Mobile communications system

摘要

A modulation scheme for use in a digital mobile radio communications system. The modulation scheme uses a four slot time-division multiple access scheme with 12.5 kHz channels. Each 12.5 kHz channel contains plural sub-carriers and each sub-carrier is modulated with a modulation scheme that encodes at least 4 bits per symbol. The modulation scheme can be used in a standalone mobile radio communications system, or in a hybrid mobile radio communications system that also uses standard TETRA modulation schemes. The invention can be used to provide a narrow band digital mobile radio communications system operating in 12.5 kHz channels that has a high degree of compatibility with existing TETRA systems.