3369144
Adaptive Multi-Channel MAC Protocol for Dense VANET with Directional Antennas
Directional antennas can increase the spatial reuse of the wireless channels and reach a higher antenna gain. This paper presents the design, implementation and simulation results of a multi-channel medium access control protocols for high density vehicular ad hoc networks using directional antennas with local beam tables. Simulation shows that our protocol has a higher throughput than the existing multi-channel protocols.
694386
A Data Storage Mechanism for P2P VoD Based on Multi-channel Overlay
It is a big challenge to provide Video-on-Demand streaming services over Internet in a scalable way. Currently, many researchers use a single channel overlay to implement the scalability of on-demand streaming services. However, in a real application environment, various channels in a P2P VOD system have different popularities, which probably cause the imbalance of data storage-capability of the whole system. It results in a problem that a mass of unpopular channels' caching capability can not be used to satisfy the data requirements of the whole system. In order to solve the problem, this paper proposes a new data-storage mechanism, which constructs a multi-channel overlay to optimize the whole system's caching-capability and greatly improves unpopular channel's caching efficiency. The experimental results show that this mechanism can achieve significant effects.
18359442
General Approach for Simulating Heterogeneity of Car-Following Behaviors
This paper presents a general approach to simulate heterogeneity of car-following behaviors in freeway traffic. This is achieved by proposing a new car-following model called General Individual Based car-following Model (GIBM) which takes into account the characteristics of the individual driver. The model parameters are expressed as functions with regard to “aggressiveness level” of drivers. The numerical simulation of the perturbation propagation in dense traffic flow by using the GIBM shows that small perturbations could develop into stable moving jams, growing moving jam, and decaying moving jams randomly, due to the heterogeneity of individual car-following behaviors in traffic flow. The result of the simulation is consistent with the empirical observation. The GIBM appears promising for application to microscopic simulations of traffic dynamics including randomness. It presents a general approach to simulate the heterogeneity of car-following behaviors efficiently and simply.
10702245
A wireless LAN-based indoor positioning technology
Context-aware computing is an emerging computing paradigm that can provide new or improved services by exploiting user context information. In this paper, we present a wireless-local-area-network-based (WLAN-based) indoor positioning technology. The wireless device deploys a position-determination model to gather location information from collected WLAN signals. A model-based signal distribution training scheme is proposed to trade off the accuracy of signal distribution and training workload. A tracking-assistant positioning algorithm is presented to employ knowledge of the area topology to assist the procedure of position determination. We have set up a positioning system at the IBM China Research Laboratory. Our experimental results indicate an accuracy of 2 m with a 90% probability for static devices and, for moving (walking) devices, an accuracy of 5 m with a 90% probability. Moreover, the complexity of the training procedure is greatly reduced compared with other positioning algorithms.
29040872
A Variant to Turing's Theory of Computing Machines
The principal purpose of this paper is to offer a theory which is closely related to Turing's [1] but is more economical in the basic operations. I t will be proved that a theoretically simple basic machine can be imagined and specified such tha t all partial recursive functions (and hence all solvable computation problems) can be computed by it and tha t only four basic types of instruction are employed for the programs: shift left one space, shift right one space, mark a blank space, conditional transfer. In particular, erasing is dispensable, one symbol for marking is sufficient, and one kind of transfer is enough. The reduction is somewhat similar to the realization of, for instance, the definability of conjunction and implication in terms of negation and disjunction, or of the definability of all these in terms of Sheffer's stroke function. As a result, i t becomes less direct to prove that certain things can be done by the machines, but a little easier to prove that certain things cannot be done. This serf-contained theory will b e presented, as far as possible, in a language which is familiar to those who are engaged in the use and construction of largescale computers. Turing's theory of computable functions antedated but has not much influenced the extensive actual construction of digital computers. These two aspects of theory and practice have been developed almost entirely independently of each other. The main reason is undoubtedly that logicians are interested in questions radically different from those with which the applied mathematicians and electrical engineers are primarily concerned. I t cannot, however, fail to strike one as rather strange that often the same concepts are expressed by very different terms in the two developments. One is even inclined to ask whether a rapprochement might not produce some good effect. This paper wiU, it is believed, be of use to those who wish to compare and connect the two approaches. Extensive use of Turing [1] and Kleene [2] (Chapter XI I I ) will be made, although the exposition is sufficient in itself.
15916460
An approach to security and privacy of RFID system for supply chain
Radio frequency identification (RFID) is expected to become pervasive and ubiquitous, as it can be embedded into everyday items as smart labels. A typical scenario of exploiting RFID is supply chain. The RFID based supply chain management yields convenience, efficiency and productivity gains. However, RFID systems create new risks to security and privacy. We briefly present the current solutions to RFID security and privacy. A new approach is then proposed, which exploits randomized read access control and thus prevents hostile tracking and man-in-the-middle attack. In addition, compared with current schemes that achieve the similar security level, the proposed approach dramatically decreases the computation load. Another benefit is that it is suitable for RFID systems with a large number of tags
5494803
Wireless Network Dynamic Topology Routing Protocol Based on Aggregation Tree Model
As the scale of the network increases, especially wireless and mobile networks comes into fashion, the problem of network dynamic topology management turns into a focus topic in the network world. When network information changes, frequent route computing and network state updates can cause computing and traffic overhead, respectively. Therefore, minimum of influence to network structure has been identified as one of the key issues in designing dynamic network routing protocols. A novel protocol, which is based on Aggregation Tree Routing Model (ATRM) as well as an effective ball-and-string algorithm, is introduced in this paper which aims to minimize the alteration of network topology and to speed up the minimum cost route computation. This routing protocol is applicable to all kinds of networks, including Internet, ad hoc and wireless sensor networks. The simulations show that our protocol not only results in significantly lower overhead, but also gives high levels of dynamic network topology management performance while keeping practical.