Uplink and Downlink MC-DS-CDMA Sensitivity to Static Clock Frequency Offsets

H. Steendam and M. Moeneclaey (Belgium)


Synchronization, MC-DS-CDMA


We study the effect of clock frequency offsets on the per formance of multicarrier direct-sequence CDMA (MC DS-CDMA) for both uplink and downlink communica tion, assuming orthogonal spreading sequences. We derive theoretical expressions for the performance degradation caused by the clock frequency offsets, in the presence of a multipath channel. We show that for both up link and downlink MC-DS-CDMA, the performance in the presence of a clock frequency offset rapidly degrades with an increasing number of carriers. It turns out that this degradation is larger in the uplink than in the down link, because the former suffers from a higher level of multiuser interference. For a given maximum clock frequency offset, enlarging the spreading factor in a fully loaded system does not affect the downlink degradation, but strongly increases the uplink degradation.

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