3G Handset and Network Design

CHAPTER 2

GPRS/EDGE Handset Hardware

In this chapter we examine the hardware requirements for a GPRS tri-band phone capable of supporting higher-level modulation techniques. We address the design issues introduced by the need to produce the following:

A multislot handset. Capable of supporting GSM (8 slots) and US TDMA (3/6 slots)

A multiband handset. 800, 900, 1800, 1900 MHz

A multimode handset. Capable of processing constant envelope GMSK modulation (GSM) and higher-level modulation with AM components (US TDMA)

We need to combine these design requirements with an overall need to minimize component count and component cost. We also must avoid compromising RF performance.

Design Issues for a Multislot Phone

The idea of a multislot phone is that we can give a user more than one channel. For instance, one slot could be supporting a voice channel, other slots could be supporting separate but simultaneous data channels, and we can give a user a variable-rate channel. This means one 9.6 kbps channel (one slot) could be expanded to eight 9.6 kbps channels (76.8 kbps), or if less coding overhead was applied, one 14.4 kbps channel could be expanded to eight 14.4 kbps channels (115 kbps). Either option is generically described as bandwidth on demand.

In practice, the GSM interface was designed to work with a 1/8 duty cycle. Increasing the duty cycle increases the power budget (battery drain) and increases the need for heat dissipation. Additionally, multislotting may reduce the sensitivity ...