Are 802.11 link quality broadcast measurements always reliable?

ABSTRACT

This paper describes an unexpected finding concerning link quality measurements carried out through broadcast frames. We found out that, with experimental equipments/drivers widely used by the scientific community (Atheros WLAN cards with MADWiFi driver), broadcast-based link quality measurements seem to be affected by a NIC-proprietary power saving mode. The striking conclusion is that some packet losses, typically attributed to bad channel characteristics, rather may depend on the broadcast measurement methodology. Unicast measurements are shown to be exempt from such a problem. A very simple test is furthermore proposed to verify whether measurement results are affected by the described phenomenon.

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