In this thesis, we propose a power saving strategy based on tree splitting algorithm in wireless sensor network with multiple packet reception. We concentrate on the case that maximum queue size is 1. We derive both analytical results and simulation results. We use theory of Markov chain to analyze the evolution of the system state. In addition, we propose to use Renewal theory to calculate the throughput. Furthermore, we obtain the average system size, the packet blocking probability, and the average packet delay. Because the network model is distributed, we can¡¦t understand the state of network all the time. So we use the length of last collision resolution cycle to predict the length of next cycle, and determine the sleeping time by the predicted length of next cycle to implement power saving. At last we will use the simulation result to show the performance of our power saving strategy.

The Metro Ethernet network (MEN) expands the advantages of Ethernet to cover areas wider than LAN. MENs running Ethernet Services as specified by the Metro Ethernet Forum (MEF) are known as Carrier Ethernet Networks (CENs). CENs can cover not only metro areas, but it can expand to cover global areas by connecting multiple MENs. Next-generation CENs are expected to support 100 GbE. With arising technologies for Ultra Long-haul (ULH) networks the bandwidth bottleneck of CENs is shifting to other areas like the transport layer protocol (such as the Transport Control Protocol or TCP) and the chip-to-chip channel capacity found at the network edge, which in general has an electrical backplane. Traditional TCP is well known to have difficulties reaching the full available bandwidth, due to its inefficient AIMD mechanisms under a high-delay-bandwidth-product environment. At the network edge, network equipment with electrical backplanes poses many problems including inductive-capacitive effects that limit its bandwidth. These are the two main issues addressed in this work. To resolve the transport layer issue, this work proposes a transport protocol that fully utilizes the available bandwidth while preserving TCP-friendliness and providing QoS support that is compatible with Ethernet Services. It can guarantee throughputs above the Committed Information Rate (CIR), which is specified in the Service Level Agreement (SLA). To resolve the physical layer limitations, a novel optical coupling technique is examined to encourage the use of optical backplanes for network-edge and core technology. The proposed technique consists of aligning the normal of the laser emission plane, waveguide plane and the normal of the photodetector active region plane with the purpose of reducing optical power loss caused by common methods of light manipulation. By addressing the shortcomings of both Traditional TCP and electrical backplane technology the overall throughput can be significantly increased.

In this dissertation, I examine how making infrastructure visible affects users' engagement with that infrastructure, through the case study of home networking. I present empirical evidence of the visibility issues that home networks present to users and how these results informed the design of a prototype called Kermit to visualize aspects of the home network. Through my implementation and evaluation of Kermit, I derive implications for making infrastructure visible in ways that enable end-users to manage and understand the systems they use everyday. I conclude with suggestions for future work for making home networks, and infrastructure more generally, more visible.

Thesis (Ph.D.(Computer Science))--University of Pretoria, 2009. / Abstract in English. Includes bibliographical references.

It is estimated that networked devices consumed about 150 TWh of electricity in 2006 in the U.S. which has cost around $15 billion and contributed about 225 billion lbs of CO 2 to greenhouse gas emissions. About 13.5% of this energy is consumed by network equipment such as switches and routers. This thesis addresses the energy consumption of Ethernet, and designs and evaluates improvements on existing methods to reduce the energy consumption of Ethernet links and switches. Energy Efficient Ethernet (EEE) is an emerging IEEE 802.3 standard which allows Ethernet links to sleep when idle. In this thesis, a performance evaluation of EEE is completed. This evaluation replicates previous work by Reviriego et al. in an independent manner. The performance evaluation shows that EEE overhead results in less energy savings than expected. A new method based on Packet Coalescing is developed and evaluated to improve the energy efficiency of EEE. Packet Coalescing bursts packets such that EEE overhead is minimized. The results show that EEE with Packet Coalescing for 10 Gb/s Ethernet can achieve very close to ideal (or energy proportional) performance at the expense of an insignificant added per packet delay. Periodically Paused Switched Ethernet (PPSE) was previously proposed and prototyped by Blanquicet and Christensen in 2008. PPSE uses periodically sent notification packets to halt packet transmission into a LAN Switch and thus allowing the switch to sleep periodically. In this thesis, a first performance evaluation of PPSE is completed. The evaluation in this thesis shows that a PPSE for 10 Gb/s Ethernet LAN Switches achieves either significant energy savings at the expense of an excessive packet delay, or less than expected savings with a less than human response time added per-packet delay. An improvement to PPSE (Adaptive PPSE) is proposed and developed based on an adaptive policy. The adaptive policy considers past traffic load to determine whether to put the switch to sleep or not. The evaluation shows that Adaptive PPSE can achieve very close to ideal performance at the expense of an added average per packet delay which is less than half of the human response time.

M. Tech. Information Networks / This dissertation reports on a prototype implementation of an architecture that seamlessly integrates Wireless Body Area Networks with Web services for ubiquitous healthcare service provisioning. The prototype ubiquitous monitoring system proactively collects body physiological signals of remote patients to recommend diagnostic services. The technologies that are based upon Wireless Body Area Networks and Web services can provide ubiquitous accessibility to variety of services by allowing distributed healthcare resources to be massively reused. This contributes to improving quality of healthcare services and shields individuals from physically moving to locations where healthcare services are provided, except in a critical situation. In addition, the technology can reduce costs of healthcare services by allowing individuals to remotely access services to support their healthcare. Especially our system is designed for ubiquitous monitoring of elderly and patients in recovery (or rehabilitation). The Wireless Body Area Networks - Web services architecture is at crossroad of embedded engineering of hardware, software and networking protocols. Testing of the prototype was carried out on enthusiastic volunteers and it has shown to be an efficient, reliable and support state-of-art service provisioning of ubiquitous healthcare monitoring in health sector.

Ring networks are appropriate for the full range of network levels, including multiprocessor systems, local area computer networks and high speed backbones. The most well known and widely implemented examples are the IBM token ring and FDDI networks. Ring networks have the advantages of high channel utilisation and bounded delay if an n-limited service policy is used. The packet transfer delay, defined as the average time a packet spends in the network from the time it is generated until the time it is received at its destination node, improves with the number of rings on which a node is connected. However, many ring connections are not economically feasible since the cost of the ring interface increases with the number of rings. There has been an abundance of previous work on single token ring networks. A number of papers on slotted rings, register insertion rings and more complex ring architectures have also been published. However, there is very little existing literature on multiple ring networks as well as ring networks in clustered traffic environments, i.e. where nodes from the same cluster tend to communicate more with each other than with other nodes in the network. This thesis focuses on two network topologies that make use of multiple rings and are well suited to clustered traffic environments: the two-connected multiple ring (2-MR) and the destination removal double ring (DRDR). For the 2-MR network, three different practical token-based protocols are investigated in an attempt to optimise performance. It is further shown that significant performance improvements can be achieved by employing a slotted ring protocol rather than the token ring protocol. The DRDR network is also examined and its performance compared to the aforementioned architectures. For each of the six cases, both random and clustered traffic patterns are considered and compared. Analytical results are derived which are verified by results obtained from computer simulations. Furthermore, we look at exact methods of analysing ring networks. A mean value analysis of a single token ring network with a I-limited service discipline is performed, which clearly shows the complexity exact methods introduce. Finally, although it has been stated in the literature that an exact analysis of a multiple symmetrical token ring network is intractable, we present a novel Markov chain approach that gives exact results for near zero loads. / Thesis (M.Sc.-Electronic Engineering)-University of Natal, 1998.

No abstract / Thesis (M.Sc.-Electronic Engineering)-University of Natal, 1992.

No description available.

The Internet Engineering Task Force (IETF) has recently released routing standards that allow deployment of TCP/IP local area networks (LANs) onboard a moving vehicle and yet maintain permanent connectivity of the onboard LAN to the Internet via a vehicular mobile router. This recent development opens up new opportunities for providing efficient mobile computing for users on the move, especially for commuters traveling on public transports. Supporting real-time communications, e.g. IP Telephony, on-line video on demand, etc., over such onboard mobile networks is the main motivation of this thesis. Due to the volatility of the wireless bandwidth available to connect the moving LAN to the Internet at different locations of the trip, supporting on-line services that require bandwidth guarantees becomes a challenging task. The main problem investigated is how to provide bandwidth guarantee efficiently, effectively, and in a scalable manner in the context of moving onboard networks. To achieve the goal, a systematic approach is taken that involves (i) designing a signalling protocol that allows transparent bandwidth reservation for the aggregate demand of all onboard users in the vehicle, and (ii) proposing effective aggregation and bandwidth reservation policies that aim to maximize the chances of successful reservation and minimize the bandwidth and processing overhead in critical network elements. Mathematical models are derived to evaluate the performance of proposed solutions. These models are validated using discrete event simulation. One important conclusion reached is that onboard mobile communication provides significant aggregation and centralized management opportunities that must be exploited to provide a scalable solution to the bandwidth guarantee problem in mobile communications. The techniques proposed and analyzed in this thesis to exploit such aggregation opportunities constitute the original contribution to knowledge.