Use of Time-Frequency Analysis and Neural Networks for Mode Identification in a Wireless Software-Defined Radio Approach
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Use of Time-Frequency Analysis and Neural Networks for Mode Identification in a Wireless Software-Defined Radio Approach Matteo Gandetto Signal Processing and Telecommunication Group (SP&T), Biophysical and Electronic Engineering Department, University of Genoa, 16145 Genoa, Italy Email: [email protected]
Marco Guainazzo Signal Processing and Telecommunication Group (SP&T), Biophysical and Electronic Engineering Department, University of Genoa, 16145 Genoa, Italy Email: [email protected]
Carlo S. Regazzoni Signal Processing and Telecommunication Group (SP&T), Biophysical and Electronic Engineering Department, University of Genoa, 16145 Genoa, Italy Email: [email protected] Received 4 September 2003; Revised 8 June 2004 The use of time-frequency distributions is proposed as a nonlinear signal processing technique that is combined with a pattern recognition approach to identify superimposed transmission modes in a reconfigurable wireless terminal based on softwaredefined radio techniques. In particular, a software-defined radio receiver is described aiming at the identification of two coexistent communication modes: frequency hopping code division multiple access and direct sequence code division multiple access. As a case study, two standards, based on the previous modes and operating in the same band (industrial, scientific, and medical), are considered: IEEE WLAN 802.11b (direct sequence) and Bluetooth (frequency hopping). Neural classifiers are used to obtain identification results. A comparison between two diļ¬erent neural classifiers is made in terms of relative error frequency. Keywords and phrases: mode identification, software-defined radio, frequency hopping code division multiple access, direct sequence code division multiple access, time-frequency analysis, pattern recognition.
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INTRODUCTION
The ideal software radio (SR) [1] can accommodate all existing bands and modes in a host terminal or, more generally, in a platform. Toward this end, SR defines all radio frequency (RF) aspects (filtering, access methods, etc.) and transmission/reception layer functions (modulation, coding, etc.) in software terms to support multimode, multiband communications. In general, SR can be applied to base stations (BSs) [2] or to user terminals (UTs). SR-based transceivers are characterized by high levels of adaptability, flexibility, and reconfiguration. The ideal SR leads to a revolution in the design of a transmitter/receiver terminal (if used in a BS or UT) with respect to the conventional radio devices based on the classical heterodyne schemes [3]. The analogical part of an SR-based
device is very reduced (only the antenna, the low noise amplifier (LNA)), and it should be designed to receive all existing available modes and not a particular one [4]. The D/A and A/D conversion processes move closer to the antenna. In the case of reception, the signals associated with all communication modes present in the radio environment are first sampled (by A/D) at high frequency and then represented in a digital fo
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