Interference based Channel Allocation

Interference based Channel Allocation

? IBCA aims at reducing interference between cells

? IBCA dynamically allocates MAIO so that less interference should take place

? IBCA improves spectral efficiency.

1. IBCA Algorithm : The IBCA algorithm includes the following procedures: Calculating interference probability

* Collecting call information

* Dynamically measuring IBCA neighboring cells

* Estimating the C/I ratio of a new call

* Estimating the interference a new call causes to established calls

* Selecting the optimal MAIO

>  Calculating Interference Probability :

In an IBCA-enabled cell, the interference probability between MAIOs in each mobile allocation (MA) group must be calculated, and the calculation result must be saved. When evaluating a channel, the BSC directly obtains the interference probability from the saved data.

The method for calculating the interference probability between two MAIOs is as follows:Assuming that:

* The cells where two calls were made share the same MA group.* The Hopping Sequence Number (HSN) for the MA group is set to 0.

* The frame offset between the two cells is FNOFFSET1, and the MAIOs used by the two calls are MAIO1 and MAIO2.

If (FNOFFSET1 + MAIO1) % N = MAIO2, the two calls experience co-channel interference.

If (MAIO1 + N + FNOFFSET1 – MAIO2) % N = 1 or (MAIO2 + N + FNOFFSET1 – MAIO1) % N = 1, the two calls experience adjacent-channel interference. Here, N indicates the number of frequencies in the MA group.