29269446
A Novel Optimal Channel Partitioning Algorithm for Integrated Wireless and Mobile Networks
How to efficiently support multi-class services is a very important issue in integrated wireless and mobile networks because each type of services has distinct characteristics and quality of service (QoS) requirements. This paper presents an efficient algorithm for near optimal channel allocation when different types of services are to be provided in the next generation integrated wireless and mobile networks. We specifically propose a preemptive priority scheme for an integrated wireless and mobile network by first dividing channels into three independent groups and classifying traffic into four different types. The proposed system is modeled by a multi-dimension Markov chain model. Then such a model is used to obtain a set of relations that correlate performances with various system parameters. A novel recursive algorithm is developed to determine the minimal number of channels in each channel group that would be necessary to satisfy the QoS requirements. We also investigate the impact of load ratio for different types of traffic on channel assignment. Finally, we discuss some limitations of our approach and indicate possible future work. We believe that the partitioning scheme proposed in this paper can become a starting point for analysis of future integrated wireless and mobile networks.
5450203
Guest Editors' Introduction: Challenges in Designing Fault-Tolerant Routing in Networks
+I INRE arc several means nf intercomiecting the compoT nents of a computer system. Components can be connccted through direct or indirect connections. In a direct network, channels directly connect each processor. Neighboring nodes communicate with each other by scnding messages across the channcls. In an indirect network, processors are cnnnccted through switches and/or buses. Depending on how components are connected, we have bus-based networks, router-based networks, switcli-bascd networks, and cluster-based (hybrid of the other thrce networks) nctworks. Nctworks can also be classified bascd on topologies, which cau be either replnr or irregulnr. Anothcr classification is based on applications-there are local arca networks (LANs), networks of workstations (NOWs), multiprocessors, and mobilc networks. In a computer network, the efficiency of a routing process is critical to the system performance. A routing process deals with moving data between processors in a given network. When a routing process involves oiic source and onc destination, it is called unicnst or poirit-lopoint communication. When such a proccss involves more than one source and/or one destination, it is called a collective comrnlrnicntion process. Examples of collective communication include iirulticnst (one-to-many, one source and many destinations), brundcnst (one-to-all), and gossip (all-to-all).
206414100
Parameters for System Effectiveness Evaluation of Distributed Systems
In a Distributed Computing System (DCS), the failure of one or more system components causes the degradation in its effectiveness to complete a given task as opposed to a complete network breakdown. This paper addresses the issue of degraded system effectiveness evaluation by introducing two static measures, namely, Distributed Program Performance Index (DPPI) and Distributed System Performance Index (DSPI). These metrics can be used to compare networks with different features for application execution. It can be used to determine if the network with high reliability and low capacity, or low reliability and high capacity is better for a given program execution. An algorithm is also developed for computing these indices, and it is shown to be not only efficient, but general enough to compute many other existing measures such as computer networks, distributed systems, transaction based systems, etc.
22890668
Arithmetic Algorithms in a Negative Base
Algorithms are described for the basic arithmetic operations in a negative base. These algorithms are simpler, faster, and more general than those proposed by Sankar et al.
26743853
Design and Analysis of a Class of Highly Scalable Hierarchical Networks: PdBCube
Abstract A class of hierarchical networks called the dBCube, that provides cost-effective and high-performance communication in large multicomputer systems, has recently been introduced. Such a compound graph of a hypercube and a de Bruijn (dB) graph utilizes every node of the hypercube as a gateway for intercluster communication. This paper presents a partially connected dBCube subclass (PdBCube), wherein the use of fewer nodes as gateways makes the PdBCube highly scalable in terms of both the hypercube and the dB size. This enhancement in scalability can be achieved by two different approaches to assigning gateways. Performance degradation of the proposed PdBCube is illustrated in terms of diameter and average distance. Improvement in track efficiency and reduction in cost are observed to be directly related to a decrease in the number of remote links.
8619939
Comments on "A Note on Base -2 Arithmetic Logic"
Recently, Yuen1 has given simple methods for positive-negative base conversion. This correspondence presents a straightforward and complete proof for his algorithmetic steps. A few comments on the choice of negabinary adders with positive twin carries and with positive and negative carries have also been added.
40935363
Beacon Signals: What, Why, How, and Where?
Beacons are primarily radio, ultrasonic, optical, laser or other types of signals that indicate the proximity or location of a device or its readiness to perform a task. Beacon signals also carry several critical, constantly changing parameters, such as power-supply information, relative address, location, timestamp, signal strength, available bandwidth resources, temperature and pressure. Although transparent to the user community, beacon signals have made wireless systems more intelligent and human-like. They are an integral part of numerous scientific and commercial applications, ranging from mobile networks to search-and-rescue operations and location-tracking systems. Beacon signals help synchronize, coordinate and manage electronic resources using miniscule bandwidth. Researchers continue to improve their functionality by increasing signal coverage while optimizing energy consumption. Beacon signals' imperceptibility and usefulness in minimizing communication delays and interference are spurring exploratory efforts in many domains, ranging from the home to outer space.
32826804
Generalized minimum distance decoding in Euclidean space: Performance analysis
We present a detailed analysis of generalized minimum distance (GMD) decoding algorithms for Euclidean space codes. In particular, we completely characterize GMD decoding regions in terms of receiver front-end properties. This characterization is used to show that GMD decoding regions have intricate geometry. We prove that although these decoding regions are polyhedral, they are essentially always nonconvex. We furthermore show that conventional performance parameters, such as error-correction radius and effective error coefficient, do not capture the essential geometric features of a GMD decoding region, and thus do not provide a meaningful measure of performance. As an alternative, probabilistic estimates of, and upper bounds upon, the performance of GMD decoding are developed. Furthermore, extensive simulation results, for both low-dimensional and high-dimensional sphere-packings, are presented. These simulations show that multilevel codes in conjunction with multistage GMD decoding provide significant coding gains at a very low complexity. Simulated performance, in both cases, is in remarkably close agreement with our probabilistic approximations.
2759775
Distributed channel management in uncoordinated wireless environments
Wireless 802.11 hotspots have grown in an uncoordinated fashion with highly variable deployment densities. Such uncoordinated deployments, coupled with the difficulty of implementing coordination protocols, has often led to conflicting configurations (e.g., in choice of transmission power and channel of operation) among the corresponding Access Points (APs). Overall, such conflicts cause both unpredictable network performance and unfairness among clients of neighboring hotspots. In this paper, we focus on the fairness problem for uncoordinated deployments. We study this problem from the channel assignment perspective. Our solution is based on the notion of channel-hopping, and meets all the important design considerations for control methods in uncoordinated deployments - distributed in nature, minimal to zero coordination among APs belonging to different hotspots, simple to implement, and interoperable with existing standards. In particular, we propose a specific algorithm called MAXchop, which works efficiently when using only non-overlapping wireless channels, but is particularly effective in exploiting partially-overlapped channels that have been proposed in recent literature. We also evaluate how our channel assignment approach complements previously proposed carrier sensing techniques in providing further performance improvements. Through extensive simulations on real hotspot topologies and evaluation of a full implementation of this technique, we demonstrate the efficacy of these techniques for not only fairness, but also the aggregate throughput, metrics.We believe that this is the first work that brings into focus the fairness properties of channel hopping techniques and we hope that the insights from this research will be applied to other domains where a fair division of a system's resources is an important consideration.
3172403
On overlay schemes to support point-in-range queries for scalable grid resource discovery
A resource directory is a critical component of a grid architecture. P2P computing paradigm could address some of the scalability issues that make distributed resource discovery services challenging. Unfortunately, most existing distributed hash table (DHT) based P2P overlays have difficulty in treating attribute range queries that are common in resource discovery lookups. This paper proposes a general framework for range-based resource discovery. In particular, the proposed framework maps tree-structured logical data (i.e., range indexing) onto a DHT-based physical node space (i.e., resource brokers). In this paper, we consider three mapping schemes from the logical space onto the physical space. Each mapping scheme uses a different replication mechanism to reduce range search time and to achieve load balance. We analytically and experimentally compare the performance characteristics (query/update costs and workload distributions) of these schemes and discuss their applicability under different resource discovery service scenarios.
13652126
Using certes to infer client response time at the web server
As businesses continue to grow their World Wide Web presence, it is becoming increasingly vital for them to have quantitative measures of the mean client perceived response times of their web services. We present Certes (CliEnt Response Time Estimated by the Server), an online server-based mechanism that allows web servers to estimate mean client perceived response time, as if measured at the client. Certes is based on a model of TCP that quantifies the effect that connection drops have on mean client perceived response time by using three simple server-side measurements: connection drop rate, connection accept rate and connection completion rate. The mechanism does not require modifications to HTTP servers or web pages, does not rely on probing or third party sampling, and does not require client-side modifications or scripting. Certes can be used to estimate response times for any web content, not just HTML. We have implemented Certes and compared its response time estimates with those obtained with detailed client instrumentation. Our results demonstrate that Certes provides accurate server-based estimates of mean client response times in HTTP 1.0/1.1 environments, even with rapidly changing workloads. Certes runs online in constant time with very low overhead. It can be used at websites and server farms to verify compliance with service level objectives.