The QoS Guarantee Mechanism For Smart Distribution Grid Communication Networks

The smart distribution grid communication network is a key component of smart grid communication networks. It mainly affords distribution automation, distribution operation monitoring, distributed generation, charging pile, load management, power consumption data acquisition and other services. It is also the key point of assuring power supply reliability, improving grid efficiency and service quality. After years of construction,smart distribution grid communication network has become a heterogeneous network formed by optical fiber communication networks, power line communication networks, private wireless networks,public wireless networks, wireless sensor networks, and etc. With the rapid development of smart distribution grid, the amount of smart distribution grid communication network services increases. Moreover,these heterogeneous services have strong heterogeneity, and have significant differences in QoS requirements. However, the traditional service management methods realized by artificial distinction are difficult to satisfy the QoS requirements of services with high bandwidth and burstiness, which may affect delivery rate and real-timeness, as well as lower the network utility. Therefore, it has great significance to better use the limited network resources and design suitable QoS guarantee mechanisms to provide end-to-end and hierarchically high QoS service for smart distribution grid communication network services.This paper analyzes the differentiated QoS requirements according to smart grid structure and service characteristics, and studies QoS guarantee mechanisms within three scenarios from single to multiple communication network technologies. These scenarios include the cognitive sensor network, the private wireless network, and the heterogeneous access network. In summary, for optimizing network operation, improving economic efficiency and comprehensive service capabilities, this paper studies QoS guarantee mechanisms including a priority-based packet scheduling mechanism in single-hop cognitive sensor networks, a QoS-based traffic scheduling mechanism in multi-hop cognitive sensor networks, a profit-based virtual resource allocation mechanism in virtual wireless networks, and a cost-aimed traffic allocation mechanism in heterogeneous access networks respectively. The detailed researches in this paper are as follows.(1) In the scenario of single-hop cognitive sensor networks, a QoS-based priority classification model and a priority-based packet scheduling mechanism are presented in this paper. The transmission delay,delivery rate, reliability and the degree of importance are comprehensively considered in the service priority classification model.Besides, the model is built with dynamic adjustment capability in order to adapt to the real-time congestion state of the network. Furthermore,combining service priority classification model and channel quality evaluation model, a priority-based packet scheduling mechanism in cognitive radio networks for smart grid is presented to provide differentiated service. Simulation results show that, the proposed mechanism can guarantee the transmission quality for the secondary user with relatively high priorities, and increase the whole system's utilization without introducing interference to primary users.(2) In the scenario of multi-hop cognitive sensor networks, a QoS-based traffic scheduling mechanism is proposed for jointly optimizing QoS indicators in terms of delay, delivery rate and reliability.First, the traffic scheduling optimization model is constructed based on Lyapunov theory, which sets the optimal system utilization as the objective and the QoS requirements as constraints. Then, the distributed QoS routing method is adopted into the QoS-based traffic scheduling mechanism to solve the optimization problem. Through three steps -channel access control, traffic admission control and transmission path control, the effects of different transmission channels, single-hop transmission rates and transmission path delays of the system areexamined. Simulation results show that, the proposed mechanism can satisfy the QoS requirements and optimize the weighted system utilization.(3) In the scenario of private wireless networks, a profit-based virtual resource allocation mechanism is designed for power grid private networks (i.e. TD 230MHz and TD 1.8GHz) to guarantee the isolation and QoS of smart grid services. According to the characteristics of electric power wireless networks, a virtualization system model is constructed to abstract and share physical wireless resources firstly. And then, the network cost, profit, service isolation constraints, backhaul bandwidth constraints, QoS constraints and other factors are integrated into a resource allocation optimization problem model. Finally, a tabu search algorithm is applyed to optimize virtual resource allocation.Simulation results show that, the proposed mechanism can support QoS and isolation requirements, as well as improve economic benefits of the network.(4) In the scenario of heterogeneous access networks, a traffic allocation optimization mechanism is proposed to ensure QoS and save economic cost on the basis of the heterogeneity of access technologies and corresponding services. Setting optimal cost as the objective function,traffic QoS requirements as restrictions, a heterogeneous network traffic allocation optimization model is established. It is solved by traffic transition control and service rate control in order to dynamically and distributedly allocate network traffic to appropriate output networks.Simulation results show that, by applying the proposed mechanism, the network economic cost is reduced and the QoS constraints of heterogeneous services are satisfied at the same time.