The IEEE 802.16m amendment distinguishes between four types of handover:
The first type is performed as per the IEEE 802.16-2009 standard. The amendment details description for types 2–4, in addition to inter-RAT handovers.
Similar to how legacy BS operate in IEEE 802.16-2009, an AMS acquires network topology either through periodic advertisements from the ABS or through scanning. An ABS advertisement contains information for neighboring ABSs and R1 BSs, but not neighboring CSG femtocells. A serving ABS may also unicast neighbor advertisement messages. In .16m, an AMS need not be assigned specific allocations by the serving ABS to perform scanning, and need not interrupt its communications with the ABS if such capability is supported. An AMS can prioritize the neighboring BSs to be scanned based on various metrics. Upon reporting these measurements to the network, either the AMS or the network can select a target BS to handover with. Conditions and rules for sending the AMS report are set by the ABS.
A handover can either be initiated by an AMS or commanded by an ABS, and either initiation or the command can include more than one Target-ABS (target ABS). If the ABS's command message contains only one target ABS, the AMS must adhere to this selection. An AMS's handover indication to the ABS results in stopping ...