gacy handover procedures for the first scenario. A new BS periodically broadcasts the system information of the neighboring new and legacy base stations using a neighbor advertisement message. The BS generates the neighbor adver- tisement message based on the cell types of neighbor cells, in order to achieve overhead reduction and prioritize scanning at the MS. A broadcast neighbor advertisement message does not include infor- mation about neighbor private femto-cells. The neighbor advertisement message may include parameters required for cell selection, such as cell load and cell type. The scanning procedure provides an opportunity for the MS to perform measurement of the neigh- boring cells for handover decision. In addition, the IEEE 802. 16m MS may use any intervals that are not allocated by the serving BS to perform self-directed scanning. The MS may perform scanning procedure without interrupting its communication with the serving BS, if the MS supports such capability. The MS selects the candidate base stations to be scanned from information obtained from the serving BS. The BS or MS may prioritize the neighbor base stations to be scanned based on various metrics such as cell type, loading, received signal strength, or geographical location. As part of the scanning procedure, the MS conducts measurements on selected candidate base stations and reports the measurement results to the serving BS. The measurements may be used by the MS or the network to determine the best target BS for the MS. The serving BS defines triggering conditions under which the MS can send the scanning report. In IEEE 802.16m, the handover process may be initiated by either the MS or the BS. In the case of MS initiated handover, the MS sends a handover initiation message to the serving BS (see Figure Privacy Key Management (PKM) is a client/server model between the base station and mobile station that is used to secure distribution of keying material. CHAPTER 6 The IEEE 802. 16m MAC CPS (Part I) 6-15). The serving BS responds to the h