Using FPGAs for Software-Defined Radio Systems: a PHY layer for an 802.15.4 transceiver. Eloi Ramon Dept. d’Enginyeria Electrònica Universitat Autònoma de Barcelona ETS d’Enginyeria 08193 Bellaterra Eloi.Ramon@uab.es Jordi Carrabina Dept. de Microelectrònica i Sistemes Electrònics Universitat Autònoma de Barcelona ETS d’Enginyeria 08193 Bellaterra Jordi.Carrabina@uab.es Abstract During the last decade, designers have used ASICs and DSPs to handle nearly all of the signal- processing functions associated with radio communications. Latest generation of FPGAs are so powerful that they're now displacing both ASICs and DSPs in software-radio applications. Software radio is an emerging technology, aimed to build flexible radio systems, which are multiple-service, multi-standard, multi-band, reconfigurable and re-programmable, by software. In this paper we present the state-of-the-art in Software-Defined Radio Systems and a PHY layer for an 802.15.4 transceiver. 1. Introduction 1.1. Software-Defined Radio Systems (SDR) Software Radio can be described as radio functionalities defined by software [1]. Currently the radio interface in wireless systems is usually implemented by dedicated hardware. The presence of software defining the radio interface implies the use of DSPs replacing dedicated hardware to execute, in real time, the radio functionalities by software [2]. The most common definitions of SDR systems are [3]: • Flexible transceiver architecture, controlled and programmable by software • Signal processing able to replace, as much as possible, radio functionalities • air-interface-download ability: dynamically re-configurable radio equipment by downloadable software, at every level of the protocol stack • Software realization of terminals multi-mode/ multi-standard • Transceiver where frequency band & radio channel bandwidth, modulation & coding scheme and radio resource and mobility management protocols can be defined by software. • System where parameters can be adapted and changed by network operator, service provider or final user. A wireless receiver developed as a software- defined radio system consists of just a few components: an analog RF front-end, an analog- to-digital converter (ADC) and a demodulator + decoder. The RF front-end is easy to use from a wide number of companies providing analog integrated down-converters in some of the most used ranges of frequencies (from ISM to DVB terrestrial or satellite). Due to high frequencies used in most of the commonly used frequency ranges, RF front- end can’t be digital. A lot of experiences have been reported in lower frequencies (commercial AM and FM, et cetera) due that these frequencies are still in the working range of commercial analog-to-digital converters (ADC). In the cases of higher frequencies, an analog down-converter is required to translate frequencies (hundreds of MHz to some GHz) to an intermediate frequency (IF) or baseband (BB). At lower frequencies the used bandwidth of channel can be processed in a standard ADC.