IEEE Communications Magazine • July 2003 116 0163-6804/03/$17.00 © 2003 IEEE TOPICS IN SOFTWARE AND DSP IN RADIO INTRODUCTION In this article we describe the essential elements of a flexible, adaptive, and reconfigurable (FAR) radio modem technology framework for indoor environments in order to accommodate various new demands placed on such radios by an assort- ment of agents. Flexibility in the present context refers to the ability to respond to various changes in the requirements or specifications, either pre- sent or future. These can be service or user requirements and their related quality of service (QoS) attributes (data and bit error rates, delays, etc.), environmental conditions (e.g., changes in the channel due to mobility, interference from other users or systems), or system conditions (e.g., operating frequency band). The users, the operator, and the channel are considered here as the three agents that may affect general system operation in a mutually independent manner. Flexibility is thus the toolbox that enables the accommodation of any such circumstances, and therefore comprises a set of techniques in the service of the desirable systemic properties of effectiveness (e.g., spectral efficiency), reliability, robustness, scalability, component reusability, spatial coverage, power and cost efficiency, adjustment to channel conditions, and so on. As new software (SW) and digital signal processing (DSP) tools are continuously developed and improved, their impact on the design philosophy of such radios must be assessed and their power incorporated. To do so effectively, to create designs that harness this power, and to concep- tually harmonize the miscellaneous approaches working in parallel to this end, have provided the key motivation for the presently described Wireless Indoor Flexible High Bitrate Modem Architecture (WIND-FLEX, WF for short) pro- ject [1], partially funded by the European Union’s Information Society Technologies (IST) program, and the collective efforts therein. Regarding short-range wireless technologies [2], to which this project broadly belongs, many important issues remain still unresolved: securi- ty, QoS provision, seamless roaming support, and easy network management, to list a few. Furthermore, present-day wireless local area networks (WLANs) are not really suited for wireless backbone applications since the bit rate is still too low, and do not yet implement some of the more advanced features currently under Andreas Polydoros, University of Athens; Jukka Rautio, VTT Technical Research Centre of Finland; Giuseppe Razzano, University of Rome “La Sapienza”; Hanna Bogucka, Poznan University of Technology; Diego Ragazzi, CEFRIEL — Politecnico di Milano; Panos I. Dallas, INTRACOM S.A.; Aarne Mämmelä, VTT Technical Research Centre of Finland; Michael Benedix, Dresden University of Technology; Manuel Lobeira, ACORDE-University of Cantabria; Luigi Agarossi, Philips Research ABSTRACT We describe the essential features of a novel testbed, code-named WIND-FLEX and devel- oped under the auspices of the EU IST research program, whose primary goal has been to define and explore concepts related to radio flexibility, with application to an OFDM-based short-range indoor radio transceiver design. The emphasis has been on the profitable use of software and DSP tools for the purpose of demonstrating adaptivity and reconfigurability features, primar- ily for the lower layers (i.e., PHY and DLC/MAC layers). The topics covered briefly herein include the meaning of the terms in the present context, their instantiation in the design, their contribu- tion to an optimized low-transmit-power scheme, the novel elements required in order to achieve it, the contribution to a guaranteed QoS philoso- phy, and the relationship of the testbed to broad- er software-defined-radio concepts. WIND-FLEX: Developing a Novel Testbed for Exploring Flexible Radio Concepts in an Indoor Environment