14512108
MCMSDA: a multi-channel multi-sector directional antenna wireless LAN
Recently there is an increasing interest in using directional antennas and multi-channel for ad-hoc wireless networks. The two techniques can also be used for infrastructure local area networks. In this paper, we present the architecture and the MAC layer design for a multi-channel multi-sector directional antenna wireless local area network (MCMSDA WLAN). This paper has three key components. First, we describe the network architecture and propose a TDMA-based MAC layer. Second, we formulate the channel time allocation problem as an optimization problem and introduce a Lagrangian relaxation based load-balancing algorithm as a solution. The simulation study shows that the algorithm obtains good sub-optimal solution very quickly. Finally, we propose two methods to accelerate the load-balancing process further
11427190
Exploiting the IPID Field to Infer Network Path and End-System Characteristics
In both active and passive network Internet measurements, the IP packet has a number of important header fields that have played key roles in past measurement efforts, e.g., IP source/destination address, protocol, TTL, port, and sequence number/acknowledgment. The 16-bit identification field (IPID) has only recently been studied to determine what information it might yield for network measurement and performance characterization purposes. We explore several new uses of the IPID field, including how it can be used to infer: (a) the amount of internal (local) traffic generated by a server; (b) the number of servers in a large-scale, load-balanced server complex and; (c) the difference between one-way delays of two machines to a target computer. We illustrate and validate the use of these techniques through empirical measurement studies.
3017976
Publish/Subscribe Tree Construction in Wireless Ad-Hoc Networks
Wireless ad-hoc publish/subscribe systems combine a publish/subscribe mechanism with wireless ad-hoc networking. The combination, although very attractive, has not been studied extensively in the literature. This paper addresses an important problem of such systems: how to construct an optimal publish/ subscribe tree for routing information from the source to all interested recipients. First we precisely define the optimality of a publish/subscribe tree by developing a metric to evaluate its "efficiency." The optimality metric takes into account both the goal of a publish/subscribe system (i.e., to route a set of events), and the characteristics of an ad-hoc network (for example, devices are resource limited). We propose a greedy algorithm, SHOPPARENT, which builds the publish/ subscribe tree in a fully distributed fashion. A key feature is that this algorithm can be "subscription-aware", allowing it to use publication/subscription information in order to find a better outcome. Our simulations show that SHOPPARENT's performance is within 15% of optimal under normal configurations. We also study the effect of geographically localized subscriptions.
21281863
Practical key distribution schemes for channel protection
The paper presents three key distribution schemes for channel protection. With the proposed schemes, encryption keys of the ordered programs can be distributed to the authorized subscribers efficiently and securely. In these schemes, for key updates, at most two messages are transmitted and simpler computation functions, including one-way hash function and XOR operation, are used to reduce the computation cost compared to existing solutions. With our key distribution schemes, only the authorized subscribers can decrypt the ordered programs. Thus, the service provider in a Pay-TV system can charge his subscribers according to their subscriptions and the intelligent property rights of TV programs can be protected by the proposed schemes.
16574049
Feature Selection with Rough Sets for Web Page Classification
Web page classification is the problem of assigning predefined categories to web pages. A challenge in web page classification is how to deal with the high dimensionality of the feature space. We present a feature reduction method based on the rough set theory and investigate the effectiveness of the rough set feature selection method on web page classification. Our experiments indicate that rough set feature selection can improve the predictive performance when the original feature set for representing web pages is large.
52809014
Siphon-Based Deadlock Prevention Policy for Flexible Manufacturing Systems
A siphon-based algorithm for deadlock prevention of a type of Petri nets called S3PMR, which is a subclass of S3PGR2, is presented in this correspondence. The proposed method is an iterative approach by adding two kinds of control places called ordinary control (OC) places and weighted control (WC) places to the original model to prevent siphons from being unmarked. An OC place with ordinary arcs, which optimally prevent a siphon from becoming unmarked, is employed whenever it is possible, and otherwise, the WC places that adopt a conservative policy of controlling the release of parts into the system are used. Furthermore, this algorithm is not only for the subclass Petri nets but also for S3PR, ES 3PR, S2LSPR, and S3PGR2 nets. The authors prove the liveness and reversibility of the controlled net, and hence establish the correctness of the deadlock prevention policy. Finally, numerical experiments indicate that the proposed policy appears to be more permissive than closely related approaches in the literature
5254746
Low-power techniques for network security processors
In this paper, we present several techniques for low-power design, including a descriptor-based low-power scheduling algorithm, design of dynamic voltage generator, and dual threshold voltage assignments, for network security processors. The experiments show that the proposed methods and designs provide the opportunity for network security processors to achieve the goals of both high performance and low power.