Achieving Soft Real-time Guarantees for Interactive Applications in Wireless Mesh Networks

The use of 802.11-based multi-hop wireless mesh networks for Internet access is extensive and growing. The primary advantages of this approach are ease of deployment and lower cost. However, these networks are designed for web and e-mail applications. Highly interactive applications, such as multiplayer online games and VoIP, with their requirements for low delay, present significant challenges to these networks. In particular, the interaction between real-time traffic and TCP traffic tends to result in either a failure of the real-time traffic getting its needed QoS or the TCP traffic unnecessarily experiencing very poor throughput. To solve this problem we place real-time and TCP traffic into separate queues. We then rate-limit TCP traffic based on the average queue size of the local or remote real-time queues. Thus, TCP traffic is permitted to use excess bandwidth as long as it does not interfere with real-time traffic guarantees. We therefore call our scheme Real-time Queue-based Rate and Admission Control, RtQ-RAC. Extensive simulations using the network simulator, ns-2, demonstrate that our approach is effective in providing soft real-time support, while allowing efficient use of the remaining bandwidth for TCP traffic

A QoS-aware architecture for mobile internet

Tese de doutoramento InformáticaHoje em dia, as pessoas pretendem ter simultaneamente mobilidade, qualidade de serviço e estar sempre connectados à Internet. No intuito, de satisfazer estes clientes muito exigentes, os mercados das telecomunicações estão a impor novos e dificeis desafios às redes móveis, através da demanda, de heterogeneidade em termos de tecnologias de acesso rádio, novos serviços, niveis de qualidade de serviço adequados aos requisitos das aplicações de tempo real, elevada taxa de utilização do recursos disponiveis e melhor capacidade de desempenho. A Internet foi concebida para fornecer serviços sem qualquer tipo de garantias de qualidade às aplicações, apenas se comprometendo em oferecer o melhor serviço possível. No entanto, nos útlimos anos diversos esforços foram levados a cabo no sentido de dotar a Internet com o suporte à qualidade de serviço. Dos esforços desenvolvidos resultaram dois paradigmas para o suporte da qualidade de serviço: o modelo de Serviços Integrados (Integrated Services - IntServ) e o modelo de Serviços Diferenciados (Differentiated Services - DiffServ). Todavia, estes modelos de qualidade de serviço (QoS) foram concebido antes da existência da Internet móvel, portanto o desenvolvimento destes modelos não teve em consideração a questão da mobilidade. Por outro lado, o protocolo padrão actual para a Internet móvel, o MIPv6, revela algumas limitações nos cenários onde os utilizadores estão constantemente a moverem-se para outros pontos de acesso. Neste tipo de cenários, o MIPv6 introduz tempos de latência que não são sustentáveis para aplicações com requisitos de QoS mais restritos. Os factos revelados, demonstram que existe uma emergente necessidade de adaptar o actual protocolo de mobilidade, e também de adaptar os modelos de QoS, ou então criar modelos alternativos de QoS, para satisfazer às exigências do utilizador de hoje de redes móveis. Para alcançar este objectivo o presente trabalho propõe melhorias no sistema de gestão da mobilidade do protocolo MIPv6 e na gestão de recursos do modelo DiffServ. O MIPv6 foi melhorado para os cenários de micro-mobilidade com a abordagem para micro-mobilidade do F-HMIPv6. Enquanto que, o modelo DiffServ foi melhorado para os ambientes móveis com funcionalidades dinâmicas e adaptativas através da utilização de sinalização de QoS e da gestão distribuida dos recursos. A gestão da mobilidade e dos recursos foi também acoplada na solução proposta com o propósito de optimizar a utilização dos recursos num meio onde os recursos são tipicamente escassos. O modelo proposto é simples, é de fácil implementação, tem em consideração os requisitos da Internet móvel, e provou ser eficiente e capaz de fornecer serviços com QoS de elevada fiabilidade às aplicações.Over the last few years, several network communication challenges have arisen as a result of the growing number of users demanding Quality of Service (QoS) and mobility simultaneously. In order to satisfy these very demanding customers, the markets are imposing new challenges to wireless networks by demanding heterogeneity in terms of wireless access technologies, new services, suited QoS levels to real-time applications, high usability and improved performance. However, the Internet has been designed for providing application services without quality guarantees. That explains why, in the last years several efforts have been made to endow Internet with QoS support. From the developed efforts have resulted two QoS paradigms: Integrated Services (IntServ) which offers the guaranteed service model and the Differentiated Services (DiffServ) which offers the predictive service model. Although these QoS models have been designed before the existence of mobile Internet, so they do not consider the mobility issue. For instance, the guaranteed service model requires that whenever a Mobile Node (MN) wants to move to a new location, the allocated resources in the old path must be released and a new resource reservation in a new path must be made, resulting in extra signaling overhead, heavy processing and state load. Therefore, if handovers are frequent, large mobility and QoS signaling messages will be created in the access networks. Consequently, significant scalability problems may arise with this type of service model. The predicted service model, on the other hand, requires an additional features such as dynamic and adaptive resource management in order to be efficient in a very dynamic network such as a mobile network. A QoS solution for mobile environments must provide the capacity to adapt its resource utilization to a changeable nature of wireless networks because they have a more dynamic behavior due to incoming or outgoing handovers. For this reason, a QoS signalization for dynamic resource provisioning is necessary in order to supply adequate QoS levels to mobile users. On the other hand, the current standard protocol for mobile Internet, Mobile IPv6 (MIPv6), reveals limitations in scenarios where users are constantly moving to another point of attachment. In these situations, MIPv6 introduces latency times that are not sustainable for applications with strict QoS requirements. All things considered, reveal the emerging need to adapt the current standard mobility protocol and QoS models to satisfy today’s mobile user’s requirements. To accomplish this goal, the present work proposes enhancements in terms of the MIPv6 protocol mobility management scheme as well as in DiffServ QoS model resource management. The former was enhanced for micro-mobility scenarios with a specific combination of FMIPv6 (Fast Mobile IPv6) and HMIPv6 (Hierarchical Mobile IPv6) protocols. Whereas, the latter was enhanced for mobile environments with dynamic and adaptive features by using QoS signalization as well as distributed resource management. The mobility and resource management has also been coupled in the proposed solution with the objective of optimizing the resource utilization in a environment where resources are typically scarce. In order to assess model performance as well as its parametrization, a simulation model has been designed and implemented in the Network Simulator version two (NS-2). The model´s performance evaluation has been conducted based on the respective data acquired from statistical analysis in order to validate and consolidate the conclusions. Simulation results indicate that the solution avoids network congestion and starvation of less priority DiffServ classes. Moreover, the results also indicate that bandwidth utilization for priority classes increases and the QoS offered to MN’s applications, in each DiffServ class, remains unchangeable with MN mobility. The proposed model is simple and easy to implement. It considers mobile Internet requirements and has proven to be effective and capable of providing services with highly reliable QoS to mobile applications.Fundação para a Ciência e a Tecnologia (FCT) - Bolsa SFRH/BD/35245/200

A Priority-based Fair Queuing (PFQ) Model for Wireless Healthcare System

Healthcare is a very active research area, primarily due to the increase in the elderly population that leads to increasing number of emergency situations that require urgent actions. In recent years some of wireless networked medical devices were equipped with different sensors to measure and report on vital signs of patient remotely. The most important sensors are Heart Beat Rate (ECG), Pressure and Glucose sensors. However, the strict requirements and real-time nature of medical applications dictate the extreme importance and need for appropriate Quality of Service (QoS), fast and accurate delivery of a patient’s measurements in reliable e-Health ecosystem. As the elderly age and older adult population is increasing (65 years and above) due to the advancement in medicine and medical care in the last two decades; high QoS and reliable e-health ecosystem has become a major challenge in Healthcare especially for patients who require continuous monitoring and attention. Nevertheless, predictions have indicated that elderly population will be approximately 2 billion in developing countries by 2050 where availability of medical staff shall be unable to cope with this growth and emergency cases that need immediate intervention. On the other side, limitations in communication networks capacity, congestions and the humongous increase of devices, applications and IOT using the available communication networks add extra layer of challenges on E-health ecosystem such as time constraints, quality of measurements and signals reaching healthcare centres. Hence this research has tackled the delay and jitter parameters in E-health M2M wireless communication and succeeded in reducing them in comparison to current available models. The novelty of this research has succeeded in developing a new Priority Queuing model ‘’Priority Based-Fair Queuing’’ (PFQ) where a new priority level and concept of ‘’Patient’s Health Record’’ (PHR) has been developed and integrated with the Priority Parameters (PP) values of each sensor to add a second level of priority. The results and data analysis performed on the PFQ model under different scenarios simulating real M2M E-health environment have revealed that the PFQ has outperformed the results obtained from simulating the widely used current models such as First in First Out (FIFO) and Weight Fair Queuing (WFQ). PFQ model has improved transmission of ECG sensor data by decreasing delay and jitter in emergency cases by 83.32% and 75.88% respectively in comparison to FIFO and 46.65% and 60.13% with respect to WFQ model. Similarly, in pressure sensor the improvements were 82.41% and 71.5% and 68.43% and 73.36% in comparison to FIFO and WFQ respectively. Data transmission were also improved in the Glucose sensor by 80.85% and 64.7% and 92.1% and 83.17% in comparison to FIFO and WFQ respectively. However, non-emergency cases data transmission using PFQ model was negatively impacted and scored higher rates than FIFO and WFQ since PFQ tends to give higher priority to emergency cases. Thus, a derivative from the PFQ model has been developed to create a new version namely “Priority Based-Fair Queuing-Tolerated Delay” (PFQ-TD) to balance the data transmission between emergency and non-emergency cases where tolerated delay in emergency cases has been considered. PFQ-TD has succeeded in balancing fairly this issue and reducing the total average delay and jitter of emergency and non-emergency cases in all sensors and keep them within the acceptable allowable standards. PFQ-TD has improved the overall average delay and jitter in emergency and non-emergency cases among all sensors by 41% and 84% respectively in comparison to PFQ model

Resource Allocation in Uplink Long Term Evolution

One of the most crucial goals of future cellular systems is to minimize transmission power while increasing system performance. This master thesis work presents two channel-queue-aware scheduling schemes to allocate channels among active users in uplink LTE. Transmission power, packet delays and data rates are three of the most important criteria critically affecting the resource allocation designs. Therefore, each of these two scheduling algorithms proposes a practical method that assigns resources in such a way so as to optimally maximize data rate and minimize transmission power and packet delays while ensuring the QoS requirements. After converting the resource allocation problem into an optimization problem, the objective function and associated constraints are derived. Due to the contiguity constraint, which is imposed by SC-FDMA in uplink LTE, binary integer programming is employed to solve the optimization problem. Also the heuristic algorithms that approximate optimal schemes are presented to decrease the algorithm complexity

Operational support systems for satellite communications

The role of satellite communications is changing from providing bandwidth linking network operators interconnections towards providing IP enabled communications to end users. This migration from few high-value routes towards many low-value routes means that integration and automation of processes with terrestrial networks becomes critical in driving down unit costs. Integration and automation is necessary on all planes: user, control and management. In satellite communications, management aspects, underpinned by Operational Support Systems (OSS) have received the least research attention, making this a valuable topic for study. In most areas, OSS for satellite systems are similar to other domains. However there are some notable areas of difference which have been the focus of this research. The eTOM business framework, developed by the TMF, has been used to highlight aspects of OSS unique to satellite. Since satellite capacity represents the highest operational cost of a satellite route, effective management while minimising the overhead traffic is critical. The transmission of IP packets is assumed and the real-time measurement of QoS parameters such as packet delay and loss emerged as the most important differences. A number of approaches to QoS measurement are feasible, however the use of trace packets is most promising especially for high network loads. An experiment compares the results from simulations, mathematical models and from a test network, using Poisson and self-similar traffic flows. The relationship between measurement accuracy and trace packet intensity is explored and the measurement response time to steps in traffic load is estimated. It is discovered that measurement accuracy improves as the queue load increases, in contrast to alternative approaches such as sampling of user packets. The response time to steps depends upon the degree of self-similarity and is generally longer than the times recommended by standards. A pragmatic approach to management of different modes is proposed where the measurement method is changed depending on the load

Radio resource allocation and hybrid multiplexing of voice and data over IP in aGSM/GPRS cellular network

Abstract In this study, a first order investigation of the issue of resource allocation between circuit voice, packet data and packet voice was completed. The study was done with reference to the GSM / GPRS air interface. To study the allocation of resources, suitable traffic source models were developed to represent the nature of the traffic offered to the base station subsystem. Circuit voice and packet data were represented using Markovian arrivals and exponentially distributed holding times. Voice over IP was modelled using a two-state Markov modulated Poisson process. The base station subsystem was modelled as a continuous time controller with eight channels (one GSM / GPRS TDMA frame). The radio propagation environment was considered by means of a large-scale propagation model, which would merely alter the load presented to the developed simulator package. From the results of the simulations, it was found that insufficient data resources lead to similar packet delay regardless of the packet size. It was found that if capacity on demand is used, then the data resources could equal the load. In the case of sufficient data channels, with capacity on demand, additional channels have a greater effect on average delay than the probability of it occurring. Prioritisation of VoIP packets did not significantly alter the probability of delay but affected the average packet delay. Packet size had a greater effect on average delay than the probability of delay. In the case of all eight channels being used for VoIP and data, the combined load should not exceed seven erlang, indicating that a higher voice load could be supported with VoIP than with circuit switched voice

Quality of service optimization of multimedia traffic in mobile networks

Mobile communication systems have continued to evolve beyond the currently deployed Third Generation (3G) systems with the main goal of providing higher capacity. Systems beyond 3G are expected to cater for a wide variety of services such as speech, data, image transmission, video, as well as multimedia services consisting of a combination of these. With the air interface being the bottleneck in mobile networks, recent enhancing technologies such as the High Speed Downlink Packet Access (HSDPA), incorporate major changes to the radio access segment of 3G Universal Mobile Telecommunications System (UMTS). HSDPA introduces new features such as fast link adaptation mechanisms, fast packet scheduling, and physical layer retransmissions in the base stations, necessitating buffering of data at the air interface which presents a bottleneck to end-to-end communication. Hence, in order to provide end-to-end Quality of Service (QoS) guarantees to multimedia services in wireless networks such as HSDPA, efficient buffer management schemes are required at the air interface. The main objective of this thesis is to propose and evaluate solutions that will address the QoS optimization of multimedia traffic at the radio link interface of HSDPA systems. In the thesis, a novel queuing system known as the Time-Space Priority (TSP) scheme is proposed for multimedia traffic QoS control. TSP provides customized preferential treatment to the constituent flows in the multimedia traffic to suit their diverse QoS requirements. With TSP queuing, the real-time component of the multimedia traffic, being delay sensitive and loss tolerant, is given transmission priority; while the non-real-time component, being loss sensitive and delay tolerant, enjoys space priority. Hence, based on the TSP queuing paradigm, new buffer managementalgorithms are designed for joint QoS control of the diverse components in a multimedia session of the same HSDPA user. In the thesis, a TSP based buffer management algorithm known as the Enhanced Time Space Priority (E-TSP) is proposed for HSDPA. E-TSP incorporates flow control mechanisms to mitigate congestion in the air interface buffer of a user with multimedia session comprising real-time and non-real-time flows. Thus, E-TSP is designed to provide efficient network and radio resource utilization to improve end-to-end multimedia traffic performance. In order to allow real-time optimization of the QoS control between the real-time and non-real-time flows of the HSDPA multimedia session, another TSP based buffer management algorithm known as the Dynamic Time Space Priority (D-TSP) is proposed. D-TSP incorporates dynamic priority switching between the real-time and non-real-time flows. D-TSP is designed to allow optimum QoS trade-off between the flows whilst still guaranteeing the stringent real-time component’s QoS requirements. The thesis presents results of extensive performance studies undertaken via analytical modelling and dynamic network-level HSDPA simulations demonstrating the effectiveness of the proposed TSP queuing system and the TSP based buffer management schemes

On the Support of Massive Machine-to-Machine Traffic in Heterogeneous Networks and Fifth-Generation Cellular Networks

The widespread availability of many emerging services enabled by the Internet of Things (IoT) paradigm passes through the capability to provide long-range connectivity to a massive number of things, overcoming the well-known issues of ad-hoc, short-range networks. This scenario entails a lot of challenges, ranging from the concerns about the radio access network efficiency to the threats about the security of IoT networks. In this thesis, we will focus on wireless communication standards for long-range IoT as well as on fundamental research outcomes about IoT networks. After investigating how Machine-Type Communication (MTC) is supported nowadays, we will provide innovative solutions that i) satisfy the requirements in terms of scalability and latency, ii) employ a combination of licensed and license-free frequency bands, and iii) assure energy-efficiency and security