958 research outputs found
To mesh or not to mesh: flexible wireless indoor communication among mobile robots in industrial environments
Mobile robots such as automated guided vehicles become increasingly important in industry as they can greatly increase efficiency. For their operation such robots must rely on wireless communication, typically realized by connecting them to an existing enterprise network. In this paper we motivate that such an approach is not always economically viable or might result in performance issues. Therefore we propose a flexible and configurable mixed architecture that leverages on mesh capabilities whenever appropriate. Through experiments on a wireless testbed for a variety of scenarios, we analyse the impact of roaming, mobility and traffic separation and demonstrate the potential of our approach
The Balanced Unicast and Multicast Capacity Regions of Large Wireless Networks
We consider the question of determining the scaling of the -dimensional
balanced unicast and the -dimensional balanced multicast capacity
regions of a wireless network with nodes placed uniformly at random in a
square region of area and communicating over Gaussian fading channels. We
identify this scaling of both the balanced unicast and multicast capacity
regions in terms of , out of total possible, cuts. These cuts
only depend on the geometry of the locations of the source nodes and their
destination nodes and the traffic demands between them, and thus can be readily
evaluated. Our results are constructive and provide optimal (in the scaling
sense) communication schemes.Comment: 37 pages, 7 figures, to appear in IEEE Transactions on Information
Theor
A Novel Approach to Reduce the Unicast Bandwidth of an IPTV System in a High-Speed Access Network
Channel change time is a critical quality of experience (QOE) metric for IP-based video delivery systems such as Internet Protocol Television (IPTV). An interesting channel change acceleration scheme based on peer-assisted delivery was recently proposed, which consists of deploying one FCC server (Fast Channel Change Server) in the IP backbone in order to send the unicast stream to the STB (Set-Top Box) before sending the normal multicast stream after each channel change. However, deploying such a solution will cause high bandwidth usage in the network because of the huge unicast traffic sent by the FCC server to the STBs. In this paper, we propose a new solution to reduce the bandwidth occupancy of the unicast traffic, by deploying the FCC server capabilities on the user STB. This means that, after each channel change request, the STB will receive the unicast traffic from another STB instead of the central server. By using this method, the unicast traffic will not pass through the IP network; it will be a peer-to-peer communication via the Access Network only. Extensive simulation results are presented to demonstrate the robustness of our new solution
Network Coding for Speedup in Switches
We present a graph theoretic upper bound on speedup needed to achieve 100%
throughput in a multicast switch using network coding. By bounding speedup, we
show the equivalence between network coding and speedup in multicast switches -
i.e. network coding, which is usually implemented using software, can in many
cases substitute speedup, which is often achieved by adding extra switch
fabrics. This bound is based on an approach to network coding problems called
the "enhanced conflict graph". We show that the "imperfection ratio" of the
enhanced conflict graph gives an upper bound on speedup. In particular, we
apply this result to K-by-N switches with traffic patterns consisting of
unicasts and broadcasts only to obtain an upper bound of min{(2K-1)/K,
2N/(N+1)}.Comment: 5 pages, 4 figures, IEEE ISIT 200
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