You are here

Mikrotik devices and 5Mhz bandwidth?

19 posts / 0 new
Last post
ng1p
ng1p's picture
Mikrotik devices and 5Mhz bandwidth?
I have heard reports the some Mikrotik devices only work at 10 and 20Mhz bandwidth (not 5Mhz)? Is this true for all Mikrotik devices that support the AREDN firmware? I have a local ham trying to connect to the mesh using the 27dB gain Mikrotik dish and it's not working. 

thank you Bill NG1P

 
nc8q
nc8q's picture
27dB gain Mikrotik dish
Hi, Bill I have a pair of RBLHG-5HPnD-XLs linking at 5 MHz. Please be more specific that "it's not working." Channel matches? Bandwidth matches? SSID matches? No 'SNR' ? Got 'SNR' but LQ/NLQ < 100% ? It will be extremely difficult to troubleshoot your 'local ham' with so little information. :-| Chuck
ng1p
ng1p's picture
More info
I stopped by kb1kin Ron's home when he was not able to connect to the mesh node that's at 5Mhz bandwidth. I used my nanostation and tried to connect to his RBLHG-5HPnD-XL and it did but just for a second and then never did again. Didn't see this url until after. Will need to test again at 10Mhz to see if his hardware has this issue: 
https://www.arednmesh.org/content/hap-ac-lite-hardware-quirks
https://github.com/aredn/aredn_ar71xx/issues/301

just trying to understand if this is across multiple Mikrotik devices. It's good to know yours are working.

 
w8erw
w8erw's picture
hAP AC Lite with Ubiquity Devices
I have a MESH setup here in the shack using AirRouters and a go box with both an AirRouter and a hAP AC Lite.  The Mikrotik device in the Go Box will not mesh with the Ubiquity devices at 5Mhz channel width.  Was there not an issue at some point with this?  The AirRouters all mesh just fine.  The hAP AC Lite will operate as DTD off the AirRouter.   The go Box does have it's own seperate Internet access via a cellular hotspot. 
 
Jim W8ERW
KE2N
KE2N's picture
basebox

I tested early versions of the AREDN software for a 2 GHz MikroTik "BaseBox" and it produced a really weak and funny-looking output (as seen on the spectrum analyzer)  when operated on 5 MHz. As I recall, it barely linked with another BaseBox and would not talk to Ubiquiti gear.  With 10 and 20 MHz BW it worked fine.   I do not know if the AREDN developer team ever followed up on that.

Ken
 

AJ6GZ
5MHz
I've found the MikroTiks *may* work at 5MHz but only with other MikroTik stuff... it generally doesn't work with Ubiquiti equipment.
ng1p
ng1p's picture
Interesting
If this is true it would be a good idea to post this info as part of the "Supported Platform Matrix" just so others know this is a limitation.
AB7PA
Recent drive test data

I just returned from a short "drive test" session with my portable Mikrotik SXTsq Lite2, which is the same Mikrotik board shared by the SXT, LHG, and LDF devices.  I understand that this was not a controlled bench test, but just to add some anecdotal data to the mix, it does not seem like a generalization can be made that "Mikrotik radios cannot communicate with Ubiquiti devices using 5 MHz channel width."  In about an hour of driving around my area I was able to make direct RF contact with almost a dozen Ubiquiti Bullet and AirGrid devices.  There was not a single Ubiquiti node within RF range that I could not make RF contact with, so I saw no failures using 5 MHz channel width.

ng1p
ng1p's picture
Thank you..
I invite others to share what they are seeing also. I know looking at the links I included about it was a hardware issue. So I wonder if newer hardware is having this issue? Will do some more testing on this and will share what we (Ron and I) find out.

Thanks Bill NG1P
AJ6GZ
Tried...
I believe there was another thread(s) about 5Mhz issues on the forum here. It was reported to be able to see other devices, but not able to hold a reliable connection or move data as a previous post here also indicated. I have seen the "it connected once but not again" myself between two Nano M2's, a hAP, and BaseBox2, tho if I recall the BaseBox "kinda" worked. Also you indicated testing against Bullets and AirGrids which are not MIMO devices. Might be something to that? Worth investigating just for fun? (tho the SXT is MIMO). We don't have any SISO devices in this area to try. I tested 5Mhz because parts of San Diego Co are using 5Mhz on 2Ghz for whatever reason maybe a holdover from the linksys days? So sticking with a Nano at that location. Don't really use 2Ghz much except for local 'on-site' coverage. I have not tested 5Mhz on 5Ghz.
AE6XE
AE6XE's picture
Performance of 5Mhz vs 10Mhz
Performance of 5Mhz vs 10Mhz

Generally 10Mhz is going to better perform at most distances over 5Mhz channel widths.  By "perform" better, this means higher data throughput measured by iperf.  Is 5Mhz in use due to limited RF space?  If not, have you tested and compared with a 10Mhz channel width to determine which yields better performance?    How significant is it to invest in working around the symptoms?

Joe AE6XE
ng1p
ng1p's picture
Good thought
I know I have been looking at using 5Mhz thinking it's going to provide the best performance at lower signal levels. I know right now I'm at 15 dB SNR switching to 10Mhz that drops to 12dB SNR. I'm I looking at this wrong? Should I just switch to 10Mhz? 

thank you Bill NG1P
AE6XE
AE6XE's picture
It's a bit more complex than
It's a bit more complex than comparing instantaneous SNR.    At a given point in time, the same xmit power is transmitted,  but there's half the ambient noise given half the bandwidth.   So we'd see at a given point in time the SNR to be 3dB better for half the channel width.   If we're dealing with weak signals on the edge and this 3dB is necessary to decode any data, then you need the smaller channel width.  But generally, we are not dealing with this weak signal state. 

When we do cut the channel in half,  the same 64 carrier waves and xmit power are squeezed into half this bandwidth, and then the symbol length is doubled.   The difference is:

1) half the bandwidth can only do maximum half the bit rate, so max MCS15 rate drops from 130Mbps @ 20Mhz channel to 65Mbps @ 10Mhz channel. 
2) the symbol is transmitted twice as long.  This longer symbol time and built in guard gap between transmitted symbols gives more time for fading or reflections that could trash the successive symbol for larger bandwidths and shorter guard gap.   If this guard gap is too short for how long it takes a signal reflection to be received, data throughput is trashed -- inter-symbol interference is occurring.   

Unbiquiti gives many channel width options in AirOS.  If we did the math, we could determine the optimal channel width, or minimum amount of time in the
symbal gap interval necessary for a given distance for how long reflections would take to be received, to determine optimal channel width or symbol gap timing.  This is a big reason to set channel width, based on optimal timing for a given distance of the link.

Generally, the lower SNR for the larger bandwith can still achieve higher thoughput  than half the bandwidth and higher SNR that cuts the max rate in half.   If you can already achieve 32.5Mbps link rate or greater in 10Mhz channel, it's unlikely to improve performance n 5Mhz channel, with max 32.5Mbps protocol rate.   But check iperf thoughput as best measure, not raw link rate.  

Joe AE6XE
ng1p
ng1p's picture
Thank you Joe
Great feedback as always!
I switched over to 10mhz this morning. Will run some tests. I did install iperf but noticed on the node up on the 250 tower it ran out of space when I tried to load Iperfspeed but still loaded. I then removed SNMPD to get some more space then did a reboot but it never came back. Will need to make a trip out and see if a power cycle brings it back. (Hopefully I don't need to climb the tower to hit the rest button)
KD1HA
KD1HA's picture
Bill you know that you should
Bill you know that you should not need to climb the tower to reset the device. The reset button on the POE is the same as the reset on the device assuming that POE source is at ground level.
Denis   
ng1p
ng1p's picture
Thanks...
I notice the smaller 1/2 amp supply don't have that reset button (Nanostations) But the Rocket supplies do. I tested that today on 2 Rocket models and works great. See if I can get to the Tower site in a few minutes and give it a try.
KD1HA
KD1HA's picture
Look on the underside of the
Look on the underside of the supply (it's very small) all my POE's including the 1/2 have it.
ng1p
ng1p's picture
50/50
So you are correct 1/2 of the 1/2 amp supplies that i have do have the reset button. Interesting that some do and some do not. I even have a few 1 amp supplies that don't have the reset button. Will keep a few on had. Btw the reset worked great at the tower site. We are back and running.

thank you Bill NG1P
w8erw
w8erw's picture
5Mhz vs 10Mhz
Initially 5Mhz was chosen to fit within the existing MESH environment and before the MikroTik devices were introduced.  At this time, I would agree that a switch to 10Mhz would be the appropriate decision, likely improving existing MESH operation and resolving the incompatibility of the MikroTik devices at 5Mhz.
 
I appreciate the clarification and additional information.
 
Thanks,

Jim W8ERW

Theme by Danetsoft and Danang Probo Sayekti inspired by Maksimer