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How does it help?

Core to supporting our vision for future wideband wireless communications systems and novel applications and services is the provision of access to broad bandwidths of radio spectrum. At the frequencies of interest for typical communications systems this bandwidth is a scarce resource. More frequency channels could be made available if successful sharing between different services could be achieved. Examples of this might be a wireless LAN sharing some radio spectrum with a broadcaster.

Another SES project considers cognitive radio. This is one particular approach by which spectrum access could be shared in the future. This study aims to look at other innovative methods for sharing the spectrum between multiple services in order to maximise its utilisation and to enable provision of new services.

Ofcom is researching this area to:

• establish the degree by which the spectrum efficiency and utilisation could be improved by using such methods.
• evaluate the risks of increasing the sharing of the radio spectrum in terms of how new services in the band will affect quality of service so as to determine where maximum benefit lies to the UK in terms of increased services and increased interference.

The work has undertaken a detailed analysis of sharing strategies. It has concluded that few novel sharing schemes seemed to be feasible with currently deployed radio systems. However a number of schemes may be viable for future systems designed specifically to facilitate sharing. We have evaluated possible schemes on the basis of:

• The amount of spectrum that might be made available.
• The risks of increased interference with existing users.
• The trade-off between increased multiplicity of radio services or increased reliability of radio services.

The most promising schemes are:

• Beacons transmitted from receivers
• Co-ordinated beacons managing requests
• Widespread frequency hopping
• Spectrum commons
• Spectrum commons, where devices move if interfered with

These sharing schemes are outlined below and are now undergoing detailed modeling to establish their benefits.

Figure 1 Co-ordinated beacons at each receiver in the primary service managing requests from the secondary service

Figure 2 Dedicated beacons managing requests amongst multiple services

Project status

Our work in this area has concluded that few novel sharing schemes seemed to be feasible for sharing between existing commercial technologies and services. It should be noted that the Cave Audit is considering sharing between commercial and non-commercial users. There are different issues which apply in this instance, for example the incentives for optimal spectrum usage, and thus we might reasonably expect a different outcome.

However considering the cost/benefit for possible future commercial technologies and services several candidates were identified with potential for sharing. Further work will model these potential candidates in detail and will establish the likely cost/benefit of implementing the solution in practice. In addition, future work will aim to examine what degradation of existing quality of service levels would be tolerable to users in order to increase the number of radio services available.

Our work here suggests there is little regulatory action required in the short term. In the longer term five to ten year timescale there may be beneficial courses of regulatory action.

This project is now completed and the full report can be downloaded below.

• Improving the Sharing of the Radio Spectrum: Final Report [pdf]
• Improving the Sharing of the Radio Spectrum: Final Report – Executive Summary [pdf]

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