Marisa Catalan

Evaluating performance of real ad-hoc networks using AODV with hello message mechanism for maintaining local connectivity

Mobile ad-hoc network (MANET) technology is an essential piece in the path towards a ubiquitous Internet. MANET routing protocol parameter configuration should be further analyzed since it may significantly impact network performance. In this paper, we perform tests in real MANET environments using the ad-hoc on-demand distance vector (AODV) routing protocol. We study the influence of the protocol, the implementation and a set of AODV link maintenance mechanisms parameter values on network performance, suggesting that usage of different settings from those proposed by default increase reactivity after topology changes with small impact on bandwidth and power consumption in a set of scenarios

TCP/IP analysis and optimization over a precommercial live UMTS network

3G wireless networks such as UMTS are currently providing wide area Internet access. However, the Internet protocols exhibit a suboptimal performance in such scenarios. In this paper we first characterize a live UMTS link from the IP level. We identify critical features such as high latency, delay spikes, high packet loss probability and connectivity gaps, specially when the user moves between cells. Next, we test a set of TCP configurations, demonstrating that TCP performance can be optimized over UMTS by the usage of adequate end-to-end mechanisms and parameter values.

Ubiquitous Web Access: Collaborative Optimization and Dynamic Content Negotiation

Traditionally, cellular wide area networks like UMTS are used as Internet access networks for particular users but, in some cases, they can be employed to provide Internet access to other smaller networks as well. The main inconvenient is that cellular networks have not the same bandwidth than wired networks and therefore, the cellular channel becomes a network bottle-neck. To help to mitigate this situation and in order to improve the users experience different optimization techniques exist, especially in web traffic. This paper studies first the existing synergies at HTTP layer between device capabilities expression, content negotiation, channel optimization and content adaptation. And secondly, it presents a system where HTTP requests transmission is optimized, showing a significant improvement in response time by means of HTTP header reduction over the cellular channel. In order to obtain a successful browsing experience, headers should be restored when reaching the Internet. This dynamic header reconstruction allows giving enriched and more expressive information about users device and browser capabilities. Thus navigation speed and users QoE can be enhanced by means of dynamic content negotiation in order to obtain adapted (and lighter) content and responses from web servers and adaptation proxies alike.

Optimizing TCP/IP parameters over GPRS and WLAN networks

The growth of both the Internet and mobile systems provides the way for wireless access to the Internet. Internet based applications are mostly based on a reliable transport service, TCP (transmission control protocol), which is one of the responsible for applications performance. In this paper we characterize two currently available radio access links, the general packet radio service (GPRS) and the IEEE 802.11b standards, at the IP level, and we show the effects and optimization of some TCP parameters in these networks.

Internet traffic analysis and optimization over a precommercial live UMTS network

3G wireless networks such as UMTS are currently providing wide area Internet access. However, the Internet protocols exhibit a suboptimal performance in such scenarios. In this paper we first characterize a live UMTS link from the IP level. We identify critical features such as high latency, delay spikes, high packet loss probability and connectivity gaps, specially when the user moves between cells. Next, we test a set of TCP configurations, demonstrating that TCP performance can be optimized over UMTS by the usage of adequate end-to-end mechanisms and parameter values. Finally, we perform a preliminary study of applications behavior over UMTS.

Implementation and Evaluation of the Enhanced Header Compression (IPHC) for 6LoWPAN

6LoWPAN defines how to carry IPv6 packets over IEEE 802.15.4 low power wireless or sensor networks. Limited bandwidth, memory and energy resources require a careful application of IPv6 in a LoWPAN. The IEEE 802.15.4 standard defines a maximum frame size of 127 bytes that decreases to 102 bytes considering the header overhead. A further reduction is due to the security, network and transport protocols header overhead that, in case of IPv6 and UDP, leave only 33 bytes for application data. A compression algorithm is necessary in order to reduce the overhead and save space in data payload. This paper describes and compares the proposed IPv6 header compression mechanisms for 6LoWPAN environments.

TRESCIMO: European union and South African Smart City contextual dimensions

Cities increasingly face challenges related to pollution, efficient use of resources (e.g. water, energy) and ensuring a good quality of life for its citizens. Solutions built on existing and emerging technologies such as Cloud computing, Internet of Things, Machine-to-Machine and data analytics can improve on or create services able to address these challenges. These solutions are seen as contributors in creating a Smart City. In Europe Smart Cities have been implemented, while South Africa has only recently started with Smart City initiatives. Current thinking has been to replicate international Smart City instances in South Africa. However, an open question is raised if this is an optimal strategy as differences in context might impact on the delivery of services. This paper extracts and compares contextual differences between Europe and South Africa, and based on those insights analyse whether full European solutions will deliver on the promise of a South African Smart City. Furthermore the question is raised if insights into a South African Smart City can strengthen European initiatives. A need for inter-continental automated testing facilities such as those developed by TRESCIMO is identified through which integrated experiments can be conducted to provide insight and answers.

Optimizing TCP parameters over GPRS and WLAN real networks

Internet based applications are mostly based on a reliable transport service. TCP (transmission control protocol) is one of the protocols responsible for applications performance. Mobile users access to Internet services through 2.5 and 3 Generation networks, which have a significant latency due to error mechanisms introduced at the link layer, as well as transmission delays in the radio access networks. High latency produces interaction with timers of upper protocols. Data rate is other limiting characteristic on these networks. Moreover, data rate changes during a TCP connection due to mobility. TCP can adapt its rate when slow data rate changes thanks to its self-clocking propriety. In case of a sudden change, TCP performance is degraded due to spurious retransmission, and the activation of its congestion control mechanisms. This paper will show the effects and optimization of some TCP parameters over GPRS (general packet radio service) and 802.11b real networks.

Towards programmable and scalable IoT infrastructures for smart cities

Smart Cities applications and infrastructures are actively being developed and rolled out. However, maintenance complexity is significant, often limiting deployments to small regions or small cities. To support gradual or spontaneous infrastructure scaling at region or national levels, infrastructure management that monitors end device connectivity and ensures overall IoT communication reliability becomes key. This article describes a method using intercontinental research facilities that programmatically manages smart devices and their communication with the ultimate aim to elastically deploy IoT servers in the cloud. Implementation details and experimental results of real devices are included.

A Proxy-Based System For Dynamic Content Negotiation And Collaborative Optimization In Heterogenic Environments

Abstract Ubiquitous and Pervasive Computing relies on ubiquitous network access and applications’ context-awareness. This pervasive access implies exchanging traffic with a wide spectrum of devices across heterogenic networks. Services and applications deployed on these networks should adapt its operation and presentation to the characteristics of the underlying network technologies and the actual client device capabilities. Cellulaz wide azea networks like UMTS are used as Internet access networks for particular users but, in some cases, they can also be employed to provide Internet access to other smaller networks. The main inconvenient is that cellular networks have not the same bandwidth as wired networks and therefore, the cellular channel becomes a network bottle-neck. To help to mitigate this situation and in order to improve the user’s experience different optimization techniques exist, especially in web traffic. This paper studies the existing synergies at HTTP layer between device capabilities e...