Adjacent Area/ Adjacent Frequency Block

Date: 12^th December 2000

Title: Adjacent Area/ Adjacent Frequency Block

Objectives: To identify whether this interference scenario requires consideration in the draft BFWA Inter-Operator Co-existence Guidelines (BFWAtg(00)47).

Contact: Barry Lewis DTI Radiocommunications Agency UK

Tel: 020 7211 0313

Fax:020 7211 00203

Introduction

At the 8^th meeting of the RA BFWA Technical Sub-Group, the issue of adjacent area / adjacent frequency block interference was raised in the context of interference scenarios considered in the guidelines document BFWAtg(00)47. The calculations in this short paper show that given the guidelines for co-channel / adjacent area interference there should be not be excessive interference arising from the adjacent area / adjacent frequency block scenario.

Calculations

For the CO-channel / adjacent area case a Power Flux Density of –102.5dBW/MHz/m² has been proposed.

The frequency plan for 28GHz BFWA includes a 28MHz guard channel between operators in adjacent frequency blocks. Therefore if systems employing 28MHz channelisation are considered then the minimum carrier spacing is 56MHz between the operators.

Referring to ERC Report 099, and the NFD tables contained in Annex 1, the Net Filter Discrimination between a similar 34Mbit/sec victim and interferer is 54dB for a 56MHz separation.

Assuming an interferer radiating towards the licensed area boundary at a power level consistent with a boundary PFD at the limit of –102.5dBW/MHz/m² . Assuming also a central station victim receiver located at the boundary looking towards the interferer with an antenna gain of 15dBi:

Taking into account the NFD the equivalent "in-channel" PFD = -102.5 – 54 dBW/MHz/m²

-156.5 dBW/MHz/m²

Power at the receiver = PFD * Antenna Aperture

Antenna Aperture, assuming 15dBi antenna = -35.24dBm²

Therefore the power at the receiver = -156.5 – 35.24 dBW/MHz = -191.74dBW/MHz

In a 28MHz channel, power received = -177dBW

This is around 40dB below the receiver noise floor based upon the assumptions detailed in doc BFWAtg(00)47r1.

Similar calculations for a subscriber station with a 32dBi antenna show the potential interference to be 23dB below the noise floor assuming a terminal station looking directly over the boundary towards the interferer.

Conclusion

The calculations show that the level of interference in the adjacent area / adjacent frequency block scenario to be considerably below the typical anticipated receiver noise floor even for the (unrealistic) worst case considered above .

Therefore it can be concluded that the frequency separation built into the frequency plan and the CO-channel adjacent area PFD criteria are sufficient to provide protection in the adjacent area / adjacent frequency block scenario and that no additional specific guidelines for this case are required.

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