Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

WiMAX 251Read RF-Channel ListScan FrequenciesIdentify best frequenciesNext frequencyDL-Sych. Acquisition (Broadcast Info.)Check BS-IDfailurefailureDerive from FCH/MAPs, UL/DL ParametersFigure 5-29Terminal station downlink frequency scanningFigure 5-29. The idea is to scan all available carrier frequencies and then from thetransmitted downlink broadcast FCH and DL-MAP zone retrieve the right base stationID. If it is successful, further information related to the new terminal station isextracted from both downlink and uplink MAPs, i.e. ranging invitation grant.– Ranging process. After receiving the corresponding invitation for transmitting theranging messages, the terminal station transmits its long burst, called the ‘rangingburst’, to the base station with a given power setting. The main goal in the basestation is to measure the so-called timing advance (propagation time between theterminal station and the base station) which will be considered in the MAC beforetransmitting any data burst from a terminal station. This is to avoid any burst collisionat the base station. In the case where the base station does not receive a rangingburst from this new terminal station (due to a possible collision or weak receivedpower), a new grant will be assigned and the procedure will be repeated with ahigher terminal station transmit power until an exact timing advance measurementis done (see Figure 5-30). After completing the ranging process, the terminal stationwaits for an assignment of a normal data grant.– Capability negotiations. Based on the standards and the supported profiles (seeSection 5.3.6) each terminal station may implement some extra features/option thatdiffer from the main profiles. These extra terminal station capabilities will be negotiatedwith the base station. They cover the following parameters:• PHY parameters– OFDM parameters (guard time, modulation)– Coding (e.g. block Turbo codes)– Transmit power• Terminal type– Full duplex (FDD or TDD)– Half duplex (H-FDD)