Shahzad A. Malik

Modeling routing overhead generated by wireless reactive routing protocols

In this paper, we have modeled the routing overhead generated by three reactive routing protocols; Ad-hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR) and DYnamic MANET On-deman (DYMO). Routing performed by reactive protocols consists of two phases; route discovery and route maintenance. Total cost paid by a protocol for efficient routing is sum of the cost paid in the form of energy consumed and time spent. These protocols majorly focus on the optimization performed by expanding ring search algorithm to control the flooding generated by the mechanism of blind flooding. So, we have modeled the energy consumed and time spent per packet both for route discovery and route maintenance. The proposed framework is evaluated in NS-2 to compare performance of the chosen routing protocols.

Modeling routing overhead generated by wireless proactive routing protocols

In this paper, we present a detailed framework consisting of modeling of routing overhead generated by three widely used proactive routing protocols; Destination-Sequenced Distance Vector (DSDV), Fish-eye State Routing (FSR) and Optimized Link State Routing (OLSR). The questions like, how these protocols differ from each other on the basis of implementing different routing strategies, how neighbor estimation errors affect broadcast of route requests, how reduction of broadcast overhead achieves bandwidth, how to cope with the problem of mobility and density, etc, are attempted to respond. In all of the above mentioned situations, routing overhead and delay generated by the chosen protocols can exactly be calculated from our modeled equations. Finally, we analyze the performance of selected routing protocols using our proposed framework in NS-2 by considering different performance parameters; Route REQuest (RREQ) packet generation, End-to-End Delay (E2ED) and Normalized Routing Load (NRL) with respect to varying rates of mobility and density of nodes in the underlying wireless network.

Vertical Handover Necessity Estimation Based on a New Dwell Time Prediction Model for Minimizing Unnecessary Handovers to a WLAN Cell

In this work, we devise a vertical handover necessity estimation (HNE) method to minimize unnecessary handovers for a mobile node (MN) entering a WLAN cell. The method relies on a new model for prediction of dwell time and computation of certain threshold values. By comparing the predicted dwell time with those thresholds, a MN is able to make decision whether it should perform handover to a WLAN cell, while keeping the probability of handover failure and probability of unnecessary handover within bounds. Simulation results obtained from Monte-Carlo experiments prove validity of the proposed model. We also compare this model with existing models for minimizing unnecessary handovers. We further enhance the analytical model by incorporating the throughput gain in HNE and show that this can further optimize handover decision in heterogenous networks.

A dynamic non-circular iris localization technique for non-ideal data

Display Omitted Robust iris inner contour localization within a sliding window.A fast and reliable technique for the iris outer contour localization.Iris contours regularization.Tolerance to rotated-iris images, specular reflections, hair, eyelids, and glasses.Applicable in real-time applications. Iris localization plays a decisive role in the overall iris biometric systems performance, because it isolates the valid part of iris. This study proposes a reliable iris localization technique. It includes the following. First, it extracts the iris inner contour within a sliding-window in an eye image using a multi-valued adaptive threshold and the two-dimensional (2D) properties of binary objects. Then, it localizes the iris outer contour using an edge-detecting operator in a sub image centered at the pupil center. Finally, it regularizes the iris contours to compensate for their non-circular structure. The proposed technique is tested on the following public iris databases: CASA V1.0, CASIA-Iris-Lamp, IITD V1.0, and the MMU V1.0. The experimental and accuracy results of the proposed scheme compared with other state-of-the-art techniques endorse its satisfactory performance.

Performance evaluation of transport layer protocols for video traffic over WiMax

With a variety of access technologies available, the demand for mobile multimedia applications has increased enormously. Supporting these multimedia applications with varied quality of service (QoS) requirements while maximizing the resource utilization is a challenging task. One important factor is the transport protocol that significantly affects the offered QoS and efficient utilization of network resources in the inherently varying transmission conditions due to the wireless medium. Currently most of the multimedia applications use UDP as the main transport layer protocol. However, UDP performance has not been satisfactory in meeting the varied QoS of diverse multimedia applications. A number of new protocols are being developed to meet the diverse needs of emerging multimedia applications. SCTP and DCCP are two important developments that are being considered in this regard. In this paper, through simulations, performance of UDP, SCTP and DCCP protocols has been analyzed for the transport of MPEG-4 video traffic over WiMAX as underlying access technology. Considering single cell WiMAX network, performance metrics such as throughput, delay and jitter have been determined for each of the three protocols in varying WiMAX network topologies/scenarios. On the basis of this study, it has been found that both SCTP and DCCP outperform UDP by large extent. Further, DCCP performance is better than SCTP in terms of delay and jitter.

An Architecture for Exploiting Multihoming in Mobile Devices for Vertical Handovers & Bandwidth Aggregation

In recent years, mobile devices with multihoming capabilities i.e. equipped with multiple network interfaces have gained large scale popularity. This multihoming capability enables the mobile devices to connect with multiple diverse access networks simultaneously. However, networking protocol stack implemented in current devices is not capable of exploiting the availability of multiple network interfaces. Multihoming can be used to provide two important services: vertical handovers and bandwidth aggregation. Vertical handover enables a multihomed device to switch its connectivity from one access network to another access network without disrupting the communication session. Bandwidth aggregation enables multihomed device to achieve higher throughput by establishing simultaneous connections over multiple available network interfaces. A number of solutions have been proposed to exploit multihoming for vertical handovers and bandwidth aggregation. However, most of these solutions either require the support of additional network entities such as host agent, foreign agent, mobility gateway, proxy, etc. or they require changes in current widely deployed protocol stack in operating system kernels. Dependence on either network operator, administrator or operating system vendors hinders the large scale deployment of these solutions. This paper presents an end-to-end architecture that offers the vertical handover and bandwidth aggregation services to TCP applications. This architecture neither requires any additional network entity nor it requires the changes in current networking protocol stack in operating system kernels. The paper presents the design, implementation and performance analysis of the proposed architecture.

A comparative study of power control strategies for soft handover in UTRA FDD WCDMA system

This paper analyzes the potential benefits of using different schemes to control base station power during soft handover for UTRA WCDMA downlink. Balanced downlink power control, used to limit control power drifting, and the site selection diversity technique (SSDT) power control are compared with hybrid power control. A hybrid scheme switches dynamically from balanced power control to site selection diversity power control to decrease the base station power during congestion. The objective is to find out whether there is any additional improvement in cellular coverage and performance using these schemes. Total base station transmission power, individual traffic channel power for each mobile station and outage time are used for comparison.

Downlink capacity and performance issues in mixed services UMTS WCDMA networks

Capacity and performance issues in UMTS FDD WCDMA system for the support of mixed heterogeneous services are investigated. The focus is on the downlink with traffic corresponding to UMTS quality of service (QoS) classes. After an initial capacity evaluation on a single service basis, the work is directed to assess the system performance in mixed services. The study aims at discerning the mutual interactions that exist among the services and evaluating the relationships between system performance and service characteristics. The emphasis is on how system performance and service behavior are inter-related in mixed traffic configurations and thus get an insight into resource control. The results are collected in terms of percentage of satisfied users, user blocking, probability of outage, throughput and delay. The analysis indicates that high data rate users are the most demanding and care must be taken at resource allocation to achieve QoS targets.

Resource allocation for multimedia services on the UMTS downlink

Efficient radio resource allocation techniques are vital for providing acceptable capacity over the UMTS radio access network (RAN). Interaction among services and power requirements according to service bit rates can seriously limit the capacity. This work presents a resource allocation framework based on service differentiation and analyzes the capacity benefits achieved through service prioritization and dynamic rate adaptation. Conversational, streaming, interactive and background service classes are considered in the investigation. Real time (RT) services are offered over dedicated radio access bearers. Non real time (NRT) services use downlink shared channels to achieve multiplexing and better resource utilization. Combining prioritized connection admission control based on service class to minimize interference and dynamic rate adaptation for NRT services leads to significant improvements in overall system capacity. Without these capacity enhancement techniques the UNITS downlink can be fairly limited by interference and resource availability in the presence of multiple services operating at various rates and requiring diverse QoS.

Performance Evaluation of DCCP and SCTP for MPEG4 Video over Wireless Networks

In this paper our focus is on the performance of two new transport protocols DCCP and SCTP; the emphasis is to determine which protocol can better meet the Quality of Service (QoS) for MPEG4 video over wireless local area network. Based on results obtained in this analysis it is observed that both SCTP and DCCP achieved better throughput than UDP. For video traffic load of 4 Mbps, throughput achieved by both SCTP and DCCP is almost 100% without expressing any packet loss. With the increase of video traffic load of 5 Mbps and beyond DCCP maintains its throughput and it shows minimum packet loss but SCTP losses its performance. Delay behavior of DCCP also indicates that its performance is better than SCTP. According to our experimental results DCCP better satisfies the quality of service than SCTP for transport of multimedia (video) traffic.