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.