Audit of Land Mobile Radio use in the UHF 1 band in the London Area

CONTENTS

SUMMARY

COMPOSITION OF THE UHF 1 BAND

MONITORING SURVEY

INTRODUCTION

BACKGROUND

Audit of Mobile Radio Bands in London - Background

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 Library
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, VHF Mid Band, and UHF 2, were published in March 1995, September 1996, and March 1998 respectively - "Survey of Land Mobile Radio use in VHF High Band in London" (ISBN 185569 1981), "Audit of Land Mobile Radio use in VHF Mid Band in the London area" (ISBN 185569 2333), and "Audit of Land Mobile Radio use in UHF 2 Band in the London area" (ISBN 185S69 2694). Future audits will cover VHF Low Band and Band III.

0.5 This Report covers the audit of the UHF 1 band and provides details of land mobile radio services operating on UHF 1 frequencies (425.00625 - 449.49375 MHz) and channel utilisation data gathered by the Agency's Mobile Monitoring Group.

SECTION 1

Number of Services

1.1 The audit established that there were 1821 radio services operating on UHF 1 channels in the London area (an average of 3.9 services per channel). It should be noted that these figures exclude the transient services on the Short Term Hire / Parking &Demonstration channel.

Channel Occupancy

1.3 Monitoring of the 468 UHF 1 band channels indicated that 32.9% 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:

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Description

2.1 Private Business Radio (PBR), Common Base Station (CBS), and National Mobile Data Network use of UHF 1 is contained within the range 425.00625 - 449.49375 MHz (band edges) providing a total of 468 channels.

2.2 There are 374 dual and 94 single frequency channels in the UHF 1 band.  These use 12.5 kHz channel spacing and are designated for use by PBR, CBS and National Mobile Data Network services as shown in the Table below.

2.3 Most UHF 1 channels are only available for civil land mobile radio use in one or more of the major conurbations.  Special arrangements have, however, been agreed which permit national use on some channels (all of the National channels category, fourteen of the National Mobile Data Networks category, and ten of the Onsite single frequency category).

2.4 The channel descriptions used in this Report only give an indication of the predominant use made of each channel, taking into account all of the conurbations where use is permitted. Some channels, therefore, have descriptions which do not reflect the uses made of them in the London area. For example some 'on-site' channels are used by wide area services in London.

Total spectrum: 842 x 12.5kHZ = 10.525MHz

National Channel Users

2.5 UHF 1 users in this category are licensees who have channels allocated for their sole use in the United Kingdom.  Special arrangements apply to the uses which may be made of these channels and, when this audit was conducted, no uses at sites within the audit area had been registered.

2.6 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.

2.7 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 the potential for interference, the Agency imposes tight engineering constraints on onsite users. The maximum permitted base and mobile ERP is 5 watts.

2.8 Wide area shared channels are for communications between base and mobile stations over an area up to 30 kms from a specified fixed base station location.

2.9 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.

2.10 Exclusive users channels support radio services which are given a high degree of protection from co-channel interference.

2.11 Short Term Hire (STH) and Parking and Demonstration uses are now licensed under the Private Business Radio Suppliers Licence. Formerly separate licences were required for these categories.

2.12 STH allows a radio supplier to hire equipment to his customers for periods of up to one year. It is used for many short term purposes, including commurucations 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.

2.13 Parking and Demonstration enables suppliers to demonstrate radio equipment to prospective customers and to install systems for customers who are awaiting a permanent frequency assignment.  It can also be used for demonstrations of PMR equipment at exhibitions.

2.14 These channels have been reserved for future growth of specific services such as Common Base Stations and for the reassignment of radio services displaced as a result of the proposed new Short Range Business Radio allocation at 446.0 - 446.1 MHz.

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.

2.16 Common Base Stations are mobile communications services offered by service providers on a commercial basis. A typical Common Base Station employs a single dual frequency channel, though some service providers offer a multi-channel service. Channel access is shared by a number of independent users on a first come, first served, basis.

SECTION 3

MONITORING SURVEY

Method

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 rnax, 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 luV at the receiver input at a typical Private Business Radio 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 UHF 1 channels have been monitored covering both base and mobile legs where appropriate.

Monitoring Results

3.9 Each UHF 1 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 1 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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