8.1 MAC

The ATWILC3000-MR110xA module is designed to operate at low power, while providing high data throughput. The IEEE 802.11 MAC functions are implemented with a combination of dedicated datapath engines, hardwired control logic and a low power, high-efficiency microprocessor. The combination of dedicated logic with a programmable processor provides optimal power efficiency and real-time response while providing the flexibility to accommodate evolving standards and future feature enhancements.

The dedicated datapath engines are used to implement datapath functions with heavy computational requirements. For example, a Frame Check Sequence (FCS) engine checks the Cyclic Redundancy Check (CRC) of the transmitting and receiving packets and a cipher engine performs all the required encryption and decryption operations for the WEP, WPA-TKIP, WPA2 CCMP-AES and WPA2 Enterprise security requirements.

Control functions, which have real-time requirements, are implemented using hardwired control logic modules. These logic modules offer a real-time response while maintaining configurability through the processor. Examples of hardwired control logic modules are the channel access control module (implements EDCA/HCCA, Beacon TX control, interframe spacing and so on), protocol timer module (responsible for the Network Access vector, back-off timing, timing synchronization function and slot management), MAC Protocol Data Unit (MPDU) handling module, aggregation/deaggregation module, block ACK controller (implements the protocol requirements for burst block communication) and TX/RX control Finite State Machine (FSM) (coordinates data movement between PHY and MAC interface, cipher engine and the Direct Memory Access (DMA) interface to the TX/RX FIFOs).

The following are the characteristics of the MAC functions implemented solely in the software on the microprocessor:

  • Functions with high memory requirements or complex data structures. Examples include association table management and power save queuing.
  • Functions with low computational load or without critical real-time requirements. Examples include authentication and association.
  • Functions that require flexibility and upgradeability. Examples include beacon frame processing and QoS scheduling.

Features

The ATWILC3000-MR110xA MAC supports the following functions:

  • IEEE 802.11b/g/n
  • IEEE 802.11e WMM QoS EDCA/HCCA/PCF multiple access categories traffic scheduling
  • Advanced IEEE 802.11n features:
    • Transmission and reception of aggregated MPDUs (A-MPDU)
    • Transmission and reception of aggregated MSDUs (A-MSDU)
    • Immediate block acknowledgment
    • Reduced Interframe Spacing (RIFS)
  • IEEE 802.11i and WFA security with key management:
    • WEP 64/128
    • WPA-TKIP
    • 128-bit WPA2 CCMP (AES)
    • WPA2 Enterprise
  • Advanced power management:
    • Standard IEEE 802.11 power save mode
    • Wi-Fi Alliance WMM-PS (U-APSD)
  • RTS-CTS and CTS-self support
  • Either STA or AP mode in the infrastructure basic service set mode
  • Concurrent mode of operation
  • Independent Basic Service Set (IBSS)