Intermediate-Level Protocols to Provide Quality of Service in Master/Slave Communication Infrastructures
Ref: HURRAY-TR-090204 Publication Date: 16, Feb, 2009
Intermediate-Level Protocols to Provide Quality of Service in Master/Slave Communication InfrastructuresRef: HURRAY-TR-090204 Publication Date: 16, Feb, 2009
Industrial communication networks have suffered a dramatic change over the last decades. There has been a proliferation of “traditional” fieldbuses and other more application-specific networks, such as the ones relying on power-line communications. Industrial Ethernet solutions have gained a significant market share too. Due to the stringent quality-of-service (QoS) requirements of industrial monitoring and control applications, most of the protocols for this type of applications rely on a master/slave paradigm where one or more master stations control the access to the communication medium, granting medium access to slave stations. This Thesis was developed in synergy with the RFieldbus and REMPLI European Union projects. Although operating at opposite network scales, they share one main characteristic: a master/slave network was enhanced with communication features previously unavailable. In the context of the RFieldbus framework, a standard fieldbus network was extended to support multimedia services and wireless/mobility capabilities. These multimedia services run over the TCP/IP stack that in turn runs over the fieldbus low layers network protocols. Since these multimedia services and the “traditional” control traffic converge in the use of the same communication medium, appropriate admission control and scheduling mechanisms were conceived to introduce different traffic classes; in such a way, that real-time control traffic is not affected by multimedia traffic, which in some cases is typically of best-effort type. The REMPLI approach is based on a power-line communication protocol that was enhanced with additional capabilities such as the ability of supporting large-scale deployments - both in terms of number of network stations and in terms of geographical area under coverage - and new metering-focused end-to-end services. This required a rethinking of the Data Link, Network and Transport Layer protocols in a cross-layered perspective that had end-to-end QoS requirements in mind. The initial hypothesis was that providing add-ons to existing protocols to achieve the required level of QoS and additional functionalities would present major advantages over all-new network protocols or using stripped-down versions of existing network protocols. This hypothesis is confirmed through experimental and simulation validations.
PhD Thesis, Faculdade de Engenharia da Universidade do Porto.