Resource Allocation And Optimization For Wireless Backhaul Networks

Backhaul networks refer to the links between the base stations with the core network in the telecommunication network,which carries the transmission tasks of the data services and control signaling in the network.In order to continuously meet the requirements of users,the density of cellular networking of operators becomes higher,and the traditional method of laying wired backhaul links has been unable to adapt to the new demands.The application of wireless transmission technology in backhaul network communication has quickly attracted widespread attention from both industry and academia.For the backhaul network,using the wireless transmission than the wired can greatly reduce the difficulty and the costs of the dense network construction,and also promote the flatness and flexibility of network management.According to the terrain conditions and traffic period of the network scenarios,the network resources should be allocated efficiently and reansonably.However,the research on wireless backhaul networks still has the following significant issues:1)Due to the increasing number of mobile user terminals and access base stations in the network,the spectrum resources that can be used for wireless backhaul transmission are seriously scarce,and it is impossible to guarantee the independent backhaul transmission with authorized channels for all base stations;2)The widely used point-to-point network topology for wireless backhaul in the actual scenario is difficult to satisfy the performance requirements of network service;3)When the backhaul network is in low traffic period,the continuous high-power operation of the nodes in the network will bring a lot of energy waste.Therefore,considering both the characteristics of backhaul network and wireless transmission technologies,the network resource allocation and optimization mechanism is investigated in this thesis to provide the efficient,flexible and stable backhaul transmission for future 5G wireless network.We consider these issues from three dimensions:spectrum resources,time resources and base station power resources.Firstly,in order to solve the problem of the scarcity of spectrum for backhaul links,a fast channel rendezvous algorithm based on cognitive radio technology is proposed.Because of the different probability of access nodes selecting channels,another blind rendezvous algorithm based on channel priority is proposed.Secondly,in view of the low transmission efficiency of the existing topology of the backhaul network,a novel wireless backhaul path selection mechanism based on the fog radio access network is proposed.Finally,a power control optimization mechanism of wireless backhaul network for energy efficiency is proposed.The main research content of this paper is as follows:1)Aiming at the scarcity of spectrum resources in wireless backhaul networks,a cognitive clock-based channel hopping blind rendezvous model is constructed by using cognitive wireless technology and dynamic spectrum access technology,which greatly reduces the time to establish channels rendezvous for wireless backhaul access nodes.Firstly,the advantages and disadvantages of the current classic blind rendezvous algorithms are analyzed.Secondly,considering the symmetric and asymmetric network scenarios,a channel bias selection mechanism and random selection mechanism are proposed.Simulation experiments show that in the symmetric scenario,the introducing of the biased channel selection mechanism can significantly reduce the average time to rendezvous.In the asymmetric scenario,the introducing of the random channel selection mechanism not only significantly reduces the average time to rendezvous,but also improves the security of the channel rendezvous process.2)Since there is a priority rank in the channel selection for the access nodes,and there is no cooresponding blind rendezvous algorithm right now,this paper proposes a priority-based rendezvous algorithm that favors the selection of higer probability channels.Firstly,the priority channel network scenario is analyzed.Based on the original channel hopping rendezvous algorithm,the priority channel concept and the evolution algorithm-PREJS are proposed.Then,the performance of different priority channel probabilities for PREJS in symmetric and asymmetric scenarios is analyzed.The simulation results show that the PREJS algorithm can significantly reduce the average time to rendezvous in both symmetric and asymmetric scenarios.3)Aiming at the issue of low transmission efficiency of wireless backhaul network,a wireless backhaul transmission strategy based on fog access network structure is proposed.Firstly,a comprehensive analysis of the three existing backhaul transmission mechanisms:Direct Transmission(DT),Decode and Forward Transmission(DF)and Cloud Access Network Transmission(C-RAN).After the base station tenninal has the capability of independently processing the data signal,the backhaul network structure is more dynamic and flexible due to the use of the wireless relay technology,and the optimal wireless backhaul transmission topology can be selected according to different positions of the users.To maximize the network throughput,the mathematical models of four wireless backhaul transmission mechanisms are given.Simulation experiments show that the F-RAN mechanism can guarantee the best network backhaul throughput under various network scenarios,and can also improve the user data throughput by about 20%in the edge area with poor transmission channel status.4)Considering the backhaul traffic periodicity,a power control optimization mechanism for base station energy efficiency is proposed to improve the energy efficiency for heterogenous dense network.Firstly,according to the traffic fluctuation of backhaul network,the energy consumption model is given.Secondly,by setting the wireless backhaul capacity threshold and sleeping the base station,we establish a traffic-aware energy saving method which can migrate the users from low load base stations to neighbors.Finally,we propose a self-organizing base station power control mechanism based on service coverage,which is used to adjust the signal transmission power of different base stations.The simulation results show that this strategy can reduce the energy consumption of the entire network by about 28%while ensuring network coverage requirements through power control of base stations.