Cell Selection Parameter

MS_TXPWR_MAX_CCH

RXLEV_ACCESS_MIN

ACS(Additional Reselect Parameter Indication)

PI(Cell Reselect Parameters Indication)

CBQ(Cell Bar Qualify)

CRO(Cell Reselection Offset)

TO(Temporary Offset)

PT(Penalty Time)

CRH( Cell Reselection Hysteresis)

 

 

When MS is powered on, it will try to find a GSM PLMN. MS will select an appropriate cell and read system information. This process is called cell selection. The appropriate cell is restricted by many factors. For example, whether this cell belongs to the selected network (under manual network selection mode), whether the cell is barred, the priority level of the cell, whether the access level of MS is prohibited by the cell, whether the quality of radio channel meets the requirement of communication, etc. Among them, the quality of radio channel is one important factor of cell selection. GSM specification stipulates one parameter called path loss principle C1. The appropriate cell must ensure the C1>0. C1 is obtained by the calculation of cell selection parameters.

After MS selects cell, MS will settle in the selected cell. At the same time it begins to measure the signal level of BCCH of neighbor cells. It records six neighbor cells with the strongest signals (refresh at least every 60s), extracts various system information and control information of each neighbor cell from it. (MS must conduct data block decoding for six strongest BCCH of neighbor cells within 5 minutes, including parameters affecting cell reselection. When MS regards a new neighbor BCCH as one of the six strongest BCCH, it will conduct data block decoding for this new BCCH at least within 30s). Moreover, MS must check one of the six strongest at least within 30s. If BSIC has any changes, it is regarded as a new BCCH and data decoding will be conducted again.  During this process, MS will not stop monitoring PCH. when a certain condition is satisfied, MS will move from current cell to anther cell. This process is called cell reselection. The condition includes many factors which integrate to measure the quality of radio channel. When neighbor cell’s quality of radio channel is better than current cell, cell reselection occurs. The channel quality standard for cell reselection is C2. C2 is obtained by calculation of a set of parameters.