e reverse channels need to feedback a significant amount of information about the link quality. This requires additional channel capacity that is provided under the scheme. For CDMA2000 1x EV-DV the additional capacity is required for the transmission of the voice channel. In 1x EV-DV this is included as part of the basic system, rather than needing an additional carrier for this. EV-DV is an evolution from 1X and does not use the TDMA elements that are included within the DO system. In fact 1xEV-DV is more similar to CDMA2000 1X than 1xEV-DO is. Unlike EV-DO, EV-DV is backwards compatible with 1X. On the forward link, EV-DV has all the channels that 1X has, plus the Packet Data Channel (PDCH) and the Packet Data Control Channel (PDCCH). As the name suggests, the PDCH carries the high rate data. It is similar to, but not identical to, the data channel portion of the EV-DO system. Similarities include the encoding and interleaving functionality as well as the adaptable modulation types (QPSK, 8-PSK or 16-QAM) and the variable transmitted data rate (which is based on channel conditions). The PDCH configuration (data rate, modulation type, target mobile, etc.) can change every slot (1.25 ms). The PDCCH is used to broadcast the configuration of each PDCH slot. Like the forward link, the EV-DV reverse link has all the channels of the 1X system. In addition, it has two new channels: the Acknowl- edgement Channel and the Channel Quality Indicator Channel. The mobile uses the Acknowledgement Channel to inform the base station whether the last packet has been received correctly or not. The CQICH is used to provide the base station with low latency information on the channel conditions. The base station uses the information from these channels (received 800 times per second) to determine which mobile should be serviced in the next slot and which packet should be transmitted to that mobile. W-CDMA The third generation system that is being adopted in Europe and many other places is known as W-CDMA (Wideband CDMA) or UMTS (Un