Brownson Obaridoa Obele

Analysis of the Behavior of Self-Similar Traffic in a QoS-Aware Architecture for Integrating WiMAX and GEPON

The access network has remained the bottleneck in efforts to deliver bandwidth-intensive new-generation applications and services to subscribers. In the wired access network, the gigabit Ethernet passive optical network (GEPON) is a promising technology for relieving this bottleneck, while its counterpart in the wireless access network is worldwide interoperability for microwave access (WiMAX). A converged quadruplet-service-enabled (video, voice, data, and mobility) network, which takes full advantage of the strengths and weaknesses of each of these promising technologies, has been proposed. Besides, research and Internet measurements have revealed that actual Ethernet and wireless data traffic are self-similar and long-range dependent. Therefore, we review the quality of service (QoS) architecture for integrating WiMAX and GEPON access networks that we proposed in previous work. Then, we present an analysis of the queuing behavior of the QoS architecture under self-similar and long-range-dependent data traffic conditions and derive closed-form expressions of the expected waiting time in queue (queuing delay) and the packet loss rate per QoS traffic class. This work brings novelty in terms of presenting performance analysis of the proposed QoS-aware integrated architecture under realistic load conditions and facilitates the provisioning of tightly bound QoS parameters to end users of the converged access network.

Multipath transport protocol for heterogeneous multi-homing networks

We present a new multipath transport protocol - Heterogeneous Multipath Transport Protocol (HMTP), powered by fountain codes to improve throughput performance and path utilization of heterogeneous multi-homing networks. HMTP solves the receive buffer blocking problem and eliminates the need for retransmission and in-order packet delivery, especially in a heterogeneous multi-homing network.

Determining Optimal Sensing Time for Multi-Radio Multi-Channel Cognitive Radios

Fast and e-cient spectrum sensing is vital for multi- radio multi-channel cognitive radio (CR) networks where unlicensed secondary users (SUs) have to sense and opportunistically transmit on multiple spectrum bands without causing any harmful interference to the licensed primary users (PUs) of those spectrum bands. Accordingly, this paper presents a smart, practical and e-cient wideband spectrum sensing scheme based on an optimal sensing stop policy that aims to optimize SU throughput while adhering to the PU interference constraints. Unlike existing work, this scheme is smart because in determining the best time for the multi-transmitter SU to stop sensing and start data transmission based on the channels that have been sensed idle, this scheme explicitly takes into consideration the number of transmitters on the SU; so-called N-transmitters constrained SU. Further, we formulate and solve the optimal sensing stopping problem. The numerical and simulation results presented verify the e-ciency of the proposed sensing scheme.

HMTP: Multipath transport protocol for multihoming wireless erasure networks

This paper proposes a fountain-code-based multipath transport protocol, called heterogeneous multipath transport protocol HMTP, and evaluates its performance. HMTP improves the throughput performance and path utilisation of multihoming wireless erasure networks. It solves the receive buffer blocking problem and eliminates the need for retransmissions and in-order packet delivery, both of which severely degrade the performance of existing multipath transport protocols in multihoming networks. The encoding and decoding algorithms of HMTP are based on efficient and computationally inexpensive coding algorithms such as LT codes. To minimise the fountain encoding/decoding overhead, complexity and computational cost while ensuring the desired decoding performance, the appropriate values of the parameters of the LT codes are determined. We implement and extensively evaluate the performance of HMTP using both NS-2 simulator and an 802.11 wireless local area network laboratory test bed. Our simulations and experimental results show that HMTP significantly outperforms the concurrent multipath transfer stream control transmission protocol, especially in multihoming 802.11 wireless local area networks. Copyright

Robust indoor localization based on hybrid Bayesian graphical models

In this paper, we study the problem of accurately estimating the location of indoor wireless devices which, due to its vast application areas, has continued to generate much interest both in the academia and industry. Specifically, we consider the location estimation problem and develop non-hybrid Bayesian location estimators for when received signal strength (RSS) and/or time of arrival (TOA) measurements between the target node (TN) and designated beacon nodes (BNs) in the network are obtainable. However, RSS- and TOA-based location estimators can be inaccurate when the RF-characteristics are not stable and time synchronization between the TN and BNs is not set up properly, respectively. To mitigate the disadvantages of these two location estimators, we propose the hybrid Bayesian location estimators. We show, through the results of extensive simulation experiments conducted that in comparison with the non-hybrid estimators, the hybrid Bayesian location estimators are more robust in the localization environment where RSS/TOA measurement precision varies.

On the QoS behavior of self-similar traffic in a converged ONU-BS under custom queueing

A novel converged optical network unit (ONU)-base station (BS) architecture has been contemplated for next-generation optical-wireless networks. It has been demonstrated through high quality studies that data traffic carried by both wired and wireless networks exhibit self-similar and long range dependent characteristics; attributes that classical teletraffic theory based on simplistic Poisson models fail to capture. Therefore, in order to apprehend the proposed converged architecture and to reinforce the provisioning of tightly bound quality of service (QoS) parameters to end-users, we substantiate the analysis of the QoS behavior of the ONU-BS under self-similar and long range dependent traffic conditions using custom queuing which is a common queuing discipline. This paper extends our previous work on priority queuing and brings novelty in terms of presenting performance analysis of the converged ONU-BS under realistic traffic load conditions. Further, the presented analysis can be used as a network planning and optimization tool to select the most robust and appropriate queuing discipline for the ONU-BS relevant to the QoS requirements of different applications.

On an Embedded Software Design Architecture for Improving the Testability of In-vehicle Multimedia Software

In-vehicle multimedia software quality remains critical to assuring vehicle-owner satisfaction and loyalty. Automated software testing has been identified as fundamental to software quality assurance but the success of such automated testing depends largely on the testability of the software under test. Accordingly, this paper presents an industry experience report which discusses a software design architecture that helps to improve software testability. This architecture which is currently being used in our software verification laboratory is simple, easily scalable, efficient, reliable and practical to implement. It enforces close collaboration between the software engineers and automation tool developers (testers) which helps to alleviate limitations of off-the-shelf test automation solutions such as tool compatibility, reusability, maintenance and usefulness.

On the QoS behavior of a converged ONU-BS

A converged ONU-BS has been proposed for optical-wireless convergence. To help its understanding and especially how QoS is affected, we analyze it under realistic traffic conditions using common queuing disciplines.