A Survey of Quality of Service in Mobile Computing Environments

Accepted versio

Soft Handoff in MC-CDMA Cellular Networks Supporting Multimedia Services

An adaptive resource reservation and handoff priority scheme, which jointly considers the characteristics from the physical, link and network layers, is proposed for a packet switching Multicode (MC)-CDMA cellular network supporting multimedia applications. A call admission region is derived for call admission control (CAC) and handoff management with the satisfaction of quality of service (QoS) requirements for all kinds of multimedia traffic, where the QoS parameters include the wireless transmission bit error rate (BER), the packet loss rate (PLR) and delay requirement. The BER requirement is guaranteed by properly arranging simultaneous packet transmissions, whereas the PLR and delay requirements are guaranteed by the proposed packet scheduling and partial packet integration scheme. To give service priority to handoff calls, a threshold-based adaptive resource reservation scheme is proposed on the basis of a practical user mobility model and a proper handoff request prediction scheme. The resource reservation scheme gives handoff calls a higher admission priority over new calls, and is designed to adjust the reservation-request time threshold adaptively according to the varying traffic load. The individual reservation requests form a common reservation pool, and handoff calls are served on a first-come-first-serve basis. By exploiting the transmission rate adaptability of video calls to the available radio resources, the resources freed from rate-adaptive high-quality video calls by service degradation can be further used to prioritize handoff calls. With the proposed resource reservation and handoff priority scheme, the dynamic properties of the system can be closely captured and a better grade of service (GoS) in terms of new call blocking and handoff call dropping probabilities(rates) can be achieved compared to other schemes in literature. Numerical results are presented to show the improvement of the GoS performance and the efficient utilization of the radio resources

Radio Resource Management for Satellite UMTS. Dynamic scheduling algorithm for a UMTS-compatible satellite network.

The third generation of mobile communication systems introduce interactive Multicast and Unicast multimedia services at a fast data rate of up to 2 Mbps and is expected to complete the globalization of the mobile telecommunication systems. The implementation of these services on satellite systems, particularly for broadcast and multicast applications to complement terrestrial services is ideal since satellite systems are capable of providing global coverage in areas not served by terrestrial telecommunication services. However, the main bottleneck of such systems is the scarcity of radio resources for supporting multimedia applications which has resulted in the rapid growth in research efforts for deriving efficient radio resource management techniques. This issue is addressed in this thesis, where the main emphasis is to design a dynamic scheduling framework and algorithm that can improve the overall performance of the radio resource management strategy of a UMTS compatible satellite network, taking into account the unique characteristics of wireless channel conditions. This thesis will initially be focused on the design of the network and functional architecture of a UMTS -compatible satellite network. Based on this architecture, an effective scheduling framework is designed, which can provide different types of resource assigning strategies. A functional model of scheduler is defined to describe the behaviours and interactions between different functional entities. An OPNET simulation model with a complete network protocol stack is developed to validate the performance of the scheduling algorithms implemented in the satellite network. Different types of traffic are considered for the OPNET simulation, such as the Poisson Process, ONOFF Source and Self Similar Process, so that the performance of scheduling algorithm can be analyzed for different types of services. A novel scheduling algorithm is proposed to optimise the channel utilisation by considering the characteristics of the wireless channel, which are bursty and location dependent. In order to overcome the channel errors, different code rates are applied for the user under different channel conditions. The proposed scheduling algorithm is designed to give higher priority to users with higher code rate, so that the throughput of network is optimized and at the same time, maintaining the end users¿ service level agreements. The fairness of the proposed scheduling algorithm is validated using OPNET simulation. The simulation results show that the algorithm can fairly allocate resource to different connections not only among different service classes but also within the same service class depending on their QoS attributes.Inmarsat Global Ltd. BGAN and the European Space Agency (ESA

High Performance Signal Processing-Based Collision Resolution for Random Access Schemes

Els darrers anys han experimentat un augment de la demanda de serveis interactius per satèl·lit per al gran consum, cobrint serveis fixes i mòbils, tal i com accés de banda ampla, comunicacions màquina-màquina (M2M), supervisió, control i adquisició de dades (SCADA), transaccions i aplicacions de seguretat crítiques. Aquestes xarxes de comunicacions es caracteritzen per tenir una gran població d’usuaris compartint l’amplada de banda amb unes condicions de tràfic molt dinàmiques. Concretament, en el canal de retorn (de l’usuari a la xarxa) de xarxes d’accés de banda ampla, els usuaris residencials generen grans ràfegues de tràfic amb períodes d’inactivitat freqüents. Una situació similar succeeix en xarxes de comunicacions mòbils per satèl·lit, on una gran població de terminals generen transmissions infreqüents de senyalització, serveis basats en la localització or altres aplicacions de missatgeria. Aquests serveis requereixen el desenvolupament de protocols d’accés múltiple eficients que puguin operar en les condicions descrites anteriorment. Els protocols d´accés aleatori són bons candidats per servir tràfic poc predictiu, amb transmissions infreqüents així com sensibles amb el retard. A més, els protocols d´accés aleatori suporten un gran nombre de terminals compartint el canal de comunicacions i requereixen poca complexitat en el terminals. El protocols d´accés aleatori han estat àmpliament estudiats i desplegats en xarxes terrestres, però les seves prestacions són pobres en el entorn satèl·lital, que està caracteritzat per retards de propagació molt grans. Avui en dia, el seu ús en les xarxes de comunicacions per satèl·lit està principalment limitat a la senyalització d’inici de sessió, transmissió de paquets de control i en alguns casos a la transmissió de petits volums de dades amb unes eficiència d’utilització del canal molt baixa. Aquesta tesi proposa tres noves tècniques d’accés aleatori, bens adaptades per proveir els serveis esmentats anteriorment en un entorn satèl·lital, amb altes prestacions i una complexitat en el terminal d’usuari reduïda. Les noves tècniques d’accés aleatori són Contention Resolution Diversity Slotted Aloha (CRDSA), Asynchronous Contention Resolution Diversity Aloha (ACRDA) i Enhanced Spread Spectrum Aloha (E-SSA), adaptades per un tipus d’accés ranurat, asíncron i d’espectre eixamplat respectivament. Les tres tècniques utilitzen una codificació de canal (FEC) robusta, capaç d’operar en front de interferències elevades, que són típiques en l’accés aleatori, i d’un mecanisme de cancel·lació successiva d’interferència que s’implementa en el receptor sobre els paquets descodificats satisfactòriament. Els nous protocols obtenen un throughput normalitzat superior a 1 bit/s/Hz amb una tassa de pèrdua de paquets inferior a 10-3, el qual representa un factor de millora de 1000 respecte a protocols d’accés aleatori tradicionals com l’ALOHA ranurat. Les prestacions de les noves tècniques d’accés aleatori has estat analitzades per mitjà de simulacions, així com amb nou models analítics desenvolupats en aquesta tesi capaços de caracteritzar el tràfic, la distribució estadística de la potència dels paquets, les prestacions de la codificació de canal (FEC) i el procés de cancel·lació d’interferència successiva.Los últimos años han experimentado un crecimiento de la demanda de servicios interactivos por satélite para el gran consumo, cubriendo servicios fijos i móviles, como el acceso de banda ancha, comunicaciones máquina a máquina (M2M), supervisión, control y adquisición de datos (SCADA), transacciones i aplicaciones criticas de seguridad. Estas redes de comunicaciones se caracterizan por tener una gran población de usuarios compartiendo el ancho de banda en unas condiciones de tráfico muy dinámicas. Concretamente, en el canal de retorno (del usuario a la red) de redes de acceso de banda ancha, los usuarios residenciales generan grandes ráfagas de tráfico con periodos frecuentes de inactividad. Una situación similar ocurre en las redes de comunicaciones móviles por satélite, donde una gran población de terminales generan transmisiones infrecuentes de señalización, servicios basados en la localización u otras aplicaciones me mensajería. Estos servicios requieren el desarrollo de protocolos de acceso múltiple eficientes capaces de operar en las condiciones descritas anteriormente. Los protocolos de acceso aleatorio son buenos candidatos para servir el tráfico poco predictivo, con transmisiones infrecuentes así como sensibles al retardo. Además, los protocolos de acceso soportan un gran número de terminales compartiendo el canal de comunicaciones y requieren poca complejidad en los terminales. Los protocolos de acceso aleatorio han estado ampliamente estudiados i desplegados en las redes terrestres, pero sus prestaciones son pobres en el entorno satelital, que se caracteriza por retardos de comunicaciones muy elevados. Hoy en día, su uso en la redes de comunicaciones por satélite está principalmente limitado a la señalización de inicio de sesión, transmisión de pequeños volumenes de datos con eficiencia de utilización del canal muy baja. Esta tesis propone tres nuevas técnicas de acceso aleatorio bien adaptadas para proveer los servicios mencionados anteriormente en un entorno de comunicaciones por satélite, con altas prestaciones y una complejidad en el terminal de usuario reducida. Las nuevas técnicas de acceso aleatorio son Contention Resolution Diversity Slotted Aloha (CRDSA), Asynchronous Contention Resolution Diversity Aloha (ACRDA) y Enhanced Spread Spectrum Aloha (E-SSA), adaptadas para un tipo de acceso ranurado, asíncrono y de espectro ensanchado respectivamente. Las tres técnicas utilizan una codificación de canal (FEC) robusta, capaz de operar en condiciones de interferencia elevadas, que son típicas en el acceso aleatorio, y de un mecanismo de cancelación sucesiva de interferencias que se implementa en el receptor sobre los paquetes que han sido decodificados satisfactoriamente. Los nuevos protocolos obtienen un throughput normalizado superior a 1 bit/s/Hz con una tasa de pérdida de paquetes inferior a 10-3, lo cual representa un factor de mejora de 1000 respecto a los protocolos de acceso aleatorio tradicionales como el ALOHA ranurado. Las prestaciones de las nuevas técnicas de acceso aleatorio han sido analizadas con simulaciones así como con nuevos modelos analíticos desarrollados en esta tesis, capaces de caracterizar el tráfico, la distribución estadística de la potencia de los paquetes, las prestaciones de la codificación de canal (FEC) y el proceso de cancelación sucesiva de interferencias.Over the past years there has been a fast growing demand for low-cost interactive satellite terminals supporting both fixed and mobile services, such as consumer broadband access, machine-to-machine communications (M2M), supervisory control and data acquisition (SCADA), transaction and safety of life applications. These networks, are generally characterized by a large population of terminals sharing the available resources under very dynamic traffic conditions. In particular, in the return link (user to network) of commercial satellite broadband access networks, residential users are likely to generate a large amount of low duty cycle bursty traffic with extended inactivity periods. A similar situation occurs in satellite mobile networks whereby a large number of terminals typically generate infrequent packets for signaling transmission as well for position reporting or other messaging applications. These services call for the development of efficient multiple access protocols able to cope with the above operating conditions. Random Access (RA) techniques are by nature, good candidates for the less predictive, low duty cycle as well as time sensitive return link traffic. Besides, RA techniques are capable of supporting large population of terminals sharing the same capacity and require low terminal complexity. RA schemes have been widely studied and deployed in terrestrial networks, but do not perform well in the satellite environment, which is characterized by very long propagation delays. Today, their use in satellite networks is mainly limited to initial network login, the transmission of control packets, and in some cases, for the transmission of very small volumes of data with very low channel utilization. This thesis proposes three novel RA schemes well suited for the provision of the above-mentioned services over a satellite environment with high performance and low terminal complexity. The new RA schemes are Contention Resolution Diversity Slotted Aloha (CRDSA), Asynchronous Contention Resolution Diversity Aloha (ACRDA) and Enhanced Spread Spectrum Aloha (E-SSA), suited for slotted, unslotted and spread spectrum-based systems respectively. They all use strong Forward Error Correction (FEC) codes, able to cope with heavy co-channel interference typically present in RA, and successive interference cancellation implemented over the successfully decoded packets. The new schemes achieve a normalized throughput above 1 bit/s/Hz for a packet loss ratio below 10-3, which represents a 1000-fold increase compared to Slotted ALOHA. The performance of the proposed RA schemes has been analyzed by means of detailed simulations as well as novel analytical frameworks that characterize traffic and packets power statistical distributions, the performance of the FEC coding as well as the iterative interference cancellation processing at the receiver

Real-time scheduling for media processing using conditionally guaranteed budgets

In dit proefschrift behandelen we een planningsprobleem dat haar oorsprong vindt in het kosteneffectief verwerken van verschillende media door software in consumentenapparaten, zoals digitale televisies. De laatste jaren zijn er trends gaande van analoge naar digitale systemen, en van verwerking van digitale signalen door speci??eke, toepassingsgerichte hardware naar verwerking door software. Voor de verwerking van digitale media door software wordt gebruik gemaakt van krachtige programmeerbare processoren. Om te kunnen wedijveren met bestaande oplossingen is het van belang dat deze programeerbare hardware zeer kosteneffectief wordt gebruikt. Daarnaast dienen de bestaande eigenschappen van deze consumenten apparaten, zoals robuustheid, stabiliteit, en voorspelbaarheid, behouden te blijven als er software wordt gebruikt. Verder geldt dat er gelijktijdig meerdere media stromen door een consumenten apparaat verwerkt moeten kunnen worden. Deze uitdaging is binnen de onderzoekslaboratoria van Philips aangegaan in het zogenoemde Video-Quality-of-Service programma, en het werk dat in dit proefschrift beschreven wordt is binnen dat programma ontstaan. De binnen dat programma gekozen aanpak is gebaseerd op schaalbare algoritmen voor de verwerking van media, budgetten voor die algoritmen, en software dat de instelling van die algoritmen en de grootte van de budgetten aanpast tijdens de verwerking van de media. Ten behoeve van het kosteneffectief gebruik van de programmeerbare processoren zijn de budgetten krap bemeten. Dit proefschrift geeft een uitvoerige beschrijving van die aanpak, en van een model van een apparaat dat de haalbaarheid van die aanpak aantoont. Vervolgens laten we zien dat die aanpak leidt tot een probleem wanneer er gelijktijdig meerdere stromen worden verwerkt die verschillende relatieve relevanties hebben voor de gebruiker van het apparaat. Om dit probleem op te lossen stellen we het nieuwe concept van voorwaardelijk gegarandeerde budgetten voor, en beschrijven we hoe dat concept kan worden gerealiseerd. De technieken voor het analyseren van het planningprobleem voor budgetten zijn gebaseerd op bestaande technieken voor slechtste-gevals-analyse voor periodieke real-time taken. We breiden die bestaande technieken uit met technieken voor beste-gevals-analyse zodat we apparaten die gebruik maken van dit nieuwe type budget kunnen analyseren

Linux-Box: DVB and VoD streaming over local area networks

Aquest treball tracta sobre un projecte comú anomenat Linux-Box portat a terme per diferents persones al departament de Telecomunicacions (IET) de la Universitat de Pisa. Linux-Box és un sistema dotat amb targetes TDT (DVB-T) i de televisió per satèl·lit (DVB-S) que permet transmetre aquests senyals fins a un àmbit domèstic. Més endavant podria ser utilitzat en àmbits privats com les cases de clients o en institucions públiques com escoles, universitats, biblioteques i també seria possible en àmbits empresarials. El projecte està dividit en 4 apartats: 1. Ubuntu 6.06 LTS. Explica perquè s’utilitza Ubuntu en el projecte. A més també s’explica de forma breu que és Linux i les distribucions més utilitzades. 2. Multimedia Network Protocols: s’expliquen els diferents protocols desde la capa de xarxa fins la capa d’aplicació que s’utilitzen en el projecte Linux-Box. Aquests protocols són utilitzats tant en streaming, com en anunciació, unicast/multicast, encapsulat de vídeo i codecs. Els diversos temes tractats aquí es fan amb el propòsit de comparar i no només com a recerca teòrica. A la fi es veuen els programes utilitzats en el projecte per analitzar el tràfic de la xarxa. 3. Linux-Box: s’explica el funcionament i els objectius globals del projecte. Es dedica un sub-apartat a “VideoLan - VLC” part important a nivell de sofware. Més endavant es parla de les característiques de la Linux-Box de forma acurada: streaming de VoD i senyals de TV i s’analitzen els problemes coneguts i les seves solucions proposades. A la fi s’enumeren els llenguatges de programació utilitzats al projecte i en quina part s’utilitzen. Observarem que és una aplicació on diversos llenguatges de programació estan contínuament solapats. 4. Developed Part: es posa en pràctica la teoria estudiada a la resta del treball. Està dividida en 4 seccions: Desenvolupar una aplicació en codi C per convertir la llista de Canals (tant terrestre com de satèl·lit) en format XML. Una secció dedicada al streaming de Canals de TV a la pàgina web principal. Un anàlisis profund dels paquets creats per la Linux-Box i la seva activitat a la xarxa. Finalment s’analitzen els diferents scripts i les seves configuracions. Alguns són útils per a un futur desenvolupament i d’altres s’utilitzen en seccions prèvies. 5. Conclusions: conté les conclusions i línies futures. El projecte compta amb diverses opcions que encara poden ser implementades i estudiades. Aquí exposem les nostres interpretacions i possibles línies futures d’estudi

Technology Directions for the 21st Century

New technologies will unleash the huge capacity of fiber-optic cable to meet growing demands for bandwidth. Companies will continue to replace private networks with public network bandwidth-on-demand. Although asynchronous transfer mode (ATM) is the transmission technology favored by many, its penetration will be slower than anticipated. Hybrid networks - e.g., a mix of ATM, frame relay, and fast Ethernet - may predominate, both as interim and long-term solutions, based on factors such as availability, interoperability, and cost. Telecommunications equipment and services prices will decrease further due to increased supply and more competition. Explosive Internet growth will continue, requiring additional backbone transmission capacity and enhanced protocols, but it is not clear who will fund the upgrade. Within ten years, space-based constellations of satellites in Low Earth orbit (LEO) will serve mobile users employing small, low-power terminals. 'Little LEO's' will provide packet transmission services and geo-position determination. 'Big LEO's' will function as global cellular telephone networks, with some planning to offer video and interactive multimedia services. Geosynchronous satellites also are proposed for mobile voice grade links and high-bandwidth services. NASA may benefit from resulting cost reductions in components, space hardware, launch services, and telecommunications services

Telecommunications Networks

This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing

Integrating LEO Satellite Constellations into Internet Backbone

Low Earth Orbit (LEO) satellite constellations have been used for ubiquitous and flexible Internet access services. However, a number of problems related to the integration of terrestrial with satellite hosts should be resolved for the effective exploitation of LEO constellations. LEO constellations are different from terrestrial Internet because of its special properties, which result in a lot of problems. A key issue is how to route Internet packets to the LEO constellation. In the thesis (1) the background of LEO constellations was introduced; (2) the obstacles of routing between the satellites and Internet were outlined; (3) The particular problem, which must be solved, is the routing burst stream traffic in LEO satellite constellations. Two novel routing algorithmsCControl Route Transmission (CRT) and CRT with bandwidth allocation (BCRT)Cwere utilized to address the bursts routing problem. CRT is an adaptive protocol which is able to minimize the congestion in the constellations. BCRT is a CRT extension which is allowed to class the traffic (e.g. video) with different QoS requirements and guarantees. Both of CRT and BCRT work in time epochs. Routes are computed on the basis of a directed weighted graph representing the global traffic traveling in the constellations. Both CRT and BCRT were evaluated via simulation and compared with other proposals in the literatures. The results showed that CRT is a simple algorithm, but the strategy produced by CRT could avoid the congestion and enhance the global resource usage in different traffic conditions. Moreover, the explicit reservation and reroute of BCRT greatly improve the performance of CRT. In particular, the dropping rate of BCRT is very low and the average delivery time is comparable with other proposals in the literatures.Low Earth Orbit (LEO) satellite constellations have been used for ubiquitous and flexible Internet access services. However, a number of problems related to the integration of terrestrial with satellite hosts should be resolved for the effective exploitation of LEO constellations. LEO constellations are different from terrestrial Internet because of its special properties, which result in a lot of problems. A key issue is how to route Internet packets to the LEO constellation. In the thesis (1) the background of LEO constellations was introduced; (2) the obstacles of routing between the satellites and Internet were outlined; (3) The particular problem, which must be solved, is the routing burst stream traffic in LEO satellite constellations. Two novel routing algorithmsCControl Route Transmission (CRT) and CRT with bandwidth allocation (BCRT)Cwere utilized to address the bursts routing problem. CRT is an adaptive protocol which is able to minimize the congestion in the constellations. BCRT is a CRT extension which is allowed to class the traffic (e.g. video) with different QoS requirements and guarantees. Both of CRT and BCRT work in time epochs. Routes are computed on the basis of a directed weighted graph representing the global traffic traveling in the constellations. Both CRT and BCRT were evaluated via simulation and compared with other proposals in the literatures. The results showed that CRT is a simple algorithm, but the strategy produced by CRT could avoid the congestion and enhance the global resource usage in different traffic conditions. Moreover, the explicit reservation and reroute of BCRT greatly improve the performance of CRT. In particular, the dropping rate of BCRT is very low and the average delivery time is comparable with other proposals in the literatures

Optimização de recursos para difusão em redes de próxima geração

Doutoramento em ElectrotecniaEsta tese aborda o problema de optimização de recursos de rede, na entrega de Serviços de Comunicação em Grupo, em Redes de Próxima Geração que suportem tecnologias de difusão. De acordo com esta problemática, são feitas propostas que levam em atenção a evolução espectável das redes 3G em Redes Heterogéneas de Próxima Geração que incluam tecnologias de difusão tais como o DVB. A optimização de recursos em Comunicações em Grupo é apresentada como um desafio vertical que deve cruzar diversas camadas. As optimizações aqui propostas cobrem tanto a interface entre Aplicação e a Plataforma de Serviços para a disponibilização de serviços de comunicação em grupo, como as abstracções e mapeamentos feitos na interface entre a Rede Central e a Rede de Acesso Rádio. As optimizações propostas nesta tese, assumem que o caminho evolutivo na direcção de uma Rede de Próxima Geração é feito através do IP. Em primeiro lugar são endereçadas as optimizações entre a Aplicação e a Plataforma de Serviços que já podem ser integradas nas redes 3G existentes. Estas optimizações podem potenciar o desenvolvimento de novas e inovadoras aplicações, que através do uso de mecanismos de distribuição em difusão podem fazer um uso mais eficiente dos recursos de rede. De seguida são apresentadas optimizações ao nível da interface entre a Rede Central e a Rede de Acesso Rádio que abordam a heterogeneidade das redes futuras assim como a necessidade de suportar tecnologias de difusão. É ainda considerada a possibilidade de aumentar a qualidade de serviço de serviços de difusão através do mapeamento do IP multicast em portadoras unidireccionais. Por forma a validar todas estas optimizações, vários protótipos foram desenvolvidos com base num router avançado para redes de acesso de próxima geração. As funcionalidades e arquitectura de software desse router são também aqui apresentadas.This thesis addresses the problem of optimizing network resource usage, for the delivery of Group Services, in Next Generation Networks featuring broadcast technologies. In this scope, proposals are made according to the expected evolution of 3G networks into Next Generation Heterogeneous Networks that include broadcast technologies such as DVB. Group Communication resource optimization is considered a vertical challenge that must cross several layers. The optimizations here proposed cover both Application to Service Platform interfaces for group communication services, and Core Network to Radio Access Network interface abstractions and mappings. The proposed optimizations are also presented taking into consideration network evolution path towards an All-IP based Next Generation Network. First it is addressed the Application to Service Platform optimization, which can already be deployed over 3G networks. This optimization could potentiate the development of new and innovative applications that through the use of broadcast/multicast service delivery mechanisms could be more efficient network wise. Next proposals are made on the Core Network to Radio Access Network interfaces that address the heterogeneity of future networks and consider the need to support broadcast networks. It is also considered the possibility to increase the Quality of Service of broadcast/multicast services based on the dynamic mapping of IP multicast into unicast radio bearers. In order to validate these optimizations, several prototypes were built based on an advanced access router for next generation networks. Such access router functionalities and software architecture are also presented here