Flexible Multi-Standard Terminals for 2nd and 3rd Generation Mobile Systems

The principle of software radio architecture is investigated and applied for the implementation of a multi-standard terminal (MST) for operation with both current 2nd and future 3rd generation mobile radio systems. A key strategy for the design of the transceiver is to place the analog-to-digital converter (ADC) and digital-to-analog converter (DAC) as close as possible to the antenna. In addition to reducing the analog front-end, this would allow more transceiver operations to be performed by programmable digital signal processing devices. Flexible DSP techniques are also ideally suited for the implementation of modem functions like channel estimation, synchronisation, equalization, interleaving, source and channel coding for a variety of different transmission technologies and multiple access schemes. This also enables the concept of over-the-air software download for the reconfiguration of the MST. The radio receiver frontend is realized with two intermediate frequencies (IF). The design must satisfy requirements like sensitivity, dynamic range, selectivity and resistance against interfering and blocking signals. Digital down-conversion is performed by sub-sampling at low IF, followed by multirate techniques for decimation and digital filtering. Several trade-offs between the analog front-end and the digital demodulation must be balanced carefully with respect to the available technology, e.g. more digital processing power can relax the requirements for analog filtering. This work has been performed in the context of the FIRST project (Flexible Integrated Radio System Technology) as part of the ACTS mobile line.