Research On The Promotion Of Downlink MU-MIMO Throughput For IEEE 802.11ay

In recent years,as the traffic of wireless communications increases exponentially,existing wireless communication systems can barely support such high data rate requirements.How to increase the capacity of wireless communication systems becomes an urgent problem.Currently,most wireless communication systems operate on high-quality low frequency bands with limited bandwidth resources,facing the difficulties of capacity enhancements.Nevertheless,according to the Shannon theory,the system capacity is proportional to the system bandwidth.Intuitively,it's a straightforward and effective method to exploit the plenty bandwidth resources on high frequency bands to enhance the system capacity.Recently,the 60 GHz millimeter-wave(mmWave)communications have become a hot topic owing to the massive available spectrum on this frequency band.However,different from lower frequency bands,the severe path loss on mmWave bands challenges the design of mmWave communication systems.In order to solve this problem,owing to the ability of focus the energy of desired signals to target directions,the beamforming technology has been agreed to be used in future mmWave communication systems,such as in the IEEE 802.11 ad and IEEE 802.11 ay standards.In mmWave directional communications,the random access process will become more complicated.On the other hand,the orthogonal spatial resources also bring in another freedom in system performance improvements.Compared with the IEEE 802.11 ad standard,the IEEE 802.11 ay standard,which is still under study,will support downlink MU-MIMO technology by deploying multiple antenna arrays in PCP/AP.Currently,the selection rule of users to simultaneously receive data are based on the interference situation without considering the asymmetry of service requirements between them.If the difference of service requirements between the selected users is very big,many transmission resources will be wasted,which will heavily decrease the system throughput.Therefore,the resource scheduling for users with asymmetrical service requirements to increase the system throughput is a meaningful study.In mmWave directional communications,before the data transmissions,the initiator and responder need to conduct the beam training process to find the best direction of transmission and reception beams.However,due to the environmental factors and the users' behaviors,in some directions the corresponding beams may always be idle.Based on this observation,to reduce the complexity of beam training processes,the scheme of decreasing the transmission frequency of beacon frames in these directions with long-time inactive beams is propsed.The focus of this paper is on the methods of improving the system throughput and resource utilization in 60 GHz millimeter-wave communication systems,including the following two aspects:1.In the downlink MU-MIMO scenario of 60 GHz communication systems,to solve the asymmetrical data demand problem between selected users during transmissions,a relayassisted balancing scheme is proposed to improve the system throughput,in which idle STAs in MU groups are utilized to relay data for the STA who has higher traffic demands.In the selection of relay links,a number of relay links are calculated to maximize the system throughput and satisfy the demands of both relays and destination STAs through the two-side matching algorithm,by considering the quality of relay links,the relay STA's capability of forwarding and the destination STA's capability of reception.Simulation results show that using idle STAs to relay data improve the system throughput in the MU-MIMO scenario,and using the matching algorithm to select the best relay link can further improve the system throughput.2.During the beam training procedure with PCP/APs as initiators,how to dynamically adjust the transmission frequency of beacon frames in inactive beam directions is studied.First,the number of cycles of the beams that do not transmit data is calculated,which is then used as a reference to divide the beam activity.For every beam activity,a transmission frequentness of beacon frames is allocated.According to the behavior of STAs,the algorithm of activity switching is formulated with the objective to ensure a slow-growth and fast-recovery state of the beam level in activity switching.Finally,simulations under the assumption of randomly arrived STAs are conducted,and the results show that by reducing the frequentness of beacon frames on inactive beams,this algorithm with acceptable additional access delay can significantly save radio resources.