Near-capacity iterative detection of co-channel interference for a high-efficiency multibeam satellite system
A communications apparatus to receive a composite signal including a desired signal and interferer signals, where the desired signal may include desired symbols and the interferer signals may include interferer symbols. The system may include N frameworks, each framework may include a detector to partition the desired symbols and the interferer symbols based on an interference severity into a dominant group and a non-dominant group, and to generate A Posteriori Probabilities (APP) of the desired symbols and the interferer symbols. The detector of each of the N frameworks generates the APP based on a feedback of a priori probabilities from each of the N frameworks.
1. A communications apparatus comprising:
a composite signal comprising a desired signal and interferer signals, wherein the desired signal comprises desired symbols and the interferer signals comprise interferer symbols; and
N frameworks, each framework comprising
a detector to partition the desired symbols and the interferer symbols based on an interference severity into a dominant group and a non-dominant group, and to generate A Posteriori Probabilities (APP) of the desired symbols and the interferer symbols,
wherein the detector of each of the N frameworks generates the APP based on a feedback of a priori probabilities from each of the N frameworks.
2. The communications apparatus of claim 1 , wherein the detector of each of the N frameworks transforms the APP to a first Log-Likelihood Ratios (LLRs) using a bit-to-symbol mapping rule, and
each of N frameworks further comprises
a deinterleaver to deinterleave the first LLRs into a decoder input,
a Forward Error Correcting (FEC) Decoder to decode the decoder input and to generate a second LLRs from a decoded decoder input, and
an interleaver to interleave the second LLRs,
wherein the second LLRs are treated as a priori probabilities for a respective N framework after the interleaver of the respective N framework, and
the second LLRs of each of the N frameworks represent either the desired symbols or the interferer symbols.
3. The communications apparatus of claim 2 , wherein the desired signal is more robust than each of the interferer signals, and the second LLRs from the FEC decoder of a first framework of the N frameworks represent the desired symbols.
4. The communications apparatus of claim 2 , wherein at least one of the interferer signals is more robust than the desired signal, and the second LLRs from the FEC decoder of a framework other than a first framework of the N frameworks represent the desired symbols.
5. The communications apparatus of claim 4 , wherein the desired symbols are recovered by Simultaneous Decoding (SD) or by Simultaneous Non-unique Decoding (SND).
6. The communications apparatus of claim 1 , wherein the detector is selected from a Soft-In Soft-Out (SISO) detector, a Divide-And-Conquer (DAC) detector or a SISO DAC detector.
7. The communications apparatus of claim 1 , wherein the communications apparatus is disposed in an SISO Iterative Divide and Conquer (IDAC) receiver and the detector is a SISO DAC detector.
8. The communications apparatus of claim 1 , wherein the dominant group comprises an Optimal-Bayesian (OB) group via a probability mass function (pmf).
9. The communications apparatus of claim 1 , wherein the non-dominant group comprises a Noise-Floor (NF) group incorporated via a power of each member and a Subtractive-Cancellation (SC) group incorporated via first- and second-order moments derived from the a priori probabilities, and the dominant group comprises an Optimal-Bayesian (OB) group incorporated via a probability mass function (pmf).
10. The communications apparatus of claim 9 , wherein an output
x
[
k
]
=
γ
n
d
·
a
n
d
,
k
+
h
_
I
,
n
d
(
O
B
)
[
k
]
·
a
_
I
,
n
d
(
O
B
)
[
k
]
+
h
_
I
,
n
d
(
S
C
)
·
[
k
]
·
a
_
I
,
n
d
(
S
C
)
[
k
]
+
h
_
I
,
n
d
(
N
F
)
[
k
]
·
a
_
I
,
n
d
(
NF
)
[
k
]
+
n
[
k
]
,
where a i,nd [k] partitioned into three groups, a I,n d (NF) [k], a I,n d (SC) [k], a I,n d (OB) [k], and h I,n d (NF) [k], h I,n d (SC) [k], h I,n d (OB) [k] represents spatial and temporal CCI channel coefficients corresponding to the NF group, the SC group and the OB group, respectively.
11. The communications apparatus of claim 10 , wherein the detector is mathematically expressed as
P
D
A
C
(
a
n
d
,
k
|
x
[
k
]
)
=
∑
a
_
I
,
n
d
(
OB
)
[
k
]
p
D
A
C
(
x
[
k
]
|
a
n
d
,
k
,
a
_
I
,
n
d
(
OB
)
[
k
]
,
a
_
I
,
n
d
(
SC
)
[
k
]
,
a
_
I
,
n
d
(
NF
)
[
k
]
)
·
P
(
a
_
I
,
n
d
(
OB
)
[
k
]
)
·
P
(
a
n
d
,
k
)
,
where pDAC(⋅) is
p
DAC
(
x
[
k
]
|
a
n
d
,
k
,
a
_
I
,
n
d
(
OB
)
[
k
]
,
a
_
I
,
n
d
(
S
C
)
[
k
]
,
a
_
I
,
n
d
(
NF
)
[
k
]
)
=
exp
{
-
(
x
[
k
]
-
I
^
n
d
(
SC
)
[
k
]
)
-
γ
n
d
·
a
n
d
,
k
-
h
_
I
,
n
d
(
OB
)
[
k
]
·
a
_
I
,
n
d
(
OB
)
[
k
]
2
σ
n
2
+
c
I
,
n
d
(
SC
)
[
k
]
+
c
I
,
n
d
(
N
F
)
[
k
]
}
a likelihood function associated with observing x[k], P(⋅) is the a priori probabilities corresponding to the second LLRs representing the desired symbols, Î n d (SC) [k]= h I,n d (SC) [k]· { a I,n d (SC) [k]}, c I,n d (SC) [k]· { a I,n d (SC) [k]}·( h I,n d (SC) [k]) H , and c I,n d (NF) [k]= h I,n d (NF) [k]·( h I,n d (NF) [k]) H .
12. The communications apparatus of claim 1 , wherein a count of the N frameworks is selected from one (1), two (2) or three (3).
13. The communications apparatus of claim 1 , wherein the desired signal and the interferer signals comprise DVB-S2X standard compliant signals.
14. A computer implemented method comprising:
providing a composite signal comprising a desired signal and interferer signals, wherein the desired signal comprises desired symbols and the interferer signals comprise interferer symbols; and
iteratively computing, N frameworks, each framework comprising
partitioning the desired symbols and the interferer symbols based on an interference severity into a dominant group and a non-dominant group, and
generating A Posteriori Probabilities (APP) of the desired symbols and the interferer symbols,
wherein the detector of each of the N frameworks generates the APP based on a feedback of a priori probabilities from each of the N frameworks.
15. The method of claim 14 , wherein the detector of each of the N frameworks transforms the APP to a first Log-Likelihood Ratios (LLRs) using a bit-to-symbol mapping rule, and
the iteratively computing further comprises:
deinterleaving the first LLRs into a decoder input,
decoding the decoder input,
generating a second LLRs from a decoded decoder input and
interleaving the second LLRs,
wherein the second LLRs are treated as a priori probabilities for a respective N framework after the interleaver of the respective N framework, and
the second LLRs of each of the N frameworks represent either the desired symbols or the interferer symbols.
16. The method of claim 15 , wherein the desired signal is more robust than each of the interferer signals, and the second LLRs from the decoding of a first framework of the N frameworks represent the desired symbols.
17. The method of claim 15 , wherein at least one of the interferer signals is more robust than the desired signal, and the second LLRs from the decoding of a framework other than a first framework of the N frameworks represent the desired symbols.
18. The method of claim 14 , wherein the non-dominant group comprises a Noise-Floor (NF) group incorporated via a power of each member and a Subtractive-Cancellation (SC) group incorporated via first- and second-order moments derived from the a priori probabilities, and the dominant group comprises an Optimal-Bayesian (OB) group incorporated via a probability mass function (pmf).
19. The method of claim 18 , wherein an output x[k] is,
x
[
k
]
=
γ
n
d
·
a
n
d
,
k
+
h
_
I
,
n
d
(
O
B
)
[
k
]
·
a
_
I
,
n
d
(
O
B
)
[
k
]
+
h
_
I
,
n
d
(
S
C
)
·
[
k
]
·
a
_
I
,
n
d
(
S
C
)
[
k
]
+
h
_
I
,
n
d
(
N
F
)
[
k
]
·
a
_
I
,
n
d
(
NF
)
[
k
]
+
n
[
k
]
,
where a i,nd [k] is partitioned into three groups, a I,n d (NF) [k], a I,n d (SC) [k], a I,n d (OB) [k], and h I,n d (NF) [k], h I,n d (SC) [k], h I,n d (OB) [k] represents spatial and temporal CCI channel coefficients corresponding to the NF group, the SC group and the OB group, respectively.
20. The method of claim 19 , wherein the detector is mathematically expressed as
P
D
A
C
(
a
n
d
,
k
|
x
[
k
]
)
=
∑
a
_
I
,
n
d
(
OB
)
[
k
]
p
D
A
C
(
x
[
k
]
|
a
n
d
,
k
,
a
_
I
,
n
d
(
OB
)
[
k
]
,
a
_
I
,
n
d
(
SC
)
[
k
]
,
a
_
I
,
n
d
(
NF
)
[
k
]
)
·
P
(
a
_
I
,
n
d
(
OB
)
[
k
]
)
·
P
(
a
n
d
,
k
)
,
where pDAC(⋅) is
p
DAC
(
x
[
k
]
|
a
n
d
,
k
,
a
_
I
,
n
d
(
OB
)
[
k
]
,
a
_
I
,
n
d
(
S
C
)
[
k
]
,
a
_
I
,
n
d
(
NF
)
[
k
]
)
=
exp
{
-
(
x
[
k
]
-
I
^
n
d
(
SC
)
[
k
]
)
-
γ
n
d
·
a
n
d
,
k
-
h
_
I
,
n
d
(
OB
)
[
k
]
·
a
_
I
,
n
d
(
OB
)
[
k
]
2
σ
n
2
+
c
I
,
n
d
(
SC
)
[
k
]
+
c
I
,
n
d
(
N
F
)
[
k
]
}
a likelihood function associated with observing x[k], PH is the a priori probabilities corresponding to the second LLRs representing the desired symbols, Î n d (SC) [k]= h I,n d (SC) [k]· { a I,n d (SC) [k]}, c I,n d (SC) [k]· { a I,n d (SC) [k]}·( h I,n d (SC) [k]) H , and c I,n d (NF) [k]= h I,n d (NF) [k]·( h I,n d (NF)[k]) H .