action time specified in the handover command. If communication is not supported between the MS and the serving BS during network re- entry, the serving BS will not allocate resources to the MS for transmission during handover interruption time. If the MS is instructed by the serving BS via a handover command, it performs network re-entry with the target BS during action time while communicating with the serving BS. However, the MS stops 6.4 Mobility management and handover communication with the serving BS after network re-entry with the target BS is completed. It must be noted that the MS cannot exchange data with the target BS prior to completion of network re-entry. The network re-entry signaling with the target BS and data communication with the serving BS are time- multiplexed and the multiplexing intervals are negotiated between the MS and the serving BS. Handover Cancellation After handover is initiated, the handover may be canceled by the MS at any time during the handover procedure. After the handover cancellation request is processed, the MS and the serving BS can resume their normal operation. The network can advertise handover cancellation trigger conditions. When one or more of those conditions are met, the MS cancels the handover. When handover execution is complete, the MS is ready to perform network re-entry with the target BS. In addition, a handover cancellation procedure is defined to allow the MS to cancel a handover procedure. If the serving BS indicates in AAI_HO-CMD that CDMA-based handover ranging ix is enabled, a dedicated ranging code/opportunity is allocated to the MS by the target BS, the MS transmits the dedicated ranging code to the target BS during network re-entry. The MAC management messages in IEEE 802.16n are distinguished from their legacy counterparts by an "AAI" prefix denoting the "Advanced Air Interface" messaging. If a ranging channel is exclusively scheduled by the target BS for handover, the MS would use that ranging channel in order to avoid interference by other mobil