Selectively disabling interference cancellation based on channel dispersion estimation
View Patent ↗A channel dispersion estimation algorithm(s) may be implemented within a channel length estimation module of a multi-branch equalizer processing module that disables a branch of the multi-branch equalizer processing module when the channel length or channel delay spread associated with received radio frequency (RF) bursts exceeds a predetermined threshold. The channel dispersion estimation algorithm identifies when the radio frequency (RF) bursts have a channel length or channel delay spread that can affect receiver performance. The channel length estimation module may disable interference cancellation by a branch of the multi-branch equalizer processing module in response to such a channel length or channel delay spread.
1. A multi-branch equalizer processing module operable to selectively enable interference cancellation for the processing of received radio frequency (RF) burst(s), comprising:
a first equalizer operable to be trained based upon a known training sequence, to equalize RF burst(s), and to extract data bits from the RF burst(s);
a second equalizer operable to be trained based upon at least the known training sequence, to equalize the RF burst(s), and to extract alternate data bits from RF burst(s); and
a channel length estimation module operable to determine a channel length associated with the RF burst(s) and disable the second equalizer when the channel length exceeds a predetermined channel length threshold.
2. The multi-branch equalizer processing module of claim 1 , wherein the second equalizer is further operable to be trained based upon re-encoded data bits extracted from the RF burst(s).
3. The multi-branch equalizer processing module of claim 1 , wherein the channel length estimation module is further operable to disable the second equalizer when:
a measure of the colored noise associated with the RF burst(s) exceeds a predetermined colored noise threshold; or
a signal-to-noise ratio (SNR) associated with the RF burst(s) exceeds a predetermined SNR threshold.
4. The multi-branch equalizer processing module of claim 1 , wherein the predetermined channel length threshold is less than a hilly terrain (HT) channel.
5. The multi-branch equalizer processing module of claim 1 , wherein the channel length estimation module is further operable to:
adjust a number of equalizer states for the first equalizer based on the channel length associated with the RF burst(s).
6. The multi-branch equalizer processing module of claim 1 , further comprising:
a deinterleaver operable to deinterleave the extracted data bits from the first equalizer;
a channel decoder operable to decode a frame comprised of the extracted data bits;
a re-encoder operable to re-encode the frame to produce re-encoded data bits;
an interleaver operable to interleave the re-encoded data bits and the known training sequence to produce a re-encoded burst, wherein the second equalizer is further operable to be trained based upon the re-encoded burst(s);
the deinterleaver further operable to deinterleave the alternate data bits; and
the channel decoder further operable to decode an alternate frame comprised of at least some of the alternate data bits.
7. The multi-branch equalizer processing module of claim 1 , wherein:
the received RF bursts used by the channel length estimation module examines to determine when to disable the second equalizer comprises a first set of RF bursts; and
the received RF bursts that the first equalizer and second equalizer process comprise a second set of RF bursts, wherein the first set of RF bursts preceded the second set of RF bursts; and
the sets of RF bursts comprise:
4 RF bursts; or
2 RF bursts for half rate adaptive multi-rate encoded speech.
8. A wireless terminal that comprises:
a Radio Frequency (RF) front end operable to receive RF burst(s);
a baseband processor communicatively coupled to the RF front end, wherein the baseband processor and RF front end are operable to produce a baseband signal from the RF burst(s);
a multi-branch equalizer processing module coupled to receive the baseband signal from the baseband processor, and wherein the multi-branch equalizer processing module includes a first equalizer operable to be trained based upon known training sequence(s), equalize the received RF burst(s) and extract data bits from the received RF burst(s) and a second equalizer operable to be trained based upon at least the known training sequence(s), equalize the received RF burst(s) and extract alternate data bits from the received RF burst(s); and
a channel length estimation module operable to determine a channel length associated with the RF burst(s) and selectively disable the second equalizer when the channel length exceeds a predetermined channel length threshold.
9. The wireless terminal of claim 8 , wherein the combination of the baseband processor and multi-branch equalizer processing module are operable to produce a data block from soft decisions or alternative soft decisions when the channel length associated with the RF burst(s) does not exceed the predetermined channel length threshold.
10. The wireless terminal of claim 9 , further comprising:
a de-interleaver operable to deinterleave the data block;
a decoder operable to decode a data frame from the data block;
a re-encoder operable to re-encode the data frame to produce at least a partially re-encoded data block; and
an interleaver operable to interleave the at least partially re-encoded data block to produce an at least partially re-encoded burst comprising the known training sequence(s) and re-encoded data bits.
11. The wireless terminal of claim 10 , wherein the second equalizer is further operable to be trained based upon the at least partially re-encoded burst.
12. The wireless terminal of claim 8 , wherein the channel length estimation module is operable to disable the second equalizer when:
a measure of the colored noise associated with the RF burst(s) exceeds a predetermined colored noise threshold; or
a signal-to-noise ratio (SNR) associated with the RF burst(s) exceeds a predetermined SNR threshold.
13. The wireless terminal of claim 8 , wherein the predetermined channel length threshold is less than a hilly terrain (HT) channel.
14. The wireless terminal of claim 8 , wherein the channel length estimation module is further operable to:
adjust a number of equalizer states for the first equalizer based on the channel length associated with the RF burst(s).
15. The wireless terminal of claim 8 , wherein:
the received RF bursts that the channel length estimation module examines to determine when to selectively disable the second equalizer comprises a first set of RF bursts; and
the received RF bursts that the first equalizer and second equalizer process comprise a second set of RF bursts, wherein the first set of RF bursts preceded the second set of RF bursts; and
the sets of RF bursts comprise:
4 RF bursts; or
2 RF burst for half rate adaptive multi-rate encoded speech.
16. The wireless terminal of claim 8 , wherein the channel length estimation module is further operable to reduce a number of equalizer states for the first equalizer when disabling the second equalizer based on the channel length associated with a the RF burst(s).
17. The wireless terminal of claim 8 , wherein the RF burst(s) include Gaussian Minimum Shift Keying (GMSK) symbols carrying the data bits and interfering Eight Phase Shift Keying (8PSK)/GMSK symbols.
18. A method for equalizing received radio frequency (RF) burst(s), comprising:
establishing a predetermined channel length threshold;
determining a channel length associated with the RF burst(s);
training a first equalizer with a known training sequence;
equalizing the received RF burst(s) with the first equalizer;
decoding the RF burst(s) to yield extracted data bits;
comparing the channel length associated with the RF burst(s) with the predetermined channel length threshold; and
when the channel length associated with the RF burst(s) is less than the predetermined channel length threshold:
training a second equalizer with the known training sequence; and
equalizing the received RF bursts with the second equalizer to extract alternative data bits.
19. The method of claim 18 , further comprising:
determining a measure of the colored noise associated with the RF burst(s);
determining a signal-to-noise ratio (SNR) associated with the RF burst(s); and
disabling the second equalizer when:
the measure of the colored noise associated with the RF burst(s) exceeds a predetermined colored noise threshold; or
the SNR associated with the RF burst(s) exceeds a predetermined SNR threshold.
20. The method of claim 18 , further comprising:
deinterleaving the RF burst(s) to produce deinterleaved RF burst(s);
decoding the deinterleaved RF burst(s) the to yield the extracted data bits;
decoding a frame from the extracted data bits; and
when the channel length associated with the RF burst(s) is less than the predetermined channel length threshold:
re-encoding the frame to produce re-encoded data bits;
interleaving the re-encoded data bits;
training a second equalizer with the known training sequence and the re-encoded data bits;
equalizing the received RF bursts to extract alternative data bits with the second equalizer;
deinterleaving the alternative extracted data bits; and
decoding an alternate frame from the deinterleaved alternative extracted data bits.