1. The University of Texas at Austin
Preliminary Results
Mitigating Computer Platform Radio Frequency Interference in Embedded Wireless Transceivers
Prof. Brian L. Evans
The University of Texas at Austin
October 17, 2007

2. Computer Platform RFI Clocks, clock harmonics, and busses generate RFI
Impulsive in nature (non-Gaussian)
Reduces communication performance for embedded wireless data transceivers
Goals
Improve communication performance in presence of computer platform RFI
Develop offline and online algorithms
Approaches
Statistical modeling of RFI
Filtering/detection using estimation of statistical model parameters
We’ll be using “interference” and “noise” interchangeably in this talk.

3. Statistical Models Middleton Class A Symmetric Alpha Stable
Power Spectral Density
Power Spectral Density
with A = 0.15 and G = 0.1
with a = 1.5, d = 0 and g = 10

4. Middleton Class A Noise
Communication Performance
Class A Parameters A = 0.35 G = 0.5 × 10-3

5. Symmetric Alpha Stable Noise
Communication Performance
SαS Parameters α = 1.5 δ = 0 γ = 1

6. Symmetric Alpha Stable Noise
80,000 data samples collected using 20 GSPS scope
Parameter Estimation
Localization (δ)
Dispersion (γ)
0.5833
Characteristic Exponent (α)
1.5525
fX(x) - PDF
Normalized MSE
x – noise amplitude

7. Conclusion
Modeling computer platform RFI using impulse noise models promising
Middleton Class A: 25 dB gain for BER 10-2
Symmetric Alpha Stable: 5 dB gain for BER 10-1
Tractable parameter estimation algorithms
Middleton Class A: iterative + polynomial rooting
Symmetric Alpha Stable: non-iterative
UT Austin RFI Mitigation Toolbox
Research began January 2007: more to come!

8. References
D. Middleton, “Non-Gaussian noise models in signal processing for telecommunications: New methods and results for Class A and Class B noise models”, IEEE Trans. Info. Theory, vol. 45, no. 4, pp , May 1999.
S. M. Zabin and H. V. Poor, “Efficient estimation of Class A noise parameters via the EM algorithms”, IEEE Trans. Info. Theory, vol. 37, no. 1, pp , Jan
G. A. Tsihrintzis and C. L. Nikias, "Fast estimation of the parameters of alpha-stable impulsive interference", IEEE Trans. Signal Proc., vol. 44, Issue 6, pp , Jun
A. Spaulding and D. Middleton, “Optimum Reception in an Impulsive Interference Environment-Part I: Coherent Detection”, IEEE Trans. Comm., vol. 25, no. 9, Sep
A. Spaulding and D. Middleton, “Optimum Reception in an Impulsive Interference Environment-Part II: Incoherent Detection”, IEEE Trans. Comm., vol. 25, no. 9, Sep
B. Widrow et al., “Principles and Applications”, Proc. of the IEEE, vol. 63, no.12, Sep
J. G. Gonzalez and G. R. Arce, “Optimality of the Myriad Filter in Practical Impulsive-Noise Environments”, IEEE Transactions on Signal Processing, vol 49, no. 2, Feb