Research On Efficient Utilization Technology Of Dynamic Spectrum In Cellular And Terminal Hybrid Network

With the development of wireless communication technology, the wireless network environment becomes increasingly complex, thus the concept of the hybrid network is proposed to define the scenario in which the traditional cellular networks and device-to-device (D2D) communication are coexist. The significance of studying this scenario is:in the aspect of theory, spectrum reuse can effectively improve the spectrum utilization, especially when the spectrum resources continue to decrease; in the aspect of practical applications, the scenario can satisfy the requirement of the operators, the reduction of the link between the terminals and the base station can not only reduce the inter-link interference, but also decrease the repeated transition of the same data packet, thereby improve spectrum utilization as well.This paper is intended to improve the utilization of dynamic wireless spectrum resources in mixed cellular and D2D network. The technology of spectrum detection in hybrid network, the base station assisted semi-centralized spectrum sharing technology, and the distributed resources scheduling which joint with terminal spectrum accessing and power controlling, are the three aspects proposed in the paper from which we can enhance the overall performance of the hybrid network. In this paper, some researches have been done to select an optimal decision threshold in broadband-based energy detection. Then according to the scenario of spectrum resources sharing in hybrid network, with the assisted of base station, an optimal resource allocation scheme has been proposed which can guarantee the fairness of different terminal users. At last, a new distributed resources scheduling which include terminal spectrum access and power controlling is designed for D2D terminal users.The main innovations of the paper are as follows:1. The spectrum sensing technology for D2D users to get spectrum resources in hybrid network has been studied in the paper. At first, for the broadband signals, based on the false alarm probability threshold and detection probability threshold, the closed-form solution of the minimum-cost decision threshold can be got by using the minimum cost function, and the restriction which comes from performance index to the decision threshold of energy detection can be analyzed in constraint of detection performance. Then, by taking advantage of the relationship between the length of observation time and the decision threshold of energy detection, a criterion about selecting an optimal decision threshold has been proposed. At last, by using the method of data simulation and analyzing the detection performance whose observation time is sectioned, the optimality of the criterion can be verified.2. An uplink spectrum resource sharing scheme for cellular and D2D users in hybrid network has been studied in the paper, and with the assisted of the base station, a scheme about spectrum resources and power allocation for different users has been implemented. At first, the resource allocation problem is modeled as an optimization problem with the object of maximizing the data rate of terminal users (including cellular and D2D terminal users), which has the constraint that the data rate requirements for the D2D users should be guaranteed in order to implement the proportional fairness scheduling for both terminal users. Then, by using the Lagrange multiplier method and KKT condition, the above problem can be resolved, and we can get the conclusion that:the relationship between the spectrum resource selection and power allocation of terminal users is a mutually conditional selection problem. At last, according to the above conclusion, the detail algorithm of the scheme is proposed in this paper, in addition with the data rate performance and the fairness verification of it.3. After the spectrum sensing information is obtained by D2D terminal users, the affection of the uplink spectrum self-accessing and power self-control for the D2D users to the performance of the hybrid network has been studied in this paper. At first, the resources allocation problem is modeled as an optimization problem about maximizing the throughput for all the D2D users, and the optimal problem is resolved upon two primary factors:maximize the total throughput and maximize the number of D2D link accessing. Then, two kinds of distributed spectrum access strategy have been given out, and according to the access sequence of a D2D link, the distributed spectrum resource allocation scheme has been proposed. At last, in order to illustrate its effectiveness, the comparison results between the performances of proposed scheduling strategy and centralized scheduling strategy has been given in this paper.