 GPS methods. Computer games generally fall into the interactive class of service. However, if the game is highly interactive, then it would be better to play it in the conversational class with its even stricter delay requirements. 10.3.1.4 Background class. E-mail, SMS, and database downloads are less delay- sensitive because the subscriber does not need to make an immediate response. A de- lay of several seconds or even a few minutes may make little difference in these ser- vices. Typically, these data have high accuracy requirements and must be delivered error-free. If the forward error correction is insufficient, it may be supplemented by er- ror detection and retransmission because the lack of delay sensitivity allows this. 11 In network-assisted GPS, the base station forwards GPS timing information to the user ter- minal, but the user terminal does not have its own GPS. A third option would be to have a GPS in the user terminal. In that case, the user terminal would identify its own location and inform the base station. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Worldwide CDMA Standards Worldwide CDMA Standards 10.3.2 W-CDMA speech coding W-CDMA uses adaptive multirate (AMR) speech coding with multiple rates that de- pend on radio conditions. This is not the same as cdmaOne and cdma2000 lowering their bit rates during times of reduced voice activity. The change in coding is triggered by changing radio conditions, not by changing speech patterns. The W-CDMA codec has eight rates from 12.2 kbps down to 4.75 kbps. The 12.2-kbps AMR speech codec is the same as GSM, 7.4 kbps is the same as the US-TDMA codec, and 6.7 kbps is the same as the Japanese PDC codec. Every 20 ms the system evaluates the load on the air in- terface and the radio link quality of the speech signal. Depending on the results of these measurements, the system may c