tailieunhanh - WIRELESS TECHNOLOGYProtocols, Standards, and Techniques pdf phần 6

Trạm di động hoạt động ở chế độ rãnh giám sát kênh phân trang cho một hoặc hai khe cắm khe cắm trên mỗi chu kỳ.)r ĐẶC BIỆT DỊCH VỤ Dịch vụ đặc biệt Lựa chọn chỉ số. Trường này cho biết dịch vụ đặc biệt hoặc dịch vụ mặc định được yêu cầu. | discontinued and a new communication with a new base station and necessarily through an analog channel is established. Handoff and Pilot Sets The monitoring of pilot channels is decisive in the handoff process. Within a given CDMA frequency assignment the mobile searches for pilots to detect CDMA channels. Each pilot is associated with the forward traffic channels in the respective forward CDMA channel. A pilot with sufficient signal strength and not associated with any of the forward traffic channels assigned to the mobile station when detected by it causes the mobile station to send a pilot strength measurement message to the base station. The base station in turn can direct the mobile station to perform a handoff. There are four sets of pilots over which the searches are carried out active set candidate set neighbor set and remaining set. The active set contains the pilots as many as six pilots associated with the forward traffic channels currently assigned to the mobile station. The candidate set contains the pilots as many as five pilots that are not in the active set but have sufficient strength to permit successful demodulation of the forward traffic channels associated with it. The neighbor set contains the pilots at least 20 pilots that are neither in the active set nor in the candidate set but are likely to be candidates to be moved to one of these sets. The remaining set contains all the pilots in the system that are not currently in any one of the other sets. Handoff Parameters As can be inferred the pilots play a very important role in the entire handoff process. The search for pilots to detect the presence of CDMA channels to establish the various pilot sets is first step in the handoff process. For each pilot set a search window range of PN offsets is specified by the base station. Within the search window which is centered at the earliest-arriving usable multipath component of the pilot the mobile station searches for usable multipath

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