Isik Aybay

Predictive mobile-oriented channel reservation schemes in wireless cellular networks

Provision of seamless service to multimedia applications in cellular wireless networks largely depends on the way calls are handled during handoff. Hence, sufficient resources must be provided for handoff (HO) connections when a mobile station (MS) moves from one cell to another. Effective allocation of resources can be achieved when the exact future trajectory of MSs is known in advance. However, such a scenario is unrealistic. The next best possibility is to employ user mobility prediction to determine the cell(s) a MS will likely visit in the near future. In this paper, we present an extensive survey and classification of channel (bandwidth) reservation schemes which employ user mobility prediction in the resource reservation process. We also present a survey and classification of call admission control (CAC) schemes, including discussion of prioritized and non-prioritized handoff schemes, which can be useful for researches both in academia and industry.

Handoff Prioritizing Schemes in Cellular Wireless Networks

This paper provides a detailed discussion of nonprioritized and prioritized handoff schemes. It presents a survey of published papers in this area. Moreover, an extensive classification of handoff prioritizing schemes is presented in this paper

A randomized contention-based load-balancing protocol for a distributed multiserver queuing system

A novel protocol for load balancing in distributed multiserver queuing systems is proposed. The protocol is based on an anonymous multicast communication in a network of servers or workers. A formal description of the protocol in terms of a state diagram is given. The complexity issues of the protocol are considered. The protocol was investigated by the use of a simulation model in terms of a class of the extended Petri nets and implemented as a prototype system on a group of computers in a LAN of Ethernet type. The results of simulation and prototype-system studies of a distributed queuing system with the proposed protocol are compared to the behavior of an ideal, centralized queuing system. Limitations and possible extensions to the protocol are outlined.

A digital neuron realization for the random neural network model

In this study, the neuron of the random neural network (RNN) model (Gelenbe 1989) is designed using digital circuitry. In the RNN model, each neuron accumulates arriving pulses and can fire if its potential at a given instant of time is strictly positive. Firing occurs at random, the intervals between successive firing instants following an exponential distribution of constant rate. When a neuron fires, it routes the generated pulses to the appropriate output lines in accordance with the connection probabilities. In the digital circuitry the fundamental parts of the neuron are simulated by realizing input module, neuron potential module, firing module and routing module. The neuron potential module accumulates incoming signals collected by the input module at the input site. The firing module generates random pulses with an exponential distribution of fixed rate. The pulses generated by the firing module are distributed to the other neurons through the routing module at the output side. A network of neurons can be constructed by using the digital circuitry presented for the single neuron. All the parts of the random neuron circuit are simulated by using Circuitmaker and Pspice digital simulation packages and the neuron is realized digitally by using LS-TTL ICs.

Influence of mobility models on the performance of data dissemination and routing in wireless mobile ad hoc networks

Graphical abstractDisplay Omitted Extended simulations for AODV, DSDV, and DSR routing protocols on MGM, GMM, and RPGM mobility models in addition to RWPM.Longer duration considered for simulation of routing protocols over mobility models and first 500s discarded.Results will help researchers to decide which routing protocol is better for which mobility model. Many routing protocols are proposed in the literature on mobile ad hoc networks (MANETs). Some of those protocols which have been investigated under different assumptions are unable to capture the actual characteristics of MANETs. Therefore, there is a necessity to investigate the performance of MANETs under a number of different protocols with various mobility models. This paper evaluates the performance of the single path routing protocols (AODV, DSR, and DSDV), in the presence of different network loads and differing mobility models. Our findings show that DSR routing protocol has a better performance compared to other protocols with respect to various metrics.

Improving VoD Performance with LAN Client Back-End Buffering

We developed a peer-to-peer local area network client back-end buffering system module for video-on-demand (VoD) systems. Our aim is to minimize both the number and duration of stops experienced by users, thereby minimizing the cost while improving the performance. Simulations show that our module outperforms both typical and recently proposed VoD systems

Document management in HALdoc

HALdoc is a general purpose document processing and archiving system. The documents archived in the system are not restricted only to text files. It can also archive images, sounds etc., in addition to text files. The system also includes a built-in OCR program and a scan control subsystem to get images of new documents. The general properties of the HALdoc system are introduced and how documents are managed in HALdoc is explained. The logical hierarchy used in the organization of HALdoc documents, and the client-server architecture used in accessing these documents is discussed.<<ETX>>

Performance Evaluation of Call Admission Control Schemes with New Call Reattempts in Wireless Cellular Networks

The majority of call admission control schemes proposed for wireless cellular networks do not take new call redials into account. However, connection reattempts are known to have a negative impact on the system performance because they generate more load. In this paper, we shall investigate how some popular call admission control schemes perform under more realistic conditions.

Performance Evaluation of Non-prioritized and Prioritized Call Admission Control Schemes in Wireless Cellular Networks

In cellular wireless networks, the choice of Call Admission Control scheme impacts the performance of the system, particularly as how calls are managed when a mobile user is handed off from one cell to another. Non-prioritized schemes treat handoff calls and new calls equally, while, prioritized schemes give higher priority to handoff calls. In this paper, some of the popular non-prioritized and prioritized Call Admission Control schemes were investigated and their behavior was simulated and analyzed. They are evaluated based on call dropping probability, call blocking probability and system utilization parameters.

Prioritized New Call Threshold Policy for Wireless Cellular Networks

This paper proposes a Prioritized New Call Threshold Policy for Call Admission Control schemes. It is known that connection reattempts negatively affect the system performance. In currently proposed policy, the system’s performance is improved by decreasing the number of connection reattempts. In order to demonstrate that the proposed scheme is better than the traditionally utilized ones in terms of various parameters, the simulations were utilized. It predicts the time that the mobile station will spend in the current cell, mobile station with different remaining time will have different number of channels available for them. More channels are available for the new calls with higher remaining time. Simulations were used in order to show that the proposed scheme outperforms the traditionally employed mechanisms in terms of various parameters.