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Changes between Version 15 and Version 16 of UserDocs/RSSI

Author:
anonymous (IP: 0.0.0.0)
Timestamp:
08/27/08 08:43:31 (11 years ago)
Comment:

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  • UserDocs/RSSI

    v15 v16  
    88== How is RSSI used in the Madwifi driver? == 
    99 
    10 In MadWiFi, the reported RSSI for each packet is actually equivalent to the Signal-to-Noise Ratio (SNR) and hence we can use the terms interchangeably. This is does not necessarily hold for other drivers though. This is because the RSSI reported by the MadWiFi HAL is a value in dBm that specifies the difference between the signal level and noise level for each packet. Hence the driver calculates a packet's absolute signal level by adding the RSSI to the  absolute noise level.  
     10In MadWiFi, the reported RSSI for each packet is actually equivalent to the Signal-to-Noise Ratio (SNR) and hence we can use the terms interchangeably. This does not necessarily hold for other drivers though. This is because the RSSI reported by the MadWiFi HAL is a value in dBm that specifies the difference between the signal level and noise level for each packet. Hence the driver calculates a packet's absolute signal level by adding the RSSI to the  absolute noise level.  
    1111 
    1212As of MadWiFi version 0.9.3, the noise floor is no longer assumed to be a constant -95 dBm. The noise floor is now updated on each receive interrupt by calling out to the HAL, which returns the absolute noise level in dBm. However, because each interrupt can service several packets we cannot get a noise reading for each and every packet. MadWiFi simply takes the measured noise level at each interrupt and assumes all packets serviced during the interrupt were received with this noise level. The measured noise is not used during scanning at present, so all scan results return with a noise level of -95 dBm.