The combination of Non-Orthogonal Multiple Access (NOMA) and Multiple Input Multiple Output (MIMO) technologies has been identified as a powerful strategy to achieve high spectral efficiency and improved wireless serv...
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The combination of Non-Orthogonal Multiple Access (NOMA) and Multiple Input Multiple Output (MIMO) technologies has been identified as a powerful strategy to achieve high spectral efficiency and improved wireless services. Imperfect Channel State Information at Transmitter (CSIT) can lead to multiuser interference issues that pose obstacles for wireless networks utilizing MIMO technology. Instead of maintaining the accurate CSIT, Rate Splitting (RS) directly addresses the issue of imperfect CSIT by dividing user messages into private and common messages. Generalized RS is designed to maximize the achievable rate and Quality of Service (QoS) at the cost of transceiver complexity. The increasing number of users served by the Generalized RS raises the number of Successive Interference Cancellation (SIC) processes;consequently, this can place a more significant burden on users in carrying out the SIC process. This paper aims to improve RS performance by employing power distribution adjustment without increasing the number of SICs, which would burden users in the overloaded network. We apply power distribution adjustment to 1-layer RS and 2-layer Hierarchical RS (HRS), called 1-layer RSPDA and 2-layer HRSPDA, which require one or two SICs per user. The simulation results demonstrate the capabilities of the proposed methods to enhance the total sum rate of the system for low-complexity decoding RS. 1-layer RSPDA and 2-layer HRSPDA achieve an increase of 13.68 % and 12.64% in sum rate compared to Generalized RS at Signal-to-Noise Ratio (SNR) of 30 dB, respectively.
The goal of this paper is to reduce the decodingcomplexity of space-time block turbo-coded system with low performance degradation. Two block turbo-coded systems with antenna diversity are considered. These include t...
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The goal of this paper is to reduce the decodingcomplexity of space-time block turbo-coded system with low performance degradation. Two block turbo-coded systems with antenna diversity are considered. These include the simple serial concatenation of error control code with space-time block code, and the recently proposed transmit antenna diversity scheme using forward error correction techniques. It is shown that the former performs better when compared to the latter in terms of bit error rate (BER) under the same spectral efficiency (up to 7 dB at the BER of 10(-5) for quasistatic channel with two transmit and two receive antennas). For the former system, a computationally efficient decoding approach is proposed for the soft decoding of space-time block code. Compared to its original maximum likelihood decoding algorithm, it can reduce the computation by up to 70% without any performance degradation. Additionally, for the considered outer code block turbo code, through reduction of test patterns scanned in the Chase algorithm and the alternative computation of its extrinsic information during iterative decoding, extra 0.3 dB to 0.4 dB coding gain is obtained if compared with previous approaches with negligible hardware overhead. The overall decodingcomplexity is approximately ten times less than that of the near-optimum block turbo decoder with coding gain loss of 0.5 dB at the BER of 10(-5) over AWGN channel.
In this paper, we study a class of staircase codes (SCCs), which is constructed by algebraic and single-parity-check component codes. These codes are referred to as mixed-component SCCs (MC-SCCs). We propose a low-com...
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In this paper, we study a class of staircase codes (SCCs), which is constructed by algebraic and single-parity-check component codes. These codes are referred to as mixed-component SCCs (MC-SCCs). We propose a low-complexity ternary message passing decoding algorithm for MC-SCCs, where error-and-erasure decoding plays a core role and soft reliability is reconstructed by hard decisions and channel log-likelihood ratios. We develop the density evolution analysis that is applicable to both binary and non-binary algebraic codes to optimize the decoder. By properly selecting mixed components, we can construct low-error-floor MC-SCCs with a smaller size of decoding window (proportional to component lengths) and a faster speed of convergence compared with the conventional SCCs. Moreover, we verify that for various requirements of overhead and decoding window size, MC-SCCs can outperform the conventional SCCs with both BCH components in terms of both error-rate performance and decodingcomplexity.
A practical low-complexity decoding of low-density parity-check codes is studied. A fast decoding scheme for weighted bit-flipping (WBF) based algorithms is first proposed. Then, an optimised 2 bit decoding scheme and...
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A practical low-complexity decoding of low-density parity-check codes is studied. A fast decoding scheme for weighted bit-flipping (WBF) based algorithms is first proposed. Then, an optimised 2 bit decoding scheme and its VLSI architecture are presented. It is shown that the new approach has significantly better decoding performance while having comparable hardware complexity compared with WBF-based algorithms.
Sparse superposition codes were recently introduced by Barron and Joseph for reliable communication over the additive white Gaussian noise (AWGN) channel at rates approaching the channel capacity. The codebook is defi...
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Sparse superposition codes were recently introduced by Barron and Joseph for reliable communication over the additive white Gaussian noise (AWGN) channel at rates approaching the channel capacity. The codebook is defined in terms of a Gaussian design matrix, and codewords are sparse linear combinations of columns of the matrix. In this paper, we propose an approximate message passing decoder for sparse superposition codes, whose decodingcomplexity scales linearly with the size of the design matrix. The performance of the decoder is rigorously analyzed and it is shown to asymptotically achieve the AWGN capacity with an appropriate power allocation. Simulation results are provided to demonstrate the performance of the decoder at finite blocklengths. We introduce a power allocation scheme to improve the empirical performance, and demonstrate how the decodingcomplexity can be significantly reduced by using Hadamard design matrices.
In this paper, the dual-threshold-based shrinking (DTBS) scheme for efficient non-binary low-density parity-check (NB-LDPC) decoding, which has been initially presented in our previous work [1], is further studied. Pa...
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ISBN:
(纸本)9781538682401
In this paper, the dual-threshold-based shrinking (DTBS) scheme for efficient non-binary low-density parity-check (NB-LDPC) decoding, which has been initially presented in our previous work [1], is further studied. Particularly, the TIT-MSA is an example to employ this scheme presented in [1]. Its computational complexity is theoretically analyzed in this paper. Numerical results show that more than 70% computational complexity is reduced compared with the SMSA, while the error performance loss is negligible. Besides, when considering memory consumption, we extend this scheme by setting a maximum number of kept values with an efficient searching method, and apply it to the TIT-MSA. Simulation results indicate that the new decoding algorithm achieves both comparable error performance and significant memory reduction. For example, the memory consumption is reduced by about 61% for a (256, 203) code over GF(2(8)) and about 31% for an (837, 726) code over GF(2(5)).
In this paper, we present a belief propagation (BP) based algorithm for decoding non-orthogonal space-time block codes (STBC) from cyclic division algebras (CDA) having large dimensions. The proposed approach involves...
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ISBN:
(纸本)9781424443123
In this paper, we present a belief propagation (BP) based algorithm for decoding non-orthogonal space-time block codes (STBC) from cyclic division algebras (CDA) having large dimensions. The proposed approach involves message passing on Markov random field (MRF) representation of the STBC MIMO system. Adoption of BP approach to decode non-orthogonal STBCs of large dimensions has not been reported so far. Our simulation results show that the proposed BP-based decoding achieves increasingly closer to SISO AWGN performance for increased number of dimensions. In addition, it also achieves near-capacity turbo coded BER performance;for e.g., with BP decoding of 24 x 24 STBC from CDA using BPSK (i.e., 576 real dimensions) and rate-1/2 turbo code (i.e., 12 bps/Hz spectral efficiency), coded BER performance close to within just about 2.5 dB from the theoretical MIMO capacity is achieved.
We study two families of error-correcting codes defined in terms of very sparse matrices. "MN" (MacKay-Neal) codes are recently invented, and "Gallager codes" were first investigated in 1962, but a...
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We study two families of error-correcting codes defined in terms of very sparse matrices. "MN" (MacKay-Neal) codes are recently invented, and "Gallager codes" were first investigated in 1962, but appear to have been largely forgotten, in spite of their excellent properties. The decoding of both codes can be tackled with a practical sum-product algorithm. We prove that these codes are "very good," in that sequences of codes exist which, when optimally decoded, achieve information rates up to the Shannon limit. This result holds not only for the binary-symmetric channel but also for any channel with symmetric stationary ergodic noise. We give experimental results for binary-symmetric channels and Gaussian channels demonstrating that practical performance substantially better than that of standard convolutional and concatenated codes can be achieved;indeed, the performance of Gallager codes is almost as close to the Shannon limit as that of turbo codes.
This paper introduces a family of error-correcting codes called zigzag codes, A zigzag code is described by a highly structured zigzag graph, Due to the structural properties of the graph, very low-complexity soft-in/...
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This paper introduces a family of error-correcting codes called zigzag codes, A zigzag code is described by a highly structured zigzag graph, Due to the structural properties of the graph, very low-complexity soft-in/soft-out decoding rules can be implemented. We present a decoding rule, based on the Max-Log-APP (MLA) formulation, which requires a total of only 20 addition-equivalent operations per information bit, per iteration. Simulation of a rate-1/2 concatenated zigzag code with four constituent encoders with interleaver length 65 536, yields a bit error rate (BER) of 10(-5) at 0.9 dB and 1.4 dB away from the Shannon limit by optimal (APP) and low-cost suboptimal (MLA) decoders, respectively. A union bound analysis of the bit error probability of the zigzag code is presented. It is shown that the union bounds for these codes can be generated very efficiently. It is also illustrated that, for a fixed interleaver size, the concatenated code has increased code potential as the number of constituent encoders increases. Finally, the analysis shows that zigzag codes with four or more constituent encoders have lower error floors than comparable turbo codes with two constituent encoders.
This paper presents a product coding scheme based on binary images of Reed-Solomon (RS) codes and single-parity-check (SPC) codes for high-speed communications. Utilizing the special selection of components, we propos...
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This paper presents a product coding scheme based on binary images of Reed-Solomon (RS) codes and single-parity-check (SPC) codes for high-speed communications. Utilizing the special selection of components, we propose hybrid soft- and hard-decision iterative decoding (ID) algorithms for these codes, during which many RS component decoders can be early terminated. The proposed hybrid ID only exchanges ternary messages between component decoders and early stops the RS component decoders satisfying a proposed stopping criterion, thus low hardware and computational complexities are guaranteed. The hybrid ID of RS-SPC product codes not only performs comparable to the soft-decision decoding of low-density parity-check (LDPC) codes and block turbo codes (BTCs), but also takes much lower computational complexity and smaller decoder data flow. We also propose semi-analytical methods to estimate the waterfall and error-floor performances of the proposed scheme, which yield relatively accurate estimated results. The simulation results and error-floor estimations indicate that some good RS-SPC product codes have very low error floors that satisfy the requirements of optical systems.
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