Scalable voip mobility intedration and deployment- P31: The term voice mobility can mean a number of different things to different people. Two words that can be quite trendy by themselves, but stuck together as if forgotten at a bus station long past the last ride of the night, the phrase rings a number of different, and at times discordant, bells. | 300 Chapter 7 throughputs of around 80kbps by occupying portions of those channels. The downlink channel does not require any contention as it is point-to-multipoint but the uplink channel has to allow for initial uncoordinated access. Thus a contention-based scheme is used. GPRS provides for a radio with four different data rates from 8 to 20kbps per slot. GPRS is sometimes called because it is an addition to the 2G GSM. To improve on the available throughput for data users GSM has the Enhanced Data Rates for GSM Evolution EDGE technology. This is a higher-throughput way of sending traffic over the air for packet downloads. EDGE upgrades the radio to include more sophisticated coding techniques. For a more detailed introduction to coding techniques please refer back to Chapter 5 s description of Wi-Fi radios. EDGE defines nine data rates from to . Furthermore EDGE offers better error correction coding methods to recover from noise or out-of-range conditions. It is impressive to see how little bandwidth the licensed carriers have to work with given that there is not a wide range of available frequencies to begin width and the signals travel so far that spatial reuse becomes a challenge at every level. EDGE is sometimes referred to as a technology because it improves upon GPRS but isn t as modern as the newer 3G technologies. CDMA CDMA the name of the mobile technology not the radio encoding is defined in IS-95. IS-95 does use the code division multiple access scheme to provide separation between devices on the channel. CDMA as a radio technology works by using the notion that streams of bit patterns can be orthogonal to one another mathematically. For IS-95 each phone is given a unique pseudorandom sequence known as a PN sequence. The point of the sequence is that no two sequences should correlate to each other or agree in a statistical way over any reasonable period of time. The insight into CDMA is that the user can use these .
