US 7,095,812 B2 · Reduced complexity receiver for space-time- bit-interleaved coded modulation

Abstract

A system employs space-time coding characterized at the transmitter by bit-interleaved coded modulation (BICM) combined with modulating several streams of the BICM encoded data for transmission over two or more antennas. Space-time coding techniques improve transmission efficiency in radio channels by using multiple transmit and/or receive antennas and coordination of the signaling over these antennas. Bit-interleaved coded modulation provides good diversity gain with higher-order modulation schemes that employ binary convolutional codes. A receiver demodulates the received signals and applies multi-input, multi-output (MIMO) demapping to estimate the BICM encoded bitstream. After deinterleaving of the BICM encoded bitstream, maximum a posteriori (MAP) decoding is applied to the resulting bit stream to generate soft output values. By applying well-known turbo-decoding principles to iteratively demap and decode, the overall receiver performance is significantly improved. The MIMO demapping and MAP decoding processes exchange likelihood information to improve the bit error rate performance over several iterations of demapping/decoding. By generating tentative decisions for transmitted bits, the overall number of evaluations used for demapping may be reduced.

Claims17

Dependent claims

A method of iteratively demapping and decoding two or more received signals into data, the method comprising the steps of:

for a first iteration,
(a) demapping, with a multi-input, multi-output (MIMO) demapper, a sequence of encoded data from the received signals as a set of minimized cost function error (MCFE) estimates;
(b) generating MCFE likelihood values for the set of MCFE estimates based on a set of corresponding variances;
(c) calculating, for the set of MCFE estimates, a set of probabilities of correct decision based on the MCFE likelihood values;
(d) setting fewer than all of the estimates in the set of MCFE estimates as hard decisions based on the set of probabilities of correct decision;
and
(e) calculating a set of maximum a posteriori (MAP) likelihood values based on the one or more MCFE estimates not set as hard decisions in step (d).

4 more elements

A computer-readable medium having stored thereon a plurality of instructions, the plurality of instructions including instructions which, when executed by a processor, cause the processor to implement a method for iteratively demapping and decoding two or more received signals into data, the method comprising the steps of:

for a first iteration,
(a) demapping, with a multi-input, multi-output (MIMO) demapper, a sequence of encoded data from the received signals as a set of minimized cost function error (MCFE) estimates;
(b) generating MCFE likelihood values for the set of MCFE estimates based on a set of corresponding variances;
(c) calculating, for the set of MCFE estimates, a set of probabilities of correct decision based on the MCFE likelihood values;
(d) setting fewer than all of the estimates in the set of MCFE estimates as hard decisions based on the set of probabilities of correct decision;
and
(e) calculating a set of maximum a posteriori (MAP) likelihood values based on the one or more MCFE estimates not set as hard decisions in step (d).

4 more elements

A method of iteratively demapping and decoding two or more received signals into data, the method comprising the steps of:

for a first iteration,
(a) demapping, with a multi-input, multi-output (MIMO) demapper, a sequence of encoded data from the received signals as a set of minimized cost function error (MCFE) estimates;
(b) generating MCFE likelihood values for the set of MCFE estimates based on a set of corresponding variances;
(c) calculating, for the set of MCFE estimates, a set of probabilities of correct decision based on the MCFE likelihood values;
(d) setting one or more of the set of MCFE estimates as hard decisions based on the set of probabilities of correct decision;
and
(e) calculating a set of maximum a posteriori (MAP) likelihood values based on the remaining MCFE estimates;
wherein, for step (c), each probability Pc of correct decision is given by:
P
c
≈
(
1
-
N
c
⁢
Q
⁡
(
d
min
2
⁢
⁢
σ
i
)
)
⁢
1
1
+
ⅇ
-

L
m
⁡
(
b
k
n
)

,
wherein Q(•) is a complementary error function, Nc represents an average number of nearest neighbors, σi is a variance corresponding to the ith MCFE estimate, Lm(bkn) represents an a posteriori log-likelihood ratio of transmit bit bkn, and dmin is a minimum distance between user symbols for a constellation.

44 more elements

Dependencies are inferred from the claim text.

Reduced complexity receiver for space-time- bit-interleaved coded modulation

Life of this patent

Reduced complexity receiver for space-time- bit-interleaved coded modulation

Life of this patent

Abstract

Claims17