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

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

Visualization on colour based flow vector of thermal image for movement detection during interactive session

Recently thermal imaging is exploited in applications such as motion and face detection. It has drawn attention many researchers to build such technology to improve lifestyle. This work proposed a technique to detect and identify a motion in sequence images for the application in security monitoring system or outdoor surveillance. Conventional system might cause false information with the present of shadow. Thus, methods employed in this work are Canny edge detector method, Lucas Kanade and Horn Shunck algorithms, to overcome the major problem when using thresholding method, which is only intensity or pixel magnitude is considered instead of relationships between the pixels. The results obtained could be observed in flow vector parameter and the segmentation colour based image for the time frame from 1 to 10 seconds. The visualization of both the parameters clarified the movement and changes of pixel intensity between two frames by the supportive colour segmentation, either in smooth or rough motion. Thus, this technique may contribute to others application such as biometrics, military system, and surveillance machine

Efficient space-frequency block coded pilot-aided channel estimation method for multiple-input-multiple-output orthogonal frequency division multiplexing systems over mobile frequency-selective fading channels

© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.An iterative pilot-aided channel estimation technique for space-frequency block coded (SFBC) multiple-input multiple-output orthogonal frequency division multiplexing systems is proposed. Traditionally, when channel estimation techniques are utilised, the SFBC information signals are decoded one block at a time. In the proposed algorithm, multiple blocks of SFBC information signals are decoded simultaneously. The proposed channel estimation method can thus significantly reduce the amount of time required to decode information signals compared to similar channel estimation methods proposed in the literature. The proposed method is based on the maximum likelihood approach that offers linearity and simplicity of implementation. An expression for the pairwise error probability (PEP) is derived based on the estimated channel. The derived PEP is then used to determine the optimal power allocation for the pilot sequence. The performance of the proposed algorithm is demonstrated in high frequency selective channels, for different number of pilot symbols, using different modulation schemes. The algorithm is also tested under different levels of Doppler shift and for different number of transmit and receive antennas. The results show that the proposed scheme minimises the error margin between slow and high speed receivers compared to similar channel estimation methods in the literature.Peer reviewe

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

Near-Instantaneously Adaptive HSDPA-Style OFDM Versus MC-CDMA Transceivers for WIFI, WIMAX, and Next-Generation Cellular Systems

Burts-by-burst (BbB) adaptive high-speed downlink packet access (HSDPA) style multicarrier systems are reviewed, identifying their most critical design aspects. These systems exhibit numerous attractive features, rendering them eminently eligible for employment in next-generation wireless systems. It is argued that BbB-adaptive or symbol-by-symbol adaptive orthogonal frequency division multiplex (OFDM) modems counteract the near instantaneous channel quality variations and hence attain an increased throughput or robustness in comparison to their fixed-mode counterparts. Although they act quite differently, various diversity techniques, such as Rake receivers and space-time block coding (STBC) are also capable of mitigating the channel quality variations in their effort to reduce the bit error ratio (BER), provided that the individual antenna elements experience independent fading. By contrast, in the presence of correlated fading imposed by shadowing or time-variant multiuser interference, the benefits of space-time coding erode and it is unrealistic to expect that a fixed-mode space-time coded system remains capable of maintaining a near-constant BER