Dual Queue Management for Improving TCP Performance in Multi-Rate Infrastructure WLANs

IEEE 802.11 infrastructure wireless local area network (WLAN) is increasingly popular, in which access points (APs) are applied. In a WLAN with an AP connected to the Internet, the communication between any two nodes is relayed by the AP, i.e., the AP serves all the nodes in the WLAN, which degrades throughput. In this paper, we propose a novel network coding scheme called MPOF that is able to encode multiple packets from different data flows and take data rates of links into account so that throughput is improved.

Research on Voice over IP (VoIP) in infrastructure wireless local area networks (WLANs) has shown that, because of the access mechanism, the access point severely limits the number of voice calls a WLAN can support. To address this problem we propose a new scheme based on the IEEE 802.11e quality of service (QoS) mechanism where a tradeoff between codec quality and priority is exploited to improve the number of calls that can be supported. In particular, we propose certain priority settings at the access point (AP) to encourage users to switch to a lower quality codec during periods of high contention and thus enable them to maintain the call. We develop a detailed analytical model to show the benefit of this scheme. Our analytical results are validated by extensive simulation and show that the voice capacity in the network can be significantly improved. Furthermore, by using the ITU-T E-model to assess the voice quality, we show that users with a lower quality codec can still maintain an acceptable level of quality using the proposed scheme.

Voice over Internet protocol (VoIP) is one of the most important applications for IEEE 802.11 wireless local area networks (WLANs). For network planners who deploy VoIP over WLANs, one of the important issues is the VoIP capacity. Directly implementing VoIP over infrastructure WLANs will create the bottleneck problem at the access point (AP). In this paper, we propose the use of the service differentiation provided by the new IEEE 802.11e standard to solve the bottleneck problem and improve voice capacity. In particular, we propose the allocation of a higher priority access category (AC) to the AP while allocating lower priority AC to mobile stations. We develop a simple Markov chain model, which considers the important enhanced distributed channel access (EDCA) parameters and the channel errors under saturation and nonsaturation conditions. Based on the developed analytical model, we analyze the performance of VoIP over EDCA. By appropriately selecting the EDCA parameters, we are able to differentiate the services for the downlink and uplink. The experimental results are very promising. With the adjustment of only one EDCA parameter, we improve the VoIP capacity by 20%-30%.

Wireless communication has experienced enormous growth during the past decade, primarily driven by mobile cellular systems for voice communications, but more recently by the use of wireless local area networks(WLANs) for corporate enterprises and hot spot areas. However, mobile operators will face many challenges both economically and technically, as WLAN evolve through a bewildering number of different standards during the coming years. Potentially this will require several upgrades to the WLAN infrastructure. A new approach for addressing these challenges is evaluated in this paper. It is based on a radio over fiber (RoF) technology that uses electro-absorption modulator (EAM) and off-the-shelf WLAN access point, and it promises to provide solutions that will be transparent to changes in protocols and frequency of operation as well as reducing radio access infrastructure costs

Fuzzy logic modelling can be applied to evaluate the behaviour of Wireless Local Area Networks (WLAN) received signal strength (RSS). The behavior study of WLAN signal strength is a pivotal part of WLAN tracking analysis. Previous analytical model has not been addressed effectively for analyzing how the WLAN infrastructure affected the accuracy of tracking. In this paper, we propose a novel fuzzy spatiotemporal topographic model. We implemented the proposed model with a large (9.34 hectare), built-up university, over 2,000 access points to survey and collect WLAN received signal strength (RSS). We applied the Nelder-Mead (NM) method to simplify our previous work on fuzzy color map into a topographic (line-based) map. The new model can provide a detail and quantitative strong representation of WLAN RSS. Finally, it serves as a quicker reference and efficient analysis tool for improving the design of WLAN infrastructure.

Queueing systems to study the energy consumption of a campus WLAN

In this paper, we study the problem of enhancing the fault tolerance of IEEE 802.11 wireless local area networks in the design stage. Our goal is to place minimal number of APs (access points), such that the system can tolerate AP failures while guaranteeing QoS requirement. Given a set of clients (end-users) in a region, each client has a traffic demand for Internet access. Our concern is to find out minimal number of APs and their locations, so that both fault tolerance and QoS constraints can be satisfied. That is, when there is no AP failure, all clients' traffic demands should be met. When one AP fails, the clients it serves shall switch to other APs and a certain percentage of traffic demands of these clients affected shall still be met. We proposed a heuristic algorithm to solve this problem. Firstly we place minimal number of APs to ensure that connection requirements and per-client degrading traffic demand can be met. Secondly, we continue to add APs to meet per-client normal traffic demand. Finally, we place more APs to tolerate failure of the APs placed in the first step. Simulation are conducted to show the performance of our proposed method.

In wireless local area networks (WLANs) made up of Extended Service Sets, access point (AP) selection is a key issue to improve the network performance and balance the traffic load. WLANs operating in the shared Industrial, Scientific and Medical band can benefit from the use of cognitive radio (CR) techniques to enable dynamic access to spectrum holes that are free from interference. In this paper, we propose an optimal Green AP Selection (GAPS) scheme, in which AP selection is optimized to maximize the system throughput while minimizing the energy consumption, for multi-rate WLANs enhanced by CRs. Different from most existing AP selection schemes, GAPS takes into account of the state transition tendency of APs and the influence of Automatic Rate Fallback mechanism in the Distributed Coordination Function. The AP selection problem is formulated as a restless bandit problem and solved by the primal-dual index heuristic algorithm based on first order relaxation to yield the GAPS scheme with the "indexability" property and hence a low complexity. GAPS is further divided into offline computation, which accounts for the bulk of the computations, and online selection, with a low complexity to facilitate implementation. Extensive simulation results illustrate the significant performance improvements of GAPS compared with existing AP selection schemes in different scenarios.

There has been widespread deployment of IEEE 802.11 wireless local area networks (LANs) because of high demand from mobile terminals, such as iPod and Android terminals. With the increasing energy consumption of the wireless LANs, the development of power saving technologies incorporated into the wireless LANs have become important. In wireless LANs, access points (APs) continuously consume the power regardless of the communication. Therefore, we have proposed the Radio-On-Demand (ROD) wireless LAN, which provides power saving schemes on the basis of the utilization of wireless LANs. In this study, we particularly focus on the power saving scheme of the APs, and propose the decentralized association management of ROD wireless LANs. In our scheme, an AP assigns associated stations (STAs) to new APs before switching to sleep mode. Simulation results show that the proposed scheme can realize sufficient power saving.

The effect of the dimensions of an arbitrary indoor environment on the coherence bandwidth of the wireless wideband channel as well as its impact on a smart antenna beamformer patterns is investigated. A deterministic ray-tracing channel modelling tool is first used to evaluate and compare the Power-Delay-Angle Profile (PDAP) for two arbitrary indoor architectures of different dimensions as well as other parameters of interest like the delay spread, the angular spread and approximately estimating the coherence bandwidth. The coherence bandwidth is also evaluated using the frequency autocorrelation function and compared with the approximate calculation. The frequency dependence of the weights and patterns of a null steering beamformer, serving four simultaneous users, are compared for both architectures. A weight interpolation algorithm is then proposed targeting infrastructure Wireless Local Area Network (WLAN) applications in indoor scenarios following the IEEE802.11a or HIPERLAN/2 standards. It is shown that for a small indoor environment with a large coherence bandwidth, the beamformer weights can be estimated two or three times over a band of 52 OFDM subcarriers and interpolated for the rest of the subcarriers. For a large indoor environment with a small coherence bandwidth the weights need to be estimated every two or three subcarriers.

Chaotic deployment of Wireless Local Area Networks (WLANs) in dense urban areas is one of the common issues of many Internet Service Providers (ISPs) and Wi-Fi users. It results in a substantial reduction of the throughput and impedes the balanced distribution of bandwidth among the users. Most of these networks are managed independently and there is no cooperation among them. Moreover, the conventional association mechanism that selects the Access Points (APs) with the strongest Received Signal Strength Indicator (RSSI) aggravates this situation. In this paper, we present a versatile near-optimal solution for the fair bandwidth distribution over virtualized WLANs through dynamic association control. The proposed scheme is called ACO-PF, which is developed on top of Ant Colony Optimization (ACO) as a meta-heuristic technique to provide Proportional Fairness (PF) among the greedy clients. In fact, it presents a generic and centralized solution for ISPs that are using a common, virtualized or overlapped WLAN infrastructure for serving their customers. We have evaluated the efficacy of ACO-PF through numerical analysis versus popular existing schemes for both downlink and uplink scenarios. Our proposed technique has less complexity in terms of the implementation and running time for largescale WLANs and it can be easily developed and customized for different objective functions. In addition, it is implemented in a testbed environment to investigate the key challenges of real deployment scenarios.

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.

While the wireless local area network (WLAN) has been the most common technology for static indoor wireless services, its applications has limited performance in seamless mobile services because of its inherent static service transaction mechanisms. In this paper, we propose a mobility provisioning handoff method called dual cross-linking method to support seamless services in WLAN. A mobile node (MN) has two wireless interfaces and access points (APs) are controlled by a mobility management (MM) agent. In the area where the service areas of two adjacent APs are overlapped, one wireless interface is used to maintain the wireless services while the other interface searches for a next available AP. After finding a new AP, MN forms dual communication path from the MM to the MN so that the MN is ready to move to a newly found AP service area without service loss. Once the MN is moved to a new AP area, the first interface is disconnected leaving only one interface connection. It was proved that the proposed method can effectively reduce the handoff delay and packet loss through the analysis.

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

This paper presents an AP (Access Point) placement framework considering indoor location-awareness and AP-based WLAN (Wireless Local Area Networks) performance enhancement. We first develop four objective functions that yield objective goals significant to the optimal AP placement in terms of location-awareness and network performance factors. Then, we develop three meta-heuristic algorithms based on simulated annealing, tabu search, and genetic algorithm. These algorithms generate a near-optimal solution for a given objective function. The performance of the AP placement framework presented in this paper is measured under the environments simulating indoor spaces, and numerical results obtained by experimental evaluation of proposed objective functions and algorithms confirm that the proposed AP placement framework can achieve a near-optimal solution to a given objective function.