China multimedia mobile broadcasting (mobile TV) (CMMB)
China Multimedia Mobile Broadcasting (CMMB) is a hybrid terrestrial- satellite network for mobile television, comparable in concept to DVB-SH. In this concept, satellite transmission in the S-band provides nationwide coverage, and terrestrial transmission in the UHF range broadcasts regional programs. The receivers therefore require dual-band tuners for the S-band and the UHF range.
The television programs are transmitted as a multiplexed data stream consisting of video, audio and data. Depending on the data rate, several programs can be combined into one service. Such a data stream can contain up to 39 services, each of which is encoded separately and assigned to a logical channel.
CMMB uses the S-band between 2 GHz and 4 GHz for satellite transmission and the frequency range between 470 MHz and 760 MHz in the UHF range for terrestrial broadcasting. The broadcast signals are modulated Orthogonal Frequency Division Multiplex( OFDM), or also with two- phase shift ke ying (BPSK), quadrature phase shift keying( QPSK) and quadrature amplitude modulation (16QAM).