Interface placement in constructing widest spanning tree for multi-channel multi-interface wireless mesh networks

Proceedings of the IEEE Wireless Communications and Networking Conference, 2009, p. 2560-2564Widest spanning tree is a broadcast tree with its bottleneck link bandwidth maximized. It provides a cost effective broadcasting solution in multi-channel multi-interface wireless mesh networks. To find the widest spanning tree, existing algorithms jointly consider channel assignment, routing and scheduling while assuming the number of network interface cards (NICs) at each node is given. In this paper, we treat the number of NICs at each node as a design parameter, whereas the total number of NICs in the system is given. By properly placing more NICs to more "critical" nodes, the bandwidth of the spanning tree can be further increased. To this end, a new Integer Linear Programming (ILP) is formulated for solving the widest spanning tree problem based on joint optimization of interface placement, channel assignment, routing and scheduling. Numerical results show that interface placement provides a significant boost to the bandwidth of the widest spanning tree found. © 2009 IEEE.published_or_final_versio

Bandwidth-guaranteed multicast in multi-channel multi-interface wireless mesh networks

Proceedings of the IEEE International Conference on Communications, 2009, p. 1-5We consider multi-channel multi-interface wireless mesh networks with a schedule-based MAC protocol, where conflict-free transmission is ensured by requiring links assigned with the same channel and within the mutual interference range of each other to be active at different time slots. When a (point-to-multipoint) multicast call arrives, the call is accepted if a multicast distribution tree can be established for connecting the source node with all the receiving nodes, and with sufficient bandwidth reserved on each link. Otherwise, the call is rejected. To maximize the call acceptance rate, the multicast tree must be constructed judiciously upon each call arrival. Aiming at minimizing the carried load on the most-heavily loaded channel, and maximizing the residual capacity of the most heavily loaded node, an integer linear program (ILP) is formulated for multicast tree construction. Since solving ILP can be time-consuming, an efficient heuristic algorithm is then proposed. We compare the two tree construction algorithms by simulations. We found that both algorithms give comparable call acceptance rate, but the heuristic algorithm requires much shorter running time. ©2009 IEEE.published_or_final_versio

J-CAR: An efficient channel assignment and routing protocol for multi-channel multi-interface mobile ad hoc networks

In Session: Wireless Ad Hoc and Sensor Networks towards Anytime Anywhere Internetworking: WSN-15: Resource Allocation: article no. WSN15-2We propose an efficient joint channel assignment and routing protocol (J-CAR) for multi-channel multi-interface mobile ad hoc networks (MANETs). Aiming at overcoming the limitations of the existing channel assignment and routing algorithms, J-CAR negotiates a channel at each active link during the route setup process. It has the following major features: a) a pre-determined common control channel is used by every node for routing and channel negotiation; b) control packets for data transmission (RTS, CTS & ACK) are carried by the associated data channels; c) the spare capacity on the control channel can be used for data transmission; d) an interface is free to change its working modes between send and receive; and e) an interface can tune to any data channels for data sending or receiving at the cost of switching overhead. With J-CAR, a more flexible assignment of interfaces, channels, and the working mode of each interface can be rendered. The performance gain brought by J-CAR is substantiated by extensive simulation results. © 2006 IEEE.published_or_final_versionProceedings of the Global Telecommunications Conference, 2006 (GLOBECOM 2006), San Francisco, CA, USA, 27 November - 1 December 200

BGP ingress-to-egress route configuration in a capacity-constrained AS

The BGP ingress-to-egress route configuration problem is to find a set of paths in an ISP to carry the transit flows, such that the amount of network resources consumed is minimized without violating the bandwidth constraint on all network links. To solve the problem, we first formulate it using Integer Linear Programming (ILP). Due to the high complexity involved in ILP, a heuristic algorithm, called MPPF, is then proposed. MPPF is designed based on the idea that heavily-loaded destination prefixes should be given higher priority to select less expensive edge links and routes. Simulation results show that MPPF requires less network resources and edge link capacity than an alternative heuristic called BTF. © 2005 IEEE.published_or_final_versio

Interface placement in constructing widest spanning tree for multi-channel multi-interface wireless mesh networks

Proceedings of the IEEE Wireless Communications and Networking Conference, 2009, p. 2560-2564Widest spanning tree is a broadcast tree with its bottleneck link bandwidth maximized. It provides a cost effective broadcasting solution in multi-channel multi-interface wireless mesh networks. To find the widest spanning tree, existing algorithms jointly consider channel assignment, routing and scheduling while assuming the number of network interface cards (NICs) at each node is given. In this paper, we treat the number of NICs at each node as a design parameter, whereas the total number of NICs in the system is given. By properly placing more NICs to more "critical" nodes, the bandwidth of the spanning tree can be further increased. To this end, a new Integer Linear Programming (ILP) is formulated for solving the widest spanning tree problem based on joint optimization of interface placement, channel assignment, routing and scheduling. Numerical results show that interface placement provides a significant boost to the bandwidth of the widest spanning tree found. © 2009 IEEE.published_or_final_versio

Performance of a prehospital trauma diversion system in Hong Kong, China

postprin

BGP ingress-to-egress route configuration in a capacity-constrained AS

The BGP ingress-to-egress route configuration problem is to find a set of paths in an ISP to carry the transit flows, such that the amount of network resources consumed is minimized without violating the bandwidth constraint on all network links. To solve the problem, we first formulate it using Integer Linear Programming (ILP). Due to the high complexity involved in ILP, a heuristic algorithm, called MPPF, is then proposed. MPPF is designed based on the idea that heavily-loaded destination prefixes should be given higher priority to select less expensive edge links and routes. Simulation results show that MPPF requires less network resources and edge link capacity than an alternative heuristic called BTF. © 2005 IEEE.published_or_final_versio

Routing algorithm for provisioning symmetric virtual private networks in the hose model

A virtual private network (VPN) is a private data network where remote sites are connected over a shared provider network. In order to provide secure communications between customer sites, predetermined paths are used to forward data packets. To support quality of service (QoS), bandwidth has to be reserved on these paths. Then, finding appropriate paths in order to optimize the bandwidth used becomes an important problem. In this paper, we study the routing problem of VPNs under the hose model, where VPN endpoints specify the maximum bandwidth they need in sending and receiving data. Some previous works considered the problem under the assumption that all links have infinite capacities. We remove this constraint in our studies and develop enhancement to existing algorithms. Our simulation results show that our algorithm works very well in networks where link capacities are tight. © 2005 IEEE.published_or_final_versio

A new ILP-based p-cycle construction algorithm without candidate cycle enumeration

The notion of p-cycle (Preconfigured Protection Cycle) allows capacity efficient schemes to be designed for fast span protection in WDM mesh networks. Conventional p-cycle construction algorithms need to enumerate/pre-select candidate cycles before ILP (Integer Linear Program) can be applied. In this paper, we propose a new algorithm which is only based on ILP. When the required number of p-cycles is not too large, our ILP can generate optimal/suboptimal solutions in reasonable amount of running time. © 2007 IEEE.published_or_final_versio

Building smart cameras on mobile tablets for hand gesture recognition

Mobile tablets have become very popular due to their portability and the wide diversity of the applications available. The touch screens and built-in accelerometers facilitate different forms of input instead of keyboards and mice. Nowadays, high-resolution cameras become a standard feature in a mobile device. Nevertheless, this camera is seldom considered to serve as a form of user inputs to the application, although similar technology is realized in some home entertainment systems. This paper describes our experience on making a smart camera on an iPad that can recognize pre-defined hand gestures. We study the time performance of performing image processing on an iPad. We find that due to the limited computational power of the mobile device, recognition results may not be available fast enough for a real-time application. We explore applying cloud computing to solve the problem. To the best of our knowledge, this is the first study on recognizing hand gestures on an iPad. Our results facilitate the development of a brand new type of applications that require smart cameras. © 2012 ACM.published_or_final_versio