River stage or flow rates are required for the design and evaluation of hydraulic structures. Most river reaches are ungauged and a methodology is needed to estimate the stages, or rates of flow, at specific locations in streams where no measurements are available. Flood routing techniques are utilised to estimate the stages, or rates of flow, in order to predict flood wave propagation along river reaches. Models can be developed for gauged catchments and their parameters related to physical characteristics such as slope, reach width, reach length so that the approach can be applied to ungauged catchments in the region. The objective of this study is to assess Muskingum-based methods for flow routing ill ungauged river reaches, both with and without lateral inflows. Using observed data, the model parameters were calibrated to assess performance of the Muskingum flood routing procedures and the Muskingum-Cunge method was then assessed using catchment derived parameters for use in ungauged river reaches. The Muskingum parameters were derived from empirically estimated variables and variables estimated from assumed river cross-sections within the selected river reaches used. Three sub-catchments in the Thukela catchment in KwaZulu-Natal, South Africa were selected for analyses, with river lengths of 4, 21 and 54 km. The slopes of the river reaches and reach lengths were derived from a digital elevation model. Manning roughness coefficients were estimated from field observations. Flow variables such as velocity, hydraulic radius, wetted perimeters, flow depth and top flow width were determined from empirical equations and cross-sections of the selected rivers. Lateral inflows to long river reaches were estimated from the Saint-Venant equation. Observed events were extracted for each sub-catchment to assess the Muskingum-Cunge parameter estimation method and Three-parameter Muskingum method. The extracted events were further analysed using empirically estimated flow variables. The performances of the methods were evaluated by comparing both graphically and statistically the simulated and observed hydrographs. Sensitivity analyses were undertaken using three selected events and a 50% variation in selected input variables was used to identify sensitive variablesThe performance of the calibrated Muskingum-Cunge flood routing method using observed hydrographs displayed acceptable results. Therefore, the Muskingum-Cunge flood routing method was applied in ungauged catchments, with variables estimated empirically. The results obtained shows that the computed outflow hydrographs generated using the Muskingum-Cunge method, with the empirically estimated variables and variables estimated from cross-sections of the selected rivers resulted in reasonably accurate computed outflow hydrographs with respect to peak discharge, timing of peak flow and volume. From this study, it is concluded that the Muskingum-Cunge method can be applied to route floods in ungauged catchments in the Thukela catchment and it is postulated that the method can be used to route floods in other ungauged rivers in South Africa. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.

Infrastructure wireless mesh networks (IWMNs) provide inexpensive deployment, flexible extension of wireless infrastructure, and easy access to the Internet. With multiple radios at each node, a capacity per node improves by transmitting over these radios simultaneously using orthogonal channels. However, without properly addressing the problem of channel assignment and routing for those nodes that form wireless infrastructures, the resulting network throughput and reliability are unlikely to meet the requirements of those highly demanding, media distribution applications. On a particular channel, poor resource allocation at a given access point/gateway of the underlying IWMN can amplify the problem even further. Motivated by these problems, we develop, based on the theory of network coding, a set of alternative solutions that addresses the above issues. We first introduce a sub-optimal solution to the joint problem of network coding, channel assignment and link scheduling for throughput optimization in the multi-channel multi-radio IWMN. We mathematically formulate the problem as a linear program, taking into account opportunistic overhearing, among other constraints. Based on this formulation, we develop a sub-optimal, auction-based algorithm for network throughput optimization. Simulation results reveal the effectiveness of our algorithm in exploiting multiple radios and channels while coping with fairness issues arising from auctions. The proposed solution also shows promising gains over traditional routing solutions. Our experimental results on an 802.11 testbed further confirm these results. The second part of this thesis then presents three AP/gateway-oriented solutions that address the link-level issues related to radio resource allocation at a particular AP/gateway node of the underlying IWMN, which operates on a given channel serving a set of wireless clients. Since the last-hop wireless link is normally a bottleneck of the IWMN, the key idea underlying all the proposed solutions is to use a version of network coding at the bottlenecked AP/gateway. We use Markov chains and the probability theory to derive several performance measures related to media distribution for both uplink and downlink applications. Via extensive simulations, we show the promising delay and reliability gains of the network-coding based schemes over the traditional schemes without network coding.

Despite the world-changing success of the Internet, shortcomings in its routing and forwarding system have become increasingly apparent. One symptom is an escalating tension between users and providers over the control of routing and forwarding of packets: providers understandably want to control use of their infrastructure, and users understandably want paths with sufficient quality-of-service (QoS) to improve the performance of their applications. As a result, users resort to various “hacks” such as sending traffic through intermediate end-systems, and the providers fight back with mechanisms to inspect and block such traffic. To enable users and providers to jointly control routing and forwarding policies, recent research has considered various architectural approaches in which provider- level route determination occurs separately from forwarding. With this separation, provider-level path computation and selection can be provided as a centralized service: users (or their applications) send path queries to a path service to obtain provider- level paths that meet their application-specific QoS requirements. At the same time, providers can control the use of their infrastructure by dictating how packets are forwarded across their network. The separation of routing and forwarding offers many advantages, but also brings a number of challenges such as scalability. In particular, the path service must respond to path queries in a timely manner and periodically collect topology information containing load-dependent (i.e., performance) routing information. We present a new design for a path service that makes use of expensive pre- computations, parallel on-demand computations on performance information, and caching of recently computed paths to achieve scalability. We demonstrate that, us- ing commodity hardware with a modest amount of resources, the path service can respond to path queries with acceptable latency under a realistic workload. The ser- vice can scale to arbitrarily large topologies through parallelism. Finally, we describe how to utilize the path service in the current Internet with existing Internet applica- tions.

Terrestrial free-space optical (FSO) communication uses visible or infrared wavelengths to broadcast high speed data wirelessly through the atmospheric channel. The performance of terrestrial FSO channel mainly depends on the local atmospheric conditions. Ad hoc networks offer cost-effective solutions for communications in areas where infrastructure is unavailable, e.g., intelligent transport system, disaster recovery and battlefield scenarios. Traditional ad hoc networks operate in the radio frequency (RF) spectrum, where the available bandwidth faces the challenge of rapidly increasing demands. FSO is an attractive alternative for RF in ad-hoc networks because of its high bandwidth and interference-free operation. This thesis investigates the influencing factors for routing traffic from given s-d pair while satisfying certain Quality of Services in terrestrial FSO ad hoc mesh networks under the effect of stochastic atmospheric turbulence. It starts with a comprehensive review of FSO technology, including the history, application, advantages and limitations. Subsequently the principle of operation, the building blocks and safety of FSO communication systems are discussed. The physics of atmosphere is taken into account to investigate how propagation of optical signals is affected in terrestrial FSO links. A propagation model is developed to grade the performance and reliability of the FSO ad hoc links in the network. Based on that model and the K-th shortest path algorithm, the performance of the path with highest reliability, the path with a second highest possible reliability and an independent path with no common links shared with the former two paths, were compared according to the simulation scenarios in node-dense area and node-sparse area. Matlab simulation shows that the short/long range dependent transmission delay are positively proportional to number of hops of the paths. Lower path reliability only dominate the cause of severe delay when traffic flow approaches near its upper link capacity in node-sparse area. In order to route traffic from given s-d pairs with satisfying certain Quality of Services, the path with highest reliability may not be the best choices since they may hold more hops which will degrade the QoS. Meanwhile, in case of exponential traffic congestion, it is recommended that both traffic demand and traffic flow propagating through the links should be pressed below a value close to the effective capacity, where the nonlinearity of the transmission delay curve starts to obviously aggravate.

The continues growth in aviation and passenger numbers is putting more pressure on airports to become more efficient in order to reduce the number of delays due to external factors such as weather, pilot deviation/errors and airport maintenance traffic. As major hubs (e.g. Heathrow, New York or Paris) expand in size to accommodate more traffic; aircraft surface movement and management become more complex and the margin for error is even lower. The traditional airport traffic management tools in large airports are increasingly stretched to the limit in meeting safety and traffic throughput requirements. This presents a huge challenge to the efficiency of airport operations because of the increased number of departures and arrivals at those airports. New technology for surface movement needs to be implemented in order to increase the safety and airport capacity. The federal aviation authorities in the USA was first to introduce the concept of Advanced Surface Movement Guidance and Control System (A-SMGCS) to address this problem in commercial airdrome operations. The system facilitates pilot recognition of the route designated by the traffic controllers and uses warning information to make them aware of any potential deviations/incursions. The system is introduced to enhance the efficiency of surface movement by increasing the aircraft taxiing speed and reducing any pilot errors during bad weather conditions. This thesis focuses on the surface guidance system for aircraft equipped with head-up display. A simulation model of the virtual environment using FlightGear and Simulink is developed based on the study of a moving map and surface guidance system for Head-Up Display (HUD) to assign the route, guide the aircraft on the designated taxiway and avoid potential conflict with other aircraft. A method of generating an airport in FlightGear and driving an airport moving map to rotate and move is also illustrated which includes the data processing flow chart and system flow chart. The Ordnance Survey National Grid and world coordinate system is discussed and used to transform from GPS latitude and longitude data to the position on Nation Grid. There is also an explanation of the 3D viewing process to generate the virtual taxiway geometries on the HUD. The communication between the traffic console and airplane is also discussed.

Infrastructure wireless mesh networks (IWMNs) provide inexpensive deployment, flexible extension of wireless infrastructure, and easy access to the Internet. With multiple radios at each node, a capacity per node improves by transmitting over these radios simultaneously using orthogonal channels. However, without properly addressing the problem of channel assignment and routing for those nodes that form wireless infrastructures, the resulting network throughput and reliability are unlikely to meet the requirements of those highly demanding, media distribution applications. On a particular channel, poor resource allocation at a given access point/gateway of the underlying IWMN can amplify the problem even further. Motivated by these problems, we develop, based on the theory of network coding, a set of alternative solutions that addresses the above issues. We first introduce a sub-optimal solution to the joint problem of network coding, channel assignment and link scheduling for throughput optimization in the multi-channel multi-radio IWMN. We mathematically formulate the problem as a linear program, taking into account opportunistic overhearing, among other constraints. Based on this formulation, we develop a sub-optimal, auction-based algorithm for network throughput optimization. Simulation results reveal the effectiveness of our algorithm in exploiting multiple radios and channels while coping with fairness issues arising from auctions. The proposed solution also shows promising gains over traditional routing solutions. Our experimental results on an 802.11 testbed further confirm these results. The second part of this thesis then presents three AP/gateway-oriented solutions that address the link-level issues related to radio resource allocation at a particular AP/gateway node of the underlying IWMN, which operates on a given channel serving a set of wireless clients. Since the last-hop wireless link is normally a bottleneck of the IWMN, the key idea underlying all the proposed solutions is to use a version of network coding at the bottlenecked AP/gateway. We use Markov chains and the probability theory to derive several performance measures related to media distribution for both uplink and downlink applications. Via extensive simulations, we show the promising delay and reliability gains of the network-coding based schemes over the traditional schemes without network coding.

Consumer electronics such as cellular phones and portable computers with short-range communication capabilities have enabled the large-scale information dissemination through user mobility and contact, without the assistance of communication infrastructures. In such a new communication paradigm, one challenge is to determine when and how to forward a message to the destination, possibly through a series of third parties. This problem has attracted a lot of attention in the literature lately, with proposals ranging from epidemic to single or multi-copy spray and wait or focus strategies. However most existing work assumed independent or identically distributed mobility. Observing most human mobility and interaction are interest-driven in the real world, in this research, we evaluate the performance of these schemes with an interest-driven mobility model. We further propose to take the user interest into account when determining routing strategies to further improve the performance of these schemes for mobile social networks. Simulation results have demonstrated the efficacy of the interest-aware routing strategies. / Graduate

This thesis presents a protocol for intervehicle communication for use in Vehicular Ad Hoc Networks (VANET). VANET is a natural extension of mobile ad hoc networks (MANET) in which the restrictions related to power and mobility are relaxed. The routing protocols used for MANETs are generally dependent on the state of the network. With changes in the network topology, routing messages are generated so that the states of the routers in the network are updated. In the case of VANETs, in which the level of node mobility is high, message-routing overhead has serious implications for the scalability and throughput of the routing protocol. This thesis introduces criteria that are recommended for use when protocols are designed for VANET applications and presents the Selected Node Geographic Forwarding (SNGF) protocol. The SNGF protocol implements controlled flooding in an efficient manner in order to reduce unnecessary communication overhead. The protocol has a destination discovery mechanism that allows it to initiate correspondence between nodes without reliance on static location services. The protocol avoids formation of clusters by using the concept of selective forwarding, thus providing the advantages of cluster based approaches without actually forming one itself. It effectively deals with blind flooding by introducing a comprehensive retransmission time delay in the nodes. This retransmission delay favors the nodes in the direction of the destination and prevents other nodes from retransmitting the same message. The SNGF protocol does not use routing tables, which require frequent updates in mobile networks, instead it relies on directing the messages to geographic locations which are forwarded by any available intermediary nodes. The protocol also provides techniques for handling network fragmentation which can be a frequent problem in vehicular networks. It is capable of delayed message transmission and multiple route discovery in the case of the non-availability of the shortest path to the destination. To evaluate the performance of the SNGF protocol, an extensive study of mobile networks was conducted using the NS2 simulator. The simulation results demonstrate the reachability of the protocol, its scalability advantages and its total independence from location services. The SNGF protocol allows each participating node to operate independently of other nodes in the network. Nodes in the network are able to communicate with other nodes without ever becoming dependent on intermediary nodes. This feature opens new possibility for individual node based application development in ad hoc networks. The traffic profiling is described as it would be observed by an independent node participating in VANET using the SNGF protocol. The node communicates with other nodes and collects relevant data through the discourse capability of SNGF. The data collected by the node is viewed as a snapshot in time of the traffic conditions down the road based upon which future traffic condition is predicted. Traffic profiling is investigated for different levels of VANET deployment. The simulation results show that the proposed method of traffic profiling in a VANET environment using the SNGF protocol is viable for even lower levels of deployment.

Delay-tolerant networking (DTN) has recently received considerable attention from the research community. This type of networks is characterized by frequent disconnections due to propagation phenomena, node mobility, and power outages. Thus, the complete path between the source and the destination may never have existed. This context requires the design of new communication paradigms and techniques that will make communication possible in these environments. To achieve message delivery, researchers have proposed the use of store-carry-and-forward protocols, whereby a node may store the message and carry it until an appropriate forwarding opportunity arises. Many flooding-routing schemes have been proposed for DTNs in order to increase the probability of message delivery. However, these schemes suffer from excessive energy consumption, severe contention that significantly degrades their performance, especially if we account for the fact that each node could be a hand-held and battery-powered device with stringent buffer size limitation. With such buffer limitations at the DTN nodes, message drop/loss could happen due to buffer overflow. In order to address the problem and improve the performance of DTNs, this thesis focuses on two main design objectives; first, the design and evaluation of new multi-copy routing schemes; second, the design and evaluation of new scheduling and dropping policies to reduce message drop/loss due to buffer overflow. To fulfill the first objective, a protocol called Self Adaptive Routing Protocol (SARP) is introduced. It is a multi-copy scheme designed to suit resource-sufficient DTNs. Based on SARP, two multi-copy routing schemes are further developed to suit resource-limited DTNs, in which compensating the traffic demand become a challenge: i) the Self Adaptive Utility-based Routing Protocol (SAURP), ii) and the Adaptive Reinforcement based Routing Protocol (ARBRP). The introduced protocols form a new framework of DTNs aiming to significantly reduce the resource requirements of flooding-based routing schemes. Each introduced scheme has its own way of exploring the possibility of taking mobile nodes as message carriers in order to increase the delivery ratio of the messages. In SAURP, the best carrier for a message characterized by jointly considering the inter-contact time that is obtained using a novel contact model and the network status, such as including wireless link condition and nodal buffer availability. In ARBRP, the routing problem is solved by manipulating a collaborative reinforcement learning technique, where a group of nodes can cooperate with each other to make a forwarding decision for the stored messages based on a cost function at each contact with another node. ARBRP is characterized by not only considering the contact time statistics, but also looks into the feedback on user behavior and network conditions, such as congestion and buffer occupancy sampled during each previous contact with any other node. The thesis argues and proves that the nodal movement and the predicted collocation with the message recipient can serve as meaningful information to achieve an intelligent message forwarding decision at each node. Therefore, the introduced protocols can achieve high efficiency via an adaptive and intelligent routing mechanism according to network conditions. To fulfill the second objective, we further enhanced the performance of DTN routing by introducing message scheduling and dropping policies such that the delivery ratio is increased and/or the delivery delay is reduced. This thesis investigates new buffer management and scheduling policies to improve the performance of flooding and utility-based forwarding routing in DTNs, such that the forwarding/dropping decision can be made at a node during each contact for either optimal message delivery ratio or message delivery delay. To examine their effectiveness, the introduced protocols and the buffer management and scheduling policies have been implemented and compared to a number of existing counterpart approaches. A near-realistic mobility model is used for testing. A number of scenarios are used to evaluate the performance of the introduced techniques in terms of delivery delay, ratio, and the number of transmissions performed.

In this study, we consider the Turkish postal delivery system and develop an effective solution approach for the combined hub location and routing problem where the location of hub nodes are determined, the nonhub regional postal offices are allocated to the hubs, and the optimal set of routes are determined for each hub. Since the realized post-routing distances between origin-destination pairs are different from those used in the hub-location model, we develop an algorithm that finds the route-compatible hub configuration and allocation paths. The algorithm is the one that iterates between the hub-location phase and a routing phase. Our strategy consists of updating the distances used in the first phase in order to produce a solution that contains the cognition of routes. Some special structures in the routed network are also identified and used for improving the solution. Computational experience is reported.