Trans-European Trunked Radio Research Articles

The lessons of Tetra

Some short-range radio devices are suffering interference from the Tetra (Trans European Trunked Radio) radio system. The author reviews the origins of this problem and the lessons for radio designers.

A Simulation Tool to Analyse the TETRA Transceiver Performance in Adverse Propagation Conditions

With growing demand for digital wireless communica tion systems, simulation tools are increasingly impor tant as means for fast, accurate prediction of system performance. The development of a software simula tion tool to analyse the performance of emerging stan dard Trans European Trunked Radio is described. It estimates the average Bit Error Rate of the communi cation link in a variety of propagation conditions, while incorporating different component subsystems in the chain. The modelling process of various components of the transceiver chain and the propagation channel is discussed; the resulting implementation is demon strated. To show the tool's use, the BER performance of TETRA with post-detection diversity under several propagation conditions has been evaluated, with an improvement in the range of 5 to 11.5 dB. System per formance is reported under Simulcast conditions, a transmission strategy that enables coverage of large, low-traffic areas. A model is incorporated using a novel approach that considers the effect of the multipath channel. A significant increase of the expected error floor is anticipated for normal operating conditions. Finally, the RMS simulcast channel delay spread was identified as a suitable parameter to characterise the most critical spots of the area covered.

Noise performance of a Cartesian loop transmitter

The Cartesian loop transmitter is now a well-known linear transmitter architecture and is finding application in a number of mobile radio systems employing linear modulation technologies. In particular, systems utilizing /spl pi//4 DQPSK require a linear transmitter, and many emerging standards [e.g., trans-European trunked radio (TETRA)] provide applications for the Cartesian feedback linearization (CFL) technique. One problem with the CFL transmitter is that its output-noise performance is no longer dominated by that of the RF power module employed within it (as is the case in more conventional transmitter architectures). The use of significant degrees of attenuation, followed by a high level of gain, within the loop, means that the noise performance of the loop is significantly poorer than that of a conventional transmitter. There are a number of tradeoffs that are available to the designer of a CFL transmitter to aid in the optimization of the output-noise performance. This paper presents a derivation of the noise performance of a Cartesian loop transmitter and highlights the design methods that may be employed in order to optimize its noise performance. It also provides a comparison of the theoretically derived behavior with that of a practical transmitter operating in the TETRA (380-400 MHz) band.

The other communications revolution

As GSM continues its advance through the global market for mobile telephones, the TETRA (Trans European Trunked Radio) standard is set to launch a comparable revolution in private mobile radio. The author discusses what TETRA is and its prospects for the future.