
William RobertsonDalhousie University | Dal · Department of Engineering Mathematics and Internetworking
William Robertson
Ph.D.
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112
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Introduction
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Publications
Publications (112)
This paper introduces a new Link State Advertisement (LSA) for a new link characteristic to be used with Constrained Open Shortest Path (CSPF) routing mechanism. The new LSA is to be exploited for building a topology database based on realistic energy and Co2 emission data about each link and the sections of the network. The energy-aware CSPF mecha...
This paper presents an analysis of the role of the networking choices on health care applications. The variation in the implementation of networks that evolved to Medical Grade Networks are explored for five different medical network applications in terms of the network parameters, performance and success results of these health care applications....
Cloud computing created many new opportunities for organisations across the world. Presently, Cloud services are available at affordable prices and accessible for all scales of businesses. The economic benefits of this wider acceptance to adopting Cloud computing are enormous and many companies have embraced Cloud computing now. Over the years, tec...
This paper applies network tomography for load balancing. Load balancing is the allocation of the work of a single application to processors at run-time so that the execution time of the application is minimized. In order to achieve this purpose, load balancing algorithms require various network parameters to make decisions for effectively balancin...
The paper deploys an adaptive provisioning algorithm to the traffic with huge volume of high-priority connection (BHC) requests with long holding time by proposing a novel service level agreement (SLA) aware mechanism over optical shared mesh networks. The contribution presented in this paper follows three main characteristics: (i) Proposing a new...
The paper describes a literature overview of the main building blocks of service level agreement based architectures over priority-aware shared mesh optical networks. The standardized protocols and existing algorithms for path attributes and service level agreement parameters negotiation are studied in this paper and shortcomings of each are identi...
This paper introduces an SLA-based routing mechanism to lower the Co2 emission rate of the optical networks governed by GMPLS. This approach provides the most available routes between any pair of source and destination nodes using a routing table populated in advance, using the combination of weather forecasting information and energy resource maps...
This paper presents a novel and efficient algorithm to implement Central Routing (CR) as an alternative to the existing approaches to avoid full mesh topology in internal border gateway protocol (iBGP). BGP is a key protocol to exchange routing information within an Autonomous System (AS) and among various ASes. All the routers inside an AS have to...
This paper introduces the dissemination of Hybrid cost calculated for each route in Emission Aware and SLA Based Routing Mechanism as path attribute for purpose of inter-domain routing operation. This paper then compares the performance of the routing mechanism using this method against performance of the routing methods using other types of transm...
Satisfying customers’ traffic engineering connection requests is one of the biggest challenges of today's service providers. However, routing mechanisms which only consider service level specifications as the path selection criteria may not be aware of energy consumption and Co2 emission rate of the routed paths. This can generate huge Co2 emission...
The paper describes a literature overview of the main building blocks of service level agreement based architectures over priority-aware shared mesh optical networks. The standardized protocols and existing algorithms for path attributes and service level agreement parameters negotiation are studied in this paper and shortcomings of each are identi...
This paper provides a detailed comparison among emission efficient routing mechanisms introduced in previous works. Emission efficient routing mechanisms focus on reducing of the emission of required energy to operate optical networks such as GMPLS networks, by using green sources of energy in systemic and automatic manner without human interaction...
The paper deploys an adaptive provisioning algorithm to the traffic with huge volume of high priority connection requests with long holding time by proposing a novel SLA-aware mechanism over optical shared mesh networks. The contribution presented in this paper follows three main characteristics: i) Proposing a new time-aware traffic engineering pa...
This paper presents a dynamic inter-domain negotiation mechanism over green optical networks. The proposed propagation mechanism disseminates the source types of energies to all nodes while it advertises a proposed path attribute called minimum path emission. The paper shows how the dynamic negotiation protocol along with the proposed traffic engin...
The paper investigates how the level of re-provisioning of lightpaths can affect the calculation of the cost of lightpaths and consequently the result of routing decisions. The paper introduces a re-provisioning mechanism with partial re-routing capabilities to lower the Co2 emission rate while it provides the most available routes between any pair...
This paper is an extension to the previous work that introduced the hybrid energy-aware and service level agreement (SLA) based routing mechanism over optical networks. This paper introduces an adaptive SLA-based routing approach to lower the Co2 emission rate while it provides the most available routes between any pair of source and destination. T...
This paper investigates the scalability issues concerned with the dynamic SLA negotiation mechanism proposed in the previous study. The previous work presented a dynamic service level agreement negotiation mechanism considering intra- and inter-domain communications over shared mesh optical networks which may cause heavy control overheads in a dyna...
This paper presents a novel link-layer encryption protocol for wireless sensor networks. The protocol design aims to reduce energy consumption by reducing security related communication overhead. This is done by merging security related data of consecutive packets. The merging (or combining packets) based on simple mathematical operations helps to...
Security was not considered when current wireless sensor nodes were designed. As a result, providing high level of security on current WSNs platforms is unattainable, especially against attacks based on key resolving and node compromise. In this paper, we scrutinize the security holes in current WSNs platforms and compare the main approaches to imp...
In this paper, we introduce Compact-Security (C-Sec), an energy efficient link layer encryption protocol for Wireless Sensor Networks (WSNs). The protocol minimizes energy consumption by eliminating the need for transmitting all header and trailer fields related to security, while keeping security functions and services intact. Such fields include...
The paper introduces two novel algorithms, one each for static and dynamic traffic types, to improve the availability of high priority connection requests over shared mesh optical networks. The proposed algorithms are a complementary study to the previous work. The paper also proposes a new metric, maximum path availability, by which the proposed a...
Security was not considered when current wireless sensor nodes were designed. As a result providing high level of security on current WSNs platforms is unattainable, especially against attacks based on key resolving and node compromise. In this paper we scrutinize the security holes in current WSNs platforms, and compare the main approaches to impl...
The paper presents a dynamic provisioning mechanism through which service providers can exploit the unused allowable down time of the connections to serve the additional upcoming requests. The algorithm work based on the holding time of the connections and the failure arrival rate over the selected primary or backup paths. The proposed mechanism in...
Clustering techniques have emerged as a popular choice for achieving energy efficiency and scalable performance in large scale sensor networks. Cluster formation is a process whereby sensor nodes decide which cluster head they should associate with among multiple choices. Typically this cluster head selection decision involves a metric based on par...
In recent years a flurry of research activity has produced many suggested schemes for clustering wireless sensor networks, but no hard numbers for real-world implementations. This lack of guidance for developers makes it very difficult to effectively and confidently build working networks. This paper partially addresses these concerns by deriving m...
Errors in data measurements for network tomography may cause misleading estimations. This paper presents a novel technique to model these errors by using sparse code shrinkage (SCS) method. SCS is used in the field of image recognition for denoising the image data and we are the first to apply this technique for estimating error free link delays fr...
We introduce a novel concept of multiple metric network tomography in this paper. The conventional network tomography observes a single parameter directly and infers another parameter indirectly from the the directly measured parameter. We consider observing two parameters (packet loss rate (PLR) and path delays) directly and use both of these para...
This paper presents the application of a matrix based technique to eliminate the assumption of a known routing matrix in network tomography. Network tomography is an effective means of determining network performance parameters such as delay and packet loss rate (PLR). It gives indirect inference of network characteristics using active probes or pa...
This paper investigates coverage and connectivity issues for Wireless Sensor Networks (WSNs) under three dimensional deployment scenarios. WSNs are deployed over a region to sense the events of interest in a geographical area and transmit collected data to a Base Station (BS). We exploit the inherent redundancy in WSN deployment by finding an optim...
In this paper, we apply the technique of sparse shrinkage coding (SCS) to denoise the network tomography model with errors. SCS is used in the field of image recognition for denoising of the image data and we are the first one to apply this technique for estimating error free link delays from erroneous link delay data. To make SCS properly adoptabl...
Anomalous activities such as flash crowd/event and denial of service (DoS) overload a pool of servers that hosts web contents. This is a great challenge for the 24 by 7 provision of Web contents and may result in interruption of the Web services. Therefore, it is very important that the occurrence of such activities is monitored so that in case of...
This chapter presents a multiple constraint optimization algorithm called routing decision system (RDS) that uses the concept of preference functions to address the problem of selecting paths in core networks that satisfy traffic-oriented QoS requirements while simultaneously satisfying network resource-oriented performance goals. The original cont...
Network multimedia applications constitute a large part of Internet traffic and guaranteed delivery of such traffic is a challenge because of their sensitivity to delay, packet loss and higher bandwidth requirement. The need for guaranteed traffic delivery is exacerbated by the increasing delay experienced by traffic propagating through more than o...
This paper investigates the effects of using a realistic discrete power model in cluster-based communication for Wireless Sensor Networks (WSNs). Four different clustering protocols are evaluated by incorporating a model compliant with Crossbow MICAz motes. The energy consumption model takes into account the discrete transmit power levels of the CC...
Recent years have witnessed an increasing availability of heterogeneous sensor networks that consist of a large number of resource constrained nodes (sensors) and a small number of powerful resource rich nodes (actors). Such heterogeneous Wireless Sensor Actor Network (WSANs) offer improvement of sensor networks' capacity/coverage, energy conservat...
In this paper, results from Wald's equation and stochastic geometry are applied to the analysis of the energy expended in a homogeneous clustered Wireless Sensor Network (WSN). We determine the optimum number of clusterheads for minimising the energy expended by a single-hop clustered WSN in transmitting data to a sink using nonlinear and linear ag...
Extended network life is one of the fundamental objectives in the design of Wireless Sensor Network systems. Clustering protocols help in achieving this objective in an efficient and scalable manner by organizing nodes into small hierarchical groups. In single hop clustering protocols, assumptions are made about direct communication from the cluste...
In recent years, network security has emerged as one of the most important challenge for many organizations. The enormous proliferation of the Internet and emergence of unified data, voice and multimedia services are responsible for emerging communication models that are essential for successful business activity of any organization. However, the i...
Clustered wireless sensor network models typically assume that a clear line-of-sight path separates the transmitter and receiver within a cluster; an accurate assumption for relatively short distances. For longer distances, and in environments that are obstructed, the log-distance path loss model agrees better with measurements. In this paper, comm...
Significant challenges has been introduced for IP networks with the advent of new emerging applications, such as VOIP and E-commerce, that require delivering quality guarantees. However, IP networks were originally designed to support best effort delivery only. Three quality of service (QoS) models, IntServ, DiffServ and multiprotocol label switchi...
Wireless sensor actor networks (WSANs) consist of a large number of resourceconstrained nodes (sensors) and a small number of powerful resource rich nodes (actors). This paper investigates the case where sensors are organized into clusters and mobile actors are used for maintaining an energy efficient topology by periodically manipulating their geo...
Significant challenges has been introduced for IP networks with the advent of new emerging applications, such as VOIP and E-Commerce, that require delivering quality guarantees. However, IP networks were originally designed to support best effort delivery only. Two Quality of Service (QoS) standard models, IntServ, DiffServ have been standardized b...
IntroductionVANET CharacteristicsEnabling TechnologiesVANET ConnectivityDynamic Transmission Range AssignmentRoutingApplicationsVehicle MobilityConcluding RemarksExercisesReferences
Extended network life is one of the fundamental objectives in the design of wireless sensor network systems. Clustering protocols help in achieving this objective in an efficient and scalable manner by organizing nodes into small hierarchical groups. In single hop clustering protocols, assumptions are made about direct communication from the cluste...
In wireless sensor networks, unbalanced energy dissipation is one of the major causes for hot spots. The many-to-one communication pattern used by sensor nodes in most of the data gathering applications leads to such unbalanced energy consumption. Cluster-based protocols attempt to solve this problem by load balancing within the cluster and rotatin...
In large scale wireless sensor networks clustering is often used for improving energy efficiency and achieving scalable performance. In this paper we present a novel energy efficient cluster formation algorithm based on a multi-criterion optimization technique. Our technique is capable of using multiple individual metrics in the cluster formation p...
This paper discusses the impact of the non-homogeneous distribution of vehicles on the connectivity of vehicular ad hoc networks (VANETs). The non-homogeneous distribution of vehicles results from traffic jams caused by bottlenecks in the transportation networks and by fluctuations in vehicles' speeds. The discussion in this paper is applicable to...
Networking, communications and computing research employ state-of-the-art infrastructure and facilities to develop and test next generation Internet applications including electronic education and electronic health. With this focus, the Internetworking Program at Dalhousie University has established an Advanced Internetworking Laboratory (AIL) rese...
This paper derives an algorithm for minimizing energy spent by a hierarchical wireless sensor network in transmitting data to a sink, referred to as a base station. The network model considered is a single-hop multi-level clustered network. We draw on results from stochastic geometry to analytically determine the optimum number of clusters at each...
This paper derives an algorithm for minimizing energy spent by a hierarchical wireless sensor network in transmitting data to a sink, referred to as a base station. The network model considered is a single-hop multi-level clustered network. We draw on results from stochastic geometry to analytically determine the optimum number of clusters at each...
A web based remote Internetworking laboratory that delivers interactive laboratory experience to geographically remote graduate
students is presented in this paper. The online Internetworking (INWK) laboratory learning environment employs remote interaction
with networking equipment in both individual and group setting that correlates with the cons...
A Web-based remote interactive laboratory (RIL) developed to deliver Internetworking laboratory experience to geographically remote graduate students is presented in this paper. The onsite Internetworking program employs hands-on laboratories in a group setting that correlates with the constructivist and collaborative pedagogical approach. This pap...
Vehicular Ad Hoc Networks (VANET) have several characteristics that distinguish them from other ad hoc networks. Among those is the rapid change in topology due to traffic jams, which also disturbs the homogenous distribution of vehicles on the road. For this reason, a dynamic transmission range is more effective in maintaining connectivity while m...
Connectivity in mobile wireless ad-hoc networks is maintained by setting the transmission range so that a node can establish a link to any other node in the network either directly or over multiple hops. Many analytical and experimental studies have focused on determining the minimum transmission range (MTR) that provides connectivity while minimiz...
TCP is the widely used transport protocol across the Internet but it was originally designed for wired networks. In satellite networks, TCP encounters serious problems due to the physical properties of the wireless medium. The high delays in GEO networks and high variability of delay in LEO systems are the most significant factors affecting TCP per...
Heuristic QoS algorithms under strict constraints perform poorly in terms of finding a path that is suitable for a user's QoS needs-the multiple constraint path problem (MCP). Exact QoS algorithms, on the other hand, guarantee that a path satisfying user needs would be found and offer a more realistic approach for solving the MCP problem in view of...
The core of any QoS routing algorithm designed to solve the multi-constrained optimal path problem, is a length function that is used to find the optimal route across the network. User applications require diverse optimisation requirements but typical QoS-based algorithms have fixed length functions and do not offer a flexible optimisation framewor...
Currently the Internet based on IP supports a single best-effort service in which, all packets are queued and forwarded with the same priority. No guarantees are made regarding timely and guaranteed delivery. However, many e-commerce applications, that are delay and loss sensitive, use the Internet as a transport infrastructure because of its reach...
A two-stage simulation model is developed to investigate the effects of free flow traffic on connectivity in inter-vehicle ad hoc networks. A traffic microsimulator generates vehicle movement in a multi-lane, unidirectional highway, and a simple network model maintains connectivity graphs between the moving vehicles. The free flow conditions allow...
The core of any quality of service (QoS) scheme is how to monitor and manage traffic flows that have guaranteed QoS. The two QoS approaches used in the literature are, IntServ (integrated service) (White, P.P., 1997) and DiffServ (differentiated service) (Blake, S. et al., 1998). IntServ uses the resource reservation protocol (RSVP) for signaling t...
The problem of finding QoS paths involving several combinations of network metrics is NP-complete. This motivates the use of heuristic approaches for finding feasible QoS paths. Many constraint based routing algorithms find QoS paths by first pruning resources that do not satisfy the requirements of the traffic flow and then running a shortest path...
Quality of service (QoS) support in mobile ad hoc networks (MANET) is a very challenging task because of the dynamic topology, limited resources and wireless link characteristics. The optimized link state routing protocol (OLSR) is a pro-active routing protocol for MANET. The metric used in OLSR protocol is hop count, which is not suitable for the...
An integrated Web engine (IWE) has been developed by the Internetworking program at Dalhousie University, Halifax, Canada to deliver remote learning experience to geographically remote Master's students. The University intends to increase its student base through online education, retaining the same quality of interactions as the onsite program. To...
QoS routing protocols involving several combinations of network metrics can be difficult to solve in polynomial time. Our
research introduces anovel approach that allows bandwidth brokers to perform QoS management in Diffserv Domains with any
number and combination of network metrics with algorithm complexity of O(m(n + 1)) where m is the number of...
The Faculty of Engineering at Dalhousie University, Halifax, Canada has been offering a Master's degree program in Internetworking since 1997. The program also provides comprehensive "hands-on" laboratory experience in configuring, maintaining, troubleshooting and simulating networks. The university intends to increase its student base through onli...
Routing using more than one metric is difficult. Distributed Multimedia applications have stringent QoS demands on the network. However, many current QoS routing algorithms have large execution times when strict (small) user constraints are used. We present an algorithm that have relatively small execution times under strict constraints and demonst...
Host mobility patterns have an important effect on performance of ad hoc networks. For this reason, many evaluation studies involve analytical or simulation models to synthesize the movement of mobile hosts. The growing interest in investigating the use of ad hoc networks in inter-vehicle communication demands a vehicle mobility model that is capab...
With the growth of the Internet and intranets, and the use of multimedia applications, video and audio streams, QoS (quality of service) technology has become more relevant and important Yoram Bernet (2000). The next generation Internet protocol (IPv6) provides more features than IPv4 such as more address space and new fields that can be used to en...
Transmission control protocol (TCP) is used by many standard data application in current wired networks. It has proven to work well in traditional networks where packets losses are mainly due to network congestion. On the other hand, a totally different scenario happens in the wireless link. Due to the high bit error rate (BER), TCP performance is...
End-to-end quality of service (QoS) is defined as the capability of a network to provide better service to selected network traffic over various network technologies such as IP, ATM or frame relay networks. Recently users are beginning to combine real-time applications such as voice and video, which have a limited tolerance for network latency and...
This paper introduces an automatic speaker-independent speech
recognition system. We investigate the performance of the wavelet packet
in the analysis of automatically generated subwords of single digits.
The modeling of the subwords is accomplished using multienergy levels of
a derived mel-like scale. A radial basis function artificial neural
netw...
The objective of this paper is to recognize speech based on speech
prediction techniques using a discrete time recurrent neural network
(DTRNN) with a block diagonal feedback weight matrix called the block
diagonal recurrent neural network (BDRNN). The ability of this network
has been investigated for the TIMIT isolated digits spoken by a
represent...
This paper describes three models acquired by applying various
wavelet analysis techniques to subwords for the purpose of speaker
independent single digit recognition. We emphasize the parameterization
of the subwords according to a Mel scale in the cases of the sampled
continuous wavelet transform (SCWT) and the wavelet packet decomposition
(WPD)....
We describe a model obtained by applying the discrete wavelet
transform (DWT) to unequally segmented digits. Each signal is divided
with a pre-determined segmentation into a maximum of five subwords. The
purpose is speaker independent single digit recognition. The
parameterization of the subwords is accomplished by measuring its energy
contents aft...
This paper investigates the use of a spectral variation function
to automatically detect acoustic sub-word boundaries in single digits.
The developed algorithm generates sub-words for single-digit recognition
system using an RBF neural network
Speech compression is the technology of converting human speech
into an efficient encoded representation that can be decoded to produce
a close approximation of the original signal. In this paper, we propose
a new algorithm which compresses speech signals using a wavelet
compression technique. The performance of this method is compared
against the...
This paper deals with a discrete-time recurrent neural network (DTRNN) with a block-diagonal feedback weight matrix, called the block-diagonal recurrent neural network (BDRNN), that allows a simplified approach to online training and to address network and training stability issues. The structure of the BDRNN is exploited to modify the conventional...
Motion artifacts have been identified as a problem in medical tomography systems. This paper describes an approach which tracks the motion and allows the artifacts to be isolated. Two sources are utilized so that two sets of projections are generated that are identical in space but separated in time
This paper deals with a discrete time recurrent neural network (DTRNN) with a block-diagonal feedback weight matrix, called the block-diagonal recurrent neural network (BDRNN), that allows a simplified approach to online trajectory learning. The BDRNN is a sparse but structured architecture in which the feedback connections are restricted to betwee...
This paper considers the construction method for the block-diagonal recurrent neural network (BDRNN) that is capable of modelling plants with complex eigenvalues. If nonlinear dynamics can be decoupled into a dominant dynamic and several less dominant dynamics, then it is feasible to employ blocks of BDRNNs, one each, to automatically learn each of...
The authors present the effects of employing limited precision
arithmetic on radial basis function networks (RBF). A statistical
formula is first derived to obtain an analytical expression for the
error so that it can be used for hand-calculations. A speech processing
example is chosen to compare the theoretical results with its simulation
counterp...
An investigation of using fixed-point arithmetic on a neural
networks is presented. A formula that estimates the standard deviation
of the output differences of fixed-point and floating-point networks is
developed. The formula provides a priori knowledge regarding the
required number of bit precision that should be employed to achieve
acceptable re...
This investigation aims to define an advanced signal processing
structure that will allow the implementation of a wide variety of
conventional, adaptive and synthetic aperture signal processing schemes
in 1-dimensional (1-D) and 2-dimensional (2-D) real time systems and
will exploit processing concept similarities among radar, sonar and
medical tom...
We have investigated the implementation of relatively new
broadband adaptive processing schemes in line array sonar systems with
passive and active capabilities. We provide details of the investigation
of adaptive beamforming schemes with and instantaneous convergence for
matched filter processing. These schemes include a so-called memoryless
gener...
Electronic ANNs rely heavily on the use of two-dimensional silicon and PCB substrates. Use of these substrates results in hierarchical hardware that exhibits varying levels of connectivity. Numerous approaches have been developed for ge