Wednesday, April 25, 2012

BS Color Code (BCC)

BCC is part of BSIC. For its function, please refer to above sections. BCC is composed of 3 bits. The available range is from 0 to 7.
BSIC includes BCC and NCC which is transmitted on SCH. BCC is part of BSIC,used to identify different cell with the same BCCH in the same GSM system. According to the requirements of GSM specification, TSC of BCCH in each cell should be the same with BCC of the cell. Generally this consistency must be ensured by manufacturers. Adjacent or close cells using the same BCCH must have different BSIC, otherwise, inter cell handover might be failure.
BCC planning has three solutions. All of them have taken distance principle into consideration to avoid collisions of adjacent cells with the same BCCH and same BSIC.
1. Based on the existing BCC set, select one of the BCC that has been used by other cell, ensure at the same time that BCC selected will not cause BSIC/BCCH collision with adjacent cell. The advantage of this solution is that it can ensure BCC be even distributed in the whole network. However, if done manually, this solution is time-consuming and troublesome, we can use automatic distribution tools.
2. When defining BCC, try to assign the value from 0. When causes BSIC/BCCH collision, expand the value range. The advantage is that the number of BCC used is kept to the smallest. So when adding a new BTS, in order to avoid the BSIC/BCCH collision, a new BCC can be selected without modifying the BCC of original cells around.
3. Allocate BCC according to its reuse model. That is to use the same BCC within one cluster. It means that adjacent cells cannot use the same BCCH with the service cell. This solution is frequently used, and also the simplest one.

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