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Higher power limits for licence exempt devices

Executive Summary

Introduction

1.1 This consultation seeks input on the potential effect of increasing the allowable power levels for certain licence exempt devices in certain geographical areas in order to facilitate new services. This could bring about greater flexibility of use, and therefore improved spectrum efficiency, as well as enhancing services such as higher speed broadband to rural communities.

1.2 In the Spectrum Framework Review (SFR) it was noted that the key reason for limiting power in Licence Exempt (LE) spectrum is to reduce interference, however, in rural areas there are likely to be fewer users and hence a lower probability of interference. Therefore, there exists the possibility to increase power levels without causing excessive interference.

1.3 A key element in making any decision is the efficiency of use of spectrum, which is often measured in economic terms. The other considerations when contemplating a change in LE spectrum regulation are:

The social benefits of providing broadband access in rural areas where DSL provision is not widespread.
The effect on Crown users of the bands such as the MoD.
The risks of interference
The alignment with international standards and regulation.

1.4 A study was commissioned to take evidence from industry, examine the technical issues and model the economic effects. The report on this study is available at http://www.ofcom.org.uk/research/technology/overview/ese/exempt/ and evidence from this report is used as part of this consultation.

Rural policy

1.5 Providing enhanced services in rural areas could aid important social goals and improve the quality of life in these areas. There have been many initiatives aimed at achieving this using wireless over the last few years which have had mixed success. The changes proposed here may improve the economics of wireless provision in rural areas. Equally, these changes do not prevent existing licence holders, such as at 3.4 – 4.2GHz providing services in these areas.

Evidence from industry interviews

1.6 In gathering evidence to form the views expressed here interviews were conducted with existing and potential service providers. Interviewees expressed different views on the extent of the benefits for a WBA operator of higher power at 2.4 and 5.xGHz. Comments ranged from “marginal” to “making a significant difference to the business case”. In addition, interviewees had different opinions on whether the main benefit would be in access or backhaul. The views largely depended on the size of operator and the urban or rural nature of the business they were considering. Many of those interviewed expressed concern that higher power devices might be used in urban areas where they might cause significant interference.

1.7 Other views expressed were for more spectrum to be made available to users for BFWA services in the 5GHz bands and for the information contained within the 5.8GHz registration database to be made available in order to enable voluntary co-ordination between users.

The economic value of increased power

1.8 The broad technical conclusions from the research project, opinions from industry interviews and economic results from modelling indicate potential benefits if:

A power increase to 10 Watts at 2.4GHz and to between four and 25 Watts at 5.xGHz is allowed.
A change to setting limits on conducted power and the use of directional antenna were allowed to facilitate point to point links in rural areas.

However such changes must guard against:

Interference in areas where higher powers are allowed.
The migration of higher power devices to areas where they are not permitted, possibly causing interference.

1.9 We note that the draft ECC Recommendation ECC/REC/(06) 04 is currently out for public consultation and it is recommending a maximum 4W EIRP be allowed within the 5.8GHz band (5725 – 5875MHz) for BFWA services. Although there seems to be general stakeholder support for this increase the economic analysis carried out in the study commissioned by Ofcom suggests that this increase may only make a minor difference to the business case in rural areas.

Limitations due to Crown and other users

1.10 The MoD makes significant use of the majority of the 2.4GHz band. In the 5.xGHz bands MoD has use in Bands A and B and the majority of Band C.

1.11 MoD has further indicated a willingness to examine whether higher power could be allowed in the bands where it has significant usage but has no resources to devote to this work for the foreseeable future. However, the MoD have agreed to allow a higher power of 4W in the 5.8GHz band (5725 – 5850MHz) as proposed in ECC Recommendation (06)04 as there is a considerable body of technical work presented as evidence in ECC Report 68 supporting this Recommendation.

1.12 As a result of the restrictions on the bands where there is significant MoD use, for the moment we can only consider the recommendations on the use of significantly higher powers in bands not used by the MoD, namely in the top 33MHz of the 2.4GHz band. Such a segmentation of the 2.4GHz band might bring advantages in ensuring lower power rural systems and other rural users can select channels where they will not receive interference from higher power systems.

The extent of areas considered

1.13 As part of their study, the consultants examined the impact of allowing higher powers over increasing geographical areas. Broadly, their conclusions were:

The benefits grow as the geographical area is expanded from rural through suburban and into urban. However the additional benefits in urban areas are relatively small as there is typically already widespread connectivity available.
The interference also grows as the area over which higher power is used expands, but based on their estimates the cost of interference always remains substantially smaller than the benefits. However, they cautioned that calculating the costs of interference is very difficult in urban areas because of a lack of information on WiFi deployment density and hence the risk that their calculation of interference is incorrect grows as the area where higher power is allowed is expanded.

1.14 These observations lead the consultants to conclude that higher powers could be restricted to rural areas with low risk of interference, but low benefits. As the area over which they are permitted expands the benefits grow but equally so does the risk that the interference estimation is incorrect. There is no single clear-cut boundary point suggested by the evidence.

Example licensing approaches

1.15 In the 2.4GHz band if the areas over which higher powers are used is limited then a mechanism of appropriately licensing devices according to geographical area is required. In this document we set out some possible approaches.

A licence requirement with registration scheme with geographical exclusion zones similar to the one already used for the 5.8GHz band which provides the maximum flexibility but places the onus on users of higher power equipment to deploy it appropriately.
To operate under the existing licence exemption with a requirement for the higher power devices in the 2.4GHz band to be location aware and control their power accordingly without user intervention.

1.16 These two licensing approaches and an overview of regulation using radiated rather than conducted power are set out at Section 5 below.

Options for consultation

1.17 In the 5.8GHz band the options are limited by MoD issues as to whether or not to increase the power to 4W EIRP in the currently available spectrum as proposed in the ECC Recommendation. We intend to implement the ECC recommendation in accordance with draft IR2007 which is attached in Annex 7. There are no other changes proposed and we intend to maintain the existing fees and registration requirement for this licence class in the band.

1.18 In the 2.4GHz band there is insufficient evidence to point to a single preferred outcome and so we are consulting on a range of options. For convenience we have encapsulated these into the decisions and scenarios given below, although other options could be considered.

Option one – maximise benefits. Under this option we would allow higher powers of 10W at 2.4GHz throughout the UK in the band 2450-2483MHz. With no geographical restrictions devices need not be location aware. No registration requirements would be placed on users.
Option two – minimise risks. Under this option we would restrict higher power operations to hamlets, villages and rural towns. Devices would be required to be location aware and only transmit at higher powers if they were in appropriate areas.
Option three – a balance between risks and benefits. Under this option we would restrict higher powers to all areas except large and major urban conurbations. Devices would not need to be location aware but a mandatory registration scheme would operate and users would need to adhere to a code which required them to work collaboratively to resolve interference issues.

1.19 We are seeking opinion on which of these options, if any, is preferred.

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