There are several methods to send data from AP to client in 802.11 standard,such as
DSSS and OFDM
the data throughput also depend on the SNR level, AP calculate the RSSI and SNR to select a modulation method to send data RSSI is high yet Throughput is low
there could be high RSSI but if there are low SNR the AP will select less complex modulation method that could effect the through put.RSSI is low(not high) yet Throughput is high
There could be high SNR, so may the AP select the bit high complex modulation resulting high throughput.
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