Measurement Interval and Offset (802.11a/g/j/p OFDM)

The Measurement Interval and Measurement Offset parameters specify an interval or section of the OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. burst within the Result Length that is used as the measurement analysis data. Measurement Interval specifies the time interval of data and measurement offset specifies the time offset of the start of the measurement interval.

Measurement Interval:	Specifies the amount of data (in symbols) within the Result Length time data that is included in the measurement analysis data. Measurement Interval is specified in symbols. The Time trace shows the Measurement Interval data.
Measurement Offset:	Measurement Offset specifies the start position of the Measurement Interval with respect to first symbol within the Result Length. Measurement Offset is specified in symbols.

Measurement Interval and Measurement Offset parameters allow you to quickly analyze and view different sections of the OFDM burst because the VSA does not acquire new measurement data when the Measurement Interval/Offset is changed. When a new Measurement Interval or Measurement Offset is entered, the VSA re-computes the trace data results using the existing measurement data.

The maximum Measurement Interval is limited to the maximum Result Length which is dependant upon the specified Result Length mode: Automatic or Manual mode, see Result Length. In Automatic mode the sum of the Measurement Interval and Offset are limited to the measurement burst length. In "Manual" mode, the Measurement Interval can extend and include data beyond the measurement burst, see below.

The sum of the Measurement Interval plus Measurement Offset must fit within the measurement Result Length.

The Time trace display shows only time data for the symbols specified by Measurement Interval parameter, except when the Measurement Interval is equal to Maximum Result Length. In this case, the Time trace display also shows the preamble data. See Time trace data for complete details.

Result Length: Total number of symbols included in the acquired and demodulated data.
Measurement Interval: Determines what segment of the Result Length data is analyzed and displayed.
Measurement Offset: Sets the start position of the Measurement Interval within the Result Length.
Symbol-time: One OFDM symbol period which includes the IFFT Inverse Fast Fourier Transform/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. period (TFFT) and guard interval period (TGI Guard interval).