Statement
Executive Summary
Rationale for Spectrum Usage Rights (SURs) in a liberalised environment
1.1 As outlined in the Spectrum Framework Review (SFR), Ofcom is moving from a ‘command and control’ regulatory regime to a market-based approach. A key element of this is spectrum liberalisation where the market is allowed to decide on the optimum use of the spectrum.
1.2 Licences are currently stated in many different forms, for example: in terms of a particular technology (e.g. ‘GSM’); or in terms of a particular use (e.g. ‘mobile’). This approach, coupled with careful control of neighbouring uses, lowers the risk of interference. However, it generally does not provide users with a simple and certain mechanism to subsequently change their usage as circumstances change. The principal reason this apparent lack of flexibility in usage has arisen in licences is a concern that if greater flexibility is allowed it may lead to interference.
1.3 There are two key mechanisms whereby the interference caused to neighbouring users can change. The first is the deployment of a different technology, with different in-band and out-of-band emission characteristics. The second is a change in the deployment density or power levels, for example increasing the number of locations where a neighbouring user will be close to a transmitter and hence may suffer interference.
1.4 Existing licences control interference indirectly. For example, a licence specified in terms of technology, such as GSM, controls the allowed transmitter power through the specifications developed for GSM, but only influences the transmitter density in so much as the economics of cellular networks lead to an optimal number of base stations. However, in the example case of cellular networks, as subscriber numbers have grown, the number of base stations deployed has also increased. In practice, this increased density has not caused interference problems because neighbouring licences are also specified in the same manner and as one operator has increased the number of base stations so have all the others. Also, operators have tended to coordinate deployments with their neighbours to reduce the impact of interference. This ‘symmetry’ of use turns out to be inherently resistant to interference because technologies are typically designed to work well when neighbours are using the same technology with similar deployment density.
1.5 If an existing user is allowed to change their usage, perhaps to a different technology or a different application then this symmetry may be lost. Neighbouring users may then have different technologies and different deployment densities increasing the probability of interference. This is the principal reason for seeking an alternative approach to controlling interference.
1.6 A better way to control interference between licensees is to specify in a licence the interference a licensee is allowed to cause, rather than the signal it is allowed to transmit. The licence then directly controls the interference rather than indirectly as is the case in existing licences. In such a system, the rights of a licensee are defined in terms of the maximum interference that can be caused to neighbours. Most importantly, any change of use or technology is allowed as long as it does not increase these levels of interference, achieving our objectives of allowing flexible spectrum use. This new approach is termed ‘spectrum usage rights’ or ‘SURs’.
1.7 This new approach to licensing brings many advantages:
- By directly specifying the parameter which needs to be controlled all unnecessary restrictions are removed from the licence, providing the licensee with maximum levels of flexibility.
- Specification of interference levels allows neighbours to plan their networks more accurately, with less uncertainty or margin for error, because they have a better idea of the interference levels to expect.
- Compared to technology specific licences, specifying rights in terms of allowed interference levels caused leads to more flexibility.
- Clearly setting out the “harm” that one user can cause another simplifies the process of negotiation between users
Context of this Statement
1.8 The SFR, published in November 2004, sets out Ofcom’s long term strategy for managing the radio spectrum. As part of that goal, it addressed the concept of SURs. The SFR outlined at a high level a mechanism by which SURs could be implemented to achieve technology and application neutral access to the spectrum.
1.9 Since then, a range of further activity has been undertaken to achieve this, including:
- Further work undertaken by external consultants, the detail of which can be found in their final report, which led to a consultation on SURs published in April 2006.
- Interaction with stakeholders through workshops on SURs, which led to proposals on its implementation as one option in the spectrum award consultations for the 2.6 GHz and the 1452 -1492 MHz awards.
- A consultation on compliance issues to an SUR licence published in September 2007.
1.10 Responses to the SUR consultations, the consultations on the 2.6 GHz and 1452-1492 MHz spectrum awards and feedback gathered through associated workshops have been taken into account when formulating this Statement.
1.11 This Statement forms a conclusion to the development of SURs. It effectively marks the transition from SUR development to implementation. The Statement sets out how in general we will deploy SURs. When we implement an SUR, for example at an auction, we would normally expect more detailed consultation on the specific implementation issues, typically as part of a broader consultation document relating to the award. We do, however, expect to publish additional detailed consultation and discussion documents periodically, for example on modelling methodologies.
Format of an SUR
1.12 SURs are intended to control three types of interference namely geographical interference, out-of-band emissions and in-band emissions.
1.13 To control emissions into neighbouring geographical areas, the following is used:
- The aggregate PFD (Power Flux Density) at a height H [m] above ground level should not exceed X dBW/m 2/MHz at more than Z% of locations at [definition of boundary ].
1.14 To control emissions outside of the licensee’s frequency band (that appear as in-band interference for a neighbour), the following is used:
- The aggregate out-of-band PFD at a height H [m] above ground level should not exceed X dBW/m 2/MHz at more than Z% of locations in a test area .
1.15 To control emissions inside the licensee’s frequency band (that may cause interference to neighbouring users in frequency due to imperfect receiver filters), the same measure is used:
- The aggregate in-band PFD at a height H [m] above ground level should not exceed X dBW/m 2/MHz at more than Z% of locations in a test area.
1.16 An SUR licence is expected to include in-band, out-of-band and where relevant, geographical interference limits. If requested by stakeholders, other forms of restrictions (e.g. EIRP limit, transmitter density limit among others) can be included in an SUR licence to facilitate particular objectives, such as enhancing coordination. The level of these restrictions can be subsequently changed through negotiations with neighbouring licensees.
1.17 A consequence of defining out-of-band PFD limits is that an indicative interference level (IIL) in a channel can be inferred. The IIL of a channel represents the anticipated maximum interference levels in that channel caused by licensees in adjacent channels (but does not include interference due to non-licensed sources such as EMC).
1.18 IILs are not a guaranteed right that a licensee can rely on. Ofcom will calculate the IIL of each SUR licensee at the time that it is issued where applicable.
Defining and making changes to licence terms
1.19 For new licences, the SUR parameters will be based on an assessment of the most likely uses of that band. Ofcom will make its initial proposals and consult on them. Ofcom will analyse the responses received before finalising the parameter values in the SUR licence.
1.20 For existing licences where the terms are to be changed to SURs, licensees will be asked to specify their views on the relevant parameter values for their licence. Ofcom will carefully assess the feedback received and subsequently propose a set of parameters. Ofcom will consult upon these, if needed, with the relevant stakeholders.
1.21 Once the parameters are set, licensees are able to make a licence variation request to change them.
1.22 An SUR licensee wishing to change its usage will determine whether it can be accommodated within its existing SUR parameters. If it cannot, the licensee needs to ask Ofcom to provide guidance on who may be affected by the change of use and enter into negotiations with the identified licensees to agree the change of use, possibly through compensation for any degradation suffered as a result.
1.23 If the agreement of all affected parties can be obtained, required changes to the SUR parameter values will be made by Ofcom. If the agreement of all parties is not obtained, or not sought by the licensee then if requested, Ofcom will still consider the change request as is its duty, but may need to consult as part of this process.
1.24 In-band and out-of-band PFD limits are defined throughout a licensee’s operational area. Licensees who want differing PFD limits in different parts of their licence area can do so by submitting a licence variation request to Ofcom.
Compliance with an SUR licence
1.25 SURs control the PFD radiated by equipment licensed to operate in a permitted frequency band. Such a definition of SURs is compatible with licence terms that can be specified under the Wireless Telegraphy Act 2006. Hence, SUR licences can operate under the existing legal framework.
1.26 Ofcom’s preferred option is to use modelling to verify compliance to licence terms. The modelling process as well as the inputs used will vary according to the nature of the service being modelled. In addition, Ofcom may decide, where appropriate, to measure the EIRP (Equivalent Isotropically Radiated Power) of the relevant transmitters and compare these to the values provided by the licensee under investigation.
1.27 In case of non-compliance, Ofcom will take appropriate action depending on what is proportionate and necessary in the circumstances.
1.28 SURs are not defined indoors. Hence, only outdoor transmitters and test points are used to verify compliance to licence terms.