for higher performance. A maximum of 15 1.25 MHz carriers can be aggregated to provide a 20 MHz of channel bandwidth to a single user. The use of multiple carriers helps in improving the coverage areas for higher data rates. It also assists networks in optimizing data delivery in time and across carriers and offloading traffic to less loaded carriers. Rev. B manages radio resources on multiple carriers by allocating carriers based on application need, device type and airlink load. Rev. B carriers need not be contiguous and can coexist with cdma2000 1X carriers. It allows multiple carriers to be aggregated even if those are in non-adjacent or non-contiguous blocks of spectrum. Rev. B introduces added flexibility by not requiring paired spectrum for downlink and uplinks. This allows deployment of fewer reverse link carriers than forward link carriers, and reduces power demand on the mobiles for applications that are forward link dominated [7]. Figure 5.7 shows the flow of data in the case where we have multiple carriers. The data flow is segmented and distributed over multiple carriers. In the downlink the packet assembly is performed at the device and in the uplink at the BSC. This process achieves lower latency by reducing the transmit time to each packet. cos(2t) cos(2ft) Serial- SMOKE SMD(t) Multi-Carrier Configuration / stream parallel converter Total Bandwidth = 5 MHz cos(2ct) 1.25MHz 1.25MHz 1.25MHz (a) Transmitter 625 kHz 625 kHz Guard Band Guard Band Frequency (b) Power spectrum of transmitted signal cos(2t) cos(2ft) Parallel Received serial signal converter cos(2t) (c) Receiver Figure 5.6 MC-DS/CDMA scheme. Reproduced with permission from Prasad and Hara 1997 IEEE [8] Next Generation Mobile Communications Ecosystem FORWARD LINK Carrier 1 Carrier 2 Internet Carrier 3 Laptop with EVDO Reassembly into single Segmentation into three Data Card high data rate at the lower data rate flows at Single High Data Rate device the BSC REVERSE LINK Carrier 1 Carrier 2 Carrier 3 Internet Segmentation into three Reassembl