Wider-band (higher bit rate) CDMA systems

A significant question with 3G CDMA systems is that of handling the much higher bit rates required for the transmission of packet-switched multimedia data traffic. In general, there are three basic ways of increasing the bit rate in CDMA: one could opt for adding frequency bands. This technique of using multiple narrower frequency bands is sometimes called multicarrier CDMA (Milstein, ^{[Milstein, L. 2000.]}) and is the technique adopted for cdma2000. (As will be noted in discussing cdma2000 later, however, initial versions of cdma2000 use a single band only.) A second technique is to increase the chip rate sufficiently so that some higher bit rate data can be transmitted with a relatively high spreading gain. (Recall from Chapter 6 that the performance and capacity of CDMA systems depend on establishing a high spreading gain, the ratio of spread bandwidth W to the bit rate R. An alternate definition of spreading gain, sometimes used, is the ratio of chip rate to bit rate, since the spread bandwidth is directly proportional to the chip rate.) To handle still higher bit rates, one...