Study On Relative Theories And Key Technologies Of Quality Of Service For Networks In Manufacturing

Nowadays, networking has been adopted in a variety of industrial fields. In particular, in manufacturing industry, the move towards networking has become a notable trend. Manufacturing networks can be regarded as integrating communication networks and networked resource service management using novel manufacturing models, such as Manufacturing Grid or Cloud Enterprise. Therefore, resolving Quality of Service (QoS) issues is important for manufacturing networks, not only to guarantee the performance of communication networks, but also to achieve effective management of various manufacturing resources. Without such effective QoS mechanisms, system performance will degrade and the manufacturing resources may become unusable. Aiming at the aforementioned problems, the thesis focuses on the relative theories and key technologies of QoS assurance for networks in manufacturing. The main contributions of the thesis are:(1) The concept of QoS for manufacturing networks is discussed, and the related QoS model is established. In order to provide overall performance assurance for manufacturing networks, a service framework integrating the QoS mechanisms of the networked resource service management function and the communication networks is proposed. The novel framework maps an application to resource services and then to communication networks, adopts an intelligent optimisation algorithm for QoS management of resource services,and provides QoS schemes for data transfer across communication networks.The communication network infrastructure in manufacturing networks is responsible for the data transfer and exchange in the system, and therefore it is the basis supporting the operation the networked resource service management. In the following content, the thesis mainly focuses on the network QoS issues in manufacturing networks, and to develop the key technologies in order to provide QoS assurance for the network infrastructure.(2).One-way delay estimation in the forward and feedback channels is crucial for a networked control system (NCS) due to its important role in the reliability and availability design. The problems existing in current one-way delay estimation schemes are investigated. Then, a novel hybrid one-way delay estimation scheme, utilizing the hybrid technique that contains an online monitoring mechanism and an end-to-end estimation method, is proposed to overcome the effects of network asymmetry and delay dynamics in the NCS. In the proposed scheme, only the delay value of the initial packet starting the control loop of the NCS is estimated by the online monitoring mechanism, all the other estimations are performed by the host using the end-to-end method, so as to achieve high accuracy in tracking delay values as well as requiring lower computation complexity of the system.(3) In the high-speed network infrastructure of manufacturing networks, the real-time traffic of multimedia applications can congest the network and result in unfairness and throughput degradation of Transmission Control Protocol (TCP) traffic, in terms of there is no control mechanism in User Datagram Protocol (UDP). In order to improve the QoS performance of the network infrastructure, a new unreliable transport protocol, FAST DCCP, is presented for the real-time traffic in high-speed networks. FAST DCCP is based on the DCCP protocol and adopts the FAST scheme to realize congestion control. Some modifications have been made to the mechanisms inherited from DCCP so as to let the proposed protocol can efficiently operate under a large size window. In addition, an enhanced protocol, EEFAST DCCP, using the measurements of one-way delay to dynamically adjust the window size is also proposed to improve the throughput of FAST DCCP with the effect of reverse traffic.(4) Although several high-speed TCP variants perform successfully to improve the bandwidth utilization of high-speed network, they still have the weakness on the performance such as RTT-fairness, TCP-friendliness, etc. A hybrid congestion control algorithm, HCC TCP, using the synergy of delay-based-and loss-based approach is proposed for the adaptation to high speed and long distance network environments. The algorithm uses queuing delay as the primary congestion indicator, and adjusts the window to stabilize around the size which can achieve the full utilization of available bandwidth. On the other hand, it uses packet loss as the second congestion indicator, and a loss-based congestion control strategy is utilized to maintain high bandwidth utilization in the cases that the delay-based strategy performs inefficiently in the networks. The two approaches in the algorithm are dynamically transferred into each other according to the network status.(5) Facing the the challenges for future SMEs in manufacturing, the thesis presents an innovative network environment, together with its architecture and methodologies, to support the development of Future Internet based Enterprise Systems for the SMEs, in order to achieve the goals of high operation efficiency and sustainable value creation. A list of related EC FP7 projects focusing on the networked enterprise domain and their characterization are introduced, analyzed, and compared. Finally some research issues and future works are given.