Scheduling And Spectrum Sharing In LTE-a Relay System

To meet the increasing requirements of high-speed data traffic in the future mobile communication system, LTE-A (Long Term Evolution-Advanced) system proposed higher requirements in the average cell throughput and the rates of cell edge users. Relay is introduced to the LTE-A system as a low power and low cost network device, which will bring higher system capacity and greater network coverage for the cell. Currently, the major telecom operators, the communication standards associations and the communication equipment makers in the world have all engaged in the research of advanced relay technology, and strive to win a leading position in the development of the next generation mobile communication technology.Because of the advantage of high spectral efficiency, two-way relay is widely discussed recently by domestic and foreign scholars. Moreover, the Samsung Company has delivered proposal in the3GPP (the Third Generation Partnership Project) meeting, which discussed the application of two-way relay technology in LTE-A network. The scheduling problem of multi-user two-way relay network was investigated in this paper by took different user requirements on rate, delay and fairness into account. Firstly, the rate factor was defined by combining SINR (Signal to Interference plus Noise Ratio) balancing technology and optimal power allocating scheme to reflect the user rates. Secondly, the real-time factor was defined to reflect the different delay requirements of different users. Thirdly, the queue factor was defined to reflect the buffer state of each pair of users. According to the above definitions, three scheduling schemes focused on different performance requirements were proposed. The first scheduling scheme jointly considered the rate factor and the real-time factor. The second scheduling scheme jointly considered the rate factor and the queue factor. The third scheduling scheme jointly considered the rate factor, the real-time factor and the queue factor. Performance comparisons among the three proposed scheduling schemes and the conventional rate maximizing scheme were illustrated by numerical results, which proved the performance superiority of the proposed schemes.According to the statistical study, the probability that a mobile user is located indoor is80%. In order to solve the indoor hot spots, dead spots and network congestion problems, indoor relay technology was written into3GPP technical reports. This paper considered the contradiction of wireless spectrum scarcity and low utilization of spectrum, proposed opportunistic spectrum sharing schemes in the uplink of LTE-A indoor relay network making use of path loss, multi-path fading, shadow fading and penetration loss. In the considered network model of this paper, an indoor or outdoor user can obtain the opportunity to share a resource block if its interference power in this resource block was lower than a certain threshold. Spectrum sharing was considered through three steps starting with the benchmark scenario without spectrum sharing, which is, indoor user sharing outdoor spectrum, indoor users inside different areas sharing spectrum with each other and outdoor user sharing indoor spectrum. Simulation results showed that both indoor and outdoor throughputs can be improved in different spectrum sharing steps. The overall cell throughput was improved through adopting the opportunistic spectrum sharing schemes, and the multi-user diversity was effectively exploited in the procedures.