Performance evaluation of WLAN IEEE802.11n using riverbed modeler

A Wireless Local Area Network (WLAN) is a type of Local Area Network (LAN) that uses high frequency radio waves rather than wires to communicate and transmit data [1]. It is a flexible data communication system implemented as an extension to or as an alternative for, a wired LAN. It provides large companies the option to connect the current wired networks to the wireless network without any problems and gives user the option to use any kind of applications regardless of its source or vendors [2]. As data sharing is sometimes slow or worst slowness due to the performance of the WLAN which is a key factor in spreading and usage of such technologies. Hence it is necessary to identify the quality of the wireless connection and how to improve the communication through the WLAN. Therefore, in this paper, Evaluating and Improving Wireless LANs Performance has been proposed to address mains parameters as Wireless LAN performance indicators and then to propose some methods to improve the performance of WLAN connection via OPNET Modeler 9.1., an advanced network simulator.

Wireless mesh networks (WMNs) has been actively explored for a few years, and the IEEE 802.11 Task Group "s" has recently approved the active 802.11s standard for Wireless local area network (WLAN) mesh networking. To provide differentiated channel access and quality of service (QoS) guarantees for multimedia flows, IEEE 802.11s standard employs enhanced distributed channel access (EDCA) as the basic medium access control (MAC) protocol. In this study, the authors focus on modelling and analysing the medium access delay differentiation of EDCA under saturation condition in multi-hop WMNs. The authors develop a three-dimensional Markov chain model to evaluate the medium access delay differentiation of EDCA. In this model, the authors fully consider the performance impact of Request to Send (RTS) frame collisions and data frame collisions and then put forward the pseudo states to distinguish the different back-off procedures induced by these collisions. Using this analytical model, the authors derive the average medium access delay for the flows with different priorities. Comparisons with the simulation results show that the analytical model is extremely accurate.

With the development of Internet computing techniques, continuous data streams from remote sites are commonly used in scientific and commercial applications. Correspondingly, there is increasing demand of assuring the integrity and authenticity of received data streams. Existing strategies of assuring data integrity and authenticity mainly use message authentication codes (MAC) generated on data blocks and transfer the MAC to the receiver for authentication through either out of band communication or in band communication. Transferring the MAC via out of band communication inevitably introduces communication overhead and additional complexity to synchronize the out of band communication with the data communication. Transferring the MAC via in band channel can be achieved by either appending the MAC to the original data or embedding the MAC into the original data, which would either incur communication overhead or change the original data. It would be desirable to be able to authenticate the stream data without any communication overhead and changing the original data at the same time. To deal with data packet or block loss, many of existing stream data authentication schemes rely on hash chaining, the current usage of which results in uncertainty in authenticating the subsequent data blocks once the first data packet or block loss is detected. In this paper, we propose a novel application layer authentication strategy called DaTA. This authentication scheme requires no change to the original data and causes no additional communication overhead. In addition, it can continue authenticating the rest of data stream even if some data loss has been detected. Our analysis shows that our authentication scheme is robust against packet loss and network jitter. We have implemented a prototype system to evaluate its performance. Our empirical results show that our proposed scheme is efficient and practical under various network conditions

Smart metering utility network (SUN) is an emerging wireless technology for achieving intelligent control and information transfer in smart grid applications. However, the operation of SUNs on unlicensed bands is very sensitive to external interferences generated from other networks working on the same spectrum bands, such as wireless local area networks (WLANs). This paper aims to analyze packet error rate (PER) performance of a victim SUN receiver under the interferences of one or more WLAN transmitting nodes. To deal with a scenario leveraged by multiple random variables, such as offset between desired SUN data packet and WLAN packet, duration of WLAN data packet, and time interval between two consecutive WLAN packets, we propose a segmented packet collision model with the help of the probability theory. We first divide all the packets into small segments and then calculate the collision probability of each segment to acquire a more accurate bit error rate (BER). Then, based on different BERs in distinct segments of the desired SUN packet, average PER of the victim SUN receiver is obtained. Finally, the proposed analytical model is validated by simulations as an effort to evaluate PER performance of a SUN receiver under the WLAN interferences.

Cognitive Radio (CR) is expected to bring about a more flexible wireless communication environment by the efficient utilization of spectrum resources. In this paper, a CR coexisting with IEEE 802.11 Wireless Local Area Networks (WLANs) is proposed. In the Distributed Coordination Function (DCF) access scheme in IEEE 802.11 WLAN, a station (STA) transmits a data frame by executing a random backoff procedure after Distributed Inter Frame Space (DIFS) period, and the destination STA of the data frame responds with Ack frame to the source STA after Short Inter Frame Space (SIFS) period. After the Ack frame is transmitted, the same procedures are repeated. The proposed CR terminal recognizes the DIFS period and the SIFS period, and then it transmits CR signals during these periods with the transmission power that does not affect the IEEE 802.11 WLAN protocol. Thus, the proposed CR terminals recognize the periods during which IEEE 802.11 STAs do not transmit any frames and they use the periods to transmit CR signals. In this paper, IEEE 802.11 WLAN STA that has the capability for the proposed CR technique in addition to the normal 802.11 WLAN capability is considered and the improved average throughputs by the CR communications are evaluated in the computer simulation, and then the effectiveness of the proposed method is clarified.

Medium access control (MAC) is a key issue for the efficiency of IEEE 802.11 wireless local area network. Legacy 802.11 DCF, using CSMA/CA and a random back-off mechanism, provides a simple-to-implement solution, however it achieves very low throughput. Exploiting the existence of a central entity in the infrastructure mode of an 802.11 wireless network, we propose a new centralized scheduling-based MAC protocol which is based on the popular DCF mechanism. This simple yet efficient scheme illustrates a new paradigm for realistic medium access control protocol design for next generation wireless networks. We have evaluated the performance of the proposed protocol by extensive simulations in different scenarios of wireless networks. Simulation results show that the new protocol significantly improves the network performance in terms of throughput and medium access delay.

Rapid growth and increasing requirements for service quality, reliability, and efficiency have made traffic evaluation an essential consideration in design and operation of data transmission networks. In this paper we analyse performance measures of data transmission network servicing batch data flows. The article provides analysis of the one channel queuing system transmitting data packet flow general distributed. In this article we introduce queuing system with finite and infinite buffer capacity. In this article we analyse such data packets transmission performance param- eters: average time spent by data packet in system, data packet delay variation, data packet loss. The data packet arrival rate and channel data packet transmission rate are independent of system state. A key mechanism of the proposed traffic model is that packet time spent in the system depends on channel utilization level, packet flow type and size of transmit- ted data. The proposed simulation model can be used when packet interarrival time follows such distributions: Pareto, Poisson, uniform, normal distribution. Simulation results of performance measures are defined by mathematical mod- els. Considering simulation results recommendations were proposed to improve performance measures for batch data flow transmission over data networks.

The Distributed Coordination Function (DCF) is the fundamental access method defined in the IEEE 802.11 Standard for Wireless Local Area Networks (WLANs). With this standard, the Access Point (AP) and the mobile stations consume a significant amount of energy to contend for access to the shared wireless channel. In order to improve the energy efficiency of WLANs, we investigate in this paper a simple and backwards compatible mechanism, called Bi-Directional DCF (BD-DCF), that enables bidirectional communications between wireless stations with a single channel access invocation. The key idea is to let the AP or any mobile station transmit a data packet together with the acknowledgement upon the successful reception of a data packet. This approach reduces the communication overhead, the channel contention, and better balances uplink and downlink transmission opportunities. We evaluate the performance of the proposed BD-DCF by means of computer-based simulation considering different traffic loads, degrees of traffic symmetry, data packet sizes, and data rates. The results presented in this paper show that the BD-DCF protocol can improve the energy efficiency of DCF up to 50%.

This paper is focused on the statistical analysis of packet arrival process in wireless LAN. The approach is fully empirical, and is based on large traces, captured from real wireless LAN. A variety of models for the packet interarrival times distribution are examined. In addition to Q-Q plot and Cramer-von Mises type statistics, are used to evaluate the models. Our findings, different from those of packet interarrival times obtained in wired backbone LAN calculations, indicate that general distribution are not applicable for wireless LAN packet arrival process. Another result of our analysis was that packet interarrival times are long-range dependent. Therefore, traffic models that assume independent exponentially distributed packet interarrival times may not produce reliable results if applied to performance analysis of wireless LAN.

This paper presents a wireless LAN based medical informatics system for storing and retrieving medical images. The system captures, digitizes and compresses a selected image and places it in a GUI with patient data and comments entered either by keyboard or speech recognition system. A given image with comments is transmitted to a server computer by wireless LAN or wired LAN, and incorporated into the patient's file. The system is intended for smaller hospitals or even field operations, and was designed with low cost components. The system is platform independent by using code written in Java. Physicians access from outside the hospital is via the Internet.

There are various attack which is possible in the network, it may be from externally or internally. But internal attacks are more dangerous than external. So, my mainly concern upon Wireless LAN and Wired LAN attacks which occurs internally. There are various Signature based tools, IDS/IPS (Intrusion detection or prevention system) available now-a-days for detecting these types of attacks but these are not sufficient due to high false alarm rate. So, I detect these types of attacks with three ways: through Wireshark, with signature based tools (Snort and Kismet) and with machine learning tools (WEKA). In wired LAN attack, my mainly concern on PING scan or PING flood, NMAP scan (portsweep) and ARP spoofing attacks. In wireless LAN attacks, I take care of Deauthentication attack, Disassociation attack and Access point (AP) spoofing attack. Signature based tools detect these types of the attacks based on the stored signature and timing threshold. But machine learning tools take several different feature to detect these types of attacks with more accuracy and low false positive rate.

Wireless sensor technology-based structural health monitoring (SHM) has been widely investigated recently. This paper proposes a fast-moving wireless sensing technique for the SHM of bridges along a highway or in a city in which the wireless sensor nodes are installed on the bridges to automatically acquire data, and a fast-moving vehicle with an onboard wireless base station periodically collects the data without interrupting traffic. For the fast-moving wireless sensing technique, the reliable wireless data transmission between the sensor nodes and the fast-moving base station is one of the key issues. In fast-moving states, the data packet loss rates during wireless data transmission between the moving base station and the sensor nodes will increase remarkably. In this paper, the data packets loss in the fast-moving states is first investigated through a series of experiments. To solve the data packets loss problem, the compressive sensing (CS)-based lost data recovery approach is proposed. A field test on a cable-stayed bridge is performed to further illustrate the data packet loss in the fast-moving wireless sensing technique and the ability of the CS-based approach for lost data recovery. The experimental and field test results indicate that the Doppler effect is the main reason causing data packet loss for the fast-moving wireless sensing technique, and the feasibility and efficiency of the CS-based lost data recovery approach are validated Copyright © 2014 John Wiley & Sons, Ltd.

As wireless local area networks (WLANs) are rapidly deployed to expand the field of wireless products in military settings, the provision of robust and efficient communication in the face of noisy environments will be mandatory. Such design needs to take into consideration the WLANs limited bandwidth and high error rates. We introduce the concept of super polling which can be implemented within the IEEE 802.11 Point Coordination Function (PCF) media access control scheme. We notice a dramatic throughput increase (up to 85%) when compared with the single poll mechanism used in IEEE 802.11 PCF. The throughput increase is measured as a function of the channel noise, the superpoll overhead per data packet and the packet size.

Currently, the IEEE 802.11n wireless local-area network (WLAN) has been broadly deployed world-wide for flexible and high-speed Internet access communications. Since it uses the limited number of partially overlapping channels (POCs) at 2.4 GHz band, the throughput performance is often degraded by interferences from signals of other WLANs. Thus, we have studied throughput drop estimation models for concurrently communicating multiple links under interferences, where the 40 MHz channel bonding (CB) and 20 MHz non-CB are considered separately. We have observed that the simultaneous use of CB and non-CB can improve the performance by enhancing the channel capacity while reducing the interference. In this paper, we study the throughput drop estimation model for concurrently communicating links under coexistence of CB and non-CB in IEEE 802.11n WLAN. The model accuracy is verified by comparing the estimated throughput with the measured one under various network topologies.

In Wireless Local Area Networks (WLANs), channel management is important in achieving reliable data communications and satisfying QoS requirements. The key aspects of wireless channel management are monitoring the channel quality and adapting quickly to the network conditions by switching to a better channel. We propose a wireless channel monitoring system with co-located monitoring surrogates. Our system works on multi-radio Access Points (APs) where a co-located surrogate radio monitors the condition of various channels while the master radio serves the clients for data communication. Although we have designed our system for generic WLANs, we believe it will be most useful for IEEE 802.11n networks where there are a large number of channels and dynamic frequency selection is required. Our system enables intelligent, fast channel adaptation, reduces service disruption time, and consequently helps realize the performance potential of 802.11n. We present our multi-radio co-located wireless channel monitoring surrogate system and evaluate its effectiveness on our IEEE 802.11n network testbed. We also perform case studies to demonstrate the benefit our system brings compared against the existing schemes.