Alessandro Leonardi

MACRO: an integrated MAC/routing protocol for geographic forwarding in wireless sensor networks

Sensor networks are characterized by limited battery supplies. Due to this feature, communication protocols specifically designed for these networks should be aimed at minimizing energy consumption. To this purpose, the sensors capability of transmitting with different power levels can be exploited. With this in mind, in this paper an integrated MAC/routing protocol, called MACRO, which exploits the capability of sensor devices to tune their transmission power is introduced. The proposed protocol requires that each node only knows its own coordinates and the coordinates of the destination, but does not require any exchange of location information. In order to select the next relay node, a competition is triggered at each hop, so that the most energy efficient relay node is chosen. This is achieved through maximization of a newly introduced parameter, called weighted progress factor, which represents the progress towards the destination per unit of transmitted power. To this aim, an analytical framework which guarantees that MACRO performs the best choice is derived. MACRO performance is evaluated through ns-2 simulation and compared to other relevant routing schemes. Performance results show that the proposed protocol outperforms other solutions in terms of energy efficiency and boosts data aggregation.

Transmission of VoIP traffic in multihop ad hoc IEEE 802.11b networks: experimental results

In the last decade numerous studies have been carried out into the transmission of VoIP traffic over wireless networks. However, only a few works have addressed the topic of supporting real-time audio applications on multi-hop IEEE 802.11 ad hoc networks from the perspective of simulations and testbeds. This paper presents the results of the implementation of a VoIP testbed on a multihop IEEE 802.11b ad hoc network with stationary hosts. The real-time audio transmission is evaluated using two different multihop routing protocols, AODV and OLSR. The quality of the voice transmission, using different codecs, is measured through different performance metrics such as end-to-end delay, delay jitter and sequence number error.

A Cross-Layer Approach for an Efficient Delivery of TCP/RTP-Based Multimedia Applications in Heterogeneous Wireless Networks

Recent trends in the telecommunication industry have been moving toward the development of ubiquitous information systems, where the provision of a plethora of advanced multimedia services should be possible, regardless of time and space limitations. An efficient and seamless delivery of multimedia services over various types of wireless networks is still a challenging task. The underlying difficulty consists of the disparity in the bandwidth availability over each network type. Indeed, the fundamental challenge upon a handoff phenomenon in a heterogeneous wireless network consists of an efficient probing of the bandwidth availability of the new network, followed by a prompt adjustment of the data delivery rate. This paper presents a cross-layer approach that involves five layers, namely, physical, data link, application, network, and transport layers. The three former layers are used to anticipate the handoff occurrence and to locate the new point of attachment to the network. Based on their feedback, the transport layer is used then to probe the resources of the new network using low-priority dummy packets. Being the most widely used protocol for multimedia delivery, this paper addresses multimedia applications based on the Transmission Control Protocol (TCP) and the Real-time Transport Protocol (RTP). The design of the whole cross-layer architecture is discussed, and enhancements to the two protocols are proposed. The performance of the enhanced TCP and the RTP are evaluated and compared against existing schemes through extensive simulations. The obtained results are encouraging and promising for the delivery of multimedia services in heterogeneous wireless networks.

A MAC/Routing cross-layer approach to geographic forwarding in wireless sensor networks

Geographic forwarding is an emerging paradigm for communications between nodes in sensor networks. No exchange of location information is required, and nodes only have to know their own coordinates and those of the destination. Due to the devices limited processing and storage capabilities, a simplified protocol architecture should be designed so as to make communications in these networks efficient and simple at the same time. Moreover, sensor nodes are battery supplied and, thus, protocol design should be aimed at reducing energy consumption in order to increase network lifetime. In this perspective, one sensor feature recently regarded as of key importance, is the ability to tune the transmission power. This allows the communication range to be varied according to node density and connectivity constraints. In this paper we propose an integrated cross-layer protocol, called MACRO, which integrates MAC and routing layer functionalities in order to support geographic forwarding in wireless sensor networks. In MACRO, a competition is triggered to select the best next relay node while forwarding information to the destination. The competition is based on the evaluation of a weighted progress factor representing the progress towards the destination per unit of transmission power. An analytical paradigm facilitating the most appropriate choice of the next relay is proposed. The proposed solution is assessed through both analysis and ns-2 simulations. Performance results show the advantages of the proposed solution when compared to other geographic forwarding protocols which do not exploit cross-layer features.

A survey of technologies for the internet of things

The number of smart things is growing exponentially. By 2020, tens of billions of things will be deployed worldwide, collecting a wealth of diverse data. Traditional computing models collect in-field data and then transmit it to a central data center where analytics are applied to it, but this is no longer a sustainable model. New approaches and new technologies are required to transform enormous amounts of collected data into meaningful information. Technology also will enable the interconnection around things in the IoT ecosystem but further research is required in the development, convergence and interoperability of the different IoT elements. In this paper, we provide a picture of the main technological components needed to enable the interconnection among things in order to realize IoT concepts and applications.

Improving energy saving and reliability in wireless sensor networks using a simple CRT-based packet-forwarding solution

This paper deals with a novel forwarding scheme for wireless sensor networks aimed at combining low computational complexity and high performance in terms of energy efficiency and reliability. The proposed approach relies on a packet-splitting algorithm based on the Chinese Remainder Theorem (CRT) and is characterized by a simple modular division between integers. An analytical model for estimating the energy efficiency of the scheme is presented, and several practical issues such as the effect of unreliable channels, topology changes, and MAC overhead are discussed. The results obtained show that the proposed algorithm outperforms traditional approaches in terms of power saving, simplicity, and fair distribution of energy consumption among all nodes in the network.

A novel reliable and energy-saving forwarding technique for wireless sensor networks

The main aim of this paper is to generalize and improve a recently proposed forwarding technique based on the Chinese Remainder Theorem (CRT). The proposed technique outperforms more traditional approaches in terms of both energy efficiency and fair distribution of energy consumption, and requires very few changes to the commonly used forwarding schemes for its implementation. In particular, in this paper it is shown how to apply the CRT-based forwarding method on a realistic wireless network where unreliable erasure channels are considered together with topological changes. Furthermore, an analytical model for the novel forwarding technique has been derived and the trade-off between reliability and energy saving has been investigated.

On the Use of Chinese Remainder Theorem for Energy Saving in Wireless Sensor Networks

In this paper we discuss the use of the Chinese Remainder Theorem (CRT) for a novel forwarding scheme in wireless sensor networks. The proposed approach is characterized by a computationally simple packet splitting procedure able to reduce the energy needed for transmission and increase the network lifetime accordingly. Simulation results show that the proposed algorithm outperforms more traditional approaches in terms of both energy efficiency and fair distribution of energy consumption among all nodes in the network.

Timely and energy-efficient communications in rural infostation systems

The infostation communication paradigm represents a good trade-off between the size of investments in infrastructure and the connectivity needs in rural areas. In fact, exploiting the emerging mesh networking technologies, infostations can be deployed with low cost. In infostation systems, mobile nodes achieve network connectivity when they are in the radio coverage of the infostation. Nevertheless, preliminary to the communication, there is a phase in which discovery must be achieved between mobile nodes and the infostation. This is an energy consuming phase that has significant impact on the performance experienced by mobile nodes. In this article the trade-off between energy efficiency and performance experienced by mobile users is discussed. This is an important problem in rural areas since infostations will often be supplied by photovoltaic or eolic generators, which have a cost that increases as the need for energy increases. To carry the study, analytical results previously obtained for general mobile wireless networks are tailored to infostation systems deployed in rural areas. Such derivations have been utilized to gain insight into the design of energy-efficient protocols for the above application scenario.

A trade-off between energy consumption reduction and responsiveness in information delivery for delay-tolerant sensor networks with mobile sink

In a delay-tolerant sensor network where the sink is mobile, a node can conveniently hold an information packet until the sink comes closer. This allows to both decrease the number of wireless hops required to deliver the information to the sink and reduce energy consumption. Thus, mobility of nodes can be exploited to increase energy efficiency in sensor networks. However, a major drawback of the above policy is that it causes delay which may be not acceptable for the application. In this paper a trade-off between energy efficiency and delay is investigated. More specifically, an analytical framework which allows to evaluate the expected delivery cost with respect to the maximum delay acceptable for the application is derived and assessed by comparison with simulation results. Numerical results show that the analytical framework is very accurate and, as expected, accuracy increases as the density of nodes in the network increases.