Method for sending channel quality information in a multi-carrier radio communication system, corresponding user terminal and base station
View Patent ↗The present invention relates to a method for gaining channel quality information at a base station of a multi-carrier radio communication system having a plurality of orthogonal frequency sub-carriers. According to the present invention, the method comprises the steps of: measuring a Channel Frequency Response at a user terminal of said multi-carrier radio communication channel; extracting samples of said Channel Frequency Response represented in the frequency domain at a predefined oversampling factor; sending said samples on a signaling channel from said user terminal to said base station; performing a windowing operation on the received samples in the time domain; determining a channel quality information for each of said sub-carriers on a representation in the frequency domain of said received samples after windowing operation.
1. A method for gaining channel quality information at a base station of a multi-carrier radio communication system having a plurality of orthogonal frequency sub-carriers, said method comprising the steps of:
measuring a channel frequency response at a user terminal of said multi-carrier radio communication system;
approximating said channel frequency response;
extracting N samples of said approximated channel frequency response at a predefined oversampling factor, wherein N is determined by a base station and communicated to the user terminal introducing redundancy for minimizing the error probability of a reconstructed channel frequency response;
sending said samples on a signaling channel from said user terminal to said base station;
performing a windowing operation on the received samples after transformation in into the time domain to minimize error; and
determining a channel quality information for each of said sub-carriers of said received samples after said windowing operation and transformation into the frequency domain.
2. The method according to claim 1 , wherein said channel frequency response is approximated by a real trigonometric polynomial of a predefined degree L, where L is a constant selected to provide a reliable accuracy after approximation.
3. The method according to claim 1 , wherein said channel frequency response is approximated by wavelets.
4. The method according to claim 2 , wherein the coefficients of said real trigonometric polynomial are calculated using a least squares based approximation.
5. The method according to claim 1 , further comprising quantizing said samples sending them on a high speed data packet access (HSDPA) signaling channel.
6. The method according to claim 1 , wherein said windowing operation includes multiplying said received samples with a constant if said samples are within a first time domain and with a linear function if said samples are outside of said first time domain.
7. An user terminal adapted to be used in a multi-carrier radio communication system having a plurality of orthogonal frequency sub-carriers, said user terminal comprising:
means for measuring a Channel Frequency Response;
means for approximating said Channel Frequency Response;
means for extracting N samples of said approximated Channel Frequency Response in the frequency domain at a predefined oversampling factor determined by a base station and communicated to the user terminal introducing redundancy for minimizing the error probability of a reconstructed channel frequency response; and
means for sending said samples on a signaling channel to a base station.
8. A base station adopted to be used in a multi-carrier radio communication system having a plurality of orthogonal frequency sub-carriers, said base station comprising:
means for determining an oversampling factor for use by a user terminal in extracting N samples of an approximated Channel Frequency Response in the frequency domain;
means for communicating the oversampling factor to a user terminal;
means for receiving samples of the approximated Channel Frequency Response on a signaling channel from a user terminal;
means for performing a windowing operation on the received samples after transformation into the time domain to minimize error;
means for determining a channel quality information for each of said sub-carriers of said received samples after transformation back into the frequency domain.
9. The method according to claim 4 , wherein said predefined oversampling factor N is equal to or greater than the total number of the coefficients 2L+1 of said real trigonometric polynomial.
10. The method according to claim 9 wherein the N samples are chosen equally spaced in the frequency domain corresponding to the channel frequency response frequency band.
11. The method according to claim 10 , wherein said base station determines a repartition of the N samples different than equally spaced in the frequency domain corresponding to the channel frequency response frequency band and informs the user terminal on the position in the frequency domain where the samples should be located.
12. The method according to claim 4 , wherein the coefficients are obtained by matrix multiplication:
x*=Q·b , where Q is a constant matrix defined as Q=(A T ·A) −1 A, where A is the matrix of trigonometric terms:
A
=
[
1
/
2
cos
ω
0
…
cos
L
ω
0
sin
ω
0
…
sin
L
ω
0
⋮
⋰
⋮
⋮
1
/
2
cos
ω
K
-
1
…
cos
L
ω
K
-
1
sin
ω
K
-
1
…
sin
L
ω
K
-
1
]
and, where b consists of the SIR measurements of the channel frequency response at the subcarrier positions.
13. The method according to claim 5 , further comprising the base station determining the quantization granularity and communicates it to the user terminal.
14. The method according to claim 5 , wherein the quantization granularity corresponds to a number of predefined modi.
15. The method according to claim 1 wherein the channel quality information for each of said sub-carriers is read on a curve representing the Fast Fourier Transformation of the frequency corresponding to each sub-carrier of the multi-carrier transmission system.
16. The user terminal according to claim 7 wherein said channel frequency response is approximated by a real trigonometric polynomial having 2L+1 coefficients calculated using a least squares based approximation, wherein said predefined oversampling factor N≧2L+1.
17. The user terminal according to claim 16 , wherein the coefficients are obtained by matrix multiplication:
x*=Q·b , where Q is a constant matrix defined as Q=(A T ·A) −1 A, where A is the matrix of trigonometric terms:
A
=
[
1
/
2
cos
ω
0
…
cos
L
ω
0
sin
ω
0
…
sin
L
ω
0
⋮
⋰
⋮
⋮
1
/
2
cos
ω
K
-
1
…
cos
L
ω
K
-
1
sin
ω
K
-
1
…
sin
L
ω
K
-
1
]
and, where b consists of the SIR measurements of the channel frequency response at the subcarrier positions.
18. The user terminal according to claim 7 , wherein said means for sending said samples further comprises means for sending said samples on a high speed data packet access (HSDPA) signaling channel.