Construct rounded Doppler spectrum object
dop = doppler.rounded
dop = doppler.rounded(coeffrounded)
The doppler.rounded function creates a rounded Doppler spectrum object that is used for the DopplerSpectrum property of a channel object (created with either the rayleighchan or the ricianchan function).
dop = doppler.rounded creates a rounded Doppler spectrum object with default polynomial coefficients , , (see Theory and Applications for the meaning of these coefficients). The maximum Doppler shift (in Hertz) is specified by the MaxDopplerShift property of the channel object.
dop = doppler.rounded(coeffrounded), where coeffrounded is a row vector of three finite real numbers, creates a rounded Doppler spectrum object with polynomial coefficients, , given by coeffrounded(1), coeffrounded(2), and coeffrounded(3), respectively.
The rounded Doppler spectrum object contains the following properties.
|SpectrumType||Fixed value, 'Rounded'|
|CoeffRounded||Vector of three polynomial coefficients (real finite numbers)|
A rounded spectrum is proposed as an approximation to the measured Doppler spectrum of the scatter component of fixed wireless channels at 2.5 GHz . However, the shape of the spectrum is influenced by the center carrier frequency.
The normalized rounded Doppler spectrum is given analytically by a polynomial in f of order four, where only the even powers of f are retained:
is the maximum Doppler shift, and are real finite coefficients. The fixed wireless channel model of IEEE 802.16  uses the following parameters: , , and . Because the channel is modeled as Rician fading with a fixed line-of-sight (LOS) component, a Dirac delta is also present in the Doppler spectrum at .
The following code creates a Rician channel object with a maximum Doppler shift of . It then creates a rounded Doppler spectrum object with polynomial coefficients , , , and assigns it to the DopplerSpectrum property of the channel object.
chan = ricianchan(1/1000,10,1); dop_rounded = doppler.rounded([1.0 -0.5 1.5]); chan.DopplerSpectrum = dop_rounded;
 IEEE 802.16 Broadband Wireless Access Working Group, "Channel models for fixed wireless applications," IEEE 802.16a-03/01, 2003-06-27.