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Cross layer analysis of interference effects in wireless systems
Full text linkWireless communication systems are nowadays employed in many fields. The research effort beneath this work is to investigate one of the main issues in a radio communication system: interference. Devices operating in the 2.4 GHz unlicensed Industrial, Scientific and Medical (ISM) band are considered and, in particular, wireless sensors networks compliant to IEEE 802.15.4 standard are used to evaluate performance indices in the presence of interference.
The analysis starts from a real wireless control application and a RF power meter application: a complete perspective involving theoretical formulas, simulations and experimental results is given. A cross layer approach for CSMA/CA based devices, merging interference effects at PHY and MAC layer, is presented.
Subsequently effects of interference on channel status evaluation and RSSI circuitry are faced and, finally, the feasibility of a low cost RF power meter is discussed.
The purpose of the work is to understand interference phenomena, using a real life test bed and a complex set of interferers comprising both arbitrary signal generators and real wireless networks. The interaction of interference with a device is manifold: it involves physical layer, hardware and protocols.
The final aim of this work is to provide protocol and hardware designers with a set of performance metrics and perspectives useful to improve wireless devices’ behavior against interference.Oggigiorno i sistemi di comunicazione wireless hanno un impiego assai vasto. Questo lavoro di ricerca si propone di investigare una delle maggiori problematiche per una comunicazione radio: l’interferenza. Vengono considerati alcuni dispositivi operanti nella banda libera ISM a 2.4 GHz e, in particolare, vengono utilizzate reti di sensori wireless aderenti allo standard IEEE 802.15.4 per la valutazione di indici di prestazioni in presenza di interferenza. L’analisi parte da un’applicazione di controllo wireless e da una applicazione per la misura della potenza a radiofrequenza. Viene di seguito presentato, per i dispositivi basati su CSMA/CA, un approccio cross-layer per un’analisi congiunta degli effetti delle interferenze a livello PHY e a livello MAC. Di seguito vengono affrontati gli effetti dell’interferenza sulla valutazione dell’occupazione di canale e sulla circuiteria di RSSI e, infine, viene discussa la fattibilità di un misuratore di potenza RF a basso costo. Lo scopo della tesi è comprendere i fenomeni d’interferenza utilizzando un test bed reale e un complesso sistema di interferenze sia provenienti da generatori di segnale sia da reti wireless reali. L’interazione dell’interferenza con un dato dispositivo è molteplice: coinvolge il livello fisico, l’hardware e i protocolli. L’obiettivo finale è fornire ai progettisti dell’hardware e dei protocolli un insieme di metriche di prestazione e prospettive utili a migliorare il comportamento dei sistemi wireless contro l’interferenza
Experimental optimization of cca thresholds in wireless sensor networks in thepresence of interference
No full textPerformance of Carrier Sense Multiple
Access with Collision Avoidance (CSMA/CA)
protocol implemented on a Wireless Sensor Network
(WSN) in the presence of interference are here
investigated. In particular, attention is focused on the
Clear Channel Assessment (CCA) method, and on the
choice of CCA threshold. The purpose of the work is
to provide helpful information and hints for designers
to be considered and applied in order to optimize the
use of CCA algorithm and the setup of CCA threshold,
in the presence of in-channel additive white gaussian
noise interference. To this goal, a number of
meaningful experiments is conducted, through a
suitable testbed and measurements executed both at
physical and medium access control layer
Analizzatore di spettro su architettura PXI per analisi di segnali wireless e delle telecomunicazioni
No full textL’analizzatore di spettro (AS) è tra gli strumenti di misura e diagnostica maggiormente utilizzati per
analisi di segnali wirelss e delle telecomunicazioni, ad esempio nella banda industrial scentifical and
medical (ISM) a 2.4 GHz. Oggetto di questo lavoro è un AS ibrido realizzato sfruttando la
piattaforma modulare PXI National Instruments: si tratta di uno strumento virtuale che copre la banda
da 9 kHz e 2.7 GHz
Experimental characterization of wireless sensor networks for industrial applications
No full textThe 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
Modeling the performance of CSMA-CA based wireless networks versus interference level
No full textWireless 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 inchannel
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
Analisi simulativa della disposizione a minimo impatto elettromagnetico ambientale di una rete cellulare
No full textIn questo lavoro, si riportano alcuni risultati di uno studio simulativo volto a evidenziare caratteristiche,
vantaggi e svantaggi ottenuti nel suddividere una cella a copertura UMTS in sette microcelle a
minore raggio e intensità di campo EM emesso. Si considerano in particolare i seguenti fattori: livelli
di potenza emessi dalle SRB, livelli di campo EM ambientale dovuti alla SRB, livelli di potenza emessi
dai terminali mobili
Effects of RSSI Impairments on IEEE 802.15.4 Wireless Devices Performance Susceptibility to Interference
No full textThe effects of interference on IEEE 802.15.4
devices performance are here dealt with, with special regard
to the role played by the signal strength indication (RSSI)
meter embedded in each device. In particular, attention is
paid to some typical RSSI meter impairments, and on their
effect on the device susceptibility to external interference.
To the purpose, measurements are conducted on a purposely
developed testbed enlisting a real IEEE 802.15.4 device. The
aim of the work is to gain from experiments helpful notes
for network designers showing how RSSI impairments may
influence the performance of a IEEE 802.15.4 wireless sensor
network in the presence of interference. In the experiments,
single tone signals and additive white Gaussian noise are used
as interferers
Experimental comparison of spectrum analyzer architectures in the diagnosis of RF interference phenomena
No full textInterference and coexistence issues among devices
deploying wireless communications are becoming more and more
intrusive. The analysis of such phenomena can be carried out employing
high frequency Spectrum Analyzers (SA). In this paper,
performances of the main architectures of SA are experimentally
analyzed and compared, in order to obtain helpful hints to choice
the most suitable instrument for diagnosis purposes
Challenges and design issues in a wireless measurement scenario
No full textIn the last few years wireless sensor networks (WSNs) have gained an increasing
interest in the scientific community, due to their wide variety of applications and
technical issues to be faced. Many challenges and design issues arise in this
Ad-Hoc scenario. In this paper, some concepts are discussed having in mind
a twofold point of view: the telecommunication researcher or GRID designer
perspective, and the metrologist or instrumentation and measurement designer
one. Such mixed view allows pointing out aspects that are somewhat seldom
considered, and that instead could provide interesting results in both the above
research areas
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