nterface for delivery of content streams to mobile stations across an operator's network. In these services, the subscribers in a certain group receive data from the base station simultaneously, because all subscriber nodes and the base station are synchronized with a global clock. Unlike the unicast cdma2000 1xEV-DO standard which uses ARQ, BCMCS utilize a forward error-correction (FEC) product code for error control, comprising of an inner turbo code and an outer Reed Solomon code [31]. The architecture of BCMCS is shown in Figure 9.21 where three additional mandatory functional elements have been incorporated in the EV-DO network to support BCMCS services: Broadcast Serving Node (BSN): It communicates with the BSC/PCF to add and remove Multicast IP Flows. BCMCS Controller: It is responsible for managing and providing the BCMCS session information to the BSN (via the Serving AAA), the BCMCS Content Server, the MS (via PDSN) and to the RAN (via the BSN function). It also acts as the key distributor (broadcast access key). BCMCS Content Server: The BCMCS Content Server may store and forward the content from the BCMCS Content Provider, and/or merge the content from the multiple content providers. If higher layer encryption is enabled, the BCMCS Content Server encrypts the stream content. It is the last application level entity to manipulate (e.g., reformat) the content prior to the content reaching the BSN. MR: This optional entity is a multicast router. If the content is transmitted over a provisioned tunnel between the BSN and the BCMCS Content Server, this entity is omitted. During the BCMCS operation the content server provides video encoding for each live program in real-time. The application level FEC is applied to the encoded video stream at content server. Then server multicasts each program to a number of BSNs either using IP multicast or IP tunnels in the root-leave- tree format as shown in Figure 9.22. The terminals can join and leave a BCMC tree dynamically. The drawback in this architecture is that th