Saturday, May 7, 2011

Simple definition of Pole Capacity


The pole capacity is the theoretical maximum capacity of the system. In WCDMA, this capacity is only theoretical since, once reached, the system goes in an instable state that leads to its collapse. However it is still a reference for expressing the load.
The uplink noise increases with the loading exponentially. When the uplink noise approaches infinity then no more users can be added to a cell – and the cell loading is close to 100% and has reached its “pole capacity”.
Mathematically, to calculate the uplink pole capacity we need to know:
W: chip rate (for UMTS 3,840,000 chips per second)
R: user data rate (assuming 12,200 kbps for CS-12.2k)
f: other-cell to in-cell interference ratio (assuming 65%)
EbNo: Eb/No requirement (assuming 5dB)
AF: Activity factor (assuming 50%)
Pole Capacity = (W/R) / ((1+f) * AF * 10^(EbNo/10)) = 120.6
To calculate the downlink pole capacity we also need to know:
α: downlink channels orthogonality factor (assuming 55%)
Pole Capacity = (W/R) / ((1- α +f) * 10^(EbNo/10)) = 64.06

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