CDD (802.16 OFDMA)
When making a CDD Cyclic Delay Diversity (CDD): To avoid unintentional beamforming, the IEEE 802.11n draft standard uses a process known as Cyclic Delay Diversity (CDD), which basically offsets each spatial stream by a different constant, non-coherent delay. The offset considerably lowers the likelihood of correlated signals being transmitted by two or more antennas. This, in conjunction with a pseudorandom scrambler run over the transmitted data bits, ensures that the likelihood of two spatial streams correlating is very low. "Cyclic-Delay Diversity" measurement, the metric is the measure of cyclic delay applied to the signal in TS Technical Specification "Time Sample" units.
CDD is only provided when Enable Cyclic Delay Diversity (CDD) Measurement on the tab is selected is selected.
TS "Time Sample" units
TS is the basic sample time for the signal, which is identified as the "TCD 1) Collision Detection, or 2) Carrier Definition" parameter in the "CDD coding" graphic below.
TS = TCD = 1/(BW*BWRatio)
See Also
