Apparatus and method for transmitting/receiving a signal in a mobile communication system using a multiple-input multiple-output scheme
View Patent ↗In a communication system, a signal transceiver generates an upper pre-encoding symbol stream and a lower pre-encoding symbol stream by pre-encoding an upper transmission vector and a lower transmission vector according to a pre-encoding scheme when the upper and lower transmission vectors to be transmitted are input. The signal transceiver generates a space-time mapping matrix by space-time mapping the upper and lower pre-encoding symbol streams according to a space-time mapping scheme based on the number of transmit antennas to be used in the signal transceiver. The signal transceiver generates and transmits a codeword according to whether a null transmission is present in the space-time mapping matrix.
1. A method for transmitting a signal in a signal transmitter of a communication system, comprising:
generating an upper pre-encoding symbol stream and a lower pre-encoding symbol stream by pre-encoding an upper transmission vector and a lower transmission vector according to a pre-encoding scheme;
generating a space-time mapping matrix by space-time mapping the upper and lower pre-encoding symbol streams according to a space-time mapping scheme based on a number of transmit antennas to be used in the signal transmitter;
generating a codeword by multiplying the space-time mapping matrix by a unitary matrix according to whether a null transmission is present in the space-time mapping matrix; and
transmitting the codeword,
wherein the unitary matrix is set to a Hadamard unitary matrix, when the null transmission is present in the space-time mapping matrix, and is set to an identity matrix, when the null transmission is not present in the space-time mapping matrix,
wherein space-time mapping the upper and lower pre-encoding symbol streams according to the space-time mapping scheme comprises space-time mapping the upper and lower pre-encoding symbol streams using a quasi-orthogonal scheme such that the upper and lower transmission vectors are orthogonal in a unit of a predetermined number of vectors, and
wherein an upper group element and a lower group element of the codeword are separated based on a square matrix of an error matrix about the codeword.
2. The method of claim 1 , wherein pre-encoding the upper transmission vector and the lower transmission vector according to the pre-encoding scheme comprises:
pre-encoding the upper transmission vector and the lower transmission vector according to a pre-encoding matrix.
3. The method of claim 2 , wherein the pre-encoding matrix is defined by:
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where Θ N T /2 denotes the pre-encoding matrix, N T denotes the number of transmit antennas, and α t =exp(j2π(i−¾)/N T ).
4. The method of claim 1 , wherein, when the upper transmission vector is x u =[x 1 , . . . , x N T /2 ] T , the lower transmission vector is x t =[x N t /2+1 , . . . , x N T ] T , the upper pre-encoding symbol stream is s u =[s u 1 , . . . , s u N T/2 ] T =[θ l T x u , . . . , θ N T /2 T x u ] T and the lower pre-encoding symbol stream is s l =[s l 1 , . . . , s t N T/2 ] T =[θ 1 T x 1 , . . . , θ N T /2 T x 1 ] T , the space-time mapping matrix is defined by:
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where S Q-HLCP denotes the space-time mapping matrix and S Q (s u 1 , s u 2 , s t 1 , s t 2 ) is defined by:
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5. A signal transmitter for use in a communication system, comprising:
a first pre-encoder for generating an upper pre-encoding symbol stream by pre-encoding an input upper transmission vector according to a pre-encoding scheme;
a second pre-encoder for generating a lower pre-encoding symbol stream by pre-encoding an input lower transmission vector according to the pre-encoding scheme; and
a space-time mapper for generating a space-time mapping matrix by space-time mapping the upper and lower pre-encoding symbol streams according to a space-time mapping scheme based on a number of transmit antennas to be used in the signal transmitter, generating a codeword by multiplying the space-time mapping matrix by a unitary matrix according to whether a null transmission is present in the space-time mapping matrix, and transmitting the codeword,
wherein the unitary matrix is set to a Hadamard unitary matrix, when the null transmission is present in the space-time mapping matrix, and is set to an identity matrix, when the null transmission is not present in the space-time mapping matrix,
wherein the space-time mapper performs space-time mapping of the upper and lower pre-encoding symbol streams using a quasi-orthogonal scheme such that the upper and lower transmission vectors are orthogonal in a unit of a predetermined number of vectors, and
wherein an upper group element and a lower group element of the codeword are separated based on a square matrix of an error matrix about the codeword.
6. The signal transmitter of claim 5 , wherein the first pre-encoder generates the upper pre-encoding symbol stream by pre-encoding the upper transmission vector according to a pre-encoding matrix, and the second pre-encoder generates the lower pre-encoding symbol stream by pre-encoding the lower transmission vector according to the pre-encoding matrix.
7. The signal transmitter of claim 6 , wherein the pre-encoding matrix is defined by:
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where Θ N T /2 denotes the pre-encoding matrix, N T denotes the number of transmit antennas, and α l =exp(j2π(i−¾)/N T ).
8. The signal transmitter of claim 5 , wherein when the upper transmission vector is x u =[x 1 , . . . , x N T /2 ] T , the lower transmission vector is x t =[x N T /2+1 , . . . , x N T ] T , the upper pre-encoding symbol stream is s u =[s u 1 , . . . , s u N T/2 ] T =[θ 1 T x u , . . . , θ N T /2 T x u ] T and the lower pre-encoding symbol stream is s 1 =[s l 1 , . . . , s 1 N T/2 ] T =[θ l T x l , . . . , θ N T /2 T x l ] T , the space-time mapping matrix is defined by:
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