SPACE-TIME BLOCK CODING SYSTEMS AND METHODS

• US 20090080566A1
• Filed: 04/01/2004
• Published: 03/26/2009
• Est. Priority Date: 04/01/2004
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Kreindelin, Vitali Borisovich, Chloma, Alexandre Mikhailovich, Bakouline, Mikhail Germanovich, Tong, Wen, Zhu, Peiying, Jia, Ming
• Granted Patent: US 8,411,787 B2
• Time in Patent Office: Days
• US Class Current: 375/299
• CPC Class Codes: H04L 1/0618 Space-time coding

Abstract

Althrough orthonormal space-time coding matrices provide for optimal communication system performance in that associated correlation matrices include no non-zero off-diagonal elements, unity code rate orthonormal coding matrices are difficult to identify for arbitrary communication network equipment. According to embodiments of the present invention, non-orthonormal space-time coding matrices, for which associated correlation matrices include non-zero off-diagonal elements, are used to encode data symbols. The non-orthonormal space-time coding matrices are more easily determined, and undesirable effects of the non-zero off-diagonal components are reduced by selecting a coding matrix from among a number of such matrices. For example, a particular space-time coding matrix may be selected from a number of generated space-time coding matrices based on a number of non-zero off-diagonal elements or a power of a trace of the associated correlation matrices.

Claims

1. A method comprising:

determining a plurality of space-time coding matrices, each having a respective associated correlation matrix comprising a plurality of non-zero off-diagonal elements;

selecting one of the plurality of space-time coding matrices for which the associated correlation matrix has a least number of non-zero off-diagonal elements; and

encoding data symbols using the selected space-time coding matrix.

2. The method of claim 1, wherein the selected space-time coding matrix comprises a plurality of rows respectively corresponding to a plurality of transmit antennas and a plurality of columns respectively corresponding to a plurality of time slots in which the data symbols are to be transmitted.

3. The method of claim 2, wherein the plurality of transmit antennas comprises four transmit antennas, and wherein the plurality of space-time coding matrices comprises

$F^{\left(1\right)}$

( S ) = [ s 1 - s 2 * - s 3 * s 4 s 2 s 1 * - s 4 * - s 3 s 3 - s 4 * s 1 * - s 2 s 4 s 3 * s 2 * s 1 ] , 

F ( 2 ) 

( S ) = [ s 1 - s 3 * - s 4 * s 2 s 2 s 4 * s 3 * s 1 s 3 s 1 * - s 2 * - s 4 s 4 - s 2 * s 1 * - s 3 ] , 

F ( 3 ) 

( S ) = [ s 1 - s 4 * - s 2 * s 3 s 2 - s 3 * s 1 * - s 4 s 3 s 2 * s 4 * s 1 s 4 s 1 * - s 3 * - s 2 ] ,

matrices comprising column permutations of F⁽¹⁾ (S), F⁽²⁾ (S), or F⁽³⁾ (S), punctured matrices of F⁽¹⁾ (S), F⁽²⁾ (S), or F⁽³⁾ (S), and matrices comprising concatenations of F⁽¹⁾ (S), F⁽²⁾ (S), and F⁽³⁾ (S), where S₁, S₂, s₃, and s₄ are the data symbols.

4. The method of claim 1, further comprising:

puncturing the selected space-time coding matrix, wherein encoding comprises encoding the data symbols using the punctured selected space-time coding matrix.

5. The method of claim 4, wherein puncturing comprises puncturing the selected space-time coding matrix according to an adaptive puncturing ratio.

6. The method of claim 4, wherein the selected space-time coding matrix comprises:

$F<br><br>\left(S_1,S_2,S_3\right)=\left[\begin{array}{cccccccccccc}{s}_1& -s_2^{*}& -s_3^{*}& s_4& s_5& -s_7^{*}& -s_8^{*}& s_6& s_9& -s_{12}^{*}& -s_{10}^{*}& s_{11}\\ s_2& s_1^{*}& -s_4^{*}& -s_3& s_6& s_8^{*}& s_7^{*}& s_5& s_{10}& -s_{11}^{*}& s_9^{*}& -s_{12}\\ s_3& -s_4^{*}& s_1^{*}& -s_2& s_7& s_5^{*}& -s_6^{*}& -s_8& s_{11}& s_{10}^{*}& s_{12}^{*}& s_9\\ s_4& s_3^{*}& s_2^{*}& s_1& s_8& -s_6^{*}& s_5^{*}& -s_7& s_{12}& s_9^{*}& -s_{11}^{*}& -s_{10}\end{array}\right],$

where s₁ through S₁₂ are the data symbols.

7. The method of claim 6, wherein puncturing comprises puncturing the selected space-time coding matrix to generate a punctured matrix selected from the group consisting of:

$F<br><br>\left(S_1,S_2,S_3\right)=\left[\begin{array}{cccccc}{s}_1& -s_2^{*}& s_5& -s_7^{*}& s_9& -s_{12}^{*}\\ s_2& s_1^{*}& s_6& s_8^{*}& s_{10}& -s_{11}^{*}\\ s_3& -s_4^{*}& s_7& s_5^{*}& s_{11}& s_{10}^{*}\\ s_4& s_3^{*}& s_8& -s_6^{*}& s_{12}& s_9^{*}\end{array}\right]<br><br><br><br>\mathrm{and}$ $F<br><br>\left(S_1,S_2,S_3\right)=\left[\begin{array}{ccc}{s}_1& s_5& s_9\\ s_2& s_6& s_{10}\\ s_3& s_7& s_{11}\\ s_4& s_8& s_{12}\end{array}\right].$

8. The method of claim 1, further comprising:

determining a phase rotation factor; and

applying the phase rotation factor to the encoded data symbols, wherein the phase rotation factor is determined to reduce values of the off-diagonal elements of the correlation matrix associated with the selected space-time coding matrix.

9. The method of claim 8, wherein determining a phase rotation factor comprises receiving the phase rotation factor from a receiver to which the data symbols are to be transmitted.

10. The method of claim 8, wherein determining a phase rotation factor comprises:

receiving feedback information from a receiver to which the data symbols are to be transmitted; and

calculating the phase rotation factor based on the feedback information.

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18. A method comprising:

receiving a communication signal comprising data symbols encoded using a space-time coding matrix selected from a plurality of space-time coding matrices having respective associated correlation matrices comprising a plurality of non-zero off-diagonal elements, the associated correlation matrix for the selected space-time coding matrix having a least number of non-zero off-diagonal elements; and

decoding the encoded data symbols.

19. The method of claim 18, further comprising:

determining feedback information; and

transmitting the feedback information to a transmitter of the communication signal for use in encoding subsequent data symbols.

20. The method of claim 18, wherein decoding comprises MMSE (Minimum Mean Square Error) decoding.

21. The method of claim 19, wherein the feedback information comprises a phase angle for a phase rotation factor to be applied to the subsequent data symbols to reduce values of the off-diagonal elements of the correlation matrix associated with the selected space-time coding matrix.

22. The method of claim 21, wherein the feedback information comprises a code representing the phase angle.

23. The method of claim 21, wherein determining comprises:

determining communication channel gain factors; and

determining the phase angle based on the communication channel gain factors.

24. The method of claim 23, implemented at a receiver having N antennas and configured to receive communication signals from four antennas at the transmitter, the communication signals comprising data symbols encoded using a coding matrix selected from the group consisting of:

$F^{\left(1\right)}<br><br>\left(S\right)=\left[\begin{array}{cccc}{s}_1& -s_2^{*}& -s_3^{*}& s_4\\ s_2& s_1^{*}& -s_4^{*}& -s_3\\ s_3& -s_4^{*}& s_1^{*}& -s_2\\ s_4& s_3^{*}& s_2^{*}& s_1\end{array}\right],<br><br>F^{\left(2\right)}<br><br>\left(S\right)=\left[\begin{array}{cccc}{s}_1& -s_3^{*}& -s_4^{*}& s_2\\ s_2& s_4^{*}& s_3^{*}& s_1\\ s_3& s_1^{*}& -s_2^{*}& -s_4\\ s_4& -s_2^{*}& s_1^{*}& -s_3\end{array}\right],<br><br>F^{\left(3\right)}<br><br>\left(S\right)=\left[\begin{array}{cccc}{s}_1& -s_4^{*}& -s_2^{*}& s_3\\ s_2& -s_3^{*}& s_1^{*}& -s_4\\ s_3& s_2^{*}& s_4^{*}& s_1\\ s_4& s_1^{*}& -s_3^{*}& -s_2\end{array}\right],$

matrices comprising column permutations of F⁽¹⁾ (S), F⁽²⁾ (S), or F⁽³⁾ (S), and punctured matrices of F⁽¹⁾ (S), F⁽²⁾ (S), or F⁽³⁾ (S), where s₁, s₂, s₃, and s₄ are the data symbols;

wherein determining the phase angle comprises determining the phase angle θ

of a phase rotation factor Θ

=exp(jθ

), where

$\mathrm{\theta <br><br>}={\mathrm{\theta <br><br>}}_{1,2}=-\arg <br><br>\left\{\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>\left(h_{1,n}<br><br>h_{4,n}^{*}-h_{2,n}<br><br>h_{3,n}^{*}\right)\right\}+\mathrm{\pi <br><br>}/2$

is a phase angle for a phase rotation factor for data symbols in the first and second rows of F⁽¹⁾ (S), matrices comprising column permutations of F⁽¹⁾ (S), or punctured matrices of F⁽¹⁾ (S);

$\mathrm{\theta <br><br>}={\mathrm{\theta <br><br>}}_{1,3}=-\arg <br><br>\left\{\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>\left(h_{1,n}<br><br>h_{2,n}^{*}-h_{3,n}<br><br>h_{4,n}^{*}\right)\right\}+\mathrm{\pi <br><br>}/2$

is a phase angle for a phase rotation factor for data symbols in the first and third rows of F⁽²⁾ (S), matrices comprising column permutations of F⁽²⁾ (S), or punctured matrices of F⁽²⁾ (S); and

$\mathrm{\theta <br><br>}={\mathrm{\theta <br><br>}}_{1,4}=-\arg <br><br>\left\{\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>\left(h_{1,n}<br><br>h_{3,n}^{*}-h_{2,n}<br><br>h_{4,n}^{*}\right)\right\}+\mathrm{\pi <br><br>}/2$

is a phase angle for a phase rotation factor for data symbols in the first and fourth rows of F⁽³⁾ (S), matrices comprising column permutations of F⁽³⁾ (S), or punctured matrices of F⁽³⁾ (S); and

h_m,n comprises a communication channel gain factor associated with an m^th one of the four antennas and an n^th one of the N receiver antennas.

25. The method of claim 19, wherein the feedback information comprises communication channel gain factors for use in calculating a phase rotation factor to be applied to the subsequent data symbols to reduce values of the off-diagonal elements of the correlation matrix.

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34. A system comprising:

an input configured to receive data symbols; and

a processor configured to determine a plurality of space-time coding matrices, each having a respective associated correlation matrix comprising a plurality of non-zero off-diagonal elements, to select one of the plurality of space-time coding matrices for which the associated correlation matrix has a least number of non-zero off-diagonal elements, and to encode the data symbols using the selected space-time coding matrix.

45. The system of claim 34 implemented in a network element of a communication network, the communication network further comprising at least one receiver, wherein the processor is configured to transmit the encoded data symbols to the at least one receiver, and wherein each receiver comprises:

an input configured to receive the encoded data symbols; and

a processor configured to decode the encoded data symbols, to determine feedback information, and to transmit the feedback information to the network element for use in encoding subsequent data symbols.

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