Partha Bhattacharjee

Study and Analysis of Cellular Wireless Networks with Multiclass Traffic

In this paper, the traffic characteristics have been studied by collecting traces from a CDMA2000 cellular wireless network that provides services like messaging, video streaming, e-mail, internet, song downloading. The traces record call activities including call initiation time, termination time, originating node identification number, packet size, home station id, foreign station id (when roaming), handoffs. Traffic parameters namely, call inter-arrival times and call holding times were estimated using statistical methods. The results show that call inter-arrival time distribution in this CDMA cellular wireless network is heavy-tailed and can be modeled by gamma as well as weibull distributions and are asymptotically long-range dependent. It is also found that the call holding times are best fitted with lognormal distribution and are not correlated. An analytical model based on our observations for performance measures of a circuit-switched cellular wireless network with multiclass traffic sources is also proposed.

Manganese doped Zinc oxide thin film hydrogen gas sensor at reduced operating temperature

During the past few decades, semiconductor metal oxide (SMO) gas sensors have become a prime technology in several domestic, commercial, and industrial gas sensing. The semiconductor properties of zinc oxide along with its dopant remain to be trapped fully in its application as gas sensor. With the advent of nanotechnology, miniaturization and high sensitivity happens to be a key issue in sensor fabrication. Most of the SMO gas sensors fabricated by nanotechnology process operate at high temperature. This paper gives a new insight to hydrogen gas sensor characteristics, by reducing the operating temperature of hydrogen (H2) sensor, fabricated from the nano particle of manganese doped zinic oxide(ZnO), synthesized by chemical precipitation method.

Design and dimensioning of an edge router using Markov model

This paper presents the formulation, modelling and analysis of network traffic for the purpose of designing an edge router. Presuming packet arrival in Poissons process and departure or service time distribution to be exponential, a Markov model has been developed. The stochastic characteristics of the traffic has been monitored and studied over long durations. Traffic data was captured from internet backbone. Different design parameters like buffer capacity, outgoing link speed and various other key parameters have been derived. Additionally, an algorithm has been suggested to manipulate the weights of the queues dynamically in a weighted round robin scheduling, thereby changing the packet departure rate of the flows. The algorithm eventually provides a control over the load factors and the probability of packet drop of the flows as per the need of quality of service and differentiated service.

Mathematical Modeling for Evaluation of Quality of Service Parameters in Next Generation Cellular Wireless Networks

In this paper, a mathematical model has been developed for cellular wireless network with Gamma inter-arrivals and general call holding times. Measurement based studies have shown that Poisson assumption averages out the traffic characteristics to a single parameter (i.e. average rate) which does not represent the real dynamics involved in the process. The actual traffic pattern in the next generation cellular wireless networks is more complex for the presence of multiple services. This work evaluates the QoS parameters from a more pragmatic model for future cellular wireless networks.

New admission control algorithm based on effective bandwidth for a multi-class network

This paper presents the analysis and estimation of effective bandwidth of a router, handling multi-class traffic. Analysis is done with marginal buffering as well as large buffers. Performance of a periodic on-off source is compared with that of a Poisson¿s source with marginal buffering. Bandwidth requirement of the sources for a given Quality of Service is worked out. The analysis is then extended to routers with large buffers. Estimated performance parameters based on effective bandwidth are found out mathematically. Trade-off between required bandwidth and buffer provisioning is shown. A humble admission control algorithm, based on the measurement of certain parameters of the incoming flows is proposed. Finally the efficacy of the algorithm is shown by comparing its performance with the calculated bounds of the probability of overflow.

Design and development of active endoscope using shape memory alloy actuators

Minimally invasive surgery is well-accepted in the society because it involves lesser operative trauma for a patient than an equivalent invasive procedure. It causes less pain and scarring, faster recovery, and reduces the incidence of post-surgical complications. An endoscope is considered as one of the most powerful diagnostic and therapeutic tool for dealing abnormalities inside the body. This article aims at deciphering a solution to the problem of passive bending of conventional endoscopes by introducing a concept of active bending by using shape memory alloy (SMA) micro actuators. The developed prototype has many small segments connected to one another by a ball and socket joint, actuated independently which gives rigidity and high degree of manoeuvrability to the scope. The article proposes an algorithm for traversing the scope inside the body and addresses a very important issue of taking it out without causing any damage to the track. A graphical interface gives the practitioner a number of options to orient the scope [on the basis of three-dimensional (3D) discrete points reached by the tip and segment orientations based on camera image] and simultaneously shows a 3D view of orientation of the full scope.

Analysis of Cellular Wireless Networks with Non-Classical Traffic and Channel Reservation

Abstract This paper describes a traffic model for cellular wireless network with non-classical traffic (i.e., gamma inter-arrivals and general service times). Empirical studies have shown that electromagnetic propagation condition, irregular users’ behaviours, management policies, equipment failures, charging capacity of battery and so on have significant influence in call drops. Hence, the exponential assumption for both the inter-arrival and service times does not always hold true, as it does not represent the real dynamics involved in an operational network. The proposed Ek/G/C model takes into account the non-exponential inter-arrival time and service time distributions and gives a more pragmatic model for future cellular wireless networks. The performance of the proposed model of the cellular wireless network has been re-evaluated with channel reservation using both classical and non-classical traffic. The results show that non-classical model gives better approximation of the system performance in terms of the blocking probabilities.

Shape Memory Alloy actuated arm for traversing complex trajectories

Steering and guiding an endoscope in a patients body has been a challenge for doctors for many years now. Present endoscopic technology allows passive bending of the scope by one or more cables attached to the tip. Bending motions of the tip of a conventional endoscope are controlled from outside the body by wire traction. Therefore, precise operation of the endoscope is difficult in areas of complex shape such as the intestine. Furthermore, patients suffer pain during a procedure with an endoscope. This paper aims at deciphering a solution for the above problems by introducing the concept of active bending of the endoscope with Shape Memory Alloy (SMA) micro-actuators. A Teflon prototype is developed to establish the concept. Many Teflon segments are connected with ball and socket joint and each segment bending is controlled independently which gives high degree of maneuverability to the device. The dexterous device prototype developed is capable of following complex trajectories and can steer tight bends. The same concept of bending can be extended to devices like borescopes, to be used for internal visualization of mechanical systems such as jet engines, turbines, satellites etc. These devices are again expected to follow complex trajectories with tight bends for visualization of specific areas within the highly integrated structure without dismantling.

A new dynamic guard channel reservation scheme for cellular wireless networks

In this paper, a new dynamic guard channel reservation scheme, based on conditional real-time channel availability, is proposed to achieve better handoff performance and higher utilisation of system resources (radio spectrum) in cellular wireless networks. The proposed scheme has been explained mathematically and studied in a cellular wireless environment. Different performance parameters are measured using the proposed scheme and are compared with those obtained from a fixed guard channel scheme.

Mathematical Modelling for the Design of an Edge Router

This paper presents the formulation, modelling and analysis of network traffic for the purpose of designing an edge router, catering for a large campus. Presuming packet arrival from Poissonpsilas process, and departure or service time distribution to be exponential, a Markov model has been developed. The stochastic characteristics of the traffic has been monitored and studied over long durations through different times of a day and different days of a week. Design parameters like buffer capacity, link speed and various other key parameters for an edge router have been derived. Additionally, an algorithm has been suggested to manipulate the weights of the queues dynamically in a weighted round robin scheduling, thereby changing the packet departure rate of the flows. The algorithm eventually provides a control over the load factors and the probability of packet.