The ORBCOMM LIVE Project Documentation Site

Disclaimer

Here you can find the results from the Hertford Trials along with Background Information and Data compiled to assist the general understanding of the two radio systems by members of the ORBCOMM LIVE Project. In producing this site every care was taken to ensure the information is accurate and the treatment of both systems is fair, but as with all information of this sort there is a very good chance that the goalposts have moved since it was written. You have been warned. The Webmaster accepts no responsibility for anything!

Background

The project was started to assess in as near to representative live conditions as possible (given time and budgetary constraints) a real ORBCOMM band sharing environment without adversely affecting the JRC PMR system at the same time. The results of the trials are surprising and indicate that the interference potential is far worse than was expected. This appears to boil down to the fact that the ORBCOMM system (in common with most other Little-LEO systems) is very similar in operation to terrestrial trunked PMR systems. The way trunked systems work usually makes sharing of the same frequencies in the same geographic area difficult, if not impossible. Recognising this, the Little-LEO operators had agreed a "Joint Proposal" (see picture below) amongst themselves to avoid using the same spectrum at the same time but until this study it was always assumed that terrestrial PMR was not affected. Whilst most PMR systems should be unaffected, trunked or automated systems certainly are. As far as the trials group are aware the only terrestrial trunked systems currently active on this band are the UK Fuel&Power MPT1327 networks, which is probably of some small comfort to the Little-LEO operators who may suffer unexpected levels of interference as the effects of the two systems sharing the same spectrum are quite likely to be reciprocal.

The "Joint Proposal" submitted by the Second Round applicants provided that they would share portions of the Little LEO spectrum among themselves, including the 148-149.9 MHz uplink band. Specifically, Orbcomm agreed to share the 148.0-148.905 MHz sub-band with E-SAT, Leo One USA and Final Analysis, to share the 148.905-149.810 MHz sub-band with Final Analysis and Leo One, and to share the 149.810- 149.9 MHz sub-band with VITA.

An illustration of the bandplan produced from FCC documentation of the "Joint Proposal".

The equipment used for the ORBCOMM LIVETrial was to be standard communications equipment used by Transco - in fact, it was selected randomly from operational stock and not modified in any way. The ORBCOMM activity was simulated by the Radiocommunications Agency using parameters agreed by the Project Steering Committee as being representative. Simulated activity was of a density and usage mapped as accurately as possible to what would be expected of a working ORBCOMM Communicator population based on the current understanding of the operation of the ORBCOMM network.

The Project Team consists of selected staff of the Radiocommunications Agency, JRC and JRC membership.

Timescales

The Project was to be completed by the end of December 2001 to allow the results to be used in a review of ORBCOMM's operating licence in the UK.

Organisational Structure

The Project is organised into two committees: A Steering Group and a Project Sub-Group.