Automatic Monitoring System

21 October 2005

Ofcom currently has two programmes which utilise unattended equipment for spectrum management and interference resolution purposes.

  • The remote monitoring and direction finding (RMDF) system currently consisting of 24 sites with the capabilities to detect signals and their direction of arrival from 20 MHz to 3 GHz.
  • The Unattended Monitoring System (UMS) currently with 28 sites capable of providing occupancy information from 20MHz to 3GHz.

These systems have been deployed separately because the RMDF systems are optimally sited on high ground so that they have the highest chance of receiving an interfering signal, whereas the UMS systems are optimally mounted in city centres where they only receive local signals and so can accurately map the usage in that city.

However, a fully comprehensive network, capable of monitoring the radio spectrum and detecting interfering sources over a large part of the country will need far more monitoring stations than currently in the network. An estimate of the number of stations required for covering much of the urban, suburban and some of the rural area is 2000, although this will be investigated in detail as part of the study. These will have to be automatic in operation, have means of downloading reports of interfering sources automatically or on request and be relatively cheap to purchase and maintain to ensure the network costs are not prohibitive.

A feasibility study is underway to investigate a system which will meet the UK radio-spectrum monitoring future needs. The study will develop a specification for a system and a monitoring station will be developed, modelled and experimental development units constructed and tested in the field. The output of this work will allow Ofcom to make a decision whether to proceed to deploy such a network in the future.

Map showing targeting of interferer

Figure 1 Location of a source of radio interference using time difference of arrival with three monitoring sensors

The prototype hardware and software design and manufacture are now nearing completion and system trials will be taking place over the next few months to prove the capability for a range of signal types and frequencies.

Picture of prototype AMS

Figure 2 Automatic monitoring system – prototype hardware

Project status

The study is concentrating on de-risking and identifying the benefits of novel techniques to address the AMS problem. The aim is to combine the new technology with conventional features available in current systems to develop a prototype and design for a future network of AMS sensors.

Work so far has concluded that construction of the AMS systems and network is feasible, though further cost and performance modelling are required. Once the feasibility study is complete, if a positive result is attained, we expect to undertake further exploratory work before taking the system forward and recommending procurement of the monitoring network.

The project is now complete and you can download the final report below. It is a large file, so has been split into two parts for ease of download.