If you have the number of subscribers, GoS, and Erlang for each subscriber, you can expect the required number of channels.
Number of subscribers= 20,000
GoS usually = 0.02
Erlang for each subscriber is usually given to be 25 mErl
for the normal S4/4/4 configuration, each cell will have totally 4TRX * 8 Time slots= 32 channel (TDMA Concept)
1 BCCH and 2 SDCCH for each cell so: 32-3= 29 channels
from Erlang B table, maximum traffic afforded will be 21.04 Erl
number of subscribers will be:
max Erl/ Erl of each subscriber= 21.04/0.025= 841.6 = 841 subscriber for each cell
Total number of sites required will be:
20,000/(841*3)= 7.9= 8 sites approximately
Note: No queue channel assumed
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