Monitoring RF spectrum use

A portable low-cost monitoring system will help in the fight against illegal use of the radio spectrum, its UK developer has claimed.

The system, which is small enough to fit into a backpack, has already been tested by telecoms regulator, Ofcom.

This latest addition to the RFeye range of products developed by Cambridge-based

can be used in conjunction with static and vehicle-mounted nodes and analysis software. Using these tools, regulators, operators and enforcement agencies can get a picture of how the spectrum is being used, where and by whom, on a scale ranging from a street to nationwide, and can trap transient interference.

Dr Alastair Massarella, CRFS chief executive, explained that the idea for RFeye originated from a previous point-to-multipoint radio telecommunications business, which was plagued by interference in licensed bands from sources such as air conditioning systems kicking in or less sophisticated telecoms equipment.

'The general way of finding interference is to put a lab-standard spectrum analyser in the back of a Land Rover and drive to different locations to take readings,' he said. 'For the type of interference we were finding, you'd want to stay there 24/7 and see the effects of an entire day.'

To achieve this, CRFS developed a ruggedised box containing intelligent spectrum measuring equipment that can broadcast results to a central communications centre or carry out calculations on board.

'The system needs to be economically viable to deploy in large numbers, so you could put 100 of these in a town and have them monitoring spectrum 24/7 to see what the occupancy is and detect transient interference,' added Massarella. 'We have expertise in manufacturing low-cost volume radio equipment so when it is in mass production it can be much cheaper than a traditional spectrum analyser. It can be bolted on to a wall and left, so you are not worried about it appearing on eBay.'

CRFS carries out all the development work in house, including the mechanical design, the electrical and electronic components, RF and antenna design, and subcontracts the manufacturing to SMS Electronics in Nottingham.

The hardware is integrated to the company's own software and a spectrum licence database. 'The nodes are intelligent and can carry out if/then/else action flows,' said Massarella. 'If a node spots unusual activity, it can carry out a more detailed examination, perhaps making a database query to see is a frequency band is being used correctly. It can flag this information to operators via SMS, e-mail or any number of alarm techniques.'

A node sweeps the frequency in the 'sweet spot' of spectrum between 10MHz to 6GHz where most devices operate, analyses it in real time and can measure things such as occupancy.

'We can even micromanage spectra on a small scale over a limited time period for things such as the London Olympics where there's going to be countless events across the city,' added Massarella. 'We want to release spectrum to use elsewhere and make sure it's not being used in the places where we have just released it. This would be an application where we could use the backpacks.'

The backpack RFeye node is around one-fifth of the size of laboratory-based equipment and has a significantly reduced power consumption. It is powered using the latest dry battery technology, which allows the device to operate for eight hours before being recharged in a matter of hours. Once in volume production, CRFS hopes to sell nodes for hundreds of pounds each, as opposed to current systems that can sell for anything up to £20,000.

The key parts of each node are a broadband radio system, capable of quickly digitising broadband data across the target range, DSP (digital signal processing) to put the radio data into a readable form, and a self-contained Linux computer. It also includes GPS and a GPRS/UMTS modem to transmit over a mobile network if necessary, and Ethernet and USB ports.

CRFS recently completed a mobile spectrum survey of the UK for Ofcom in which it gave travelling salespeople a roof-box node mounted on their cars. 'These guys drove around as normal and sent in data sticks to us and we got a picture of spectrum use in the UK,' said Massarella. 'We've now got interest from regulators and other people interested in spectra.' CRFS is currently bidding in a major tender with Ofcom.

'The vision of the company is to have the most knowledge of spectrum use everywhere,' added Massarella. 'To do that we need to measure it, and in order to do that we need to get the price point of the monitoring system down.'