## Documentation Center |

`dop = doppler.roundeddop = 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.

Property | Description |
---|---|

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 [1]. 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:

where

is the maximum Doppler shift, and are real finite coefficients. The fixed wireless channel model of IEEE 802.16 [1] 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;

[1] IEEE 802.16 Broadband Wireless Access
Working Group, "Channel models for fixed wireless applications," * IEEE
802.16a-03/01*, 2003-06-27.

`doppler` | `doppler.ajakes` | `doppler.bell` | `doppler.bigaussian` | `doppler.flat` | `doppler.gaussian` | `doppler.jakes` | `doppler.rjakes` | `rayleighchan` | `ricianchan` | `stdchan`

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