The Application of Programmable DSPs in Mobile Communications

2

The History of DSP Based Architectures in Second Generation Cellular Handsets

Alan Gatherer, Trudy Stetzler and Edgar Auslander

2.1 Introduction

Programmable Digital Signal Processors (DSPs) are pervasive in the second generation (2G) wireless handset market for digital cellular telephony. This did not come about because everyone agreed up front to use DSPs in handset architectures. Rather, it was a result of a battle between competing designs in the market place. Indeed, the full extent of the use of programmable DSPs today was probably not appreciated, even by those who were proposing DSP use, when the 2G market began to take off.

In this chapter we present the argument from a pro-DSP perspective by looking at the history of DSP use in digital telephony, examining the DSP based solution options for today's standards and looking at future trends in low power DSPs. We show that some very compelling arguments in favor of the unsuitability of DSPs for 2G digital telephony turned out to be spectacularly wrong and that, if history is to teach us anything, it is that DSP use increases as a wireless communications standard matures. As power is the greatest potential roadblock to increased DSP use, we summarize trends in power consumption and MIPS.

Of course, history is useless unless it tells us something about our future. Moreover, as the DSP debate starts to rage for third generation (3G) mobile communication devices we would like to postulate that the lessons of 2G will apply to ...