For the RSSI calculation with LNA in the Receive side of the miniPCI module , the gain of the
LNA is reduced from the signal strength received by the base band chip.
we are reducing the gain with the signal strength. Because based on the RSS, the rate control algorithm is going to work. For example. if the gain of
LNA is 10dB and the Rx signal is -80dBm at antenna port.
Case 1: RSS with LNA gain calculation reported in madwifi layer = -80dBm actual RSS will be -70dBm at the base band chip
Case 2 : RSS without LNA gain calculation reported in madwifi layer = -70dBm , actual RSS will be -70dBm at the base band chip and -80 at the antenna port
so when the rate control algorithm works,
case 1 it will transmit in 24Mbps , assuming -80 for 24Mbps Rx sensitivity
case 2 it will transmit in 54Mbps. say the for 54Mbps the Rx sensitivity is -70dBm
but in case1 the actual RSS was -70 with which it can transmit at 54Mbps, so loosing the throughput.
so adding the LNA gain is wrong right ??? the RSS should be the value at antenna port or at the chip input.
So adding the LNA gain is good or bad ???
Dino Joseph Mycle