The industrial narrowband land mobile radio (LMR) devices, as considered in this paper, have been the subject to European standard ETSI EN 300 113 . The system operates on frequencies between 30 MHz and 1 GHz, with channel separations of up to 25 kHz, and is intended for private, fixed, or mobile, radio packet switching networks. Data telemetry, SCADA, maritime and police radio services; traffic monitoring; gas, water, and electricity producing factories are the typical system applications. Long distance coverage, high power efficiency, and efficient channel access techniques in half duplex operation are the primary advantages the system relays on. Very low level of adjacent channel power emissions and robust radio receiver architectures, with high dynamic range, enable for a system’s coexistence with various communication standards without the additional guard band frequency intervals.
On the other hand, the strict limitations of the referenced standard as well as the state of the technology, has hindered the increase in spectrum efficiency, with which the system has used its occupied bandwidth. With its modification as well as with the new emerging specifications (ETSI EN 302 561 , ETSI EN 301 166 ) it is now possible for the up-to-date architectures of narrowband LMR devices to make the utilization of more efficient modes of system operation practically applicable.
The main objective of this paper is to describe the favorable properties of operational modes based on advanced nonlinear and linear digital modulation techniques in order to easy the decision on their usage and thus to help system integrators to increase the efficiency of the narrowband radio channel utilization allocated to the new generation of industrial LMR devices.