Combined Channel Coding Research Articles

Complex Field Network Coding for Multi-Source Multi-Relay Single-Destination UAV Cooperative Surveillance Networks

Relay-based cooperative communication for unmanned aerial vehicle (UAV) networks can obtain spatial diversity gains, expand coverage, and potentially increase the network capacity. A multi-source multi-relay single-destination structure is the main topology structure for UAV cooperative surveillance networks, which is similar to the structure of network coding (NC). Compared with conventional NC schemes, complex field network coding (CFNC) can achieve a higher throughput and is introduced to surveillance networks in this paper. According to whether there is a direct communication link between any source drone and the destination, the information transfer mechanism at the downlink is set to one of two modes, either mixed or relay transmission, and two corresponding irregular topology structures for CFNC-based networks are proposed. Theoretical analysis and simulation results with an additive white Gaussian noise (AWGN) channel show that the CFNC obtains a throughput as high as 1/2 symbol per source per channel use. Moreover, the CFNC applied to the proposed irregular structures under the two transmission modes can achieve better reliability due to full diversity gain as compared to that based on the regular structure. Moreover, the reliability of the CFNC scheme can continue to be improved by combining channel coding and modulation techniques at the expense of rate loss.

A Source and Channel Coding Approach for Improving Flash Memory Endurance

The introduction of multiple-level cell (MLC) and triple-level cell (TLC) technologies reduced the reliability of flash memories significantly compared with single-level cell flash. With MLC and TLC flash cells, the error probability varies for the different states. Hence, asymmetric models are required to characterize the flash channel, e.g., the binary asymmetric channel (BAC). This contribution presents a combined channel and source coding approach improving the reliability of MLC and TLC flash memories. With flash memories data compression has to be performed on block level considering short-data blocks. We present a coding scheme suitable for blocks of 1 kB of data. The objective of the data compression algorithm is to reduce the amount of user data such that the redundancy of the error correction coding can be increased in order to improve the reliability of the data storage system. Moreover, data compression can be utilized to exploit the asymmetry of the channel to reduce the error probability. With redundant data, the proposed combined coding scheme results in a significant improvement of the program/erase cycling endurance and the data retention time of flash memories.

The Generalized Stochastic Likelihood Decoder: Random Coding and Expurgated Bounds

The likelihood decoder is a stochastic decoder that selects the decoded message at random, using the posterior distribution of the true underlying message given the channel output. In this paper, we study a generalized version of this decoder, where the posterior is proportional to a general function that depends only on the joint empirical distribution of the output vector and the code word. This framework allows both mismatched versions and universal versions of the likelihood decoder, as well as the corresponding ordinary deterministic decoders, among many others. We provide a direct analysis method that yields the exact random coding exponent (as opposed to separate upper bounds and lower bounds that turn out to be compatible, which were derived earlier by Scarlett et al. ). We also extend the result from pure channel coding to combined source and channel coding (random binning followed by random channel coding) with side information available to the decoder. Finally, returning to pure channel coding, we derive also an expurgated exponent for the stochastic likelihood decoder, which turns out to be at least as tight (and in some cases, strictly so) as the classical expurgated exponent of the maximum likelihood decoder, even though the stochastic likelihood decoder is suboptimal.

Generalized Joint Channel–Network Coding in Asymmetric Two-Way Relay Channels

Combining channel coding and network coding in a physical layer in a fading channel, generalized joint channel-network coding (G-JCNC) is proved to highly perform in a two-way relay channel (TWRC). However, most relevant discussions are restricted to symmetric networks. This paper investigates the G-JCNC protocols in an asymmetric TWRC (A-TWRC). A newly designed encoder used by source nodes that is dedicated to correlate codewords with different orders is presented. Moreover, the capability of a simple common non-binary decoder at a relay node is verified. The effects of a power match under various numbers of iteration and code lengths are also analyzed. The simulation results give the optimum power match ratio and demonstrate that the designed scheme based on G-JCNC in an A-TWRC has excellent bit error rate performance under an appropriate power match ratio.

A Joint Coding Method Based on Rateless Coding and Channel Coding at Network Layer

Decoding overhead is a standard for measuring whether rateless coding is good or not. The product-code coding of Shifted RSD, a communication transmission scheme, is based on the joint decoding of rateless coding and channel coding at the network layer of feedback information, was proposed in this study in order to reduce the overhead of decoding in rateless coding in the wireless communication. This method combines rateless coding and channel coding at the network layer to decode, which results in multiple packets instead of one recovered by iterative decoding every time during decoding. The decoding is accomplished until all packets are decoded, and the original information of source is recovered. The decoding overhead used for recovering the original information can be reduced due to the increase in the number of packets recovered at a time. Experimental results show that the use of this method combining channel coding with rateless coding to decode requires less decoding overhead than using LT code or RSD code with feedback for decoding, thus improving the decoding capability of the receiving end.

Implementation of Physical Layer Key Distribution using Software Defined Radios

It was well known from Shannon’s days that characteristics of the physical channel like attenuation, fadingand noise can impair reliable communication. But it was more recently that the beneficial side effects of channelcharacteristics in ensuring secret communication started getting attention. Studies have been made to quantify theamount of secrecy that can be reaped by combining channel coding with security protocols. The Wiretap channelproposed by Wyner is arguably one of the oldest models of physical layer security protocols. In this paper, wepresent a brief tutorial introduction to the Wiretap channel, followed by an application of the physical layer modelto a class of Key Distribution protocols. We present results from an implementation of key distribution protocolsusing Software Defined Radio tools along with physical RF hardware peripherals. We believe this approach is muchmore tangible and informative than computer based simulation studies. Defence Science Journal, 2013, 63(1), pp.6 -14 , DOI:http://dx.doi.org/10.14429/dsj. 63.3758

Quasi-cyclic Random Projection Code and Hardware Implementation

Random Projection Code (RPC) is a mechanism that combines channel coding and modulation together and realizes rate adaptation in the receiving end. Random projection code’s mapping matrix has significant influences on decoding performance as well as hardware implementation complexity. To reduce hardware implementation complexity, we design a quasi-cyclic mapping matrix for RPC codes. Compared with other construction approaches, our design gets rid of data filter component, thus reducing chip area 7284.95 um2, and power consumption 331.46 uW in 0.13 um fabrication. Our simulation results show that our method does not cause any performance loss and even gets 0.2 dB to 0.5 dB gain at BER 10-4.

Performance Bounds for Combined Channel Coding and Space–Time Block Coding With Receive Antenna Selection

This paper studies the performance of the concatenation of an outer channel code with an orthogonal space-time block code (STBC), where the outer code can be a convolutional code (CC) or a trellis-coded modulation (TCM) code. In particular, upper bounds on the bit error rate (BER) for this concatenation scheme with receive antenna selection are derived. In the analysis, the authors assume that 1) the receiver uses only L out of the available M receive antennas, where, typically, L/spl les/M; 2) the selected antennas are those that maximize the instantaneous received signal-to-noise ratio (SNR); 3) the channel state information is perfectly known at the receiver; 4) the underlying channel is fully interleaved; and 5) the underlying orthogonal STBC is full rate. An explicit upper bound on the BER for the above concatenation scheme for any N, M, and L is derived, where N denotes the number of transmit antennas. It has been shown that the diversity order with antenna selection is the same as that of the full-complexity system, whereas the deterioration in SNR is upper bounded by 10log/sub 10/(M/L) dB. The authors also derive a tighter upper bound on the BER for the Alamouti scheme when the receiver uses the best antenna, i.e., L=1. These upper bounds can be extended in a straightforward manner to other types of outer codes and fading channels, including fast, block, and slow fading channels. Finally, simulation results that validate the analysis are derived.

Interference suppressing for cellular MIMO system based on turbo receiver

Space-Time Coding (STC), which combines channel coding, modulation, and multiple transmit antennas, is a powerful scheme to achieve higher data rates and combat fading in wireless systems. In this paper, we propose a soft/cancellation turbo equalization scheme to suppress Co-Channel Interference (CCI) in STC systems. The simulation results show that the proposed method significantly improves the system’s ability of interference suppression, while preserving the space-time structure.

Optimising the combined source and channel coding of a discrete communication system

The problem of optimising the structure of the encoder/decoder pair in a discrete communication system, with an additive distortion measure, is formulated in terms of a quadratic programming (QP) problem. This new formulation benefits from the following special features: it optimises the joint effects of the source/channel coding on the end-to-end distortion; and the encoder and the decoder structures are not restricted to being the inverse of each other. A method which obtains an ɛ-minimiser approximation of an optimum point of a general QP problem is discussed. Some simulation results based on this method are also given.

Adaptive cochannel interference cancellation in space-time coded communication systems

Space-time coding is a powerful scheme that combines channel coding, modulation, and multiple transmit antennas to achieve higher data rates and combat fading in wireless systems. In this letter, we propose a multiple-input multiple-output minimum mean-square error spatial-filtering-based adaptive antenna arrays method to suppress cochannel interference (CCI) in space-time coded systems. It is shown that the proposed method can effectively suppress CCI while preserving the space-time structure, thereby significantly improving the system's interference suppression ability without significant bit error rate performance degradation.

Maximum Likelihood Blind Channel Estimation for Space-Time Coding Systems

Sophisticated signal processing techniques have to be developed for capacity enhancement of future wireless communication systems. In recent years, space-time coding is proposed to provide significant capacity gains over the traditional communication systems in fading wireless channels. Space-time codes are obtained by combining channel coding, modulation, transmit diversity, and optional receive diversity in order to provide diversity at the receiver and coding gain without sacrificing the bandwidth. In this paper, we consider the problem of blind estimation of space-time coded signals along with the channel parameters. Both conditional and unconditional maximum likelihood approaches are developed and iterative solutions are proposed. The conditional maximum likelihood algorithm is based on iterative least squares with projection whereas the unconditional maximum likelihood approach is developed by means of finite state Markov process modelling. The performance analysis issues of the proposed methods are studied. Finally, some simulation results are presented.

Robust image transmission using JPEG2000 and turbo-codes

A method of combined source and channel coding is described that provides robustness to errors from a binary symmetric channel and uses the JPEG2000 (JP2) image compression standard. The source code rate and channel code rate are jointly optimized to produce a stream of fixed-size channel packets, such that the rate allocation complexity grows O(N/sup 2/) with the number of transmitted packets, N. Punctured turbo codes are used for channel coding, providing strong error protection. The rate allocation scheme presented obtains all necessary information from the JP2 encoder, and does not require image decompression.

Semiblind space–time decoding in wireless communications: a maximum likelihood approach

It has been recently shown that deploying multiple transmitting and receiving antennae can substantially improve the capacity of multipath wireless channels if the rich time-scattering is properly exploited. Space–time coding (STC) is a novel proposal that combines channel coding techniques suitable for multiple transmitting elements with signal processing algorithms that exploit the spatial and temporal diversity at the receiver. In this paper, we focus on the signal processing perspective and propose a novel space–time semiblind decoding scheme that performs maximum likelihood (ML) based channel estimation and data detection. The multiple input multiple output (MIMO) time-scattering channel is estimated using a block iterative expectation-maximization (EM) algorithm that fully exploits the statistical features of the transmitted signal together with the knowledge of a small number of transmitted symbols, hence the term semiblind. Data detection is efficiently carried out using the Viterbi algorithm. In order to reduce the computational load of the receiver, a modification of the EM algorithm with a potentially lower complexity is also suggested. Computer simulations show that the proposed semiblind decoder clearly outperforms conventional receivers that estimate the channel parameters exclusively from the a priori known transmitted symbols.

Operational rate-distortion performance for joint source and channel coding of images

This paper describes a methodology for evaluating the operational rate-distortion behavior of combined source and channel coding schemes with particular application to images. In particular, we demonstrate use of the operational rate-distortion function to obtain the optimum tradeoff between source coding accuracy and channel error protection under the constraint of a fixed transmission bandwidth for the investigated transmission schemes. Furthermore, we develop information-theoretic bounds on performance for specific source and channel coding systems and demonstrate that our combined source-channel coding methodology applied to different schemes results in operational rate-distortion performance which closely approach these theoretical limits. We concentrate specifically on a wavelet-based subband source coding scheme and the use of binary rate-compatible punctured convolutional (RCPC) codes for transmission over the additive white Gaussian noise (AWGN) channel. Explicit results for real-world images demonstrate the efficacy of this approach.

Robust video transmission over correlated mobile fading channels

We develop a unique set of techniques to support reliable and efficient video transmission over bandwidth-limited mobile networks. The video coder is based on the H.263 coding standard, while its transmission system design is based on a joint study of combined source and channel coding, diversity reception, and pre/postprocessing techniques. In particular, a finite-state Markov model for representing a correlated fading channel with diversity is developed. Based on this model, a recursive algorithm is further devised for an efficient estimation of block-code performance. By doing so, an important means for finding proper diversity and channel coding schemes for correlated video data in correlated fading channels is obtained. In addition, robust decoding together with a combined spatial-temporal concealment is employed to mitigate the effects of decoding mismatch caused by residual errors. Simulation results confirm that the proposed system can significantly reduce the bursty error effects on the H.263 coded video data while maintaining high transmission efficiency.

Mobile image transmission using combined source and channel coding with low complexity concealment

In this paper, we propose an efficient image transmission system for reliable transmission of vulnerable compressed images over mobile radio channels. The image coder is fully compatible with the JPEG baseline coding standard. Its transmission system is designed based on lossy transmission with combined source and channel coding (CSCC) and low complexity error concealment. Specifically, the proposed CSCC uses block codes which are designed to match both the coded image characteristics and wireless channel statistics, thereby accomplishing efficient transmission along with good visual quality. Together with a block-shuffling scheme, a simple error-concealment technique is introduced to effectively reconstruct the damaged image blocks caused by the residual errors. It is shown that the proposed techniques are applicable to mobile image transmission with different compression ratios under various mobile channel conditions. Performance results based on images `LENA' and `AIRPLANE', which are coded at 0.85 and 0.90 bit/pixel, respectively, under the simulated GSM channel (Pan-European Cellular Standard) with an average SNR (signal-to-noise ratio) of 18 dB and various vehicle speeds (2–50 miles/h) indicate that the proposed system achieves a throughput as high as 70% with good visual quality at PSNRs (peak signal-to-noise ratio) around 30 dB for the reconstructed images.

Reliable Speech Transmission Using Combined Adaptive-rate Sampling (ARS) and Channel Coding

A novel speech transmission technique over noisy channel condition based on combined ARS and channel coding schemes is described. The proposed scheme is suitable for time varying channels with some form of ARQ facilities. It is shown that under an AWGN channel condition, up to 3.8 dB gain relative to a conventional 32 kbits/s transmission can be provided using the combined technique.

Coded Modulations for Fading Channels: An Overview

AbstractIt is by now well known that combined channel coding and digital modulation (in short coded modulation) yield power and bandwidth efficient digital transmission schemes for the Gaussian channel. These schemes perform closer to channel capacity than those where coding and modulation are treated separately. More recently, coded modulation methods have been investigated for transmission over Rayleigh fading channels. It has been discovered that systems optimized for the Gaussian channel are not optimum for fading channels. This is primarily due to the importance of built‐in time diversity of the coded modulation scheme for fading channels.In this paper we give a brief overview of recent developments in signal design for Rayleigh fading channels. Mainly schemes based on phase shift keying are presented. Theoretical guidance for design and identification of the most important system parameters are given. A couple of detailed examples of code designs and their error probability performance are also given. Optimum and suboptimum receivers are discussed. An overview of analytical performance analysis tools, as well as code designs for both trellis coded modulation and block coded modulation is included in the paper. Methods for unequal error protection are given. Potential application areas are identified. An extensive reference list is supplied.

ARQ scheme with combined channel coding and modulation using noncoherent detection

A new method for the combination of channel coding and modulation with noncoherent detection in automatic-repeat-request protocols is described. This scheme can be used in automatic-repeat-request protocols in which each codeword is transmitted m ≥ 2 times consecutively. Theoretical analysis shows that this scheme offers a net increase in the performance with respect to other similar protocols.