Method and apparatus for equalization and decoding in a wireless communications system including plural receiver antennae
View Patent ↗Joint equalization and decoding techniques to eliminate the division operations in the Frequency domain Equalizer (FEQ) of an Orthogonal Frequency Division Modulation (OFDM) receiver by incorporating the magnitude of the channel impulse response estimates into the decision metrics in the decoder. This includes methods for both hard-decision symbol-by-symbol detection and soft-decision decoding using the Viterbi algorithm. Further, Channel State Information (CSI) is incorporated to improve the performance of the receiver. The disclosure also introduces a computationally efficient bit-by-bit piecewise approximation technique incorporating CSI to implement decoder decision metrics. Finally, an efficient implementation technique for multiple receiver antennae using Maximum Ratio Combining (MRC) and Viterbi decoding with CSI is disclosed.
1. A baseband processing unit for decoding a received symbol bearing modulated data, the received symbol capable of being borne across plural receive pathways, the unit comprising:
a demodulation unit to generate channel state information and a co-phased and summed MRC symbol from the received symbol; and
a Viterbi decoder, comprising:
a branch metric computation unit to compute a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
a most-likely symbol estimator to estimate a clean symbol based on the plurality of branch metrics computed by said branch metric computation unit.
2. The processing unit of claim 1 , wherein
the demodulation unit equalizes the MRC symbol to derive {overscore (X)} k,n,t CSI ; and
wherein said branch metric computation unit computes the plurality of branch metrics using BM k,n,t =−2{overscore (X)} k,n,i CSI ·X+(Ĥ k,n ·X) 2 per dimension.
3. The processing unit of claim 1 , wherein said branch metric computation unit computes the plurality of branch metrics based on a channel estimate associated with the received symbol.
4. The processing unit of claim 3 , wherein said branch metric computation unit computes the plurality of branch metrics using
BM k,n,i =−2 Z k,n,i ·X+Ĥ k,n 4 ·X 2 .
5. The processing unit of claim 1 , wherein said branch metric computation unit computes the plurality of branch metrics based on a piecewise bit-by-bit approximation.
6. The processing unit of claim 5 , wherein said branch metric computation unit computes the plurality of branch metrics using
BM k,n,t =−(| Z k,n,t |−Ĥ k,n 2 ·m )·sign( b t ).
7. The processing unit of claim 1 , wherein said branch metric computation unit computes the plurality of branch metrics based on a gain associated with each of the plurality of receive pathways and a piecewise bit-by-bit approximation.
8. The processing unit of claim 7 , wherein said branch metric computation unit computes the plurality of branch metrics using
BM k,n,t =(−| Z k,n,t |+{hacek over (H)} k,n 2 ·m )·sign( b i )
where
H
⋓
k
,
n
=
∑
m
=
0
D
-
1
(
g
(
m
)
)
-
2
H
~
k
,
n
(
m
)
2
.
9. The processing unit of claim 1 , wherein the received symbol comprises an OFDM symbol formatted in compliance with at least one of IEEE 802.11a, IEEE 802.11g, and IEEE 802.16a standards.
10. The processing unit of claim 9 , wherein the OFDM symbol is mapped to one of a DBPSK, QPSK, 16-QAM, 64-QAM, a 256-QAM modulation constellation, and an N QAM modulation constellation wherein N exceeds 256.
11. A transceiver, comprising:
a plurality of MRC receive pathways collectively bearing a received symbol defining modulated data; and
a baseband processing unit for decoding the received symbol, comprising:
a demodulation unit to generate channel state information and a co-phased and summed MRC symbol from the received symbol; and
a Viterbi decoder, comprising:
a branch metric computation unit to compute a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
a most-likely symbol estimator to estimate a clean symbol based on the plurality of branch metrics computed by said branch metric computation unit.
12. The transceiver of claim 11 , wherein
said demodulation unit equalizes the MRC symbol to derive {overscore (X)} k,n,t CSI ; and
wherein said branch metric computation unit computes the plurality of branch metrics using BM k,n,t =−2X k,n,i CSI ·Ĥ k,n ·X+(Ĥ k,n ·X) 2 per dimension.
13. The transceiver of claim 11 , wherein said branch metric computation unit computes the plurality of branch metrics based on a channel estimate associated with the received symbol.
14. The transceiver of claim 13 , wherein said branch metric computation unit computes the plurality of branch metrics using
BM k,n,i =−2 Z k,n,i ·X+Ĥ k,n 4 ·X 2 .
15. The transceiver of claim 11 , wherein said branch metric computation unit computes the plurality of branch metrics based on a piecewise bit-by-bit approximation.
16. The transceiver of claim 15 , wherein said branch metric computation unit computes the plurality of branch metrics using
BM k,n,t =−(| Z k,n,t |−H k,n 2 ·m )·sign( b i ).
17. The transceiver of claim 11 , wherein said branch metric computation unit computes the plurality of branch metrics based on a gain associated with each of the plurality of receive pathways and a piecewise bit-by-bit approximation.
18. The transceiver of claim 17 , wherein said branch metric computation unit computes the plurality of branch metrics using where
BM k,n,t =−(| Z k,n,t |+{hacek over (H)} k,n 2 ·m )·sign( b i ).
where
H
⋓
k
,
n
=
∑
m
=
0
D
-
1
(
g
(
m
)
)
-
2
H
~
k
,
n
(
m
)
2
.
19. The transceiver of claim 11 , wherein the received symbol comprises an OFDM symbol formatted in compliance with at least one of IEEE 802.11a, IEEE 802.11g, and IEEE 802.16a standards.
20. The transceiver of claim 19 , wherein the OFDM symbol is mapped to one of a DBPSK, QPSK, 16-QAM, 64-QAM, a 256-QAM modulation constellation, and an N QAM modulation constellation wherein N exceeds 256.
21. The transceiver of claim 11 , further comprising a transmitter capable of transmitting an outbound signal.
22. A network interface apparatus, comprising:
a wireless transceiver, comprising:
a plurality of MRC receive pathways collectively bearing a received symbol defining modulated data; and
a baseband processing unit for decoding the received symbol, comprising:
a demodulation unit to generate channel state information and a co-phased and summed MRC symbol from the received symbol; and
a Viterbi decoder, comprising:
a branch metric computation unit to compute a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
a most-likely symbol estimator to estimate a clean symbol based on the plurality of branch metrics computed by said branch metric computation unit; and
a network interface capable of recovering inbound data from the clean symbol.
23. An information processing apparatus, comprising:
an information processor; and
a network interface apparatus responsive to said information processor, said network interface apparatus comprising:
a wireless transceiver, comprising:
a plurality of MRC receive pathways collectively bearing a received symbol defining modulated data; and
a baseband processing unit for decoding the received symbol, comprising:
a demodulation unit to generate channel state information and a co-phased and summed MRC symbol from the received symbol; and
a Viterbi decoder, comprising:
a branch metric computation unit to compute a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
a most-likely symbol estimator to estimate a clean symbol based on the plurality of branch metrics computed by said branch metric computation unit; and
a network interface capable of recovering inbound data from the clean symbol.
24. A baseband processing unit for decoding a received symbol bearing modulated data, the received symbol capable of being borne across plural receive pathways, the unit comprising:
means for generating channel state information and a co-phased and summed MRC symbol from the received symbol; and
Viterbi decoder means, comprising:
means for computing a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
means for estimating a clean symbol based on the plurality of branch metrics computed by said computing means.
25. The processing unit of claim 24 , wherein
the generating means includes means for equalizing the MRC symbol to derive {overscore (X)} k,n,i CSI ; and
wherein said computing means includes means for computing the plurality of branch metrics using BM k,n,t =−2{overscore (X)} k,n,t CSI ·Ĥ k,n ·X+(Ĥ k,n ·X) 2 per dimension.
26. The processing unit of claim 24 , wherein said computing means includes second means for computing the plurality of branch metrics based on a channel estimate associated with the received symbol.
27. The processing unit of claim 26 , wherein said second computing means includes means for computing the plurality of branch metrics using
BM k,n,i =−2 Z k,n,i ·X+{hacek over (H)} k,n 4 ·X 2 .
28. The processing unit of claim 24 , wherein said computing means includes second means for computing the plurality of branch metrics based on a piecewise bit-by-bit approximation.
29. The processing unit of claim 28 , wherein said second computing means includes means for computing the plurality of branch metrics using
BM k,n,t =−(| Z k,n,t |−Ĥ k,n 2 ·m )·sign ( b i ).
30. The processing unit of claim 24 , wherein said computing means includes second means for computing the plurality of branch metrics based on a gain associated with each of the plurality of receive pathways and a piecewise bit-by-bit approximation.
31. The processing unit of claim 30 , wherein said second computing means includes means for computing the plurality of branch metrics using
BM k,n,i =(−| Z k,n,i |+{hacek over (H)} k,n 2 ·m )sign( b i )
where
H
⋓
k
,
n
=
∑
m
=
0
D
-
1
(
g
(
m
)
)
-
2
H
~
k
,
n
(
m
)
2
.
32. The processing unit of claim 24 , wherein the received symbol comprises an OFDM symbol formatted in compliance with at least one of IEEE 802.11a, IEEE 802.11g, and IEEE 802.16a standards.
33. The processing unit of claim 32 , wherein the OFDM symbol is mapped to one of a DBPSK, QPSK, 16-QAM, 64-QAM, a 256-QAM modulation constellation, and an N QAM modulation constellation wherein N exceeds 256.
34. A transceiver, comprising:
means for collectively bearing a received symbol defining modulated data; and
baseband processing means for decoding the received symbol, comprising:
means for generating channel state information and a co-phased and summed MRC symbol from the received symbol; and
Viterbi decoder means, comprising:
means for computing a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
means for estimating a clean symbol based on the plurality of branch metrics computed by said computing means.
35. The transceiver of claim 34 , wherein
the generating means includes means for equalizing the MRC symbol to derive {overscore (X)} k,n,t CSI ; and
wherein said computing means includes means for computing the plurality of branch metrics using BM k,n,t =−2{overscore (X)} k,n,t CSI ·Ĥ k,n ·X+(Ĥ k,n ·X) 2 per dimension.
36. The transceiver of claim 34 , wherein said computing means includes second means for computing the plurality of branch metrics based on a channel estimate associated with the received symbol.
37. The transceiver of claim 36 , wherein said second computing means includes means for computing the plurality of branch metrics using
BM k,n,i =−2 Z k,n,i ·X+Ĥ k,n 4 ·X 2 .
38. The transceiver of claim 34 , wherein said computing means includes second means for computing the plurality of branch metrics based on a piecewise bit-by-bit approximation.
39. The transceiver of claim 38 , wherein said second computing means includes means for computing the plurality of branch metrics using
BM k,n,t =−(| Z k,n,t |−Ĥ k,n 2 ·m )·sign( b i ).
40. The transceiver of claim 34 , wherein said computing means includes second means for computing the plurality of branch metrics based on a gain associated with each of the plurality of receive pathways and a piecewise bit-by-bit approximation.
41. The transceiver of claim 40 , wherein said second computing means includes means for computing the plurality of branch metrics using
BM k,n,t =(−| Z k,n,t |+{hacek over (H)} k,n 2 ·m )sign( b i )
where
H
⋓
k
,
n
=
∑
m
=
0
D
-
1
(
g
(
m
)
)
-
2
H
~
k
,
n
(
m
)
2
.
42. The transceiver of claim 34 , wherein the received symbol comprises an OFDM symbol formatted in compliance with at least one of IEEE 802.11a, IEEE 802.1 μg, and IEEE 802.16a standards.
43. The transceiver of claim 42 , wherein the OFDM symbol is mapped to one of a DBPSK, QPSK, 16-QAM, 64-QAM, a 256-QAM modulation constellation, and an N QAM modulation constellation wherein N exceeds 256.
44. The transceiver of claim 34 , further comprising means for transmitting an outbound signal.
45. A network interface apparatus, comprising:
a transceiver means, comprising:
means for collectively bearing a received symbol defining modulated data; and
baseband processing means for decoding the received symbol, comprising:
means for generating channel state information and a co-phased and summed MRC symbol from the received symbol; and
Viterbi decoder means, comprising:
means for computing a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
means for estimating a clean symbol based on the plurality of branch metrics computed by said computing means; and
means for recovering inbound data from the clean symbol.
46. An information processing apparatus, comprising:
information processor means; and
network interface means, comprising:
transceiver means, comprising:
means for collectively bearing a symbol defining modulated data; and
baseband processing means for decoding the received symbol, comprising:
means for generating channel state information and a co-phased and summed MRC symbol from the symbol; and
Viterbi decoder means, comprising:
means for computing a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
means for estimating a clean symbol based on the plurality of branch metrics computed by said computing means; and
means for recovering inbound data from the clean symbol.
47. A method for decoding a received symbol bearing modulated data, the received symbol capable of being borne across plural receive pathways, the method comprising:
generating channel state information from the received symbol;
generating a co-phased and summed MRC symbol from the received symbol;
computing a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
estimating a clean symbol based on the plurality of branch metrics computed at said computing step.
48. The method of claim 47 , wherein
said generating step includes the step of equalizing the MRC symbol to derive {overscore (X)} k,n,t CSI ; and
wherein said computing step includes computing the plurality of branch metrics using BM k,n,t =−2{overscore (X)} k,n,t CSI ·{overscore (H)} k,n ·X+(Ĥ k,n ·X) 2 per dimension.
49. The method of claim 47 , wherein said computing step includes computing the plurality of branch metrics based on a channel estimate associated with the received symbol.
50. The method of claim 49 , wherein said computing step includes computing the plurality of branch metrics using
BM k,n,i =−2 Z k,n,i ·X+Ĥ k,n 4 ·X 2 .
51. The method of claim 47 , wherein said computing step includes computing the plurality of branch metrics based on a piecewise bit-by-bit approximation.
52. The method of claim 51 , wherein said computing step includes computing the plurality of branch metrics using
BM k,n,t =(| Z k,n,t |−Ĥ k,n 2 ·m )·sign( b 1 )
53. The method of claim 47 , wherein said computing step includes computing the plurality of branch metrics based on a gain associated with each of the plurality of receive pathways and a piecewise bit-by-bit approximation.
54. The method of claim 53 , wherein said computing step includes computing the plurality of branch metrics using
BM k,n,t =(−| Z k,n,t |+{hacek over (H)} k,n 2 ·m )sign( b 1 )
where
H
⋓
k
,
n
=
∑
m
=
0
D
-
1
(
g
(
m
)
)
-
2
H
~
k
,
n
(
m
)
2
.
55. The method of claim 47 , wherein the received symbol comprises an OFDM symbol formatted in compliance with at least one of IEEE 802.11a, IEEE 802.11g, and IEEE 802.16a standards.
56. The method of claim 55 , wherein the OFDM symbol is mapped to one of a DBPSK, QPSK, 16-QAM, 64-QAM, a 256-QAM modulation constellation, and an N QAM modulation constellation wherein N exceeds 256.
57. The method of claim 47 , further comprising recovering a baseband signal, the baseband signal including the received symbol.
58. The method of claim 47 , further comprising recovering inbound data from the clean symbol.
59. A computer program product, comprising computer readable program code causing an information processor to perform the following steps in support of decoding a received symbol bearing modulated data, the received symbol capable of being borne across plural receive pathways, the steps comprising:
generating channel state information from the received symbol;
generating a co-phased and summed MRC symbol from the received symbol;
computing a plurality of branch metrics responsive to and based on the channel state information and the MRC symbol; and
estimating a clean symbol based on the plurality of branch metrics computed at said computing step.
60. The product of claim 59 , wherein
said generating step includes the step of equalizing the MRC symbol to derive {overscore (X)} k,n,i CSI ; and
wherein said computing step includes computing the plurality of branch metrics using BM k,n,t =−2{overscore (X)} k,n,t CSI ·Ĥ k,n ·X+(Ĥ k,n ·X) 2 per dimension.
61. The product of claim 59 , wherein said computing step includes computing the plurality of branch metrics based on a channel estimate associated with the received symbol.
62. The product of claim 61 , wherein said computing step includes computing the plurality of branch metrics using
BM k,n,i =−2 Z k,n,i ·X+Ĥ k,n 4 ·X 2 .
63. The product of claim 59 , wherein said computing step includes computing the plurality of branch metrics based on a piecewise bit-by-bit approximation.
64. The product of claim 63 , wherein said computing step includes computing the plurality of branch metrics using
BM k,n,t =−(| Z k,n,t |−Ĥ k,n 2 ·m )·sign( b i ).
65. The product of claim 59 , wherein said computing step includes computing the plurality of branch metrics based on a gain associated with each of the plurality of receive pathways and a piecewise bit-by-bit approximation.
66. The product of claim 65 , wherein said computing step includes computing the plurality of branch metrics using
BM k,n,t =(−| Z k,n,t |+{hacek over (H)} k,n 2 ·m )sign( b i )
H
⋓
k
,
n
=
∑
m
=
0
D
-
1
(
g
(
m
)
)
-
2
H
~
k
,
n
(
m
)
2
.
67. The product of claim 59 , wherein the received symbol comprises an OFDM symbol formatted in compliance with at least one of IEEE 802.11a, IEEE 802.11g, and IEEE 802.16a standards.
68. The product of claim 67 , wherein the OFDM symbol is mapped to one of a DBPSK, QPSK, 16-QAM, 64-QAM, a 256-QAM modulation constellation, and an N QAM modulation constellation wherein N exceeds 256.
69. The product of claim 59 , further comprising computer readable program code causing the information processor to perform the step of recovering a baseband signal, the baseband signal including the received symbol.
70. The product of claim 59 , further comprising computer readable program code causing the information processor to perform the step of recovering inbound data from the clean symbol.