Research On Interference Coordination In Heterogeneous Ultra Dense Networks

With the progress of mobile communication technologies,mobile communication network has transformed from carrying voice service to undertaking broadband data service.Due to the exponentially growing number of user terminals,the communication business categories and application scenarios are getting diversified,which poses new challenges for the system capacity,transmission rate,number of connections,connection density,end-to-end delay and quality of service of mobile communication.The heterogeneous ultra-dense networks(HUDN)is one of the globally recognized key technologies for increasing network capacity,improving transmission rate,number of connections and connection density,shortening end-to-end delay and improving quality of network service.HUDN is the convergence of multi-radio access technology,a new type of network consisting of macro base stations and low power nodes(LPNs)with different functions and covering areas which are deployed with ultra-high density in space.Within the HUDN,the macro bases deployed in the licensed band provide control coverage,service connection and mobility management;the LPNs deployed in unlicensed band offer data coverage of high capacity,high speed,high density and low delay.The HUDN brings the network closer to the users,and augments the network density and network capacity by providing network coverage of multiple formats and multiple levels.However,the dense deployment of network challenges HUDN in terms of radio resources management,interference coordination and optimization of energy efficiency.Dissertation foucus on the "National High Technology Research and Development Program(863 program)" subject "Agreement of 5G Wireless Network Stack Virtualization Key Technology Research and Development","the Ministry of Education-China Mobile Communications Group co.,LTD." subject "Future Network(5G and Beyond)Architecture Research" needs,in view of the HUDN interference coordination problems,the main research contents and contributions are as follows:(1)The proposition of a LTE-Advanced HUND inter-cell interference coordination algorithmIn connection with the downlink interference of macro bases to the users in extended coverage of LPNs brought by macro bases,this dissertation puts forward a split type coverage extension mechanism,which could balance the load of macro cell and micro cell by adjusting LPN bias and stretching the coverage of LPN dynamically,better serving the users in hot spots.What's more,this dissertation proposes a Macro-LPN collaborative interference coordination algorithm to suppress the downlink interference of macro bases to the users in the extended coverage of LPN.LPN could allocate the unoccupied frequency resources to the users in the extended coverage of LPN when the network load is not heavy.If the network becomes busy,the macro users could cooperate to share the frequency resources with users in extended coverage of LPN to suppress the downlink interference of macro base to the users in extended coverage of LPN as well as meeting the needs for throughput of macro users and LPN users,increasing the proportion of active users in the network.(2)The establishment of a HUND interference coordination testing platformA real-time testing platform for interference coordination of HUDN by software-defined radio is established.Compared with computer software-based simulation that is commonly used domestically and overseas,the real-time testing platform combining software with hardware has several advantages: more realistic channel environment and interference environment,higher execution speed and stronger timeliness,so it is suitable for testing and verifying continuously developing HUND interference coordination technology.We designed the working mechanism of the real-time testing platform,and realized the physical layer and the media access layer in line with the 3GPP(3rd Generation Partnership Project)standard.On the testing platform,we adopted the enhanced Inter-Cell Interference Coordination(e ICIC)scheme to test the real-time communication of HUND of two-tier structure(macro cell/micro cell)that conforms to LTE-Advanced norms.This testing platform provided technical means for the design,testing and verification of HUND interference coordination mechanism in real physical environment.(3)Non-collaborative coexistence mechanisms of LTE and Wi-FiIn connection with the interference problem of co-channel deployment of LTE and Wi-Fi,a dynamic non-collaborative coexistence mechanism of LTE and Wi-Fi was designed,in which LTE dynamically adjusts its time length of occupying the bands through detecting the spectrum utilization efficiency of Wi-Fi,so that the LTE and Wi-Fi alternately use unlicensed bands by time-division multiplexing.Then,static LTE on/off,dynamic LTE on/off,Hyper Access Point(HAP)and LBT mechanisms were tested.The results indicate that on dense and ultra-dense scenarios,dynamic LTE on/off mechanism has a higher spectrum utilization efficiency and bigger network throughput,compared with static LTE on/off,HAP and LBT mechanisms.(4)Collaborative coexistence mechanisms of LTE and Wi-Fi and engineering practices.On the basis of non-collaborative coexistence mechanism,a collaborative coexistence mechanism of the LTE and Wi-Fi based on heterogeneous convergence network is proposed.Based on the heterogeneous convergence network,LTE acquires the working information of Wi-Fi through network interface so that LTE is on/off in due time,thus reducing the interference between LTE and Wi-Fi.The experimental results suggest that in the collaborative coexistence mechanism,LTE did not interrupt the transmission of Wi-Fi;LTE and Wi-Fi existed in harmony on an ultra-dense scenario where the distance between LTE and Wi-Fi APs is less than 6 meters.The above findings provide some technical support for the engineering practice about deployment of heterogeneous convergence networks and its interference coordination.