Semi-Stateful QoS Models in Mobile Ad Hoc Networks (MANETs)

The existing literature on Quality-of-Service (QoS) in ad hoc networks can be broadly categorized into stateful QoS and stateless QoS architectures. Providing stateful QoS in MANETs is not significant in the presence of low traffic and high mobility and it is too costly due to scarce resource in the network. Stateless QoS, on the other hand, faces the problem of stale QoS bandwidth or delay information since there is no mechanism to keep the information of the flows status. However, there has been a little work investigating the semi-stateful QoS model. Therefore, this study aims to further investigate the semi-stateful QoS model by deploying a new resource reservation mechanism to the stateless QoS in order to provide QoS guarantees in MANETs. Furthermore, this research also investigates how adaptive QoS models can further be developed in order to achieve QoS guarantees in Mobile networks

 

 

Broadcast Algorithms in Ad Hoc Mobile Networks

An Ad-hoc network is a collection of mobile nodes forming a temporary network without any centralized administration, so nodes must cooperate to route a packet. Broadcast service is a fundamental operation in ad hoc networks for different application. It is often necessary in MANET routing protocols to establish route to particular host, paging a particular host, and sending an alarm signal. However, broadcasting by native flooding is usually very costly and will result in serious redundancy, contention, and collision. The goal of this research is the development and analysis of more efficient broadcast methods that can minimize the number of retransmissions while ensuring high delivery of broadcast packets.

 


Performance Analysis of Routing Algorithms for MANETs

Mobile ad hoc networks (MANETs) have become the focus of intense research in recent times due to the advent of affordable mobile devices and the wide applicability of such networks to military and civil purposes. Nodes participating in such a network can be highly mobile and so exhibit unexpected connectivity changes that may radically change the topology of the network. This sort of environment has prompted the development of new routing algorithms that will address the challenges of optimal route discovery, goodput increase and effective scalability. Several ad hoc routing algorithms have been proposed to take up those challenges. These can be classified as proactive or reactive. Proactive routing algorithms discover routes between source and destinations whether there is use for those routes or not. Alternatively, reactive or "on demand" routing algorithms only try to discover a route once it is needed.  In this research, we conduct an extensive performance comparison of some well-known routing algorithms with the aim of identifying of identifying any performance deficiencies and propose practical methods to overcome them.

 


A Bandwidth Efficient Routing Protocol for MANETs

MANETs have dynamic topologies by nature, and have some limitations such as limited bandwidth and limited power. A routing protocol that is able to deal efficiently with its dynamic nature and its natural limitations is crucial to achieving good performance levels in MANETs. The goal of this research project is to develop a bandwidth efficient routing protocol that can exploit with the dynamic nature of MANETs to establish and maintain correct routes between any source and destination, while reducing the use of limited resources such as bandwidth and battery life.

 


Performance Evaluation of Wormhole Networks with Finite Buffers and Multiple Virtual Channels

Analytical models for wormhole routed interconnection networks have been widely reported in the literature. However, almost, all of these models have assumed a one flit buffer in each networks node. Nevertheless, routers in practical multicomputers are often equipped with large (and finite) buffer size to hold transiting messages in order to smooth out congestion. This research aims to develop analytical models for wormhole-routed k-ary n-cube networks with finite size buffers.  Currant interconnection networks exploit the concept of virtual channels not only to avoid deadlock situations but also to better utilize the physical bandwidth. Almost all models that have considered virtual channels have used the method proposed by Dally to capture the effects of virtual channels multiplexing. However, it has been revealed that Dally’s method, is accurate only under low traffic. This is due to the statistical similarities of different queuing systems under low traffic rates. The accuracy of the method degrades under moderate and high traffic conditions. This study aims to further investigate the effects of virtual channel multiplexing on network performance using the analytical approach.

 


Past Research

 

Scalable Algorithms for Broadcast and Multicast in Mesh Networks

The mesh has been recognized as one of the most suitable networks for large-scale multicomputers due to its ease of implementation, high scalability, and ability to exploit communication locality. In this work, a new routing approach, the Coded Path Routing (CPR), will be used as a new framework for designing efficient collective algorithms, e.g.  broadcast and multicast, for the mesh. In the first stage of this research, new  broadcast algorithms for the 2 and 3-D mesh are  proposed. These algorithms can exploit  advanced system features, including the multiport model, routing adaptivity, and virtual channels. An extensive comparative study will be performed using analytical and simulation models against existing algorithms that use the common unicast and multidestination-based approaches. In the second stage, new  algorithms for multicast in the 2D and 3D mesh will be proposed and compared to the previous well-known algorithm.

 


Fault-Tolerant Replication Algorithms in Distributed Systems

Replication is a key to providing good performance, high availability, and fault tolerance. In our research we study fault tolerant dynamic data replication in distributed systems. We aim at designing data replication algorithms, developing fault tolerant techniques capable of providing high availability in presence of system failures, and analyzing the performance of these algorithms and techniques. We also study the application of such algorithms in areas like the Internet, Multimedia servers, and mobile computers.
 

 

Performance Modelling and Analysis of Routing Algorithms with Deadlock Recovery Strategies

Deadlock recovery as a viable alternative to deadlock avoidance has recently gained consideration in the scientific community. It has been shown that deadlocks are quite rare except when the network is close to saturation. Thus the hardware dedicated for deadlock avoidance is not necessary most of the time. This consideration has motivated several researchers to propose different routing algorithms based on regressive or progressive deadlock recovery methods. Except studies that have resorted to simulation to evaluate the performance benefits of the deadlock recovery routing algorithms, there has been hardly any work that describes analytical models for fully adaptive routing algorithms with deadlock recovery. This research is intended to contribute towards filling this gap by presenting new analytical models for fully adaptive routing based on deadlock recovery.

 

 

Parallel Algorithms in Hierarchical and Optical Networks

In this research, we propose a new hierarchical interconnection network, referred to as the arrangement-star, deriving many of its topological and performance properties from its constitutes the well-known star and arrangement graphs. We construct a framework for the development of efficient algorithms on this new network. We extend the algorithmic framework to another recently-proposed hierarchical topologies including the optical transpose system networks (or OTIS networks). Our research aims to show that our algorithmic framework enables hierarchical networks to outperform their flat counterparts, including mesh, k-ary n-cubes, and hypercubes.

 


Performance Modelling/Evaluation of Wormhole-Routed Networks under Non-Uniform Traffic

All the performance models proposed for direct wormhole-routed networks have used uniform message traffic and most of them assume deterministic routing. We are studying the impact of the non-uniformities in message traffic on the performance of wormhole-routed k-ary n-cubes using analytical models. Our focus is adaptive routing, as such routing algorithms are getting popular in practice. We have been studying three well-known non-uniform traffic patterns that have already been examined using simulation. They include traffic generated by hot-spots, matrix-transpose and digit/bit reversal.

 


Probability-Based Fault-Tolerant Routing Algorithms

A routing algorithm specifies how a message selects a path to cross from source to destination, and has great impact on network performance. As the network size scales up the probability of processor and link failure also increases. It is therefore essential to design fault-tolerant routing algorithms that allow messages to reach their destinations even in the presence of faulty components (links and processors) . This work focuses on the development of efficient fault tolerant routing algorithms using probabiltistic concepts for unicast and broadcast communication on direct  networks, including hypercubic-based and product interconnection networks.

 


Networks for Large-Scale Parallel Multimedia Servers

Traditional networks employed in existing parallel computers have been optimised for text data (or best-effort traffic) only. As a result, they cannot provide guaranteed Quality of Service (QoS) for the emerging multimedia applications, which combine audio, video and text. The objective of this research is to design a high-performance interconnection network suitable for large-scale parallel multimedia servers and evaluate its performance.



Performance Modelling and Evaluation of Broadcast Communication

Although many broadcast/multicast algorithms have been proposed for wormhole-routed networks over the past decade, there has been hardly any study that proposes an analytical model for these algorithms. This research investigates the impact of different broadcast algorithms on the wormhole-routed network under various traffic patterns through analytical modelling. We will study and compare the behaviour of the network using either unicast-based or multidestination-based broadcast algorithms and looking for a trade-off between minimisation of start-up latencies and minimisation of network and blocking latencies.