Performance analysis for industrial wireless networks
Author
Zdravković, Nemanja M.
Mentor
Kansanen, KimmoCommittee members
Chatzigeorgiou, IoannisPetersen, Stig
Milović, Daniela

Čiča, Zoran

Metadata
Show full item recordAbstract
Industrial wireless networks operate in harsher and noisier environments compared to
traditional wireless networks, while demanding high reliability and low latency. These
requirements, combined with the constant need for better coverage, higher data rates
and overall seamless user experience call for a paradigm shift in communication in regards
to the previous generations of technologies used. Cooperative diversity is one such
approach.
The main focus of this thesis is on the performance analysis of cooperative wireless
networks set in industrial environments – where the network, apart from additive white
Gaussian noise, is subject to multipath fading and shadowing, and/or temporary random
blockage effects. In these scenarios, in order to achieve specific performance metrics
such as error rates or outage probabilities, existing cooperative strategies are aided by
protocols in the channel between the cooperating nodes. Moreover, pair-wise analysis
investigates the correlati...on of multiple data flows.
Building upon existing repetition protocols, outage performance of a network subject
to fading and shadowing is observed, and the effects of fading and shadowing severity,
network dimension, average signal-to-noise ratio values and packet length are discussed.
Special cases are also observed, in which the composite fading channel is reduced to
several familiar propagation environments, unifying the analysis.
Afterwards, the analysis of more complex protocols is presented, taking into account
random blockage in the channels between cooperating nodes. A novel, threshold-based
internode protocol is introduced, which improves performance by listening to the transmissions
and choosing whether to send a packet immediately or after a waiting period.
As these two periods are close, the effect of temporal correlation is also investigated.
Apart from the exact outage probability expressions, simpler asymptotic expressions,
with and without blockage, are derived as well, giving a better insight on the network
behaviour at high average signal-to-noise ratio regimes.
Both outage probability and packet error rate can be also improved by adding automatic
repeat request schemes in the channel between cooperating nodes, which again
utilize the internode channels by re-sending data until it can be successfully decoded.
Error-free communication can be achieved, but at a delay cost. Nevertheless, a trade-off
between performance gains and delays remains, and can therefore be used for designing
wireless networks with different requirements – error-free or low-latency.
Finally, joint outage performance is investigated. Using a generic approach, which
can be applied to any sort of data where multiple sources are communicating over wireless
networks, pair-wise behaviour is investigated. As a result, any multi-route diversity
type of scheme will have this sort of behaviour, since particular point-to-point relay links
are being shared by source nodes. This in turn means that the performance of those
flows will be correlated. For higher layers, there is a difference in the behaviour, meaning
that when errors are correlated, data flows start behaving correlated as well. As a
result, negative acknowledgements may start to correlate as well. All of this contributes
to the network behaving in a correlated way, i.e., when something happens, it tends to
happen to more than one data flow.