A software radio testbed for UMTS TDD systems

Today's and near future mobile communication systems need to provide universal seamless connection to the users between different standards and types of service. This requires a significant degree of flexibility that can be provided by Software Defined Radio (SDR) terminals. Eurécom and EPFL have started a joint project whose objective is to study and implement a real-time SDR communication platform to validate advanced algorithms for wireless communications. The platform is a real-time PC based system that can handle wide-band radio resources. It provides hardware, DSP software, and link-level software functionalities. Due to various practical design issues, the platform implements the essential physical layer features of the time-division duplex (TDD) mode of the UMTS standard proposal (air-interface and signal processing), although frequency-division duplex (FDD) mode and even other standards could also be im-plemented. In this paper we address the major general issues inherent to the design of a real-time SDR system. Then we focus on our SDR platform by describing the general architecture, the signal processing techniques adopted to implement the transmitter and receiver SDR front-end, the current set-up, and DSP performance measurements. Finally, we address the future perspectives for the platform evolution.