The Implementation And Simulation Of Frame Aggregation Mechanisms And Noise Variance Estimation Algorithm Based On WLAN Link Simulation Platform

As the main standards of WLAN, IEEE802.11defines the relevant mechanisms of the PHY layer and MAC layer of WLAN. IEEE802.11n and the latest IEEE802.11ac protocols introduce many new techniques or enhanced mechanisms to increase the data transmission rate in PHY and MAC, including enhanced modulation and coding techniques, downlink multi-user MEMO, block acknowledgment, frame aggregation technology and so on. Different IEEE802.11protocols defined different types of PPDU frame, including the Non-HT frame format of802.11a protocol, the HT-mixed and HT-GreenField frame format of802.11n protocol and the VHT frame format of802.11ac protocol. There are different composition and generation method of data field and preamble field for different types of frame.The background of this thesis is a R&D project of a local enterprise. This project aims at designing a link level simulation platform based on matlab to support WLAN technologies and features. The goal of the simulation platform is to simulate and verify the performance of key physical layer and MAC layer access technologies for the IEEE802.11standard families, such as a/b/g/n/ac. The main work of this thesis is designed as the following aspects: First of all, we study the structure of different types of frame, and then implement the generation module of data field and preamble field for PPDU frame in IEEE802.11a/n/ac. Besides, the thesis completed the programming of A-MSDU and A-MPDU frame aggregation mechanisms proposed by802.11n protocol. Further more, we set up a WLAN simulation link including MAC layer and the main modules of physical layer, and simulate the performance of the two frame aggregation mechanisms. The system throughput performance of the two frame aggregation mechanisms and Non-aggregation mechanism under different lengths of subframe and different numbers of subframes is analyzed and compared. Finally, four classical noise variance estimation algorithms are discussed, including estimation algorithm based on M2M4, estimation algorithm based on Boumars, estimation algorithm based on maximum likelihood (ML) and estimation algorithm based on minimum mean square error (MMSE). In addition, we simulate and analyze the performance of MMSE and ML estimation algorithm.The thesis is organized as four chapters. Chapter1introduces the background of this thesis, the development of standards, current research progress, the structure and major work of this thesis. Chapter2describes the PPDU frame formate of IEEE802.11a/n/ac, including preamble fields and data fields, as well as the frame aggregation mechanisms proposed by802.11n. Chapter3focus on the realization of frame aggregation mechanism and generation of PPDU frame from the aspects of program with Matlab. The simulation results under different lengths of subframe and different numbers of subframes is analyzed. Chapter4presents and analyzes four noise variance estimation algorithms. The performance evaluation of MMSE and ML under different modulation orders based on matlab is decribed. The last part of the thesis is the inclusion and the future research expectation.