CONTENTS

INTRODUCTION

SUMMARY

COMPOSITION OF THE UHF 2 BAND

MONITORING SURVEY

INTRODUCTION

Background

Audit of Mobile Radio Bands in London

0.1 In July 1992 a review was commissioned aimed at examining current use of the radio frequency spectrum from 28-470 MHz and making recommendations in the light of developments.

0.2 The Report of the Review Committee was published in March 1994 (Report of the Radio Spectrum Review Committee Stage 3: 28-470 MHz; ISBN 1 85569 172 8). A response to the Report was published in April 1995 (ISBN 1 85569 172 8). Copies of the Report and the Response are available from:

The Information and Library Service
Radiocommunications Agency
Wyndham House
189 Marsh Wall
London E14 9SX

0.3 One of the recommendations of the Review Committee was that "The existing mobile radio allocations in London should be the subject of a detailed "spectrum audit" to establish whether they are adequate to cope with current demands".

0.4 The Radiocommunications Agency is responding to this recommendation by carrying out audits of the land mobile radio bands on a band by band basis. Reports on VHF High Band and Mid Band were published in March 1995 and September 1996 respectively - "Survey of Land Mobile Radio use in VHF High Band in London" (ISBN 185569 1981) and "Audit of Land Mobile Radio use in VHF Mid Band in the London area" (ISBN 185569 2333). Future audits will cover the UHF1 Band (420 - 450 MHz), VHF Low Band and Band III.

0.5 This Report covers the audit of the UHF2 band and provides details of land mobile radio services operating on UHF2 frequencies (453.00625 - 462.49375 MHz) and channel utilisation data gathered by the Agency’s Mobile Monitoring Group.

OBJECTIVES

0.6 The objectives of the audit were to:

(a) establish the accuracy of the Agency's licensing data, in particular data relating to the technical characteristics of UHF2 radio services, numbers of mobiles in use, and location of services;

(b) monitor radio traffic on UHF2 channels so as to establish current loadings;

(c) analyse the data obtained from (a) and (b) above in order to draw conclusions on the current loading of UHF2 channels in the London area.

METHODOLOGY

Licensing Data Check

0.7 The Agency contacted all UHF2 licensees operating radio services from sites located within a radius of 30 kilometres from Central London (NOR: TQ 300 800). They were asked to complete a questionnaire (copy at Annex A -As this report is very large it is not available on-line, copies can be obtained by contacting:) and to confirm that the details recorded on their Iicence schedule(s) were correct.

0.8 Licensees who did not reply were contacted by staff from the Agency's District Offices. The District staff assisted these licensees in the completion of the questionnaire and verification of the schedule details.

0.9 Questionnaires returned to the Agency undelivered were passed to the relevant District Office so that an attempt could be made to trace the licensee. Appropriate action was taken where services had ceased to operate.

0.10 In order that a degree of confidence might be given to the findings the District Offices made a random sample check of some of the replies received. This involved a visit to the licensee and examination of the radio system.

0.11 The Agency's Mobile Monitoring Group at Baldock obtained radio traffic data, including details of the busy period for each base transmit frequency and each mobile transmit frequency. Information was gathered through the installation of 7 unattended monitoring systems (UMS), located around Greater London. Details of the methodology employed are set out in Section 3 of this Report.

0.12 An analysis of overall channel loadings, based on the full range of channels surveyed, is at Section 4 of this Report; (As this report is very large it is not available on-line, copies can be obtained by contacting) together with a sample of individual channel analyses. A full individual analysis for each of the 274 channels in the UHF2 band is contained in Part 2 of this Report; together with information on the services which operate on these channels.

0.13 The Agency would welcome any views or comments on the contents of this Report. Please send your comments to:

Ray Wilson
Radiocommunications Agency
Private Business Systems Unit
Wyndham House
189 Marsh Wall
London E14 9SX

Tel: 020 7211 0253

SECTION 1

SUMMARY

1.1 The audit established that there were 2031 radio services operating on UHF2 channels in the London area (an average of 7.4 services per channel). It should be noted that these figures exclude the transient services on Short Term Hire, UK General, and Parking & Demonstration channels and services operating on Short Range Business Radio channels.

1.2 The average number of services per channel (excluding the service categories referred to in pare 1.1 above) for the various channel categories in the UHF2 band is as follows:

1.3 Monitoring of the 274 UHF2 band channels indicated that 20.4% achieved a peak occupancy level of between 0.5 and 1 Erlang.

1.4 The rates of occupancy varied according to the types of radio service operating on the channels. For each of the channel categories covered by the audit the percentage of channels in the 0.5 to 1 Erlang range was as follows:

SECTION 2

COMPOSITION OF THE UHF2 BAND

2.1 Private Business Radio (PBR) and Mobile Data Network use of UHF2 is contained within the range 453.00625 - 462.49375 MHz (band edges) providing a total of 274 channels.

2.2 There are 207 dual and 67 single frequency channels in the UHF2 band. These use 12.5 kHz channel spacing. UHF2 channels are designated for use by PBR and National Mobile Data Network services as shown in the Table below:

2.3 UHF2 users in this category are either licensees who have channels allocated for their sole use in the United Kingdom or licensee groups, such as the utilities, who operate on channels which are only assigned to similarly categorised users.

2.4 National Mobile Data Networks are mobile, data only, communications services offered by service providers on a commercial basis. Uses include despatch operations and vehicle location/status messages.

2.5 On-site channels are used for communications between base and mobile. stations, or for mobile to mobile communications. Mobile operation is restricted to within an area of 3 kms radius from a specified location. Typical users include shopping centres and industrial complexes. To ensure maximum reuse of channels, and to reduce to a minimum potential for interference, the Agency imposes tight engineering constraints on on-site users. The maximum permitted base and mobile ERP is 5 watts.

2.6 Wide area shared channels are for communications between base and mobile stations over an area up to 30 kms from specified fixed base station location. In the UHF2 band only dual frequency channels,' are available for wide area use.

The maximum permitted base ERP for wide area shared services with aerials not exceeding 30 metres above ground level is 25 watts. The maximum base ERP for services with aerial heights exceeding 30 metres is 10 watts and is 5 watts if the height exceeds 100 metres. The maximum permitted mobile ERP is 25 watts.

2.7 Most of the channels in the exclusive users category are only available for PBR use on a geographically restricted basis. These channels support radio services which are given a high degree of protection from co-channel interference, including some which cover operations over a large regional area.

2.8 Channels in the limited availability category are only available for PBR use at airports and airfields in the United Kingdom. Applications to use these channels are subject to clearance from the Civil Aviation Authority's Frequency Management Unit.

2.9 The base transmit and mobile transmit legs of the split dual frequency channels are now used as single frequency channels. No new dual frequency assignments are permitted on these charnels.

Miscellaneous

2.10 Short Term Hire (STH) allows a radio dealer to hire equipment to his customers for periods of up to one year. It is used for many short term purposes, including communications at sporting events. STH is also used by organisations which have a permanent radio service but have a short term requirement for additional, or separate, radio capacity.

2.11 The Parking and Demonstration licence is intended primarily for suppliers of radio equipment and permits temporary uses of certain designated frequencies. The licence enables suppliers to demonstrate radio equipment to prospective customers and to install systems for customers who are awaiting a permanent frequency assignment. The licence also permits the demonstration of PMR equipment at exhibitions.

Short Range Business Radio

2.12

Short Range Business Radio (SRBR) is a short range, handheld, two-way speech radio service for business use. The range of the service depends on circumstances but may be 400 metres in open country and less in built up areas. Frequencies are shared by users without planning or control by the Agency.

UK General

2.13 UK General channels can be used for communications between mobile radios anywhere in the United Kingdom provided that the appropriate Agency Local Office is informed in advance. The service operates only on single frequency channels and use of base stations is not permitted.

The most common users are those who move about the country, or within a large geographical area, on a regular basis i.e. they do not have a requirement to use radio long term from a fixed location (fixed site users who require to use radio for more than 12 months are assigned on-site channels). UK General users include exhibition contractors, sporting event organisers, and construction companies. The maximum permitted mobile ERP is 5 watts.

2.14 These channels have been reserved for future growth of specific services such as Mobile Data Networks and to assist with plans to align the UHF2 band with the channelling arrangement used in Continental Europe (many UK radio users who operate on UHF2 frequencies currently receive interference from the Continent because UK use is configured differently).

2.15 The unallocated channels are a resource which has yet to be earmarked for any particular purpose but which could be used for future growth of existing services, for new services, or for future exceptional circumstances.

SECTION 3

MONITORING SURVEY

3.1 Monitoring has taken place from 7 sites selected to represent the majority of London, within the M25. The monitoring has been undertaken by unattended monitoring systems located in secure sites. Computed predictions have been made to indicate the area in which contributions from mobiles would be accounted for within the monitoring results. The general principle is shown in Figure 1 on Page 10.

3.2 The monitoring techniques used for the unattended monitoring systems capture data over 24 hours per day and 7 days per week.

3.3 The UMS contains a programmable receiver which is fitted with a tracking preselector and switchable RF attenuators, the latter enables system performance to be verified. The system is controlled by a dedicated computer that can be programmed locally or by remote modem link. The complete system can be configured, programmed and data extracted by the Agency's Mobile Monitoring facility based at Baldock.

3.4 The units measure field strength, by applying cable loss and antenna factors to the voltage measured by the receiver. This level is then compared to the threshold set in the set up file. Values above the threshold increment the occupancy register. The field strength is also recorded and a report detailing max, min and average field strengths, together with occupancy is created for each frequency monitored. Results can be reported for every 15 min period. Both peak and average detectors can be selected, however the average detector is used for this type of monitoring exercise. Scan rate is a fixed 20 channels per second.

3.5 As the scan rate is relatively slow, the UMS systems were left in place for 10 weeks and the results aggregated for the corresponding 15 minute period for each day. This approach has resulted in approximately 360 samples contributing to each 15 minute period.

3.6 The unattended systems are installed at suitable sites that provide security, power, and telephone line access. The sites have been chosen to cover areas of London, minimising overlap. Site details are given in Table 1 and the colour prediction chart on Page 11 shows the theoretical coverage of each site.

Table 1. Monitoring Locations

3.7 The prediction is based on a minimum field strength of 30dBuV/m at the monitoring site. This is considered to be representative of 1uV at the receiver input at a typical PMR installation. It is clear that some users will be operating with signals below this threshold.

3.8 It can be seen from the coverage chart that a few pockets within London have not been monitored; alternative sites that offered the security and other necessary facilities could not improve the situation. The sites chosen were generally free of in band transmitters, which would raise the noise floor to unacceptable levels. All  UHF2 channels have been monitored covering both base and mobile legs where appropriate.

Monitoring Results

3.9 Each UHF2 channel has been monitored from each location, and detailed plots of activity have been produced. To keep this Report manageable, plots for two locations only are included - the one with the highest peak loading and the one with the lowest loading. The plots for each location are available for inspection, if required.

3.10 Careful comparison of the detailed plots and the licence statistics build up identifiable profiles matched to particular user groups. The profiles have become an important measure in the Agency's work towards defining the quality of service expectations for a channel.

3.11 The occupancy categories have been chosen to indicate the variation of occupancy levels across channels in a particular group.

This report is available in two parts:

Part 1: Overview of findings obtained from licensing and monitoring information relating to occupancy of channels.

Part 2: Analysis of licensing and monitoring information relating to the occupancy of each channel in the UHF 2 band.

As this report is very large it is not available on-line, copies can be obtained by contacting:

The Information and Library Service
Radiocommunications Agency
Wyndham House
189 Marsh Wall
London E14 9SX

Tel: 020 7211 0502 or 0505
Fax: 020 7211 0507
e-mail: library@ra.gsi.gov.uk

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RA 343 (0n-line introduction) February 1998