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) time to the Inverse FFT time (T(IFFT)). The guard interval is used to eliminate inter-symbol and inter-carrier interference. A copy of the last guard interval T(GI) 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.

 image\OFDMGuardInterval_wmf.jpg

See Also

Format Tab (802.16 OFDMA)