Improving Ieee 802.11 Wlan Handoff Latency by Access Point-Based Modification

IEEE 802.11 WLAN provides multimedia services like live telecast, video streaming, video conferencing, Voice over IP (VoIP) to its users. For deployment of these fast real time services, it needs stringent Quality of service (QoS) requirement such as delay time less than 150ms for VoIP, and packet loss rate of 1%. The mobility service for users come with cost of handoff process required when mobile stations get connected from 1 Access point (AP) to another for continuous service. In existing 802.11 IEEE handoff procedure, the scanning phase can exceed duration of 200ms and packet loss can exceed 10%. Thus, proposed methodology focuses on achieving reduced overall handoff latency by implementing handoff delay duration less than 150ms which is the need for seamless service in IEEE 802.11 WLAN

Towards the Quality of Service for VoIP traffic in IEEE 802.11 Wireless Networks

The usage of voice over IP (VoIP) traffic in IEEE 802.11 wireless networks is expected to increase in the near future due to widely deployed 802.11 wireless networks and VoIP services on fixed lines. However, the quality of service (QoS) of VoIP traffic in wireless networks is still unsatisfactory. In this thesis, I identify several sources for the QoS problems of VoIP traffic in IEEE 802.11 wireless networks and propose solutions for these problems. The QoS problems discussed can be divided into three categories, namely, user mobility, VoIP capacity, and call admission control. User mobility causes network disruptions during handoffs. In order to reduce the handoff time between Access Points (APs), I propose a new handoff algorithm, Selective Scanning and Caching, which finds available APs by scanning a minimum number of channels and furthermore allows clients to perform handoffs without scanning, by caching AP information. I also describe a new architecture for the client and server side for seamless IP layer handoffs, which are caused when mobile clients change the subnet due to layer 2 handoffs. I also present two methods to improve VoIP capacity for 802.11 networks, Adaptive Priority Control (APC) and Dynamic Point Coordination Function (DPCF). APC is a new packet scheduling algorithm at the AP and improves the capacity by balancing the uplink and downlink delay of VoIP traffic, and DPCF uses a polling based protocol and minimizes the bandwidth wasted from unnecessary polling, using a dynamic polling list. Additionally, I estimated the capacity for VoIP traffic in IEEE 802.11 wireless networks via theoretical analysis, simulations, and experiments in a wireless test-bed and show how to avoid mistakes in the measurements and comparisons. Finally, to protect the QoS for existing VoIP calls while maximizing the channel utilization, I propose a novel admission control algorithm called QP-CAT (Queue size Prediction using Computation of Additional Transmission), which accurately predicts the impact of new voice calls by virtually transmitting virtual new VoIP traffic

Hybrid Hand-off Scheme for Performance Improvisation of Wireless Networks

Wireless systems administration is turning into an inexorably significant and well known method of giving worldwide data access to clients progressing. Handoff, the procedure where portable hubs select best passageway accessible to move information and its postpones make a major issue. A great deal of research has been done in most recent years to diminish the handoff delays happen in the various degrees of  WLAN correspondence. Because of the versatility of handoff, significant viewpoint in WLAN and cell correspondences are substantially more significant. Because of constrained scope of APs, WLAN likewise gives adequate data transmission to continuous spilling administrations. In this research article, various handoff plans are proposed to diminish the hand-off idleness and bolster quick hand-off in IEEE 802.11arcchitecture of wireless networks. In this article, we survey these quick handoff plots subjectively. In this work it is to make accessible preparation for prospect research on lessening the handoff inertness and give accentuation on necessity of quick handover for consistent network

Experimenting with commodity 802.11 hardware: overview and future directions

The huge adoption of 802.11 technologies has triggered a vast amount of experimentally-driven research works. These works range from performance analysis to protocol enhancements, including the proposal of novel applications and services. Due to the affordability of the technology, this experimental research is typically based on commercial off-the-shelf (COTS) devices, and, given the rate at which 802.11 releases new standards (which are adopted into new, affordable devices), the field is likely to continue to produce results. In this paper, we review and categorise the most prevalent works carried out with 802.11 COTS devices over the past 15 years, to present a timely snapshot of the areas that have attracted the most attention so far, through a taxonomy that distinguishes between performance studies, enhancements, services, and methodology. In this way, we provide a quick overview of the results achieved by the research community that enables prospective authors to identify potential areas of new research, some of which are discussed after the presentation of the survey.This work has been partly supported by the European Community through the CROWD project (FP7-ICT-318115) and by the Madrid Regional Government through the TIGRE5-CM program (S2013/ICE-2919).Publicad

Channel Scanning and Access Point Selection Mechanisms for 802.11 Handoff: A Survey

While the cellular technology has been evolving continuously in recent years and client handoffs remain unnoticed, the 802.11 networks still impose an enormous latency issue once the client device decides to roam between the Access Point (AP). This latency is caused by many factors reckoning on scanning the channels and searching for APs with better signal strength. Once data from all the nearby APs has been collected, the client picks the most suitable AP and tries to connect with it. The AP verifies if it has enough capability to serve the client. It also ensures that the client has the required parameters and supported rates to match with the AP. The AP then processes this request, generates a new Association ID and sends it back to the client, thereby granting access to connect. Throughout this re-association process, the client fails to receive or send any data frames and experiences a lag between leaving the old and associating with a new AP. Originally, 802.11 authentication frames were designed for Wired Equivalent Privacy protocol, but later it was found to be insecure and thus got depreciated. Keeping these security aspects concerning shared key authentication in mind, few additional drafts were introduced by IEEE that concerned many key exchanges between the devices. IEEE 802.11r was introduced in 2008 that permits wireless clients to perform faster handoff along with additional data security standards. The key exchange method was redefined and also the new security negotiation protocol started serving wireless devices with a better approach. This enables a client to set up the Quality of Service state and security on an alternative AP before making a transition which ends up in minimal connectivity losses. Although this was an excellent step towards minimizing the service disruption and channel scanning, failure to remain connected with consecutive suitable APs within the minimum time continued to be a challenge. Different manufacturers use their custom-built methodology of handling a client handoff and hence the latency costs differ based on the type of handoff scheme deployed on the device. This thesis focuses on the foremost economical researches throughout recent years which targets minimizing the delays involved with channel scanning and AP selection. A wide sort of enhancements, whether it is on a client device or the AP, has been discussed and compared. Some modifications are associated with enhancing channel scan period or using beacons, and probe requests/responses in an efficient manner. Others concentrate on modifying the device hardware configuration and switching between Network Interfaces. Central controllers are a solution to handoff delays that may track the status of each device within the network and guide them to provide the appropriate Quality of Service to the end-users

Fast and seamless mobility management in IPV6-based next-generation wireless networks

Introduction -- Access router tunnelling protocol (ARTP) -- Proposed integrated architecture for next generation wireless networks -- Proposed seamless handoff schemes in next generation wireless networks -- Proposed fast mac layer handoff scheme for MIPV6/WLANs