BMWnet IEEE 802 11 Wireless Local Area Networks
BMWnet IEEE 802. 11 Wireless Local Area Networks Prof. W. S. Hwang www. themegallery. com
The IEEE 802. 11 Reference Model PMD:Physical Medium Dependent PLCP:Physical Layer Convergence Protocol MLME:MAC Layer Management Entity PLME:PHY Layer Management Entity SME:Station Management Entity SAP:Service Access Point www. themegallery. com
The 802. 11 Network Architecture CF (Coordination Function) manages the access to the wireless medium. PCF is an optional extension for the support of Qo. S, described in older versions of the standard. www. themegallery. com
802. 11 MAC Frame Formats www. themegallery. com
802. 11 a MAC-Data to PLCP Frame Mapping www. themegallery. com
Spectrum of IEEE 802. 11 channels in 2. 4 GHz v Figure shows the frequency channel allocation in the 2. 4 GHz ISM band. v There are 13 channels available. www. themegallery. com
DCF -- Interframe Spaces www. themegallery. com
DCF -- Collision Avoidance Backoff Time = Random() x a. Slot. Time www. themegallery. com
Fragmentation v Fragmentation limits the probability of long MPDUs colliding. v Data frames protect the subsequent transmissions of their ACK responses and the following data frame with the NAV. www. themegallery. com
DCF -- Hidden Station and RTS/CTS www. themegallery. com
Synchronization v TBTT: Target Beacon Transmission Time, the time the next beacon frame will arrive. v Stations stop initiating frame exchanges upon reaching a TBTT. www. themegallery. com
PCF -- Polling Point Coordinator Station 1 is the PC and polls station 2. Station 3 detects the beacon frame and updates the NAV for the whole CFP. Start of the CFP may be delayed. www. themegallery. com
IEEE 802. 11 e MAC Architecture v Enhanced Distributed Channel Access (EDCA) § Access Category (AC) § Backoff Entities § Parameters Per AC § Medium Access v HCF Controlled Channel Access (HCCA) § Superframe v Block Acknowledgement www. themegallery. com
IEEE 802. 11 e MAC Architecture (cont. ) www. themegallery. com
EDCA -- Access Category www. themegallery. com
EDCA -- Backoff Entities www. themegallery. com
EDCA -- Parameters Per AC www. themegallery. com
EDCA -- Medium Access www. themegallery. com
HCCA -- The Superframe TXOP:Transmission Opportunity www. themegallery. com
Block Acknowledgement www. themegallery. com
Simulation www. themegallery. com
Simulation (cont. ) www. themegallery. com
Simulation (cont. ) www. themegallery. com
BMWnet www. themegallery. com
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