21 Feb 2020

Zig-Bee and WiFi in commercial installations

There are a lot of new devices  that uses Zig-Bee.  These could be door locks, thermostat temp sensors , light switches for home automation.   If you go here you can see some certified ones.

Generally these work fine in a residential situation but I have been attending more and more installations where they have been installed in commercial installations without regard to the existing environment and the Wifi Stopping the Zig-Bee working at all some times.

Zig-Bee and WiFi both  exist in the 2.4Ghz Band and unfortunately they share the same frequencies as well

There MUST be careful planning to make sure they can both exist a the same time.  As you would for a Wifi Design.

In Zig-Bee there are 16 Channels  so different devices can communicate at the same time in the same area.

Unfortunately the16  Channels overlap with the 13 Wifi Channels in Australia

You know the rule:  ONLY USE 1,6,11 in 2.4Ghz in Commercial WIFI designs

In Zig-Bee the channels are 11 to 26

As you can see they overlap with WiFi

If the Wifi 2.4Ghz usage of Spectrum is low, things work OK, the Zig-Bee has enough dead air time to communicate.  NOTE: Zig-Bee and Wifi can not detect each other.  Each is seen as interference to the other.

I have noticed most manufactures set their devices to default to channels 26,25,20,15  as they assume WiFi will be on 1,6,11  to try and avoid interference  but the side lobes of the Wifi  go here and tend to swamp the Zig-Bee.

I have seen lights that take 10 seconds to turn on or Door locks that take 10 seconds to open because the Zig-Bee has to re transmits so many times to overcome the WiFi interference.

A lot of Zig-Bee devices are battery powered and these transmitters just waste battery power.  I have seen devices with a rated battery life of 6 months only last 1 month in high utilization WiFi environments.

In a battle between Zig-Bee and WiFi Zig-Bee normally looses.

Moving Wifi to 5Ghz is a great idea but a lot of devices ONLY work on 2.4Ghz

Generally if you want Zig-Bee to work you need to stop using WiFi channel 11

 Then you can use Zig-Bee Channel 24 25 26  without any worries.

But this only works if you have complete control of the spectrum.

in the below example only 1,6,11 are used in WiFi and side lobes at this location for Zig-Bee  is OK for Channels 15,20,25,26

 Click to view

In a commercial situation you generally cannot control the neighbors  or the employee devices.

and I can bet is a WiFi device on auto channel sees 11 free it will take it !

You need to keep the Zig-Bee Device as far as possible from the AP and the Client so the side lobes have fallen off so much to not interfere

Channelizer from Meta Geek is great as it have a view option to show Zig-Bee channels

At one site the channel 6 Wifi Channel was so busy and AP too close.  You can see how big the side lobes were when measured at the  Zig-Bee Device  (it was configured to use channel 15 and 20)

It was never going to work

Click to view

 At a better designed site  the AP is away from Zig-Bee Device  It was using channel 26 and 11

Channel 26 is away enough not to be too effected by side lob  but if channel 1 or channel 6 was busy Zigbee Channel 11 would be effected.

 Click to view

Imagine Zig-Bee Locks at a private high density student accommodation tower.  With all the students running their own Wifi hot-spots on 2.4Ghz  on channels 1-13  (The 1,6,11 rules is not being obeyed).
 Xbox, Nintendo, Cheap WiFi cameras Wifi connected TVs and phones streaming Netflix.
You could never control the spectrum.  The locks will not work very well and the battery life will be very poor.

 Wifi and Zig-Bee  NEEDS TO BE DESIGNED  with will NOT just work together!

Thank you to my daughter for her drawing skills in sketch-it for the pictures.

10 Feb 2020

Windows 7 Unable to shutdown and slow

Microsoft has discontinued support for windows 7

But when they did windows 7 customers are having issues with machine doing weird things and Admin not being able to shut down

Is this MS trying to force users to windows 10 ??

Seems to be that users do not have admin priv.

Found this solution
  1. 'gpedit.msc'
  2. 'Computer Configuration' > 'Windows Settings' > 'Security Settings' > 'Local Policies' > 'Security Options'
  3. find  'User Account Control: Run all administrators in Admin Approval Mode' and  'Enable'
  4. 'gpupdate /force'
  5. reboot.

This fixed the issue for now.