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i'm writing a C program to manage certain aspects of a wireless network (Access Point + Client Devices) One Part of the program runs on the Devices an another runs on the AP. The AP is a simple Linux-Station (a Cubietruck, later on exchanged with a Intel Celeron holding Board; Access Point setup with hostapd and dnsmasq) Some features are already implemented. I've done a lot with cfg80211/nl80211 and a bit with Wext and some Communication Routines over BSD Sockets are standing.

But now a problem came up. In the C program running on the Access Point i need the Received Signal Strength of the associated Devices. On the Devices everything works well. With nl80211 i can get nearly every information about the connection. But on the Access Point i don't know how to obtain the RSS. I've tried some nl80211 requests with some attributes but can't get it to work. Sure, on the Devices it's easy, because they have a single connection. But on the AP i had expected something like a nl80211 answer with a linked list or nested attributes, but nothing. I checked the contained attributes of the answers from certain requests and the messages contain nothing usable.

Does somebody know how to solve this? It shouldn't be a big deal like that to obtain the Received Signal Strength of the associated devices on a WLAN AP. Would be really nice if it were doable with nl80211 but another solution would also be welcome. Maybe with some WiFi Package Parsing? I heared that there is something like a RSSI (Received Signal Strength Indicator) but i'm not familiar with it.

Thanks in advance

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Dionysos
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1 Answers1

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Here's a wrokaround: the wireless channel attenuation from AP to a station/device and from that station to the same AP are identical at the same time. So, if transmission power of AP and stations are all the same, stations may report their RSS to AP using you current solution, and the work is done. Surely tx powers at different stations may be different, but they are constant. So find them out and make adjustments accordingly. Here's a simple example:

AP tx power 20 dBm; Station 1 tx power 15 dBm with RSS -37 dBm; Then the RSS from station 1 to AP link should be -42 dBm

Daniel
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  • Thank you, i also thought about something like that. This would work, but i hoped for a »clean« solution. Nevertheless thanks for your answer. – Dionysos Sep 08 '14 at 08:31
  • Might need to hack into wifi driver. I know sb are able to get not only RSS but also channel response from Atheros WiFi NIC with ath9k driver. – Daniel Sep 08 '14 at 15:10