Convolutionally coded binary PSAM for Rayleigh fading channels

Recently proposed, pilot symbol assisted modulation (PSAM) uses a known pilot sequence to derive amplitude and phase references at the receiver. The authors present convolutional coding for such systems and derive the exact pairwise error probability and the Chernoff upper bound of it. A comparison among PSAM, coherent and differential detected coded systems indicates that, even at 5% Doppler fading rate, coded PSAM requires 3.5 dB more than the ideal coherent case but less than the differential case.<>     

On the capacity of Rayleigh fading cooperative systems under adaptive transmission

In this letter, the use of adaptive source transmission with amplify-and-forward relaying is proposed. Three different adaptive techniques are considered: (i) optimal simultaneous power and rate adaptation; (ii) constant power with optimal rate adaptation; (iii) channel inversion with fixed rate. The capacity upper bounds of these adaptive protocols are derived for the amplify-and-forward cooperative system over both independent and identically distributed (i.i.d.) Rayleigh fading and non-i.i.d. Rayleigh fading environments. The capacity analysis is based on an upper bound on the effective received signal-to-noise ratio (SNR). The tightness of the upper bound is validated by the use of a lower bound and by Monte Carlo simulation. It is shown that at high SNR the optimal simultaneous power and rate adaptation and the optimal rate adaptation with constant power provide roughly the same capacity. Channel inversion is shown to suffer from a deterioration in capacity relative to the other adaptive techniques.     

An efficient generalized sphere decoder for rank-deficient MIMO systems

We derive a generalized sphere decoder (GSD) for rank-deficient multiple input multiple output (MIMO) systems using N transmit antennas and M receive antennas. This problem arises when N>M or when the channel gains are strongly correlated. The upper triangular factorization of the Grammian yields an under-determined system and the standard sphere decoding (SD) fails. For constant modulus constellations, we modify the maximum likelihood (ML) cost metric so that the equivalent Grammian is rank N. The resulting GSD algorithm has significantly lower complexity than previous algorithms. A method to handle nonconstant modulus constellations is also developed.     

Capacity Analysis for Transmit Antenna Selection Using Orthogonal Space-Time Block Codes

Antenna selection for multiple-input multiple-output (MIMO) where only a subset of antennas at the transmitter and/or receiver are activated for signal transmission is a practical technique for the realization of full diversity. Despite extensive research, closed-form capacity expressions for MIMO systems employing transmit antenna selection (TAS) and orthogonal space-time block codes (OSTBCs) are not available. We thus derive the exact closed-form capacity expressions when an OSTBC is employed and N transmit antennas out of total L_t antennas are selected for transmission. The expressions are valid for a frequency-flat Rayleigh fading MIMO channel and avoid numerical integration methods     

Performance Analysis of TDMA Relay Protocols Over Nakagami- $m$ Fading

Several time-division multiple-access (TDMA) cooperative wireless relay protocols and their performances have recently been developed by Nabar, Bolcskei, and Kneubuhler. Their work, however, is limited to an upper bound-based performance analysis for Rayleigh fading. We thus provide an exact analysis of two of their protocols in single-relay and multiple-relay networks over independent identically distributed (i.i.d.) Nakagami- $m$ fading channels. Our analysis is focused on an Alamouti-coded system with two-stage protocols, fixed-gain amplify-and-forward (AF) relays, and maximal ratio combiner (MRC) reception. The performance metrics are the capacity, the diversity order, and the symbol error rate (SER). The closed-form moment-generating function (MGF) of the total end-to-end signal-to-noise ratio (SNR) is derived. The MGF is then used to derive the diversity order and the SER of $M$-ary phase-shift keying ($M$-PSK) and $M$-ary quadrature amplitude modulation ($M$ -QAM). It is found that the end-to-end SNR for relaying with orthogonal channels is higher than that of nonorthogonal relay channels. The diversity order of a multiple-relay network ( $n$ relays) in a Nakagami-$m$ environment is shown to be $(n + 1)m$. The closed-form SER expressions for relay–destination links with high SNRs and static relay–destination links are derived. Numerical and simulation results are provided to verify the analysis.      

Efficient computation of MRC diversity performance in Nakagamifading channel with arbitrary parameters

A very efficient numerical expression is described for MRC diversity performance in a Nakagami fading channel with arbitrary parameters, including all possible conditions of received signal strength and arbitrary fading figures     

A general combinatorial sphere decoder and its application

The conventional problem of searching the shortest vector z of a N-dimensional lattice L(H) with generating matrix HisinR^NtimesM is considered in a more general setting. There are P generating matrices H_iisinR^NtimesM(i=1,2,...,P) of the P lattices L(H_i). For a (bounded) integer vector bisinZ^M , we obtain P lattice points H_ib. Let d_i be the Euclidean norm of H_ib. The problem of interest is how to search for a vector b so that the maximum of d_i is minimized. We propose a new sphere decoder called combinatorial sphere decoder (CSD) to solve this problem. One of the applications of the new CSD is presented in detail to show its effectiveness     

On the trivariate rician distribution

An exact expression for the joint density of three correlated Rician variables is not available in the open literature. In this letter, we derive new infinite series representations for the trivariate Rician probability density function (pdf) and the joint cumulative distribution function (cdf). Our results are limited to the case where the inverse covariance matrix is tridiagonal. This case seems the most general one that is tractable with Miller?s approach and cannot be extended to more than three Rician variables. The outage probability of triple branch selective combining (SC) receiver over correlated Rician channels is presented as an application of the density function.     

Performance of digital linear modulations on Weibull slow-fading channels

A closed-form expression is derived for the moment-generating function of the Weibull distribution, valid when its fading parameter assumes integer values. Expressions for average signal-to-noise ratio, signal outage, and average symbol-error rate are derived for single-channel reception and independent multichannel diversity reception operating on flat Weibull slow-fading channels.     

Bit error rate performance of π/4 DQPSK for Nakagami-lognormalchannels

A convergent infinite series has been presented for the bit error performance of π/4 DQPSK for Nakagami-lognormal channels if the fading figure m is an integer. The authors show that this infinite series can be replaced by a finite series. A convergent series for the BER is also derived when the fading figure, m, is real