Co-Ordination Across Licensed Area Boundaries

Title: Co-ordination across licensed area boundaries

Source: RA

Objectives: Group to agree in principle the process for cross boundary co-ordination.

Contact: DTI Radiocommunications Agency UK
                 Tel: 0207 211 0313
                 Fax: 0207 211 0115

BFWA Co-existence.

Introduction

Licensing of both the 28GHz and 40GHz bands for BFWA will require some means of assessing the co-existence of:

1. Operators using the same frequencies in neighbouring licence regions.

2. Operators using adjacent frequencies in the same licensed area.

3. The Fixed Service BFWA operation and other services such as Radio Astronomy in the 40GHz band and co-ordinated FSS stations in the 28GHz band.

4. UK BFWA services along international boundaries.

This document assesses only the case 1) above which can be considered in two parts. In the first instance it is proposed that a trigger for action required to facilitate co-existence is introduced. In the second instance, some means of testing whether that trigger level is exceeded is needed.

For case 2) above, studies are continuing within CEPT/IEEE and ETSI. For cases 3) and 4), further study is required.

Trigger for Co-ordination

Whilst there is a wish to minimise the burden on operators to co-ordinate across their boundaries, there is a potential for co-frequency interference across any licensed area boundary. This interference could be harmful to the network of a neighbouring operator and therefore needs to be controlled and restricted to some relatively harmless known level.

Document BFWAtg(00)03 detailed work carried out to assess the potential for a Power Flux Density (PFD) limit at the licence area boundary which should not be exceeded associated with a co-ordination distance shared equally between the two licensed areas. Any stations located at distances from the licensed area boundary by more than the co-ordination distance will not require any action in terms of potential co-ordination with the neighbouring operator. The PFD is based on typical receiving antenna performance and the co-ordination distance is dependant upon the EIRP of the interfering station. (Refer to BFWAtg(00)03 for more detail). The recommendations of the previous work are as follows:

28GHz:
BFWA transmitters should be co-ordinated when the PFD generated at the network’s service area boundary exceeds the following value:
[- 102.5 dBW/MHz/m² ]

For typical values of EIRP expected in the 28GHz band, co-ordination distances are:

[27.5 km] for P-MP Base Station (EIRP = 0.5dBW/MHz)
[16km] for P-MP Terminal Station (EIRP = 11.5dBW/MHz)

40GHz:

BFWA transmitters should be co-ordinated when the PFD generated at the network’s service area boundary exceeds the following value:

For typical values of EIRP expected in the 40GHz band, co-ordination distances are:

[18km] for P-MP Base Station (EIRP = 0.5dBW/MHz)
[10km] for P-MP Terminal Station (EIRP = 11.5dBW/MHz).

The figures remain in [ ] whilst further work on these issues continues.

The level for the PFD trigger threshold has been set assuming a worst case LOS alignment between a Tx and victim Rx using the same frequency. The above figures are based on a long term interference limit of I/N = -10dB.

In addition the report detailed in BFWAtg(00)03 also recommends that, to minimise the need for individual subscriber station co-ordination, operators in adjacent service areas should avoid co-channel, co-polar operation within 5 km of their network service area boundaries. This issue may need further discussion and would be dependant upon co-operation between operators concerned.

PFD Calculation

In assessing the boundary PFD, use of a simple LOS calculation will usually lead to over estimation of the boundary PFD resulting in unnecessary constraints on deployment and operation. Therefore a more complex calculation is needed that takes into account the terrain effects, clutter effects and the effects of propagation enhancements. This last point brings in an element of time variability leading to the question;

Since the PFD is based on a degradation in system gain of 0.5dB in the victim perhaps the time percentage should be small, say 1% of time.

Where possible established ITU-R Recommendations should be employed for assessing the PFD level including, ITU-R Rec. F.452-9 and any other associated Recommendations.

Co-ordination distance

As noted above, the co-ordination distance within each service area is dependant upon the EIRP in the direction of the licensed area boundary. It varies in accordance with the following graphs

 For the 40GHz band: (based on typical receiver antenna gain = 15dBi)

For the 28Hz band: (based on typical receiver antenna gain = 15dBi)

Resultant Action

If the calculations show that the boundary PFD is exceeded for greater than 1% of time then some action is required on the part of the operator to reduce the PFD at the boundary. There are two possibilities:

1. To take some action to reduce the EIRP in the direction of the boundary such that the PFD limit is no longer exceeded.

2. Enter into discussions with the affected neighbour regarding a relaxation of the PFD at the boundary or movement of the PFD evaluation point. This may be useful in cases where one operator has an attractive service area close to the border of his licence area but the neighbouring area has no similar attractive area close to the border.

The RA is proposing development of a tool to assess compliance based on the points under the "PFD Calculation" heading and that the detail process will be published in some form of RA Information document similar in nature to the Frequency Assignment Criteria documents produced for fixed link assignments.

Process Flow

The following block diagram proposes a suggested flow associated with this activity:

Note: Option 2 may be useful in cases where one operator has an attractive service area close to the licence region boundary but the operators in neighbouring regions have no similar attractive areas close to the boundary.

Addendum 1 to BFWATG(00)32 - 27th July 2000

Co-ordination Process for Adjacent Region Co-Channel BFWA Systems

Note: Option 2 may be useful in cases where one operator has an attractive service area close to the licence region boundary but the operators in neighbouring regions have no similar attractive areas close to the boundary.

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