Modulation and coding occupy a fundamental place in any mobile or personal communication system. They mediate between the data services, which are to be provided, and the radio systems which form the means of that provision. It is the modulation and coding which determine the quality of the data services, and also how they interact with the radio channel. In particular they determine the resource requirements of the system, in terms of both RF power required and bandwidth occupied. One may regard the encoder/modulator as a single sub-system, which maps data presented to it, by means of a user interface, onto a modulated RF carrier for subsequent processing, amplification and transmission, by the RF sub-system. The demodulator/decoder conversely takes the received RF signal and performs the inverse mapping, back to a data stream for onward transmission. This view underlines the importance of the process; it is the encoding and modulation that determines, for example, the bandwidth occupied by the transmitted signal, whilst it is the demodulator/decoder which determines the quality of the resulting data service availability in terms of BER and delay. It also determines the robustness of the system to channel impairments, due both to the RF sub-systems (such as phase noise and non-linearity) and the RF channel (such as multipath dispersion and fading). Thus the correct choice for the modulation/coding scheme is vital to the efficient operation of the whole system.

Inspec keywords: modulation coding; mobile radio; error statistics; wireless channels

Other keywords: BER; RF channel; RF signal; RF power; user interface; encoder-modulator system; modulation countermeasure; modulated RF carrier; RF subsystem; mobile communication system; data stream; demodulator-decoder system; personal communication system; multipath countermeasure; radio systems; radio channel; modulation-coding scheme; data services

Subjects: Mobile radio systems