Special Issue on Signal Processing for Software Defined Radio Handsets

Abstract

The ultimate objective of Software Defined Radio (SDR) is to replace the entire analog signal processing in the wireless transceivers with digital signal processing. This will provide the flexibility, through reconfiguration or reprogramming, to enable the transceivers to work with different air-interfaces standards using a single generic hardware platform. Most of the research in SDR to date has been focused on base stations, which do not have as tight constraints in size and power consumption as handsets. However, in order to realize the promise of integrated services and global roaming capabilities, the design and development of a multi-standard SDR handset with dynamic reconfigurability is crucial. The size and power constraints imposed by handsets with limited resources pose a major design challenge. This special issue brings together 11 papers that address various aspects of this challenge from the perspectives of wireless systems, computing architectures, embedded systems and signal processing. The most important part of an SDR transceiver is the wideband analog-to-digital converter (ADC) that converts the radio frequency signal received by the antenna into digital form for further processing. The first paper, “A multi-mode sigma-delta ADC for GSM/WCDMA/WLAN applications” by Jose et. al. proposed a cascaded reconfigurable sigma-delta modulator that is able to work with three different communication standards. This design, implemented in 0.18 μm CMOS technology, exhibits excellent signal-to-noise plus distortion ratios and has reduced power consumption compared to conventional designs. After ADC, the digitized received signal will need to be separated into signals within the various bands specified by the communication standard. This is performed by the channelizer which has the highest computational requirements of the whole SDR system. The second paper, by Panicker et al., reviews the state-of-the-art filter bank channelizer techniques with low power and dynamic reconfigurability properties. The design of reconfigurable devices can be optimized using the methodology of parametrization which bring together the common aspects of a myriad number of wireless standards into a single processing procedure. In this way, the implementation of the multi-standard SDR will be greatly simplified. “Promising technique of parametrisation for reconfigurable radio, the Common Operators Technique: fundamentals and examples” by Alaus et al. presents the common operator technique for parametrization which is less standards dependent than the more conventional Common Function technique. The direct digitization of the radio frequency (RF) signal requires very high speed ADCs which is not readily available using current technology. Therefore, current SDR implementations typically down-converts the RF A. P. Vinod (*) School of Computer Engineering, Nanyang Technological University, Nanyang, Singapore e-mail: asvinod@ntu.edu.sg