Matteo Repetto

Estimation of freeway traffic variables using information from mobile phones

The presence of mobile phones on a freeway can be exploited to provide information on the traffic behavior. To this end, an extension of a standard freeway macroscopic model is presented that allows to describe the dynamic of the overall cars, together with variables representing the percentage of communicating mobile phones. A freeway trunk is divided into sections, each covered by a cell of the wireless network and associated with state variables describing density of vehicles, mean velocity, and percentage of active mobile phones. The measurements of mobile phone densities in the various cells of the network are used to estimate these state variables using an extended Kalman filter. A complex simulation set-up has been developed for the purpose of validation. Simulation results are reported to show the effectiveness and potential of the proposed approach.

A Comprehensive Tutorial for Mobility Management in Data Networks

The convergence towards the IP protocol has made Internet access available almost everywhere; this has leveraged new expectations about continuous and seamless communication, especially when portable devices are involved. Mobility management is a key issue in this context. The original IP specification does not account for mobility. Nevertheless, since the beginning of the Internet there has been a continuous interest in managing nomadic hosts; this has brought to a large number of approaches and protocols that have faced the problem from different perspectives. This paper reviews different approaches to mobility management that have arisen during the years. It is intended to serve as a tutorial for this topic, which draws out the lesson learned until now and depicts a comprehensive picture to foster new ideas and solutions while avoiding duplication of past work.

Design and Implementation of Cooperative Network Connectivity Proxy Using Universal Plug and Play

Reducing the network energy waste is one of the key challenges of the Future Internet. Many Internet-based applications require preserving network connectivity for getting incoming remote service requests or confirming their availability and presence to remote peers by sending periodic keep-alive or heart-beating messages. Billions of dollars of electricity is wasted every year to keep idle or unused network hosts fully powered-up only to maintain the network connectivity. This paper describes a new approach to design and implement the cooperative Network Connectivity Proxy (NCP) for reducing energy waste in the ever-growing future Internet. The NCP is implemented using Universal Plug and Play (UPnP), that uses a set of protocols to allow seamless discovery and interaction between the network hosts and the NCP. The NCP allows all registered network hosts to transition into the low power sleep modes and maintains the network connectivity on their behalf. It handles basic network presence and management protocols like ICMP, DHCP, ARP etc on behalf of the sleeping network hosts and wakes them up only when their resources are required. Depending on the network hosts time usage model, the NCP can provide about 60 to 70% network energy savings.

Smart proxying: An optimal strategy for improving battery life of mobile devices

Improving energy efficiency of mobile devices is one of the main challenges to extend the battery life. The Wireless Network Interface Card (WNIC) or 3G is usually considered as primary source of energy consumption. To reduce the energy consumption, different proxying schemes have been proposed in literature mostly focusing on increasing WNIC idle periods through traffic shaping, reducing number of bits transmitted/received through compression techniques and putting WNIC or even the mobile device itself into sleep mode whenever possible. This paper presents the possible smart proxying schemes for mobile devices and particularly focuses on the Network Connectivity Proxy (NCP) which impersonates the mobile devices during their sleep periods and maintains their network presence. Till now the proxying schemes have only been considered for static networks without taking into account the mobility of mobile devices. This paper proposes possible proxy architectural designs in order to support hosts mobility. Further, challenges and issues with each architectural design and possible solutions to tackle with those challenges have also been addressed.

Network Connectivity Proxy: An optimal strategy for reducing energy waste in network edge devices

A network connected host generates/responds to routine applications and protocols heart-beat messages and is considered as disconnected when it fails to do this. Past studies have revealed that about 60-70% people leave their computers powered up 24/7 in the offices and at homes just to maintain the network connectivity. Huge amount of energy savings are possible if these computers can sleep during idle periods but still maintaining their network presence. Thus, a Network Connectivity Proxy (NCP) can be designed which is a software entity running on a low power network hardware such as switch or router and maintains the network connectivity for high power devices during their sleep periods. This paper describes the design, implementation and evaluation of a cooperative NCP that maintains the basic network and application level presence for the sleeping hosts. It also addresses the generic architecture of our NCP and its client softwares.

A new model for network traffic forecast based on user's mobility in cellular networks with highway stretches

Wireless communications have always faced the scarceness of bandwidth and until today the cellular division has solved this problem by making radio cells always smaller. However, as cell size is reduced, more users will probably require handoffs, and signaling can overload the system. Further, the decrease in cell dimension cannot ensure the best utilization of system resources, because user density in the cell is not constant over the time. Dynamic allocation might be the solution, but it is a complex task, basically due to complexity of the models for the mobility prediction, especially in those environments where users move very fast (e.g. highways). This last one is a typical environment where high mobility of vehicles does not allow small cell sizes and thus system capacity is intrinsically bounded. In this paper, we deploy an analytical model for a cellular network operating in a high mobility environment. Such a model is capable of representing and forecasting wireless system evolution in terms of channel occupancy, starting from the current state of the mobile network and road traffic. This model has been defined by integrating a vehicular traffic model with a wireless cellular communication one. With such approach the dynamic behaviour of the most critical mobile terminals, those associated with vehicles, are described in a very precise and specific way with respect to mobility. Many results obtained with specific simulation tools and herein reported show the good behaviour of our proposal. Copyright

Streaming Multimedia Contents to Nomadic Users in Ubiquitous Computing Environments

Streaming of multimedia data is a common application in todays Internet. The trend towards ubiquitous computing raises expectations from the users about enjoying multimedia contents everywhere and with any device. However, current protocols for streaming data (e.g., RTSP) have not been designed for this purpose, thus they fail in providing the user with a transparent and seamless media experience in nomadic life. In this paper we propose a framework for multimedia delivery and adaptation in mobile environments.We introduce the concept of Personal Address (PA), which is a network address associated to the user instead of a network interface; the proposed framework works at the network layer; it moves the PA among networks and devices to deliver media in a seamless and transparent way.

Design of Home Energy Gateway boosting the development of Smart Grid applications at Home

Smart Grids provide an effective and efficient management of production, transmission, distribution and usage of electricity. One of the main issues in designing applications for Smart Grids is the need to cope with a plethora of different devices, communication protocols and data representations. This paper presents the design of a Home Energy Gateway (HEG) that abstracts heterogeneous devices and communication protocols and can be used to develop intelligent applications following a technology-agnostic approach. It is especially conceived to take over efficient energy management at home. Main design issues of our framework are the ability to automatically discover available devices and appliances, to track their operational status, to support different communication protocols and paradigms and to run concurrently multiple services. As an example of service, we address the implementation of a Network Connectivity Proxy (NCP), which save energy by letting unused ICT devices to remain into low-power states without losing their presence on the network. Further, some preliminary results based on the aforementioned service are also presented.

An Integrated Mobility Framework for Pervasive Communications

Pervasive communications are greatly affected by mobility issues. Users often move and that implies different devices and networks to become available dynamically. Terminal handovers and session migrations could negatively impact the enjoyment of multimedia content in such scenarios. In this paper, we introduce the concept of Personal Address and proposed a mobility framework around it, which accounts for all aspects of mobility. Moreover, we describe an implementation of this framework for interactive Voice-over-IP and for streaming applications; finally, we report the results from our experimental testbed.

Modeling and Identification of Nonlinear Dynamics for Freeway Traffic by Using Information From a Mobile Cellular Network

The high coverage of the territory by cellular networks and the widespread diffusion of mobile terminals aboard vehicles allow one to collect information on the traffic behavior. The problem of selecting a dynamic model to describe the freeway traffic by using the information available from a wireless cellular network is addressed by assuming the distribution of mobile terminals aboard vehicles to be uniform along the carriageway. Two different nonlinear parametrized models of freeway traffic are investigated: the first is an extension to a well-established macroscopic model, while the second is based on a black-box approach and consists in using a neural network to approximate the traffic dynamics. The parameters of such models are identified off line by a least-squares technique. Traffic measurements obtained from a cellular network are employed to identify and validate the proposed models, as shown by means of simulations.