A low-power DSP for wireless communications

This paper proposes a low-power high-throughput digital signal processor (DSP) for baseband processing in wireless terminals. It builds on our earlier architecture-Signal processing On Demand Architecture (SODA)-which is a four-processor, 32-lane SIMD machine that was optimized for WCDMA 2 Mbps and IEEE 802.11a. SODA has several shortcomings including large register file power, wasted cycles for data alignment, etc., and cannot satisfy the higher throughput and lower power requirements of emerging standards. We propose SODA-II, which addresses these problems by deploying the following schemes: operation chaining, pipelined execution of SIMD units, staggered memory access, and multicycling of computation units. Operation chaining involves chaining the primitive instructions, thereby eliminating unnecessary register file accesses and saving power. Pipelined execution of the vector instructions through the SIMD units improves the system throughput. Staggered execution of computation units helps simplify the data alignment networks. It is implemented in conjunction with multicycling so that the computation units are busy most of the time. The proposed architecture is evaluated with an in-house architecture emulator which uses component-level area and power models built with Synopsys and Artisan tools. Our results show that for WCDMA 2 Mbps, the proposed architecture uses two processors and consumes only 120 mW while SODA uses four processors and consumes 210 mW when implemented in 0.13-μm technology and clocked at 300 MHz.