The Ricean probability density function (pdf) is widely used to estimate the electromagnetic field distribution in indoor environments. The goal of using the Ricean or other pdfs is to evade the computational cost of deterministic field calculation. The parameters of the pdfs are usually obtained using the maximum-likelihood estimation which is here shown to fail in local areas close to the antenna where the direct field varies significantly. This paper presents the new localized maximum likelihood method which is valid in close regions as well. Moreover, the maximum-likelihood method requires a large number of field values within the local area to yield the parameters of the pdf. This paper presents the ray-tracing maximum-likelihood (RTML) method where a much lower number of field values are required. These values are determined using ray-tracing and without the need to account for the computationally expensive higher-order reflections. The RTML fails in local areas close to the antenna, and thus the new localized RTML is presented to restore accuracy.
2. Babich, F. and G. Lombardi, "Statistical analysis and characterization of the indoor propagation channel," IEEE Transactions on Communications, Vol. 48, No. 3, 455-464, Mar. 2000.
3. Hashemi, H., "The indoor radio propagation channel," Proceedings of the IEEE, Vol. 81, No. 7, 943-968, Jul. 1993.
4. Ardavan, M., EMI risk assessment in a hospital ward with roaming wireless transmitters, Ph.D. thesis, Concordia University, 2014.
5. Ardavan, M., C. W. Trueman, and K. Schmitt, "A sabine-rice approximation for the risk of exceeding immunity," 2011 IEEE International Symposium on Antennas and Propagation (APSURSI), 2363-2366, Jul. 3–8, 2011.
6. Ardavan, M., C. W. Trueman, and K. Schmitt, "Ricean and rayleigh probability distribution functions for estimating field distributions in indoor propagation," 27th Annual Review of Progress in Applied Computational Electromagnetics (ACES), 980-985, Williamsburg, Virginia, Mar. 2011.
7. Sijbers, J., A. J. den Dekker, P. Scheunders, and D. van Dyck, "Maximum-likelihood estimation of Rician distribution parameters," IEEE Transactions on Medical Imaging, Vol. 17, No. 3, 357-361, Jun. 1998.
8. Greenstein, L. J., D. G. Michelson, and V. Erceg, "Moment-method estimation of the Ricean K-factor," IEEE Communications Letters, Vol. 3, No. 6, 175-176, Jun. 1999.
9. Trueman, C. W., R. Paknys, J. Zhao, D. Davis, and B. Segal, "Ray tracing algorithm for indoor propagation," ACES 16th Annual Review of Progress in Applied Computational Electromagnetics, 493-500, Monterey, California, Mar. 20–24, 2000.
10. Goldsmith, A., Wireless Communications, Cambridge University Press, 2005.
11. Balanis, C. A., Advanced Engineering Electromagnetics, John Wiley & Sons, 1999.
12. Medawar, S., P. Handel, and P. Zetterberg, "Approximate maximum likelihood estimation of Rician K-factor and investigation of urban wireless measurements," IEEE Transactions on Wireless Communications, Vol. 12, No. 6, 2545-2555, Jun. 2013.