IEEE Std Technique Overview nmgmt.cs.nchu.edu.tw 系統暨網路管理實驗室 Systems & Network Management Lab Reporter :黃文帥 2007/09/18
nmgmt.nchu.edu.tw LOGO Contents What is WiMAX 1 Physical Layer 2 Frame Structure 3
nmgmt.nchu.edu.tw LOGO What is WiMAX Scope: - Specifies the air interface, MAC (Medium Access Control), PHY (Physical Layer). Purpose: - Enable rapid worldwide deployment of cost-effective broadband wireless access product. - Facilitate competition in broadband access by providing alternatives to wireless broadband access. Main advantage: - Fast deployment, dynamic sharing of radio resources and low cost.
nmgmt.nchu.edu.tw LOGO What is WiMAX Deployment
nmgmt.nchu.edu.tw LOGO What is WiMAX Adaptive Modulation Maximize throughput. Minimize average power. Minimize average bit error rate.
nmgmt.nchu.edu.tw LOGO What is WiMAX is not strictly synchronized is a slotted system and all the transmission must be synchronize. uses two-way (Data/ACK) or four-way (RTS/CTS/Data/ACK) handshaking to access channel and transmit data uses a three-way handshaking to set up connection before data transmission (Request/Grant/Transmit). does not distinguish control channel and data channel. In , the control channel and data channel are separated. In , a station must compete for every packet. In , a station can reserve multiple slots for the following packets vs
nmgmt.nchu.edu.tw LOGO Physical Layer Support framing. Support both Time Division Duplex (TDD) and Frequency Division Duplex (FDD), as well as half-duplex FDD (H-FDD). Burst transmission format which supports adaptive burst profiling. - Data allocations within a frame are referred as bursts. - Transmission parameters, including the modulation and coding schemes (burst profiles), may be adjusted individually to each SS on a frame-by-frame basis. - Burst profiles are broadcast via MAC management messages Downlink Channel Descriptor (DCD) and Uplink Channel Descriptor (UCD) periodically. - The actual transmission bandwidth is allocated by BS and broadcast in MAC management messages Downlink MAP (DL-MAP) and Uplink MAP (UP-MAP) in each frame. - Adapt to multiple modulation levels : BPSK, QPSK, QAM-16, QAM-64. Introduction
nmgmt.nchu.edu.tw LOGO Physical Layer TDD - The UL and DL transmissions occur at different times and usually share the same frequency. (SS does not receive and transmit data at the same time) - A TDD frame has a fixed duration and contains one DL and one UL subframe, whose durations can vary. FDD - The UL and DL channels are located on separate frequencies. - A fixed duration frame is used for both UL and DL transmissions. - The H-FDD SS does not receive and transmit data at the same time. PHY Duplexing Option
nmgmt.nchu.edu.tw LOGO Physical Layer TDD Frame Structure PS (Physical Slot) - A unit of time, depend on the PHY specification, for allocating bandwidth.
nmgmt.nchu.edu.tw LOGO Physical Layer FDD Bandwidth Allocation
nmgmt.nchu.edu.tw LOGO Frame Structure Downlink Subframe TTG/RTG (Transmit/Receive Transition Gap) - A gap between the downlink burst and the subsequent uplink burst in a time division duplex (TDD) transceiver.
nmgmt.nchu.edu.tw LOGO Frame Structure Uplink Subframe SSTG (Subscriber Station Transition Gap)
nmgmt.nchu.edu.tw LOGO Frame Structure OFDMA Frame Structure