Nominal Bandwidth (802.16 OFDMA)

Default: 10 MHz Megahertz: A unit of frequency equal to one million hertz or cycles per second. (See OFDMA Standard Presets Table.)

Range: Hardware dependent

The Nominal Bandwidth parameter specifies the nominal channel bandwidth.

Nominal Bandwidth is only available when the Restrict bandwidth to standard values check box is selected on the Advanced tab.

When the Nominal Bandwidthis set, the FFT Fast Fourier Transform: A mathematical operation performed on a time-domain signal to yield the individual spectral components that constitute the signal. See Spectrum. Length and Bandwidth Ratio are coupled to standard compliant values:

Nominal Bandwidth	FFT size	Bandwidth Ratio
1.25 MHz	128	28/25
3.5 MHz	512	8/7
4.375 MHz	512	28/25
5 MHz	512	28/25
7 MHz	512	8/7
8.75 MHz	1024	8/7
10 MHz	1024	28/25
14 MHz	1024	8/7
15 MHz	2048	28/25
17.5 MHz	2048	8/7
20 MHz	2048	28/25
28 MHz	2048	8/7

When Standard is selected, the Bandwidth Ratio will be set to 8/7 for all values.

OFDMA supports a scalable frame structure where the FFT size scales with bandwidth to keep the subcarrier spacing fixed. The OFDMA standard specifies four FFT "NFFT"sizes" (128, 512, 1024 and 2048) and many nominal bandwidths respectively.

How the VSA determines Nominal Bandwidth

The IEEE Institute of Electrical and Electronics Engineers. A US-based membership organisation that includes engineers, scientists, and students in electronics and related fields. The IEEE developed the 802 series wired and wireless LAN standards. Visit the IEEE at http://www.ieee.org 802.16-2004 standard defines the Sampling Frequency(Fs) as:

Fs = floor(BWRatio*BW/8000)*8000

This is the sample rate for a non-oversampled OFDMA signal.

This equation restricts the sampling frequency to 8 kHz kiloHertz: A radio frequency measurement (one kilohertz = one thousand cycles per second). increments. To facilitate R&D development and debug-mode analysis of an OFDMA DUT Device under Test: An acronym used to describe some type of electrical apparatus connected to test instrumentation. The apparatus can range from a single component to a complex subsystem such as a mobile phone, base station or MSC., the VSA allows arbitrary Sampling Frequency. To implement this capability, the VSA does not use the "floor" function to compute the Sampling Frequency, but instead uses the following formula:

Nominal BW (analyzer) = Fs / BWRatio

For example, if a profile for an 802.16e OFDMA signal specifies a Nominal BW value of 10 MHz and a BW Ratio of 8/7, the Sampling Frequency is computed as:

Fs = floor(8/7 * 10e6 / 8000)*8000 = 11.424 MHz

And the corresponding VSA Nominal BW value is:

Nominal BW (analyzer) = 11.424 MHz / (8/7) = 9.996 MHz