Method for channel state feedback by quantization of time-domain coefficients
The present invention relates to a channel state transmission method using time domain coefficient quantization. A terminal measures channel information in the time domain and transmits it to a base station. In this instance, a multipath frequency selective fading channel is displayed in a tapped delay line format configured with a per-path path delay value and a path gain in the time domain, differentiates a quantization level for each path gain for more efficient transmission, quantizes the same, and transmits it to a transmitter. Therefore, while the amount of bandwidths required for transmitting state information from the terminal to the base station is reduced, the base station can efficiently acquire channel state information on the entire bandwidths. Also, the base station transmits signals to many terminals through beamforming by using the acquired reliable channel state information, thereby increasing the terminal's signal receiving performance.
1. A method for a terminal to transmit channel state information with a base station to the base station, comprising:
measuring a channel state with the base station;
quantizing the measured channel state in the time domain;
including the quantized channel state information in a reference signal and transmitting the same to the base station; and
determining a plurality of quantization bits and determining a quantization interval value before the quantizing,
wherein the determining of the plurality of the quantization bits comprises determining a maximum distortion value that comprises a maximum allowable value for a first distortion value, and determining the plurality of the quantization bits based on the maximum distortion value, and
wherein the quantization interval value is determined to minimize a second distortion value.
2. The method of claim 1 , wherein, in the quantizing, the plurality of quantization bits and a quantization region for each path gain are differently set according to a statistic characteristic of the path gain for each channel path.
3. The method of claim 2 , wherein the quantizing includes:
respectively allocating the plurality of quantization bits according to the statistic characteristic of the path gain for each channel path; and
setting a quantization region based on the plurality of quantization bits.
4. The method of claim 3 , wherein the respectively allocating the plurality of quantization bits further includes:
defining the first distortion value with an average value of a squared quantization error of the time domain channel coefficient; and
determining the plurality of quantization bits for quantizing a channel coefficient of a channel path that is needed for a case in which the first distortion value is less than a predetermined maximum distortion value.
5. The method of claim 3 , wherein the setting of a quantization region includes:
determining a plurality of quantization regions based on the plurality of quantization bits;
uniformly setting the quantization interval value so as to minimize the second distortion value; and
finding a quantization boundary value and a middle value of the quantization region from the quantization interval value.
6. The method of claim 3 , further including simultaneously finding the plurality of quantization bits and the quantization interval value for minimizing the second distortion value, and using the same as the plurality of quantization bits and the quantization interval value.
7. The method of claim 6 , wherein the plurality of quantization bits and the quantization interval value are computed when the statistic characteristic of a path gain for each channel path is changed or for each predetermined period, and computed results are transmitted to the base station.
8. The method of claim 1 , wherein the measuring of the channel state includes:
estimating a channel in the frequency domain; and
taking an inverse fast Fourier transform of a value of the estimated channel in the frequency domain to acquire a time domain channel coefficient.
9. A method for a base station receiving feedback information from a terminal to acquire a channel state from the base station to the terminal, comprising:
transmitting a reference signal to the terminal through a multipath communication channel;
receiving quantized channel state information in the time domain from the terminal;
checking a channel state in the frequency domain from the received channel state information in the time domain; and
determining a plurality of quantization bits and determining a quantization interval value before the quantizing,
wherein the determining of the plurality of the quantization bits comprises determining a maximum distortion value that comprises a maximum allowable value for a first distortion value, and determining the plurality of the quantization bits based on the maximum distortion value, and
wherein the quantization interval value is determined to minimize a second distortion value.
10. The method of claim 9 , further including receiving the plurality of quantization bits and the quantization interval value of a path gain for each channel path from the base station when the channel state is changed or according to a predetermined period.
11. The method of claim 10 , wherein the method includes receiving feedback information including quantized channel state information in the time domain from the terminal, analyzing the feedback information based on the plurality of quantization bits and the quantization interval value of the path gain for each channel path, and acquiring quantized time domain channel state information.
12. The method of claim 1 , wherein the method further comprises determining a plurality of quantization regions based on the plurality of quantization bits, before the quantizing.