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BFWA Point to Point (P-P) Infrastructure Links at 28GHz |
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BFWA Point to Point (P-P) Infrastructure Links at 28GHz |
Date: 22 May 2000
Title: BFWA Point to Point (P-P) Infrastructure Links at 28GHz
Objectives: To present some initial calculations for discussion regarding the use of in band P-P infrastructure links.
Contact: Jim Nixon DTI Radiocommunications Agency UK
Tel:
020 7211 0128
Fax:020
7211 0155
Introduction
The use of "in band" P-P links to satisfy BFWA infrastructure requirements has been previously discussed. This paper presents some initial calculations of typical required transmitter EIRPs for three P-P link lengths, from 5km to 10km, and then presents the resulting co-ordination distances based on a P-MP station interference limit of -147 dBW/MHz.
P-P EIRP Calculations
Given that:
EIRPTX = FSPL + Latmos – GR + (PR(min) + FM)
where:
EIRPTX = Transmitter EIRP
FSPL = Free Space Path Loss (20 log 4p R/l dB)
Latmos = Atmospheric Loss (0.12R dB)
GR = Receiver Antenna Gain
PR(min) = Receiver Sensitivity
FM = Fade Margin
Link Length (km) |
FSPL at 28GHz (dB) |
Latmos (dB) |
GR (dBi) |
PR(min) (dBW) |
FM (dB) |
EIRPTX (dBW/MHz) |
5.0 |
136 |
0.6 |
35.5 |
-102 |
12.8 |
-2.6 |
7.5 |
139 |
0.9 |
35.5 |
-102 |
18.4 |
6.3 |
10.0 |
142 |
1.2 |
35.5 |
-102 |
23.6 |
14.8 |
Co-ordination Distance
The following interference geometry applies:
1Report on BFWA co-existence
at 28 & 42 GHz, Aegis Systems Limited [BFWAtg(00)03].
2For a BER 10-6, 28MHz channel bandwidth, 34 Mbit/s, QPSK system.
3For vertical polarisation, availability of 99.95% and rain rate of 32 mm/hr.
and now:
PR = EIRPTX - FSPL - Latmos + GR
where:
EIRPTX = P-P Transmitter EIRP
FSPL = Free Space Path Loss (20 log 4p R/l dB)
Latmos = Atmospheric Loss (0.12R dB)
GR = P-MP Receiver Antenna Gain (15 dBi)
PR = P-MP Interference Limit (-147 dBW/MHz)
we find:
| P-P Link Length (km) | X (km) |
| 5.0 | 16.5 |
| 7.5 | 49.5 |
| 10.0 | radio horizon |
Conclusions
These initial calculations have shown that short length, low EIRP P-P links may be able to be deployed without infringing the current proposed co-existence criteria. However, the usefulness of these links for BFWA infrastructure is questionable.
It is clear that as the link length increases, or higher availability or link bit rates (higher modulation) are required, the consequent increase in link EIRP leads to leads to much greater co-ordination distances and possibly leads to problems deploying these links within a region without causing undue interference to neighbouring BFWA operators.
In addition, an analysis of the interference from adjacent channel P-P links in the same geographic area also needs to be considered to assess the overall co-ordination requirements.
| BFWATG(00)34 |
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