Low complexity, iterative approach to active interference cancellation
View Patent ↗Generating a notch in an Orthogonal Frequency Division Multiplexing (OFDM) frequency spectrum includes determining a first active interference cancellation (AIC) tone, comparing the first AIC tone with an amplitude limit, in the event that the first AIC tone exceeds the amplitude limit, constraining the first AIC tone, and determining a second AIC tone based at least in part on the first AIC tone. An Active Interference Cancellation (AIC) tone generator includes an interface configured to receive a plurality of tones, a processing component coupled to the interface, configured to determine a first AIC tone, compare the first AIC tone with an amplitude limit, and in the event that the first AIC tone exceeds the amplitude limit, constrain the first AIC tone, and determine a second AIC tone based at least in part on the first AIC tone.
1. A method of generating a notch in an Orthogonal Frequency Division Multiplexing (OFDM) frequency spectrum, comprising:
determining a first active interference cancellation (AIC) tone;
comparing, using a processing component, the first AIC tone with an amplitude limit;
in the event that the first AIC tone exceeds the amplitude limit, constraining the first AIC tone, and determining a second AIC tone based at least in part on the first AIC tone;
wherein the first AIC tone is determined based at least in part on a plurality of peak values of a transform function.
2. A method as recited in claim 1 , wherein the transform function is a transform function of a window function.
3. A method as recited in claim 1 , wherein the first AIC tone is determined based at least in part on a plurality of data tones.
4. A method as recited in claim 1 , wherein the second AIC tone is determined based at least in part on the plurality of peak values of the transform function.
5. A method as recited in claim 1 , wherein a current AIC tone is used as the second AIC tone, and the method further comprises:
a) comparing the current AIC tone with the amplitude limit; and
b) in the event that the current AIC tone exceeds the amplitude limit, constraining the current AIC tone, obtaining a next AIC tone to be determined, and setting the current AIC tone to be the next AIC tone.
6. A method as recited in claim 5 , further comprising repeating a)-b).
7. A method as recited in claim 1 , wherein constraining the first AIC tone includes multiplying the AIC tone with a normalization factor.
8. A method as recited in claim 1 , wherein constraining the first AIC tone includes multiplying the AIC tone with a normalization factor Cnorm, and
C
norm
=
(
A
2
-
A
1
)
·
1
num_len
-
1
∑
n
=
2
num_len
Peak
(
n
)
1
num_len
∑
n
=
1
num_len
Peak
(
n
)
,
wherein
A 1 corresponds to an amplitude of the AIC tone, A 2 corresponds to a constrained tone level, num_len corresponds to (number of null tones desired)/2, rounded up for odd number of null tones, n corresponds to the peak number for the sinc function, and Peak(n) corresponds to the relative value of the sinc function at peak n.
9. A method as recited in claim 1 , wherein constraining the first AIC tone includes multiplying the AIC tone with a normalization factor Cnorm that is set to a convergent value substantially between 0.8-0.84.
10. An Active Interference Cancellation (AIC) tone generator, comprising:
an interface configured to receive a plurality of tones;
a processing component coupled to the interface, configured to:
determine a first AIC tone;
compare the first AIC tone with an amplitude limit; and
in the event that the first AIC tone exceeds the amplitude limit, constrain the first AIC tone, and determine a second AIC tone based at least in part on the first AIC tone;
wherein the first AIC tone is determined based at least in part on a plurality of peak values of a transform function.
11. An AIC tone generator as recited in claim 10 , wherein the transform function is a transform function of a window function.
12. An AIC tone generator as recited in claim 10 , wherein the first AIC tone is further determined based at least in part on a plurality of data tones.
13. An AIC tone generator as recited in claim 10 , wherein the second AIC tone is further determined based at least in part on the plurality of peak values of the transform function.
14. An Orthogonal Frequency Division Multiplexing (OFDM) transmitter comprising:
a tone controller configured to turn off one or more data tones in a frequency band;
an active interference cancellation (AIC) tone generator coupled to the tone controller, configured to:
determine a first AIC tone;
compare the first AIC tone with an amplitude limit; and
in the event that the first AIC tone exceeds the amplitude limit, constrain the first AIC tone, and determine a second AIC tone based at least in part on the first AIC tone;
wherein the first AIC tone is determined based at least in part on a plurality of peak values of a transform function.
15. An OFDM transmitter as recited in claim 14 , wherein the transform function is a transform function of a window function.
16. An OFDM transmitter as recited in claim 14 , wherein the first AIC tone is further determined based at least in part on a plurality of data tones.
17. An OFDM transmitter as recited in claim 14 , wherein the second AIC tone is further determined based at least in part on the plurality of peak values of the transform function.