Transmission of digital signals over MMDS

The paper focuses on the work being undertaken with regard to the testing of the suitability and applicability of 64-QAM modulated signals over MMDS. The work is part funded under the accompanying measures of `Digital Image Transmission´ of the EU RACE II programme as the project DIMMP. The paper outlines briefly the market penetration and service characteristics of MMDS as an analogue transmission medium and the related functionality of such a system. Service comparisons with competing delivery media are described. The required equipment functionality at the transmit chain for the introduction of digital services is then analysed. There follows a description of the equipment configuration for undertaking a series of trials involving the transmission of a 64-QAM signal in an 8 MHz channel at 2.5 GHz. The trials assess the threshold C/N for acceptable BER rates, the associated power efficiency, the impact of phase noise, the appropriate channel coding and the permitted rolloff when used in channels adjacent to analogue PAL signals. The related testing methodology together with some results are then outlined. Finally, the demonstration scenario for the broadcasting of a four programme multiplex over a single MMDS channel is developed