19 research outputs found
Enhancing TCP Performance in Mobile Ad Hoc Network Using Explicit Link Failure Notification (ELFN)
The dynamics and the unpredictable behaviour of a wireless mobile ad hoc network results in the hindrance of providing adequate reliability to network connections. Frequent route changes in the network relatively introduce incessant link failures which eventually degrade TCP performance considerably. In this research, we are going to study the potential improvement of TCP performance when Explicit Link Failure Notification is implemented as opposed to the standard TCP mechanism. ELFN modifies the ‘slow start’ mechanism that is used in standard TCP so that the throughput achieved from the network can be maximized
Mobile Ad-Hoc Networks
Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: vehicular ad-hoc networks, security and caching, TCP in ad-hoc networks and emerging applications. It is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks
Improvements to end-to-end performance of low-power wireless networks
Over the last decades, wireless technologies have become an important part of our daily lives. A plentitude of new types of networks based on wireless technologies have emerged, often replacing wired solutions. In this development, not only the number and the types of devices equipped with wireless transceivers have significantly increased, also the variety of wireless technologies has grown considerably. Moreover, Internet access for wireless devices has paved the way for a large variety of new private, business, and research applications. Great efforts have been made by the research community and the industry to develop standards, specifications, and communication protocols for networks of constrained devices, we refer to as Wireless Sensor Networks (WSNs). The Institute of Electrical and Electronics Engineers (IEEE) defined the 802.15.4 standard for Personal Area Networks (PANs). With the introduction of an adaptation layer which makes IEEE 802.15.4 networks IPv6-capable, interconnecting billions of constrained devices has become possible and is expected to become a reality in the near future. The vision that embraces the idea of interweaving Internet technology with any type of smart objects, such as wearable devices or sensors of a WSN, is called the Internet of Things (IoT).
The main goal of this thesis is the improvement of the performance of low-power wireless networks. Given the wide scope of application scenarios and networking solutions proposed for such networks, the development and optimization of communication protocols for wireless low-power devices is a challenging task: The hardware restrictions of constrained devices, specific application scenarios that may vary from one network to another, and the integration of WSNs into the IoT require new approaches to the design and evaluation of communication protocols. To face these challenges and to find solutions for them, research needs to be carried out. Mechanisms and parameter settings of communication protocol stacks for WSNs that are crucial to the network performance need to be identified, optimized, and complemented by adding new ones.
The first contribution of this thesis is the improvement of end-to-end performance for IEEE 802.15.4-based PANs, where default parameter settings of common communication protocols are analyzed and evaluated with regard to their impact on the network performance. Physical evaluations are carried out in a large testbed, addressing the important question of whether the default and allowed range settings defined for common communication protocols are efficient or whether alternative settings may yield a better performance.
The second contribution of this thesis is the improvement of end-to-end performance for ZigBee wireless HA networks. ZigBee is an important standard for low-power wireless networks and the investigations carried out address the crucial lack of investigation the ZigBee HA performance evaluations through physical experiments and potential ways to improve the network performance based on these experiments.
Eventually, this thesis focuses on the improvement of the congestion control (CC) mechanism applied by the Constrained Application Protocol (CoAP) used in IoT communications. For the handling of the possible congestion in the IoT produced by the plethora of the devices and/or link errors innate to low-power radio communications, the default CC mechanism it lacks an advanced CC algorithm. Given CoAP's high relevance for IoT communications, an advanced CC algorithm should be capable of adapting to these particularities of IoT communications. This thesis contributes to this topic with the design and optimization of the CoAP Advanced Congestion Control/Simple (CoCoA) protocol, an advanced CC mechanism for CoAP.The investigations of advanced CC mechanisms for CoAP involve extensive performance evaluations in simulated networks and physical experiments in real testbeds using different communication technologies.En les últimes dècades, les tecnologies sense fils s'han convertit en una part important de la nostra vida quotidiana. Una à mplia varietat de nous tipus de xarxes basades en tecnologies sense fils han sorgit, sovint reemplaçant solucions cablejades. En aquest desenvolupament, no només el nombre i els tipus de dispositius equipats amb transceptors sense fils han augmentat significativament, també la varietat de tecnologies sense fils ha crescut de manera considerable. D'altra banda, l'accés a Internet per als dispositius sense fils ha donat pas a una gran varietat de noves aplicacions privades, comercials i d'investigació. La comunitat cientÃfica i la indústria han fet grans esforços per desenvolupar normes, especificacions i protocols de comunicació per a xarxes de sensors sense fils (WSNs). L'Institut d'Enginyeria Elèctrica i Electrònica (IEEE) defineix l'està ndard 802.15.4 per a xarxes d'à rea personal (PAN). Amb la introducció d'una capa d'adaptació que possibilita les IEEE 802.15.4 xarxes compatibles amb IPv6, la interconnexió de milers de milions de dispositius restringits s'ha fet possible. La idea d'entreteixir la tecnologia d'Internet amb qualsevol tipus d'objectes intel·ligents, com els dispositius o sensors d'una WSN és coneguda com la Internet de les Coses (IoT). L'objectiu principal d'aquesta tesi és la millora del rendiment de les WSNs. Donada l'à mplia gamma d'escenaris d'aplicacions i solucions de xarxes proposats per a aquest tipus de xarxes, el desenvolupament i l'optimització dels protocols de comunicació per a dispositius de WSNs és una tasca difÃcil: les limitacions de capacitats dels dispositius restringits, escenaris d'aplicació especÃfics que poden variar d'una xarxa a l'altra, i la integració de les WSNs a la IoT requereixen nous enfocaments per al disseny i avaluació de protocols de comunicació. Cal identificar mecanismes i configuracions de parà metres de les piles de protocols de comunicació per a WSNs que són elementals per al rendiment de la xarxa, optimitzar-los, i complementar-los amb l'addició d'altres de nous. La primera contribució d'aquesta tesi és la millora del rendiment extrem a extrem per PANs basat en IEEE 802.15.4, on s'analitza la configuració de parà metres que es fan servir per defecte en protocols de comunicació comuns i s'avalua el seu impacte en el rendiment de la xarxa. Avaluacions fÃsiques en una xarxa de sensors permeten fer front a la important qüestió de si els valors està ndards dels parà metres són eficients o si ajustant-los es pot proporcionar un millor rendiment. La segona contribució d'aquesta tesi és l'optimització del rendiment extrem a extrem de xarxes ZigBee domòtiques (HA) sense fils. ZigBee és un està ndard important per a WSNs. Els estudis duts a terme cobreixen la important falta d'investigació d'avaluacions de rendiment de xarxes HA de ZigBee mitjançant experiments fÃsics i mostrant formes per millorar el rendiment de la xarxa en base d'aquests experiments. Finalment, aquesta tesi es centra en la millora del mecanisme bà sic de control de congestió (CC) aplicada pel Constrained Application Protocol (CoAP) utilitzat en les comunicacions de la IoT. És necessari un algoritme de CC avançat per al control de la possible congestió en la IoT produïda per la plètora de dispositius i/o errors d'enllaç naturals per a les comunicacions de rà dio de baixa potencia. Donada l'alta rellevà ncia de CoAP per a les comunicacions en la IoT, un algoritme CC avançat ha de ser capaç d'adaptar-se a les particularitats de les comunicacions de la IoT. Aquesta tesi contribueix al problema amb el disseny i l'optimització Control de Congestió Avançat / Simple del CoAP (CoCoA), un mecanisme de CC avançat per CoAP. Les investigacions de mecanismes de CC avançats per CoAP impliquen avaluacions extenses en xarxes simulades i experiments fÃsics en xarxes reals utilitzant diferents tecnologies de comunicacions
End-to-End Resilience Mechanisms for Network Transport Protocols
The universal reliance on and hence the need for resilience in network communications has been well established. Current transport protocols are designed to provide fixed mechanisms for error remediation (if any), using techniques such as ARQ, and offer little or no adaptability to underlying network conditions, or to different sets of application requirements. The ubiquitous TCP transport protocol makes too many assumptions about underlying layers to provide resilient end-to-end service in all network scenarios, especially those which include significant heterogeneity. Additionally the properties of reliability, performability, availability, dependability, and survivability are not explicitly addressed in the design, so there is no support for resilience. This dissertation presents considerations which must be taken in designing new resilience mechanisms for future transport protocols to meet service requirements in the face of various attacks and challenges. The primary mechanisms addressed include diverse end-to-end paths, and multi-mode operation for changing network conditions
Concurrent Multipath Transferring in IP Networks: Two IP-level solutions for TCP and UDP
Having multiple network interfaces or gateways available, the Internet users can transfer their data through multiple paths to achieve load balancing, fault-tolerance, and more aggregate bandwidth. However, transferring the packets of the same flow over multiple paths with diverse delays could introduce reordering among the received packets at the destination. In TCP, fast-retransmit/recovery might mistake reordered packets for lost packets and hence degrades the throughput. In UDP, we require larger buffers to keep out-of-order received packets. In this thesis, we propose two approaches at the IP layer to address the reordering problem of TCP and UDP. In the case of TCP, the key observation is that the interleaved reception of the packets at the destination does not trigger the fast-retransmit/recovery mechanism, even though the packets are received reordered. Therefore, the IP layer who is in charge of alternating the packets among the multipath available paths needs to linger on the slower path for at least the delay difference between the paths. In the case of UDP, the proposed approach schedules the packets at the source to have them received in-order at the destination
Proceedings of the Third Edition of the Annual Conference on Wireless On-demand Network Systems and Services (WONS 2006)
Ce fichier regroupe en un seul documents l'ensemble des articles accéptés pour la conférences WONS2006/http://citi.insa-lyon.fr/wons2006/index.htmlThis year, 56 papers were submitted. From the Open Call submissions we accepted 16 papers as full papers (up to 12 pages) and 8 papers as short papers (up to 6 pages). All the accepted papers will be presented orally in the Workshop sessions. More precisely, the selected papers have been organized in 7 session: Channel access and scheduling, Energy-aware Protocols, QoS in Mobile Ad-Hoc networks, Multihop Performance Issues, Wireless Internet, Applications and finally Security Issues. The papers (and authors) come from all parts of the world, confirming the international stature of this Workshop. The majority of the contributions are from Europe (France, Germany, Greece, Italy, Netherlands, Norway, Switzerland, UK). However, a significant number is from Australia, Brazil, Canada, Iran, Korea and USA. The proceedings also include two invited papers. We take this opportunity to thank all the authors who submitted their papers to WONS 2006. You helped make this event again a success
Design and implementation of simulation tools, protocols and architectures to support service platforms on vehicular networks
Tesis por compendioProducts related with Intelligent Transportation Systems (ITS) are becoming
a reality on our roads.
All car manufacturers are starting to include Internet
access in their vehicles and to integrate smartphones directly from the
dashboard, but more and more services will be introduced in the near future.
Connectivity through "vehicular networks" will become a cornerstone of every
new proposal, and offering an adequate quality of service is obviously desirable.
However, a lot of work is needed for vehicular networks to offer performances
similar to those of the wired networks.
Vehicular networks can be characterized by two main features: high variability
due to mobility levels that can reach up to 250 kilometers per hour,
and heterogeneity, being that various competing versions from different vendors
have and will be released. Therefore, to make the deployment of efficient
services possible, an extensive study must be carried out and adequate tools
must be proposed and developed. This PhD thesis addresses the service deployment
problem in these networks at three different levels: (i) the physical
and link layer, showing an exhaustive analysis of the physical channel and
models; (ii) the network layer, proposing a forwarding protocol for IP packets;
and (iii) the transport layer, where protocols are proposed to improve data
delivery.
First of all, the two main wireless technologies used in vehicular networks
where studied and modeled, namely the 802.11 family of standards, particularly
802.11p, and the cellular networks focusing on LTE. Since 802.11p is a
quite mature standard, we defined (i) a propagation and attenuation model
capable of replicating the transmission range and the fading behavior of real
802.11p devices, both in line-of-sight conditions and when obstructed by small
obstacles, and (ii) a visibility model able to deal with large obstacles, such
as buildings and houses, in a realistic manner.
Additionally, we proposed a
model based on high-level performance indicators (bandwidth and delay) for
LTE, which makes application validation and evaluation easier.
At the network layer, a hybrid protocol called AVE is proposed for packet
forwarding by switching among a set of standard routing strategies. Depending
on the specific scenario, AVE selects one out of four different routing solutions:
a) two-hop direct delivery, b) Dynamic MANET On-demand (DYMO), c)
greedy georouting, and d) store-carry-and-forward technique, to dynamically
adapt its behavior to the specific situation.
At the transport layer, we proposed a content delivery protocol for reliable
and bidirectional unicast communication in lossy links that improves content
delivery in situations where the wireless network is the bottleneck.
It has
been designed, validated, optimized, and its performance has been analyzed
in terms of throughput and resource efficiency.
Finally, at system level, we propose an edge-assisted computing model that
allows reducing the response latency of several queries by placing a computing
unit at the network edge. This way, traffic traversal through the Internet is
avoided when not needed.
This scheme could be used in both 802.11p and
cellular networks, and in this thesis we decided to focus on its evaluation using
LTE networks.
The platform presented in this thesis combines all the individual efforts to
create a single efficient platform. This new environment could be used by any
provider to improve the quality of the user experience obtainable through the
proposed vehicular network-based services.Los productos relacionados con los Sistemas Inteligentes de Transporte (ITS)
se están transformando en una realidad en nuestras carreteras. Todos los
fabricantes de coches comienzan a incluir acceso a internet en sus vehÃculos y a
facilitar su integración con los teléfonos móviles, pero más y más servicios se
introducirán en el futuro.
La conectividad usando las "redes vehiculares" se
convertirá en la piedra angular de cada nueva propuesta, y ofrecer una calidad
de servicio adecuada será, obviamente, deseable. Sin embargo, se necesita
una gran cantidad de trabajo para que las redes vehiculares ofrezcan un
rendimiento similar al de las redes cableadas.
Las redes vehiculares quedan definidas por sus dos caracterÃsticas básicas:
alto dinamismo, pues los nodos pueden alcanzar una velocidad relativa de más
de 250 km/h; y heterogeneidad, por la gran cantidad de propuestas diferentes
que los fabricantes están lanzando al mercado. Por ello, para hacer posible el
despliegue de servicios sobre ellas, se impone la necesidad de hacer un estudio
en profundidad de este entorno, y deben de proponerse y desarrollarse las
herramientas adecuadas.
Esta tesis ataca la problemática del despliegue de servicios en estas redes
a tres niveles diferentes: (i) el nivel fÃsico y de enlace, mostrando varios análisis
en profundidad del medio fÃsico y modelos derivados para su simulación;
(ii) el nivel de red, proponiendo un protocolo de difusión de la información
para los paquetes IP; y (iii) el nivel de transporte, donde otros protocolos son
propuestos para mejorar el rendimiento del transporte de datos.
En primer lugar, se han estudiado y modelado las dos principales tecnologÃas
inalámbricas que se utilizan para la comunicación en redes vehiculares,
la rama de estándares 802.11, en concreto 802.11p; y la comunicación celular,
en particular LTE. Dado que el estándar 802.11p es un estándar bastante
maduro, nos centramos en crear (i) un modelo de propagación y atenuación
capaz de replicar el rango de transmisión de dispositivos 802.11p reales, en
condiciones de visión directa y obstrucción por pequeños obstáculos, y (ii) un
modelo de visibilidad capaz de simular el efecto de grandes obstáculos, como
son los edifcios, de una manera realista.
Además, proponemos un modelo
basado en indicadores de rendimiento de alto nivel (ancho de banda y retardo)
para LTE, que facilita la validación y evaluación de aplicaciones.
En el plano de red, se propone un protocolo hÃbrido, llamado AVE, para
el encaminamiento y reenvÃo de paquetes usando un conjunto de estrategias
estándar de enrutamiento. Dependiendo del escenario, AVE elige entre cuatro
estrategias diferentes: a) entrega directa a dos saltos, b) Dynamic MANET
On-demand (DYMO) c) georouting voraz, y d) una técnica store-carry-and-
forward, para adaptar su comportamiento dinámicamente a cada situación.
En el plano de transporte, se propone un protocolo bidireccional de distribución
de contenidos en canales con pérdidas que mejora la entrega de contenidos
en situaciones en las que la red es un cuello de botella, como las redes
inalámbricas.
Ha sido diseñado, validado, optimizado, y su rendimiento ha
sido analizado en términos de productividad y eficiencia en la utilización de
recursos.
Finalmente, a nivel de sistema, proponemos un modelo de computación
asistida que permite reducir la latencia en la respuesta a muchas consultas
colocando una unidad de computación en el borde de la red, i.e., la red de
acceso. Este esquema podrÃa ser usado en redes basadas en 802.11p y en redes
celulares, si bien en esta tesis decidimos centrarnos en su evaluación usando
redes LTE.
La plataforma presentada en esta tesis combina todos los esfuerzos individuales
para crear una plataforma única y eficiente. Este nuevo entorno puede
ser usado por cualquier proveedor para mejorar la calidad de la experiencia de
usuario en los servicios desplegados sobre redes vehiculares.Els productes relacionats amb els sistemes intel · ligents de transport (ITS)
s'estan transformant en una realitat en les nostres carreteres. Tots els fabri-
cants de cotxes comencen a incloure accés a internet en els vehicles i a facilitar-
ne la integració amb els telèfons mòbils, però en el futur més i més serveis s'hi
introduiran. La connectivitat usant les xarxes vehicular esdevindrà la pedra
angular de cada nova proposta, i oferir una qualitat de servei adequada serà ,
òbviament, desitjable.
No obstant això, es necessita una gran quantitat de
treball perquè les xarxes vehiculars oferisquen un rendiment similar al de les
xarxes cablejades.
Les xarxes vehiculars queden definides per dues caracterÃstiques bà siques:
alt dinamisme, ja que els nodes poden arribar a una velocitat relativa de més
de 250 km/h; i heterogeneïtat, per la gran quantitat de propostes diferents
que els fabricants estan llançant al mercat.
Per això, per a fer possible el
desplegament de serveis sobre aquestes xarxes, s'imposa la necessitat de fer un
estudi en profunditat d'aquest entorn, i cal proposar i desenvolupar les eines
adequades.
Aquesta tesi ataca la problemà tica del desplegament de serveis en aquestes
xarxes a tres nivells diferents: (i) el nivell fÃsic i d'enllaç , mostrant diverses
anà lisis en profunditat del medi fÃsic i models derivats per simular-lo; (ii) el
nivell de xarxa, proposant un protocol de difusió de la informació per als
paquets IP; i (iii) el nivell de transport, on es proposen altres protocols per a
millorar el rendiment del transport de dades.
En primer lloc, s'han estudiat i modelat les dues principals tecnologies
sense fils que s'utilitzen per a la comunicació en xarxes vehiculars, la branca
d'està ndards 802.11, en concret 802.11p; i la comunicació cel · lular, en partic-
ular LTE. Atès que l'està ndard 802.11p és un està ndard bastant madur, ens
centrem a crear (i) un model de propagació i atenuació capaç de replicar el
rang de transmissió de dispositius 802.11p reals, en condicions de visió directa
i obstrucció per petits obstacles, i (ii) un model de visibilitat capaç de simular
l'efecte de grans obstacles, com són els edificis, d'una manera realista. A més,
proposem un model basat en indicadors de rendiment d'alt nivell (ample de
banda i retard) per a LTE, que facilita la validació i l'avaluació d'aplicacions.
En el pla de xarxa, es proposa un protocol hÃbrid, anomenat AVE, per
a l'encaminament i el reenviament de paquets usant un conjunt d'estratègies
està ndard d'encaminament.
Depenent de l'escenari , AVE tria entre quatre
estratègies diferents: a) lliurament directe a dos salts, b) Dynamic MANET
On-demand (DYMO) c) georouting voraç, i d) una tècnica store-carry-and-
forward, per a adaptar-ne el comportament dinà micament a cada situació.
En el pla de transport, es proposa un protocol bidireccional de distribució
de continguts en canals amb pèrdues que millora el lliurament de continguts
en situacions en què la xarxa és un coll de botella, com les xarxes sense fils.
Ha sigut dissenyat, validat, optimitzat, i el seu rendiment ha sigut analitzat
en termes de productivitat i eficiència en la utilització de recursos.
Finalment, a nivell de sistema, proposem un model de computació assistida
que permet reduir la latència en la resposta a moltes consultes col · locant una
unitat de computació a la vora de la xarxa, és a dir, la xarxa d'accés. Aquest
esquema podria ser usat en xarxes basades en 802.11p i en xarxes cel · lulars, si
bé en aquesta tesi decidim centrar-nos en la seua avaluació usant xarxes LTE.
La plataforma presentada en aquesta tesi combina tots els esforços indi-
viduals per a crear una plataforma única i eficient. Aquest nou entorn pot ser
usat per qualsevol proveïdor per a millorar la qualitat de l'experiència d'usuari
en els serveis desplegats sobre xarxes vehiculars.Báguena Albaladejo, M. (2017). Design and implementation of simulation tools, protocols and architectures to support service platforms on vehicular networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/85333TESISCompendi
Design and Analysis of a Novel Split and Aggregated Transmission Control Protocol for Smart Metering Infrastructure
Utility companies (electricity, gas, and water suppliers), governments, and
researchers recognize an urgent need to deploy communication-based systems to
automate data collection from smart meters and sensors, known as Smart Metering
Infrastructure (SMI) or Automatic Meter Reading (AMR). A smart metering system
is envisaged to bring tremendous benefits to customers, utilities, and
governments. The advantages include reducing peak demand for energy, supporting
the time-of-use concept for billing, enabling customers to make informed
decisions, and performing effective load management, to name a few.
A key element in an SMI is communications between meters and utility servers.
However, the mass deployment of metering devices in the grid calls for studying
the scalability of communication protocols. SMI is characterized by the
deployment of a large number of small Internet Protocol (IP) devices sending
small packets at a low rate to a central server. Although the individual
devices generate data at a low rate, the collective traffic produced is
significant and is disruptive to network communication functionality. This
research work focuses on the scalability of the transport layer
functionalities. The TCP congestion control mechanism, in particular, would be
ineffective for the traffic of smart meters because a large volume of data
comes from a large number of individual sources. This situation makes the TCP
congestion control mechanism unable to lower the transmission rate even when
congestion occurs. The consequences are a high loss rate for metered data and
degraded throughput for competing traffic in the smart metering network.
To enhance the performance of TCP in a smart metering infrastructure (SMI), we
introduce a novel TCP-based scheme, called Split- and Aggregated-TCP (SA-TCP).
This scheme is based on the idea of upgrading intermediate devices in SMI
(known in the industry as regional collectors) to offer the service of
aggregating the TCP connections. An SA-TCP aggregator collects data packets
from the smart meters of its region over separate TCP connections; then it
reliably forwards the data over another TCP connection to the utility server.
The proposed split and aggregated scheme provides a better response to traffic
conditions and, most importantly, makes the TCP congestion control and flow
control mechanisms effective. Supported by extensive ns-2 simulations, we show
the effectiveness of the SA-TCP approach to mitigating the problems in terms of
the throughput and packet loss rate performance metrics.
A full mathematical model of SA-TCP is provided. The model is highly accurate
and flexible in predicting the behaviour of the two stages, separately and
combined, of the SA-TCP scheme in terms of throughput, packet loss rate and
end-to-end delay. Considering the two stages of the scheme, the modelling
approach uses Markovian models to represent smart meters in the first stage and
SA-TCP aggregators in the second. Then, the approach studies the interaction of
smart meters and SA-TCP aggregators with the network by means of standard
queuing models. The ns-2 simulations validate the math model results.
A comprehensive performance analysis of the SA-TCP scheme is performed. It
studies the impact of varying various parameters on the scheme, including the
impact of network link capacity, buffering capacity of those RCs that act as
SA-TCP aggregators, propagation delay between the meters and the utility
server, and finally, the number of SA-TCP aggregators. The performance results
show that adjusting those parameters makes it possible to further enhance
congestion control in SMI. Therefore, this thesis also formulates an
optimization model to achieve better TCP performance and ensures satisfactory
performance results, such as a minimal loss rate and acceptable end-to-end
delay. The optimization model also considers minimizing the SA-TCP scheme
deployment cost by balancing the number of SA-TCP aggregators and the link
bandwidth, while still satisfying performance requirements
Design and Analysis of a Novel Split and Aggregated Transmission Control Protocol for Smart Metering Infrastructure
Utility companies (electricity, gas, and water suppliers), governments, and
researchers recognize an urgent need to deploy communication-based systems to
automate data collection from smart meters and sensors, known as Smart Metering
Infrastructure (SMI) or Automatic Meter Reading (AMR). A smart metering system
is envisaged to bring tremendous benefits to customers, utilities, and
governments. The advantages include reducing peak demand for energy, supporting
the time-of-use concept for billing, enabling customers to make informed
decisions, and performing effective load management, to name a few.
A key element in an SMI is communications between meters and utility servers.
However, the mass deployment of metering devices in the grid calls for studying
the scalability of communication protocols. SMI is characterized by the
deployment of a large number of small Internet Protocol (IP) devices sending
small packets at a low rate to a central server. Although the individual
devices generate data at a low rate, the collective traffic produced is
significant and is disruptive to network communication functionality. This
research work focuses on the scalability of the transport layer
functionalities. The TCP congestion control mechanism, in particular, would be
ineffective for the traffic of smart meters because a large volume of data
comes from a large number of individual sources. This situation makes the TCP
congestion control mechanism unable to lower the transmission rate even when
congestion occurs. The consequences are a high loss rate for metered data and
degraded throughput for competing traffic in the smart metering network.
To enhance the performance of TCP in a smart metering infrastructure (SMI), we
introduce a novel TCP-based scheme, called Split- and Aggregated-TCP (SA-TCP).
This scheme is based on the idea of upgrading intermediate devices in SMI
(known in the industry as regional collectors) to offer the service of
aggregating the TCP connections. An SA-TCP aggregator collects data packets
from the smart meters of its region over separate TCP connections; then it
reliably forwards the data over another TCP connection to the utility server.
The proposed split and aggregated scheme provides a better response to traffic
conditions and, most importantly, makes the TCP congestion control and flow
control mechanisms effective. Supported by extensive ns-2 simulations, we show
the effectiveness of the SA-TCP approach to mitigating the problems in terms of
the throughput and packet loss rate performance metrics.
A full mathematical model of SA-TCP is provided. The model is highly accurate
and flexible in predicting the behaviour of the two stages, separately and
combined, of the SA-TCP scheme in terms of throughput, packet loss rate and
end-to-end delay. Considering the two stages of the scheme, the modelling
approach uses Markovian models to represent smart meters in the first stage and
SA-TCP aggregators in the second. Then, the approach studies the interaction of
smart meters and SA-TCP aggregators with the network by means of standard
queuing models. The ns-2 simulations validate the math model results.
A comprehensive performance analysis of the SA-TCP scheme is performed. It
studies the impact of varying various parameters on the scheme, including the
impact of network link capacity, buffering capacity of those RCs that act as
SA-TCP aggregators, propagation delay between the meters and the utility
server, and finally, the number of SA-TCP aggregators. The performance results
show that adjusting those parameters makes it possible to further enhance
congestion control in SMI. Therefore, this thesis also formulates an
optimization model to achieve better TCP performance and ensures satisfactory
performance results, such as a minimal loss rate and acceptable end-to-end
delay. The optimization model also considers minimizing the SA-TCP scheme
deployment cost by balancing the number of SA-TCP aggregators and the link
bandwidth, while still satisfying performance requirements