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số byte yêu cầu; CID cho biết kết nối băng thông uplink được yêu cầu. Tổng hợp và gia tăng các loại BR sẽ được nhìn thấy trong Chương 10. Các tiêu đề SN báo cáo được gửi bởi SS trong khuôn khổ của ARQ Tiêu đề định dạng mà không có trọng tải loại I | 158 WiMAX Technology for Broadband Wireless Access Management message type 24 Reserved DIUC Configuration change count Figure 11.2 DBPC-RSP MAC management message format. If the DIUC parameter is the same as requested in the DBPC-REQ message the request was accepted 11.1.2 Initial Ranging Initial ranging allows an SS joining the network to acquire the correct transmission parameters such as time offset frequency and transmitted power level so that the SS can communicate with the BS. In the OFDM PHYsical Layer initial ranging uses the initial ranging uplink contention slots. First an SS synchronises to the downlink using the preamble and then learns the uplink channel characteristics through the UCD MAC management message. Then the SS scans the UL-MAP message to find an initial ranging contention slots interval. As described in Chapter 10 the BS allocates an initial ranging interval made of one or more initial ranging transmission opportunities. In this interval the SS sends an RNG-REQ MAC management message with a CID value 0 see Table 7.1 . For the OFDMA PHY the initial ranging process is different. It uses initial ranging CDMA codes see Section 10.5 . In OFDM PHY initial ranging transmissions use a long preamble two OFDM symbols and the most robust mandatory burst profile. When the initial ranging transmission opportunity occurs the SS sends the RNG-REQ message using a CDMA code in the case of the OFDMA PHY . The SS sends the message as if it were colocated with the BS as the propagation delay is taken into account in the initial ranging transmission opportunity. 11.1.2.1 Initial Ranging Message Initial Transmitted Power Value The SS calculates the maximum transmitted power for initial ranging denoted PTXIRMAX as follows p TX_IR_MAX EIRXP IR max BS_EIRP - RSS Figure 11.3 Illustration of DBPC Request and Response messages operation Network Entry and Quality of Service QoS Management 159 where BS_EIRP Equivalent Isotropic Radiated Power is the BS transmitted power
