| With the increasing data services,people's demand for data transmission rate and transmission quality is also increasing.However,the traditional low-frequency network has limited spectral resources and is unable to meet people's communication needs.Millimeter wave communication is favored by many companies and standardization organizations because of its rich bandwidth and ultra-high transmission rate.The use of directional transmission not only compensates for the shortcomings of the large path loss,but also brings more possibilities for spatial reuse.In addition,the millimeter wave link is easily blocked by obstacles,resulting in continuous changes in link quality.In particular,in dense networks,there are many links and the interference between them is large.Due to the relatively large number of blcokage,the probability of link interruption is higher.In this case,it is very important to improve the overall performance of the network by using a reasonable scheduling scheme.Firstly,this thesis analyzes the communication mode and characteristics of millimeter wave band,and introduces the composition and channel access mechanism of millimeter wave WLAN.The spatial reuse mechanism in 802.11ad/ay is summarized and its efficiency is analyzed.In addition,the relay operation is studied.Then,the spatial reuse scheme of fair scheduling in OBSS(Overlay Basic Service Set)scenario is studied.Although the spatial reuse process has been specified in the existing standards,the interference from other BSS(Basic Service Set)is not fully considered.Therefore,this thesis adopts the network architecture of central control,and the control node schedules the links in the network according to the interference between links in different BSSs.The scheduling problem is described as a multi-objective optimization problem,which guarantees the fairness between links while fully performing spatial reuse and maximizing system throughput.In order to reduce the complexity of solving the problem,a heuristic method is proposed to speed up the solution process and obtain a suboptimal solution in a short time.And then,the proposed scheme is simulated and compared with the time-division scheduling scheme and the random scheduling scheme.Simulations show that this scheme can provide better fairness and system performance.Finally,according to the characteristics that the mmWave link is easily blocked by human body and other objects,a spatial reuse scheme for multi-hop millimeter-wave networks is proposed.When the link is interrupted,the relay mechanism is used for communication.Since the selection of different relay links has different effects on the efficiency of spatial reuse,relay selection and spatial reuse scheduling are considered jointly.The relay nodes are selected by considering the load of nodes and the quality of relay links,and the efficiency of spatial reuse is maximized by optimizing the relay selection process.In addition,the scheduling algorithm is extended from a single-hop network to a two-hop network,taking into account the new features brought about by the use of the relay mechanism,so that it can be scheduled in the presence of relay.And then,the proposed scheme is simulated and compared with the scheme of selecting relay nodes with optimal channel quality and the case without the relay mechanism.The results show that the proposed scheme can reduce the transmission time and provide a better performance. |
