Alessandro Sona

Experimental Study of Coexistence Issues Between IEEE 802.11b and IEEE 802.15.4 Wireless Networks

Coexistence issues between IEEE 802.11b wireless communication networks and IEEE 802.15.4 wireless sensor networks, operating over the 2.4-GHz industrial, scientific, and medical band, are assessed. In particular, meaningful experiments that are performed through a suitable testbed are presented. Such experiments involve both the physical layer, through measurements of channel power and the SIR, and the network/transport layer, by means of packet loss ratio estimations. Different configurations of the testbed are considered; major characteristics, such as the packet rate, the packet size, the SIR, and the network topology, are varied. The purpose of this paper is to gain helpful information and hints to efficiently face coexistence problems between such networks and optimize their setup in some real-life conditions. Details concerning the testbed, the measurement procedure, and the performed experiments are provided.

Experimental Characterization of Wireless Sensor Networks for Industrial Applications

The effects of interference in the setup of wireless sensor networks (WSNs) represent a critical issue, and as such, it needs to be carefully addressed. To this aim, helpful information can be achieved through measurements to be carried out in advance on suitable prototypes and testbeds. In this paper, the measurement of industrial WSN performance is dealt with. In particular, a suitable testbed enlisting IEEE 802.15.4 wireless sensor nodes is presented along with the results of some experiments carried out even in the presence of interference. The purpose is to show how to evaluate some specific parameters of a WSN employed for industrial applications to obtain useful information for its setup optimization in the presence of interference. The analysis will show that from the measurement of these parameters (number of failed pollings, polling round-trip time, experimental cycle time, and alarm latency), interference effects can effectively be recognized, and the network setup can be optimized.

Is CSMA/CA really efficient against interference in a wireless control system? An experimental answer

The deployment of a wireless control system must cope with a number of effects usually negligible in a wired scenario. To this aim, an experimental analysis on suitable prototypes and testbeds can readably offer a valid and rapid method to forecast the behavior of a real network. In this paper, performance measurement of industrial wireless sensor network in the presence of various type of interference is provided. In particular a Bluetooth, WiFi and Zigbee disturbing network impairs a suitable testbed employing IEEE 802.15.4 wireless sensor nodes. The purpose is to optimize the effectiveness of the medium access control mechanism through the choice of a proper mode of use. The analysis will show that from the measurement of certain parameters (number of failed pollings, experimental cycle-time, and alarm latency) interference effects can be effectively recognized and the network setup optimized.

Assessing coexistence problems of IEEE 802.11b and IEEE 802.15.4 wireless networks through cross-layer measurements

Coexistence issues between IEEE 802.11b (Wi-Fi) wireless communication networks and IEEE 802.15.4 wireless sensor networks (WSN), operating within the same 2.4 GHz ISM-band, are hereinafter assessed. In particular, meaningful experiments performed through a suitable testbed and a cross-layer measurement approach are presented. Such experiments are executed both at physical layer, through measurements of channel power and signal-to-interference ratio (SIR), and at network/transport layer, by means of packet loss ratio estimations. Different testbed configurations are analyzed, varying characteristics like packet rate, packet size, SIR, network topology and number of wireless nodes. The purpose of the work is to deduce from experiments practical information and guidelines showing how optimizing networks setup and mitigating coexistence problems in some real-life configurations. Practical details about testbed, test environment and performed experiments are provided in the paper.

Experimental Evaluation of an Industrial Application Layer Protocol Over Wireless Systems

Several recent studies have addressed the suitability of current wireless technologies for industrial communications which, frequently, are requested to cope with severe timing constraints. Most of the analysis that have lately appeared in the literature have focused on the performance offered by the lower layers of the communication stack. However, in order to obtain a complete picture, it is important to analyze how this gets coupled with the features of higher layer protocols typically employed by industrial communication applications. In this paper, we investigate the performance obtained by an application layer protocol, derived from those currently employed by wired fieldbuses, running over COTS devices based on two popular wireless communication standards, namely, IEEE 802.15.4 and IEEE 802.11. In particular, we present a mapping of the application service elements onto the services offered by the mentioned wireless systems and discuss some possible design choices. A prototype of the application layer protocol is then implemented for each considered wireless technology and the performance figures evaluated by means of experimental measurements.

Assessment of Out-of-Channel Interference Effects on IEEE 802.15.4 Wireless Sensor Networks

The impact of out-of-channel interference on IEEE 802.15.4 wireless sensor networks (WSNs) performance is here dealt with. In particular, the effect on networks based on the carrier sense multiple access with collision avoidance (CSMA/CA) protocol is investigated. To this aim, a theoretical analysis of the problem is outlined, and results from both simulations and experiments are provided. Measurements are performed both at physical layer, through parameters like in-channel power, and at network layer, through packet error ratio estimates. The purpose is to provide from simulations and experiments a set of helpful information and hints to be used for an efficient measurement and troubleshoot of interference problems caused on IEEE 802.15.4 WSNs by out-of-band signals.

Investigating wireless networks coexistence issues through an interference aware simulator

In the modern wireless applications of factory automation, interference phenomena among near operating wireless networks can be the cause of severe performance degradation. To avoid this possibility and prevent deleterious system failures, simulations may offer a real and reliable solution. In this paper a new simulator is presented, allowing cross-layer analysis of interference phenomena arising among IEEE 802.15.4 wireless sensor networks (WSNs) and IEEE 802.11 wireless local area networks. The purpose is to provide an accurate tool able to forecast possible interference effects on a WSN and by which optimize the setup of some suitable network parameters such as the position of wireless nodes.

Modeling the Performance of CSMA-CA Based Wireless Networks Versus Interference Level

Wireless communication networks based on non-scheduled random medium access methods, such as carrier sense multiple access with collision avoidance (CSMA/CA), can be affected by in- channel interference at two different levels: at physical (PHY) layer, in terms of data packet collisions, and at medium access control (MAC) layer, in terms of channel occupation. The separate knowledge of such interference effects may represent an essential information to be used in a design or setup stage of CSMA/CA-based wireless networks. To this aim, a simple yet effective two-layer model is proposed in the paper. The model allows to clearly distinguish the effect of both interference contributions and to forecast the network performance in terms of packet error ratio, in the presence of interference. An example of how to use the model, and results from experiments, validating the model, are both reported. The experiments have been conducted through a suitable testbed enlisting a IEEE 802.15.4-compliant wireless sensor network.

Experimental analysis of UHF RFID impairments and performance

Radio frequency identification (RFID) is a modern wireless communication technology used for identification purposes. By now, experimental results showing the actual performances reachable by a UHF RFID system, are still missing, together with the problems that can be encountered in practice and the corresponding solutions. In this paper, the performance of an UHF RFID system in real-world conditions are experimentally assessed to experimentally investigate the reliability of UHF RFID systems typical environmental conditions; and to deduce helpful and practical hints in order to efficiently assess and enhance performances of an UHF RFID system.

On the power measurement via a spectrum analyzer

This paper discusses the accuracy of spectrum analyzers when used for power measurements. Zero-span analysis and power-density techniques are theoretically modeled for greater generality. Experimental tests are discussed in order to verify the provided analysis. Moreover, practical hints for the optimization of accuracy and measurement time are reported.