Towards the Elimination of White Spots in Mobile WiMAX Grids through Time Efficient Cognitive Vertical Handoff Algorithm

Table 3

RSS of WiMAX mobile station user with respect to WiMAX and GSM grids.

Optimized time	Current received signal strength (RSS)	Radio access selection	Current handoff status
= above threshold limit	−29 dBm > −31 dBm	1251 dBHz	Currently in WiMAX grid
= below threshold limit; white spot occurred; = searching neighboring WiMAX base station till 20 s and failed	−31 dBm < −30 dBm	600 dBHz	White spot has occurred and efforts to locate neighboring WiMAX base station for horizontal handoff are performed, but handoff fails as neighboring WiMAX base station is not present
= vertical handoff to GSM grid	51.31 dBm	4500 dBHz	Neighboring GSM grid located with good RSS; now vertical handoff to GSM base station is initiated
= horizontal handoff in GSM grid	44.46 dBm	4500 dBHz	As WiMAX grid is not located yet the mobile user can initiate horizontal handoff within GSM grid to neighboring GSM base station
= vertical handoff to WiMAX grid	47.9 dBm	1274 dBHz	Initial WiMAX grid located with good RSS; now vertical handoff to initial WiMAX grid base station is initiated
= horizontal handoff in WiMAX grid	44.14 dBm	2549 dBHz	A new WiMAX base station is present so mobile user can initiate horizontal handoff within WiMAX grid to neighboring WiMAX base station.