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WiMAX Technology for Broadband Wireless Access 2007 phần 6

bit này cho thấy cho dù đó là loại I hoặc II Chỉ ra loại của tiêu đề mà không cần tải trọng (xem dưới đây) Tiêu đề nội dung, chức năng của chuỗi giá trị Type lĩnh vực IDentifier kết nối Kiểm tra Header (cùng như đối với tiêu đề MAC chung) | Multiple Access and Burst Profile Description 129 Order of magnitude 10 values of DIUC Figure 9.15 Illustration of the DCD message transmission period and DIUC use. The value of 1000 frames between two DCD messages is an order of magnitude. The global parts of this message are shown in Table 9.5. The full details of this message including fields lengths are given in Annex B. For this message the OFDM PHYsical interface specifications are considered. 802.16e added new parameters to the DCD message mainly for handover process they are not taken into account in this example. 9.5.5 DIUC Values The DIUC Downlink Interval Usage Code is then the indicator of a burst profile i.e. the PHY characteristics modulation encoding burst profile use condition etc. of a downlink burst. The DIUC is a 4-bit field. The value of DIUC is PHY layer-dependent. Table 9.6 shows the values defined for the OFDM WiMAX PHY Layer. Only 11 values are used for burst profile selection. The correspondence between the 20 modulation and coding scheme possibilities shown in Table 9.5 and the DIUC value a maximal number of 11 burst profile value indicators is the choice of the BS. Each interval or more specifically burst downlink or uplink will have its burst profile and start time described by a DL-MAP IE Downlink MAP Message Information Element or a UL-MAP IE. The DL-MAP and the UL-MAP are MAC management messages that describe the use of the time frame by different SSs see above . The burst profile is referenced by the DIUC value. Only bursts whose profile is explicitly known which is the case for some control bursts example FCH burst see above do not have a burst profile DIUC value. 130 WiMAX Technology for Broadband Wireless Access Table 9.5 Example of a DCD message containing two burst profile descriptions OFDM PHY 802.16e modifications not included . The full details are given in Annex B Field contents Description MAC management message Type 1 Identification of the MAC management message DCD .