Efficient channel characteristics handling
A method, performed in a network node, for channel characteristics handling for an antenna array in a communication system. The antenna array has a plurality of antenna elements. The method includes obtaining geometrical relationships between any pair of antenna elements in a spatial layout of the antenna array. All pairs of antenna elements are classified into sets based on the obtained geometrical relationships, wherein all pairs of antenna elements in a set have substantially equal geometrical relationship in the spatial layout. The method includes determining a representation of channel characteristics as P(β), wherein argument β is a vector of elements, each element relating to a magnitude and/or phase of covariance between the antenna elements in the set, and P is a mapping function based on the classifying. Antenna characteristics are processed based on the representation P(β).
1. A method, performed in a network node, for channel characteristics handling for an antenna array in a communication system, the antenna array having a plurality of antenna elements, the method comprising:
obtaining geometrical relationships between any pair of antenna elements in a spatial layout of the antenna array;
classifying all pairs of antenna elements into sets based on the obtained geometrical relationships, all pairs of antenna elements in a set having substantially equal geometrical relationship in the spatial layout, a number of sets being equal to a number of unique geometrical relationships between the pairs of antenna elements;
determining a representation of channel characteristics as P(β), argument β being a vector of elements, each element relating to a covariance between the antenna elements in a set, and P being a mapping function based on the classifying, the mapping function being a matrix having a dimension equal to a total number of unique covariances and a dimension equal to a dimension of the vector β, each element of the matrix being precalculated based on at least one of the unique covariances; and
processing antenna characteristics based on the representation P(β).
2. The method according to claim 1 , wherein the step of processing antenna characteristics comprises performing a measurement on at least one signal and estimating elements of β based on the measurement.
3. The method according to claim 2 , wherein the step of performing a measurement on at least one signal is based on a processing of at least one signal representing respective at least one pair of a set obtained in the classifying.
4. The method according to claim 1 , wherein the step of processing antenna characteristics comprises transmitting information relating to β.
5. The method according to claim 4 , wherein the step of transmitting information relating to β comprises transmitting information relating to β between at least two network nodes.
6. The method according to claim 4 , wherein the step of transmitting information relating to β comprises transmitting information relating to β to a memory.
7. The method according to claim 1 , wherein the step of processing antenna characteristics comprises performing a signal processing operation involving the covariance between antenna elements, the signal processing operation being expressed as a function of the elements of β.
8. The method according to claim 7 , wherein the step of performing a signal processing operation involving the covariance between antenna elements comprises determining at least one weight vector w based on the elements of β, the weight vector w consisting of antenna weights being used to adjust magnitude and/or phase of signals to and from antenna elements of the antenna array.
9. The method according to claim 1 , wherein the step of processing antenna characteristics comprises transmitting information relating to P, the information relating to P enabling estimation of β based on a measured signal.
10. The method according to claim 9 , wherein the information relating to P comprises the representation P(β).
11. The method according to claim 9 , wherein the information relating to P comprises an indication relating to a representation P(β) stored at a receiving node.
12. The method according to claim 1 , wherein the step of determining a representation comprises an error tolerance, such that P(β)≈R within the error tolerance, wherein ≈ denotes approximately equal to, and covariance between antenna elements is represented by a covariance matrix R.
13. The method according to claim 1 , wherein P is a matrix defined by
vec{ R mn }=Pβ
wherein covariance between antenna elements is represented by a covariance matrix R mn , vec{R mn } denoting the vectorization of R mn , m and n being indices running over the number of antenna elements of the antenna array.
14. The method according to claim 1 , wherein the elements of β are real-valued.
15. A network node configured to handle channel characteristics for an antenna array, the network node comprising an antenna array, the antenna array having a plurality of antenna elements, the network node further comprising processing means configured to:
obtain geometrical relationships between any pair of antenna elements in a spatial layout of the antenna array;
classify all pairs of antenna elements into sets based on the obtained geometrical relationships, all pairs of antenna elements in a set having substantially equal geometrical relationship in the spatial layout, a number of sets being equal to a number of unique geometrical relationships between the pairs of antenna elements;
determine a representation of channel characteristics as P(β), argument β being a vector of elements, each element relating to a covariance between the antenna elements in the set, and P being a mapping function based on the classifying, the mapping function being a matrix having a dimension equal to a total number of unique covariances and a dimension equal to a dimension of the vector β, each element of the matrix being precalculated based on at least one of the unique covariances; and
process antenna characteristics based on the representation P(β).
16. The network node according to claim 15 , wherein the processing means comprises a processor and a memory, wherein the memory contains instructions executable by the processor.
17. A method, performed in a wireless device, for channel characteristics handling for an antenna array in a communication system, the antenna array having a plurality of antenna elements, the method comprising:
receiving a representation of the channel characteristics as P(β), β being a vector of elements, each element relating to a covariance between antenna elements of the antenna array and P being a mapping function based on a classifying of pairs of the antenna elements into sets, all pairs of antenna elements in a set having substantially equal geometrical relationship in a spatial layout of the antenna elements in the antenna array, a number of sets being equal to a number of unique geometrical relationships between the pairs of antenna elements, the mapping function being a matrix having a dimension equal to a total number of unique covariances and a dimension equal to a dimension of the vector β, each element of the matrix being precalculated based on at least one of the unique covariances; and
processing channel characteristics related to the antenna array based on the mapping function P( ).
18. The method according to claim 17 , wherein the processing further comprises performing a measurement on at least one signal and estimating elements of the vector β based on the performed measurement.
19. The method according to claim 17 , wherein the processing comprises transmitting information relating to elements of the vector β.
20. The method according to claim 17 , wherein the mapping function P( ) is a matrix defined by
vec{ R mn }=Pβ
wherein covariance between antenna elements is represented by a covariance matrix R mn , vec{R mn } denoting a vectorization of R mn , m and n being indices running over the number of antenna elements of the antenna array.
21. A wireless device configured for channel characteristics handling for an antenna array in a communication system, the antenna array having a plurality of antenna elements, the wireless device comprising:
a receiving module configured to receive a representation of the channel characteristics as P(β), β being a vector of elements, each element relating to a covariance between antenna elements of the antenna array and P being a mapping function based on a classifying of pairs of the antenna elements into sets, all pairs of antenna elements in a set having substantially equal geometrical relationship in a spatial layout of the antenna elements in the antenna array, a number of sets being equal to a number of unique geometrical relationships between the pairs of antenna elements, the mapping function being a matrix having a dimension equal to a total number of unique covariances and a dimension equal to a dimension of the vector β, each element of the matrix being precalculated based on at least one of the unique covariances; and
a processing module configured to process channel characteristics related to the antenna array based on the mapping function P( ).
22. The wireless device according to claim 21 , wherein the processing module is further configured to perform a measurement on at least one signal and to estimate elements of the vector β based on the performed measurement.
23. The wireless device according to claim 21 , wherein the processing module is configured to transmit information relating to elements of a vector β.