Shafaq Bashir Chaudhry

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Publications

Shafaq B. Chaudhry, Victor C. Hung, Ratan K. Guha and Kenneth O. Stanley, "Evolutionary Computational Approach for Pareto-Optimal Wireless Sensor Placement." (Submitted).
Abstract: Soon...
Jaruwan Mesit, Ratan K. Guha and Shafaq B. Chaudhry, "3D Soft Body Simulation using Mass-spring System with Internal Pressure Force and Simplified Implicit Integration." In Journal of Computers (JCP). (Accepted).
Abstract: In this paper, we propose a method to simulate soft bodies by using gravitational force, spring and damping forces between surface points, and internal molecular pressure forces. We consider a 3D soft body model composed of mesh points that define the body’s surface such that the points are connected by springs and influenced by internal molecular pressure forces. These pressure forces have been modeled on gaseous molecular interactions. Simulation of soft body with internal pressure forces is known to become unstable when high constants are used and is averted using an implicit integration method. We propose an approximation to this implicit integration method that considerably reduces the number of computations in the algorithm. Our results show that the proposed method realistically simulates soft bodies and improves performance of the implicit integration method.
Shafaq B. Chaudhry and Ratan K. Guha, "Adaptive Connection Admission Control and Packet Scheduling for QoS Provisioning in Mobile WiMAX." In Proceedings of IEEE International Conference on Signal Processing and Communication (ICSPC), 24-27 November, 2007.
Abstract: We propose a connection admission control (CAC) scheme and a packet scheduling algorithm for the IEEE 802.16e-2005 standard for fixed and mobile Broadband Wireless Access systems. In the proposed architecture, CAC will reserve an adaptive temporal channel bandwidth for mobile subscriber stations based on most recent CAC requests to assure seamless handoff of mobile station's connections to another base station. Packet scheduling will allocate physical layer slots to user packets based on the corresponding application's data rate and latency characteristics. Thus, the proposed architecture will provide Quality of Service (QoS) provisioning for real-time and non real-time applications according to their delay and bandwidth requirements as dictated by the service flows defined in the IEEE standard. In our architecture, we consider user satisfaction, fairness condition, channel utilization and packet throughput as important parameters.
Yi Qian, Shafaq B. Chaudhry, and Ratan K. Guha. "Resource Management in WiMAX Networks." In Yang Xiao (ed.), WiMax/MobileFi: Advanced Research and Technology. Auerbach Publications, CRC Press. (to be published in December, 2007)
Abstract: In this chapter, we investigate resource management mechanisms in Worldwide Interoperability for Microwave Access (WiMAX) networks, including subcarrier assignment, adaptive power allocation, and call admission control schemes. Sub- carrier assignment scheme deals with how to allocate subcarriers to form a sub- channel. Adaptive power allocation allows the transmitter to grant different power levels to different subcarriers according to the channel state information. Call admission control highlights how to distribute a subscriber's access band- width over different types of applications such that the QoS requirement of each connection is guaranteed. We focus on orthogonal frequency division multiple access (OFDMA) with time division duplex (TDD) environment, which allows high spectrum utility efficiency on the uplink and downlink channels in asymmet- ric "last-mile" Internet access. We conclude this chapter with the optimization strategy that finds a balance between the revenue of a WiMAX service provider and the satisfaction of WiMAX subscribers.
Shafaq B. Chaudhry, Victor C. Hung and Ratan K. Guha, "Optimal Placement of Wireless Sensor Nodes with Fault Tolerance and Minimal Energy Consumption." In Proceedings of IEEE International Conference on Mobile Adhoc and Sensor Systems (MASS), 9-12 October, 2006.
Abstract: In this paper, an evolutionary algorithm is presented to develop a solution for the variable radii sensor placement optimization problem. Sensor nodes are placed in a sensor field such that maximum coverage of the target region is achieved. Coverage is defined in terms of monitoring points of interest. In point coverage, it is desired to place the sensor nodes such that certain target points in the area to be monitored are efficiently covered. The sensors are assumed to have varying communication and sensing radii within specified ranges. To attain a certain degree of fault tolerance, the network is required to have k-connectivity. Therein, the challenge lies in finding a solution that provides the optimal choice and arrangement of sensor nodes with a minimized overall energy consumption. Our devised algorithm places the sensors to form an energy-efficient and fault tolerant network that provides coverage of the given query points.
Shafaq B. Chaudhry, Ratan K. Guha, Yi Qian and Seema Bandyopadhyay, "A Collision-free MAC Layer Protocol for Event-based Data Gathering in Wireless Sensor Networks." In Proceedings of The Huntsville Simulation Conference (HSC), 26-27 October, 2005.
Abstract: In this paper, we have proposed a collision-free medium access control (MAC) protocol for wide area data gathering applications in wireless sensor networks. The proposed MAC scheme is specifically designed for reactive networks and follows an event-based datagathering paradigm that takes into consideration the spatial and temporal correlations of the process being monitored. Sensors periodically monitor their surroundings and react to the environment either by waking up if an abnormality is detected or by decreasing their sleep cycle if an abnormal trend is detected. Simulation studies show that the proposed scheme performs better than similar existing schemes in terms of network lifetime and the responsiveness of the network to the events of interest.