Following decades of closed proprietary satellite systems, the open European Telecommunications Standards Institute (ETSI) standard for interactive broadband satellite services digital video broadcast-return channel via satellite (DVB-RCS) was approved and published in March 2000. Considerable work has been performed by satellite operators, manufacturers and others, in order to deploy DVB-RCS systems for commercial Internet protocol (IP) services. Their efforts have not only resulted in several DVB-RCS systems now in commercial operation, but also in a common focus on interoperability between equipment from different manufacturers through the SatLabs group, working under the auspices of the European Space Agency (ESA). In addition to the open standard aspect, success for DVB-RCS depends on equipment cost and bandwidth efficiency offered by the system, as discussed in this paper. Equipment cost is important as it represents the initial investment for the operator and the final users, while the cost of usage depends on the efficiency, and will, in the long term, be the dominating cost factor. The DVB-RCS specification opens up for a wide range of radio resource management (RRM) implementation possibilities and the RRM plays a key role in optimizing the efficiency of the system for the targeted IP services. This paper presents the main features of a complete DVB-RCS system, the Nera SatLink system, hereafter only referred to as the SatLink system, and offers measurement results and experience from DVB-RCS installations. Critical parts of the system are highlighted, and focus is given to the objectives for current optimization of the system.

We present two multilevel constant-envelope continuous-phase modulation (CPM) schemes with four-dimensional (4-D) trellis coding. The receiver is composed of a simple quadrature demodulator, followed by a symbol-rate sampler and a Viterbi decoder matched to the code trellis. The first modulation is a quaternary CPM scheme whose phase transitions over a symbol interval are those of /spl pi//4-shift quaternary phase-shift keying (QPSK). The demodulator filter is optimized so as to minimize the combined effect of intersymbol interference (ISI) and noise at the decision instants. We use Wei's (1987) 16-state 4-D trellis code, and redefine the set partitioning tree so as to maintain the same minimum distance between parallel transitions as in quadrature amplitude modulation (QAM) signal sets. The resulting modulation outperforms minimum-shift keying (MSK) by as much as 3.5 dB, in addition to reducing the 30-dB signal bandwidth by 20%. Next, we introduce an octonary (8-level) CPM scheme whose phase transitions are those of /spl pi//8-shift 8PSK. The same trellis code and receive filter optimization are also applied to this modulation which is shown to achieve better error rate performance than MSK, while saving some 60% of the transmitted signal bandwidth.