TCP Performance in Heterogeneous Wireless Networks

The TCP protocol is used by most Internet applications today, including the recent mobile wireless terminals that use TCP for their World-Wide Web, E-mail and other traffic. The recent wireless network technologies, such as GPRS, are known to cause delay spikes in packet transfer. This causes unnecessary TCP retransmission timeouts. This dissertation proposes a mechanism, Forward RTO-Recovery (F-RTO) for detecting the unnecessary TCP retransmission timeouts and thus allow TCP to take appropriate follow-up actions. We analyze a Linux F-RTO implementation in various network scenarios and investigate different alternatives to the basic algorithm. The second part of this dissertation is focused on quickly adapting the TCP's transmission rate when the underlying link characteristics change suddenly. This can happen, for example, due to vertical hand-offs between GPRS and WLAN wireless technologies. We investigate the Quick-Start algorithm that, in collaboration with the network routers, aims to quickly probe the available bandwidth on a network path, and allow TCP's congestion control algorithms to use that information. By extensive simulations we study the different router algorithms and parameters for Quick-Start, and discuss the challenges Quick-Start faces in the current Internet. We also study the performance of Quick-Start when applied to vertical hand-offs between different wireless link technologies.Suurin osa Internet-sovelluksista käyttää TCP-protokollaa turvatakseen luotettavan tiedonvaihdon. Tällaisia sovelluksia ovat esimerkiksi WWW, sähköposti, ja monet pikaviestiohjelmat. TCP-protokollan pääpiirteet on suunniteltu 1970- ja 1980-luvulla, jolloin päätelaitteita ja sovelluksia oli huomattavasti nykyistä vähemmän ja yhteydet pohjautuivat kiinteiden kommunikaatiolinkkien käyttöön. Langattomien päätelaitteiden yleistyessä on huomattu, että TCP-protokollan suorituskyky ei aina ole hyväksyttävällä tasolla, koska monet sen piirteistä on alunperin suunniteltu erilaisessa käyttöympäristössä. Väitöstyö perehtyy langattoman linkin aiheuttamien vaikeasti ennustettavien viiveiden vaikutukseen TCP:n suorituskyvylle. Tällainen käyttäytyminen on ominaista esimerkiksi nykyisin laajalti matkapuhelimissa käytetylle GPRS-teknologialle. Yllättävät viiveet datansiirrossa aiheuttavat TCP:n uudelleenlähetysajastimen tarpeettoman laukeamisen. Tämä aiheuttaa useiden pakettien turhan uudelleenlähetyksen ja vaikeuttaa TCP:n ruuhkanvalvonta-algoritmien toimintaa. Väitöstyössä ehdotetaan F-RTO -nimistä parannusta TCP:n uudelleenlähetysalgoritmeihin, joka pyrkii havaitsemaan turhat uudelleenlähetykset ja välttämään edellä mainitut ongelmat tällaisissa tilanteissa. Väitöstyö analysoi F-RTO:n suorituskykyä erilaisissa kommunikaatioskenaarioissa ja tutkii erilaisia variaatioita perusalgoritmiin. Lisäksi väitöskirjassa tutkitaan TCP:n lähetysnopeuden pikaista sopeuttamista vallitseville siirto-olosuhteille. Normaalisti TCP tarvitsee huomattavan ajan löytääkseen oikean siirtonopeuden yhteyden alussa, mikäli siirtolinkki on erityisen nopea ja siirtoviiveet verraten pitkiä. Tämä on tilanne uusimmissa langattomissa kommunikaatioteknologioissa. Samankaltainen ongelma esiintyy myös, mikäli TCP-yhteys vaihtaa käyttämäänsä siirtoteknologiaa kesken yhteyden esimerkiksi liikkuvuuden seurauksena. Tämä voi tapahtua uusimmissa päätelaitteissa, jotka tukevat useita erityyppisiä radioteknologioita, kuten WLAN ja GPRS. Väitöskirjassa tutkitaan Quick-Start - nimistä mekanismia, joka nopeuttaa huomattavasti TCP:n sopeutumisnopeutta edellä mainitun kaltaisissa tilanteissa. Työssä tarkastellaan erilaisia algoritmeja Quick-Startin käyttöön ja analysoidaan simulointien avulla algoritmien toimintaa erilaisissa ympäristöissä. Väitöstyössä esitetyillä tuloksilla Internet-kommunikaation suorituskykyä ja käytettävyyttä langattomilla laitteilla voidaan parantaa huomattavasti

Cross-layer Assisted TCP Algorithms for Vertical Handoff

The ever expanding growth of the wireless access to the Internet in recent years has led to the proliferation of wireless and mobile devices to connect to the Internet. This has created the possibility of mobile devices equipped with multiple radio interfaces to connect to the Internet using any of several wireless access network technologies such as GPRS, WLAN and WiMAX in order to get the connectivity best suited for the application. These access networks are highly heterogeneous and they vary widely in their characteristics such as bandwidth, propagation delay and geographical coverage. The mechanism by which a mobile device switches between these access networks during an ongoing connection is referred to as vertical handoff and it often results in an abrupt and significant change in the access link characteristics. The most common Internet applications such as Web browsing and e-mail make use of the Transmission Control Protocol (TCP) as their transport protocol and the behaviour of TCP depends on the end-to-end path characteristics such as bandwidth and round-trip time (RTT). As the wireless access link is most likely the bottleneck of a TCP end-to-end path, the abrupt changes in the link characteristics due to a vertical handoff may affect TCP behaviour adversely degrading the performance of the application. The focus of this thesis is to study the effect of a vertical handoff on TCP behaviour and to propose algorithms that improve the handoff behaviour of TCP using cross-layer information about the changes in the access link characteristics. We begin this study by identifying the various problems of TCP due to a vertical handoff based on extensive simulation experiments. We use this study as a basis to develop cross-layer assisted TCP algorithms in handoff scenarios involving GPRS and WLAN access networks. We then extend the scope of the study by developing cross-layer assisted TCP algorithms in a broader context applicable to a wide range of bandwidth and delay changes during a handoff. And finally, the algorithms developed here are shown to be easily extendable to the multiple-TCP flow scenario. We evaluate the proposed algorithms by comparison with standard TCP (TCP SACK) and show that the proposed algorithms are effective in improving TCP behavior in vertical handoff involving a wide range of bandwidth and delay of the access networks. Our algorithms are easy to implement in real systems and they involve modifications to the TCP sender algorithm only. The proposed algorithms are conservative in nature and they do not adversely affect the performance of TCP in the absence of cross-layer information.Käytämme enenevissä määrin kannettavia päätelaitteita (esim. matkapuhelin, kannettava tietokone) erilaisiin sovelluksiin kuten sähköpostin lukemiseen, verkon selaamiseen, musiikin lataamiseen ja kuuntelemiseen, pelien pelaamiseen ja laskujen maksamiseen riippumatta olinpaikastamme tai liikkuvuudestamme. Pystymme yhdistämään laitteemme Internetiin milloin tahansa missä tahansa. Langattomat verkot, jotka mahdollistavat laitteen kytkemisen Internetiin radion kautta käyttävät moninaisia teknologioita ja eroavat laajalti ominaisuuksiltaan. Esimerkiksi langaton lähiverkko (WLAN), jota voidaan käyttää rakennuksen sisällä, on matkapuhelinverkkoa (esim. GPRS) nopeampi verkko, kun taas GPRS-kenttä voi ulottua kokonaisen kaupungin tai maan alueelle ja laajemmallekin. Kannettava päätelaite, jossa on monia radioliittymiä, voi siirtyä käyttämään mitä tahansa monista saatavilla olevistaverkoista riippuen olinpaikasta tai käytettävän sovelluksen tarpeista. Verkonvaihto viittaa tähän verkosta toiseen siirtymiseen, ja se tunnetaan vertikaalisena verkonvaihtona, kun siirtymisen kohteena olevien verkkojen teknologia eroaa toisistaan. TCP on tietoliikenneohjelmisto, jota sekä tiedon lähettäjä että vastaanottaja käyttävät kuljettamaan sovelluksen tiedon luotettavasti. TCP säätelee tiedon lähetysnopeutta riippuen Internetin resurssien saatavuudesta. TCP:n käyttäytyminen riippuu päästä-päähän polun ominaisuuksista ja erityisesti pullonkaulayhteydestä, siitä yhteydestä, jolla on minimikapasiteetti polulla. Langaton yhteys, joka yhdistää kannettavan laitteen Internetiin on usein pullonkaulayhteys, ja äkillinen muutos sen ominaisuuksissa vertikaalisen siirtymän aikana vaikuttaa merkittävästi TCP:n suorituskykyyn ja siten koko sovelluksen laatuun. Tämä työssä on keskitytty tutkimaan TCP:n toimintaa vertikaalisessa verkonvaihdon yhteydessä ja suunnittelemaan algoritmeja, jotka parantavat sen suorituskykyä vertikaalisen verkonvaihdon yhteydessä. Suunnitellut algoritmit käyttävät hyväksi tietoa vertikaaliseen verkonvaihtoon liittyvien langattomien yhteyksien ominaisuuksista. Ensimmäinen tapaustutkimuskohde liittyy WLAN-GPRS -ympäristöön, jossa TCP saa minimimäärän tietoa verkonvaihtoon liittyen. Tulokset näyttävät, että TCP:n suorituskykyä voidaan parantaa huomattavasti. Tutkimusta on laajennettu kattamaan verkonvaihto yleisemmässä tapauksessa käyttäen karkeita arvioita ko. verkkojen ominaisuuksista. Kehitettyjen algoritmien toiminnallisuus on evaluoitu simulaatiokokeilla kattaen laajan joukon ominaisuuksiltaan erilaisia verkkoja. Tulokset osoittavat, että TCP-suorituskykyä voidaan parantaa vertikaalisen verkonvaihdon yhteydessä huomattavasti tätä lähestymistapaa käyttäen. Kehitetyt algoritmit voivat olla hyödyksi etsiessämme ratkaisuja kannettavien laitteiden todellisen käytön tarpeisiin

Recent Advances in Wireless Communications and Networks

This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters

Quality of service differentiation for multimedia delivery in wireless LANs

Delivering multimedia content to heterogeneous devices over a variable networking environment while maintaining high quality levels involves many technical challenges. The research reported in this thesis presents a solution for Quality of Service (QoS)-based service differentiation when delivering multimedia content over the wireless LANs. This thesis has three major contributions outlined below: 1. A Model-based Bandwidth Estimation algorithm (MBE), which estimates the available bandwidth based on novel TCP and UDP throughput models over IEEE 802.11 WLANs. MBE has been modelled, implemented, and tested through simulations and real life testing. In comparison with other bandwidth estimation techniques, MBE shows better performance in terms of error rate, overhead, and loss. 2. An intelligent Prioritized Adaptive Scheme (iPAS), which provides QoS service differentiation for multimedia delivery in wireless networks. iPAS assigns dynamic priorities to various streams and determines their bandwidth share by employing a probabilistic approach-which makes use of stereotypes. The total bandwidth to be allocated is estimated using MBE. The priority level of individual stream is variable and dependent on stream-related characteristics and delivery QoS parameters. iPAS can be deployed seamlessly over the original IEEE 802.11 protocols and can be included in the IEEE 802.21 framework in order to optimize the control signal communication. iPAS has been modelled, implemented, and evaluated via simulations. The results demonstrate that iPAS achieves better performance than the equal channel access mechanism over IEEE 802.11 DCF and a service differentiation scheme on top of IEEE 802.11e EDCA, in terms of fairness, throughput, delay, loss, and estimated PSNR. Additionally, both objective and subjective video quality assessment have been performed using a prototype system. 3. A QoS-based Downlink/Uplink Fairness Scheme, which uses the stereotypes-based structure to balance the QoS parameters (i.e. throughput, delay, and loss) between downlink and uplink VoIP traffic. The proposed scheme has been modelled and tested through simulations. The results show that, in comparison with other downlink/uplink fairness-oriented solutions, the proposed scheme performs better in terms of VoIP capacity and fairness level between downlink and uplink traffic

Building a test bed for simulation analysis for the internet of things

Mestrado com dupla diplomação com a Universidade Tecnológica e Federal do ParanáThe Internet of Things (IoT) enables the mix between the physical and informational world. Physical objects will be able to see, hear, think together, share information and coordinate decisions, without human interference in a variety of domains. To enable this vision of IoT in large scale is expected of the equipment to be low-cost, mobile, power efficient, computational constrained, and wireless communication enabled. This project performs an extensive overview of the state-of-the-art in communication technologies for IoT, simulation theory and tools. It also describes test bed for IoT simulation and its implementation. The simulation was built with Castalia Simulator (i.e. Wireless Sensor Networks (WSN) network) and INET framework (i.e. IP network), both extends OMNeT++ features. There are two independent networks that communicate through files and exchange information about source, destination, payload and simulation time. Analyzing the outputs is possible to assure that the routing protocol that is provided in the Castalia Simulator does not provide any advantage in terms of packets loss, packets reception or energy consumption.A Internet das Coisas (IoT) permite a mistura entre o mundo físico e informacional. Objetos físicos serão capazes de ver, ouvir, pensar juntos, compartilhar informações e coordenar decisões, sem interferência humana em uma variedade de domínios. Para permitir essa visão de IoT em larga escala, espera-se que o equipamento seja de baixo custo, móvel, eficiente em termos de energia, com restrições computacionais e possibilite a comunicação sem fio. Este projeto faz uma extensa visão geral do estado da arte em tecnologias de comunicação para IoT, teoria de simulação e ferramentas. Também descreve o banco de testes para simulação de IoT e sua implementação. A simulação foi construída com o Simulador Castalia (ou seja, rede WSN) e o framework INET (ou seja, rede IP), ambos estendem os recursos do OMNeT ++. Existem duas redes independentes que se comunicam através de arquivos e trocam informações sobre origem, destino, carga útil e tempo de simulação. Analisando os resultados é possível garantir que o protocolo de roteamento que é fornecido no Simulador Castalia não oferece qualquer vantagem em termos de quebra de pacotes, recepção de pacotes ou consumo de energia

Proposta 3GPP de indicadores de desempenho de rede - R4 CS Core Network

Mestrado em Engenharia Electrónica e TelecomunicaçõesO mercado de telecomunicações tem vindo a tornar-se cada vez mais competitivo e agressivo devido à diminuição das margens dos operadores de telecomunicações. Este facto é igualmente relevante no mercado das redes móveis em que este trabalho se foca. A maior parte dos actuais mercados de redes móveis pauta-se por uma consolidação da sua base instalada e por uma optimização dos recursos existentes. Por uma questão de estratégia comercial e técnica (não dependência de um único fornecedor) é frequente os operadores de redes móveis terem mais do que um fornecedor de equipamentos de telecomunicações para a sua rede. Devido a este facto, os problemas das redes com multi-fabricantes agudizou-se o que levou à premente necessidade de se arranjar uma linguagem comum através da qual se consiga ter uma ideia do nível global de desempenho alcançado e dos pontos críticos em que a rede pode melhorar o seu desempenho. É nesta problemática que o presente trabalho se foca. Neste momento, o 3GPP tem definidos uma quantidade vasta de indicadores de desempenho de rede para a área Circuit Switch (CS) Core Network (CN) mas ainda não tem definidos os seus Key Performance Indicators (KPIs). Tendo como base os indicadores de desempenho 3GPP existentes, esta Dissertação propõe um conjunto de KPIs que possibilitam a análise do desempenho da rede Core Network ao nível da sua parte CS. Esta Dissertação apresenta as propostas de KPIs para a rede CS, as quais estão divididas em três partes. Numa primeira parte são apresentados os KPIs relativos ao MSC Server (MSS) ao nível da análise de acessibilidade, utilização e mobilidade. Na segunda secção são apresentados os KPIs relativos ao Media Gateway (MGW) ao nível da análise de acessibilidade, integridade e utilização. Finalmente na terceira e última secção apresentam-se os KPIs associados ao HLR.The telecommunications market has become increasingly competitive and aggressive due to the decreasing margins of telecom operators. This fact is also relevant in the mobile networks market in which this Thesis is focused. Most of today's mobile networks is guided by a consolidation of its installed base and by optimizing existing resources. As a matter of business strategy and technique (not dependent on one supplier) it is common for the mobile network operators to have more than one telecommunications equipment supplier. Due to this, the problems of multi-vendor networks has worsened leading to the urgent need to find a common language that everyone speaks and, through which, can get an idea of overall performance level achieved and critical points where the network can improve its performance. This paper is focused on this issue. Currently, 3GPP has defined a wide range of network performance indicators for the Core Network (CN) Circuit Switch (CS) area but, nothing is yet set in what Key Performance Indicators (KPIs) is concerned. The purpose of this Thesis is, based on already existent 3GPP performance indicators, recommend a set of KPIs to enable the CS CN performance analysis. This Thesis present the CS KPI proposals which are divided in three main parts. In the first part, are presented the MSC Server (MSS) KPIs at accessibility analysis, usage and mobility levels. In the second part are presented the Media Gateway (MGW) related KPIs at accessibility analysis, integrity and usage levels. Finally we have the third and last part where the HLR related KPIs are presented

Cross-layer energy-efficient schemes for multimedia content delivery in heterogeneous wireless networks

The wireless communication technology has been developed focusing on fulfilling the demand in various parts of human life. In many real-life cases, this demand directs to most types of commonly-used rich-media applications which – with diverse traffic patterns - often require high quality levels on the devices of wireless network users. Deliveries of applications with different patterns are accomplished using heterogeneous wireless networks using multiple types of wireless network structure simultaneously. Meanwhile, content deliveries with assuring quality involve increased energy consumption on wireless network devices and highly challenge their limited power resources. As a result, many efforts have been invested aiming at high-quality and energy-efficient rich-media content deliveries in the past years. The research work presented in the thesis focuses on developing energy-aware content delivery schemes in heterogeneous wireless networks. This thesis has four major contributions outlined below: 1. An energy-aware mesh router duty cycle management scheme (AOC-MAC) for high-quality video deliveries over wireless mesh networks. AOC-MAC manages the sleep-periods of mesh devices based on link-state communication condition, reducing their energy consumption by extending their sleep-periods. 2. An energy efficient routing algorithm (E-Mesh) for high-quality video deliveries over wireless mesh networks. E-Mesh evolves an innovative energy-aware OLSR-based routing algorithm by taking energy consumption, router position and network load into consideration. 3. An energy-aware multi-flow-based traffic load balancing scheme (eMTCP) for multi-path content delivery over heterogeneous wireless networks. The scheme makes use of the MPTCP protocol at the upper transport layer of network, allowing data streams to be delivered across multiple consequent paths. Meanwhile, this benefit of MPTCP is also balanced with energy consumption awareness by partially off-loading traffic from the paths with higher energy cost to others. 4. A MPTCP-based traffic-characteristic-aware load balancing mechanism (eMTCP-BT) for heterogeneous wireless networks. In eMTCP-BT, mobile applications are categorized according to burstiness level. eMTCP-BT increases the energy efficiency of the application content deliveries by performing a MDP-based distribution of traffic delivery via the available wireless network interfaces and paths based on the traffic burstiness level

A-Interface Over Internet Protocol For User-Plane Connection Optimization In GSM/EDGE Radio Access Network

This thesis will cover a detailed study about the main motivations and benefits from using IP as a transport protocol for specifically A-interface in GERAN for Circuit Switched User-Plane (CS-UP) connection, in addition to the required protocols. The main study in this document will be around Real Time Protocol (RTP), Real Time Control Protocol (RTCP) negotiation for RTP packets multiplexing, for both cases, with and without RTP header compression. The focus will be about the communication between the Base Station Controller (BSC) and the Media GateWay (MGW), the bandwidth gain in accordance to the multiplexing delay for processing and buffering, the voice Quality of Service (QoS) and some other parameters