Resource Allocation And Interference Management Technology In Unlicensed Band LTE And WiFi Coexistence Scenarios

The advent of smart mobile devices and the rapid development of mobile Internet triggered the constant push for higher data rates.How to create innovative technologies to meet the ever-increasing demand for faster mobile data services on scarce cellular spectrum is of great significance.Cellular network operating on the licensed bands is already operating at a very high spectral efficiency,leaving little margin for further practical and cost-effective improvements.Thus,the network capacity is ultimately upper-bounded by the availability of these licensed bands.Therefore,a key element to materialize the full potential of cellular communications is the introduction of a new technology that allows the cellular communications to operate beyond the limited cellular spectrum.In order to cope with the interference and regulatory rules on license-exempt spectrum,a special medium access mechanism is introduced into the existing LTE transmission frame structure to coexist with WiFi.Resource allocation and interference management in the coexistence scenario is also discussed.The specific work and main contributions are as follows:(1)This thesis describes the concept of cellular communications on both licensed and license-exempt/unlicensed spectrum under a unified architecture.The purpose to extend a cellular system into the bandwidth-rich unlicensed spectrum is to form a larger cellular network for both spectrum types.This would result in an ultimate mobile converged cellular network.This thesis examines the benefits of this concept,the technical challenges,and provides a conceptual LTE-based design example that demonstrates how a traditional cellular system like LTE can adapt itself to a different spectrum type,conform to the regulatory requirements,and harmoniously co-exist with the incumbent systems such as Wi-Fi.(2)This thesis propose a general resource allocation scheme with multiple small cell,WiFi,and macro users over licensed and unlicensed bands.The utility maximization of the total small-cell users and WIFI users is achieved by small-cell power control and dynamical time sharing factor assigned in the licensed bands and the channel time allocation of small-cell users and WIFI users in the unlicensed bands.The quality of service(Qo S)for both macro cell user equipments(MUEs)and WiFi system is also taken into account.(3)To reduce the co-channel interference among different small cell users,this thesis address the limitations of the original signal-to-leakage-plus-noise ratio(SLNR)transmit precoding strategy and the active antenna selection(AAS)schemes,then provide a generalizes SLNR precoding model.The co-channel interference among different small cell users can be better reduced by the optimized transmit precoding vector which is obtained by incorporating the antenna-receiver structure into the optimization process.Therefore,the small cell multi-user MIMO performance under various receiver structures can be further improved.