Customer wants to bring connectivity into the cabin of a 11-storey elevator. The only way we can do this is to use the old trick of placing a bridge unit at the top of the elevator shaft pointing straight down, and a second bridge unit on top of the cabin facing straight up. I know this can be done using a 5ghz ptp bridge, but this is a hotel so 5ghz is already very busy.
I was wondering if anyone has ever used a 60ghz link (eg. Wireless Wire) to set up this kind of link and what was the result?
No reason not to work perfectly fine, it’s clear line of sight, even 5ghz would work just fine I’m sure, but if you want to avoid posible interference go for 60ghz.
Thanks. I agree there’s “no reason it wouldn’t work”, but I’m wondering if there’s something I’m missing. I’ve only worked with 60Ghz on traditional fixed PTP links, so I don’t know how it would behave if one endpoint is constantly moving (vibration, variation in alignment, doppler frequency shift, etc).
For geometry problems (vibration, alignment), using a device with low antenna gain (and thus wide beam) should be enough. I guess that distance won’t exceed 50-60 metres and inside a shaft signal loss should not be that great. Doppler shift might be harder nut to crack, depending on maximum elevator speed we’re looking at around 600Hz of shift. I’ve no idea if that’s huge or not for 60GHz wifi-like radio. However, this article states that with 802.11ax, width of OFDMA subcarriers is between 78kHz and 312kHz. Which means Doppler shift “moves” OFDMA subcarrier by less than 1% from where it’s supposed to be and I guess that even pretty shitty receivers in 802.11ax gear should be able to handle it.
Unless somebody with more knowledge, experience and/or research results comes by and explains things to us, you’ll have to bite the bullet and try it. And tell us how it went
Variation in alignment depends on the characteristics of the antenna, ie. the radiation pattern and the beam area. These key factors affect the possibility of the device might falling outside the signal range. Be aware that some PTP equipment might have problems with short distances.
Doppler frequency shift you do not have worry about (the elevator needs to move really fast to become a problem ).
What you should worry about is vibrations, ie if any models are robust enough to cope with it. I haven’t seen any specific product specifications regarding this. Usually what gives way first are loose cables that are not properly anchored in the unit. They need to be anchored to reduce stress at the cable terminations and to prevent false signals due to cable vibration and slapping. Cables and other components that are allowed to have excessive motion will eventually result in cable metal and insulation fatigue.
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