-
[show abstract]
[hide abstract]
ABSTRACT: Subspace codes were introduced by K\"otter and Kschischang for error control
in random linear network coding. In this paper, a layered type of subspace
codes is considered, which can be viewed as a superposition of multiple
component subspace codes. Exploiting the layered structure, we develop two
decoding algorithms for these codes. The first algorithm operates by separately
decoding each component code. The second algorithm is similar to the successive
interference cancellation (SIC) algorithm for conventional superposition
coding, and further permits an iterative version. We show that both algorithms
decode not only deterministically up to but also probabilistically beyond the
error-correction capability of the overall code. Finally we present possible
applications of layered subspace codes in several network coding scenarios.
09/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, we presented three approaches to improve the design of Kite
codes (newly proposed rateless codes), resulting in an ensemble of
rate-compatible
LDPC codes with code rates varying "continuously" from 0.1 to 0.9 for
additive white Gaussian noise (AWGN) channels. The new ensemble rate-compatible
LDPC codes can be constructed conveniently with an empirical formula.
Simulation results show that, when applied to incremental redundancy hybrid
automatic repeat request (IR-HARQ) system, the constructed codes (with higher
order modulation) perform well in a wide range of signal-to-noise-ratios
(SNRs).
05/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: Constellation classification for phase-amplitude-modulated signals transmitted through unknown intersymbol interference channels
is proposed based on the sequential Monte Carlo (SMC) framework under both stochastic and deterministic settings. The stochastic
SMC-based constellation classification (SMC-CC) sampler generates constellation symbol samples based on importance sampling
and resampling techniques, whereas the deterministic SMC-CC approach recursively performs exploration and selection steps
in a greedy manner. Then the constellation classification is achieved according to the distribution of the drawn samples in
both the stochastic SMC-CC and the deterministic SMC-CC. Moreover, both the proposed methods are achieved along with joint
estimation of transmitted data symbols and channel taps. Simulations show that the proposed methods perform well on various
constellations with different cardinalities, as well as constellations with symbols.
KeywordsConstellation classification-Sequential Monte Carlo-Intersymbol interference channel
Wireless Personal Communications 04/2012; 55(2):135-146. · 0.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, nested Gallager regions with a single parameter is introduced
to exploit Gallager's first bounding technique (GFBT). We present a necessary
and sufficient condition on the optimal parameter. We also present a sufficient
condition (with a simple geometrical explanation) under which the optimal
parameter does not depend on the signal-to-noise ratio (SNR). With this general
framework, three existing upper bounds are revisited, including the tangential
bound (TB) of Berlekamp, the sphere bound (SB) of Herzberg and Poltyrev, and
the tangential-sphere bound (TSB) of Poltyrev. This paper also reveals that the
SB of Herzberg and Poltyrev is equivalent to the SB of Kasami et al., which was
rarely cited in literature.
02/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: This paper is concerned with general interference channels characterized by a
sequence of transition (conditional) probabilities. We present a general
formula for the capacity region of the interference channel with two pairs of
users. The formula shows that the capacity region is the union of a family of
rectangles, where each rectangle is determined by a pair of spectral inf-mutual
information rates. Although the presented formula is usually difficult to
compute, it provides us useful insights into the interference channels. For
example, the formula suggests us that the simplest inner bounds (obtained by
treating the interference as noise) could be improved by taking into account
the structure of the interference processes. This is verified numerically by
computing the mutual information rates for Gaussian interference channels with
embedded convolutional codes.
01/2012;
-
IEEE Transactions on Communications. 01/2012; 60:9-13.
-
SCIENCE CHINA Information Sciences. 01/2012; 55:301-311.
-
[show abstract]
[hide abstract]
ABSTRACT: A modified reliability-based iterative majority-logic decoding (MRBI-MLGD) algorithm for two classes of structured LDPC codes is presented based on a recent work by Huang et al. Compared with the original one, the modified algorithm has better performance with slightly increased complexity. Then a reliability-based iterative min-sum decoding (RBI-MSD) algorithm is presented. For the presented RBI-MSD algorithm, reliability-based integer messages are processed and exchanged between variable nodes and check nodes. The main computations include only binary logical operations and integer additions. Different from the conventional min-sum algorithm, the variable nodes pass full messages rather than extrinsic messages to check nodes. This can reduce the memory loads and the computational complexity but with a little (or negligible) performance degradation. Simulation results show that, compared with the (M)RBI-MLGD algorithms, the presented RBI-MSD algorithm achieves better error performance, faster decoding convergence rate and fewer quantization bits with moderate increased computational complexity. Furthermore, the RBI-MSD algorithm is also applicable to decoding random LDPC codes, a distinct difference from the (M)RBI-MLGD algorithms. Finally, we point out that the scaling factors employed in the MRBI-MLGD algorithm and the RBI-MSD algorithm can be optimized using discretized density evolution.
IEEE Transactions on Communications 08/2011; · 1.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, we propose a new ensemble of rateless forward error correction
(FEC) codes. The proposed codes are serially concatenated codes with
Reed-Solomon (RS) codes as outer codes and Kite codes as inner codes. The inner
Kite codes are a special class of prefix rateless low-density parity-check
(PRLDPC) codes, which can generate potentially infinite (or as many as
required) random-like parity-check bits. The employment of RS codes as outer
codes not only lowers down error-floors but also ensures (with high
probability) the correctness of successfully decoded codewords. In addition to
the conventional two-stage decoding, iterative decoding between the inner code
and the outer code are also implemented to improve the performance further. The
performance of the Kite codes under maximum likelihood (ML) decoding is
analyzed by applying a refined Divsalar bound to the ensemble weight
enumerating functions (WEF). We propose a simulation-based optimization method
as well as density evolution (DE) using Gaussian approximations (GA) to design
the Kite codes. Numerical results along with semi-analytic bounds show that the
proposed codes can approach Shannon limits with extremely low error-floors. It
is also shown by simulation that the proposed codes performs well within a wide
range of signal-to-noise-ratios (SNRs).
04/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: The application of the precoding technique to turbo codes is investigated, resulting in a new class of turbo-like codes named precoded turbo codes. The introduction of a precoder provides a degree of
freedom for code optimisation. As a result, an optimised rate-1/2 precoded turbo code with a threshold of 0.28 dB is designed using the EXIT chart.
Electronics Letters 04/2011; 47(8). · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, new techniques are presented to either simplify or improve
most existing upper bounds on the maximum-likelihood (ML) decoding performance
of the binary linear codes over additive white Gaussian noise (AWGN) channels.
Firstly, the recently proposed union bound using truncated weight spectrums by
Ma {\em et al} is re-derived in a detailed way based on Gallager's first
bounding technique (GFBT), where the "good region" is specified by a
sub-optimal list decoding algorithm. The error probability caused by the bad
region can be upper-bounded by the tail-probability of a binomial distribution,
while the error probability caused by the good region can be upper-bounded by
most existing techniques. Secondly, we propose two techniques to tighten the
union bound on the error probability caused by the good region. The first
technique is based on pair-wise error probabilities, which can be further
tightened by employing the independence between the error events and certain
components of the received random vectors. The second technique is based on
triplet-wise error probabilities, which can be upper-bounded by proving that
any three bipolar vectors form a non-obtuse triangle. The proposed bounds
improve the conventional union bounds but have a similar complexity since they
involve only the $Q$-function. The proposed bounds can also be adapted to
bit-error probabilities.
04/2011;
-
25th IEEE International Conference on Advanced Information Networking and Applications, AINA 2011, Biopolis, Singapore, March 22-25, 2011; 01/2011
-
25th IEEE International Conference on Advanced Information Networking and Applications, AINA 2011, Biopolis, Singapore, March 22-25, 2011; 01/2011
-
IEEE Transactions on Communications. 01/2011; 59:1766-1771.
-
[show abstract]
[hide abstract]
ABSTRACT: A new problem formulation is presented for the Gaussian interference channels (GIFC) with two pairs of users, which are distinguished as primary users and secondary users, respectively. The primary users employ a pair of encoder and decoder that were originally designed to satisfy a given error performance requirement under the assumption that no interference exists from other users. In the case when the secondary users attempt to access the same medium, we are interested in the maximum transmission rate (defined as {\em accessible capacity}) at which secondary users can communicate reliably without affecting the error performance requirement by the primary users under the constraint that the primary encoder (not the decoder) is kept unchanged. By modeling the primary encoder as a generalized trellis code (GTC), we are then able to treat the secondary link as a finite state channel (FSC). The relation of the accessible capacity to the capacity region of the GIFC is revealed. Upper and lower bounds on the accessible capacity are derived. For some special cases, these bounds can be computed numerically by using the BCJR algorithm. The numerical results show us, as expected, that primary users with lower transmission rates may allow higher accessible rates, and that better primary encoders guarantee not only higher quality of the primary link but also higher accessible rates of the secondary users. More interestingly, the numerical results show that the accessible capacity does not always increase with the transmission power of the secondary transmitter. Comment: 28 pages, 11 figures; Submitted to IEEE Transactions on Information Theory, December, 2010
12/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: Luby-Transform (LT) codes are a class of Fountain codes which can approach the capacity of the erasure channels. In this paper, we investigate the performance of the LT codes over AWGN channels with BPSK modulation. First, the ensemble weight distribution of an LT code is derived. Secondly, we use a refined union bound to analyze the performance of LT codes under the maximum likelihood decoding assumption. Finally, simulation results using the iterative sum-product decoding algorithm are given for the comparison with the computational bounds.
Turbo Codes and Iterative Information Processing (ISTC), 2010 6th International Symposium on; 10/2010
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, we present a low-complexity joint detection-decoding algorithm for nonbinary LDPC coded-modulation systems. The algorithm combines hard-decision decoding using the message-passing strategy with the signal detector in an iterative manner. It requires low computational complexity, offers good system performance and has a fast rate of decoding convergence. Compared to the q-ary sum-product algorithm (QSPA), it provides an attractive candidate for practical applications of q-ary LDPC codes.
Information Theory Proceedings (ISIT), 2010 IEEE International Symposium on; 07/2010
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper, we present a low-complexity joint detection-decoding algorithm for nonbinary LDPC codedmodulation systems. The algorithm combines hard-decision decoding using the message-passing strategy with the signal detector in an iterative manner. It requires low computational complexity, offers good system performance and has a fast rate of decoding convergence. Compared to the q-ary sum-product algorithm (QSPA), it provides an attractive candidate for practical applications of q-ary LDPC codes. Comment: 5 pages, 8 figures, to be presented at the IEEE Symposium on Information Theory (ISIT 2010) in Austin, Texas, June 2010
06/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: In this letter, we propose a construction of nonbinary quasi-cyclic low-density parity-check (QC-LDPC) codes based on a cyclic maximum distance separable (MDS) code. The parity-check matrices are significantly rank deficient square matrices and their Tanner graphs have a girth of at least 6. The minimum distances of the codes are very respectable as far as LDPC codes are concerned. Based on plurality voting and iterative mechanism, a low-complexity nonbinary massage-passing decoding algorithm is proposed. It only requires finite field operations, integer additions and integer comparisons. Simulation results show that the decoding algorithm is fit for the proposed codes, providing efficient trade-offs between performance and decoding complexity, which suggests that the coding scheme may find some applications in communication or storage systems with high-speed and low-power consumption requirements.
IEEE Communications Letters 04/2010; · 0.98 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A low-density parity-check (LDPC) code whose parity-check matrix consists of weight-2 columns is known as a cycle code. In this letter, we propose a construction of nonbinary quasi-cyclic (QC) LDPC cycle codes based on Singer perfect difference set. The Tanner graph has girth 12 and the code length achieves the Gallager lower bound. We further show that constructed codes have exactly a minimum symbol Hamming distance 6. Simulation results show that the proposed codes perform better than random nonbinary LDPC cycle codes.
IEEE Communications Letters 03/2010; · 0.98 Impact Factor
