Chip blanking and processing in SCDMA to mitigate impulse and burst noise and/or distortion
View Patent ↗A system for mitigating impairment in a communication system includes a delay block, a signal level block, a moving average window block, an impulse noise detection block, and a combiner. The delay block receives and delays each chip of a plurality of chips in a spreading interval. The signal level block determines a signal level of each chip of the plurality of chips in the spreading interval. The moving average window block determines a composite signal level for a chip window corresponding to the chip. The impulse noise detection block receives the signal level, receives the composite signal level, and produces an erasure indication for each chip of the plurality of chips of the corresponding chip window. The combiner erases chips of the plurality of chips of the spreading interval based upon the erasure indication.
1. A method for mitigating impairment in a communication system, the method comprising:
receiving a plurality of chips in a spreading interval;
for each chip of the spreading interval:
determining a signal level of the chip;
comparing the signal level of the chip to a first threshold to produce a first comparison result;
determining a composite signal level of a plurality of chips of a chip window of the spreading interval; and
comparing the composite signal level of the plurality of chips of the chip window to a second threshold to produce a second comparison result; and
keeping or erasing the chip based upon the first comparison result and the second comparison result.
2. The method of claim 1 , further comprising passing a plurality of kept chips and at least one blanked chip to a coupled decoder.
3. The method of claim 1 , wherein determining the signal level of the chip comprises magnitude-squaring a measured level of the chip.
4. The method of claim 1 , wherein determining the composite signal level of the plurality of chips of the chip window of the spreading interval comprises:
magnitude-squaring a measured level of each chip of the plurality of chips of the chip window to produce a corresponding plurality of signal levels;
summing the corresponding plurality of signal levels to produce a signal level summation result; and
averaging the signal level summation result across the chip window to produce the composite signal level.
5. The method of claim 1 , wherein the chip is erased when either the first comparison result or the second comparison result is unfavorable.
6. The method of claim 1 , wherein the chip is erased only when both the first comparison result and the second comparison result are unfavorable.
7. The method of claim 1 :
further comprising comparing the composite signal level of the plurality of chips of the corresponding chip window to a third threshold to produce a third comparison result;
further comprising determining a fourth comparison result based upon third comparison results of adjacent chips; and
wherein keeping or erasing the chip is further based upon the fourth comparison result.
8. The method of claim 7 , wherein the fourth comparison result is indicative of a boundary of impulse noise affecting the plurality of chips in the spreading interval.
9. The method of claim 1 , wherein keeping or erasing the chip based upon the first comparison result and the second comparison result further comprises considering first comparison results and second comparison results of neighboring chips.
10. The method of claim 1 , further comprising delaying the plurality of chips in the spreading interval to allow for delay in completing the keeping or erasing operations.
11. A system for mitigating impairment in a communication system comprising:
a delay block operable to receive and delay each chip of a plurality of chips in a spreading interval;
a signal level block operable to determine a signal level of each chip of the plurality of chips in the spreading interval;
a moving average window block communicatively coupled to the signal level block and operable to determine a composite signal level for a chip window corresponding to the chip;
an impulse noise detection block communicatively coupled to the signal level block and to the moving average window block, operable to receive the signal level of each chip of the plurality of chips in the spreading interval, operable to receive the composite signal level corresponding to each chip of the plurality of chips, and operable to produce an erasure indication for each chip of the plurality of chips of the corresponding chip window; and
a combiner communicatively coupled to the delay block and to the impulse noise detection block and operable to keep or erase chips of the plurality of chips in the spreading interval based upon the erasure indication.
12. The system of claim 11 , further comprising decoder coupling operable to pass a plurality of kept chips and at least one blanked chip to a coupled decoder.
13. The system of claim 11 , wherein determining the signal level of the chip comprises magnitude-squaring a measured level of the chip.
14. The system of claim 11 , wherein the moving average window block is operable to determine the composite signal level for a chip window corresponding to the chip by:
magnitude-squaring a measured level of each chip of the plurality of chips of the chip window to produce a corresponding plurality of signal levels;
summing the corresponding plurality of signal levels to produce a signal level summation result; and
averaging the signal level summation result across the chip window to produce the composite signal level.
15. The system of claim 11 , wherein the impulse noise detection block is operable to, for each chip of the plurality of chips:
compare the signal level of the chip to a first threshold to produce a first comparison result;
compare the composite signal level corresponding to the chip to a second threshold to produce a second comparison result; and
produce the erasure indication based upon the first comparison result and the second comparison result.
16. The system of claim 15 , wherein the impulse noise detection block is operable to erase the chip when either the first comparison result or the second comparison result is unfavorable.
17. The system of claim 15 , wherein the impulse noise detection block is operable to erase the chip only when both the first comparison result and the second comparison result are unfavorable.
18. The system of claim 15 , wherein the impulse noise detection block is further operable to:
compare the composite signal level of the plurality of chips of the corresponding chip window to a third threshold to produce a third comparison result;
determine a fourth comparison result based upon third comparison results of adjacent chips; and
produce the erasure indication based upon the fourth comparison result.
19. The system of claim 18 , wherein the fourth comparison result is indicative of a boundary of impulse noise affecting the plurality of chips in the spreading interval.
20. The system of claim 11 , further comprising producing the erasure indication by considering first comparison results and second comparison results of neighboring chips.
21. The system of claim 11 , wherein the delay block is operable to delay the plurality of chips in the spreading interval to allow the impulse noise detection block to produce the erasure indication.
22. A method for mitigating impairment in a communication system, the method comprising:
receiving a plurality of chips in a spreading interval;
for each chip of the spreading interval:
determining a signal level of the chip;
comparing the signal level of the chip to a first threshold to produce a first comparison result;
determining a composite signal level of a plurality of chips of a chip window of the spreading interval; and
comparing the composite signal level of the plurality of chips of the chip window to a second threshold to produce a second comparison result;
comparing the composite signal level of the plurality of chips of the corresponding chip window to a third threshold to produce a third comparison result; and
determining a fourth comparison result based upon third comparison results of adjacent chips; and
keeping or erasing the chip based upon the first comparison result, the second comparison result, and the fourth comparison result.
23. The method of claim 22 , wherein determining the composite signal level of the plurality of chips of the chip window of the spreading interval comprises:
magnitude-squaring a measured level of each chip of the plurality of chips of the chip window to produce a corresponding plurality of signal levels;
summing the corresponding plurality of signal levels to produce a signal level summation result; and
averaging the signal level summation result across the chip window to produce the composite signal level.
24. The method of claim 22 , wherein the fourth comparison result is indicative of a boundary of impulse noise affecting the plurality of chips in the spreading interval.