designed for two antennas. In another embodiment, additional transmit antennas may be used with the corresponding space time codes. In another embodiment, space-time coding is not used. Pilot inserters 22 and 24 insert pilot tones into the multicarrier signal transmitted by each transmit antenna 38, 40. The pilot tone can be used at the receiver for the purpose of estimation and synchronization. Pilot tones may be distributed in frequency across a multicarrier symbol.

IDFTs 26 and 28 receive subcarriers (data subcarriers and pilot subcarriers) modulated in the frequency domain from pilot inserters 22 and 24 and convert the subcarriers into time domain representations for transmission. Then, the time domain representation can be converted from a parallel form to a serial form. For example, any kind of IDFT may be used, including fast inverse Fourier transforms (IFFTs) and / or other forms. The cyclic prefixes 30 and 32 add a cyclic prefix to the time domain signal to reduce intersymbol interference (ISI) and intercarrier interference (ICI) on the channel. The resulting signals are then converted and amplified to higher frequencies in the RF transmitters 34 and 35 and sent to the transmit antennas 38 and 40 for transmission over the MIMO channel. 1 illustrates one possible transmitter structure, in accordance with the present invention. Other structures may optionally be used.

아다마르 행렬을 이용해서 각 블록에 대해 아다마르 변환이 적용된다. 아다마르 행렬이 존재하는 경우, M은 벡터

의 크기와 같거나 작은 임의의 정수이다. 일반적으로, 사용되는 M의 값이 클수록 변환을 수행함에 있어서 보다 높은 계산 복잡도를 갖는다. 따라서, 만일 계산 전력이 부족한 경우라면, 작은 M의 값을 사용하는 것이 바람직하다. 그러나 복조/디코딩 문제들의 가능성을 줄이고, 낮은 전송 계수 부반송파의 클러스터의 영향을 분산시키기 위하여는 사용되는 M의 값이 충분히 커야 한다. As described above, in at least one embodiment, the first role of the Hadamard transformer 16 is to split the vector of symbols X into one or more blocks of size M. Then,

The Hadamard transform is applied to each block using the Hadamard matrix. If an Hadamard matrix exists, M is a vector

Any integer less than or equal to the size of. In general, the larger the value of M used, the higher the computational complexity in performing the conversion. Therefore, if the calculation power is insufficient, it is preferable to use a small value of M. However, in order to reduce the possibility of demodulation / decoding problems and to disperse the effects of clusters of low transmission coefficient subcarriers, the value of M used must be large enough.

의 기호들은 갖가지 다양한 방법으로 블록들로 분할될 수 있다. 도 2 및 도 3은 길이가 4인 블록을 사용하는 시스템에서 블록을 생성하는 2가지 방식(50, 60)을 도시한다. 도 2에 도시된 바와 같이, 한가지 가능한 접근 방법에서, 다중반송파 기호(52)의 부반송파와 관련된 기호들은, 이들이 최초에 기호로 생성되는 순서와 동일한 순서로 블록으로 분할된다. 따라서, 다중반송파 기호(52)의 첫 번째 4개의 부반송파와 관련된 기호들은 첫 번째 블록(54)을 형성하고, 다중반송파 기호(52)의 다음 4개의 부반송파와 관련된 기호들은 두 번째 블록(56)을 형성하고, 그 다음 4개의 부반송파와 관련된 기호들은 세 번째 블록(58)을 형성한다. 다른 가능한 방법으로, 도 3에 도시된 바와 같이, 원(original) 다중반송파 기호(62)의 부반송파와 관련된 기호들은 순환 순서 방식(round robin type fashion)에 따라 블록(64, 66, 68)으로 분배된다. 즉, 다중반송파 기호(62)의 첫 번째 부반송파와 관련된 기호는 첫 번째 블록(64)에 할당되고, 두 번째 부반송파와 관련된 샘플은 두 번째 블록(66)에 할당되고, 세 번째 부반송파에 관련된 샘플은 세 번째 블록(68)에 할당되고, 네 번째 부반송파에 관련된 샘플은 첫 번째 블록(64)에 할당되고, 다섯 번째 부반송파에 관련된 샘플은 두 번째 블록(66)에 할당되는 것 등과 같은 것이다. 불량 채널(bad channel)들은 일반적으로 클러스터로 그룹화되기 때문에, 전술된 바와 같이, 상기 기술은 서로 간에 멀리 떨어진 부반송파들을 각각의 블록 내에 위치시키는 것이 바람직하다. 블록을 형성하는 다른 기술들이 선택적으로 이용될 수 있다. 수신기는 원(original) 벡터

로부터 블록이 형성된 방법을 알아야 한다. In an embodiment of the invention, the vector

The symbols of may be divided into blocks in various ways. 2 and 3 show two ways 50, 60 for creating blocks in a system using blocks of length four. As shown in FIG. 2, in one possible approach, the symbols associated with the subcarriers of the multicarrier symbol 52 are divided into blocks in the same order in which they are initially created as symbols. Thus, symbols associated with the first four subcarriers of the multicarrier symbol 52 form the first block 54, and symbols associated with the next four subcarriers of the multicarrier symbol 52 represent the second block 56. And the symbols associated with the next four subcarriers form a third block 58. Alternatively, as shown in FIG. 3, symbols associated with subcarriers of the original multicarrier symbol 62 are distributed to blocks 64, 66, 68 in a round robin type fashion. do. That is, symbols associated with the first subcarrier of the multicarrier symbol 62 are assigned to the first block 64, samples associated with the second subcarrier are assigned to the second block 66, and samples associated with the third subcarrier Samples assigned to the third block 68, samples associated with the fourth subcarrier are assigned to the first block 64, samples associated with the fifth subcarrier, assigned to the second block 66, and so on. Since bad channels are generally grouped into clusters, as described above, the technique preferably places subcarriers remote from each other within each block. Other techniques of forming the block may optionally be used. Receiver is an original vector

It is necessary to know how the blocks are formed from.

In order to perform the Hadamard transform on a block of symbols, the symbols must first be sorted into a vector of M columns as follows:

은 기호들이다. 그 다음에, 변환은 다음과 같은 변환이 수행될 수 있다:here

Are symbols. Then, the conversion may be performed as follows:

은 크기 M의 아다마르 행렬이다. 상기 변환은 각 정의된 블록에 대해서 수행될 수 있다. 전술된 바와 같이, 각 변환 블록

의 요소들은, 변환 벡터

를 형성하기 위해 대응 소스 블록

의 기호들이 위치했던, 벡터

의 동일한 위치 내에서 배치될 수 있다. 아다마르 행렬은 다음을 만족하는

행렬로 정의될 수 있다. here

Is the Hadamard matrix of size M. The transformation may be performed for each defined block. As mentioned above, each transform block

The elements of the transform vector

Corresponding source block to form

The symbols of the vector

It can be arranged in the same position of. Adama matrix to satisfy

Can be defined as a matrix.

는

단위 행렬이다. 일반적으로,

아다마르 행렬은 다음과 같은 형태로 표현된다:here

Is

Unit matrix. Generally,

The Hadamard matrix is expressed in the form:

However, as long as the matrix is orthogonal, the shape of the matrix used does not matter.

를 수신할 것이다. 첫 번째 기호 시간(symbol time)에서, 시공간 코더(20)는, 안테나(38)로부터

를 전송하고, 안테나(40)로부터

를 전송한다. 그 다음 기호 시간에, 시공간 코더(20)는, 안테나(38)으로부터

을 전송하고, 안테나(40)로부터

을 전송 한다(여기서 *은 complex conjugate를 의미한다). 수신기에 있는 각 수신 안테나에 대하여, 첫 번째 및 두 번째 기호 시간에 수신된 신호들은 다음과 같다:Referring back to FIG. 1, the space-time coder 20 receives symbols from the mapper 18 and uses the space-time code for transmission from the transmit antennas 38, 40 in the transmitter system 10. Encode In at least one embodiment, the Alamouti code is used as a space time code. Since the Aramuti code for two antenna systems is used, the space-time coder 20 firstly transmits two signals to a remote receiver using the antenna 38 and the antenna 40.

Will receive. At the first symbol time, the space-time coder 20, from the antenna 38,

From the antenna 40

Send it. At the next preference time, the space-time coder 20 is moved from the antenna 38.

From the antenna 40

(Where * means complex conjugate). For each receive antenna at the receiver, the signals received at the first and second symbol times are as follows:

및

은 각각 첫 번째 및 두 번째 기호 시간에 수신된 신호들이다.

및

은 각각 안테나(38) 및 안테나(40)과 관련된 채널 전송 계수들이다. 그리고

및

은 첫 번째 및 두 번째 기호 시간에 있어서, 각 채널의 가우스 잡음(Gaussian noise)이다. 그 다음에, 수신기의 콤바이너(combiner)는 다음과 같이 전송된 신호들을 재구성할 수 있다.here

And

Are the signals received at the first and second symbol times, respectively.

And

Are channel transmission coefficients associated with antenna 38 and antenna 40, respectively. And

And

Is the Gaussian noise of each channel in the first and second symbol times. Then, the combiner of the receiver may reconstruct the transmitted signals as follows.

The combined signals from all receive antennas are the sum of the combined signals from each receive antenna. In other embodiments, space-time codes (or codes other than space-time codes) other than Araumaty codes may be used.

After transmission, the Adamar transform blocks are delivered to the receiver over a MIMO channel. Then, to extract the user data carried through it, the receiver must process the received signals. 4 is a block diagram illustrating one example of a wireless receiver system 70 that may be used to process the received signal in accordance with an embodiment of the present invention. The wireless receiver 70 may be used, for example, in a multicarrier wireless network using MIMO technology. In at least one embodiment, the wireless receiver system 70 may be used at a subscriber station of a wireless network where other applications also exist. As shown, receiver system 70 includes: first, second and third RF receivers 72, 74, and 76; First, second, and third periodic presignal removers 78, 80, 82; First, second, and third discrete Fourier transforms (DFTs) 84, 86, 88; First, second, and third channel estimators 90, 92, 94; Combiner 96; A depaper / Hadamard demodulator 98; And decoder 100. In addition, the first, second and third RF receivers 72, 74, 76 may be combined with one or more receive antennas 102, 104, 106 to facilitate receiving signals from the MIMO channel. For example, any type of antenna may be used, including dipoles, patches, spiral antennas and / or other types of antennas, and the like. Although three receive antennas 102, 104, 106 are shown, any number of receive antennas (ie, two or more) within receiver system 70 may be used.

RF receivers 72, 74, and 76 process signals received from the MIMO channel by corresponding receive antennas 102, 104, and 106. The RF receivers 72, 74, 76 may, for example, amplify the received signal and downconvert the signal to a baseband representation. The down-converted signal may also be an analog signal that requires digital conversion. Periodic prefix remover 78, 80, 82 removes the periodic prefixes from the received signal. After the cyclic prefix has been removed, the DFTs 84, 86, 88 convert the signal from the time domain representation to the frequency domain representation. Any kind of DFTs may be used, including, for example, fast Fourier transforms and / or others. Serial to parallel conversion may be performed at the inputs of the DFTs 84, 86, 88. Channel estimators 90, 92, 94 may use pilot tones in the received signals to generate channel estimates of the corresponding channels. The combiner 96 can then combine the signals received from all receive antennas in a predefined manner. If space-time coding is used at the transmitter, the combination of the received signal will be tailored to the specific space-time code used.

의 기호를 그룹화하기 위해서 송신기에서 사용된 것과 유사한 방법으로 수신된 기호인

를 크기 M의 블록들로 그룹화한다. 각 블록에 대하여, 디맵퍼/아다마르 복조기(98)는 다음의 과정을 수행할 수 있다. 우선, 기호들의 블록은 열 벡터로 표현될 수 있다.The combined signal may be input to the demapper / adamard demodulator 98. Demapper / Hadamard demodulator 98 demaps and demodulates the symbols received from the transmitter. In addition to the combined signal, the demapper / Hadamard demodulator 98 also receives channel information generated by the channel estimators 90, 92, 94. In at least one embodiment, the demapper / Hadamard demodulator 98 uses a maximum a posteriori (MAP) detection technique to demodulate the combined signal and extract bit reliability from the signal. In the preparation phase, the demapper / Hadamard demodulator 98 is a vector

Is a symbol received in a manner similar to that used by the transmitter to group

Are grouped into blocks of size M. For each block, the demapper / Hadamard demodulator 98 may perform the following process. First, the block of symbols can be represented by a column vector.

를 포함하는 길이 M의 각 가능한 벡터 Z에 대하여, 디맵퍼/아다마르 복조기(98)는 현재 블록의 기호들이 유래한 부반송파의 채널 추정치를 기초로 추정 수신 벡터를 계산할 수 있다. 그 다음에 추정 수신 벡터들에 대한 리스트가 형성될 수 있다. 소스 벡터 Z에 대한 추정 수신 벡터는 다음과 같이 계산될 수 있다.As the source sample value

For each possible vector Z of length M comprising a, the demapper / Hadamard demodulator 98 may calculate an estimated received vector based on the channel estimate of the subcarrier from which the symbols of the current block originate. Then a list can be formed for the estimated received vectors. The estimated reception vector for the source vector Z can be calculated as follows.

는 대응하는 서브채널의 제곱 크기 계수(square amplitude coefficient)이다. here

Is the square amplitude coefficient of the corresponding subchannel.

비트를 전송하며, 여기서

는 변조 방식에 따른 기호당 비트의 수를 의미한다(즉, 16 QAM에서

값은 4이다). 초기 벡터를 형성하는데 사용되었던 각 비트에 대하여, 디맵퍼/아다마르 복조기(98)는 수신 블록의 유클리디언 거리(Euclidean Distance)가 가장 가까운 벡터를 찾기 위해 리스트를 2번 검색한다. 첫 번째 검색은 원 비트 시퀀스(original bit sequence)의 관련 비트 위치가 0의 값을 가지는 추정 수신 벡터로 제한되고, 두 번째 검색은 원 비트 시퀀스의 관련 비트 위치가 1의 값을 가지는 추정 수신 벡터로 제한된다. 첫 번째 검색에서 가장 낮은 유클리디언 거리 결과값은

로 표시될 수 있고, 두 번째 검색에서 가장 낮은 유클리디언 거리 결과값은

으로 표시될 수 있다. 그 후에, 해당 비트의 신뢰도는

로 계산될 수 있다. 비트 신뢰도 값은 각 비트 위치에 대해 생성된다. 비트 신뢰도 값은 신호 맵핑에 사용된 비트를 기초로 디맵핑될 수 있다. 상술된 과정은 디코더(100)에서의 향후 처리과정에 적합한 로그 우도율(log likelihood ratio)의 관점에서 MAP의 근사값을 도출한다. 다른 실시예에 있어서, 다른 복조화 및 검출 기술들이 사용될 수 있다. Each block consists of M transform symbols. Thus, each block

Transmits bits, where

Denotes the number of bits per symbol according to the modulation scheme (i.e. at 16 QAM

Value is 4). For each bit that was used to form the initial vector, the demapper / Hadamard demodulator 98 searches the list twice to find the vector whose Euclidean distance of the receive block is closest. The first search is limited to an estimated receive vector whose relative bit position in the original bit sequence has a value of zero, and the second search is an estimated received vector whose relative bit position in the original bit sequence has a value of 1. Limited. In the first search, the lowest Euclidean distance result is

, The lowest Euclidean distance result in the second search

It may be indicated by. After that, the reliability of that bit

It can be calculated as Bit reliability values are generated for each bit position. The bit reliability value may be demapped based on the bits used for signal mapping. The above-described process derives an approximation of MAP in terms of log likelihood ratios suitable for future processing in the decoder 100. In other embodiments, other demodulation and detection techniques may be used.

의 블록(114)에 해당한다. 블록들은, 전술된 바와 같이, 변환 블록들(116)을 형성하기 위해서 아다마르 변환을 이용하여 변환될 수 있다. 각 변환 블록들이 전송되는 경우의 수신 신호(즉, 수신된 변환 블록들)를 추정하기 위해서 채널 추정 정보가 사용될 수 있다(118). 5 is a diagram illustrating one example of a process 110 for generating a list of the estimated received signals described above. As shown, process 110 may begin with a list of all possible source bit sequences 112 that may be transmitted. Each bit sequence is symbols

Corresponds to block 114. The blocks may be transformed using the Hadamard transform to form the transform blocks 116, as described above. Channel estimation information may be used to estimate a received signal (ie, received transform blocks) when each transform block is transmitted (118).

를 가지는 엔트리를 찾을 수 있다. 유사하게, 두 번째 리스트(126)에 있는 여러 엔트리 중에서 수신 블록(128)으로부터 가장 가까운 유클리디언 거리

를 가지는 엔트리를 찾을 수 있다. 그 다음에, 비트 신뢰도(130)는 상기 비트 위치에 대해

로서 계산된다. 상기 프로세스는 각 비트 위치에 대해서 반복될 수 있다. 6 is a diagram illustrating one example of a process 120 for generating a bit probability for a receive block using a list of estimated received signals in accordance with an embodiment of the present invention. The process begins with a list 122 as produced in process 110 of FIG. For each bit position, the list may be divided into two parts: having a bit sequence 124 with zeros in the bit position and having a bit sequence 126 with ones in the bit position. Receive blocks may be compared with estimated received transformed blocks in two lists 122 and 124, respectively. Euclidean distance nearest to receiving block 128 of the various entries in the first list 124

You can find an entry with. Similarly, the nearest Euclidean distance from the receiving block 128 among the various entries in the second list 126.

You can find an entry with. Then, bit reliability 130 is determined for that bit position.

Is calculated as The process can be repeated for each bit position.

7 is a flowchart illustrating one example of a method for processing data transmitted on a MIMO channel in a multicarrier system according to an embodiment of the present invention. First, the input data bits are encoded using the FEC code (block 142). Any of a variety of codes can be used. The coded bits are transformed using a predefined modulation technique to generate a symbol (block 144). In at least one embodiment, FEC encoding is not used and the original uncoded bit is modulated to form symbols. The symbols are grouped into blocks of size M (block 146). For each block, a Hadamard transform is performed to form a transform block (block 148). The transform blocks are arranged in the same way as the original blocks (block 150). The transform blocks are then transmitted on a multicarrier MIMO channel using MIMO technology (block 152). In at least one embodiment, space-time coding is used to process the transform blocks before they are sent to the channel. In some other embodiments, space-time coding is not used.

가 다중반송파 MIMO채널로부터 수신된다(블록 162). 그 다음에, 수신 벡터

의 기호들은 크기 M의 블록으로 그룹화되는데, 여기서 M은 해당 수신기에서 사용하는 아다마르 행렬의 크기이다(블록 164). 그 다음에, 첫 번째 블록이 프로세싱되기 위해서 선택될 수 있다(블록 166). 길이가 M인 소스 샘플 값(source sample value)의 각 가능한 벡터

에 대하여, 추정 수신 벡터는 현재 블록과 관련된 부반송파(즉, 현재 블록 내의 기호들을 수신기로 운반하는 부반송파)의 채널 추정치들에 기초하여 계산될 수 있다(블록 168). 추정 수신 벡터 정보(estimated received vector information)를 이용하여 리스트가 형성된다. 8 is a flow diagram illustrating one embodiment of a method 160 of processing received signals at a receiver in accordance with an embodiment of the present invention. First of all, vector

Is received from the multicarrier MIMO channel (block 162). Next, the receive vector

The symbols of are grouped into blocks of size M, where M is the size of the Hadamard matrix used by the receiver (block 164). The first block may then be selected for processing (block 166). Each possible vector of source sample value of length M

For, the estimated received vector may be calculated based on channel estimates of the subcarrier associated with the current block (ie, the subcarrier carrying symbols in the current block to the receiver) (block 168). A list is formed using estimated received vector information.

)를 가지는 추정 수신 벡터를 찾기 위해서 검사될 수 있다(블록 170). 각 비트 위치에 대하여, 상기 리스트는 또한 비트 시퀀스의 관련된 비트 위치에서 1의 값을 갖는 리스트 엔트리들에 대한, 실제 수신 블록에서 가장 낮은 유클리디언 거리(

)를 갖는 추정 수신 벡터를 찾기 위해서 검사될 수 있다(블록 172). 그 다음에, 각 비트 위치에 대한 비트 신뢰도는

및

의 해당 값들을 이용하여 계산될 수 있다. 예를 들어, 적어도 하나의 실시예에서, 비록 다른 계산 기술들이 선택적으로 사용될 수 있으나, 비트 신뢰도는

로 계산된다. For each bit position, the list is the lowest Euclidean distance in the actual receiving block for list entries having a value of zero at the associated bit position of the bit sequence.

May be examined to find an estimated received vector with (block 170). For each bit position, the list is also the lowest Euclidean distance in the actual receive block, for list entries having a value of 1 at the associated bit position of the bit sequence.

May be examined to find an estimated received vector with (block 172). Then, the bit reliability for each bit position is

And

It can be calculated using the corresponding values of. For example, in at least one embodiment, although other computational techniques may optionally be used, the bit reliability is

.

At this point, if there are more blocks to be processed (block 176-Y), the next block may be selected for processing (block 178). The method 160 then repeats returning to block 168. After all relevant blocks have been processed (block 176-N), the bit probability is de-mapped (block 180). The demapped bit probability can then be decoded to complete the extraction of the desired data. In the method 160 described above, several blocks are processed sequentially (sequentially). In other embodiments, blocks may be processed in parallel or in other forms.

As used herein, the term MIMO is not limited to channels using multiple transmit antennas and multiple receive antennas, but may also apply to channels using single transmit antennas and multiple receive antennas. The Adamar transform may also be used in the channel according to the embodiment according to the present invention, but space-time coding is not generally used in the above embodiments.

The features of the present invention can be used in conjunction with any wireless networking standard that uses MIMO in a multicarrier environment. For example, in at least one implementation, features of the invention can be used in a network conforming to the IEEE 802.16x wireless networking standard.

The techniques and structures of the present invention may be embodied in various forms. For example, features of the present invention include wireless laptops, palmtops, desktops, and tablet computers; Personal digital assistants (PDAs) with wireless capabilities; Cell phones and other small wireless communication devices; Pager; Satellite communication devices; A camera with a wireless function; Audio / video equipment having a wireless function; Network interface card (NIC) and other network interface structures; Base station; Wireless access point; Integrated circuits; Instructions and / or data structures stored on a machine readable medium; And / or other forms. Examples of the various types of machine readable media that can be used include floppy disks, hard disks, optical disks, compact disk reading storage (CD-ROMs), digital video disks (DVDs), Blu-ray disks, magneto-optical disks. Read-only memory (ROMs), RAM, erasable and programmable read-memory (EPROM), electrically erasable and programmable read-memory (EEPROM), magnetic or optical cards, flash memory, and / or Various types of media suitable for storing electronic instructions or data. As used herein, the term logic may include, for example, software or hardware and / or a combination of software and hardware.

The individual blocks shown in the block diagrams herein may be functional in nature and need not correspond to individual hardware components. For example, in at least one embodiment, two or more blocks in one figure are implemented as software in one or more digital processing devices. Digital processing devices include, for example, general purpose microprocessors, digital signal processors (DSPs), reduced instruction set computers (RISCs), complex instruction set computers (CISCs), field programmable gate arrays (FPGAs), application specific semiconductors (ASICs), and And / or other devices including a combination of the above. Hardware, software, palmware, and hybrid implementations can be used.

In the foregoing detailed description, for the purpose of streamlining the disclosure, various features of the invention are grouped together in one or more separate implementations. This disclosure method should not be construed as an intention that the claimed invention requires more features than are explicitly listed in each claim. Furthermore, as the claims set forth below show, aspects of the invention may be less than all features of each disclosed embodiment.

Although the present invention has been described in conjunction with specific embodiments, it is apparent that modifications and variations that can be readily understood by those skilled in the art can be made without departing from the spirit and scope of the invention. Such modifications and variations are considered to be within the scope and scope of the invention and the claims set out below.

Claims (20)

Generating symbols from a stream of input bits according to a predefined modulation scheme to form a data vector X of symbols of size n, where n is a positive integer; Grouping the symbols into blocks of size M, where M is a positive integer less than or equal to n; Transforming each block using a Hadamard matrix of size M × M to produce a transformed block of size M; Placing each element of each transform block at the same position in the data vector X as the position where the symbol was located before the Hadamard transform to form a data vector X of transform blocks; And Transmitting the transform blocks to a multiple carrier multiple input, multiple output (MIMO) channel How to include. The method of claim 1, Prior to transmitting, space-time coding the transform blocks. The method of claim 1, Wherein the input bits are forward error correction (FEC) encoded bits. The method of claim 1, Transmitting the transform blocks, Mapping symbols within the blocks to subcarriers, Inserting pilot tones, and Performing inverse discrete Fourier transform on the subcarriers How to include. The method of claim 1, Grouping the symbols into blocks of size M, Assigning symbols associated with the first M adjacent subcarriers to the first block, and Assigning symbols associated with a second M adjacent subcarriers to a second block. The method of claim 1, Grouping the symbols into blocks of size M, Assigning the symbol associated with the first subcarrier to the first block, Assigning a symbol associated with a second subcarrier adjacent to the first subcarrier to a second block, and Allocating a symbol related to a third subcarrier adjacent to the second subcarrier to a third block How to include. A modulator that generates several symbols from a stream of data bits according to a predefined modulation scheme to form a data vector X of symbols of size n, where n is a positive integer; Group the symbols into blocks of size M, perform a Hadamard transform on each of the blocks to generate a transform block of size M using a Hadamard matrix of size M × M, A Hadamard transformer that places each element of each transform block at the same location within the data vector X and at the location where the symbol was located before the Hadamard transform to form a data vector X-M is a positive integer less than or equal to n -; And Mapper for mapping the symbols of the transform block to a plurality of subcarriers / RTI > The method of claim 7, wherein And at least two transmit antennas for transmitting the transform blocks on a multicarrier MIMO channel. The method of claim 8, And a space-time coder for space-time coding the symbols of the transform blocks before transmitting from the at least two transmit antennas. The method of claim 8, And an inverse discrete Fourier transformer for each transmit antenna for converting the symbols of the transform blocks from a frequency domain representation to a time domain representation for transmission from a corresponding transmit antenna. Receiving a vector Y of a symbol of size n from a multicarrier MIMO channel, wherein the vector Y has a plurality of symbols and n is a positive integer; Grouping the symbols of the vector Y into multiple blocks of size M, where MxM is the size of the Hadamard matrix used for Hadamard transform source blocks at the corresponding transmitter, and M is a positive integer less than or equal to n; And For the first block of the multi-block, for each possible vector of source symbols of length M, calculate an estimated received vector; Generate a list using the estimated received vector; Using the list to generate bit reliability for use in decoding the vector Y How to include. The method of claim 11, Using the list, for the first bit position of the bit sequence, The smallest Euclidean distance for the first block of the listed vectors with a value of 0 at the first bit position of the corresponding source bit sequence (

First examining the list to find an estimated received vector having < RTI ID = 0.0 > The smallest Euclidean distance for the first block of the listed vectors with a value of 1 at the first bit position of the corresponding source bit sequence (

Second examining the list to find an estimated received vector having < RTI ID = 0.0 > And

And

Calculating bit reliability for the first bit position using The method comprising performing. The method of claim 12, Using the list, Repeating the first checking, the second checking, and the calculating steps for the bit positions of the bit sequence other than the first bit position. How to include more. The method of claim 11, Performing calculation, generating, and using for blocks in the multi-block other than the first block How to include more. The method of claim 11, Calculating the estimated reception vector, Using channel estimates for subcarriers associated with the first block. The method of claim 11, Computing the bit reliability for the first bit position,

Wow

Calculating the difference between. A combiner combining the signals received by multiple receive antennas from a multicarrier MIMO channel, to produce a receive vector Y of symbol n having a plurality of symbols, where n is a positive integer; And Demapper / Demodulator Including; The demapper / demodulator, Logic to divide the symbols of the received vector Y into multiple blocks of length M, where MxM is the size of the Hadamard matrix used at the corresponding transmitter, and M is a positive integer less than or equal to n; And For the first of the multiple blocks, calculate an estimated received vector for each possible vector of source symbols of length M, generate a list using the estimated received vector, and use the list to obtain bit reliability. Logic to generate / RTI > The method of claim 17, The demapper / demodulator, For other blocks in the multiblock, calculate an estimated received vector for each possible vector of source symbols of length M, generate a list using the estimated received vector, and use the list to obtain bit reliability. Logic to generate Device further comprising. The method of claim 17, The logic for generating bit reliability using the list is Of the listed vectors with a value of 0 at the first bit position of the corresponding source bit sequences, the smallest Euclidean distance for the first block (

First logic to check the list to find an estimated received vector having < RTI ID = 0.0 > Of the listed vectors with a value of 1 in the first bit position of the corresponding source bit sequences, the smallest Euclidean distance for the first block (

Second logic to check the list to find an estimated received vector with < RTI ID = 0.0 > And

And

A third logic to calculate bit reliability for the first bit position using Device further comprising. The method of claim 19, The third logic is

Wow

A device that includes logic to determine the difference between.

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