Software Defined Radio: Baseband Technologies for 3G Handsets and Basestations

7

Cost Effective Software Radio for CDMA Systems

Alan Gatherer, Sundararajan Sriram, Filip Moerman, Chaitali Sengupta and Kathy Brown

Texas Instruments, Dallas, Texas

7.1. Introduction

7.1.1. The Phases of Baseband Development

The development of baseband radio equipment traditionally passes through three distinct phases. In phase zero, a completely flexible solution is developed using DSPs and FPGAs. This early modem is designed to test out the algorithms in trials. Already at this stage of development the software-to-hardware partition is being developed. Often in the next stage, phase one, the modem is roughly a copy of the phase-zero modem architecture with the FPGA replaced by ASIC and the major bugs removed. Developers do not go to a completely hardwired solution because of potential changes in the standard being implemented, as well as upgrades for better performance, or even channel density, that occur as a greater understanding of the modem's operation is gained from field experience. Also, some operations are already carried out efficiently in the DSP and conversion to an ASIC solution is seen to have little value. The third phase is generally a cost reduction of the second phase and may well involve a change in architecture. A more detailed description of the design cycles for 2G and 3G modems is given in [1].

7.1.2. Software Radio and Technology Intercept

From the software defined radio (SDR) disciple's point of view, the modem in phase zero would already be a software-only ...