Zigbee vs zwave ecosystem


(Eduardo Veras) #1

Witch one is more reliable? witch one has better range? and in general what are the pros and cons of one against the other?

Particulary, im looking at the Lowes iris sensors/ keypad on the zigbee side and the GoControl kits with motion/contact sensors on the zwave side, also im worried about having something future-proof (zigbee-thread compatibility)


ST Alternative?
#2

Hi @Eduardo_Veras,

There’s no real answers to your questions because it all depends on your environment, other devices that can impact reliability, and a few other factors. There are several discussions in the community talking about this subject, so I highly recommend trying a search with your key words.

I wouldn’t worry about the future proof of the devices so much, but more importantly the hub and what’s evolving in the HA world.

https://community.smartthings.com/search?q=Zigbee%20zwave

#3

The community-created wiki has a zwave vs Zigbee article that might be of interest:

http://thingsthataresmart.wiki/index.php?title=Z-wave_versus_Zigbee

There is also a forum FAQ that covers some additional points regarding protocol selection:


(Stephen) #4

Both work well in my environment. I will tell you that all of my zigbee devices seem to react a bit quicker than my z-wave devices. Not sure if it’s just me or not but it is a fact in my set-up.


(Brian Diehl) #5

It really comes down to the number of devices of each type you have (or will have), how far apart they are (and how far from the hub), and how many are repeaters.


#6

I have about 90 devices and roughly 1/2 are zigbee and 1/2 are zwave. Zigbee seems to respond a bit faster in my mind. Also, I have had a couple of problem with zwave device dying killing the network. No problem with zigbee so far in about a year usage. I’ve been adding more and more zigbee where I can.


#7

What do you mean by Z-Wave device dying killing the network?

From what I understand Z-Wave shouldn’t affect wifi networks?

Thanks


#8

It was the z-wave mesh that got screwed up. Things would be really really slow to turn on/off (more than 10 seconds) where at the same time, my zigbee are almost instant meaning it wasn’t a cloud issue. Z-wave repair would come up with a few device failing to route until i power cycled the entire house. After the power cycle, the zwave repair was always good.


(Ash (www.smart-dots.com) / Ashutosh Jaiswal) #9

I know its mentioned in different places, but WiFi interference is a big factor when it comes to Zigbee devices. There is tendency to place the ST hub right next to the WiFi router. If you do that you may have issues even connecting a Zigbee device with the hub, forget the communication… Placing the hub right next to the WiFi router or repeater is a NO NO. One of the things that can be done to mitigate interference is to keep the WiFi and Zigbee channel as far apart as possible. You can check the Zigbee channel on your IDE and your WiFi channel can be checked using several free tools available or just through your router.

Sometimes even though you keep a good distance between the channels, there may be interference issues when placed close to the WiFi router. This could be because of higher order harmonics that can be generated by your WiFi router - especially if there is RF energy that leaks due to poor antenna connection or internal impedance mismatches on the WiFi router (Typically this happens the most on the cheap WiFi repeaters or extenders that people use to extend their WiFi range) - Also known as Inter-modulation Distortion. These harmonics can be enough to interfere with Zigbee, since Zigbee operates at low power and the noise floor created by these WiFi routers may be too much to over come for Zigbee.

Bottom line: Place your hub and sensors at least 6 feet away from WiFi routers, extenders etc. Ideally, an ethernet cable should be wired from the router to somewhere in the central location of your home, and the hub should be placed there. This gives optimal performance and coverage.


#10

Good info. What about interference from a Philips Hue hub (Hue devices are zigbee) and the ST hub? My router isn’t in the same area, but these two hubs are right beside each other. Could that cause any issues?


(Ash (www.smart-dots.com) / Ashutosh Jaiswal) #11

Likelihood is low. The Philips Hue bridge does use Zigbee, but Zigbee networks have a very narrow spectral density - meaning that the activity on the Zigbee channel is very limited - Only active when you turn light ON or OFF, or polling is done etc. In such a situation, it may be unlikely that ST may also be communicating at the same time and they interfere with each other. Moreover, the Zigbee channels that ST uses and Philips Hue uses are likely to be different. It may be a good idea to check the Zigbee channels being used by each hub, just to eliminate any possibility of interference if they use the same channel.


#12

I dont think placing the hub next to the wifi AP is as big an issue as you say. Just have to be smart about the wifi channel you choose.


(Ash (www.smart-dots.com) / Ashutosh Jaiswal) #13

I disagree. It depends a lot on your wireless router as well. It does not matter even if you choose a different channel. If there is impedance mismatch within the WiFi equipment, that will generate harmonic frequencies that can interfere with zigbee communications. These frequencies are strongest close to the equpment and contribute maximum to the interference. It is possible that you may not see an issue at all, but that that does not mean that it is OK to place the hub next to the router. I do several installations and I have seen the impact of placing the hub next to the WiFi router . www.smart-dots.com


(Ray) #14

I totally agree with you. My router is channel 1 and I believe my ST Hub is 15 or 14. Half my zigbee door sensors will drop off my network within a couple of days. Also keep the hub away from your microwave oven at well. It’s a 2.4Ghz killer regardless of channel.


(Ash (www.smart-dots.com) / Ashutosh Jaiswal) #15

I’ve seen this issue with multiple customers of mine. Their Zigbee lights would not work whenever the microwave oven was ON. Unfortunately there is no solution for this, so we changed those specific interference locations with Z-Wave and used the Zigbee devices in other areas where there was no impact of interference.


#16

Move your WLAN to channel 11, channel 1 wifi is very close to zigbee channel 15


#17

Can you give an example of these harmonic frequencies? Its been a while since Ive taken an RF course but my understandings is harmonics only occur at multiples of the carrier frequency.

Do you have any frequency domain RF measurements that can show this occuring due to a wifi hub?


#18

As it happens, zigbee channel 11 and WiFi channel 11 don’t overlap. This is often a good choice, especially since many of your neighbors will probably be on Wi-Fi six. So this gives you a good chance of avoiding both Wi-Fi and Zigbee degradation due to the neighbors’ transmissions.

For ZLL, try zigbee 15. So A set up with smart things on zigbee 11, a hue bridge on zigbee 15 and wifi on 11 usually works. :sunglasses:


(Ash (www.smart-dots.com) / Ashutosh Jaiswal) #19

I dont understand what you mean by an example. But to put it simply, it is a derivative of the original signal. You are right that it is a multiple of the carrier frequency, but harmonic frequencies are very complex. The main concern with a transmitter’s harmonic emissions is the undesired signal outputs which are harmonically related to the fundamental signal rather than to other oscillator circuits. When interference from communications transmitters is experienced, it is a result of inter-modulation or defective equipment, which can interfere with frequencies within the same band.

I work for Ericsson as a Senior RF engineer and we see these kind of issues almost every day for cell phone towers., that use our equipment. Spatial Isolation in such situations usually helps a lot, unless it is not possible then you need to identify the source of the issue , which involves some times swapping the equipment or fixing a poor connection that was causing a high impedance mismatch.

A poorly built router (mostly the cheaper routers and repeaters) is where an issue like this is highly likely, but is relatively a rarer scenario.

A more common scenario will be channel over lap, which we all know and understand. Channel isolation is one of the ways to mitigate this kind of interference for sure, but it is not so easy because the channel that is ideal for WiFi in order to isolate from Zigbee, may not be the best channel for WiFi itself because a lot of your neighbor may be using it already. And unfortunately you cannot change your Zigbee channel . I’ve seen many times where the available WiFi channels are so limited as the neighboring WiFi networks are already using them.

In either case, having the hub closer to the WiFi router will cause an impact., as the WiFi signal is the strongest interferer closer to the router.


(Ash (www.smart-dots.com) / Ashutosh Jaiswal) #20

I think I understood what you were looking for :slight_smile:

See the example below.

The list of WiFi channels with the center frequency is shown below,

The Zigbee Channels are shown below, with the center frequencies.

Assume that your Zigbee device is set to channel 24, which is center frequency of 2470MHz. = f2
And your WiFi is set to channel 1, with center frequency of 2412 MHz = f1

If the Wifi Router has poor quality components or poor impedance matching between components, then RF leakage can generate harmonic frequencies that can interfere with other channels/band.

In this case a relatively lower order harmonic frequency can interfere with Zigbee.

If f1 creates harmonics of the order of 1.02f1, then that is good enough to interfere with the center channel of your Zigbee. 1.02*2412 = 2470 . - The amount of interference can depend on what order harmonics are being generated and what frequency is Zigbee actually communicating over at that instant of time.
Harmonics are not necessarily in multiple of 1,2,3…etc. You can even have lower order harmonics like 0.9f or 1.1f etc.

Hope this clarifies it :slight_smile: