Comparison between time-compression multiplexing and frequency-division multiplexing over narrowband radio systems

Time-compression multiplexing (TCM) is a spectrally efficient, time-domain multiplexing method, which is an alternative to the conventional and widely used frequency-division multiplexing technique (FDM). The paper demonstrates the significant advantages of TCM over FDM when used over narrowband radio systems which contain inherent nonlinearities. Indeed, these nonlinearities can render FDM unusable for many applications, producing quite unacceptable levels of crosstalk for an adequate signal/noise performance. TCM, however, is shown to overcome this problem without utilising excessive bandwidth, usually associated with time-domain multiplexing systems that employ digital modulation: for example, pulse code modulation. The paper contains details of the design and performance of a fully operational, two-channel TCM prototype, including a simple, yet robust, synchronisation system, which is then compared with an FDM system with an equivalent bandwidth.