Design And Implementation Of 802.11n MAC Firmware

IEEE 802.11 standard had been evolved and already achieved great success since 1997. Acting as a bridge between legacy 802.11a/b/g amendment and latest 802.11ac/ad amendment, 802.11 n amendment introduces many MAC layer methods to match those physical layer transmission rate improvement, thus pushes the overall system efficiency to new heights. Generally speaking, 802.11 n compatible equipment has reached a good balance among cost, power consumption and performance, and will exist on market for a long time. Based on the consideration of cost, customer support and other business factors, developing our own chip that supports 802.11 n and selling together with our application processors is a reasonable choice. Therefore, developing corresponding 802.11 n MAC firmware is also on the schedule.This thesis mainly covers the top-down R&D process of 802.11 n MAC firmware. After briefly introducing the history, status and some basic knowledge of IEEE 802.11 standard, it follows the typical embedded software development procedure. Firstly it analyses the feature and performance requirement. Then it analyzes the division between software and hardware, while trying to maintain both flexibility and efficiency. Later it sets up the top level architecture of software and hardware. By choosing event queue as the fundamental mechanism, it eliminates most of the coupling between internal modules at the cost of a little extra latency. After that it depicts the detailed lower level implementations of STA and AP mode according to function blocks and data flows, including hardware interface(registers, lookup tables, descriptors and interrupts), memory pool management(descriptors and frame buffers), event queue management, application processor interface(data and message), main finite state machine, connecting and disconnecting, TX routine, RX routine, cipher and decipher, aggregation and de-aggregation, power management, scan routing and some key algorithms(QoS, Rate Adaptation, Aggregation Adaptation). Finally the system level test result shows that 802.11 n MAC firmware can fully meet original feature and performance requirement.