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Author:Ben Cheikh, Sami
Title:Design of an Adaptive Frequency Hopping Algorithm Based On Probabilistic Channel Usage
Publication type:Master's thesis
Publication year:2011
Pages:[8] + 65      Language:   eng
Department/School:Tietoliikenne- ja tietoverkkotekniikan laitos
Main subject:Tietoliikennetekniikka   (S-72)
Supervisor:Jäntti, Riku
Instructor:Hellbrück, Horst
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201207022743
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  676   | Archive
Keywords:adaptive frequency hopping
coexistence in the ISM band
probabilistic channel usage
interference mitigation
exponential smoothing filter
WPAN
LR-WPAN
WLAN
Abstract (eng): Dealing with interference in the 2.4 GHz ISM band is of paramount importance due to an increase in the number of operating devices.
For instance systems based on Bluetooth low energy technology are gaining lots of momentum due to their small size, reasonable cost and very low power consumptions.
Thus the 2.4 GHz ISM band is becoming very hostile.

Bluetooth specification enables the use of adaptive frequency hopping to improve performance in the presence of interference.
This technique avoids the congested portions of the ISM band, however as the number of interferers increases for a given geographical environment, a greater number of bad channels are removed from the adapted hopping sequence.
This results in longer channel occupancy, and consequently higher probability of collisions with coexisting devices, degrading their operation.

At CoSa Research Group a novel algorithm, based on probabilistic channel usage of all channels (good and bad), is developed.
The scheme is named Smooth Adaptive Frequency Hopping (SAFH) and uses an exponential smoothing filter to predict the conditions of the radio spectrum.
Based on the predicted values, different usage probabilities are assigned to the channels, such as good channels are used more often than bad ones.
The discrete probability distribution generated is then mapped to a set of frequencies, used for hopping.

MATLAB/SIMULINK was used to investigate the performance of SAFH, in the presence of different types of interfering devices such as 802.11b , 802.15.4 and 802.15.1.
Simulation study under different scenarios show, that our developed algorithm outperforms the conventional random frequency hopping as well as other adaptive hopping schemes.
SAFH achieves lower average frame error rate and responds fast to changes in the channel conditions.
Moreover it experiences smooth operation due to the exponential smoothing filter.
ED:2012-01-30
INSSI record number: 43879
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