Aresh Dadlani

Multicast Scheduling and Resource Allocation Algorithms for OFDMA-Based Systems: A Survey

Multicasting is emerging as an enabling technology for multimedia transmissions over wireless networks to support several groups of users with flexible quality of service (QoS) requirements. Although multicast has huge potential to push the limits of next generation communication systems; it is however one of the most challenging issues currently being addressed. In this survey, we explain multicast group formation and various forms of group rate determination approaches. We also provide a systematic review of recent channel-aware multicast scheduling and resource allocation (MSRA) techniques proposed for downlink multicast services in OFDMA based systems. We study these enabling algorithms, evaluate their core characteristics, limitations and classify them using multidimensional matrix. We cohesively review the algorithms in terms of their throughput maximization, fairness considerations, performance complexities, multi-antenna support, optimality and simplifying assumptions. We discuss existing standards employing multicasting and further highlight some potential research opportunities in multicast systems.

Adaptive generalized minimum variance congestion controller for dynamic TCP/AQM networks

Generic generalized minimum variance-based (GMV) controllers have been adopted as efficient control mechanisms especially in presence of measurement noise. However, such controllers exhibit degraded performance with change in process dynamics. To overcome this problem, a novel congestion controller based on active queue management (AQM) strategy for dynamically varying TCP/AQM networks known as adaptive generalized minimum variance (AGMV) is proposed. AGMV is the combination of the real-time parameter estimation and GMV. The performance of the proposed scheme is evaluated and compared with its adaptive minimum variance (AMV) counterpart under two distinct scenarios: TCP network with unknown parameters and TCP network with time varying parameters. Simulation results indicate that, in either case, AGMV is able to keep the queue length around the desired point. In addition, the superior performance of the proposed controller has been shown with regard to the PI controller, which is well-known in the AQM domain.

Improved algorithms for leader election in distributed systems

An important challenge confronted in distributed systems is the adoption of suitable and efficient algorithms for coordinator election. The main role of an elected coordinator is to manage the use of a shared resource in an optimal manner. Among all the algorithms reported in the literature, the Bully and Ring algorithms have gained more popularity. In this paper, we describe novel approaches towards improving the Bully and Ring algorithms and also propose the heap tree mechanism for electing the coordinator. The higher efficiency and better performance of our presented algorithms with respect to the existing algorithms is validated through extensive simulation results.

Mean-Field Dynamics of Inter-Switching Memes Competing Over Multiplex Social Networks

This letter characterizes the intertwined behavior of a susceptible-infected-susceptible epidemic model involving multiple mutually exclusive memes, each competing over distinct contact planes of an undirected multi-layer social network, with the possibility of inter-switching. Based on the mean-field theory, we contrast and derive closed-form analytical expressions for the steady-state thresholds that govern the transitions between extinction, co-existence, and absolute dominance of the inter-switchable memes. Moreover, a non-linear optimization formulation is presented to determine the optimal budget allocation for controlling the switching rates to a particular co-existing meme. Validated by simulations, the impact of switching on the tipping thresholds and their implications in reality are demonstrated using data extracted from online social networks.

On modeling optical burst switching networks with fiber delay lines: A novel approach

Optical Burst Switching (OBS) has been widely admitted as a viable candidate for the evolving all-optical network control framework of nowadays Internet core to meet the explosive demand of bandwidth constraints in multimedia and real-time applications. A number of analytical models have been proposed to characterize the behavior of OBS networks. These models, however, do not imitate the actual features of the Fiber Delay Line (FDL) components present in contemporary optical switches. Underscoring the precise behavior of FDLs leads to misleading results regarding major performance measures of OBS networks. While FDLs behavior has been neglected in many studies, as a crude approximation, a few researches characterize FDLs as conventional buffers present in electronic switching systems. In this paper, we provide an inclusive discussion on the features of FDLs, followed by presenting a novel analytical model to realize the inimitable characteristics of FDLs. The proposed network-level model is based on the results of queuing systems with impatient customers and deterministic impatience time. The viability of the proposed model is validated through extensive simulation experiments.

A Probabilistic Characterization of Fault Rings in Adaptively-Routed Mesh Interconnection Networks

With increase in concern for reliability in the current and next generation of multiprocessors system-on-chip (MP-SoCs), multi-computers, cluster computers, and peer-to-peer communication networks, fault-tolerance has become an integral part of these systems. One of the fundamental issues regarding fault-tolerance is how to efficiently route a faulty network where each component is associated with some probability of failure. Adaptive fault-tolerant routing algorithms have been frequently suggested in the literature as means of improving communication performance and fault-tolerant demands in computer systems. Also, several results have been reported on usage of fault rings in providing detours to messages blocked by faults and in routing messages adaptively around the rectangular faulty regions. In order to analyze the performance of such routing schemes, one must investigate the characteristics of fault rings. In this paper, we derive mathematical expressions to compute the probability of message facing the fault rings in the well-known mesh interconnection network. We also conduct extensive simulation experiments using a variety of faults, the results of which are used to confirm the accuracy of the proposed models.

Stability and Immunization Analysis of a Malware Spread Model Over Scale-Free Networks

The spreading dynamics and control of infectious agents primarily depend on the connectivity properties of underlying networks. Here, we investigate the stability of a susceptible- infected-susceptible epidemic model incorporated with multiple infection stages and propagation vectors to mimic malware behavior over scale-free communication networks. In particular, we derive the basic reproductive ratio (R0) and provide results for stability analysis at infection-free and infection-chronic equilibrium points. Based on R0, the effectiveness of four prevailing immunization strategies as countermeasures is studied and compared. The outperformance of proportional and targeted immunization is justified via numerical results.

Mathematical Analysis of Wavelength-Based QoS Management in Optical Burst Switched Networks

With increase in time-critical applications over the Internet, the need for differentiating services has become a major endeavor in research communities. One promising paradigm proposed to support such traffic diversity in the next-generation Internet is Optical Burst Switching (OBS). In the literature, two simple but efficient approaches namely, threshold and wavelength-based techniques have been investigated under the resource allocation-based QoS management scheme as solutions to overcome the bandwidth requirement in the backbone. However, to the best of our knowledge, the wavelength-based technique has not been analytically studied for any arbitrary number of service classes. In this paper, we generalize the wavelength-based technique to support any number of classes. Firstly, we present a novel mathematical model for the wavelength-based technique for real-time and non-real-time service classes. The proposed model is then extended to support any arbitrary number of classes. Simulations conducted at the switch level validate the model.

System Dynamics of a Refined Epidemic Model for Infection Propagation Over Complex Networks

The ability to predict future epidemic threats, both in real and digital worlds, and to develop effective containment strategies heavily leans on the availability of reliable infection spreading models. The stochastic behavior of such processes makes them even more demanding to scrutinize over structured networks. This paper concerns the dynamics of a new susceptible-infected-susceptible (SIS) epidemic model incorporated with multistage infection (infection delay) and an infective medium (propagation vector) over complex networks. In particular, we investigate the critical epidemic thresholds and the infection spreading pattern using mean-field approximation (MFA) and results obtained through extensive numerical simulations. We further generalize the model for any arbitrary number of infective media to mimic existing scenarios in biological and social networks. Our analysis and simulation results reveal that the inclusion of multiple infective medium and multiple stages of infection significantly alleviates the epidemic threshold and, thus, accelerates the process of infection spreading in the population.

Analysis of the Impact of Wavelength Converters on Contention Resolution in Optical Burst Switching

Optical burst switching (OBS) appears to be the best available solution to the ever-increasing demand for Internet bandwidth. As a multifaceted paradigm, it has opened up various motivating challenges in optical networking. Several analytical models regarding optical networking have been proposed in the literature. However, to the best of our knowledge, these models follow an exponential burst length distribution which is unrealistic in the case of threshold-based burst aggregation occurring at edge switches. In this work, we present an insightful model which considers constant burst lengths and study the effect of employing wavelength converters (WC) to the resource utilization and contention resolution policy. We investigate two types of optical switches in terms of availability of WCs in the switch fabric and study their performance through mathematical modeling using the results of queuing theory. We then further extend our investigation by comparing these switches through simulation experiments and thus, confirm our mathematical model. For the purpose of tractability, we also present an approximate model of M/D/c/K queuing system with finite waiting room using an M/D/l/K system.