TETRA Transmission planning

Preface

"Speak louder, I cannot hear you" or "Are the levels set correctly?"

Transmission planning is essential in a communications system but it is often misunderstood and inappropriate settings made. Whilst these initally appear to be satisfactory serious problems are soon found when trying to interoperate with other equipment, the public telephone networks or in adverse environments. The widespread use of cellular systems has raised the user's expectations of acceptable performance and made them less tolerant of misconfigured systems.

An understanding of the factors which determine audio performance allows the system designer to set the audio parameters to maximise the intelligibility of the system. This is not as difficult as it might at first appear, ITU (formally CCITT) and ETSI have done a lot of work over the years and the results are available to the interested user.

These pages analyse the factors which impact audio performance in the TETRA system, ETSI never came up with a transmission plan for this system unlike GSM, DECT and UMTS (based on GSM). This may be because the equipment manufacturers didn't want a specification which they could be forced to implement or held to account over by the customers. Whatever the reason, the author has encountered problems with TETRA systems which prompted the analysis within these pages.

If any errors or omissions are found within these pages please drop an email to andy@x31.com. If you find the information useful to you please let me know too, a friendly email is always welcome. If you know of any other useful online resources then please send me a link.

You are welcome to use the information in these pages but please give credit to the originator if you make any derivitive works. They took a long time to write so don't claim the material as your own.

Andy Fletcher