The impact of exercise capacity in the atherosclerotic patient: Keep on walking!

__Abstract__ Peripheral arterial disease (PAD) is a manifestation of systemic arteriosclerosis. It is a common disease affecting millions of people. Depending on the age of the investigated population prevalences between 4% to 29% has been reported. It is alarming that the prevalence is expected to rise in the following decades due to the aging of the western population and the increase of risk factors such as diabetes mellitus, obesity and lack of exercise. Patients with PAD are of an increased risk of cardiovascular events and mortality. In addition, they may also experience signifi cant limitations in their physical functioning and impairment in their quality of life. It is important to diagnose patients with PAD early in the course of the disease to provide them optimal treatment as soon as possible in attempting to lower the complication rates, improve morbidity, mortality and subsequent their quality of life. However, symptoms of PAD are diverse. The classical symptoms are intermittent claudication consisted of calf pain provoked by walking and declining at rest. Earlier investigations, on the other hand, have demonstrated a large range of symptoms ranging from no pain at all till pain at rest . A major problem is that between 20% till 50% of the patients are asymptomatic . Commonly, to identify patients with PAD the resting ankle brachial index (ABI) is used. This is the ratio between the ankle’s systolic blood pressure, measured at the dorsalis pedis or posterial tibial arterie using a Doppler ultrasonic instrument, and the systolic blood pressure at the arm. An ABI below 0.90 is associated with angiographic stenosis of more than 50% . According to the guidelines a resting ABI of < 0.90 is defi ned as PAD. Several studies have found that an ABI of < 0.90 is associated with an increased risk of cardiovascular diseases and mortality. Moreover it can also be used for prognostic risk stratifi cation

An energy efficient position based Adaptive real-time routing protocol for WSNs

Devices for Wireless Sensor Networks (WSN) are limited by power and thus routing protocols should be designed with this constrain in mind. This paper presents and evaluates an Energy Efficient Position Based Adaptive Real-Time Routing protocol (EFPBARP) as a novel, real-time, position based and energy efficient routing protocol. EFPBARP is a lightweight protocol that reduces the number of nodes which receive the RF signal using a novel Parent Forwarding Region (PFR) algorithm. EFPBARP as a Geographical Routing Protocol (GRP) reduces the number of forwarding nodes and thus the traffic and packet collision in the network. A series of performance evaluations through Matlab and Omnet++ simulations show significant improvements in network performance parameters and total energy consumption over CTP and Directed Flooding Routing Protocol (DFRP)

Spectrum Monitoring Algorithms for Wireless and Satellite Communications

Nowadays, there is an increasing demand for more efficient utilization of the radio frequency spectrum as new terrestrial and space services are deployed resulting in the congestion of the already crowded frequency bands. In this context, spectrum monitoring is a necessity. Spectrum monitoring techniques can be applied in a cognitive radio network, exploiting the spectrum holes and allowing the secondary users to have access in an unlicensed frequency band for them, when it is not occupied by the primary user. Furthermore, spectrum monitoring techniques can be used for interference detection in wireless and satellite communications. These two topics are addressed in this thesis. In the beginning, a detailed survey of the existing spectrum monitoring techniques according to the way that cognitive radio users 1) can detect the presence or absence of the primary user; and 2) can access the licensed spectrum is provided. Subsequently, an overview of the problem of satellite interference and existing methods for its detection are discussed, while the contributions of this thesis are presented as well. Moreover, this thesis discusses some issues in a cognitive radio system such as the reduction of the secondary user's throughput of the conventional \listen before talk" access method in the spectrum. Then, the idea of simultaneous spectrum sensing and data transmission through the collaboration of the secondary transmitter with receiver is proposed to address these concerns. First, the secondary receiver decodes the signal from the secondary transmitter, then, removes it from the total received signal and finally, applies spectrum sensing in the remaining signal in order to decide if the primary user is active or idle. The effects of the imperfect signal cancellation due to decoding errors, which are ignored in the existing literature, are considered in our analysis. The analytical expressions for the probabilities of false alarm and detection are derived and numerical results through simulations are also presented to validate the proposed study. Furthermore, the threat of interference for the satellite communications services is studied in this thesis. It proposes the detection of interference on-board the satellite by introducing a spectrum monitoring unit within the satellite transponder. This development will bring several benefits such as faster reaction time and simplification of the ground stations in multi-beam satellite systems. Then, two algorithms for the detection of interference are provided. The first detection scheme is based on energy detector with signal cancellation exploiting the pilot symbols. The second detection scheme considers a two-stage detector, where first, the energy detector with signal cancellation in the pilot domain is performed, and if required, an energy detector with signal cancellation in the data domain is carried out in the second stage. Moreover, the analytical expressions for the probabilities of false alarm and detection are derived and numerical results through simulations are provided to verify the accuracy of the proposed analysis. Finally, this thesis goes one step further and the developed algorithms are evaluated experimentally using software defined radios, particularly universal software radio peripherals (USRPs), while it concludes discussing some open research topics

QoS provisioning and mobility management for IP-based wireless LAN

Today two major technological forces drive the telecommunication era: the wireless cellular systems and the Internet. As these forces converge, the demand for new services, increasing bandwidth and ubiquitous connectivity continuously grows. The next-generation mobile systems will be based solely or in a large extent, on the Internet Protocol (IP). This thesis begins by addressing the problems and challenges faced in a multimedia, IP-based Wireless LAN environment. The ETSI HiperLAN/2 system has been mainly selected as the test wireless network for our theoretical and simulation experiments. Apart from the simulations, measurements have been taken from real life test scenarios, where the IEEE 802.11 system was used (UniS Test-bed). Furthermore, a brief overview of the All-IP network infrastructure is presented. An extension to the conventional wireless (cellular) architecture, which takes advantage of the IP network characteristics, is considered. Some of the trends driving the 3G and WLANs developments are explored, while the provision of quality of service on the latter for real-time and non-real-time multimedia services is investigated, simulated and evaluated. Finally, an efficient and catholic Q0S framework is proposed. At the same time, the multimedia services should be offered in a seamless and uninterrupted manner to users who access the all-IP infrastructure via a WLAN, meeting the demands of both enterprise and public environments anywhere and anytime. Thus providing support for mobile communications not only in terms of terminal mobility, as is currently the case, but also for session, service and personal mobility. Furthermore, this mobility should be available over heterogeneous networks, such as WLANs, IJMTS, as well as fixed networks. Therefore, this work investigates issues such as, multilayer and multi-protocol (SIP-Mobile IP-Cellular IP) mobility management in wireless LAN and 3G domains. Several local and global mobility protocols and architectures have been tested and evaluated and a complete mobility management framework is proposed. Moreover, integration of simple yet efficient authentication, accounting and authorisation mechanisms with the multimedia service architecture is an important issue of IP-based WLANs. Without such integration providers will not have the necessary means to control their provided services and make revenue from the users. The proposed AAA architecture should support a robust AAA infrastructure providing secure, fast and seamless access granting to multimedia services. On the other hand, a user wishing a service from the All-IP WLAN infrastructure needs to be authenticated twice, once to get access to the network and the other one should be granted for the required service. Hence, we provide insights into these issues by simulating and evaluating pre-authentication techniques and other network authentication scenarios based on the wellknown IEEE 802.lx protocol for multimedia IP-based WLANs.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

An Analysis of Routing Protocol Metrics in Wireless Mesh Networks

Wireless Mesh Networks (WMN)s play an important role in todays communication and they are expected to increase in proliferation in the field of wireless communication in the near future. Researchers in the area of WMNs address some issues like low throughput and high latency. Routing Protocols in WMNs have a vital role in data communication and the key parameter in all routing protocols is link metrics. In this paper the majority of link metrics in WMNs are studied in different categories. Link-quality and traffic-aware metrics account for most of the metrics, however multi channel network and cognitive radio systems are also considered in detail. In each section, by reviewing the metrics and its performance in detail, summary and comparison tables of link quality metrics are also provided to enable better understanding of this topic

Integrating peer-to-peer functionalities and routing in mobile ad-hoc networks

Mobile Ad-hoc Networks (MANETs) impose strict requirements in terms of battery life, communication overhead and network latency, therefore optimization should be made to applications and services such as domain name service (DNS), dynamic host configuration protocol (DHCP) and session initiation protocol (SIP) if they are to be considered for use on MANETs. Due to the decentralized and self-organizing nature of MANETs, such applications could utilize a distributed name resolution/data storage service. Distributed Hash Tables (DHTs) enable these features by virtually organizing the network topology in a peer-to-peer (P2P) overlay. P2P overlays have been designed to operate on the application layer without knowledge of the underlying network thus causing poor performance. To address this problem, we propose and evaluate two different DHTs integrated with MANET routing in order to optimize the overall performance of MANET communications when P2P applications and services are used. Both architectures share the same functionality such as decentralization, self-reorganization, and self-healing but differ in MANET routing protocol. Performance evaluation using the NS2 simulator shows that these architectures are suited to different scenarios namely increasing network size and peer velocity. Comparisons with other well-known solutions have proven their efficiency with regard to the above requirements

ECG Signal Reconstruction on the IoT-Gateway and Efficacy of Compressive Sensing Under Real-time Constraints

Remote health monitoring is becoming indispensable, though, Internet of Things (IoTs)-based solutions have many implementation challenges, including energy consumption at the sensing node, and delay and instability due to cloud computing. Compressive sensing (CS) has been explored as a method to extend the battery lifetime of medical wearable devices. However, it is usually associated with computational complexity at the decoding end, increasing the latency of the system. Meanwhile, mobile processors are becoming computationally stronger and more efficient. Heterogeneous multicore platforms (HMPs) offer a local processing solution that can alleviate the limitations of remote signal processing. This paper demonstrates the real-time performance of compressed ECG reconstruction on ARM's big.LITTLE HMP and the advantages they provide as the primary processing unit of the IoT architecture. It also investigates the efficacy of CS in minimizing power consumption of a wearable device under real-time and hardware constraints. Results show that both the orthogonal matching pursuit and subspace pursuit reconstruction algorithms can be executed on the platform in real time and yield optimum performance on a single A15 core at minimum frequency. The CS extends the battery life of wearable medical devices up to 15.4% considering ECGs suitable for wellness applications and up to 6.6% for clinical grade ECGs. Energy consumption at the gateway is largely due to an active internet connection; hence, processing the signals locally both mitigates system's latency and improves gateway's battery life. Many remote health solutions can benefit from an architecture centered around the use of HMPs, a step toward better remote health monitoring systems.Peer reviewedFinal Published versio

Towards a scalable routing approach for mobile ad-hoc networks

The Internet is evolving towards a two-fold architecture that will comprise of traditional infrastructure based networks as well as emerging self organised autonomic peripheral networks. Such Internet peripheral networks are being termed as the Internet of things (IoT) whereby smart objects and devices will be connected together in a fully distributed fashion to provide ubiquitous services through pervasive networking. Mobile Ad hoc Networks (MANETs) is regarded as one of the pervasive self-organised networks that will play a major role in autonomic future internet communication. There are several well- known challenges to be addressed in order to enable MANET deployments of large islands of interconnected smart devices. Therefore, in this paper, we present a mathematical model based analysis of various well-known routing protocols for MANETs in order to determine the scalability of these protocols. This paper analyses the scalability of the routing protocols with respect to routing overhead required by approaches while also considering the packet delivery latency, which is an important Quality of Service (QoS) metric

Sensing optimization in cooperative cognitive radio networks

Cooperative spectrum sensing is a key function in cognitive radio networks in order to provide unused spectrum access opportunities and mitigate the impact of interference to the primary networks. Cooperative sensing can incur additional cooperation overhead, increased energy consumption, extra sensing time and delay in heterogeneous networks. In this paper, the sensing time period is optimized to minimize energy consumption in a diverse cooperative network using square law combining decision rule. The evaluation results confirm significant improvement in the sensing time and sensing task energy consumption