Research On The Improvement Of Robustness And Throughput In Millimeter Wave WLAN

Today,multimedia services occupy a large part of wireless communication resources,such as ultra-high-definition video,virtual reality,augmented reality,voice calls,etc.,which require a wide bandwidth and high data rate to ensure the users' service experience.Future communication technologies typically reach gigabits per second or even tens of gigabits per second.The microwave band(below 6 GHz)is no longer able to meet future communication needs due to its limited spectrum resources.The 60 GHz millimeter wave band has very rich spectral resources,usually reaching a bandwidth of 7 GHz to 9 GHz,which can meet the increasing communication rate and capacity requirements.However,millimeter wave communication also faces many challenges,such as severe path loss,high oxygen absorption and poor penetration,thus it is mainly suitable for indoor short-distance and LOS line-of-sight transmission applications.Due to the small coverage of millimeter waves and severe signal attenuation,directional beamforming technology could be used as a key technology that can be applied to millimeter waves.Since beamforming can concentrate signal energy in a certain direction,it can compensate for severe channel attenuation of millimeter waves,and reduce interference.However,directional communication makes the communication link vulnerable to channel fluctuations,such as rotation,movement and occlusion,which will lead to beam misalignment,link quality degradation or even interruption.Therefore,the research on the robustness improvement of millimeter wave communication is very necessary.In addition,directional transmission reduces the degree of interference between links and links with different transmission directions,which brings great potential for spatial multiplexing,and enables different links to simultaneously transmit data on the same frequency band effectively,and thereby increases the system throughput.In this paper,the blockage problem of millimeter wave directional beam transmission is studied.Aiming at the defect of IEEE 802.11 ad beam tracking mechanism,a beam tracking scheme based on alternative link is proposed.When the link is blocked and interrupted,the spare beam can be used to resume the communication,which effectively improves the reliability and robustness of the millimeter wave communications.This paper introduces in detail the selection,establishment and maintenance of the available beams,and the switching process of communication beams,and carries out mathematical calculations and simulation analysis.The simulation results show that the proposed scheme can effectively reduce the communica-tion outage probability and reduce the communication recovery delay compared with the original beam tracking mechanism,which not only improves the robust performance of the millimeter wave communication system,but also further improves the network average throughput.Then,this paper studies the spatial multiplexing mechanism and multi-band operation mechanism in the IEEE 802.11 ad standard,and proposes a low-frequency assisted high-frequency spatial multiplexing scheme to improve the long delay problem in the original mechanism for high-frequency transmission.The scheme proposes to use low frequency to transmit the management and control frames required in the spatial multiplexing process.Further,it saves high frequency time overhead.The high frequency focuses on data transmission,which can effectively improve the high frequency data transmission.And the low frequency allows the AP to know the multiplexing situation,and end the multiplexing instantly.This paper introduces the way of information interaction between high and low frequencies and the specific process of this scheme,and carries out mathematical calculation and simulation analysis on spatial multiplexing time overhead,data transmission volume and spatial multiplexing gain.The simulation results show that the scheme can effectively save the time overhead of highfrequency transmission and effectively improve the transmission of high-frequency data.Compared with the original mechanism,the spatial multiplexing gain is greatly improved,which makes the performance of millimeter-wave communication system be more efficient.