0000000000001626
AUTHOR
Yi Wu
Reducing the peak and average power for OFDM systems using QAM by constellation shaping
In this paper, we present a shell mapping scheme to reduce the peak and average power of orthogonal frequency division multiplexing (OFDM) signals using quadrature amplitude modulation (QAM) by constellation shaping. Our approach can be considered as an extension of the shell mapping technique introduced originally in the V.34 recommendation of ITU-T. The shell mapping method uses multiple cost functions, each having the OFDM block length N as a parameter. The cost functions are presented in closed form for any N. The main advantage of the proposed scheme is that the peak and average power can be reduced without sacrificing the data rate, and no side information is needed at the receive sid…
Unitary Space–Time Constellation Design Based on the Chernoff Bound of the Pairwise Error Probability
Unitary space-time constellation design is considered for noncoherent multiple-antenna communications, where neither the transmitter nor the receiver knows the fading coefficients of the channel. By employing the Clarke's subdifferential theorem of the sum of the kappa largest singular values of a unitary matrix, we present a numerical optimization procedure for finding unitary space-time signal constellations of any dimension. The Chernoff bound of the pairwise error probability is used directly as a design criterion. The constellations are found by performing gradient descent search on a family ldquosurrogaterdquo functions that converge to the maximum pairwise error probability. The comp…
Parameter optimization for amplify-and-forward relaying with imperfect channel estimation
Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with an imperfectly-known relay fading channel. It is assumed that a pilot symbol assisted modulation (PSAM) scheme with linear minimum mean square estimator (LMMSE) is used for the channel estimation. A simple and easy-to-evaluate asymptotical upper bound (AUB) of the symbol-error-rate (SER) is derived for uncoded AF cooperative systems with quadrature amplitude modulation (QAM) constellations. Based on the AUB, we propose a criterion for the choice of parameters in the PSAM scheme, i.e., the pilot spacing …
Performance analysis of amplify-and-forward cooperative communication systems with channel estimation errors
Cooperative diversity is a transmission technique that achieves a diversity gain by using a combination of the relayed signal and the direct signal. In this paper, we study the symbol-error-rate (SER) performance of a cooperative communication system operating in an amplify-and-forward (AF) mode, where the channel state information (CSI) available at the receiver is an estimate of the channel gains with estimation errors. We derive both the probability density function and the moment generating function of the instantaneous signal-to-noise ratio (SNR) at the destination terminal. These statistical quantities are then applied to study the performance of an AF cooperative communication system…
Parameter optimization for amplify-and-forward relaying systems with pilot symbol assisted modulation scheme
Article published in the journal:Wireless Sensor Network Also available from publisher: http://dx.doi.org/10.4236/wsn.2009.11003 Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol assisted modulation (PSAM) scheme. It is assumed that a linear minimum mean square estimator (LMMSE) is used for the channel estimation at the receiver. A simple and easy-to-evaluate asymptotical upper bound (AUB) of the symbol-error-rate (SER) is derived for uncoded AF cooperative communication systems with quadrature amplitude modulation (QAM) constellations. …
A 16QAM super-orthogonal space-frequency code for broadband mobile communication systems with two transmit antennas
We combine our previously designed 32-state super-orthogonal space-time trellis code (SOSTTC) with orthogonal frequency division multiplexing (OFDM) to build a broadband mobile communication system having a spectral efficiency that amounts to 4 bits/s/Hz depending on the length of the cyclic prefix used to avoid interframe interference. The transmitter is equipped with two antennas, where the OFDM frames they transmit are not independent, as they carry the same information in an orthogonal form. The 2N OFDM tones are grouped in N pairs of tones. Each group of two tones transmits the entries of a 2×2 orthogonal matrix. In our case, the entries are symbols taken from the rectangular 16-point …
Performance Analysis of Cooperative Communication Systems with Imperfect Channel Estimation
This paper investigates the effects of channel estimation errors on the symbol-error-rate (SER) performance of a cooperative communication system operating in an amplify-and- forward (AF) mode. A pilot symbol assisted modulation scheme with linear minimum mean square estimation (LMMSE) is used for the channel estimation. An accurate and easy-to-evaluate SER expression is presented for uncoded cooperative communication systems with quadrature amplitude modulation (QAM) and phase-shift keying (PSK) constellations. Numerical simulations are conducted to verify the correctness of the proposed analytical formulation. It is shown that the performance loss caused by channel estimation errors incre…