TIM encoding for IEEE 802.11ah based WLAN

Trafc indication map (TIM) is one information element (IE) that is used to indicate the buffered frame status for the stations (STAs) and carried in the regularly transmitted beacons in the IEEE 802.11 based WLANs. To reduce the overhead of TIM signaling for the recent standardization of IEEE 802.11ah, which supports a large number of STAs and operates at the sub-1GHz frequency, a hierarchical structure for TIM encoding and four encoding methods are accepted into the 802.11ah task group specication framework document (SFD). In this paper, the methods of AID (Association Identier) Differential Encoding (ADE) and ADE with AID interpolations are proposed to further reduce the encoded bitmap length within the same hierarchical structure. The simulation results illustrate that the proposed methods can improve the performance.