Anindita Kundu

Performance study of mobile WiMAX network with changing scenarios under different modulation and coding

WiMAX—the Worldwide Interoperability for Microwave Access is a promising technology for offering high-speed data, video and multimedia services over mobile platform evolving toward all IP networks. The increasing demand of WiMAX for VoIP and high-speed multimedia is due to the simplicity of installation and cost reduction compared with the traditional wired DSL cable. The challenges to service providers lie with the Quality of Service (QoS) under varying fading environment while at the same time maximizing for resource utilization. In this paper, a rigorous and comprehensive performance study of mobile WiMAX has been made with respect to adaptive modulation and coding techniques considering the variation in the speed of the mobile, path-loss, scheduling services and application type for comparing with the fixed type of modulations. The OPNET 14.5.A modeler for WiMAX platform has been used as simulator for adaptation at the physical layer of the transmission in WiMAX OFDMA structure. Observation reveals that dynamic adaptation of modulation and coding schemes based on channel condition enables better QoS while consuming low overall bandwidth of the system. Copyright

A tradeoff pricing strategy using AHP for revenue maximization in WiMAX networks

Pricing plays a crucial role in trading any resource or service in the existing Broadband Wireless Access system i.e. WiMAX. Through a proper pricing strategy, a wireless service provider would like to achieve the highest revenue, while the end users would like to achieve the highest satisfaction from service usage. In order to make it feasible, in this paper we propose a tradeoff policy between the user satisfaction and profit of the service providers. In addition, we also propose a Call Admission Control (CAC) mechanism to control various level of Quality of Service (QoS) guarantee of the WiMAX service classes viz. UGS, rtPS, nrtPS and BE. Analytic Hierarchy Process (AHP) is used to prove the consistency of the assumed order of preference of the various QoS parameters for each service classes. Simulation results shows that our proposed tradeoff price maximizes the revenue of the service providers as it provides more user satisfaction or higher level of QoS guarantee to the end users.

Comparison of VoIP Performance over WiMAX, WLAN and WiMAX-WLAN Integrated Network Using OPNET

Voice over IP is expected to be in practice in the next generation communication networks. The target of this paper is to analyse its performance in the next generation networks. Among the most competing networks like WiMAX, Wifi, etc., WiMAX having higher bandwidth accommodates more users but with degraded performance. Hence, an integrated network using WiMAX backbone and WLAN hotspots has been developed and VoIP has been setup using SIP. Since, OPNET 14.5.A provides a real life simulation environment, it is chosen as the simulation tool. Quality of the service is critically analysed with parameters like jitter, MOS and delay for various voice codecs. Finally, it is concluded that the WiMAX-WLAN integrated network provides improved and optimal performance over WLAN and WiMAX network with respect to network capacity and quality of service.

Herb and Drug Interaction

Abstract Herbal medicines have been widely used since ancient times for the treatment of various ailments, and are now gaining popularity worldwide as complementary or alternative treatments for a variety of diseases. Since herbal medicines are regarded as safe, they are often coadministered with many prescribed drugs, and thereby arises the potential of herb–drug interactions (HDIs). Herbal drugs contain more than one pharmacologically active ingredient, which also contributes to HDIs. Simultaneous use of herbs may increase or decrease the effect of prescribed drugs, which can have very serious consequences. The possibility of HDIs had been largely ignored, but the finding that grapefruit juice could impair drug metabolism forced the scientific fraternity to look at the problem more closely. These interactions could be ascribed to both pharmacokinetic and/or pharmacodynamic mechanisms. A significant proportion of reported HDIs are of pharmacokinetic origin, arising from the effects of herbal medicines on metabolic enzymes and/or transporters. Pharmacokinetic alterations may result in changes in absorption, distribution, metabolism, and excretion of the concomitantly prescribed drugs. These changes are clinically very significant as pharmacokinetic parameters such as the area under the plasma concentration–time curve, the maximum plasma concentration, or the elimination half-life of the concomitant drug alter. Induction or inhibition of metabolic enzymes such as cytochrome P450 (CYP3A4, CYP2C9, CYP1A2) and modulation of efflux transporters (P-glycoproteins) are usually the common mechanisms involved in pharmacokinetic interactions. St. Johns wort (SJW; Hypericum perforatum ) was a widely used herbal medicine for the treatment of affective disorders such as depression and anxiety, until its propensity to cause drug interactions was known. Its active constituents such as hyperforin and amentoflavone induced intestinal P-glycoprotein and hepatic CYP3A4 enzyme, which markedly increased the metabolism of their cosubstrates. SJW is a potent uptake inhibitor of neurotransmitters such as serotonin, norepinephrine, and dopamine. In combination with other drugs that may elevate serotonin levels (serotonin reuptake inhibitors), SJW may contribute to serotonin syndrome, a potentially life-threatening adverse drug reaction. Thus to increase the safety of herbal drug usage the potential for HDI should always be assessed in the preclinical safety assessment phase of the drug development process. More clinically relevant research is also necessary in this domain as the present information on HDI is insufficient for clinical applications.

Coverage extension and power optimization for closed group femto cells in BWA network

In todays world 70-90% wireless communication occurs inside the building area. However, due to high wallpenetration loss the signal quality falls below the desired level. Therefore, low power femto base stations are deployed inside the buildings to enhance the indoor coverage and signal strength. In this paper, we have considered a building area located at the cell edge. In the first part of the paper, we have observed the variation of signal to interference plus noise ratio (SINR), packet loss rate and throughput for varied user density and number of channels. However, a huge number of femto cells may create significant amount of interference. Hence, the effect of the interference scenario is discussed and a power optimization algorithm to reduce the cross layer interference is proposed in the rest of the paper. After deploying power optimized femto cells, it is observed that the signal quality within the building has improved significantly.

Design and implementation of a cognitive channel allocation algorithm for BWA system

The practical feasibility of any proposed algorithm could be tested only by hardware implementation of the algorithm. However, in cases involving wireless infrastructure based networks, hardware implementation may be very costly and time consuming. Hence, software simulations are used for these cases. In this paper, we have discussed the approach to be taken to implement any algorithm in any real time simulator. As a test case, we have implemented a simple infrastructure based centralized cognitive channel allocation algorithm for WiMAX BWA system under QualNet 5.0 software. The performance of the algorithm is then validated in terms of Spectrum Utilization and System Throughput for both Poisson and Pareto Arrival Rate of the end users. The results are further compared with results obtained from MATLAB 7.3.0. Unlike MATLAB, the impact of the lossy environment and layered architecture of the nodes is embedded in the results obtained from Qualnet. A fall of 4% in Spectrum Utilization and 3.8% in Throughput is observed in Qualnet compared to MATLAB.

Buffered non-random channel access method for better QoS of cognitive users

Cognitive Radio Networks allow opportunistic spectrum usage by the cognitive users leading to better spectrum utilization. The spectrum utilization however depends on the channel access method adopted and the access of the channel by the primary and the cognitive users. In this paper, a non-random channel access method with dedicated channels for the primary users has been proposed which buffers the requesting cognitive users when all channels are busy. A four dimensional Continuous Time Markov Chain (CTMC) has been developed to analyze our proposed algorithm. The performance of the algorithm has been compared with the existing non-random channel access method and about 71% improvement has been achieved in the Call Blocking Probability while the Channel Utilization and Call Dropping Probability remains almost unchanged.

Load Balancing with Reduced Unnecessary Handoff in Hierarchical Macro/Femto-cell WiMAX Networks

The hierarchical macro/femto cell WiMAX networks are observed to be quite promising for mobile operators as it improves their network coverage and capacity at the outskirt of the macro cell. However, this new technology introduces increased number of macro/femto handoff which inturn may affect the system performance. Users moving with high velocity or undergoing real-time transmission suffers degraded performace due to huge number of unnecessary macro/femto handoff. Our proposed handoff decision algorithm eliminates the unnecessary handoff while balancing the load of the macro and femto cells. The performance of the proposed algorithm is analyzed using Continuous Time Markov Chain (CTMC) Model. In addition, we have also contributed a method to determine the balanced threshold level of the received signal strength (RSS) from macro base station (BS). The balanced threshold level provides equal load distribution to the macro and femto BSs. The balanced threshold level is evaluated based on the distant location of the femto cells for small scaled networks. Numerical analysis shows that threshold level above the balanced threhold results in higher load distribution to the femto BSs.

Reducing Hand-Off Latency in WiMAX Network Using Cross Layer Information

With the growing demand for wireless Internet services and advancement in broadband wireless technologies, seamless hand-off has become a crucial factor in quality of service aware networks. The hierarchical WiMAX network model gives low hand-off latency but requires centralized control approach which introduces system overhead and increased packet end-to-end delay. The flat architecture model reduces system overhead and packet end to end delay at the cost of higher hand-off latency. Hence, a scheme to reduce hand off latency in flat architecture model is proposed. The proposed scheme utilizes information provided by the Medium Access Control (MAC) layer regarding hand-off in order to minimize network layer hand off delay. With the help of simulation using OPNET Modeler, it is shown that the new scheme decreases the hand-off latency while causing no extra overhead to the WiMAX network.