Research On Resource Scheduling And User Fairness Underlaying Cooperative Multicast

The current international mainstream technology standards of promoting the implementation, Long Term Evolution(LTE), can provide a downlink peak rate of100Mbit/s and uplink 50Mbit/s in the spectrum of 20 MHz. With the rapid development of mobile Internet and intelligent terminals, fast, accurate transmission of large amounts of data puts forward high demands on technology development.Therefore, LTE proposes Multimedia Broadcast Multicast Service(MBMS), which achieves efficient one-to-many data transmission, improves spectral efficiency.MBMS technology requires users within the cell to be formed multicast group, and the base station uniformly transfer data to users within the multicast group via multicast channel, sharing resource. Because of the time-varying characteristics of the wireless channel, MBMS faces the contradiction between the cell throughput and fairness among users. Higher fairness ensures that the difference among the data rate of the users within multicast group is small.Firstly, this paper expounds several classical multicast scheduling algorithms, and points out their shortcomings on throughput or fairness; secondly, this paper proposes one improved algorithm based on MBMS in LTE, which is called the algorithm of Two-I Proportional Fairness Scheduling(TIPFS). TIPFS algorithm considers the differences in the throughput of multicast groups and user throughput, taking into account the users of poor channel quality and the users of better channel quality,better weighing cell throughput and user fairness. LTE system-level simulation results show that the proposed multicast scheduling algorithm’s correctness and feasibility.To further improve the cell throughput and user fairness, this paper introduces the idea of two-stage cooperative multicast, and analyses various embodiments of two-stage cooperative multicast scheduling algorithms under LTE network systematically, from different levels. Considering the differences in user channel quality and the characteristics of base station’s multiple data transmission, this paper concludes with one cooperative multicast mechanism based on Non-orthogonal Multiple Access(NOMA). By introducing successive interference cancellationtechnology and network coding technology, base station and users achieve joint processing on data signals. By adjusting the scheduling period to four slots, during each slot, base station cooperate the relay users, making cell center users and cell edge users share data signals transmitted from base station, improving cell edge users’ throughput of poor channel quality and user fairness within the cell.To assess the performance of the proposed algorithm, this paper analyses the comparison simulation with the traditional multicast scheduling algorithm and cooperative multicast scheduling algorithm based on hierarchical coding, from three aspects of throughput, fairness, spectrum efficiency. System-level simulation shows that NOMA-based cooperative multicast scheduling scheme all increased substantially compared with the other two algorithms, in terms of throughput,spectrum efficiency, whose fairness is also higher than cooperative multicast scheduling algorithm based on hierarchical coding. Therefore, NOMA-based cooperative multicast scheduling mechanism has greater development prospects and is easy implemented in the field of the future wireless communications.