Semi-Distributed Backoff: Collision-Aware Migration from Random to Deterministic Backoff

In wireless local area networks (WLANs) packet classification is done to report matched packet to its destination node. Although several schemes are proposed, they suffer from execution corruption. In this paper initially a choleric layer is being constructed in WLANs to increase the bandwidth and performance of WLANs. We use Joint-Interface to combine all the layers. By using cross layer co-ordination among all layer is increased while comparing to the traditional layer architecture. When the packet arrives they are moved to routing table where all possible path to the nearest neighbor are found out and moved to, forwarding table which contains only the route chosen by the routing algorithm. Routing table is constructed using Ad-hoc on demand distance vector protocol. While forwarding packet, it is being double encrypted and decrypted. In order to avoid congestion occurrence near destination elliptical priority scheduling is used where time slot is given for each packet to be processed out and to send packet based on a priority algorithm are being used. Hence we can increase the classification speed and performance.

Wireless communication provides users many benefits such as portability, flexibility, reduced hardware need and lower installation costs. Wireless local area networks (WLANs) for example allow users the ability to carry their laptops from place to place without any physical wires and without losing network connectivity.However, some amount of security risk is always associated with wireless networks. The most significant security risk for wireless technology is the potential outsiders have in gaining access to the communications medium, the communications medium being the air waves. Though WLANs provide the users with the option of roaming, this convenience is facilitated by broadcasting packets to anyone with compatible equipment within range of a transmitting device. This broadcasting of packets induces a compromise between convenience and security. Having an unsecured WLAN can result in a loss of service, or can be used as a staging area to launch attacks against other networks. The significant challenges faced today in securing wireless LANs are maintaining privacy, data confidentiality, and preventing unauthorized access using proper access control mechanisms.As wireless networking and security become more prevalent in the market, more and more computer science programs are incorporating courses in wireless networks or at the least, devoting a significant percentage of the advanced networking courses to wireless topics. As a result, in addition to industry practitioners, there is a growing interest among university researchers and faculty regarding tools used in monitoring and assessing security threats for wireless networks.This paper will demonstrate and evaluate a free and open source software tool, called Network Stumbler, used for monitoring and assessing security threats for wireless networks. Network Stumbler is a Windows-based tool that allows you to detect Wireless Local Area Networks (WLANs) using 802.11b, 802.11a and 802.11g. It has many uses:• Verifies that your network is set up the way you intended.• Find locations with poor coverage in your WLAN.• Detects other networks that may be causing interference on your network.• Detects unauthorized rogue access points in your workplace.• Helps aim directional antennas for long-haul WLAN links.• Can be used recreationally for WarDriving.

The development of protocol standards and the low cost of wireless equipment increased the number of wireless network installations in public (airports, universities campuses) and private (enterprises, homes) areas all over the world. This research effort examines the IEEE 802.11 protocol that dominates wireless local area networks (WLANs). Specifically, it investigates the performance of the Distributed Coordination Function (DCF) of ΙEEE 802.11 Medium Access Control (MAC) protocol. The objective of this thesis is to contribute in the research for the development of a simple and effective MAC sub-layer for WLANs that utilize the IEEE 802.11 protocol. Mathematical models are developed to calculate the following metrics in order to examine the performance of DCF that use Binary Exponential Backoff (BEB) algorithm: a) average packet delay per backoff stage and probability per backoff stage b) average packet delay, c) packet jitter, d) packet drop probability, e) average packet drop time, f) packet delay distribution, and g) cumulative packet delay distribution. An admission control algorithm is also presented. The proposed mathematical models are a) simple, as expressed with relatively simple mathematical relations, b) accurate, since they are validated by comparing analytical against simulation results and show that the proposed models are fairly accurate, and c) provide results in short period of time. Different scenarios of WLANs are examined to investigate the effect of DCF parameters in performance and to define the system parameters values that improve the performance of the IEEE 802.11 protocol. The analysis of metrics and the application of their outcomes to WLANs contribute in the design and development of more efficient access methods to wireless medium. The main contribution of this thesis is that packet delay is investigated thoroughly as a measure of WLAN performance.%%%%Η ανάπτυξη προτύπων για τα ασύρματα τοπικά δίκτυα σe συνδυασμό μe το χαμηλό κόστος της ασύρματης τeχνολογίας eπέτρeψe την ραγδαία eξαπλωση των ασυρμάτων δικτύων σe κοινόχρηστους και σe ιδιωτικούς χώρους όπως πανeπιστήμια, πλατeίeς, αeροδρόμια, γραφeία eπιχeιρήσeων, οικίeς, κλπ. Η παρούσα διατριβή μeλeτά το πρωτόκολλο ΙEEE 802.11 το οποίο κυριαρχeί στα ασύρματα τοπικά δίκτυα. Eιδικότeρα eρeυνά την απόδοση της κατανeμημένης διαδικασίας πρόσβασης DCF του υποeπιπέδου MAC του ΙEEE 802.11. Σκοπός της παρούσας eρeυνητικής προσπάθeιας eίναι η συμβολή στην έρeυνα για την ανάπτυξη eνός απλού και αποτeλeσματικού υποeπιπέδου πρόσβασης μέσου MAC στα ασύρματα δίκτυα που βασίζονται στο πρωτόκολλο ΙEEE 802.11. Αναπτύσσονται μαθηματικά μοντέλα για τον υπολογισμό των ακόλουθων μeτρικών για την απόδοση της διαδικασίας DCF που χρησιμοποιeί τον αλγόριθμο eκθeτικής οπισθοχώρησης ΒEΒ: α) την μέση καθυστέρηση των πακέτων ανά βαθμίδα οπισθοχώρησης και την πιθανότητα ανά βαθμίδα οπισθοχώρησης, β) την μέση καθυστέρηση των πακέτων, γ) την κατανομή των καθυστeρήσeων των πακέτων, δ) την αθροιστική κατανομή των καθυστeρήσeων, e) την διακύμανση των καθυστeρήσeων των…

Wireless Local Area Networks (WLANs) and Wireless Metropolitan Area Networks (WMANs) are two of the main technologies in wireless data networks. WLANs have a short range and aim at providing connectivity to end users. On the other hand, WMANs have a long range and aim at serving as a backbone network and also at serving end users. In this dissertation, we consider the problem of Medium Access Control (MAC) in WLANs and the placement of Relay Stations (RSs) in WMANs. We propose a MAC scheme for WLANs in which stations contend by using jams on the channel. We present analytic and simulation results to find the optimal parameters of the scheme and measure its performance. Our scheme has a low collision rate and delay and a high throughput and fairness performance. Secondly, we present a MAC scheme for the latest generation of WLANs which have very high data rates. In this scheme, we divide the stations into groups and only one station from each group contends to the channel. We also use frame aggregation to reduce the overhead. We present analytic and simulation results which show that our scheme provides a small collision rate and, hence, achieves a high throughput. The results also show that our scheme provides a delay performance that is suitable for real-time applications and also has a high level of fairness. Finally, we consider the problem of placing Relay Stations (RSs) in WMANs. We consider the Worldwide Interoperability for Microwave Access (WIMAX) technology. The RSs are used to increase the capacity of the network and to extend its range. We present an optimization formulation that places RSs in the WiMAX network to serve a number of customers with a pre-defined bit rate. Our solution also provides fault-tolerance by allowing one RS to fail at a given time so that the performance to the users remains at a predictable level. The goal of our solution is to meet the demands of the users, provide fault-tolerance and minimize the number of RSs used.

Recent demands on affordable, portable wireless communication and computation devices have resulted in exponential growth of wireless networks ranging from Wireless Local Area Networks (WLAN) and Wireless Wide Area Networks (WWAN) to Ad-Hoc and Sensor networks. The major goal of wireless communication is to allow users to communicate together and to have access to global network anytime anywhere. This has led to wide acceptance of infrastructure based cellular networks (WWANs) where mobile stations communicate with a centralized controller, often referred as Access Point (AP) that is connected to the wired networks. On the other hand, WLANs have appeared as dominant popular technologies in many venues including a local area such as an academic campus or an airport terminal. These wireless networks mostly rely on IEEE 802.11 Wi-Fi (Wireless Fidelity) technology and its various derived versions (i.e. 802.11a,b,g). IEEE 802.11 standard supports two operational modes: The infrastructure-based Wireless Local Area Networks (WLANs) and an infrastructure-less Ad-Hoc Networks. A WLAN (Conti, 2003) typically imposes the existence of an AP and normally is connected to the wired networks to provide internet access for mobile devices. Obviously, only one hop link is needed to communicate between mobile devices and AP. In contrast, there is no AP or infrastructure in Ad-Hoc networks. Any two stations can communicate directly when they are in the range of reception of each other. To this end, the stations may use multi-hop routing to deliver their packets to destinations. The ad-hoc protocols (Conti, 2003; Mohapatra & Krishnamurthy, 2005) are self-configured for address and routing in the face of mobility and the network topology may change in each configuration. The multi-hop wireless ad-hoc networks, or multi-hop wireless networks enable wireless networking in the environments where the wired or cellular connections are impossible, inadequate, or cost effective (e.g. battle field, disaster recovery, etc.). The popularity of internet over the last decades has resulted in rapid advancement of demanding applications. The Transmission Control Protocol/Internet Protocol (TCP/IP) (Stevens, 1994) is a well-known de facto protocol in developing today’s internet. Basically, TCP provides a connection-oriented and reliable end-to-end data delivery between two hosts in traditional wired networks. Since TCP is well tuned and due to its wide acceptance in internet, it is desirable to extend and adopt its functionality to wireless networks. On the

Wireless Local Area Network (WLAN) is an alternative in overcoming cabling problems in a local network. Often wireless network security that is installed still uses vendor default settings such as SSID, IP Address, remote management, DHCP enabled, frequency channels, without encryption, even user or password for wireless administration. How does a strong WLAN security system work? The most common security system applied to wireless networks at this time is starting from securing access points by applying the MAC Filtering concept, using WPA / WPA2-PSK security keys, and RADIUS server authentication. To see the quality of wireless LAN network security, how do you analyze the test of the existing security system in the network. The method that can be used in evaluating wireless networks is by testing the system by simulating forms of attacks on wireless networks with the Penetration Testing method. By carrying out 4 stages of research using the penetration testing method (i) the planning stage, (ii) the discovery stage, (iii) the attack stage and (iv) the report stage, from the attack stage (Cracking The Encryption, Bypassing MAC Address, Attacking The Infrastructure and MITM ) using Kali Linux got the results of four types of attacks carried out, only one of which was failed, namely the cracking attack type of the encryption on the RADIUS server due to using captive portal authentication

With the increasing popularity of the wireless network, the security issue for mobile users could be even more serious than it can be expected. Here it is need to search for new architecture and mechanisms to protect the wireless networks and mobile computing application. This paper focuses on intrusion detection and security consideration in wireless local area networks (WLANs) and also presents intrusion detection for WLANs, which gives a wireless intrusion detection system and its architecture consideration. A wireless IDS is similar to a standard, wired IDS, but has additional deployment requirements as well as some unique features specific to WLAN intrusion and misuse detection. Meanwhile, we discuss some issues with wireless networks and Intrusion detection solution to wireless networks.

The performance of Wireless Local Area Network (WLAN) is highly dependent on the processes that are implemented in the Medium Access Control (MAC) sublayer regulated by the IEEE 802.11 standard. In turn, various parameters affect the performance of the MAC sublayer, the most important of which is the number of stations in the network and the offered load. With the massive growth of multimedia traffic, research of the network performance depending on traffic types is relevant. In this paper, we present the impact of a high-/low-priority traffic ratio on WLAN performance with different numbers of access categories. The simulation results show different impact of high-/low-priority traffic ratio on the performance of the MAC sublayer of wireless LANs depending on different network-sizes and on network conditions. Performance of the large network with two access categories and with the prevalent high-priority traffic is significantly higher than in the case of using four categories on the MAC sublayer. This allows us to conclude that the performance improvement of the large network with the prevalent high-priority traffic can be achieved by an adaptive adjustment of the access categories number on the MAC sublayer.

Wireless networks are being deployed widely to provide network connectivity without requiring the web of physical wires. A collection of a small number of workstations connected using a wireless network forms a wireless local area network (WLAN) that follows the IEEE 802.11 standard. In a WLAN, the communication takes place using packets whose sizes may vary and have a significant impact on the delay incurred during transmission. In this regard, fragmentation may play a vital role in reducing the delay for efficient transmission across the network. This paper analyzes the performance of WLANs with respect to the packet fragmentation. We simulate three network scenarios having 4, 8 and 12 wireless workstations respectively. The scenarios are simulated using OPNET IT Guru Academic Edition v 9.1 while incorporating a peer-to-peer (P2P) based communication model for each scenario. We compare the performance of non-fragmented and fragmented communication in terms of network delay and throughput. Our results show that the fragmentation minimizes the delay and increases the throughput, however its impact is highly dependent on the size of the underlying network.

Rapid deployment of IEEE 802.11 wireless local area networks (WLANs) and their increasing quality of service (QoS) requirements motivate extensive performance evaluations of the upcoming 802.11e QoS-aware enhanced distributed coordination function (EDCA). Most of the analytical studies up-to-date have been based on one of the three major performance models in legacy distributed coordination function analysis, requiring a large degree of complexity in solving multidimensional Markov chains. Here, we expose the common guiding principle behind these three seemingly different models. Subsequently, by abstracting, unifying, and extending this common principle, we propose a new unified performance model and analysis method to study the saturation throughput and delay performance of EDCA, under the assumption of a finite number of stations and ideal channel conditions in a single-hop WLAN. This unified model combines the strengths of all three models, and thus, is easy to understand and apply; on the other hand, it helps increase the understanding of the existing performance analysis. Despite its appealing simplicity, our unified model and analysis are validated very well by simulation results. Ultimately, by means of the proposed model, we are able to precisely evaluate the differentiation effects of EDCA parameters on WLAN performance in very broad settings, a feature which is essential for network design.

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.

The increasing demand for the coverage of high‐speed wireless local area networks (WLANs) is driving the installation of a very large number of access points (APs). Wireless mesh networks (WMNs) have emerged as a promising technology in the next generation networks to provide economical and scalable broadband access to wireless interconnection of multiple APs that manage individual WLANs in order to extend the coverage of the conventional single WLANs. In this paper, we develop a new analytical model to investigate the quality‐of‐service (QoS) performance metrics in WMNs interconnecting multiple WLANs. The model takes the phenomenon of communication locality into consideration. Extensive simulation experiments are conducted to validate the accuracy of the analytical model. The proposed model is then used to obtain the maximum achievable throughput, which is a key performance metrics in wireless networks. Moreover, we utilize the model to evaluate the impact of communication locality on network performance and investigate its effects on the optimization of integrated WLANs and multi‐hop mesh networks. Copyright © 2009 John Wiley & Sons, Ltd.

Wireless network security protocols are essential for enhancing security, privacy and confidentiality. However, network security protocols also require network resources in other to carry out authentication of users through the use of encryption keys and packet encryption. It is therefore relevant to investigate the effects of the amount of resources used by recommended wireless network security protocols in other to determine if user quality of experience and user quality of service is affected by the implementation wireless network security protocols. Our research investigates and examines the effect of security protocols on wireless network performance. The Wi-Fi Protected Access 2 - PreShared Key (WPA2-PSK) was used as the security protocol in focus while throughput was the network performance feature that was analyzed. Experiments were carried out which showed that throughput in a non-secured Wireless Local Area Network (WLAN) is a bit higher than throughput in a secured WLAN. Our research contributes to the future development of WLAN protocols with low network resource consumption in other to contribute to improved network performance.

In IEEE 802.11 wireless local area networks (WLANs), TCP suffers unfairness between uplink and downlink flows due to its asymmetric reactions towards data and ACK losses at the AP (Access Point), and the AP's inability to distinguish itself from other contending stations accessing the medium. In this paper, we propose a novel dual queue management (DQM) scheme with ECN (Explicit Congestion Notification) at the AP's downlink buffer to improve TCP performance in infrastructure WLANs. Our approach maintains two queues for TCP ACK and data respectively, with their total length controlled by a PI (Proportional Integral) controller to prevent congestion. ACK/data packets are marked/dequeued dependent on uplink/downlink time usage of the wireless channel. We also propose an opportunistic scheduling mechanism of the two queues exploiting multi-rate capability and multi-user diversity for more efficient link utilization. We evaluate the proposed approach in ns-2 and our simulation results demonstrate that this design with few states can significantly improve TCP congestion control, fairness performance and link utilization in WLANs.

Automated interference detection is required for operation and management services in wireless networks as Wireless Local Area Networks (WLANs) based on IEEE 802.11 Standard since co-channel interference from other wireless transmitters occurs irregularly. We propose a new approach for detecting the presence of interference on 802.11 links. Our solution focuses on the Access Point (AP)-initiated monitoring approach without Wireless Station (STA)-initiated additional function and sniffer devices. Our approach uses the geographical distribution of the response delay of the Acknowledgment packet (ACK) to the downlink packet that AP transmitted to STAs. The proposed method consists of a continuous monitoring step and a periodical diagnosis step to measure network statistics by ACK response delay between an AP and STAs and to detect whether and where interference occurs respectively. Comprehensive simulation results show that the proposed approach has a good accuracy and low misdetection ratio for diagnosing the interference existence and location in IEEE 802.11 WLANs.