Local Area Network Environment Research Articles

An Inclusive Comparison in LAN Environment between Conventional and Hybrid Methods for Spectral Amplitude Coding Optical CDMA Systems

In this paper, performance analysis of conventional spectral amplitude coding (CSAC) with hybrid (HSAC) for OCDMA system is investigated in local area network (LAN) environment. The CSAC is built based on arithmetic sequence with simple algebraic ways. The HSAC technique is used in which spectral amplitude coding (SAC) combined with wavelength division multiplexing (WDM) to effectively reduce multiple access interference (MAI) and mitigate the influence of phase induced intensity noise (PIIN) arising in photodetecting process. The main idea is to construct the code sequences in SAC domain then repeat it diagonally in the wavelength domain as groups which maintains the same cardinality of a given code weight. Results show that HSAC outperforms CSAC when the number of active users is high due to its better correlation properties. It has been shown that the HSAC can suppress intensity noise effectively and improve the bandwidth utilization significantly up to 4.2 nm.

A Passive Indoor Tracking Scheme With Geometrical Formulation

Passive tracking that aims to track targets without assistant devices, i.e., device-free targets , is addressed as an emerging field recently. This letter proposes a novel passive tracking algorithm with several pairs of position-known wireless terminals (WTs) and access points (APs), which can be implemented in wireless local area network environments. In the proposed scheme, we formulate the crossing point estimation on the line-of-sight paths (LOSPs) between APs and WTs of third parties, which reveal trajectory of the device-free target, as a geometrical optimization problem. Then, the optimization problem is solved by the particle swarm optimization algorithm. As essential knowledge, we first explore the characteristics of the wireless propagation radio frequency tomography, under LOSP. The tracking performance of the proposed scheme is evaluated via computer simulations as well as experiments in a $(5 \times 12)\hbox{-m}^2 $ monitored area. The experimental results show that the proposed scheme can provide remarkable tracking accuracy of as high as decimeters.

Assessment of the peak-to-average power ratio in different channel organization strategies

The benefits of organizing multichannel communications by fragmenting the data in bonded or in aggregated channels have been usually assessed at the media access control layer, being the network traffic the purpose of the studies. Despite the importance of the different kinds of channel organizations over the transmit signal peak-to average power ratio (PAPR) to size the back-off value of the power amplifier, little attention has been paid to it. In this paper the key aspect is the PAPR, which is fundamental to face transmitter designs optimizing the trade-off between linearity and the time-of-life of the batteries. The results are of interest not only in ad hoc cognitive radio networks, but also in some of the latest European Telecommunications Standards Institute and Institute of Electrical and Electronics Engineers standards supporting mobility in either wireless local area network environments or in cellular communications. A standardized radio link is used to model a realistic scenario to study different settings of the aggregate channels and to compare them with channel bonding alternatives. Besides, the suitability of some crest factor reduction techniques is here considered for different channel organizations. The results show how the channel organization (contiguous, regular and random spaced), either with bonded or aggregated strategies, affects the PAPR.

Received Signal Strength Estimation in Wireless Local Area Network (WLAN) Environment

This paper is focused on indoor propagation prediction in wireless local area network. In this paper, measurements of received signal strength were carried out within fifteen meters of the three access points with a step size of one meter at a test bed environment in the Faculty of Engineering Building; Block A, Nnamdi Azikiwe University Awka, Anambra State, Nigeria. The Netstumbler software installed in a laptop (DELL. Model: Inspiron E1505) with an inbuilt wireless interface card was used in recording the received signal strength from each of the access points. Results obtained showed that the received signal strength decreases as the distance of the receiver increases from the transmitting point and the developed mathematical signal model can be used as a valuable tool for accurate prediction of the received signal strength in the testbed environment.

Performance analysis of a k ‐round contention resolution scheme for WLANs

To achieve high efficiency and robustness during the node contention process in medium access control (MAC) protocols, a k-round contention resolution (k-CR) scheme is devised. Theoretical analysis of its success probability of selecting only one node p s and throughput is also presented. Numerical results show that the k-CR scheme can achieve higher p s than the k-round elimination contention (k-EC) scheme, and higher throughput than the k-EC and IEEE 802.11 DCF schemes in a wireless local area network environment.

A dynamic adjustable contention period mechanism and adaptive backoff process to improve the performance for multichannel mesh deterministic access in wireless mesh LAN

Abstract IEEE802.11s draft proposes a new medium access control function-mesh deterministic access (MDA), which is mainly used for single-channel wireless mesh local area network (LAN). In single-channel environment, collisions between control packets and data packets may occur very often. To completely avoid the collision between control packets and data packets, the mesh delivery traffic indication message (DTIM) interval is first divided into contention period and data transmission period. To reduce the hardware requirements in design, we require a mesh point (MP) only equips a single transceiver to support multichannel environment. To provide higher performance and network capacity than the original MDA for wireless mesh LAN, we proposed a multichannel MDA (MMDA) algorithm. However, the MMDA algorithm may suffer from the resource waste problem when wireless mesh LAN is at heavy-loading situation, so this paper proposes a dynamic adjustable contention period (DACP) mechanism to solve this problem. In addition, we use an adaptive backoff process (ABP) to improve the fairness of the MMDA algorithm. The theoretical analysis gives the upper limit of the throughput for the DACP mechanism. The simulation experiments clearly show the results in multichannel wireless mesh LAN environment that the proposed scheme performs better than the MMDA algorithm and the enhanced distributed channel access (EDCA) in throughput, average waiting time, and packet drop ratio.

Reducing handover delays for seamless multimedia service in IEEE 802.11 networks

In IEEE 802.11 wireless local area network (WLAN) environments, handovers occur when a mobile node (client) moves from the coverage area of one access point (AP) to that of another AP. In particular, a handover in multimedia streaming settings requires a series of tasks to be executed – recognising the disconnection to the currently associated AP, searching for other APs in client visibility and so on. The time taken to perform these tasks gives rise to an interruption of service for about 6 s, which greatly decreases users’ quality of experience (QoE). To reduce service disruptions caused by handovers in IEEE 802.11 networks, a soft proactive handover scheme that exploits the received signal strength indicator (RSSI) and scalable video coding (SVC) is proposed. The proposed scheme predicts the time that a handover process is going to start using the RSSI values and receives the lightweight base layer code of the SVC-encoded video during a certain interval before the predicted handover starts. Experimental results show that the proposed scheme can minimise service interruption times during the 802.11 handover operations, thereby increasing QoE.

The SOAP Based Mechanism for Home Environment using Web Services

Recent advancements in smart home systems have increased the utilization of consumer devices and appliances in home environment. However, many of these devices and appliances exhibit certain degree of heterogeneity and do not adapt towards joint execution of operation. Hence, it is rather difficult to perform interoperation especially to realize desired services preferred by home users. In this paper, we propose a new intelligent interoperability framework for smart home systems execution as well as coordinating them in a federated manner. The framework core is based on Simple Object Access Protocol (SOAP) technology that provides platform independent interoperation among heterogeneous systems. We have implemented the interoperability framework with several home devices to demonstrate their effectiveness for interoperation. The performance of the framework was tested in Local Area Network (LAN) environment and proves to be reliable in smart home setting1.

The Design and Implementation of On-Line Examination Using Firewall security

Online Examination System is a software solution, which allows a company or institute to arrange, conduct and manage examinations via an online environment. This can be done through the Internet, Intranet and/or Local Area Network environments. In this paper propose a system that provides security to improve on- line Examination by utilizing DMZ Concept in firewall technology. This research paper, discuss the performance of online exam with respect to the security provided by the firewall technology. This paper concludes that by improving the security system using a firewall that can be incorporated into the proposed system to fulfil the challenge of online examination system. We proposed a system using firewall technology to monitor candidates and control network packets of all machines incorporating the username and password for authentication. This paper provides an overview of online Examination System using firewall technologies.

Optimized Designing of Optical Local Area Network With Optical Code Division Multiple Access Incorporating Forward Error Correction

Optical Code-Division Multiple-Access (OCDMA) have flourished as successful schemes for expanding the transmission capacity as well as enhancing the security for OCDMA. Optical code-division multiple-access is proposed as a natural solution to achieving asynchronous, high-speed connectivity in a local area network environment. Optical CDMA is shown to be competitive with other networking technologies such as WDMA and TDMA, but has the benefit of more flexibility, simpler protocols, and no need for centralized network control. The purpose of this paper is to review the literature on OCDMA overlay systems, including our approach of one dimensional coding of SAC OCDMA. Furthermore, an essential background of OCDMA, recent coding techniques and security issues are also presented.The limitations of one-dimensional optical orthogonal codes for CDMA have motivated the idea of spectral spreading in both the temporal and wavelength domains. If the constraints on constant weight in these two-dimensional codes are relaxed, differentiated levels of service at the physical layer become possible. Areas for further research are suggested which may allow quality of service levels to be guaranteed at the physical layer.

CRP-CMAC: A Priority-Differentiated Cooperative MAC Protocol with Contention Resolution for Multihop Wireless Networks

To improve the cooperative efficiency of node cooperation and multiple access performance for multihop wireless networks, a priority-differentiated cooperative medium access control protocol with contention resolution (CRP-CMAC) is proposed. In the protocol, the helper selection process is divided into the priority differentiation phase and the contention resolution phase for the helpers with the same priority. A higher priority helper can choose an earlier minislot in the priority differentiation phase to send a busy tone. As a result, the protocol promptly selects all the highest priority helpers. The contention resolution phase of the same priority helpers consists of k round contention resolution procedures. The helpers that had sent the first busy tone and are now sending the longest busy tone can continue to the next round, and then the other helpers that sense the busy tone withdraw from the contention. Therefore, it can select the unique best helper from the highest priority helpers with high probability. A packet piggyback mechanism is also adopted to make the high data rate helper with packet to send transmit its data packets to its recipient without reservation. It can significantly decrease the reservation overhead and effectively improve the cooperation efficiency and channel utilization. Simulation results show that the maximum throughput of CRP-CMAC is 74%, 36.1% and 15% higher than those of the 802.11 DCF, CoopMACA and 2rcMAC protocols in a wireless local area network (WLAN) environment, and 82.6%, 37.6% and 46.3% higher in an ad hoc network environment, respectively.

A rapid cooperation-differentiated medium access control protocol with packet piggyback for multihop wireless networks

Abstract To improve the efficiency of node cooperation and multiple access performance in multihop wireless networks, a rapid cooperation-differentiated medium access control (MAC) protocol is proposed. In the protocol, the helper selection process is divided into a priority differentiation phase and contention resolution phase for helpers with the same priority. A higher priority helper can choose an earlier minislot in the priority differentiation phase to send a busy tone. As a result, the protocol promptly selects all the highest priority helpers. The contention resolution phase for the same priority helpers can use any existing collision resolution scheme, such as the k-round elimination contention scheme. Helpers sending a busy tone first can proceed to the next round, while others, sensing the busy tone, subsequently withdraw from contention. Therefore, a unique optimal helper is selected from the highest priority helpers with high probability. A packet piggyback mechanism is also adopted, which allows a high data rate helper with its own data packets, to transmit these to their recipient without reservation. This significantly decreases the reservation overhead and effectively improves cooperation efficiency and channel utilization. Simulation results show that the maximum throughput of the proposed protocol is 39.6% and 9.6% higher than those of the cooperative MAC-aggregation (CoopMACA) and instantaneous relay-based cooperative MAC protocols, respectively, in a wireless local area network environment, and 40.8% and 31.9% higher, respectively, in an ad hoc network environment.

Energy consumption of mobile agents in a wireless ad hoc network environment

In this study the authors consider the energy consumption of mobile agents operating in wireless local area network (WLAN) environment. They present an energy model of an ad hoc WLAN based on the IEEE 802.11 standard and analyse both per-device and WLAN-wide energy consumption. With this model the authors investigate `features' of the 802.11 protocol (such as frame fragmentation, preamble/header lengths and power-save schemes) on energy consumption in the context of a mobile agent management domain. They also consider `clustering' as a means of optimising energy consumption.

Efficient Radio Map Construction Based on Low-Rank Approximation for Indoor Positioning

Fingerprint-based positioning in a wireless local area network (WLAN) environment has received much attention recently. One key issue for the positioning method is the radio map construction, which generally requires significant effort to collect enough measurements of received signal strength (RSS). Based on the observation that RSSs have high spatial correlation, we propose an efficient radio map construction method based on low-rank approximation. Different from the conventional interpolation methods, the proposed method represents the distribution of RSSs as a low-rank matrix and constructs the dense radio map from relative sparse measurements by a revised low-rank matrix completion method. To evaluate the proposed method, both simulation tests and field experiments have been conducted. The experimental results indicate that the proposed method can reduce the RSS measurements evidently. Moreover, using the constructed radio maps for positioning, the positioning accuracy is also improved.

Symmetry Reduction of Time-Triggered Ethernet Protocol

Time-Triggered Ethernet is a relatively new protocol for safety-critical Local Area Network environments, known for its reliability and efficiency in providing seamless fail-safe communication. This paper presents a formal verification of the TTEthernet protocol, based on an interpretation of the TTEthernet specification document, applied to two formal network scenarios that represent a real-time, safety-critical setting. The conceptual model of both scenarios are modeled using the probabilistic timed automata, then, encoded into PRISM code. Also, a set of precise functional requirements is derived from the TTEthernet specification document and expressed using PCTL. Using this approach, the TTEthernet protocol was verified as applied to real-life network environments and one faulty state was identified within one of the settings, thus revealing a possible weak point in TTEthernet protocol.

Study on multi-channel mesh deterministic access for wireless mesh LAN

IEEE802.11s draft proposes a new medium access control (MAC) function-mesh deterministic access (MDA), which is mainly used for single-channel wireless mesh local area network (LAN). In single-channel environment, collisions between control packets and data packets may occur very often. In order to provide higher performance and network capacity for wireless mesh LAN, this article develops an algorithm for MDA to work well on multi-channel wireless mesh LAN. To reduce the hardware requirements in design, a mesh point (MP) only equips single transceiver to support multi-channel environment. To completely avoid the collision between control packets and data packets, the interval of the meshed delivery traffic indication message is first divided into contention period and data transmission period. We newly define a neighbor MP status table for MPs to support multi-channel environment. The mechanism of reserving MDA opportunity (MDAOP) adopts the four-way-handshaking mode to reduce hidden node problem; we propose channel load first random fit and multi-channel best fit mechanisms to select MDAOP. We also propose a multi-channel MDA (MMDA) algorithm to improve the overall performance of wireless mesh LAN in multi-channel environment. The theoretical analysis gives the upper limit of the throughput for MMDA. The simulation experiments clearly show the results in multi-channel wireless mesh LAN environment that MMDA performs better than the enhanced distributed channel access in throughput, average waiting time, and packet drop ratio both in the saturated and non-saturated mode.

Using JPCAP to Prevent Man-in-the-Middle Attacks in a Local Area Network Environment

Internal attacks are as dangerous and malicious as external attacks. A man-in-the-middle (MITM) attack is a serious problem. The attacker can hijack the connection between two communicating parties and capture the packets between them. He or she can modify, add, or prevent the data from reaching the victim. Address resolution protocol (ARP) poisoning can easily exploit the vulnerability present in ARP. Through this, an attacker can easily perform further attacks such as sniffing, denial of service, and MITM among others. The methodology to prevent MITM attacks conducted by ARP spoofing is to first assign unique IP addresses to every node on the local area network (LAN) based upon their MAC address. The algorithm by which IP addresses are assigned is DepMAC-IP proposed in 2010. For example, when working in the Windows OS environment, the existing ARP cannot be changed. The JPCAP (a Java library for capturing and sending network packets) must be used to capture ARP replies. JPCAP is open source and is licensed under GNU LGPL. It can capture Ethernet, IPv4, IPv6, ARP/RARP, TCP, UDP, and ICMPv4 packets.

Sequence Homology Search Using Fine Grained Cycle Sharing of Idle GPUs

In this paper, we propose a Fine Grained Cycle Sharing (FGCS) system capable of exploiting idle Graphics Processing Units (GPUs) for accelerating sequence homology search in local area network environments. Our system exploits short idle periods on GPUs by running small parts of guest programs such that each part can be completed within hundreds of milliseconds. To detect such short idle periods from the pool of registered resources, our system continuously monitors keyboard and mouse activities via event handlers rather than waiting for a screensaver, as is typically deployed in existing systems. Our system also divides guest tasks into small parts according to a performance model that estimates execution times of the parts. This task division strategy minimizes any disruption to the owners of the GPU resources. Experimental results show that our FGCS system running on two nondedicated GPUs achieves 111-116 percent of the throughput achieved by a single dedicated GPU. Furthermore, our system provides over two times the throughput of a screensaver-based system. We also show that the idle periods detected by our system constitute half of the system uptime. We believe that the GPUs hidden and often unused in office environments provide a powerful solution to sequence homology search.

Applying Wireless Classroom to Build a Highly Interactive Learning Environment

Wireless networks now support Web browsing, email, real-time chat, and access to remote computing resources. With the increasing use of small portable computers, this emerging communications infrastructure will enable many new Internet applications. The innovative project at the Yangtze University is currently exploring how educators can use portable handheld computers with wireless Internet access to improve teaching and learning in both local and wide area network environments.

Interoperability framework for smart home systems

Recent advancements in smart home systems have increased the utilization of consumer devices and appliances in home environment. However, many of these devices and appliances exhibit certain degree of heterogeneity and do not adapt towards joint execution of operation. Hence, it is rather difficult to perform interoperation especially to realize desired services preferred by home users. In this paper, we propose a new intelligent interoperability framework for smart home systems execution as well as coordinating them in a federated manner. The framework core is based on Simple Object Access Protocol (SOAP) technology that provides platform independent interoperation among heterogeneous systems. We have implemented the interoperability framework with several home devices to demonstrate their effectiveness for interoperation. The performance of the framework was tested in Local Area Network (LAN) environment and proves to be reliable in smart home setting <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> .