Energy-saving Machnism Based On Multi-base Station Cooperation In LTE-A Network

As a major energy consumer in the information and communications industry,the energy saving of mobile communication cellular network has attracted more and more attention.In the component part of cellular network energy consumption,base stations(BS)consume about 57%of the total energy,and about half of energy consumption is the based energy consumption for daily BS operation and has nothing to do with traffic load.Due to the tidal characteristic of mobile communication traffic,lots of BSs in low traffic load status can be switched off in mobile cellular networks.Therefore,switching off BSs is an important energy-saving approach to reduce the based energy consumption in mobile communication cellular networks.The implementation of energy saving mainly by switching off BSs inevitably leads to the network coverage decline,then neighbor compensation BSs have to run a compensation technology to solve the coverage compensation problem in energy-saving region.The traditional compensation technologies,such as enhancing transmit power and adjusting antenna tilt,are restricted because of the inability to restrain the inter-cell interference.Coordinated multi-point(CoMP)technology can restrain inter-cell interference and improve network coverage via multi-BS cooperative transmission.The research on network energy-saving mechanism based on multi-BS cooperation is of great significance.At present,the 4G long term evolution-advanced(LTE-A)system has already entered a large-scale commercial phase,hence this paper mainly studies the energy-saving mechanism in LTE-A networks.For multiple types of network scenarios,including small-scale LTE-A network,large-scale LTE-A network and heterogeneous LTE-A network,we deeply conduct studies on different energy-saving mechanisms based on multi-BS cooperation under the condition of non-limited resource or limited resource.The main contents of our research are as follows:(1)To reduce the energy consumption in non-resource-limted small-scale LTE-A network,we propose a traffic distribution based cooperative energy-saving mechanism.In this mechanism,we adopt dynamic CoMP technology to slove network coverage decline problem caused by switching off BSs.First,a traffic load computing model is established by using poisson point process,then the number of BSs is estimated to be switched off based on the traffic load valley in the network.Second,a BS selection model based on dynamic joint processing technology is designed to decide the BS switch-off and the BS cooperation groups.Finally,users are handed over to the BS cooperation groups following the rule of maximum received signal to interference plus noise ratio(SINR),and then idle BSs are switched off.Simulation results show that adopting proposed energy-saving mechanism,network coverage requirement can be met and data rate of edge users can be improved without extra transmit power.(2)To reduce the energy consumption in non-resource-limted large-scale LTE-A network,we propose a network clustering based cooperative energy-saving mechanism.In this mechanism,we adopt static CoMP technology to slove network coverage decline problem caused by switching off BSs.First,the BSs are grouped into clusters with the equivalent BS method.Second,a BS selection model is designed to determine a BS switch-off group and a BS cooperation group in each independent BS cluster.Finally,on the basis of SINR threshold,users are divided into common users and to-be-compensated users(CU),then the CUs are handed over to different BS cooperation groups.Simulation results show that utilizing the energy-saving mechanism,more BSs can be switched off and network requirement of coverage rate can be met.(3)To reduce the energy consumption in resource-limted large-scale LTE-A network,we propose a Benders' decomposition based cooperative energy-saving mechanism.In this energy-saving mechanism,we adopt static CoMP technology and cooperation reuse technology to slove network coerage decline problem caused by switching off BSs.First,the network is divided by equivalent BS method,meanwhile the cooperation reuse BSs are planned to improve the use ratio of cooperation BSs and reduce the edge region between clusters.Second,the number of BSs in the same cooperation transmission is set in terms of additional overhead and coverage compensation capcity of CoMP to optimize the cooperative BS selection model.Finally,a Benders'decomposition based joint optimization strategy is proposed on the basis of BS switch-off groups and BS cooperation groups,and it aims at balancing system capacity with energy consumption via dynamically controlling the on-off state of BSs.Simulation results show that adopting the energy-saving mechanism,coverage compensation can be achieved and basic network coverage requirement can be met without extra transimt power while switching off more BSs.(4)The cloud of radio access network(CRAN)is a new type of LTE-A network architecture,and we propose a user association based cooperative energy-saving mechanism to reduce the energy consumption in resource-limted heterogeneous cloud of radio access network with Relays.In the energy-saving mechanism,we adopt the two forms of CoMP,including homogeneous cellular CoMP between BSs and heterogeneous cellular CoMP between BSs and Relays,to slove network coverage decline problem caused by switching off BSs.First,the number of BSs to be switched off is estimated based on the traffic load valley in the network.Second,a BS selection model is designed to optimize the two forms of cooperation groups.Finally,a bipartite graph based dynamic BS switch-off strategy is proposed in the case of limited resource of base band unit(BBU)pool and limited capacity of cooperative BSs.It aims at emptying usrs of BS switch-off groups by associating users with BS cooperation groups.Simulation results show that adopting the proposed energy-saving mechanism,coverage performance of energy-saving networks can be met and data rate of edge users can be improved without extra transmit power while switching off some BSs.