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Communications, IEEE Transactions on

Issue 9 • Date September 2009

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Displaying Results 1 - 25 of 43
  • IEEE Transactions on Communications - Cover

    Publication Year: 2009 , Page(s): c1 - c3
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    Freely Available from IEEE
  • Improving the distance properties of turbo codes using a third component code: 3D turbo codes - [transactions letters]

    Publication Year: 2009 , Page(s): 2505 - 2509
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    Thanks to the probabilistic message passing performed between its component decoders, a turbo decoder is able to provide strong error correction close to the theoretical limit. However, the minimum Hamming distance (dmin) of a turbo code may not be sufficiently large to ensure large asymptotic gains at very low error rates (the so-called flattening effect). Increasing the dmin of a turbo code may involve using component encoders with a large number of states, devising more sophisticated internal permutations, or increasing the number of component encoders. This paper addresses the latter option and proposes a modified turbo code in which a fraction of the parity bits are encoded by a rate-1, third encoder. The result is a noticeably increased dmin, which improves turbo decoder performance at low error rates. Performance comparisons with turbo codes and serially concatenated convolutional codes are given. View full abstract»

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  • Expanding window fountain codes for unequal error protection

    Publication Year: 2009 , Page(s): 2510 - 2516
    Cited by:  Papers (31)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (474 KB) |  | HTML iconHTML  

    A novel approach to provide unequal error protection (UEP) using rateless codes over erasure channels, named Expanding Window Fountain (EWF) codes, is developed and discussed. EWF codes use a windowing technique rather than a weighted (non-uniform) selection of input symbols to achieve UEP property. The windowing approach introduces additional parameters in the UEP rateless code design, making it more general and flexible than the weighted approach. Furthermore, the windowing approach provides better performance of UEP scheme, which is confirmed both theoretically and experimentally. View full abstract»

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  • Comments regarding "On the performance/complexity tradeoff in block turbo decoder design

    Publication Year: 2009 , Page(s): 2517
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (90 KB) |  | HTML iconHTML  

    In this comment we position the work of Z. Chi, et al, 2004,2001 in terms of the prior literature and note that many of its results are subsumed by previous papers. View full abstract»

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  • A differential binary message-passing LDPC decoder

    Publication Year: 2009 , Page(s): 2518 - 2523
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (378 KB) |  | HTML iconHTML  

    In this paper, we propose a binary message-passing algorithm for decoding low-density parity-check (LDPC) codes. The algorithm substantially improves the performance of purely hard-decision iterative algorithms with a small increase in the memory requirements and the computational complexity. We associate a reliability value to each nonzero element of the code's parity-check matrix, and differentially modify this value in each iteration based on the sum of the extrinsic binary messages from the check nodes. For the tested random and finite-geometry LDPC codes, the proposed algorithm can perform as close as about 1 dB and 0.5 dB to belief propagation (BP) at the error rates of interest, respectively. This is while, unlike BP, the algorithm does not require the estimation of channel signal to noise ratio. Low memory and computational requirements and binary message-passing make the proposed algorithm attractive for high-speed low-power applications. View full abstract»

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  • A class of quasi-cyclic LDPC codes over GF(2m)

    Publication Year: 2009 , Page(s): 2524 - 2527
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (265 KB) |  | HTML iconHTML  

    Low Density Parity Check (LDPC) codes over GF(2m,)are an extension of binary LDPC codes. Performances of GF(2m,) LDPC codes have been shown to be higher than binary LDPC codes, but the complexity of the encoders/decoders increases. Hence there is a substantial lack of implementations for LDPC codes over GF(2m,)codes. This paper presents a class of quasi-cyclic LDPC codes over GF(2m,). These codes can alleviate the encoding/decoding complexity without excessive loss of performances. It is shown how, from a performance point of view, such codes are better than m times bigger binary codes and as good as (2m,)longer binary codes. View full abstract»

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  • Throughput maximization over slowly fading channels using quantized and erroneous feedback

    Publication Year: 2009 , Page(s): 2528 - 2533
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (357 KB) |  | HTML iconHTML  

    We design a conceptual transmission scheme that adjusts rate and power of data codewords to send them over a slowly fading channel, when quantized and possibly erroneous channel state information (CSI) is available at the transmitter. The goal is to maximize the data throughput or the expected data rate using a multi-layer superposition coding technique and temporal power control at the transmitter. The main challenge here is to design a CSI quantizer structure for a noisy feedback link. This structure resembles conventional joint source and channel coding schemes, however, with a newly introduced quasi-gray bit-mapping. Our results show that with proper CSI quantizer design, even erroneous feedback can provide performance gains. Also, with an unreliable feedback link, superposition coding provides significant gains when feedback channel is poorly conditioned and channel uncertainty at the transmitter is severe, whereas power control is more effective with more reliable feedback. View full abstract»

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  • The equivalence between slepian-wolf coding and channel coding under density evolution

    Publication Year: 2009 , Page(s): 2534 - 2540
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (231 KB) |  | HTML iconHTML  

    We consider Slepian-Wolf code design based on low density parity-check (LDPC) coset codes. The density evolution formula for Slepian-Wolf coding is derived. An intimate connection between Slepian-Wolf coding and channel coding is then established. Specifically we show that, under density evolution, each Slepian-Wolf coding problem is equivalent to a channel coding problem for a binary-input output-symmetric channel. View full abstract»

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  • Improving power efficiency of coded OFDM with feedback

    Publication Year: 2009 , Page(s): 2541 - 2544
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (281 KB) |  | HTML iconHTML  

    Coding with diversity is one of the keys to reliable wireless communication over fading channels. Adaptive modulation can provide additional performance improvement which may be significant when the channel diversity orders are small. In this letter, we propose adaptation algorithms for improving the power efficiency of coded orthogonal frequency division multiplexing (OFDM) on fading channels. We derive simple power-loading and bit-loading algorithms for achieving a fixed throughput and reliability with minimal transmitter power. We illustrate the performance of our schemes using simulations. View full abstract»

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  • Some comments on the use of markov models in communications

    Publication Year: 2009 , Page(s): 2545
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (64 KB) |  | HTML iconHTML  

    In their recent article Feng, Field and Haykin rediscovered an approach to the channel modelling based on stochastic differential equations (SDE). In the following we would like to bring readers attention to a body of literature which deals with similar subjects using SDE approach. View full abstract»

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  • Error rate analysis for peaky signaling over fading channels

    Publication Year: 2009 , Page(s): 2546 - 2550
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (334 KB) |  | HTML iconHTML  

    In this paper, the performance of signaling strategies with high peak-to-average power ratio is analyzed in both coherent and noncoherent fading channels. Two modulation schemes, namely on-off phase-shift keying (OOPSK) and on-off frequency-shift keying (OOFSK), are considered. The optimal detector structures are identified and analytical expressions for the error probabilities are obtained for arbitrary constellation sizes. Numerical techniques are employed to compute the error rates. It is concluded that increasing the peakedness of the signals results in reduced error rates for a given power level and hence equivalently improves the energy efficiency for fixed error probabilities. View full abstract»

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  • A unified framework for performance analysis of CSI-assisted cooperative communications over fading channels

    Publication Year: 2009 , Page(s): 2551 - 2557
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (341 KB) |  | HTML iconHTML  

    In this Letter, we propose a comprehensive framework for performance analysis of cooperative wireless systems using Amplify and Forward (AF) relay methods. The framework relies on the Moment Generating Function (MGF-) based approach for performance analysis of communication systems over fading channels, and on some properties of the Laplace Transform, which allow to develop a single-integral relation between the MGF of a random variable and the MGF of its inverse. Moreover, a simple lower bound for Outage Probability (Pout) and Outage Capacity (OC) computation is also introduced. Numerical and simulation results are provided to substantiate the accuracy of the proposed framework. View full abstract»

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  • Distribution of max-log metrics for QAM-based BICM in fading channels

    Publication Year: 2009 , Page(s): 2558 - 2563
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (269 KB) |  | HTML iconHTML  

    In this letter we derive closed-form expressions for the probability density functions (PDFs) of the bits' reliability metrics (L-values) in bit-interleaved coded modulation (BICM) transmission over fully-interleaved fading channels. The expressions are valid for the relevant case of quadrature amplitude modulation (QAM) with Gray mapping when the metrics are calculated via the so-called max-log approximation. Using the developed expressions, the performance of coded BICM transmissions is efficiently evaluated, i.e., without resorting to otherwise required two-dimensional numerical integration. The BICM capacity for different fading channels and constellation sizes is also evaluated. View full abstract»

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  • Reduced complexity sphere decoding via a reordered lattice representation

    Publication Year: 2009 , Page(s): 2564 - 2569
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (450 KB) |  | HTML iconHTML  

    In this letter, we propose a reordering of the channel representation for Sphere Decoding (SD) where the real and imaginary parts of each jointly detected symbol are decoded independently. Making use of the proposed structure along with a scalar quantization technique, we reduce the decoding complexity substantially. We show that this approach achieves 85% reduction in the overall complexity compared to the conventional SD for a 2 times 2 system, and 92% reduction for the 4 times 4 and 6 times 6 cases at low SNR values, and almost 50% at high SNR, thus relaxing the requirements for hardware implementation. View full abstract»

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  • Enabling differentiated services using generalized power control model in optical networks

    Publication Year: 2009 , Page(s): 2570 - 2575
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    This paper considers a generalized framework to study OSNR optimization-based end-to-end link level power control problems in optical networks. We combine favorable features of game-theoretical approach and central cost approach to allow different service groups within the network. We develop solutions concepts for both cases of empty and nonempty feasible sets. In addition, we derive and prove the convergence of a distributed iterative algorithm for different classes of users. In the end, we use numerical examples to illustrate the novel framework. View full abstract»

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  • Substream-based soft handoff in CDMA cellular networks

    Publication Year: 2009 , Page(s): 2576 - 2579
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    We present a new soft handoff scheme that enhances the reliability during soft handoff by increasing the signal distance (Euclidean and/or Hamming) in forward link code division multiple access cellular networks. Each base station participating in soft handoff sends a disjoint subset of the main data stream (called sub-stream) and the mobile receiver reassembles the sub-streams and restores the main data stream. This approach can reduce the data rate per base station by a factor of the number of participating base stations and thereby can increase the signal distance as opposed to the diversity gain. It is shown that the proposed soft handoff scheme is promising for high data rate applications which are the major interests in the next generation cellular networks. View full abstract»

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  • Antenna/relay selection for coded cooperative networks with AF relaying

    Publication Year: 2009 , Page(s): 2580 - 2584
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    In this paper, we consider antenna/relay selection for coded cooperative networks in an effort to improve their end-to-end performance by improving the detection reliability at the relay nodes. Considering amplify-and-forward (AF) relaying, we analyze a previously proposed distributed coded cooperation scheme in conjunction with antenna/relay selection. Specifically, we derive upper bounded expressions for the bit error rate assuming M-ary phase shift keying (M-PSK) transmission. Our analytical results show that the maximum diversity order of the system is maintained for the entire range of symbol error rate of interest, unlike the case without antenna/relay selection. Several numerical and simulation results are presented to demonstrate the efficacy of the proposed scheme. View full abstract»

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  • Sum-rate analysis of multiuser MIMO system with zero-forcing transmit beamforming

    Publication Year: 2009 , Page(s): 2585 - 2589
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (278 KB) |  | HTML iconHTML  

    In this letter, we present the exact sum-rate analysis of the multiuser multiple-input multiple-output (MIMO) systems with zero-forcing transmit beamforming (ZFBF). We develop the analytical expressions of the ergodic sum-rate for two low-complexity user selection strategies for the dual-transmit-antenna scenario. Based on the analytical results, we examine the parameter optimization problem to properly trade off between channel power gain and directional gain in term of maximizing the ergodic sum rate. View full abstract»

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  • Relay ordering in a multi-hop cooperative diversity network

    Publication Year: 2009 , Page(s): 2590 - 2596
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB) |  | HTML iconHTML  

    In this paper, we first propose an optimum relay ordering algorithm for the multi-branch multi-hop cooperative diversity networks. This optimum algorithm has a high complexity that makes it hard to implement. Therefore, a suboptimum relay ordering algorithm, which considerably reduces the complexity, is then developed. Furthermore, for a cooperative network with two relays, we analytically evaluate the performance of the suboptimum algorithm by using an approximate end-to-end signal-to-noise ratio expression. Specifically, an approximate probability of wrong selection and an approximate expression of the symbol error rate are derived. The analysis and the numerical results demonstrate that the suboptimum algorithm performs very well as the optimum one at a much lower complexity. View full abstract»

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  • Effect of transmit correlation on the sum-rate capacity of two-user broadcast channels

    Publication Year: 2009 , Page(s): 2597 - 2599
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (202 KB) |  | HTML iconHTML  

    This letter investigates the effect of the transmit correlation on the sum-rate capacity of a two-user broadcast channel (BC) with the use of equal-power allocation in high signal-to-noise ratio (SNR) environments. It is shown using an upper-bound analysis that the sum-rate capacity of a correlated two-user BC at high SNR highly depends on the phase difference between the transmit correlation coefficients of two users as well as the magnitude of the transmit correlation coefficients, and it is maximized (or minimized) when the principal eigenvectors of the transmit correlation matrix of two users are orthogonal (or parallel) to each other. The analytic results are verified by computer simulation. View full abstract»

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  • Polynomial based analog source-channel codes - [transactions papers]

    Publication Year: 2009 , Page(s): 2600 - 2606
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (501 KB) |  | HTML iconHTML  

    In many communication applications one is interested in transmitting a time-discrete analog-valued (i.e. continuous alphabet) source over a time-discrete analog channel. We study this problem in the case of bandwidth expansion, in the sense that one source sample, X, is transmitted over N-orthogonal channels. An analog source-channel code based on orthogonal polynomials is proposed and analyzed. The code can be generated using a Gram-Schmidt procedure, to fit virtually any source distribution. View full abstract»

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  • Data extraction from wireless sensor networks using distributed fountain codes

    Publication Year: 2009 , Page(s): 2607 - 2618
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (679 KB) |  | HTML iconHTML  

    A Wireless Sensor Network (WSN) observes a natural field and aims to recreate it with sufficient fidelity at a, perhaps distant, Fusion Center (FC) using a wireless communication channel of arbitrary capacity. We propose a universal and power efficient method for such data extraction, based on Digital Fountain Codes (DFCs) and joint-source channel decoding. Our method implements a distributed `rate-lessiquest DFC which automatically tunes the number of transmissions to the channel capacity. Furthermore, instead of directly compressing the WSN data, we achieve rate reduction by treating the spatiotemporal dependencies in the field as an outer code, and jointly decoding this concatenation at the FC using a multi-stage iterative decoder. We demonstrate that a power efficiency close to the capacity-rate-distortion limit is achieved at moderate distortion levels, irrespective of the channel capacity or field dependencies. As compared to the traditional approach of source-channel separation, the proposed data extraction scheme is particularly attractive for WSN applications due its computationally simple encoding procedure, low latency and the ability to seamlessly trade-off fidelity of reconstruction for power consumption. View full abstract»

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  • A gaussian sum approach to blind carrier phase estimation and data detection in turbo coded transmissions

    Publication Year: 2009 , Page(s): 2619 - 2632
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (621 KB) |  | HTML iconHTML  

    We present a joint phase estimation and decoding method for convolutional turbo codes in the presence of strong phase noise. In order to overcome the problem of phase ambiguity and cycle slips, a combined state-space model for the time varying phase and the component convolutional codes is introduced. The proposed algorithm uses a Gaussian sum approach to approximate the multimodal a posteriori probability density function (pdf) of the phase in a blind context. We compare our method to the well known alternative consisting in discretizing the phase.Monte-Carlo simulations for the turbo code used in the DVB-RCS standard show that the performances of the proposed scheme are close to decoding with perfect knowledge of the phase. View full abstract»

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  • Performance of vector perturbation multiuser MIMO systems with limited feedback

    Publication Year: 2009 , Page(s): 2633 - 2644
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (647 KB) |  | HTML iconHTML  

    This paper considers the multiuser multiple-input multiple-output (MIMO) Rayleigh fading broadcast channel. We consider the case where the multiple transmit antennas are used to deliver independent data streams to multiple users via a multiuser technique known as vector perturbation. We propose lattice-theoretic and rate-distortion based approaches to analyze the performance of these systems, taking into account the practical restrictions imposed by limited feedback and training. We show that performance is primarily determined by the ratio between the number of users and the number of transmit antennas. We then propose a new practical low-complexity low-rate feedback scheme, and show that the performance approaches the ideal rate-distortion based scheme. View full abstract»

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  • On channel quantization and feedback strategies for multiuser MIMO-OFDM downlink systems

    Publication Year: 2009 , Page(s): 2645 - 2654
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    We consider a multiuser MIMO-OFDM downlink system with single antenna mobile terminals (MTs) where channel state information at the base station is provided through limited uplink feedback (FB). In order to reduce the FB rate and signal processing complexity, the available bandwidth is divided into resource blocks (RBs) whose number of subcarriers reflects the coherence bandwidth of the channel. This approach is very common in the standardization of 4th generation wireless communication systems and justifies an independent channel quantization per RB. Within this framework the paper contains two main contributions. Firstly we provide joint conditions on the channel coherence bandwidth and the FB rate per RB that allow for a simpler quantization of the RB channel matrix (space-frequency) by a space vector, causing negligible performance loss in terms of system achievable throughput. This is accomplished after deriving a new metric for codebook design in RB channel quantization that exploits spatial and frequency correlation. As a second contribution we investigate the trade-off between accurate channel knowledge and frequency/multiuser diversity. It is seen that even for a moderate number of MTs in the network, concentrating all the available FB bits in characterizing only one RB provides a significant gain in system throughput over a more classical distributed approach and this result is validated both analytically and by simulations. View full abstract»

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Aims & Scope

IEEE Transactions on Communications focuses on all telecommunications including telephone, telegraphy, facsimile, and point-to-point television by electromagnetic propagation.

 

 

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Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia