Researchof Key Technology In Next Generation Of WLAN

With the surge of heavy data traffic multimedia business, such as HD (High Definition) videos, the number of users in WLAN (Wireless Local Area Network) also grows exponentially. Driven by the growing new business in the high-dense scenario, WLAN evolves towards higher data rate and lager user capacity.802.11HEW (High Efficiency WLAN) is put forward as the next generation of WLAN protocols by the IEEE (Institute of Electrical and Electronics Engineers) standards organization in2013, for the purpose of further increase of spectrum efficiency and regional throughput, as well as the improvement of actual performance in high-dense scenario and the enhancement of operators’business support ability. To achieve above goals, some work about multicast packet retransmission and collaborative transmission in MAC (Media Access Control) layer has been done in this thesis. The improvement of protocols and algorithms is concluded as follows:1) The missing packets recovery mechanism applicable to WLAN multicast scenarios referred as MRP-ARQ (Minimum Retransmission Packets Automatic Repeat reQuest) is put forward. Based on multicast transmission model, the theoretical analysis and solvability validation of MRP-ARQ retransmission mechanism is introduced, especially the format of data frame and the encoding and decoding process are demonstrated. Finally a specific example is elaborated to verify this new algorithm. The MATLAB result of MRP-ARQ mechanism shows that MRP-ARQ can significantly reduce the expected transmission count of every packet and has a better performance than traditional retransmission mechanism SR-ARQ (Selective Repeat-ARQ). Even in the high-dense scenario with a high packet loss rate, MRP-ARQ algorithm still keeps a good performance. 2) Two types of cooperative transmission mechanism in MAC layer are proposed, known as distributed T-Coop (Time division Coopertative) mechanism and half distributed T-Coop mechanism. Based on the theoretical model of cooperative transmission, the new designed control frame format, the process of collecting prior information, and interactive process among the sender, the receiver and the cooperative nodes are introduced in detail. The MATLAB performance of T-Coop mechanisms shows that they can greatly reduce the average delay of each packet, make full use of the diversity gain and improve the reliability of data transmission.