Shu (Marloon) Wang

Instead of the traditional single-coverage model, a layered broadcast model with a two-layer coverage is considered here. In this model, the broadcast station (BS) broadcast two layers of signal to all mobile stations (MS) in the covered area. The signal for the inner coverage has the achievable rate of R 1 and the achievable rate for the outer coverage is R 2 , where R 1 > R 2 . The MS's located near to the outer coverage edge may only be able to reliably decode the data stream of a low rate R 2 while the MS's close to the BS can decode both data streams with a high sum rate R 1 . There many ways for achieving this two-layer broadcasting, including frequency-division multiplexing (FDM), time-division multiplexing (TDM) and superposition precoding (SPC).  Figure 1. Achievable capacity region of broadcast channel. The coverage difference is 6dB.  One key aspect of studying two-layer broadcast is the finding of the achievable broadcast channel capacity, which states

Broadcast multicast service (BMS) has increasingly been popular for delivering multimedia content to mobile users. BMS can be implemented through either a dedicated digital broadcast infrastructure like DVB-T/H/S2, MediaFLO and DMB or a 3rd generation and beyond radio access network like UMTS or cdma2000 network. Traditional digital broadcast air interface and network are designed with the tradeoff between the achievable capacity and intended coverage in mind. The actual throughput is limited by the maximum transmit power and the worst channel condition so that each user in the coverage area can reliably receive services. Therefore, all covered users share services with same quality. The users under good reception condition may not have advantages, even though their achievable throughput can be much higher. In addition, there are also rising interests in upgrading existing digital broadcast systems with more services for new users while be able to keep existing users unchanged, deliver