Guest Editorial

Abstract

Originally, when the guest editorial board was contacted by Associate Editor-in-Chief Dr. Haohong Wang of Journal of Communications, we planned to call for the papers contributed to “Blind Signal Processing for Communications”. After collecting the submitted papers, the guest editorial board adjusted the originally focused theme to “Efficient and Robust Signal Processing Schemes for Wireless Receivers” because very few submitted papers were actually dedicated to the former topic while there were quite a few excellent papers addressing the latter thrust area. Perhaps, it seems slightly quixotic to change the course after we saddle up and run a distance. However, for the benefit of the readership, the guest editorial board tried to collect the quality papers to present in this special issue, which turned out to be in a different theme from what we foresaw.

The five papers collected in this special issue are “Radio Resource Allocation for Heterogeneous Services in Relay Enhanced OFDMA Systems”, “A Low-Complexity Optimum Multiuser Receiver for DS-CDMA Wireless Systems”, “Research on Adaptive Waveform Selection Algorithm in Cognitive Radar”, “Grid-based Mobile Target Tracking Mechanism in Wireless Sensor Networks”, and “Analysis of Performance Degradation using Convex Optimization for a Mismatched Receiver”. They address the crucial problems and provide the corresponding innovative approaches and analyses for many kinds of wireless systems such as wireless local-area networks, wireless metropolitan-area networks, radars, sensor networks, etc. The important problems involving resource allocation, waveform adaptation, optimization and searching algorithms are tackled therein.

In general, wireless receivers often endure the difficulties caused by the interference, hardware/software complexities, time-varying or dynamic environments, etc. The popular and key approach is to use the advanced signal processing schemes or subsystems as the solution. In this special issue, the authors with outstanding expertise in code-division multiple-access (CDMA), orthogonal frequency-division multiplexing (OFDM), radar, sensor network systems and communication theories share their state-of-the-art knowledge and innovative methods in these areas.

The highlights of this special issue are given as follows. A priority based resource allocation algorithm for heterogeneous services in the relay enhanced OFDMA downlink systems is proposed to maximize the system throughput while satisfying the quality-of-service (QoS) requirements. A novel approach for reducing the asymptotic computational complexity of multiuser receivers is proposed and it utilizes the transformation matrix (TM) technique to improve the performance of multiuser detectors. By using this proposed algorithm, the computational complexity of multiuser detectors can be reduced by several orders of magnitude. The problem of adaptive waveform selection in cognitive radar is modeled by stochastic dynamic programming and then backward dynamic programming, temporal difference learning and Q-learning are employed to solve this problem. A new grid-based mobile target tracking (GMTT) mechanism is designed for sensor networks to prolong the network lifetime. Finally, the robustness of a complex communication system mismatch problem is studied. A potential application of this study is that the concept of requiring additional margin in the signal-to-noise (SNR) operating point of the system can be formulated in order to maintain the original desired system performance in the presence of this mismatched receiver design.

The expected impacts of this special issue can be found in the significant areas ranging from CDMA, OFDM, radar, sensor networks, to general receiver design in the future. Although this special issue covers a good spectrum of diversified topics, there still remain much more open questions than we try and are able to answer. Hopefully, we may dedicate this issue to a notable mileage in the long scientific journey on communications research. Compagnon de voyage, enjoy this marvelous ride!