Tools Required - RF Dimensioner or RF Planning tools i.e. Asset - Terrain / Clutter Database
- GSM900 or GSM1800 - Area Requiring coverage - Coverage Area Probability i.e. 80%, 90%. - Coverage Type i.e. in-building, in-car, etc. - Coverage level i.e. in-building -75dBm, etc.
High Level RF Design Process Procure Terrain and Clutter database
Drive Test to Tune Model
Setup database in Propagation Tool
If time permits ?
Fade margin & LinkBudget Calculation
Service Level Assumptions
To calculate BTS maximum transmit power
If customer doesn’t provide ?
Based on Clutter\Terrain info Grid Design (up to certain extent)
Put Sites into Asset
RF write-up
Fade Margin Drive Test
Fast Fading Signal
+
=
• Fast Fading (Rayleigh) experienced at the scale of •
sub-wavelengths Slow Fading (Shadowing and Blockage) experienced over 10’s of wavelengths
Log Normal Distribution σ
, dB
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
Standard Deviations from Median Signal Strength
Urban Environment σ ~ 5 to 7 dB
Sub-Urban Environment σ ~ 5 to 8 dB
Rural Environment σ ~ 8 to 11 dB
Link - Budget Fade Margin Calculation Shadow Fade Margin depends on: Link Budget - The desired coverage probability Margin Calculation - TheFade standard deviation σ of the lognormal fading
Cell edge probability 50 75 86 90 95
% % % % %
Cell area probability 77 91 95 97 99
% % % % %
M argin for σ = 9 dB 0.0 dB 6.1 dB 9.7 dB 11.5 dB 14.8 dB
Link - Budget Fade Margin Calculation
Essential to balance the uplink and downlink path In-Building Power Budget Uplink MS Transmit Power (CLASS 1) Cable Loss Antenna Gain MS (dBi) Body Loss Max. Path Loss In-Building Penetration Loss Fade Margin (80% Cell Area) Antenna Gain BTS (dBi) ACE Loss (Duplexer) Cable Loss Diversity Gain BTS Receiver Sensitivity
Downlink BTS Transmit Power Cable Loss ACE Loss Antenna Gain BTS (dBi) Max. Path Loss In-building Penetration Loss Fade Margin (80% Cell Area) Body Loss Antenna Gain MS (dBi) Cable Loss Diversity Gain MS Receiver Sensitivity
(dB/dBm) 41 3 1 18 133 21 3 2 2 0 0 -102
Service Level Assumption •
Coverage Threshold at Cell Edge For Outdoor Criteria
Field strength at sensitivity level Body Loss Fade margin (95% Cell area) MS antenna gain Planned outdoor threshold at cell edge for coverage plan •
Coverage Threshold at Cell Edge For In-car Criteria
Field strength at sensitivity level Body Loss Fade margin (90% Cell area) MS antenna gain In-car Penetration Loss Planned outdoor threshold at cell edge for coverage plan •
-102 dBm +2 dB +6 dB +2 dB -96 dBm
-102 dBm +2 dB +6 dB +2 dB -8 dB -88 dBm
Coverage Threshold at Cell Edge For Indoor Criteria
Field strength at sensitivity level Body Loss Fade margin (80% Cell area) MS antenna gain Indoor Penetration Loss Planned outdoor threshold at cell edge for coverage plan
-102 dBm +2 dB +3 dB +2 dB -21 dB -78 dBm
Site Survey - Search Ring Search Rings need to be created around the high level design sites. Dense Urban/Urban areas need to have smaller Search Ring than outskirts area. Include pertinent information such as antenna (building) height, antenna type, etc. in the site search ring form. Essential to impress upon real estate people the closer the site to the center of the search ring, the better it is.
Site Visit RF Evaluation Bring along all equipment necessary in conducting site survey .i.e GPS, compass, etc. Note pertinent information - site obstruction, existing mast or tower, antenna placement issue, surrounding area, etc. Evaluate site
