Support of resource-aware vertical handovers in WLAN hotspots

Endgeräte wie Smartphones oder Tablets bieten häufig eine Vielfalt drahtloser Zugänge zum Internet an. Üblicherweise schließt dies die 802.11 WLANs und auch Technologien drahtloser Weitverkehrsnetze (WWANs) aus dem Bereich LTE oder WiMAX ein. Aufgrund dieser Optionen haben sich die Endanwender daran gewöhnt, überall und zu jeder Zeit auf ihre Internetdienste zuzugreifen. Damit hat auch der Datenverkehr pro Anwender zugenommen, was eine Herausforderung insbesondere für die Betreiber von WWANs ist. Soweit verfügbar, favorisieren Endanwender heutzutage eher einen drahtlosen Zugang zum Internet über WLANs als über WWANs. Des Weiteren haben die 3GPP-Standardisierungsgremien Ansätze erarbeitet, die zusätzlich Verkehr aus WWANs in Netze mit geringerer Abdeckung wie WLAN- oder Femto-Zellen abgeben. Solche Ansätze werden auch als "Traffic Offloading" bezeichnet und haben das Ziel, die WWANs zu entlasten. Dabei werden jedoch eher einfache Strategien verfolgt, die auf der Nutzung zusätzlicher Kapazitäten heterogener Netze beruhen und dann angewendet werden, wenn ein alternatives Zugangsnetz für ein Endgerät verfügbar ist. Im Rahmen dieser Arbeit zeigen wir Gewinne auf, die entstehen, wenn man die Auswahl der Endgeräte für ein WLAN-Netz stattdessen auf Basis der von ihnen belegten Ressourcen durchführt. In diesem Kontext schlagen wir vor, Geräte mit stark negativem Einfluss auf die WLAN-Kapazität wieder zurück in das WWAN zu reichen, was wir als "Onloading" bezeichnen. Ein solches "Onloading" zieht Herausforderungen in unterschiedlichen Richtungen mit sich. Die fortschreitende Miniaturisierung hat in den letzten Jahren zu dem Trend geführt, die Anzahl der Netzwerkkarten (NICs) in Endgeräten zu reduzieren. Wir bezeichnen eine NIC als multimodal, wenn sie mehrere Funktechnologien unterstützt, aber zu einem bestimmten Zeitpunkt immer nur eine davon genutzt werden kann. Deswegen stellt für eine multimodale NIC das "Onloading" während einer laufenden Verbindung eine Herausforderung dar. Wir schlagen einen Ansatz vor, der vorbereitende Mechanismen für ein "Onloading" als auch eine laufende Verbindung im WLAN über eine solche NIC ermöglicht. Des Weiteren ist es wichtig, in einem WLAN Hotspot zu entscheiden, welche Geräte einen negativen Einfluss auf die Kapazität des Netzes haben. Dafür haben wir eine Metrik entwickelt, die eine Entscheidungsgrundlage für das Onloading bildet. Diese Metrik basiert rein auf einer Beobachtung des Netzes und seiner Geräte, ermöglicht jedoch keine Entscheidung für sich neu assoziierende Geräte im WLAN. Erschwerend kommt hinzu, dass viele Eigenschaften der NICs durch herstellerabhängige Implementierungen geprägt werden. Solche Algorithmen bieten eine zusätzliche Herausforderung, da ihre internen Abläufe üblicherweise unbekannt sind. Ein bekanntes Beispiel für solche Algorithmen stellt die Anpassung der WLAN-Link-Datenraten dar. Diese Algorithmen wählen die jeweiligen Modulations- und Kodierungsschemata (MCSs) für die drahtlosen Übertragungen aus. Robuste MCSs resultieren dabei in geringere Link-Datenraten und haben somit einen starken Einfluss auf die Kapazität einer WLAN-Zelle. Aus diesem Grund fokussieren wir uns auf eine Abschätzung der Datenratenwahl eines Endgerätes. Damit lassen sich im Vorfeld Aussagen treffen, ob ein Gerät starken Einfluss auf die WLAN-Kapazität haben wird, so dass es für ein "Onloading" in Frage kommt.End-user devices such as smart phones and tablets have become very popular as they offer a variety of wireless Internet accesses ranging from the WLAN standards to WWAN technologies such as LTE or even WiMAX. Due to these different wireless access options and new emerging applications—e.g., from the areas of video streaming, social networks, as well as Internet clouds—people are increasingly connecting to the Internet with their de- vices while being on the move. In line with this, the number of devices as well as the traffic demand of end users have been reported to increase rapidly over the last years which imposes a strong challenge especially for the operators of WWANs. Thereby, end users frequently tend to use settings that favor a connectivity to the Internet whenever possible rather over WLAN than over WWAN access. Further, the cellular standardization bodies of the 3GPP envision solutions to hand over on-going wireless sessions from cellular to other small cell accesses such as WLANs or femto cells. This is also known as traffic offloading essentially freeing capacity in terms of users with a certain service in the cellular accesses. Nevertheless this offloading follows a rather simple strategy to utilize additional capacity of heterogeneous accesses such as WLANs whenever being available for a given device. This thesis shows that stronger gains can be expected if the selection of devices to be served in WLANs is conducted in a resource-aware fashion including an evaluation of the WLAN traffic in terms of the channel occupation time and MAC overhead as result of contention, interference, and fluctuating channels. In this context, this thesis envisions to onload unfavorable devices negatively affecting the WLAN capacity back to WWAN accesses. A support of such an onloading imposes challenges in different dimensions. From the hardware design of devices, there is a strong trend to limit the number of separate network interface cards (NICs) due to space and cost issues. We refer to a multi-mode NIC if it covers multiple technologies, while at a given time only access to one technology is possible. Thus, smoothly onloading a device with such a NIC is by far not trivial. We present an approach that conducts handover preparation mechanisms, while also allowing a continuous WLAN communication over a multi-mode NIC. Further, it is by far not trivial to judge which subset of associated devices is negatively affecting the capacity of a WLAN hotspot. Thus, a careful evaluation of devices regarding a selection for an onloading back to WWAN accesses imposes a challenge yet. In this direction, we present a performance metric that identifies devices degrading the WLAN capacity. While our performance metric tackles a reactive selection, it falls short to support a predictive evaluation, e.g., of devices which just joined the WLAN cell. Even worse, proprietary algorithms inside a WLAN stack impose a severe challenge as their internal routines are usually not conveyed via typical management interfaces. A well-known example for this category of algorithms are the link data rate adaptation schemes, with which WLAN devices adjust the modulation and coding scheme (MCS) for their transmissions. As MCSs resulting in low link data rates may specifically degrade the capacity of a WLAN cell, we focus on an estimation regarding the data rate selection of a device as a third contribution of this thesis. This estimation enables to select devices that will likely degrade the capacity of the WLAN hotspot for an onloading in advance

Standardization of network interfaces : a framework for collaborative development and go-to-market strategy

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2006."June 2006."Includes bibliographical references.Over the last decade technological innovation in computers and communications industries has resulted in higher penetration of technology intensive products in businesses and homes. In communications industry, the true value of converged networks will be exploited only if the products and services provided end-to-end quality, reliability and consistency of features and functionalities that are offered. However, for this to happen, the products, systems and networks need to be interoperable. Interoperability can be accomplished most effectively and efficiently by use of common standards; but at the same time use of common standards potentially and arguably leads to commoditization of products, and constrains ability of product differentiation. Processes for setting standards, are not only messy but are prolonged, and quite often lead to battles for platform leadership. As incumbent telecommunications service providers transition from the public switched telephone networks to the IP-based data networks, customer expectations are high, challenges are many and failures are costly.(cont.) Verizon Interoperability Forum has taken on this challenge by attempting to develop standards for interfaces for network elements that are used on Verizon's own network. It is proposed that network interfaces' standards exhibit characteristics of network effects and possess a great potential for becoming a de facto standard.by Uday Hardikar.S.M

Adaptive scheduling in cellular access, wireless mesh and IP networks

Networking scenarios in the future will be complex and will include fixed networks and hybrid Fourth Generation (4G) networks, consisting of both infrastructure-based and infrastructureless, wireless parts. In such scenarios, adaptive provisioning and management of network resources becomes of critical importance. Adaptive mechanisms are desirable since they enable a self-configurable network that is able to adjust itself to varying traffic and channel conditions. The operation of adaptive mechanisms is heavily based on measurements. The aim of this thesis is to investigate how measurement based, adaptive packet scheduling algorithms can be utilized in different networking environments. The first part of this thesis is a proposal for a new delay-based scheduling algorithm, known as Delay-Bounded Hybrid Proportional Delay (DBHPD), for delay adaptive provisioning in DiffServ-based fixed IP networks. This DBHPD algorithm is thoroughly evaluated by ns2-simulations and measurements in a FreeBSD prototype router network. It is shown that DBHPD results in considerably more controllable differentiation than basic static bandwidth sharing algorithms. The prototype router measurements also prove that a DBHPD algorithm can be easily implemented in practice, causing less processing overheads than a well known CBQ algorithm. The second part of this thesis discusses specific scheduling requirements set by hybrid 4G networking scenarios. Firstly, methods for joint scheduling and transmit beamforming in 3.9G or 4G networks are described and quantitatively analyzed using statistical methods. The analysis reveals that the combined gain of channel-adaptive scheduling and transmit beamforming is substantial and that an On-off strategy can achieve the performance of an ideal Max SNR strategy if the feedback threshold is optimized. Finally, a novel cross-layer energy-adaptive scheduling and queue management framework EAED (Energy Aware Early Detection), for preserving delay bounds and minimizing energy consumption in WLAN mesh networks, is proposed and evaluated with simulations. The simulations show that our scheme can save considerable amounts of transmission energy without violating application level QoS requirements when traffic load and distances are reasonable

Estrategias de configuración de redes WLAN IEEE 802.11e EDCA

Las redes inalámbricas de área local (WLANs) se han convertido en una solución muy común para proporcionar acceso a Internet. El principal mecanismo usado a nivel MAC (Medium Access Control) para las WLANs es el definido por el estándar IEEE 802.11. Recientemente, el grupo de trabajo (Working Group) 802.11 ha aprobado un nuevo estándar, denominado 802.11e, que extiende dicho mecanismo para suministrar calidad de servicio (QoS). Este nuevo estándar se basa en una serie de parámetros a configurar, tema aún pendiente de ser resuelto pues si bien se proporcionan unos valores recomendados para dichos parámetros, estos valores son estáticos por lo que su idoneidad no está garantizada. La presente tesis aborda el diseño de estrategias de configuración que optimicen el uso del mecanismo EDCA del estándar 802.11e. A tal efecto, se distinguen dos escenarios WLAN bien diferentes, cada uno definiendo una diferente estrategia de configuración para los mencionados parámetros: En el primer escenario, denominado WLAN abierta, se supone un entorno abierto como, por ejemplo, un hot-spot. En dicho escenario no se puede confiar en la caracterización del tráfico y los requisitos de servicio que pudiesen proporcionar los usuarios, dado que estos bien pueden declarar unos valores diferentes a los reales para obtener más recursos de la red. Dichos usuarios pueden incluso saturar su acceso inalámbrico (esto es, tener siempre un paquete en proceso de ser transmitido)para obtener recursos adicionales. Para este escenario se propone una configuración que garantice un rendimiento óptimo incluso en presencia de posibles usuarios saturando sus interfaces. Dada la naturaleza abierta de este escenario, adicionalmente se desarrolla un mecanismo que detecta comportamientos no ajustados a una determinada configuración. En el segundo escenario, denominado WLAN cerrada, los usuarios son dignos de confianza. Un ejemplo de dicho escenario puede ser un entorno de oficinas, donde sólo los empleados pueden conectarse a la red. En este caso, tanto la caracterización declarada del tráfico, así como los requisitos de servicio, pueden ser utilizados con objeto de calcular la configuración óptima que proporciona el mejor rendimiento. Nótese que, en este escenario, dado que se dispone de más información, sí que es posible escoger la configuración que mejor atiende los requisitos y características de las fuentes de tráfico. Las principales contribuciones de la presente tesis se resumen a continuación: para el escenario de la WLAN abierta, en primer lugar se analiza el rendimiento de una red saturada,a partir del cual se propone un algoritmo de configuración que optimiza el rendimiento global de la red, tanto en el modo básico como en el modo multirate. También se propone un algoritmo para detectar usuarios maliciosos en la red. Para el caso de la WLAN cerrada, se presentan algoritmos para caracterizar el comportamiento del retardo (valor medio, desviación típica y función de distribución) de la red en condiciones de no saturación. Con base en estos resultados, se presenta un algoritmo que calcula la configuración óptima para un caso de uso de Voz sobre IP. Por último, se describen resultados experimentales centrados también en este caso de uso. ____________________________________________Nowadays Wireless LANs (WLANs) have become a very popular technology for Internet access. The Medium Access Control algorithm used by today’s WLANs is the one defined by the IEEE 802.11 standard. Recently, the IEEE 802 Working Group has approved a new standard called 802.11e that extends the basic 802.11 algorithm with Quality of Service capabilities. This new standard is based on a number of open parameters the configuration of which is yet an unsolved research issue. Although the standard includes some recommendations for the parameters configuration, these recommendations are statically set and do no guarantee optimized performance. This thesis takes up the issue of designing optimal configuration guidelines for 802.11e EDCA. To this aim, in this thesis two different WLAN scenarios are considered, each scenario driving to a different configuration strategy for the setting of the parameters: In the first scenario, which we call open WLAN, an open scenario like e.g. a hot-spot is assumed. In such scenario, the network cannot rely on the traffic characterization and requirements declared by the users, as users could potentially declare different values than the real ones thereby gaining additional resources from the network. Such users could even saturate their wireless access (i.e. by having always packets ready for transmission) in order to obtain extra resources. For this scenario, we propose an optimal configuration that guarantees optimal operation even in the presence of users saturating their channel. Given the untrusted nature of this scenario, mechanisms that detect malicious behaviours are devised. In the second scenario, the closed WLAN, users’behaviour can be trusted. An example of such a scenario could be an office setting in which only trusted employees are allowed to connect to the network. In this case, the source behaviour declared by the users, as well as their Quality of Service requirements, can be used in order to compute an optimal configuration that optimizes the behaviour given this information. Note that with this scenario, given that more information is known, it is possible to choose a parameter configuration that better meets the requirements and characteristics of the sources. The main contributions of this thesis are summarized as follows. For the open WLAN scenario, we first analyze the performance of a saturated WLAN and then, based on this analysis, we propose configuration algorithms that optimize the overall network performance both in the basic and multirate modes.We also propose an algorithm to detect malicious users in this scenario. For the closed WLAN scenario, we present novel algorithms to compute the delay performance (average delay, typical deviation and delay distribution) of a nonsaturated WLAN. Next, based on these analysis, we present an algorithm for computing the optimal configuration for the use case of VoIP traffic. Finally, we present some experimental results for this use case

Classification and Comparative Study of Routing Techniques in Adhoc Wireless Networks

Wireless systems have been in use since 1980s. We have seen their evolutions to first, second and third generation's wireless systems. Wireless systems operate with the aid of a centralized supporting structure such as an access point. These access points assist the wireless users to keep connected with the wireless system, when they roam from one place to the other. The presence of a fixed supporting structure limits the adaptability of wireless systems. In other words, the technology cannot work effectively in places where there is no fixed infrastructure. Future generation wireless systems will require easy and quick deployment of wireless networks. This quick network deployment is not possible with the Infrastructured wireless systems. Recent advancements such as Bluetooth introduced a new type of wireless systems known as ad-hoc networks. Ad-hoc networks or "short live" networks operate in the absence of fixed infrastructure. They offer quick and easy network deployment in situations where it is not possible otherwise. Ad-hoc is a Latin word, which means "for this or for this only." Mobile ad-hoc network is an autonomous system of mobile nodes connected by wireless links; each node operates as an end system and a router for all other nodes in the network. Nodes in ad-hoc network are free to move and organize themselves in an arbitrary fashion. Each user is free to roam about while communication with others. The path between each pair of the users may have multiple links and the radio between them can be heterogeneous. This allows an association of various links to be a part of the same network. A mobile ad-hoc network is a collection of mobile nodes forming an ad-hoc network without the assistance of any centralized structures. These networks introduced a new art of network establishment and can be well suited for an environment where either the infrastructure is lost or where deploy an infrastructure is not very cost effective. The popular IEEE 802.11 "WI-FI" protocol is capable of providing ad-hoc network facilities at low level, when no access point is available. However in this case, the nodes are limited to send and receive information but do not route anything across the network. Ad-hoc networks can operate in a standalone fashion or could possibly be connected to a larger network such as the Internet. An ad-hoc network has certain characteristics, which imposes new demands on the routing protocol. The most important characteristic is the dynamic topology, which is a consequence of node mobility. Nodes can change position quite frequently; the nodes in an ad-hoc network can consist of laptops and personal digital assistants and are often very limited in resources such as CPU power, storage capacity, battery power and bandwidth. This means that the routing protocol should try to minimize control traffic, such as periodic update messages. The Internet Engineering Task Force currently has a working group named Mobile Ad-hoc Networks that is working on routing specifications for ad-hoc networks. This M.Phill thesis evaluates some of the protocols put forth by the working group. This evaluation is done by means of simulation using Network simulator 2 from Berkeley. This work aims at classification of the existing routing protocols of adhoc wireless networks using some definite parameters. After classification of routing protocols of adhoc wireless network, their comparative study was undertaken in order to yield category wise distribution. Furthermore performance evaluation of these protocols was carried out by employing different parameters like fading models, mobility models, traffic patterns etc using the network simulator NS-2 Hence I explore and evaluate different methods for validation of ad hoc routing protocols which are used to set up forwarding paths in spontaneous networks of mobile/Adhoc devices to accomplish the above mentioned comparative study and classification

Scenario analysis of the mobile voice market

Mobiiliverkkojen kehitys yhdessä Internetpalveluiden kasvavan kysynnän kanssa on johtamassa mobiiliteollisuuden sekä Internet-maailman yhtymiseen. Yksi eniten keskustelua herättäneistä Internet palveluista on VoIP, joka on jo nyt kehittynyt tärkeäksi kommunikaatiotavaksi. Myös mobiiliteollisuus on jo saanut kokea muutamia alustavia mobiili-VoIP toteutuksia. (Nokian puhelinten SIP applikaatio, Fring, Three:n ja Skypen yhteistyö). Lisäksi myös muiden mobiili-Internet palveluiden kehitys tulee vauhdittamaan mobiili VoIPin nousua. Mobiilioperaattorit ovat huomanneet mobiili-VoIPin tuoman uhkan ja pelkäävät sen tuomia vaikutuksia puhepalveluidensa tuottoon. Toisaalta, jotkin mobiilioperaattorit ja Internetin palveluntarjoajat saattavat nähdä tämän kehityksen mahdollisuutena konvergoitua myös palveluliiketoimintaan. Tämä diplomityö käsittelee langattomien pakettikytkentäisten tietoverkkojen soveltuvuutta VoIP-tekniikan käyttöön. Myös puhemarkkinoiden markkinadynamiikkaa on tutkittu, jotta VoIP-markkinoiden muuttumisen syitä voitaisiin paremmin ymmärtää. Näiden teknisten ja kaupallisten tutkimusten pohjalta on suoritettu kvalitatiivinen Viiden Voiman analyysi, jonka avulla mobiilimarkkinaan vaikuttavia epävarmuuksia on pyritty identifioimaan. Näistä epävarmuuksista on nostettu esiin joukko tärkeitä muuttujia, jotka parhaiten kuvaavat mobiilimarkkinan muutosta. Lopuksi joitakin teollisuuden asiantuntijoita haastateltiin ja näiden haastatteluiden avulla määritettiin kaksi tärkeintä muuttujaa (markkinarakenne mobiiiliviestinnässä sekä yhteystapa multiradio-verkoissa), jotka yhdessä muodostavat skenaarioita tulevaisuuden mobiilipuhe-markkinasta. Tämän työn tuloksena esitellään neljä tulevaisuuden skenaariota, jotka määrittelevät tulevaisuuden puhemarkkinan. Työn lopullisena päätelmänä on, että mobiiliteollisuus on horisontalisoitumisen partaalla. Mobiili-VoIPlla on suora vaikutus mobiilioperaattoreiden puhepalveluiden tuottavuuteen, mikä erityisesti korostaa VoIPn vaikutusta markkinarakenteeseen. Lisäksi mobiili-VoIPn vaikutus yhdessä lukuisien muiden mobiilipalveluiden kanssa tulee olemaan vielä aiempaakin huomattavampi. Tässä kehityksessä vaihtoehtoiset langattomat tekniikat nähdään tärkeimpinä disruption lähteitä. Myös mobiiliverkkojen sääntelyn todetaan olevan kehitystä jäljessä ja täten jokainen muutos sääntelyssä tulee aiheuttamaan muutoksia kehittyvässä mobiili-VoIP markkinassa.The development of mobile networks together with the growing popularity of Internet services is currently leading the mobile industry to converge with the Internet world. One of the most widely discussed Internet services is VoIP that has already become an important means of communication in the Internet. However, also the mobile industry has experienced some tentative launches of VoIP services (Nokia phones with SIP application, Fring, Three and Skype collaboration). In addition, the development of other mobile Internet services will only speed up the emergence of mobile VoIP. Mobile operators have recognized the threat of mobile VoIP and the consequences it may have on their voice revenue. On the other hand, some of the mobile operators may see the development as an opportunity to converge with the services industry. This thesis consists of studies on the mobile packet switched networks and their applicability to be used with VoIP technology. Market dynamics of the VoIP offerings are studied to better understand the business dynamics of mobile VoIP services. The framework of Five Forces is used to combine the industry uncertainties from the previous technical and business studies. A set of important variables is then obtained from these uncertainties to describe the evolution of mobile voice market. A group of industry experts were interviewed in order to define the two most important variables (mobile market structure and access mode in multi-radio networks), which together structure the dimensions of the scenarios on mobile voice market. This thesis introduces four industry scenarios that define the future market of mobile voice. The main outcome of this thesis is that the mobile industry is found to be on a verge of horizontalization. Mobile VoIP has a direct effect on the mobile operators' voice revenue, which especially emphasizes its effect on the market structural change. Besides, mobile VoIP has also synergies with all the diverged mobile services and together they will have an impact on the market structure if they break in to the mobile industry. In this evolution the alternative wireless technologies are seen as the main source of disruption. Also the regulation of mobile networks and services is found lagging the evolution and thus any act by the regulator will cause turbulence among the rising mobile VoIP market