Recent researches show that inter-session network coding could decrease the number of packets transmission and achieve higher throughput in wireless network compared with traditional forwarding mechanism. In most exis...
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Recent researches show that inter-session network coding could decrease the number of packets transmission and achieve higher throughput in wireless network compared with traditional forwarding mechanism. In most existing relay mechanisms based on inter-sessionnetwork such as COPE, relay node demands to collect the messages from its neighbor nodes to get notice of which packets already overheard by them so as to determine whether there exists coding opportunity between or among forwarding packets. However, transmission overhead of this message collection and computing cost of opportunity determination will degrade the performance of these mechanisms. It is observed that coding opportunity at relay node is much more related with the local topology, and the opportunity of encoding three or more packets together is far less than that of encoding two packets together in wireless network with general density. Based on this, a new coding-aware routing mechanism, named TCAR, is proposed. TCAR ignores the oppommity of encoding three or more than three packets together. Each relay node maintains an encoding mapping table being established according to the result of its local topology detection, which can be used to calculate the path cost during routing setup phase, and determine that which two packets can be encoded together during the packets forwarding phase. In TCAR, instead of periodic messages collection, each relay nodes just need once local topology detection, and the encoding determination is much simpler than that of the former mechanisms. Simulation results show that compared with typical inter-session network coding mechanisms COPE and COPE-based routing, TCAR achieves 12% and 7% throughput gains, and keeps the minimum end to end delay.
In this study the authors consider the scenario of multiple unicast flows intersecting a common router in an opportunistic wireless network. Instead of forwarding packets in each of the flows independently, the router...
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In this study the authors consider the scenario of multiple unicast flows intersecting a common router in an opportunistic wireless network. Instead of forwarding packets in each of the flows independently, the router can perform inter-session network coding and transmit codewords to improve the network throughput. Unlike coding for multicast data flow for which an optimal code can be constructed in polynomial time, coding for unicast data flows is a more complicated coding problem and has been shown to be an NP-hard problem. Opportunities for inter-session network coding have also been shown to exist in single-hop wireless data dissemination network such as Wi-Fi and WiMAX networks. In this study the authors propose an efficient coding scheme for unicast flows and demonstrate its higher coding gain over previously proposed state-of-the-art coding schemes, validated using simulation results and wireless sensor network testbed packet reception traces. The authors also show that the proposed algorithm is optimal for all 238 non-isomorphic coding instances for instances for n 4, and for 9500 of the 9608 non-isomorphic coding instances for n = 5, where n is the number of unicast packets.
With the proliferation of multi-touch mobile devices, such as smartphones and tablets, users interact with devices in non-conventional gesture-intensive ways. As a new way to interact with mobile devices, gestures hav...
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With the proliferation of multi-touch mobile devices, such as smartphones and tablets, users interact with devices in non-conventional gesture-intensive ways. As a new way to interact with mobile devices, gestures have been proven to be intuitive and natural with a minimal learning curve, and can be used in interactive multimedia applications. In order for multiple users to collaborate in an interactive manner, we propose that gestures can be streamed in multiple broadcast sessions, with each session corresponding to one of the users as the source of a gesture stream. During the interactive session, the Quality of Experience (QoE) of mobile users hinges upon delays from when gestures are entered by the source to when they are recognized by each of the receivers, which we refer to as gesture recognizing delays. In this paper, we present the design of GestureFlow, a gesture broadcast protocol designed specifically for concurrent gesture streams in multiple broadcast sessions, such that the gesture recognizing delay in each session is minimized. We motivate the effectiveness and practicality of using inter-session network coding, and address challenges introduced by the linear dependence of coded packets. We evaluate our protocol design using an extensive array of real-world experiments on mobile devices, involving a new gesture-intensive interactive multimedia application, called MusicScore, that we developed from scratch.
We propose and study a new set of enhancement features to improve the performance of reliable transport in Delay Tolerant networks (DTNs) consisting of both unicast and multicast flows. The improvement in reliability ...
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We propose and study a new set of enhancement features to improve the performance of reliable transport in Delay Tolerant networks (DTNs) consisting of both unicast and multicast flows. The improvement in reliability is brought in by a novel Global Selective ACKnowledgment (G-SACK) scheme and random linear networkcoding. The motivation for using networkcoding and G-SACKs comes from the observation that one should take the maximum advantage of the contact opportunities which occur quite infrequently in DTNs. networkcoding and G-SACKs perform "mixing" of packet and acknowledgment information, respectively, at the contact opportunities and essentially solve the randomness and finite capacity limitations of DTNs. In contrast to earlier work on networkcoding in DTNs, we observe and explain the gains due to networkcoding even under an inter-session setting. Our results from extensive simulations of appropriately chosen "minimal" topologies quantify the gains due to each enhancement feature. We show that substantial gains can be achieved by our proposed enhancements that are very simple to implement. (C) 2013 Elsevier B.V. All rights reserved.
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