As explained in IEEE 802.16 standard, ranging is the process of obtaining the right timing offset such that the subscriber station transmission are associated to a symbol that marks the start of a minislot boundary.
Timing offset is dictated by the distance between subscriber station (SS) and to the base station (BS) and the equivalent signal propagation delay. The SS begin this process by scanning UL-MAP messages for an available maintenance interval.
Once an available maintenance interval has been determined, the SS will send a Ranging Request (RNG-REQ) message, within this contention based initial maintenance period, to the BS at minimum power level. If this transmission does not receive a response, the SS will increase the power level incrementally as necessary, but not to exceed the maximum specified transmission power.
The BS will reply with a Ranging Response (RNG-RSP) message, which specifies the appropriate timing advance and power adjustment for the SS, as well as the basic and primary managements CIDs.
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