WCDMA uses code division multiple access (CDMA). WCDMA is a spread spectrum system that spreads the data with a direct sequence (DSSS) to a chip-rate of 3.84Mcps. By using different spreading rates from 2 to 256; it can accomplish varying data-rates from 12.2kbps to almost 2Mbps. The spread data is modulated with QPSK. Different users residing on the same frequency at the same time; are separated by different orthogonal codes. Duplex is accomplished by frequency division (FDD) where transmission and reception take place simultaneously at different frequencies. For details about WCDMA see .
802.11a uses an orthogonal frequency division multiplexing (OFDM)transmission scheme. It can be seen as information divided between a set of sub-carriers separated in frequency. The total bandwidth used is 16.6MHz. The information is modulated on to the sub-carriers with different schemes depending on the used data-rate. For the lowest rate the modulation scheme is QPSK ranging up to 64QAM for the highest data rate of 54Mbps. In 802.11a duplex is accomplished by time division (TDD) where transmission and reception takes place at different times at the same frequency. For details about 802.11a see .
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