Design of CMA's Broadcast System for Meteorological Data—CMACast

Due to broad coverage, low-cost user equipment and easy installation, data broadcast system based on commercial communication satellite has been considered to be the most effective way for data dissemination worldwide. CMA has implemented three satellite broadcast systems, PCVSAT, DVB-S and FENGYUNCast since 1998. PCVSAT and DVB-S, which are Ku band systems covering China and surrounding area, are primarily used to distribute land and air based observation data and products. FENGYUNCast, which is a C-band system covering Asia and part of the south-western Pacific area, is primarily used to distribute space-based observation data and derived products from Fengyun series satellites of China. FENGYUNCast becomes part of GEONETCast Centre of GENONETCast Network in Asia-Pacific region in 2008. Currently PCVSAT, DVB-S and FENGYUNCast have 2400, 700 and 200 users respectively.The coexistence of three broadcast system causes inefficiency and inconvenience to both CMA and users. In 2008, CMA started to build a new system, CMACast, to consolidate the services and users of the three systems together. CMACast is a multimedia dissemination system based on the second-generation Digital Video Broadcast (DVB-S2) technology with both file and multimedia transmission capability, employing a whole 36 MHz C-band transponder of AsiaSat-4 and the transmission capacity can reach up to 70 Mbps. Besides high data rate, CMACast is expected to enhance user management and data exchange cooperation with other regional GEONETCast Network Centres (GNC), including EUMETCast and GEONETCast Americas.CMACast is not only the main component of CMA national and international communication system, but also the main component of WMO IGDDS and GEONETCast. The infrastructural, main function and key technology of CMACast and its comparison between PCVSAT, DVB-S, FENGYUNCast, EUMETCast and GEONETCast Americas are introduced. Infrastructural introduction includes system architecture, coverage and capacity. Main function includes file broadcast, multimedia broadcast, data exchange, user management and data reception. Key technology includes DVB-S2 standard, bandwidth sharing mechanism and dynamic data encryption mechanism. The comparison result indicates that CMACast is a leading satellite data broadcast system in the world with broad coverage, advanced technology and multiple functions.CMACast is on trail operation in the middle of 2011 and will operate simultaneously together with PCVSAT, FENGYUNCast and DVB-S from June to October in 2011, when all the users of the current three systems will transit to CMACast. After that, the current three systems will be closed and CMACast will be the only operating data broadcast system of CMA.