Guard Interval (802.16 OFDMA)

Default: 1/8 (See OFDMA Standard Presets Table.)

Range: 0 to 1

The Guard Interval specifies the current Guard Interval value, the default is 1/8. The Guard Interval - Other parameter allows you to specify a unique value, which is specified as a decimal fraction from 0 to 1. The VSA converts the decimal fraction to the equivalent rational fraction value. The OFDMA standard supports Guard Interval values of 1/32 (0.03125), 1/16 (0.0625), 1/8 (default), and 1/4 (0.25). When 0.125 (1/8) is specified, the VSA selects the default 1/8 radial button.

The Guard Interval is the ratio of the Cyclic Prefix (CP 1) Contention period, or 2) Cyclic prefix) time to the Inverse 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. time (T(IFFT Inverse Fast Fourier Transform)). The guard interval is used to eliminate inter-symbol and inter-carrier interference. A copy of the last guard interval T(GI Guard interval) of the useful symbol period T(IFFT), termed Cyclic Prefix (CP), is used to collect multipath, while maintaining the orthogonal relationship of the subcarriers. Each symbol is transmitted for a slightly longer time, extended symbol time T(s), than the active (or useful) symbol time T(IFFT). The extra time is the guard interval.

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