Jorge Herrera-Tapia

Friendly-Sharing: Improving the Performance of City Sensoring through Contact-Based Messaging Applications

Regular citizens equipped with smart devices are being increasingly used as “sensors” by Smart Cities applications. Using contacts among users, data in the form of messages is obtained and shared. Contact-based messaging applications are based on establishing a short-range communication directly between mobile devices, and on storing the messages in these devices for subsequent delivery to cloud-based services. An effective way to increase the number of messages that can be shared is to increase the contact duration. We thus introduce the Friendly-Sharing diffusion approach, where, during a contact, the users are aware of the time needed to interchange the messages stored in their buffers, and they can thus decide to wait more time in order to increase the message sharing probability. The performance of this approach is anyway closely related to the size of the buffer in the device. We therefore compare various policies either for the message selection at forwarding times and for message dropping when the buffer is full. We evaluate our proposal with a modified version of the Opportunistic Networking Environment (ONE) simulator and using real human mobility traces.

Evaluating the Impact of Data Transfer Time in Contact-Based Messaging Applications

In this letter, we propose an analytical model based on delay differential equations (DDEs) to evaluate the diffusion of messages in groups taking into account the transmission time of the messages. This model was validated through simulation studies using the ONE simulator. Evaluation results show that, considering the impact of data transfer time is of utmost importance, as when message size increases (for example, when transmitting short videos), the diffusion is bounded by this transmission time, and the result is that the diffusion time increases slightly when the number of nodes increases (as opposed to the always decreasing diffusion time of the epidemic diffusion with no delay).

Evaluating the use of sub-gigahertz wireless technologies to improve message delivery in opportunistic networks

The message delivery ratio of mobile opportunistic networks strongly depends on the transmission time, which is closely related either to the mobility of users and to the communication properties of the mobile devices. A larger radio transmission range allows longer contact durations, improving the message dissemination. Furthermore, user mobility is a crucial factor to be considered, especially when the mobile nodes are vehicles, because of their limited freedom of movement and the high relative speed. In this paper, we evaluate the use of a sub-gigahertz wireless technology, namely LoRa (Long Range), to establish links between the mobile users in an opportunistic network in order to augment the number of contacts and their duration. We evaluate the performance of LoRa, comparing it with WiFi, using the Epidemic protocol for message diffusion with realistic vehicular traces. Through simulations, we compare the message delivery probability and the network overhead. These experiments were carried out using the ONE simulator with minor modifications to model the typical behaviour of mobile users. The results show that, in opportunistic networks, increasing the range even while reducing the available bandwidth increases the message delivery ratio.

Power consumption evaluation in vehicular opportunistic networks

The duration of batteries is a key factor that must be considered in the design and deployment of applications and services on mobile devices. The users of this technology are not aware of the energetic impact of the applications executing in their devices, especially if these applications present an adaptive behavior. The goal of this paper is to study the power consumption associated to an opportunistic communication application. This will be achieved by analyzing the different operation stages of an application running on mobile and vehicular devices, using basic statistical analysis calculations on data collected by a logging application. Furthermore, this will allow analysing the impact of this kind of applications regarding battery performance, providing useful information to users and developers. The experiments were executed in an opportunistic network environment, using a floating content approach as a mechanism for information distribution in a geographically delimited zone.

Improving Message Delivery Performance in Opportunistic Networks Using a Forced-Stop Diffusion Scheme

The performance of mobile opportunistic networks strongly depends on contact duration. If the contact lasts less than the required transmission times, some messages will not get delivered, and the whole diffusion scheme will be seriously affected.

Mobility as the Main Enabler of Opportunistic Data Dissemination in Urban Scenarios

The use of opportunistic communications to disseminate common interest messages in an urban scenario have various applications, like sharing traffic status, advertising shop offers, spread alarms, and so on. In this paper, we evaluate the combined use of fixed and mobile nodes to establish an optimal urban opportunistic network aimed at the distribution of general interest data.

Evaluating the Impact of Data Transfer Time and Mobility Patterns in Opportunistic Networks

The Epidemic protocol is an effective way to achieve information diffusion in opportunistic networks. Its performance depends on two key factors: the device mobility pattern,, the message transmission time. The mobility pattern determines the contact time, duration. If contact durations are shorter than the required transmission times, some messages will not get delivered,, the whole diffusion scheme will be seriously hampered. In this paper we evaluate the impact of message transmission times in epidemic diffusion processes. We demonstrate how, when certain conditions hold, forcing devices to stop moving to complete the data delivery process can improve their performance. We implemented this mobility model, called Forced Stop, in the ONE (Opportunistic Networking Environment) simulator,, we show that, for large message sizes, the diffusion performance is increased. These results can be a relevant indication to the designers of opportunistic networks applications that could integrate in their products strategies to inform the user about the need to temporarily stop to increase the overall data delivery.

Assessing the Impact of Mobility on LoRa Communications

The use of LPWAN (Low Powered Wide Area Network) technologies in the scope of the Internet of Things have become the best alternative to send data between devices and cloud systems. Among these technologies, LoRa stands out as a novel and promising system that could be used in areas with a high device density, and in locations where other technologies do not provide enough communications range. In the past, most research works have made experiments in static scenarios, without taking the mobility of the things into account.