| Millimeter wave refers to the electromagnetic wave with the wavelength of 1?10 mm,and its corresponding frequency is 30?300 GHz.Millimeter wave band has become the most potential wireless communication technology due to its abundant unauthorized bandwidth.The application of millimeter wave technology in 5G network and IEEE 802.11ad/ay WLAN consolidates this cognition.However,compared with the traditional network,the disadvantages of 60GHz millimeter wave network,such as fast signal attenuation,easy to be blocked,short coverage distance and so on,hinder its further development.Fortunately,the millimeter wave is smaller than the traditional low frequency band,and its relatively small antenna size can be easily concentrated into a multi antenna array,thus using directional communication to improve the signal transmission gain through beamformiing technology,but it also brings other challenges:1)How to effectively reduce the beam training time;2)How to improve the spatial reuse of directed network;3)How to increase the coverage of network signal.This thesis focuses on these prominent problems of 60GHz millimeter wave network,and researches from three aspects:reducing beam redirection time by planning scanning angle,improving spatial reuse by reducing signal interference and realizing network signal coverage by deploying multiple APs.The main contributions of this thesis are as follows:(1)This thesis proposes a beam redirection method for 3D space,which is the basis of millimeter wave directional communication.Due to the directional communication and the poor penetration of 60GHz millimeter wave link,it is easy to cause transmission link interruption due to the user's movement or obstruction,resulting in frequent beam training and long beam redirection time,which affects the user experience,especially for the application scenarios with high real-time requirements.Although 802.11ad/ay standard provides a double-layer beam scanning mechanism to reduce the cost of beam scanning,with the increase of the number of phased array antennas,the existing scanning mechanism can not deal with it effectively,resulting in the exponential growth of beam training time.Based on the inherent spatial characteristics of 60GHz millimeter wave,a 3D spatial beam redirection method based on parallel scanning is proposed,which can effectively reduce the beam training time and significantly improve the data transmission rate.(2)This thesis proposes a multi-dimensional spatial r-euse method,which is the key to realize multi-link concurrent transmission.Due to the influence of reflection and multi-path,the beam pattern of millimeter wave often presents irregular shape,which makes the interference between links difficult to measure.However,the current 802.11ad/ay standard does not consider the interference between multiple links,which affects the spatial reuse of multiple links.In order to accurately evaluate and reduce the interference between multi-link transmission,this thesis presents a multi-dimensional spatial reuse mechanism based on signal-to-noise interference ratio(SINR)by using real-time measured signal strength,thus designing the best AP association mechanism and parallel user beam transmission combination in multi-AP link,to effectively improve the spatial reuse and increase the system throughput.(3)This thesis proposes a fine-grained AP deployment method,which is the premise of high quality signal coverage in millimeter wave network.Due to the sensitivity of 60GHz millimeter wave to the surrounding environment,its strong reflection characteristics and weak penetration,AP deployment can not fully learn from the traditional low-frequency methods.In order to improve the coverage of the network and meet the signal quality requirements of different scenarios and users,this thesis proposes a fine-grained AP deployment strategy based on ray tracing,which uses the measured environment and reflection information to simulate the room signal distribution in different locations,and according to the default AP connection rules of 802.11ad/ay,based on the deployment principle of maximizing the signal matrix,the AP deployment is transformed into a combinatorial optimization problem.On this basis,this thesis uses the average strength and similarity of the signal matrix,this thesis proposes a simple and effective iterative location filtering mechanism to reduce the optimization solution space and avoid the iterative algorithm falling into the local optimal solution too fast,to achieve near optimal AP deployment combination and significantly improve the signal coverage and quality.Finally,we build a 60GHz millimeter wave network performance simulation system based on multi-AP collaboration,and verify the effectiveness of our method in a real scenario. |
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