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authorMukesh Agrawal <quiche@chromium.org>2014-04-09 00:54:49 (GMT)
committerJouni Malinen <j@w1.fi>2015-02-01 20:01:18 (GMT)
commitf0d0a5d23bd406a60358add9fa101b49dc9f9039 (patch)
tree02bccd34f5f622c21c174ffb0a26cbd7187446d8 /hs20
parent7f7bfba919a76bb03a7f762eab0ac00d4f5c3184 (diff)
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Improve BSS selection with default noise floor values
When noise floor measurements are not available, compute SNR using default values for the noise floor. This helps steer us towards 5 GHz BSSes in high signal strength environments. In more detail... Existing code prefers a 5 GHz BSS when the 5 GHz BSS's signal strength is "close" to that of the 2.4 GHz BSS, or when both SNRs are large. However, the mwifiex driver does not provide noise floor measurements, so we can't compute SNRs. Because mwifiex doesn't provide NF measurements, the "large SNR" code wasn't effective. By using default values for the noise floor, we can again compute SNRs, and decide that the SNR is high enough that we shouldn't worry about the exact difference in SNR. The default noise floor values (one for 2.4 GHz, and one for 5 GHz) were chosen by measurement in a noisy environment, so they should be conservative. Note that while this patch is motivated by mwifiex, it affects ath9k as well. Although ath9k provides noise floor measurements in general, it will sometimes fail to provide a measurement for one or more specific channels. As a result of this patch, we'll always compare BSSes based on SNR (either measured or estimated), rather than sometimes comparing based on signal strength. ("Always" assumes that the WPA_SCAN_LEVEL_DBM flag is set. It is for mwifiex and ath9k.) While there: - fix a whitespace issue (spaces -> tab) - clean up existing comments - update dump_scan_res to indicate whether the noise floor is measured, or default Signed-hostap: mukesh agrawal <quiche@chromium.org>
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