4-ary, multi-h Continuous Phase Modulation (CPM) has been added to MIL-STD-188-181B for dedicated mode UHF SATCOM operation to provide greater throughput capacity for this power-and bandwidth-restricted communications network. The physical layer of the waveform is designed to occupy the entire channel bandwidth at all data rates, optimizing power and spectral efficiency, but presenting challenges for acquisition. As an example, at low data rates the waveform has a 4 dB processing gain relative to binary phase shift keying (BPSK). Hence this waveform is expected to be acquired successfully at an EdN, 4dB lower than that of BPSK. To acquire the CPM waveform, the modem must be capable of acquiring at low signal-to-noise, in the presence of large unknown frequency and timing offsets, and with the bandlimiting and hard-limiting channel impairments introduced by the satellite. To promote interoperability and reliability, the Joint Interoperability and Engineering Organization (JIEO) requested a synchronization method that would provide reliable acquisition at an E D , corresponding to a 1 x lo" bit-error-rate and also provide automatic data rate and waveform parameter detection. The resulting preamble achieves the aforementioned objectives and, in addition, is short enough in length to allow it be implemented as the burst preamble for future incorporation of the CPM waveform into the MIL-STD-188-182 and -183 demand assigned multiple access modes of operation. In this paper the design philosophy and implementation of the preamble are presented.

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ABSTRACT

The Global Broadcast System (GBS) implemented by the U. S. Department of Defense utilizes commercially-based Digital Video Broadcast (DVB) technology to enable highrate (IO'S of Mb/s), one-way, data dissemination to a large number of users. Currently, however, user terminals are limited to receive-only operation. For many users, a receive-only configuration is not adequate and a low to medium-rate (10's to 100's of kb/s) return channel is required for true network-centric operations and enhanced mission effectiveness. This paper describes a frequency re-use architecture that provides such return channel connectivity to a large number of users without requiring additional satellite bandwidth and with minimal interference to current receive-only users.