Stefan Mijovic

Testing Protocols for the Internet of Things on the EuWIn Platform

Several approaches have been considered by research community as possible enablers for the Internet of Things (IoT) implementation. This paper presents the results obtained by testing and comparing three different solutions. In particular, we compare a centralized solution based on software defined network (SDN), called software defined wireless networking (SDWN), with two standard and distributed solutions, that are ZigBee and IPv6 over low-power wireless personal area networks (6LoWPAN). SDWN uses a centralized network layer protocol, where routing policies are defined by an external controller that can be positioned anywhere in the network. The other two solutions are actually the most common protocol stacks for wireless sensor networks, and they both use a distributed routing protocol. The comparison is achieved by experimentations performed on the European Laboratory of Wireless Communications for the Future Internet (EuWIn) platform developed within the network of excellence, NEWCOM#. Results show that SDWN is the best solution in static or quasi-static environments, while the performance degrades in highly dynamic conditions. However, ZigBee has a good reactivity to environmental changes. This paper reports the evaluation of several performance metrics, including packet loss rate, round-trip-time, and overhead generated in the network, under different conditions and considering different kinds of traffic.

Comparing application layer protocols for the Internet of Things via experimentation

In this paper we compare the performance of three application layer protocols, that are Constrained Application Protocol (CoAP), WebSocket and Message Queuing Telemetry Transport (MQTT), in an Internet of Things (IoT) scenario. The three protocols have been implemented on the same low cost and low complexity hardware platform, suitable for IoT applications. The performance, in terms of protocol efficiency, strictly related to the overhead, and average Round Trip Time (RTT), were experimentally evaluated. In the considered scenario an IoT device was transmitting data to a server and waiting for replies. IEEE 802.11.b/g/n air interface was used for the communication between the IoT device and an Access Point (AP), connected to the final server. Two different settings have been considered: a local area network (LAN) configuration, where the AP and the server were in the same LAN; and a more realistic IoT configuration, where the AP was connected to a remote server via the Internet. Furthermore, in the IoT configuration, two types of Internet connection are considered: a connection established through a home router and another via cellular network. Results show that CoAP achieves the highest protocol efficiency and the lowest average RTT, closely followed by WebSocket. The performance of MQTT protocol strongly depend on the Quality of Service (QoS) profile. Changing the environment, from a LAN network to a realistic IoT scenario, does not significantly impact the protocol efficiency, but has a considerable influence on the average RTT, which increases by a factor of 2 or 3, depending on the protocol. Finally, we give some insights on the impact of routing through a cellular network on the system performance.

On the performance of 6LoWPAN through experimentation

The Internet of Things (IoT) research activities are oriented towards the standardisation of communication protocols and platforms for globally interconnected smart objects. 6LoWPAN is a standardised protocol stack aiming at providing the seamless interconnection between IPv6 Wireless Sensor Network (WSN) and Internet, while maintaining low-power consumption. In this paper, we present and investigate the performance of 6LoWPAN, being one of the most promising solutions for the implementation of IoT paradigm. The evaluation is performed through experimentation on the “European Laboratory of Wireless Communications for the Future Internet” (EuWIn) facilities developed within the Network of Excellence, NEWCOM#, at the University of Bologna. We report results in terms of average round-trip-time, packet loss rate and throughput for different payload sizes and number of hops, both for unicast and multicast traffics.

Experimental characterization of Low Power Listening in BAN

This paper presents an implementation of a Low Power Listening-based (LPL) Medium Access Control (MAC) protocol on a platform for Body Area Network (BAN) applications. LPL exploits the transmission of a burst of short packets, called preambles, to synchronize the transmitter and the receiver. In this way, devices are able to spend most of the time in sleeping mode, providing longer lifetime and energy saving. Experiments on the field have been conducted by considering different scenarios and results, in terms of average energy consumed per packet, packet loss rate and average delay, have been investigated. Conclusions regarding the proper parameters setting depending on the application requirements were derived. This work has been performed in the framework of the FP7 Integrated Project, WiserBAN.

Experimental characterisation of energy consumption in Body Area Networks

This paper addresses the issue of power consumption in the field of Wireless Body Area Networks (WBAN). It presents a methodology used to perform real-time measurements of the energy consumption of a deployed WBAN, and describes how to design Medium Access Control (MAC) protocols, able to satisfy different application requirements in terms of lifetime, but also of latency. More precisely we analyse the performance of two MAC protocols, one based on low power listening and the other one based on the IEEE 802.15.6 standard, and we discuss their applicability to two specific scenarios. The evaluation is performed through experiments carried out on a hardware platform intended for WBANs, while the application scenarios are inspired by those defined in the FP7 EC Project, WiserBAN. Results obtained allow us to draw conclusions and considerations regarding energy consumption in realistic scenarios and provide significant inputs to WBAN designers.

Optimal design of energy-efficient cooperative WSNs: How many sensors are needed?

In this paper, a cooperative Multiple-Input-Multiple-Output (MIMO) scheme for wireless sensor networks is presented. We consider a network which consists of inexpensive sensor nodes transmitting data towards sinks. We take into account the hardware limitations this kind of devices typically present. Having in mind potentially high number of nodes in the network, we study the asymptotic regime, inspired by recent developments in the massive MIMO field, which simplifies the performance analysis and is shown to be sound even for relatively low number of nodes. The aim is to provide the optimal number of sensor nodes to be deployed and the duration of the channel estimation phase, having in mind energy efficiency as performance metric.

A Cooperative Beamforming Technique for Body Area Networks

Abstract We consider an indoor environment with multiple Body Area Networks (BANs) that have to transmit data towards specific sinks, located in fixed positions. Nodes deployed on the same body may cooperate in order to form Virtual Antenna Arrays (VAAs) and transmit data towards one of the available sinks. Sinks are also equipped with multiple antennas, such that a virtual Multiple Input Multiple Output (MIMO) channel is established. Beamforming is used as a cooperation technique on both transmitter and receiver sides. A simple technique, consisting of decimating the number of cooperating nodes in the VAA with the aim of reducing energy consumption as well as interference, is presented. Results show that the proposed technique improves the performance in terms of energy efficiency, and also in terms of block error rate when the system is interference-limited. Performance is evaluated by applying different well-known scheduling strategies.

On the optimum number of cooperating nodes in interfered cluster-based sensor networks

This paper presents a cooperative multiple-input multiple-output (MIMO) scheme for a wireless sensor network consisting of inexpensive nodes, organised in clusters and transmitting data towards sinks. The transmission is affected by hardware imperfections, imperfect synchronisation, data correlation among nodes of the same cluster, channel estimation errors and interference among nodes of different clusters. Within this setting, we are interested in determining the number of nodes per cluster that maximises the energy efficiency of the network. The analysis is conducted in the asymptotic regime in which the number N of sensor nodes per cluster grows large without bound. Numerical results are used to validate the asymptotic analysis in the finite system regime and to investigate different configurations. It turns out that the optimum number of sensor nodes per cluster increases with the inter-cluster interference and with the number of sinks.

Low Power Listening in BAN: Experimental Characterisation

This paper presents an implementation of a Low Power Listening-based LPL Medium Access Control MAC protocol on a platform for Body Area Network BAN applications. LPL exploits the transmission of a burst of short packets, called preambles, to synchronize the transmitter and the receiver. In this way, devices are able to spend most of the time in sleeping mode, providing longer lifetime and energy saving. Experiments on the field have been conducted by considering different scenarios and results, in terms of average energy consumed per packet transmitted/received, packet loss rate, average delay and network throughput, have been investigated. Conclusions regarding the proper parameters setting depending on the application requirements were derived. This work has been performed in the framework of the FP7 Integrated Project, WiserBAN.