r: The part of the access network that provides one CDMA channel. 5.2.2 1xEV-DO Revision 0 Revision 0 was designed for asymmetric IP traffic. It enables peak data rate of 2.4 Mbps in the downlink and 153.6 kbps in the uplink in a 1.25 MHz carrier. It supports neither circuit switched nor packet switched voice. In commercial networks, Revision 0 delivers average throughput of 400-500 kbps in the forward link and 50-70 kbps in the reverse link. It offers an "always on" user experience and only supports best effort flow of data. It supports applications like broadband Internet access, web browsing, multiple forms of downloads, emails, and SO on. The first Revision 0 system was deployed in South Korea in 2002. 5.2.3 1xEV-DO Revision A 3GPP2 completed the specifications of 1xEV-DO Revision A in 2004. Rev A (TIA-856-A) provides a number of enhancements over Rev. 0 to improve the performance of the network and compete with 3GPP HSPA. These improvements are briefly discussed in this section [2-4]: High Speed Forward and Reverse Links: 1xEV-DO Revision A provides enhancements via both software and hardware to increase the data speeds in the downlink from 2.45 to 3.09 Mbps and in the uplink from 153.6 kbps to 1.8 Mbps. In the downlink two new data rates of 1.5 and 3.1 Mbps were added plus a few in the uplink. Optimized Reverse Link: The uplink of Rev. A has been redesiged to provide significant speed and capacity improvements. It has been designed to support low latency applications such as VoIP. To support higher data rates two new modulation schemes namely QPSK and 8-PSK have been introduced. Additional key improvements are the presence of a number of packet sizes, four-slot sub-packet transmission format, a three sub-packet interlace and Hybrid ARQ. The Rev. A four-slot sub-packet transmission format along with Rev. 0 sixteen slot (26.6 ms) is shown in Figure 5.3. The total transmission time is the same as Rev. 0, however interspersing the subframes with other packets provides time for the Access Rev. 0: 16 Slots 16 Slo