To calculate the maximum number of users (M) on a cell, we need to know:
W: chip rate (for UMTS 3,840,000 chips per second)
EbNo: Eb/No requirement (assuming 3dB for CS-12.2k)
i: other-cell to in-cell interference ratio (assuming 60%)
R: user data rate (assuming 12,200 kbps for CS-12.2k)
η: loading factor (assuming 50%)
Take 12.2kbps as example:
M = W / (EnNo * (1 + i) * R) * η = 3,840,000 (3 * (1 + 0.6) * 12,200) * 0.5 = 32.8
The number of users could also be hard-limited by OVSF code space. Take CS12.2k for example:
· A CS-12.2k bearer needs 1 SF128 code.
· Total available codes for CS-12.2k = 128 – 2 (1 SF64) – 2 (4 SF256) = 124.
· Consider soft-handover factor of 1.8 and loading factor of 50%: 124 / 1.8 *.05 = 34 uers/cell.
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There is a litle mistake in the loading factor in the calculation formula, the loading is 50% or 0.5
ReplyDeletein the formula you have included 0.05.
The correction is shown below
Consider soft-handover factor of 1.8 and loading factor of 50%: 124 / 1.8 *.5 = 34 uers/cell.