1. A Stochastically Resonant Ontologically Based Cognitive
Radio for TV White Space Communications
Shastri Jayram, Khmaies Ouahada, Suvendi Rimer, Fisseha Mekuria (CSIR)
Department of Electrical and Electronic Engineering Science
University of Johannesburg, South Africa
shastri@itisy.co.za
Abstract—Research, Design and Development of a
Stochastically Resonant Ontologically Based Cognitive Radio
(SROBCR) for TV White Space Communications at the
University of Johannesburg, South Africa.
Keywords—cognitive radio; software defined radio; ontological
radio; digital signal processing; stochastic resonance; interference
[mitigation management]; noise; SINAD; RF; dynamic spectrum
[sensing sharing utilization management]; [tv] white space;
I. WIRELESS GROWTH & INTERFERENCE
Considering the phenomenal growth and extensive use of
wireless systems today, two things captivate. First, interference
is increasing, which raises the apparent Noise Floor and
consumes limited Radio Resources. Second, the concepts of
opportunistic or Dynamic Spectrum Sharing, Access and
Management (DSSH/DSA/DSM) and concomitant Cognitive
Radios (CR) are gaining ground. One practical deployment of
CR abounds in TV White Space Communications, although
CR capabilities need not be band limited and can be
technologically agnostic such as in system, coding, modulation,
channel, multiplexing, access, protocol, network, route, stream,
payload, etc. at Base Band, Intermediate or Radio Frequencies.
II. THE SROBCR
Inherent in CR is the exploitation of modern Computing or
Machine Intelligence and Digital Signal Processing (DSP) to
give Software Defined Radios (SDR) Cognitive i.e. “analytic
learning, thinking and reasoning” capabilities, [1]. In [1], the
author also specifies a necessary radio ‘ontology’ in order to,
effectively; incorporate “intelligence” in a radio. Such a
SDR/CR has intriguing applications beyond just TV White
Space Spectrum e.g. agnostic (as above), and, dynamic and
autonomous adaptation, control and optimisation in real-time;
one supposes it is presumably what all intelli-radios aspire to.
Intrinsic to Interference (or Interference Temperature) are
Noise and Distortion, which are further forked and bifurcated
into Wanted (Carrier/Signal/S) and Unwanted Signals (Others,
Interference, Noise And Distortion/INAD), i.e. SINAD Ratio.
Noise, “being noise”, is usually considered “bad”. However,
Stochastic Resonance (SR), [2][3], the ability to ‘enhance
Signal-to-Noise Ratios by adding noise’ instead of removing it
as is usually and counter-intuitively the case, allows for the
Detection of Signals below normal Detection Threshold Limits.
This ability is useful in applications where there is Spectrum
Sensing of real Radio Environments and Dynamic Utilization
of Spectrum, where accurate SINAD Ratios are critical.
Thus, this research seeks to explore, understand and apply
this knowledge towards designing and developing a SROBCR
for TV White Space Communications.
III. OUTLINE OF IMPLEMENTATION
We employ Open Source GNU Radio/USRP as the
RF/SDR Interface and are architecting a custom Linux
SROBCR Test Bed comprising of various subsystems,
programs, software, hardware, tools, utilities and instruments.
In order to instill Ontological capabilities, we employ OWL
(Web Ontology Language), to develop an appropriate OBCR
Engine. The OBCR Engine is fundamentally “meta” and has to
manipulate Software Objects via Management and Control
Planes. We need to model and simulate the RF Environment in
Software; then compare it to Sensed Real Systems, and with
Feedback, achieve some level of Specified Performance or
Optimization. Processing and reaction time are critical.
This requires a functional Dynamic Spectrum Sensing module
(Physical Layer upwards including CR Management & Control
Planes) which by design uses SR to enhance Detected SINAD
Ratios of all Signals, whether Wanted, Unwanted, Interference
or Noise. Additionally, it is necessary to include Interference
Mitigation mechanisms incorporating Primary User Detection
and Other Peer White Space Opportunistic Secondary Users
whilst dynamically managing spectrum to best-fit User
Requirements in Real-Time. Essentially, a CR has to
Dynamically Sense, Detect and Classify constantly varying
Signals, and through pre-programmed and eventually self-
learned CR responses and active Interference Management,
enable DSSH/DSA/DSM and efficient spectrum utilization.
Our initial investigations employ SEAMCAT to model, test
and simulate various TV White Space systems under different
scenarios on a High Performance Machine. Currently, we are
conceiving an OBCR Engine using Protégé, establishing the
GNU Radio and USRP SDR/RF interfaces and charting the
SR, Interference Management, DSSH/DSA/DSM modules.
REFERENCES
[1] J. Mitola III, “Cognitive Radio, An Integrated Agent Architecture for
Software Defined Radio,” Dissertation submitted in partial fulfilment of
the degree of Doctor of Technology, Royal Institute of Technology
(KTH), Teleinformatics, Sweden, 8 May 2000, ISSN 1403-5286, ISRN
KTH/IT/AVH—00/01—SE.
[2] R. Benzi, A. Sutera, and A. Vulpiani, “The mechanism of stochastic
resonance,” J. Phys. A, vol. 14, no. 11, pp. L453–L457, 1981.
[3] B. Kosko, “Noise,” New York, NY, Viking, 2006, ISBN 0-670-03495-9.