3 research outputs found
Minimização de perdas em redes veiculares com multihoming
The growing interest in Vehicular Ad-hoc NETworks (VANETs) is encouraging
its deployment in new environments, allowing the development of safety
and entertainment applications. Vehicles can connect to other vehicles or
to the infrastructure, providing an Internet connection. The communication
equipment placed inside the vehicles may have multiple network interfaces of
diverse technologies, such as IEEE 802.11p/WAVE, IEEE 802.11a/g/n (Wi-
Fi) and cellular. This diversity enables the exploration of Multihoming (MH)
and Network Coding (NC) mechanisms which can be used to provide higher
bandwidth and reliability to these services, reducing packet losses due to
poor wireless signal quality, therefore improving the final Quality-of-Service
(QoS).
This dissertation enhances the communication quality of a MH vehicular
network by improving its mobility protocol and the NC mechanisms. Specifically,
changes were performed to ensure the reliability of control mobility
messages to help the infrastructure to react faster to the wireless communication
conditions of a mobile node. On a different perspective, it has been
provided a mechanism to enable NC through different technologies being
used in MH, and making use of all technologies simultaneously to code and
recover the packets.
Both approaches were evaluated with real systems in a laboratory scenario.
The obtained results on the reliability of the control messages show that
the new approach is able to provide higher communication reliability, reducing
the packet losses presented in case of an abrupt disconnection, and
when in presence of other connections. For the multi-technology architecture
proposed for the NC, the experimental tests evaluated its impact on the
effective delivery ratio and the delay. The comparative results show that the
multi-technology approach integrated with MH has a better delivery ratio
when compared to the single-technology, despite the small impact on the
packet delay.O interesse crescente em Redes Veiculares está a encorajar a sua implementação
em novos ambientes, permitindo o desenvolvimento de aplicações de
segurança e de entretenimento. Os veículos podem-se ligar a outros veículos
ou à infraestrutura, tendo assim uma ligação à Internet. O equipamento
de comunicação colocado nos veículos poderá ter múltiplas interfaces de
rede de tecnologias diferentes, como por exemplo, IEEE 802.11p/WAVE,
IEEE 802.11a/g/n (Wi-Fi) e celular. Esta diversidade permite a exploração
e utilização de mecanismos de Multihoming e de Network Coding, os quais
podem ser usados para oferecer maior largura de banda e maior fiabilidade a
este tipo de aplicações, reduzindo as perdas de pacotes na presença de um
sinal sem fios de fraca qualidade, melhorando assim a qualidade de serviço.
Esta dissertação tem como objetivo melhorar a qualidade de comunicação de
uma rede veicular que suporta Multihoming, assim como melhorar os seus
mecanismos de Network Coding e do protocolo de mobilidade. Mais especificamente,
foram feitas alterações a nível do processo de handover entre
redes, para ajudar a infraestrutura a reagir mais rapidamente às condições
de comunicação de um nó móvel na rede. Numa perspetiva diferente, foi
desenvolvido um mecanismo que permite a aplicação de Network Coding
através de diferentes tecnologias em Multihoming, o qual faz uso das diferentes
tecnologias simultaneamente para codificar e recuperar os pacotes.
Ambos os mecanismos foram avaliados em cenários de laboratório com sistemas
reais. Os resultados obtidos relativos ao envio das mensagens de
controlo mostram que esta nova abordagem é capaz de fornecer uma comunicação
com maior fiabilidade, reduzindo as perdas de pacotes no caso
de uma desconexão abrupta, e quando na presença de outras tecnologias e
ligações. Quanto à proposta de muti-tecnologia para o Network Coding, os
testes experimentais avaliaram o seu impacto na taxa de entrega de pacotes
efetiva e no atraso de transmissão. Os resultados comparativos evidenciam
que, apesar de ter um pequeno impacto no atraso dos pacotes em comparação
com a abordagem que considera o Network Coding em cada tecnologia
de forma independente, a abordagem de multi-tecnologia apresenta uma
melhor taxa de entrega.CMUP-ERI/TIC/0010/2014Mestrado em Engenharia Eletrónica e Telecomunicaçõe
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Network Coding for Multihop Wireless Networks: Joint Random Linear Network Coding and Forward Error Correction with Interleaving for Multihop Wireless Networks
Optimising the throughput performance for wireless networks is one of the
challenging tasks in the objectives of communication engineering, since wireless
channels are prone to errors due to path losses, random noise, and fading
phenomena. The transmission errors will be worse in a multihop scenario due to its
accumulative effects. Network Coding (NC) is an elegant technique to improve the
throughput performance of a communication network. There is the fact that the bit
error rates over one modulation symbol of 16- and higher order- Quadrature
Amplitude Modulation (QAM) scheme follow a certain pattern. The Scattered
Random Network Coding (SRNC) system was proposed in the literature to exploit
the error pattern of 16-QAM by using bit-scattering to improve the throughput of
multihop network to which is being applied the Random Linear Network Coding
(RLNC). This thesis aims to improve further the SRNC system by using Forward
Error Correction (FEC) code; the proposed system is called Joint RLNC and FEC
with interleaving.
The first proposed system (System-I) uses Convolutional Code (CC) FEC. The
performances analysis of System-I with various CC rates of 1/2, 1/3, 1/4, 1/6, and
1/8 was carried out using the developed simulation tools in MATLAB and compared
to two benchmark systems: SRNC system (System-II) and RLNC system (System-
III). The second proposed system (System-IV) uses Reed-Solomon (RS) FEC
code. Performance evaluation of System IV was carried out and compared to three
systems; System-I with 1/2 CC rate, System-II, and System-III. All simulations were
carried out over three possible channel environments: 1) AWGN channel, 2) a
Rayleigh fading channel, and 3) a Rician fading channel, where both fading
channels are in series with the AWGN channel. The simulation results show that
the proposed system improves the SRNC system. How much improvement gain
can be achieved depends on the FEC type used and the channel environment.Indonesian Government and the University of Bradfor