has a value from 1 to 4 which, respectively, corresponds to BR, Initial Ranging, Periodic Ranging, and Handover Ranging.
The periodic ranging takes places during all the time the MS is connected to the serving BS.
In the Ranging and BR messages, we assume that the numbers of BR, Initial Ranging, Periodic Ranging, and Handover Ranging are,,, and.
Based on the feature of temporal locality, accordingly, we forecast the numbers of BR, Initial Ranging, Periodic Ranging, and Handover Ranging sent by a MS next time.
Two types of ranging regions are defined: initial ranging, used during network entry, and periodic ranging, used when the MSs are already connected.
Different sets of codes are used depending on the purpose of the MS: initial ranging, periodic ranging, bandwidth requests, or handover.
where indicates the forecast value of the th message for the time period, and has a value from 1 to 4 which, respectively, corresponds to BR, Initial Ranging, Periodic Ranging, and Handover Ranging.
IEEE 802.16 defines four messages for the use of the CDMA method, that is, Initial Ranging, Periodic Ranging, Handover Ranging, and the aforementioned BR, which are referred to as the Ranging and BR messages in the following text of this paper.
If the BS knows the numbers of BR, Initial Ranging, Periodic Ranging, and Handover Ranging sent by a MS next time, the BS can adjust the allocation of the ranging codes in each ranging code subgroup and improve the transmission success rate of a MS in sending the Ranging and BR messages.
Since the proposed solution shows a (much) faster synchronization time than deterministic methods, it can be used to further increase the energy efficiency of mobile terminals by reducing the frequency of periodic ranging procedures, which are currently used by 4G communication systems to meet the transmission latency requirements.
