| 1. |
- Cano, J., et al.
(författare)
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Scheduling feedback for scalability and reliability in a streaming multicast protocol
- 2015
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Ingår i: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS. - 9781479982448
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Konferensbidrag (refereegranskat)abstract
- The number of mobile devices accessing the Internet is continuously increasing, creating new problems. For example, when many wireless clients try to access the same video stream in the same hot spot, multicast transmission must be used. However, multicast packets are unacknowledged and may present a high loss rate under adverse conditions which may jeopardize the quality of the streaming. In a severe scenario, packet losses may affect all video frames, preventing the clients from receiving the video stream at all. Therefore, we propose a novel reliable multicast protocol, tailored to streaming applications, that also scales to many clients under the same access point. It uses a feedback repeat request mechanism per client and such requests are adequately scheduled by the streaming server. This mechanism, which is the focus of this paper, also allows differentiating the quality of service provided to the clients, polling their feedback independently. We show experimental and simulation results that confirm the desired scalability and reliable streaming, with efficient bandwidth usage. The results also show a clear superiority in mitigating lost packets with respect to other approaches to the same problem, with benefits reaching and even going beyond one order of magnitude in packets recovery.
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| 2. |
- Girs, Svetlana, et al.
(författare)
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Scheduling Transmissions in Industrial Networks Using Source Relaying and Packet Aggregation
- 2015
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Ingår i: 2015 IEEE World Conference on Factory Communication Systems (WFCS). - Piscataway, NJ : IEEE. - 9781479982448 ; , s. 1855-1864
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Konferensbidrag (refereegranskat)abstract
- Wireless networks present a promising alternative to the currently used wired systems as they are more flexible, easier to install and maintain. However, requirements on reliability and timeliness which at present are met by wired networks, also need be fulfilled by wireless solutions. Relaying and packet aggregation have been recognised as viable tools to do this. However, introducing additional relay nodes into an industrial network is costly. Hence, in this paper we propose to use a combination of relaying and packet aggregation performed by the source nodes themselves. The results show that our proposal improves performance considerably, but also that the transmission schedule plays a crucial role. A schedule adapting to the varying channel conditions, improves the performance substantially. By carefully choosing which packet to aggregate, even further improvements can be achieved. © 2015 IEEE.
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| 3. |
- Gutiérrez, Marina, et al.
(författare)
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A Configuration Agent based on the Time Triggered Paradigm for Real-Time Networks
- 2015
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Ingår i: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS. - 9781479982448
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Konferensbidrag (refereegranskat)abstract
- Distributed cyber-physical systems are growing in size and functionality and deterministic communication is an important requirement for those systems. The existing solutions based on the time-triggered paradigm pose certain limitations in regards to the configuration. Usually configuration is seen as a one-time event during the installation of the network. Future realtime networks need to be able to adapt more easily to changes in the network. Thus, the configuration becomes an ongoing service, e.g., as for network maintenance and re-configuration to add and remove new, respectively old, equipment. We postulate that configuration will emerge to a continued service that accompanies a real-time network throughout its different life-cycle phases. In this context of evolving and dynamic networks, we introduce the concept of a configuration agent for real-time networks and demonstrate the concept by a realization based on the time triggered paradigm.
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| 4. |
- Oliveira, L., et al.
(författare)
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Multi-hop routing within TDMA slots for teams of cooperating robots
- 2015
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Ingår i: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS. - 9781479982448
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Konferensbidrag (refereegranskat)abstract
- Small teams of cooperating robots have been shown to benefit from the increased reliability of synchronised message exchanges provided by TDMA-based schemes. However, such schemes may also impose a long propagation delay to communications between non neighbour robots. Such negative impact is further increased by long TDMA rounds, which favour reduced medium utilisation and energy consumption, and by decentralised mesh topologies, which increase the team coverage and layout flexibility. For small size teams, say up to 10 units, it is feasible to set-up a global TDMA framework as well as tracking the instantaneous network topology, making it available to each robot. In this work we use this knowledge to forward packets along their path within each TDMA slot. To that end, we present a novel communication protocol that combines global TDMA and multi-hop routing. It maintains the reliability benefits of the TDMA schemes while strongly reducing the end-to-end propagation delay of interactions between non neighbour robots. We validate our protocol with simulation results using OMNET++. In a worst-case topology scenario we achieved an end-to-end delay that can be as low as 35% that of a traditional TDMA implementation that forwards the packets to the immediate one-hop neighbours, only. In a concrete audio streaming application scenario reported in the literature for an alternative real-time token-passing protocol, our proposal achieves similar delays with significantly less management bandwidth.
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