Local Area Network Environment Research Articles

Improved Markov predictor in wireless networks

As wireless networks have been an integral part of our daily life, mobility prediction techniques have become one of the main topics in current research efforts. An accurate prediction of the next cell to which the mobile users are going can greatly improve the performance of wireless applications, such as map resource allocation, congestion control, quality of service and mobility management. It has been shown that the Markov predictor is a good mobility predictor in actual wireless local area network environments. However, from the standpoint of conditional entropy, the authors analyse that the Markov predictor has the disadvantage of performing worse when the location history is lacking or an approximate tie has happened. As a consequence, a novel improved Markov predictor is proposed, and simulations are conducted to evaluate the performance of the proposed scheme. The simulation results show that the improved Markov predictor solves not only the disadvantages of Markov predictor due to the lack of location history information, but also the expansion of state space in multiple-order Markov predictors.

Indoor Localization via Discriminatively Regularized Least Square Classification

In this paper, we address the received signal strength (RSS)-based indoor localization problem in a wireless local area network (WLAN) environment and formulate it as a multi-class classification problem using survey locations as classes. We present a discriminatively regularized least square classifier (DRLSC)-based localization algorithm that is aimed at making use of the class label information to better distinguish the RSS samples taken from different locations after proper transformation. Besides DRLSC, two other regularized least square classifiers (RLSCs) are also presented for comparison. We show that these RLSCs can be expressed in a unified problem formulation with a closed-form solution and convenient assessment of the convexity of the problem. We then extend the linear RLSCs to their nonlinear counterparts via the kernel trick. Moreover, we address the missing value problem, utilize clustering to reduce the training and online complexity, and introduce kernel alignment for fast kernel parameter tuning. Experimental results show that, compared with other methods, the kernel DRLSC-based algorithm achieves superior performance for indoor localization when only a small fraction of the data samples are used.

An Effective Adaptive Autocorrelation-Based Neighboring Matching Location-Aware Computing in WLANs

The recent advances of ubiquitous wireless infrastructures and requirements for high speed context-aware computing have created the opportunities to supply the high efficient location based service (LBS) in indoor wireless local area network (WLAN) environment. Because of the serious multi-path effect, unpredictable co-channel interference and inherent equipment noise, the measured signal strengths vary a lot in the real-world indoor environment. And this strength variation will also result in the performance deterioration of radio map-based neighboring matching algorithm. In response to this compelling problem, we propose the adoption of adaptive autocorrelation-based signal preprocessing method as a specific solution by effectively eliminating the singular strength from the original fingerprint set. Finally, the feasibility and effectiveness of autocorrelation-based preprocessing are also verified by decreasing about 33.4% and 32.9% of errors in k nearest neighbor (KNN) and weighted KNN (WKNN).

On Localization Using Location Fingerprints and Energy Efficient Operation of WLANs in Indoor Areas

This study focuses on the power efficient localization by fingerprinted KNN algorithm in the indoor wireless local area network (WLAN) environment. To the best of our knowledge, although the fingerprint algorithm has been utilized to supply some special location based service (LBS) with high precision and accuracy, these associated location systems have resulted in significant energy consumption. Therefore, serious attention should be paid on the energy consumption because of the hundreds to thousands of access points (APs) with high-density deployed in our university campuses and corporate offices. In response to this compelling problem, we discuss the relationship between energy costs and radio map-based location performance for the Gaussian radio signal strength (RSS) distribution with different neighboring points in KNN. Furthermore, using our results, the guidelines on the power efficient fingerprint location algorithm is also provided.

RITAS: Services for Randomized Intrusion Tolerance

Randomized agreement protocols have been around for more than two decades. Often assumed to be inefficient due to their high expected communication and computation complexities, they have remained overlooked by the community-at-large as a valid solution for the deployment of fault-tolerant distributed systems. This paper aims to demonstrate that randomization can be a very competitive approach even in hostile environments where arbitrary faults can occur. A stack of randomized intrusion-tolerant protocols is described and its performance evaluated under several settings in both local-area-network (LAN) and wide-area-network environments. The stack provides a set of relevant services ranging from basic communication primitives up to atomic broadcast. The experimental evaluation shows that the protocols are efficient, especially in LAN environments where no performance reduction is observed under certain Byzantine faults.

To Our Readers

In IEEE 802.11 networks, many access points (APs) are required to cover a large area due to the limited coverage range of APs, and frequent handoffs may occur while a station (STA) is moving in an area covered by several APs. However, traditional handoff mechanisms employed at STAs introduce a few hundred milliseconds delay, which is far longer than what can be tolerated by some multimedia streams such as voice over Internet protocol (VoIP), it is a challenging issue for supporting seamless handoff service in IEEE 802.11 networks. In this paper, we propose a pre-scan based fast handoff scheme within an IEEE 802.11 enterprise wireless local area network (EWLAN) environment. The proposed scheme can help STA obtain the best alternative AP in advance after the pre-scan process, and when the handoff is actually triggered, STA can perform the authentication and reassociation process toward the alternative AP directly. Furthermore, we adopt Kalman filter to minimize the fluctuation of received signal strength (RSS), thus reducing the unnecessary pre-scan process and handoffs. We performed simulations to evaluate performance, and the simulation results show that the proposed scheme can effectively reduce the handoff delay.

Projection-Based Location System via Multiple Discriminant Analysis in Wireless Local Area Networks

This paper presents a projection-based location system in an indoor wireless local area network (WLAN) environment. Our algorithm projects the received signal strength (RSS) onto a discriminative space such that the information of all access points (APs) is more efficiently utilized. The projection is determined by multiple discriminant analysis (MDA), thereby guaranteeing maximal discriminative information involved in the positioning system. The study conducts a series of experiments on the effects of our approach in a realistic indoor environment. The results show that not only is the positioning accuracy significantly improved, but the system cost, including the computation and data collection, is also greatly reduced at the same time. This is because our approach extracts only useful information for positioning, whereas the redundant noise is discarded to avoid the problem of overfitting and unnecessary calculations. Compared with prior works, this technique can produce a more graceful balance between the positioning accuracy and the computational complexity for the resource-weak clients.

Security-Enhanced OSGi Service Environments

Today's home and local-area network environments consist of various types of personal equipments, network devices, and corresponding services. Since such prevalent home network environments frequently deal with private and sensitive information, it is crucial to legitimately provide access control for protecting such emerging environments. As a result, the open services gateway initiative (OSGi) attempted to address this critical issue. However, the current OSGi authorization mechanism is not rigorous enough to fulfill security requirements involved in dynamic OSGi environments. In this paper, we provide a systematic way to adopt a role-based access control (RBAC) approach in OSGi environments. We demonstrate how our authorization framework can achieve important RBAC features and enhance existing primitive access control modules in OSGi service environments. Also, we describe a proof-of-concept prototype of the proposed framework to discuss the feasibility of our approach using an open source implementation of OSGi framework known as Knopflerfish.

Enhanced Switched Network Sniffer Detection Technique Based on IP Packet Routing

ABSTRACT Sniffers are program that are used to capture network packets illegally. It is a malicious activity performed by network users, and because of this network security is at risk. Detection of sniffers is an essential task to maintaining network security. Man in the middle (MiM) intrusion detection, switched network sniffer detection based on IP packet routing, and ARP watch detection techniques are used to detect a sniffer in switch Local Area Network (LAN) environments. This paper highlights the shortcomings of previous techniques that detect sniffers in switch LAN environments. We propose a new sniffer detection technique based on Internet Protocol (IP) packet routing that removes the shortcomings of previous techniques. Experimental results demonstrate that the proposed detection technique shows a significance improvement in network performance.

Performance Comparison of IP-Networked Storage

Dramatically increasing amounts of digital data are placing huge requirements on storage systems. IP-networked storage systems, such as the network file system (NFS)-based network-attached storage (NAS) systems and the iSCSI-storage area network (SAN) systems, have become increasingly common in today's local area network (LAN) environments. The emergence of new storage techniques, such as object-based storage (OBS) and content aware storage (CAS), significantly improves the functionality of storage devices to meet further needs for storage sub-systems. However, these may impact system performance. This paper compares the performance of NFS, iSCSI storage, object-based storage devices (OSDs), and CAS-based storage systems in an environment with no data sharing across host machines. A gigabit ethernet network is used as the storage network. Test results demonstrate that the performances of these systems are comparable with CAS being much better than the others for write operations. The performance bottlenecks in these systems are analyzed to provide insight into how future storage systems may be improved and possible optimization methods. The analysis shows how the I/O interfaces in these systems affect the application performance and that network-based storage systems require optimized I/O latency and reduced network and buffer processing in the servers.

Using Large-Scale FDTD Method to Obtain Precise Numerical Estimation of Indoor Wireless Local Area Network Office Environment

The Finite-Difference Time-Domain (FDTD) technique is presented in this paper as an estimation method for radio propagation prediction in large and complex wireless local area network (WLAN) environments. Its validity is shown by comparing measurements and Ray-trace method with FDTD data. The 2GHz (802.11b/g) and 5GHz (802.11a) frequency bands are used in both the calculations and experiments. The electric field (E-field) strength distribution has been illustrated in the form of histograms and cumulative ratio graphs. By using the FDTD method to vary the number of human bodies in the environment, the effects on E-field distribution due to human body absorption are also observed for 5GHz WLAN design.

Indoor Location System Based on Discriminant-Adaptive Neural Network in IEEE 802.11 Environments

This brief paper presents a novel localization algorithm, named discriminant-adaptive neural network (DANN), which takes the received signal strength (RSS) from the access points (APs) as inputs to infer the client position in the wireless local area network (LAN) environment. We extract the useful information into discriminative components (DCs) for network learning. The nonlinear relationship between RSS and the position is then accurately constructed by incrementally inserting the DCs and recursively updating the weightings in the network until no further improvement is required. Our localization system is developed in a real-world wireless LAN WLAN environment, where the realistic RSS measurement is collected. We implement the traditional approaches on the same test bed, including weighted kappa-nearest neighbor (WKNN), maximum likelihood (ML), and multilayer perceptron (MLP), and compare the results. The experimental results indicate that the proposed algorithm is much higher in accuracy compared with other examined techniques. The improvement can be attributed to that only the useful information is efficiently extracted for positioning while the redundant information is regarded as noise and discarded. Finally, the analysis shows that our network intelligently accomplishes learning while the inserted DCs provide sufficient information.

A high-speed and low-cost storage architecture based on virtual interface

Over the years, the network storage bandwidth has increased rapidly while the node-to-node latency has not decreased much. This is because the latency is dominated by the protocol software execution time in the kernel, instead of by the raw transmission time over the link. Virtual Interface (VI) protocol has been proposed to overcome the software overhead of the TCP/IP. In this paper, we introduce another new technology vSCSI (VI-attached SCSI) to compete with iSCSI in LAN (Local Area Networks) environment, and compare performance of vSCSI and iSCSI experimentally. Meanwhile, we present a Virtual Interface Storage Architecture (VISA) as a new network storage architecture which uses vSCSI as the network communication protocol. Then, we can take advantage of VI’s superior performance over TCP/IP in LAN environment. Also, actually we have implemented and measured our data transport and Remote Procedure Call (RPC) layer over VI. The aim of our design and implementation is to put forward new techniques to reduce overheads.

Performance limits of pico-cell systems using radio-over-fiber techniques with an electroabsorption modulator

We investigate the performance limits of a pico-cell system using the radio- over-fiber technique with an electroabsorption modulator (EAM) in a 2.4 GHz wireless local area network (WLAN) environment. To understand the performance limits of the system using an EAM as the optical transceiver, we vary the optical modulation index (OMI) of the transmitter for different bias voltages to the EAM. Power margins in the links are found to estimate a possible service range, and packet loss rates (PLRs) in the pico-cell system are measured to evaluate the transmission performance. The total service range can be extended up to 3 m by adjusting the OMI of the transmitter for different applied bias voltages to the EAM.

Practical algorithms for scheduling video data in a local area network environment

Simultaneous transmission of multiple high quality video streams from a server to the clients is becoming an increasingly important class of traffic in a network of workstations or cluster environment. With a powerful symmetric multiprocessor (SMP) as the server and a high-speed network, such transmission is practicable from a hardware point of view. However, the actual construction of such a video data server system entails tackling a number of difficult problems related to the provision of strict quality of service (QoS) guarantees. Among others, the smoothing and scheduling of multiple video packet streams are two crucial issues. Smoothing is concerned with reducing the rate variability of video streams in view of the fact that video data are usually compressed in a variable bit rate fashion. Scheduling is important to guarantee the requested QoS levels while maximizing the utilization of the resources. Although much work on smoothing has been done, it is not clear which scheduling scheme is suitable for multiplexing smoothed video data to the network. In this paper we present an extensive performance study of the EDF and RM scheduling algorithms which are modified to provide QoS guarantees for smoothed video data. With a probabilistic definition of QoS, admission control conditions are incorporated into the two algorithms. Furthermore, a counter-based scheduling module is included as the core scheduling mechanism which adaptively adjusts the actual QoS levels assigned to requests. Our theoretical analysis of the two modified algorithms, called QEDF and QRM, shows that the QRM algorithm is more robust than the QEDF algorithm for different workload and utilization conditions. We also propose to use a new metric called meta-QoS to quantify the overall performance of a packet scheduler given a set of simultaneous requests. In our experiments based on an SMP-based Linux platform, we find that the QRM algorithm can sustain a rather stable level of meta-QoS even when the workload and utilization levels are increased. On the other hand, the QEDF algorithm, due to its conservative admission control policy, is found to be not suitable for a high level of utilization and a large number of requests. In view of the lower complexity of the QRM algorithm, it seems that the QRM approach is a more suitable candidate for packet scheduling in the client-server environment considered in our study.

Performance analysis of mobile agents

The results of a performance analysis of mobile agents in a distributed network environment are presented. Analytical models are developed and used to compare the performance of carrying out a simple management function with mobile agents (MA) or SNMP (simple network management protocol). An examination is made of how delay is affected by the size of the management domain and how each method behaves in both a local area network (LAN) and wide area network (WAN) environment. For large domains, optimal performance is obtained if the mobile agents' size is bounded, and this may require sharing the management task among a small number of mobile agents.

Improving OSPF Dynamics on a Broadcast LAN

In this article, the authors propose modifications to OSPF's interface state machine to reduce the time/processing requirements of the leader election process in a broadcast local-area network (LAN) environment. The proposed modifications are based on dynamic adjustment of wait time duration rather than using a static value. They compare the original and modified state machines both analytically as well as via testbed experiments.

Adaptive bandwidth provisioning in an integrated 3G and WLAN environment

AbstractIn this paper, we propose a practical bandwidth reprovisioning scheme in an integrated third generation (3G) and wireless local area network (WLAN) environment. We investigate how to increase available bandwidth for conversational class while keeping the packet loss probability of background class below a threshold. The proposed scheme is implemented as a simple network management protocol (SNMP) compliant management information base (MIB) and deployed at packet data serving node (PDSN) equipment. The experiments conducted on 1x evolution for data and voice (1xEV‐DV) testbed show that the proposed scheme increases the bandwidth of the conversational class and guarantee adequate service quality of the background class. Copyright © 2005 John Wiley & Sons, Ltd.

Network-based wireless location: challenges faced in developing techniques for accurate wireless location information

Wireless location refers to the geographic coordinates of a mobile subscriber in cellular or wireless local area network (WLAN) environments. Wireless location finding has emerged as an essential public safety feature of cellular systems in response to an order issued by the Federal Communications Commission (FCC) in 1996. The FCC mandate aims to solve a serious public safety problem caused by the fact that, at present, a large proportion of all 911 calls originate from mobile phones, the location of which cannot be determined with the existing technology. However, many difficulties intrinsic to the wireless environment make meeting the FCC objective challenging. These challenges include channel fading, low signal-to-noise ratios (SNRs), multiuser interference, and multipath conditions. In addition to emergency services, there are many other applications for wireless location technology, including monitoring and tracking for security reasons, location sensitive billing, fraud protection, asset tracking, fleet management, intelligent transportation systems, mobile yellow pages, and even cellular system design and management. This article provides an overview of wireless location challenges and techniques with a special focus on network-based technologies and applications.

Distributed steady-state simulation of telecommunication networks with self-similar teletraffic

Recent measurement studies of teletraffic data in modern telecommunication networks have shown that self-similar processes may provide better models of teletraffic than Poisson processes. If this is not taken into account, it can lead to inaccurate conclusions about performance of telecommunication networks. We show how arrival processes with self-similar input influences the run-length of a distributed steady-state simulation of queueing systems in telecommunication networks. For this purpose, the simulation run-length of SSM/ M/1/∞ queueing systems in the method based on the batch means, conducted for estimating steady-state mean waiting times is compared with the results obtained from simulations of M/ M/1/∞ queueing systems when a single processor and multiple processors are used. We also investigate speedup conducted stochastic simulation of SSM/ M/1/∞ queueing systems on multiple processors under a scenario of distributed stochastic simulation known as MRIP (Multiple Replications In Parallel) in a local area network (LAN) environment on Solaris operating system. We show that, assuming self-similar inter-event processes (i.e., SSM/ M/1/∞ queueing systems), many more observations are required to obtain the final simulation results with a required precision, as the value of the Hurst parameter H increases, than when assuming Poisson models, exhibiting short-range dependence (i.e., M/ M/1/∞ queueing systems) on a single processor and multiple processors. Our results show that the time for collecting many numbers of observations under the MRIP scenario is clearly reduced as traffic intensity and the value of the Hurst parameter increase, and as the engaged processor increases one to four. In particular, the value of H influences much more the speedup than traffic intensity and the engaged processor.