Pilot Symbol-aided Modulation Research Articles

MIMO Two-Way Amplify-and-Forward Relaying With Imperfect Receiver CSI

In this paper, we investigate the effects of channel estimation error on the receiver of multiple-input-multiple-output (MIMO) amplify-and-forward (AF) two-way relaying. The estimation is conducted via training using known pilot symbols transmitted from the terminals, which is a method commonly referred to as pilot symbol-aided modulation. In this context, linear minimum mean square estimation (LMMSE) of composite and individual channels is analyzed. We show that orthogonal pilots, i.e., pilot sequences that are orthogonal over the antenna arrays and the communicating terminals, minimize the composite and individual mean square errors. Using notions of worst-case noise, we obtain lower bounds on the sum rate of information transmission in both directions of the bidirectional relay link and show that the orthogonal pilots perform well against the bound.

Iterative Channel Estimators in V-BLAST OFDM Systems

An iterative pilot-symbol aided modulation (PSAM) channel estimation approach is proposed for vertical Bell Laboratories layered space-time (V-BLAST) orthogonal frequency division multiplexing systems operating on frequency-selective fading channels. Since the signals at the receive antennas are the superposition of signals from multiple transmit antennas, accurate channel estimates are crucial for good error performance. Furthermore, the time selectivity of the fading channels leads to inter-carrier interference (ICI). While ICI can be ignored for slow fading channels, it should be mitigated for fast fading channels. This paper proposes an ICI mitigation scheme for time-varying channels. We also propose an iterative channel estimator with low-complexity. Simulation results demonstrate the usefulness of the proposed algorithm on frequency-selective fading channels.

Maximal-ratio eigen-combining: a performance analysis

Maximal-ratio eigen-combining (MREC) for wireless communications channels, also known as eigen-beamforming for receivers equipped with antenna arrays, integrates conventional maximum average signal-to-noise-ratio beamforming (Max-ASNR BF) and maximal-ratio combining (MRC) to provide both high average SNR in high fading correlation as well as diversity in low fading correlation. Previous studies of MREC were based on simulation or limited analysis and suggested that MREC can outperform Max-ASNR BF and MRC in terms of average error probability (AEP). A comprehensive analysis of MREC is provided for BPSK signals and Rayleigh fading, including computable AEP and outage probability (OP) expressions for perfectly known, correlated channel gains. Particular cases of these expressions apply to Max-ASNR BF and MRC. For imperfectly known channels the analysis yields a new and general AEP expression for MREC, which is specialized to estimation based on pilot-symbol-aidedmodulation (PSAM) and interpolation. In particular, this AEP expression applies to Max-ASNR BF and, for PSAM and data-independent interpolation filters, to MRC. Numerical results for antenna arrays receiving signals with angle-of-arrival dispersion and imperfectly known channel gains confirm the potential advantage of MREC over Max-ASNR BF and MRC.

Impact of imperfect pilot-symbol-aided channel estimation on TCM performance over Rayleigh fading channels

In this paper, we present a simple method of approximating BER performance of a mobile communication system using trellis-coded modulation and realistic and thus imperfect channel estimation. We consider the case of pilot-symbol-aided modulation (PSAM) by interpolation on flat Rayleigh fading channels. Different methods of PSAM are considered and compared on the realistic Bessel channel model as well as on a simplified Butterworth model. An error floor at high SNR is identified as the most important degradation from the case of ideal channel estimation. Error floor values, necessary for system dimensioning, can easily be approximated using a modified approach to exact pairwise error probability (PEP) calculation.

Symbol error rate analysis for MPSK under Rician fading channels with fading compensation based on time correlation

In order to combat the effects of channel fading, a pilot symbol-aided modulation based on fading time correlation has been proposed. In this paper we present results of analytical studies on this technique which were not included in previous works. We derive a new formula to determine the symbol error rate of MPSK scheme under Rician fading channels. The results are compared with a perfect carrier-referenced system. Computer simulations are also carried out to verify the analytical results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>