Pilot-Symbol-Aided 16PSK and 16QAM for Digital Land Mobile Radio Systems

The paper proposes a novel pilot-symbol-aided (PSA) technique for fading compensation of digital signals in the mobile environments. In a PSA system, the data sequence at the transmitter is divided into frames of data. A pilot symbol from a known pseudoradom-symbol sequence is inserted periodically into a frame of data symbol for transmission. In a conventional PSA-receiver, these pilot symbols are extracted from the received signal and used to estimate the effects of signal distortion introduced in the fading channel. The resultant estimates are then used to correct the distortion effects in the received data frames. In the paper, a novel estimation technique that uses the data symbols as well as the pilot symbols is proposed. The technique has the major advantages of simple implementation and short storage-delay time. Results are presented in a series of computer-simulation tests. These assess the effectiveness of the estimation technique on the BER performances of a 16-ary phase-shift keyed (16PSK) and a 16-ary quadrature-amplitude modulated (16QAM) signals in the frequency-selective and frequency-nonselective Rayleigh fading channels. The channels are corrupted by co-channel interference or additive white Gaussian noise. Results of differential-detected 16PSK and star-16QAM signals are also presented for comparison. It has been shown that, the use of PSA technique can significantly improve the bit-error-rate performances of the systems, relative to those using differential detection.postprin

A Faded-Compensation Technique for Digital Land Mobile Satellite Systems

This paper proposes a novel fade-compensation algorithm using a pilot symbol-aided technique for digital and mobile satellite systems. In a conventional pilot symbol-aided system, a pilot symbol from a known pseudorandom-symbol sequence is inserted periodically into the data-symbol sequence in the transmitter. At the receiver, these pilot symbols are extracted from the received signal and used to estimate the signal distortion introduced in the fading channel. The resultant estimate is then used to correct the fading effects in the received data symbols. In this paper, a novel fade-compensation technique that uses both the pilot symbols and the data symbols is proposed. A series of computer-simulation tests has been carried out to assess the effectiveness of the technique on the bit-error-rate (BER) performances of an uncoded 16-ary phase-shift keyed (16PSK) and an uncoded 16-ary quadrature-amplitude modulated (16QAM) signal over the land mobile satellite channels. The results have shown that substantial improvements in the BER performances of the systems can be obtained, compared to those using only the pilot symbolspostprin

Performance of a pilot symbol-aided technique in frequency-selective Rayleigh fading channels corrupted by co-channel interference and Gaussian noise

The paper studies the effects of a pilot symbol-aided (PSA) technique on the performances of 16QAM and 16PSK in the frequency-selective Rayleigh fading channels corrupted by co-channel interference and Gaussian noise. The PSA technique employs both the pilot symbols and data symbols for fading estimation. Computer simulation results have shown that significant improvements on bit-error rate performances of the signals can be achieved through the use of the PSA technique.published_or_final_versio

Bandwidth-efficient pilot-symbol-aided technique for multipath-fading channels

Pilot-symbol-aided (PSA) transmission is one of the effective methods to combat multipath fading in digital mobile communications systems. In the PSA systems, redundant bandwidth and power are required to transmit the pilot symbols. In this paper, we propose a novel fading estimation technique that requires a very low bandwidth redundancy in the PSA systems. The proposed technique uses simple linear interpolation on the pilot symbols and the detected data symbols to obtain the estimates of the channel fading effects. Monte Carlo computer simulation has been carried out to study the effects of the technique on the bit error rate performance of 16-ary quadrature amplitude modulation in the flat and the frequency-selective Rayleigh-fading channels corrupted with cochannel interference and additive white Gaussian noise. Results have shown that the proposed technique can, at the expense of a little power efficiency, significantly improve the bandwidth efficiency of the PSA systems using receivers with low com plexity and latency.published_or_final_versio

Performances of 16QAM with fading compensation and postdetection diversity reception in satellite mobile channels

This paper studies the effects of N-branch postdetection selection diversity reception, where N = 1, 2, 3 or 4, incorporated with fading compensation on a digital satellite mobile system. The digital satellite mobile system transmits a pilot-symbol-aided 16-ary quadrature-amplitude modulated (PSA-16QAM) signal over the Rician channels. A selection method that makes use of the pilot symbols to select one of the N branches in the diversity reception system for signal detection, and a novel PSA technique that makes use of both the pilot symbols and data symbols for fading compensation, are proposed. Computer simulation tests are used to assess the effects of the proposed techniques on bit-error rate performances (BER) of the PSA-16QAM system in the presence of additive white Gaussian noise (AWGN) or co-channel interference (CCI) in the Rician faded channels. When frequency diversity is used, PSA-16QAM with 2-branch and 4-branch diversity reception occupies about the same bandwidths as quaternary phase-shift-keying (QPSK) without using diversity and with 2-branch diversity, respectively, yet achieving the same capacity. Thus, simulation tests on the BER performances of a QPSK system without diversity and with 2-branch diversity are also carried out and the results are used to determine the preferred system arrangements. ©1997 John Wiley & Sons, Ltd.postprin

Adaptive multiple symbol decision feedback for non-coherent detection.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2006.Non-coherent detection is a simple form of signal detection and demodulation for digital communications. The main drawback of this detection method is the performance penalty incurred, since the channel state information is not known at the receiver. Multiple symbol detection (MSD) is a technique employed to close the gap between coherent and non-coherent detection schemes. Differentially encoded JW-ary phase shift keying (DM-PSK) is the classic modulation technique that is favourable for non-coherent detection. The main drawback for standard differential detection (SDD) has been the error floor incurred for frequency flat fading channels. Recently a decision feedback differential detection (DFDD) scheme, which uses the concept of MSD was proposed and offered significant performance gain over the SDD in the mobile flat fading channel, almost eliminating the error floor. This dissertation investigates multiple symbol decision feedback detection schemes, and proposes alternate adaptive strategies for non-coherent detection. An adaptive algorithm utilizing the numerically stable QR decomposition that does not require training symbols is proposed, named QR-DFDD. The QR-DFDD is modified to use a simpler QR decomposition method which incorporates sliding windows: QRSW-DFDD. This structure offers good tracking performance in flat fading conditions, while achieving near optimal DFDD performance. A bit interleaved coded decision feedback differential demodulation (DFDM) scheme, which takes advantage of the decision feedback concept and iterative decoding, was introduced by Lampe in 2001. This low complexity iterative demodulator relied on accurate channel statistics for optimal performance. In this dissertation an alternate adaptive DFDM is introduced using the recursive least squares (RLS) algorithm. The alternate iterative decoding procedure makes use of the convergence properties of the RLS algorithm that is more stable and achieves superior performance compared to the DFDM

Combining PSA fading estimation techniques for TCM and diversity reception in Rician fading channels

In this paper, a novel pilot-symbol-aided (PSA) technique is proposed for fading estimation in the land mobile satellite fading channels. The proposed technique combines the fading estimates obtained from a bandwidth-efficient technique and a conventional technique according to the signal-to-noise ratios (SNRs) of the fading estimates. To enhance the transmission quality, trellis-coded modulation (TCM) and diversity reception are employed in the system, and the combined estimates are subsequently used to correct the channel fading effects, to weight the signals from different diversity branches, and to provide channel state information of the Viterbi decoder. Monte Carlo computer simulation has been used to study the bit-error-rate (BER) performance of the proposed technique on trellis-coded 16-ary quadrature amplitude modulation in the frequency non-selective Rician fading channels. Results have shown that the proposed PSA technique requires a very low bandwidth redundancy to provide satisfactory BER performance at low SNRs, and thus is suitable for use with TCM and diversity reception to achieve both bandwidth and power-efficient transmission.postprin

Performance of a Faded-Compensated 16QAM with Diversity Reception in Mobile radio Channels

The paper studies the bit-error-rate (BER) performance of a fade-compensated 16 QAM with two-branch postdetection selection combining diversity reception in the Rayleigh fading channels. A pilot symbol-aided (PSA) technique that uses both pilot symbols and data symbols is employed for fading compensation. Computer simulation results have shown that, the use of diversity reception technique can significantly improve the BER performance when the normalized delay between the signals at the two receivers is small. It is also shown that, the error-floor is sensitive to the normalized delay, but relatively less sensitive to the power ratio between the signals at the two receivers.published_or_final_versio

Combining pilot-symbol-aided techniques for fading estimation and diversity reception in multipath fading channels

A novel pilot-symbol-aided (PSA) fading estimation technique that combines the estimates from a conventional PSA technique and a bandwidth-efficient PSA technique to achieve better performances is proposed for digital signals in multipath fading channels. The conventional technique has better performances at low signal-to-noise ratios (SNRs), while the bandwidth-efficient technique is superior at high SNRs. Monte Carlo computer simulation has been used to assess the effects of the proposed combining technique on the bit-error-rate (BER) performances of 16-ary quadrature-amplitude-modulation (16QAM), with and without two-branch diversity reception, in a flat Rayleigh fading channel. Results have shown that the combining technique has the advantages of both of the conventional technique and the bandwidth-efficient technique and is more preferred for use with diversity reception. © 2006 Springer Science + Business Media, Inc.postprin