Space-time block coding systems and methods
View Patent ↗Although 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.
1. A method in a transmitter comprising:
determining a plurality of space-time coding matrices, each space-time coding matrix in the plurality of space-time coding matrices having a respective associated correlation matrix comprising a plurality of non-zero off-diagonal elements;
selecting a space-time coding matrix from the plurality of space-time coding matrices for which the associated correlation matrix has a least number of non-zero off-diagonal elements;
encoding data symbols using the selected space-time coding matrix; and
transmitting the encoded data symbols from a network element that supports wireless communication to one or more communication terminals.
2. The method of claim 1 , the method further comprising:
determining a phase rotation factor, wherein the phase rotation factor is determined to reduce values of the non-zero off-diagonal elements of the correlation matrix having the least number of non-zero off-diagonal elements, wherein the determination of the phase rotation factor comprises receiving the phase rotation factor from a communication terminal to which the data symbols are to be transmitted; and
applying the phase rotation factor to the encoded data symbols prior to transmission by the network element.
3. The method of claim 2 , wherein determining the phase rotation factor comprises:
receiving feedback information from the communication terminal to which the data symbols are to be transmitted; and
calculating the phase rotation factor based upon the feedback information.
4. The method of claim 3 , wherein the feedback information comprises a code representing a phase angle for the phase rotation factor determined on a basis of communication channel gain factors.
5. The method of claim 4 , wherein the code has a length selected from the group consisting of: 1 bit, 2 bits, and 4 bits.
6. The method of claim 1 , the method further comprising puncturing the selected space-time coding matrix, wherein encoding comprises encoding the data symbols using the punctured selected space-time coding matrix.
7. The method of claim 1 , further comprising:
receiving the encoded data symbols at a communication terminal of the one or more communication terinals;
decoding the received encoded data symbols;
determining feedback information at the communication terminal;
transmitting the feedback information from the communication terminal to the network element;
receiving the transmitted feedback information at the network element; and
determining a phase rotation factor at the network element based upon the received feedback information for use in encoding subsequent data symbols.
8. The method of claim 1 , further comprising:
receiving the encoded data symbols at a communication terminal of the one or more communication terinals;
decoding the received encoded data symbols;
determining a phase angle θ of a phase rotation factor at the communication terminal; and
transmitting the phase angle θ to the network element.
9. The method of claim 1 , wherein each of the plurality of space-time coding matrices has a form
[
F
1
F
2
…
F
M
]
,
and each correlation matrix associated with each of the plurality of space-time coding matrices has a form
R
=
∑
m
=
1
M
F
m
T
H
T
H
F
m
,
where R is a correlation matrix, and H is a matrix of channel gain factors, M≧1.
10. A method in a receiver comprising:
receiving a communication signal comprising data symbols encoded using a space-time coding matrix selected from a plurality of space-time coding matrices, the plurality of space-time coding matrices each having a respective associated correlation matrix 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;
decoding the received encoded data symbols; and
transmitting feedback information based upon the decoded data symbols to a transmitter of the communication signal for use by the transmitter in encoding subsequent data symbols.
11. The method of claim 10 , wherein the feedback information comprises a phase angle for a phase rotation factor to be applied to subsequent data symbols to reduce values of the non-zero off-diagonal elements of the correlation matrix having the least number of non-zero off-diagonal elements.
12. The method of claim 10 , wherein the feedback information comprises a code representing a phase angle.
13. The method of claim 10 , wherein the feedback information comprises communication channel gain factors for calculating a phase rotation factor applied to the subsequent data symbols to reduce values of the non-zero off-diagonal elements of the correlation matrix having the least number of non-zero off-diagonal elements.
14. The method of claim 10 , wherein each of the plurality of space-time coding matrices has a form
[
F
1
F
2
…
F
M
]
,
and each correlation matrix associated with each of the plurality of space-time coding matrices has a form
R
=
∑
m
=
1
M
F
m
T
H
T
H
F
m
,
where R is a correlation matrix, and H is a matrix of channel gain factors, M≧1.
15. A network element that supports wireless communication, the network element comprising:
a processor configured to:
determine a plurality of space-time coding matrices, each space-time coding matrix in the plurality of space-time coding matrices having a respective associated correlation matrix comprising a plurality of non-zero off-diagonal elements;
select a space-time coding matrix from the plurality of space-time coding matrices for which the associated correlation matrix has a least number of non-zero off-diagonal elements;
an encoder configured to encode data symbols using the selected space-time coding matrix; and
a transmitter configured to transmit the encoded data symbols to one or more communication terminals.
16. The network element of claim 15 , the processor further configured to:
determine a phase rotation factor, wherein the phase rotation factor is determined to reduce values of the non-zero off-diagonal elements of the correlation matrix having the least number of non-zero off-diagonal elements, wherein the determination of the phase rotation factor comprises receiving the phase rotation factor from a communication terminal of the one or more communication terminals to which the data symbols are to be transmitted; and
apply the phase rotation factor to the encoded data symbols prior to transmission of the encoded data symbols by the transmitter.
17. The network element of claim 16 , wherein determining the phase rotation factor comprises:
receiving feedback information from the communication terminal to which the encoded data symbols are to be transmitted; and
calculating the phase rotation factor based upon the feedback information received from the communication terminal.
18. The network element of claim 16 , wherein the feedback information comprises a code representing a phase angle for the phase rotation factor determined on a basis of communication channel gain factors.
19. The network element of claim 18 , wherein the code has a length selected from the group consisting of: 1 bit, 2 bits, and 4 bits.
20. The network element of claim 16 , the processor further configured to puncture the selected space-time coding matrix, wherein encoding the data symbols comprises using the punctured selected space-time coding matrix.