There is a significant number of posts on the internet regarding how people hate bloatware that comes bundled with their devices, how it eats at their precious internal storage space and how they would want to uninstall it (which is impossible w/o rooting your device). While I agree with one’s right to hate the bloatware, everything else is a delusion. Let’s take a look.
This is a very popular question that is asked at literally every WING5 training (and, I must admit, due to misinterpretation I was giving out the wrong answer, so read this). Getting those link levels is easy, troubleshooting the resulting system instability issues is not easy. (more…)
In my recent Android trainings and the Android security talk I gave at AppForum 2014 I was asked to provide a sort of a demo that can be easily replicated to explain the importance of maintaining a proper security posture. So I created a script that ‘recovers’ PSKs from the device and displays them.
Before moving on, a brief disclaimer: Android (or iOS, or Windows) are pretty secure, it is up to the user how much of this security is traded for convenience (or ignorance).
A discussion of my previous post in the 802.11 Wireless professionals group lead to a discovery of a new bit of overlooked knowledge! Many thanks to Eduard Garcia-Villegas and Mike Rex, who turned my attention to this one.
Ever wondered why faster rates have smaller effective distance? It was always attributed to signal fading – higher rates require more complex modulation, which, in turn, requires higher SNR (Signal-to-Noise Ratio) value. So at greater distances, with lower SNR, one has to use lower rates. Simple.
Turns out, in addition to that the transmitters may as well lower their power when transmitting at higher rates! This is done because at higher power values transmitters are more likely to introduce errors in the signal they create due to non-linearity in their behaviour (if you want more details – just go to the discussion). Here’s an example from a datasheet that Eduardo provided (the numbers are Tx Power, dBm):
Note how the power falls as MCS number increases. Also note how this is different in 5GHz depending on channel number.
Mike Rex added, that the users of alternative consumer WLAN router firmwares (such as DD-WRT and Tomato) sometimes suffer from strange performance and link reliability issues, as these firmwares allow varying radio power levels (and other power settings) beyond what manufacturer has intended, resulting in poor Tx signal quality. This mainly is just a result of the shortcomings and compromises in hardware design (even if the APs are built on the same chipset), but certainly not something a non RF engineer would suspect first! 😉
Well, I learned something – this blog already pays off. 🙂 Many thanks to Eduard, Mike and all others, who tool part in the discussion. This bit has been rolled into the original post to keep all things together.
Just finished listening to http://www.wlanpros.com/wlw052-7-rules-accurate-site-surveys/ by Keith Parsons.
Highly recommended – a very good summarisation of site survey lore:
- What do do on a site survey
- What not to do on a site survey
- How can others cheat on a site survey (= do not do it)
- Active vs Passive survey
- Spectrum analyzers
- And more
P.S. Check out the web page for PDF white papers that summarize the podcast!