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Communications, 2006 23rd Biennial Symposium on

Date May 30 2006-June 1 2006

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Displaying Results 1 - 25 of 94
  • Symposium chair's message

    Publication Year: 2006 , Page(s): i - iii
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  • Organizing Committee

    Publication Year: 2006 , Page(s): iv - vi
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  • Plenary speakers

    Publication Year: 2006 , Page(s): vii
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    Provides an abstract for each of the plenary presentations and a brief professional biography of each presenter. The complete presentations were not made available for publication as part of the conference proceedings. View full abstract»

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  • Table of contents

    Publication Year: 2006 , Page(s): viii - xv
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  • Author index

    Publication Year: 2006 , Page(s): xvi - xxii
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  • Hard-Decision Performance of LDPC Codes on Binary Symmetric Channels with Small Crossover Probabilities

    Publication Year: 2006 , Page(s): 1 - 4
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (203 KB) |  | HTML iconHTML  

    Upper and lower bounds are derived on the frame error rate (FER) of low-density parity-check (LDPC) codes decoded by hard-decision iterative algorithms over binary symmetric channels (BSC). The bounds, which are tight for sufficiently small crossover probabilities of the channel, provide a good estimate of FER in this region. The derivation of the bounds is based on the enumeration of low-weight error patterns at the input of the decoder and is much less complex than the conventional Monte Carlo simulation in the crossover probability range of interest. The proposed method can be applied to any LDPC code and for any decoding algorithm View full abstract»

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  • Performance Bounds for Multilevel LDPC Coded Modulation

    Publication Year: 2006 , Page(s): 5 - 9
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    This paper investigates multilevel coded modulation with multistage decoding, where finite-length low-density parity check (LDPC) codes are used as component codes. The systems under consideration are different from the conventional multilevel coded modulation by the fact that more than one coded bit of a component code are mapped to the labeling bits of the signal constellation. The union bound on the bit error probability for each decoding stage is derived. The tightness of the bounds is verified against the simulation results on the error performance of the ordered statistic decoding (OSD) and sum-product decoding View full abstract»

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  • Capacity-Approaching LDPC Codes with Low Error Floors for High-Speed Digital Communications

    Publication Year: 2006 , Page(s): 10 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (189 KB) |  | HTML iconHTML  

    This paper discusses the design of capacity-approaching irregular low density parity check (LDPC) codes constructed from circulant permutation matrices with low error floors. The experimental results indicate that the performance in the waterfall region of the error curve can be improved by increasing the maximum column degree or by decreasing the fraction of columns with maximum degree in the parity check matrix. To delay the onset of the error floor, several techniques in code constructions are proposed to optimize both the degree distributions and the cycle structures of irregular codes. Having encoder architectures supporting throughputs in the Gbits/s region, the proposed codes are suitable for high-speed applications of various digital communications View full abstract»

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  • Low-Density Parity-Check Codes for Discretized Min-Sum Decoding

    Publication Year: 2006 , Page(s): 14 - 17
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (194 KB) |  | HTML iconHTML  

    The performance of low-density parity-check (LDPC) codes transmitted over a memoryless binary-input continuous output additive white Gaussian noise (AWGN) channel and decoded with quantized min-sum decoding is strongly influenced by the decoder's quantization scheme. This paper presents an efficient algorithm that determines the best uniform scalar quantizer for a particular code. To maximize performance, it is necessary to determine degree distributions that best match the characteristics of the quantized min-sum decoder. Toward this end, an iterative optimization framework that jointly optimizes the degree distributions and the quantizer is presented View full abstract»

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  • A New Fast Generalized Sphere Decoding Algorithm for Under-Determined MIMO Systems

    Publication Year: 2006 , Page(s): 18 - 21
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (243 KB) |  | HTML iconHTML  

    Generalized sphere decoding (GSD) algorithms have been applied to decode the under-determined MIMO systems. It detects the transmitting vector by decoding a sequence of determined subproblems. In this paper a fast recursive GSD algorithm is proposed. This new algorithm can generate the sequence of determined subproblems in a more efficient way than the current algorithms. A column-reordering strategy for the channel matrix is incorporated into the reduction process of the new algorithm, which can significantly reduce the computational cost. Furthermore, a method to determine a good initial radius of the hyper-sphere is given. Numerical simulations show that the new recursive GSD algorithm can be significantly faster than the current algorithms View full abstract»

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  • Multi-Keyholes and Measure of Correlation in MIMO Channels

    Publication Year: 2006 , Page(s): 22 - 25
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (263 KB) |  | HTML iconHTML  

    Keyhole MIMO channels were predicted theoretically and also observed experimentally. However, they are not often encountered in practice since the assumption of a single propagation eigenmode is only a rough approximation of real propagation environments. This paper presents an extension to the single-keyhole channel model, termed a "multi-keyhole channel", which includes a number of statistically independent keyholes. Correlated full-rank and rank-deficient multi-keyhole channels are considered in detail. Under some general conditions the full-rank multi-keyhole channel is asymptotically Rayleigh fading if the number of keyholes is large. When the number of both Tx and Rx antennas is large, the capacity of a rank-deficient multi-keyhole channel is a sum of the capacities of the equivalent single-keyhole channels. The outage capacity distribution of both full-rank and rank-deficient multi-keyhole channels is asymptotically Gaussian. Based on the asymptotic capacity analysis, full ordering scalar measures of MIMO channel correlation and power imbalance are introduced View full abstract»

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  • A Low-Complexity Iterative Receiver for Multiuser Space-Time Coding Systems

    Publication Year: 2006 , Page(s): 26 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (261 KB) |  | HTML iconHTML  

    Iterative processing has been shown to be very effective in multiuser space-time block coding (STBC) systems, where each user employs channel coding and iterations are performed between the soft-output multiuser detector and the soft-input soft-output channel decoders. The complexity of an iterative receiver depends heavily on how the log-likelihood ratios (LLRs) are computed for users' coded bits in order to implement the iterations. The use of sigma mapping for M-QAM constellations is proposed in this paper to ease the computation of the LLRs and allow bit-level interference cancellation in the iterative processing. It is demonstrated that the proposed iterative receiver performs very close to the conventional one, but with a much less computational complexity View full abstract»

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  • User Selection and Signaling Over Time-Varying MIMO Broadcast Channels

    Publication Year: 2006 , Page(s): 31 - 34
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    Communication over time-varying multiple input multiple output (MIMO) broadcast channels with zero-forcing beamforming (ZFBF) is considered. Different kinds of user selection algorithms are studied and the impact of channel time variation in the presence of outdated channel state information (CSI) is evaluated both analytically and experimentally through Monte-Carlo simulation. In each user selection algorithm, M beamforming directions are selected, where M indicates the number of transmit antennas. Each active beamforming direction utilizes fixed-rate block coded modulation (BCM) scheme. It is assumed that the perfect CSI is known at the beginning of each block, while the channel varies over time. The effect of channel aging is modeled as an additive noise with time-varying power. We introduce a new method based on Hadamard transformation in order to equalize the noise power across the coding block. The performance of BCM scheme is studied using the pairwise error probability, showing that the proposed method results in a significant improvement in the error performance with a negligible increase in the complexity View full abstract»

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  • A Low Power 3.12Gbit/s/Channel Parallel Optical Receiver for Very Short Reach (VSR) Applications

    Publication Year: 2006 , Page(s): 35 - 38
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB) |  | HTML iconHTML  

    A truly-differential transimpedance amplifier (TIA) for optical receiver front-ends based on common-gate topology is fabricated and tested. -16 dBm sensitivity is achieved for this inductorless TIA at 3.125 Gbit/s while drawing 3.7 mA current from a 1.2 V power supply. The channel power consumption is 22 mW including an input buffer (IB), a limiting amplifier (LA), and a current-mode-logic (CML) output buffer with a 400 mV peak-to-peak differential output swing. We present a method to convert pseudo-differential signals into truly-differential signals by using AC coupling techniques. Also a new method of measuring cross-talk power penalty with an on-chip pseudo-random-bit-sequence (PRBS) generator is introduced. The circuits are implemented in the IBM CMRF8SF-DM 0.13-mum complementary-metal-oxide-semiconductor (CMOS) process View full abstract»

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  • Efficient Optical Time Division Multiplexing Scheme Using Solition Interaction

    Publication Year: 2006 , Page(s): 39 - 42
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (778 KB) |  | HTML iconHTML  

    A soliton multiplexing scheme to minimize the time-bandwidth product (TBP) is proposed. The soliton multiplexer consisting of a highly nonlinear fiber (HNLF) combines two adjacent fundamental solitons to form a composite soliton. The soliton demultiplexer consisting of a similar HNLF separates the fundamental solitons. The theoretical analysis and numerical simulation results demonstrate that this soliton multiplexing scheme offers high time-bandwidth efficiency, which makes it an attractive candidate for meeting the challenge of increasing demand on bandwidth View full abstract»

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  • Impact of the Input Pulse Width on the Performance of a 10 Gb/s SOA-DI Wavelength Converter

    Publication Year: 2006 , Page(s): 43 - 46
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    For a wavelength converter based on a semiconductor optical amplifier and a delayed interferometer, the performance implications of the pulse width for a 10 Gb/s RZ input signal are studied experimentally and theoretically. As the pulse width increases, the wavelength converted signal exhibits an increasingly pronounced pattern effect and decrease in the Q-factor. This is caused by the gain/phase recovery time of the semiconductor optical amplifier. The experimental and theoretical results indicate that pulse widths of 15-25 ps are required in order to avoid a penalty in performance View full abstract»

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  • Impact of Component Mismatch on the BER Performance of 2D Wavelength-Time Bipolar OCDMA Systems

    Publication Year: 2006 , Page(s): 47 - 50
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (347 KB) |  | HTML iconHTML  

    We develop a simulation platform for investigating the impact of component mismatch, caused by wavelength and/or time misalignments in the optical encoders/decoders or misbalance in the photodetectors, on the bit error rate (BER) system performance of 2D wavelength-time bipolar OCDMA systems View full abstract»

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  • Adaptive Demodulation Performance over a Rayleigh Fading Channel

    Publication Year: 2006 , Page(s): 51 - 54
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (315 KB) |  | HTML iconHTML  

    Adaptive demodulation (ADM) is a newly proposed rate adaptive system which operates without requiring channel state information at the transmitter (unlike adaptive modulation). We consider the performance of ADM (using 16-QAM and using 16-PSK) over a Rayleigh fading channel. A methodology is presented for the receiver to effectively choose its operating region based on the observed SNR at the receiver. New results are obtained for the spectral efficiency of the ADM system for both uncoded and coded bits View full abstract»

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  • Incremental Redundancy via Check Splitting

    Publication Year: 2006 , Page(s): 55 - 58
    Cited by:  Papers (6)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (215 KB) |  | HTML iconHTML  

    A new method of creating rateless codes for noisy channels is presented. Unlike puncturing, where every punctured variable disables several checks, or extending, which creates many cycles in the code graph or creates parity checks with insufficient weight, the proposed method uses check splitting to lower the rate of the code. Check splitting operates by replacing a row r of maximum weight in the parity check matrix with two new rows s1 and s2, of approximately equal weight and with s1opluss2=r. This causes the check-node degree-distribution to remain fairly concentrated and prevents cycles from forming as the rate decreases. This scheme performs closer to capacity than Raptor codes, it can use a linear-time-encodable code such as a repeat-accumulate code, and it has nearly constant decoding complexity per information bit per iteration, independent of the effective code rate View full abstract»

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  • When is a Message Decodable Over Fading Channels?

    Publication Year: 2006 , Page(s): 59 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (267 KB) |  | HTML iconHTML  

    We investigate the distribution of decoding times for frequency-flat fading channels when the information block size is fixed to a finite value a priori but codeword length is not. We characterize the distribution of decoding times for block-fading channels in a computable form and demonstrate that the resulting distribution is discontinuous at block boundaries. We make suggestions regarding coding strategies based on these distributions and discuss the benefits of rateless coding in this setting View full abstract»

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  • A Lower Bound on the Minimum Distance of a 1-Generator Quasi-Cyclic Code

    Publication Year: 2006 , Page(s): 63 - 65
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (166 KB) |  | HTML iconHTML  

    Let Fq be the finite field of q elements and A=Fq [X]/(Xn-1) be the algebra of q-ary polynomials modulo X n-1. The 1-generator quasi-cyclic (QC) code of block length nm over Fq, of index a divisor of m, with generator alowbar(X)=(ai(X))0 m-1 is the A-cyclic submodule of Am defined as Aalowbar(X)={(lambda(X)ai(X))0 m-1 ,lambda(X)isin A}, under the module operation lambda(X)Sigmai=0 mai(X)Yi =Sigmai=0 m-1lambda(X)ai(X)Y i lambda(X)isinA, (a0(X),a1(X),..., am-1(X))isinAm, where lambda(X)ai(X) is reduced modulo Xn-1. Assuming that g.c.d(n,q)=1, we show that the projections of a q-ary 1-generator QC code V according to its components are q-ary cyclic codes. Based on this property, we determine a lower bound on the minimum distance of a 1-generator QC code by means of this generator View full abstract»

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  • Information Rates for the Relay Channel with Confidentiality

    Publication Year: 2006 , Page(s): 66 - 70
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    The problem of the relay channel with confidentiality was first formulated by Oohama in 2001, at which time an inner bound for the capacity region was stated. However, a proof of this inner bound remained unavailable in the literature, a fact that has hindered the development of further results involving more complex cooperative diversity channels. In this paper, we prove the inner bound on the capacity of the relay channel with confidentiality by using typical sequence decoding. We also generalize it by introducing an auxiliary random variable, and prove a corollary lower bound on the secret capacity of the channel View full abstract»

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  • Cooperative Networks with Multiuser Diversity

    Publication Year: 2006 , Page(s): 71 - 74
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (321 KB) |  | HTML iconHTML  

    In order to improve the diversity order of a cooperative network, this paper presents a new scheme which combines multiuser diversity with the amplify-and-forward protocol. We derive an asymptotic expression of the average symbol error rate (SER) to analyze the diversity order. Through the analysis and simulations, it is shown that the new scheme substantially improves the diversity order of a cooperative network. In addition, an optimal power allocation algorithm is proposed View full abstract»

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  • Evaluation of Game Theoretic Approaches to Cooperative Wireless Network Design

    Publication Year: 2006 , Page(s): 75 - 79
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (223 KB) |  | HTML iconHTML  

    This paper serves to illustrate the sensitivity of the game theoretic approach to the choice of utility functions. The paper develops several seemingly rational utility functions which result in significantly different network characteristics. The paper also shows that while such an approach may increase utility, measures of communication performance may actually worsen View full abstract»

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  • Relaying in Wireless Sensor Networks with Interference Mitigation

    Publication Year: 2006 , Page(s): 80 - 83
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (347 KB) |  | HTML iconHTML  

    We study the use of wireless relay channel in a one-hop sensor network with random packet arrival. Exploiting regular sensor nodes to serve in a wireless relay channel can increase the overall network capacity. However, due to asynchronous source transmission, the relays interfere with each other's transmission and reception. The fundamental trade-off between these two issues leads us to an optimization problem in which we find the optimum relay zone radius to maximize the overall sum rate of the network. We also propose a MAC protocol to choose the optimum number of sources allowed to transmit under this setting. The overall system capacity is proven to increase significantly under the proposed scheme, compared with cases where relay nodes are not exploited or where the relay zone radius is suboptimal View full abstract»

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