IEEE Transactions on Communications

In this letter, we propose a systematic design of space-time block codes (STBC) which can achieve high rate and full diversity when the partial interference cancellation (PIC) group decoding is used at receivers. The proposed codes can be applied to any number of transmit antennas and admit a low decoding complexity while achieving full diversity. For M transmit antennas, in each codeword real and... View full abstract»

An approximate upper bound is derived to the maximum likelihood decoding threshold of weighted nonbinary repeat-accumulate (WNRA) codes over GF(q) with q-ary orthogonal modulation and coherent detection over the additive white Gaussian noise channel. As with binary RA codes, WNRA codes show the potential for achieving the channel capacity with decreasing code rate for large enough q. View full abstract»

It is known that an (n,n-1) non catastrophic antipodal punctured convolutional encoder of memory m is minimal. That is, the corresponding code cannot be produced by an encoder of smaller memory size. In this letter it is shown that the trellis module of a code produced by an (n,n-1) non catastrophic punctured convolutional encoder is optimum, if and only if the encoder is antipodal. View full abstract»

This Letter considers the finite-length analysis of iterative decoding of low-density parity-check codes under differential binary-phase-shift-keying (DBPSK) and differential quadrature-phase-shift-keying (DQPSK) over the noncoherent additive-white-Gaussian-noise channel. Specifically, we derive the weight of the pseudocodewords of a Tanner graph under these signaling schemes and use them to expla... View full abstract»

In multiple-input multiple-output (MIMO) systems, lattice reduction significantly improves the performance of approximate detection techniques. Taking advantage of the temporal correlation of a Rayleigh fading channel, low complexity lattice reduction is investigated in this work by adaptively updating the reduced lattice basis. We show that a careful use of previous channel realizations yields a ... View full abstract»

This paper studies the optimization problem for joint precoding design in a multi-antenna downlink channel using relaying. We formulate the joint source and relay precoding design by aiming at sum capacity maximization. Since this problem is in general nonconvex, we first convert this problem into standard convex quadratic programs, and then propose an iterative joint precoding optimization algori... View full abstract»

Log-likelihood ratio (LLR) computation for non-binary modulations over fading channels is complicated. A measure of LLR accuracy on asymmetric binary channels is introduced to facilitate good LLR approximations for non-binary modulations. Considering piecewise linear LLR approximations, we prove convexity of optimizing the coefficients according to this measure. For the optimized approximate LLRs,... View full abstract»

In this paper, a low-complexity routing strategy is introduced for a hybrid network in which n wireless nodes are randomly located and multiple base stations (BSs) are used. We allow different transmission rates according to the geographic location of each source in the network. Our achievable scheme consists of the following two routing schemes: a BS-based single-hop (SH) routing in the up/downli... View full abstract»

To provide differential quality-of-service in optical code-division multiple access, variable-weight codes were proposed and analyzed under a conventional assumption of identical power in every optical pulses (i.e., same chip power). To account for power limit of some laser sources, we assume the use of same optical power in each bit duration (i.e., same bit power) in this paper. For illustration,... View full abstract»

In this work, an allele gene adaptive mutation (AGAM) and a schemata crossover (SC) operators are designed to improve the performance of the conventional genetic algorithm (GA) and applied to the code design. Specifically, the proposed AGAM exploits both global and local information of the population to maintain an appropriate level of diversity throughout the search process. The SC utilizes high-... View full abstract»

Connectivity patterns in intermittently-connected mobile networks (ICMN) can be modeled as edge-Markovian dynamic graphs. We propose a new model for epidemic propagation on such graphs and calculate a closed-form expression that links the best achievable delivery ratio to common ICMN parameters such as message size, maximum tolerated delay, and link lifetime. These theoretical results are compared... View full abstract»

To overcome the problem that the transmission rate of a multicast channel is limited by the user with the worst channel quality, which causes the total system throughput to be low, the use of both multicast and unicast channels for multicast service is considered in this letter. Unicast channels, in addition to a multicast channel, are allocated to users with signal-to-noise ratios (SNRs) lower th... View full abstract»

We establish in closed-form the capacity and the optimal signaling scheme for a MISO channel with per-antenna power constraint. Two cases of channel state information are considered: constant channel known at both the transmitter and receiver, and Rayleigh fading channel known only at the receiver. For the first case, the optimal signaling scheme is beamforming with the phases of the beam weights ... View full abstract»

Beamforming techniques that employ Singular Value Decomposition (SVD) are commonly used in Multi-Input Multi-Output (MIMO) wireless communication systems. In the absence of channel coding, when a single symbol is transmitted, these systems achieve the full diversity order provided by the channel; whereas when multiple symbols are simultaneously transmitted, this property is lost. When channel codi... View full abstract»

We investigate a promising coding scheme over channels impaired by insertion, deletion, and substitution errors, i.e., interleaved concatenation of an outer low-density parity-check (LDPC) code with error-correction capabilities and an inner marker code for synchronization purposes. To limit the decoding latency, we start with a single-pass decoding algorithm, that is, marker code-based synchroniz... View full abstract»

The Gamma-Gamma (Γ Γ ) distribution has recently attracted the interest of the research community due to its involvement in various communication systems. In the context of RF wireless communications, Γ Γ distribution accurately models the power statistics in composite shadowing/fading channels as well as in cascade multipath fading channels, while in optical wireless (... View full abstract»

This paper studies the Demmel condition number of Wishart matrices, a quantity which has numerous applications to wireless communications, such as adaptive switching between beamforming and diversity coding, link adaptation, and spectrum sensing. For complex Wishart matrices, we give an exact analytical expression for the probability density function (p.d.f.) of the Demmel condition number, and al... View full abstract»

We analyze the effect of Wiener phase noise on the capacity and signal-to-interference-plus-noise (SINR) ratio. Our analysis includes phase noise at the transmitter and receiver end of an OFDM communication link. We see that the capacity and SINR are random variables whose distribution depends on the phase noise and the fading channel. Using a Taylor series approximation, we show that the random v... View full abstract»

We report here that channel power gain and Root-Mean-Square Delay Spread (RMS-DS) in Low/Medium Voltage power line channels are negatively correlated lognormal random variables. Further analysis of other wireline channels allows us to report a strong similarity between some properties observed in power line channels and the ones observed in other wireline channels, e.g. coaxial cables and phone li... View full abstract»

Distributed beamforming using multiple relay nodes is an effective means to provide power efficient transmission with diversity gain. Various approaches have been proposed to decide relay weights for each relay so that they can cooperatively relay signals. The maximum signal-to-noise ratio (MSNR) has been widely adopted as a performance measure in deciding relay weights. In this paper, we adopt th... View full abstract»

This study presents several schemes for adaptively allocating the number of ultra wideband (UWB) pulses used by each node within a wireless sensor network (WSN) in such a way as to enhance the detection performance while simultaneously satisfying a constraint imposed on the maximum number of pulses consumed. The study focuses on WSNs in which the data communications take place over multipath fadin... View full abstract»

We propose an adaptive transmission technique for free space optical (FSO) systems, operating in atmospheric turbulence and employing subcarrier phase shift keying (S-PSK) intensity modulation. Exploiting the constant envelope characteristics of S-PSK, the proposed technique offers efficient utilization of the FSO channel capacity by adapting the modulation order of S-PSK, according to the instant... View full abstract»

Building on the Ethernet Passive Optical Network (EPON) and Gigabit PON (GPON) standards, Next-Generation (NG) PONs (i) provide increased data rates, split ratios, wavelengths counts, and fiber lengths, as well as (ii) allow for all-optical integration of access and metro networks. In this paper we provide a comprehensive probabilistic analysis of the capacity (maximum mean packet throughput) and ... View full abstract»