Sant Sharan Pathak

Complete analysis of MAP/G/1/N queue with single (multiple) vacation(s) under limited service discipline

We consider a finite-buffer single-server queue with Markovian arrival process (MAP) where the server serves a limited number of customers, and when the limit is reached it goes on vacation. Both single- and multiple-vacation policies are analyzed and the queue length distributions at various epochs, such as pre-arrival, arbitrary, departure, have been obtained. The effect of certain model parameters on some important performance measures, like probability of loss, mean queue lengths, mean waiting time, is discussed. The model can be applied in computer communication and networking, for example, performance analysis of token passing ring of LAN and SVC (switched virtual connection) of ATM.

BMAP/G/1/N queue with vacations and limited service discipline

Abstract We consider a finite buffer single server queue with batch Markovian arrival process ( BMAP ), where server serves a limited number of customer before going for vacation(s). Single as well as multiple vacation policies are analyzed along with two possible rejection strategies: partial batch rejection and total batch rejection. We obtain queue length distributions at various epochs and some important performance measures. The Laplace–Stieltjes transforms of the actual waiting time of the first customer and an arbitrary customer in an accepted batch have also been obtained.

Design and performance analysis of code families for multi-dimensional optical CDMA

A code design algorithm for application in multi-dimensional optical code division multiple access (MD-OCDMA) for asynchronous optical fibre communication is proposed. Two-dimensional (2D) wavelength-time or space-time OCDMA and three-dimensional (3D) space-wavelength-time OCDMA are subsets of MD-OCDMA. Some applications and the performance analysis of the algorithm in 2D multipulse per row codes and 3D multipulse per plane codes are shown. In the applications discussed, this design ensures a maximum cross-correlation of ‘1’ between any two codes. The performance metrics studied are the probability of error due to multiple-access interference for different numbers of active users and optimum temporal length for different values of cardinality. The performance analysis shows that the proposed 2D design offers very low probability of error due to multiple-access interference at lower cardinality when compared with other 2D designs using equivalent code dimension. A comparison of the proposed 3D design with an existing 3D design shows better performance at lower cardinality. The 3D designs show better performance when compared with the 2D designs.

Modeling and Coverage Analysis of BS-Centric Clustered Users in a Random Wireless Network

Modeling the irregularities in the locations of cellular base station (BS) using Poisson point process (PPP) has attracted attention in the research community. In existing literature, for coverage analysis the assumption of modeling the locations of users and BSs using independent homogeneous PPP is common. Nevertheless, irregularities in the locations of BS is the effect of traffic-demand-based deployment. Therefore, correlation between the locations of users and BSs is evident. In this letter, we present the coverage analysis for the scenario of BS-centric user clustering. The users are modeled using Poisson cluster process (PCP). The parent points of clusters are assumed to be BSs that are drawn from PPP. Thomas cluster process (TCP) is considered to model the clusters of PCP. The derived expressions of coverage under small scale fading with and without long-term shadowing are validated through simulations. Further, the coverage experienced under TCP becomes the same as that under the assumption of independent PPPs for users and BSs as standard deviation of TCP tends to infinity.

Finite buffer vacation models under E-limited with limit variation service and Markovian arrival process

We consider a finite-buffer single server queue with single (multiple) vacation(s) and Markovian arrival process. The service discipline is E-limited with limit variation (ELV). Several other service disciplines like, Bernoulli scheduling, nonexhaustive and E-limited service can be treated as special cases of the ELV service.

Modelling of Cooperative Spectrum Sensing over Rayleigh Fading Without CSI in Cognitive Radio Networks

It is proved that cooperation among secondary users (SUs) in a cognitive radio network (CRN) greatly improves the spectrum sensing performance. However, modelling and analysis of cooperative spectrum sensing in a CRN over fading channels is an important issue. This paper derives a new fusion rule based on likelihood ratio test which requires exact channel statistics instead of instantaneous channel state information. This scheme provides Neyman–Pearson criteria based optimal sensing while considering both sensing and reporting channels as independently Rayleigh faded. We derive closed form solutions for local probabilities of detection and false alarm by assuming that all SUs perform energy detection, which makes real-time computations simple. Further, closed form solutions for system-level performance are derived by considering that all SUs experience independent fading and statistically identical signal-to-noise ratios. Performance of the proposed cooperative sensing scheme has been evaluated both analytically and by simulations.

A Novel Swarm Intelligence Based Routing Scheme for Manet using Weighted Pheromone Paths

The highly dynamic topology, limited bandwidth availability and energy constraints for mobile ad-hoc networks (MANETs) make the routing scenario in MANET a complex one. In this paper, we present a novel routing scheme in MANET based on ant colony optimization (ACO) algorithm that is probabilistic in nature and inspired by the foraging behavior of the real ants. This routing scheme takes into account the trip time along with the estimated queuing delay as the optimization criterion to select the route for packet transmission from source node to destination node, whereas, in the existing algorithms total path delay is determined from hop count and processing delay (a fixed value for all nodes) only, which is far away from reality. In the proposed algorithm, nonlinear weights for the deposited pheromone at the intermediate nodes are obtained by incorporating some aspects of queuing delay analysis while calculating the total path delay. Simulation results in terms of average end-to-end delay and packet delivery rate have been obtained to show the performance of the algorithm

An Approach to Recursive Equalization via White Sequence Estimation Techniques

A state space modeling approach to equalization, which is applicable to both finite, as well as infinite impulse response channels, is presented. The order of the state space model is typically much Smaller than the length of the impulse response. It is shown by analysis and simulation that the proposed approach has considerably less digit mean square-error as compared to the conventional Kalman filter equalizers for much smaller model orders and, hence, computational efforts.

Coverage Analysis of Two-Tier HetNets for Co-Channel, Orthogonal, and Partial Spectrum Sharing Under Fractional Load Conditions

In heterogeneous networks, the random deployment of femto access points (FAPs) and macro base stations (MBSs) with uncoordinated channel access imposes huge intertier interferences. In real-life networks, the process of MBSs’ deployment exhibits the homogeneity; however the FAPs have the behavioral characteristic of clusters formation, such as in malls, apartments, or offices. Therefore, the composite modeling of the MBSs and the FAPs using Poisson point process and Poisson cluster process is employed for the evaluation of coverage probability. The scenario of the real-time traffic for macrotier and the best-effort traffic for femto-tier is considered. Cognition is introduced in the clustered FAPs to control the intertier interference. Furthermore, the impact of the macrotier load is analyzed by exploiting the inherent coupling between coverage probability and activity factor of an MBS. Further, we study the effect of co-channel, orthogonal, and partial spectrum sharing modes on the coverage for given parameters, such as load condition and FAPs/MBSs density. We provide simulation validation for the derived expressions of coverage and present a comparative analysis for the mentioned spectrum sharing modes.

Evaluation of Blocking Probability for Downlink in Poisson Networks

In recent years, wireless network modeling using stochastic geometry tools, like Poisson Point Process (PPP), has acquired the attention of researchers. Modeling of interference, coverage, and capacity for cellular networks using PPP is presented in literature. However, the blocking probability remains to be investigated. In this letter, we present an analytical framework for evaluation of network blocking probability for downlink. The services can be categorized using multiple classes based on the average resource units required by the service. The multi-class service scenario is modeled using multi-dimensional Markov Chain. The Markov chain is further approximated using the Erlang approximation method to evaluate the activity factor of a base station (BS). Moreover, an approximate closed form expression for coverage probability is derived, which is applicable to interference as well as noise limited scenario. Exploiting the coupling between coverage and activity factor, we determine the class-wise arrival rate. Further, the class-wise arrival rates are used to determine the networks blocking probability. We validate the proposed analytical framework through the extensive simulation.