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EVOLUTION OF DIRECT BROADCAST
Source:NSMC    Author:admin     IssuedDate:13 November 2011

The present document reports on the ongoing evolution of Direct Broadcast (DB) services.
On one hand, the frequency allocation to Meteorological Satellite Services in L-Band (around 1.7 GHz) is now threatened in the United States and possibly worldwide since the US plan to allocate the upper part of this band (1.695- 1.710 GHz) to broadband mobile communication services. This would affect DB services from current LEO satellite generations, which are planned to continue through the next decade.
On the other hand, it is anticipated that DB services from the future generation of LEO systems will be mainly, if not exclusively, in X-Band (7.750-7.850/7.900 GHz), in order to accommodate considerably higher data rates than current satellite systems. Several LEO systems are already using X-Band: Aqua, Terra, NPP, and FY-3 (for the MPT service). This evolution raises several issues:
- Current lack of CGMS standard protocol applicable to X-Band;
- Higher sensitivity than L-Band to weather conditions;
- Higher class of hardware needed for receiving stations;
- Higher class of user hardware and software for handling high data rates.

This was discussed at the IGDDS meeting in 2010 and reported to CGMS. CGMS-39 took actions to develop a standard and to organize the use of X- Band frequencies for LEO Direct Broadcast. It was furthermore agreed at CGMS that WMO would perform a survey in the global user community in order to assess the need for maintaining a low data rate DB service in L-Band for future systems, in addition to the planned high-rate services in X-Band

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