Dynamically adjusted OFDM channel estimation filtering in OFDM communications

1. A method of performing channel estimation in an orthogonal frequency domain multiplexing (OFDM) communications system, the method comprising:

receiving a plurality of reference signals on a plurality of subcarriers;

performing channel estimation to obtain a plurality of raw channel estimates based on the received plurality of reference signals;

determining whether a channel estimate filtering refinement is necessary based on a signal to noise ratio (SNR) measurement of the received plurality of reference signals;

determining, if the channel estimate filtering refinement is determined to be necessary, a minimum value of a filter length for the channel estimation filtering refinement; and

calculating a refined channel estimate using a number of raw channel estimates of the determined minimum value of the filter length from the plurality of raw channel estimates.

2. The method recited in claim 1 , wherein the operation of performing channel estimation includes performing channel estimation in a frequency domain.

3. The method recited in claim 1 , wherein the operation of calculating the plurality of raw channel estimates includes calculating the plurality of raw channel estimates by filtering the raw channel estimates with a filter of the determined minimum value of the filter length.

4. The method recited in claim 3 , wherein the filtering the raw channel estimates includes averaging the number of raw channel estimates.

5. The method of claim 1 , wherein the determining whether a channel estimate filtering is necessary includes comparing a required SNR in the channel estimation with an SNR in the raw channel estimates.

6. The method of claim 1 , wherein the determining of the minimum value of the filter length includes determining a minimum number of filter multiplications per raw channel estimate required to achieve the required SNR improvement.

7. An apparatus for performing channel estimation in an orthogonal frequency domain multiplexing (OFDM) communications system, the apparatus comprising:

a receiver module that receives a plurality of reference signals on a plurality of subcarriers;

a channel estimation module that performs channel estimation to obtain a plurality of raw channel estimates based on the received plurality of reference signals;

a module that determines whether a channel estimate filtering refinement is necessary based on a signal to noise ratio (SNR) measurement of the received plurality of reference signals;

a module that determines, if the channel estimate filtering refinement is determined to be necessary, a minimum value of a filter length for the channel estimation filtering refinement; and

a channel estimation refinement module that provides a refined channel estimate using a number of raw channel estimates of the determined minimum value of the filter length from the plurality of raw channel estimates.

8. The apparatus recited in claim 7 , wherein the channel estimation module is operable to perform channel estimation in a frequency domain.

9. The apparatus recited in claim 7 , wherein the channel estimation module includes a filtering module that produces the plurality of raw channel estimates by filtering the raw channel estimates with a filter of the determined minimum value of the filter length.

10. The apparatus recited in claim 9 , wherein the filtering the raw channel estimates includes averaging the number of raw channel estimates.

11. The apparatus of claim 7 , wherein the channel estimation filter module compares a required SNR in the channel estimation with an SNR in the raw channel estimates.

12. The apparatus of claim 7 , wherein the channel estimation filter module determines a minimum number of filter multiplications per raw channel estimate required to achieve the required SNR improvement.

13. A computer program product comprising a non-volatile computer readable medium having computer executable instructions stored thereon, the instructions comprising code for facilitating:

receiving a plurality of reference signals on a plurality of subcarriers;

performing channel estimation to obtain a plurality of raw channel estimates based on the received plurality of reference signals;

determining whether a channel estimate filtering refinement is necessary based on a signal to noise ratio (SNR) measurement of the received plurality of reference signals;

determining, if the channel estimate filtering refinement is determined to be necessary, a minimum value of a filter length for the channel estimation filtering refinement; and

calculating a refined channel estimate using a number of raw channel estimates of the determined minimum value of the filter length from the plurality of raw channel estimates.

14. A method of obtaining a channel estimate in a receiver, comprising:

receiving a baseband signal having a cyclic prefix and corresponding to a channel;

removing the cyclic prefix from the baseband signal;

transforming the baseband signal from a time domain to a frequency domain to yield a baseband signal in the frequency domain;

extracting a subcarrier used to transmit the baseband signal from the baseband signal in the frequency domain to yield a raw channel estimate;

determining a required signal to noise ratio for a filtered channel estimate;

determining a minimum number of filter multiplications per raw channel estimate required to achieve a required signal to noise ratio for the filtered channel estimate, wherein the minimum number of multiplications per filtered channel corresponds to a determined filter length; and

filtering the raw channel estimate with a filter of the determined filter length to yield the filtered channel estimate.

15. A method of allocating filtering resources in a receiver, comprising:

for each of a plurality of channels:

determining a required signal to noise ratio for a filtered channel estimate corresponding to the channel;

determining a minimum number of filter multiplications per raw channel estimate required to achieve a required signal to noise ratio for the filtered channel estimate, wherein the minimum number of multiplications per filtered channel corresponds to a determined filter length; and

allocating available filtering resources of a receiver in an ascending order of determined filter lengths required for each channel; and

for each channel that is allocated filtering resources, filtering the raw channel estimate with a filter of the determined filter length to yield the filtered channel estimate.

16. A receiver, comprising:

an antenna operable to receive a baseband signal having a cyclic prefix and corresponding to a channel; and

a processor in communication with the antenna, the processor operable to:

remove the cyclic prefix from the baseband signal;

transform the baseband signal from a time domain to a frequency domain to yield a baseband signal in the frequency domain;

extract a subcarrier used to transmit the baseband signal from the baseband signal in the frequency domain to yield a raw channel estimate;

determine a required signal to noise ratio for a filtered channel estimate;

determine a minimum number of filter multiplications per raw channel estimate required to achieve a required signal to noise ratio for the filtered channel estimate, wherein the minimum number of multiplications per filtered channel corresponds to a determined filter length; and

filter the raw channel estimate with a filter of the determined filter length to yield the filtered channel estimate.

17. A communication system based on orthogonal frequency domain multiplexing (OFDM) comprising:

a network of base stations that are spatially distributed in a service area to form a radio access network for wireless communication devices,

wherein each base station includes:

a receiver module that receives a plurality of reference signals on a plurality of subcarriers;

a channel estimation module that performs channel estimation to obtain a plurality of raw channel estimates based on the received plurality of reference signals;

a channel estimation filter module that determines whether a channel estimate filtering is necessary based on a required signal to noise ratio (SNR) improvement that is produced by the channel estimate filtering; and

a channel estimation refinement module that provides a refined channel estimate using the determined filter length,

wherein the channel estimation filter module determines, if the channel estimate filtering is determined necessary, a minimum value of a filter length required to achieve the required SNR improvement for the filtered channel estimate.