TCP over low-power and lossy networks: tuning the segment size to minimize energy consumption

Low-power and Lossy Networks (LLNs), like wireless networks based upon the IEEE 802.15.4 standard, have strong energy constraints, and are moreover subject to frequent transmission errors, not only due to congestion but also to collisions and to radio channel conditions. This paper introduces an analytical model to compute the total energy consumption in an LLN due to the TCP protocol. The model allows us to highlight some tradeoffs as regards the choice of the TCP maximum segment size, of the Forward Error Correction (FEC) redundancy ratio, and of the number of link-layer retransmissions, in order to minimize the total energy consumption.Comment: TELECOM Bretagne Research Repor

JTP: An Energy-conscious Transport Protocol for Wireless Ad Hoc Networks

Within a recently developed low-power ad hoc network system, we present a transport protocol (JTP) whose goal is to reduce power consumption without trading off delivery requirements of applications. JTP has the following features: it is lightweight whereby end-nodes control in-network actions by encoding delivery requirements in packet headers; JTP enables applications to specify a range of reliability requirements, thus allocating the right energy budget to packets; JTP minimizes feedback control traffic from the destination by varying its frequency based on delivery requirements and stability of the network; JTP minimizes energy consumption by implementing in-network caching and increasing the chances that data retransmission requests from destinations "hit" these caches, thus avoiding costly source retransmissions; and JTP fairly allocates bandwidth among flows by backing off the sending rate of a source to account for in-network retransmissions on its behalf. Analysis and extensive simulations demonstrate the energy gains of JTP over one-size-fits-all transport protocols.Defense Advanced Research Projects Agency (AFRL FA8750-06-C-0199

An Energy-conscious Transport Protocol for Multi-hop Wireless Networks

We present a transport protocol whose goal is to reduce power consumption without compromising delivery requirements of applications. To meet its goal of energy efficiency, our transport protocol (1) contains mechanisms to balance end-to-end vs. local retransmissions; (2) minimizes acknowledgment traffic using receiver regulated rate-based flow control combined with selected acknowledgements and in-network caching of packets; and (3) aggressively seeks to avoid any congestion-based packet loss. Within a recently developed ultra low-power multi-hop wireless network system, extensive simulations and experimental results demonstrate that our transport protocol meets its goal of preserving the energy efficiency of the underlying network.Defense Advanced Research Projects Agency (NBCHC050053

TCP Optimization through FEC, ARQ and Transmission Power Tradeoffs

TCP performance degrades when end-to-end connections extend over wireless connections --- links which are characterized by high bit error rate and intermittent connectivity. Such link characteristics can significantly degrade TCP performance as the TCP sender assumes wireless losses to be congestion losses resulting in unnecessary congestion control actions. Link errors can be reduced by increasing transmission power, code redundancy (FEC) or number of retransmissions (ARQ). But increasing power costs resources, increasing code redundancy reduces available channel bandwidth and increasing persistency increases end-to-end delay. The paper proposes a TCP optimization through proper tuning of power management, FEC and ARQ in wireless environments (WLAN and WWAN)

JTP, an energy-aware transport protocol for mobile ad hoc networks (PhD thesis)

Wireless ad-hoc networks are based on a cooperative communication model, where all nodes not only generate traffic but also help to route traffic from other nodes to its final destination. In such an environment where there is no infrastructure support the lifetime of the network is tightly coupled with the lifetime of individual nodes. Most of the devices that form such networks are battery-operated, and thus it becomes important to conserve energy so as to maximize the lifetime of a node. In this thesis, we present JTP, a new energy-aware transport protocol, whose goal is to reduce power consumption without compromising delivery requirements of applications. JTP has been implemented within the JAVeLEN system. JAVeLEN [RKM+08], is a new system architecture for ad hoc networks that has been developed to elevate energy efficiency as a first-class optimization metric at all protocol layers, from physical to transport. Thus, energy gains obtained in one layer would not be offset by incompatibilities and/or inefficiencies in other layers. To meet its goal of energy efficiency, JTP (1) contains mechanisms to balance end-toend vs. local retransmissions; (2) minimizes acknowledgment traffic using receiver regulated rate-based flow control combined with selected acknowledgments and in-network caching of packets; and (3) aggressively seeks to avoid any congestion-based packet loss. Within this ultra low-power multi-hop wireless network system, simulations and experimental results demonstrate that our transport protocol meets its goal of preserving the energy efficiency of the underlying network. JTP has been implemented on the actual JAVeLEN nodes and its benefits have been demonstrated on a real system

JTP, an energy-aware transport protocol for mobile ad hoc networks

Wireless ad-hoc networks are based on a cooperative communication model, where all nodes not only generate traffic but also help to route traffic from other nodes to its final destination. In such an environment where there is no infrastructure support the lifetime of the network is tightly coupled with the lifetime of individual nodes. Most of the devices that form such networks are battery-operated, and thus it becomes important to conserve energy so as to maximize the lifetime of a node. In this thesis, we present JTP, a new energy-aware transport protocol, whose goal is to reduce power consumption without compromising delivery requirements of applications. JTP has been implemented within the JAVeLEN system. JAVeLEN~\cite{javelen08redi}, is a new system architecture for ad hoc networks that has been developed to elevate energy efficiency as a first-class optimization metric at all protocol layers, from physical to transport. Thus, energy gains obtained in one layer would not be offset by incompatibilities and/or inefficiencies in other layers. To meet its goal of energy efficiency, JTP (1) contains mechanisms to balance end-to-end vs. local retransmissions; (2) minimizes acknowledgment traffic using receiver regulated rate-based flow control combined with selected acknowledgments and in-network caching of packets; and (3) aggressively seeks to avoid any congestion-based packet loss. Within this ultra low-power multi-hop wireless network system, simulations and experimental results demonstrate that our transport protocol meets its goal of preserving the energy efficiency of the underlying network. JTP has been implemented on the actual JAVeLEN nodes and its benefits have been demoed on a real system

Networking And Security Solutions For Vanet Initial Deployment Stage

Vehicular ad hoc network (VANET) is a special case of mobile networks, where vehicles equipped with computing/communicating devices (called smart vehicles ) are the mobile wireless nodes. However, the movement pattern of these mobile wireless nodes is no more random, as in case of mobile networks, rather it is restricted to roads and streets. Vehicular networks have hybrid architecture; it is a combination of both infrastructure and infrastructure-less architectures. The direct vehicle to vehicle (V2V) communication is infrastructure-less or ad hoc in nature. Here the vehicles traveling within communication range of each other form an ad hoc network. On the other hand, the vehicle to infrastructure (V2I) communication has infrastructure architecture where vehicles connect to access points deployed along roads. These access points are known as road side units (RSUs) and vehicles communicate with other vehicles/wired nodes through these RSUs. To provide various services to vehicles, RSUs are generally connected to each other and to the Internet. The direct RSU to RSU communication is also referred as I2I communication. The success of VANET depends on the existence of pervasive roadside infrastructure and sufficient number of smart vehicles. Most VANET applications and services are based on either one or both of these requirements. A fully matured VANET will have pervasive roadside network and enough vehicle density to enable VANET applications. However, the initial deployment stage of VANET will be characterized by the lack of pervasive roadside infrastructure and low market penetration of smart vehicles. It will be economically infeasible to initially install a pervasive and fully networked iv roadside infrastructure, which could result in the failure of applications and services that depend on V2I or I2I communications. Further, low market penetration means there are insufficient number of smart vehicles to enable V2V communication, which could result in failure of services and applications that depend on V2V communications. Non-availability of pervasive connectivity to certification authorities and dynamic locations of each vehicle will make it difficult and expensive to implement security solutions that are based on some central certificate management authority. Nonavailability of pervasive connectivity will also affect the backend connectivity of vehicles to the Internet or the rest of the world. Due to economic considerations, the installation of roadside infrastructure will take a long time and will be incremental thus resulting in a heterogeneous infrastructure with non-consistent capabilities. Similarly, smart vehicles will also have varying degree of capabilities. This will result in failure of applications and services that have very strict requirements on V2I or V2V communications. We have proposed several solutions to overcome the challenges described above that will be faced during the initial deployment stage of VANET. Specifically, we have proposed: A VANET architecture that can provide services with limited number of heterogeneous roadside units and smart vehicles with varying capabilities. A backend connectivity solution that provides connectivity between the Internet and smart vehicles without requiring pervasive roadside infrastructure or large number of smart vehicles. A security architecture that does not depend on pervasive roadside infrastructure or a fully connected V2V network and fulfills all the security requirements. v Optimization solutions for placement of a limited number of RSUs within a given area to provide best possible service to smart vehicles. The optimal placement solutions cover both urban areas and highways environment

Transporte de informação directamente sobre sistemas de comunicação ópticos

Mestrado em Engenharia ElectrónicaNum futuro próximo, a informação transmitida entre vários utilizadores, seja áudio, vídeo ou dados, poderá ser transportada directamente sobre redes ópticas. Neste sentido, têm sido estudadas e analisadas várias tecnologias emergentes de redes ópticas, que culminaram com o aparecimento de soluções que permitem a integração de redes IP (Internet Protocol) sobre redes ópticas. Tendo em vista este cenário, o objectivo deste trabalho foi o estudo dos mecanismos de transporte de informação sobre sistemas de comunicação ópticos. Foi dada especial relevância a tecnologias ópticas multicanal utilizadas actualmente, o Wavelength Division Multiplexing (WDM) e o Multiprotocol Label Switching (MPLS). Uma vez que uma das formas usuais de avaliar o impacto da camada física nos sistemas de comunicação é através das taxa de erro binários, foi efectuada a caracterização da camada física em termos de taxas de erros binários e da probabilidade de erros na transmissão de pacotes de informação. Este estudo englobou várias fases, nomeadamente a caracterização do meio de transmissão, a fibra (através da taxa de erros binários e do factor Q), e a análise do impacto dos erros binários nas camadas de ligação de dados, de rede e de transporte, traduzida na probabilidade de erros em sequências de bits. Foi também abordado o impacto dos esquemas de detecção e/ou de correcção de erros utilizados nas várias camadas protocolares. Finalmente, foi analisado e caracterizado o comportamento da rede em função das características físicas do canal de transmissão.In a near future, information (audio, video and data) may be transmitted between several users directly over optical networks. Several emerging technologies on optical networks, which allow the IP (Internet Protocol) integration in the optical domain, have already been widely studied and analyzed. Keeping in mind this scenario, the goal of this work was the study of the information transport mechanisms over optical communication systems. Special attention was given to technologies currently used, the Wavelength Division Multiplexing (WDM) and the Multiprotocol Label Switching (MPLS). The Bit Error Rate (BER) is used as a measure of the negative effects of all physical impairments on the fibre, being usually a comprehensive criterion for the evaluation of the signal transmission quality. This way, the physical layer characterization was made in terms of BER and/or packet error rate (PER). This study concerned several stages: the fibre characterization in terms of BER and Q-factor, the study of the impact of the binary errors in the network behaviour, and the study and analysis of the error detection and correction schemes used in the several layers. Finally, the network behaviour was analysed and characterized as a function of the channel physical characteristics and constraints