Longer distance WiFi AP?

On Sun, 5 Nov 2023 11:06:23 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:

>
>[Note that I have to address different markets with likely different
>operating conditions.  So, I'm looking for approaches that can be
>applied to all]

If you plan to sell your system to different countries, please note
that the 900 MHz band is not available on all continents.

In some countries license free NBFM phone channels may be available
just above 400 MHz.

Note also that on 2450 MHz here might be a strict +20 dBm EiRP limit.
If you use directional antennas, you must drop the transmitter power
by that gain amount to remain below the +20 dBm (100 mW) EiRP limit.

>
>In a "home" environment, most residential areas have reasonably
>low speed limits because it's not practical for folks to pull
>out of their driveway into fast-moving traffic.  15 & 25MPH seem
>to be the most common (though folks always abuse those limits
>in the absence of "enforcers").

The NBFM mobile flutter is quite harmless on 400 MHz. I don't know
about 900 MHz but already on 1300 MHz and higher the mobile flutter
can be quite annoying. At those frequencies the multipath null is
often in places close to traffic lights, so if you stop at traffic
lights, you might fail to communicate :-) until the car is moving
again.

On 11/5/2023 2:31 PM, upsidedown@downunder.com wrote:
> On Sun, 5 Nov 2023 11:06:23 -0700, Don Y <blockedofcourse@foo.invalid>
> wrote:
> 
>>
>> [Note that I have to address different markets with likely different
>> operating conditions.  So, I'm looking for approaches that can be
>> applied to all]
> 
> If you plan to sell your system to different countries, please note
> that the 900 MHz band is not available on all continents.

I don't "sell" anything.  My goal in this has simply been to come up with
a "significant" project to tax the limits of multi-modal user I/O
schemes (deaf, blind, mobility impaired, cognitive impaired, etc.)
beyond a "token" example (like a calculator, clock, etc.)

I selfishly chose an example that would be challenging and personally
rewarding; it's cool to be able to walk around the house and have
TVs/HiFis turn off/on to ensure the "content" I was watching follows
me to wherever I happen to want to sit, next!  Or, have the doorbell
announce who's visiting, etc.

But, I have colleagues and other interested parties who are waiting
to exploit the technology (sadly, with typical less concern over the
other UI modality issues) for specific markets.  It's up to *them* to
deal with regulatory issues, I18N/L12N, patents, marketing, support, etc.

[I don't like customers]

> In some countries license free NBFM phone channels may be available
> just above 400 MHz.
> 
> Note also that on 2450 MHz here might be a strict +20 dBm EiRP limit.
> If you use directional antennas, you must drop the transmitter power
> by that gain amount to remain below the +20 dBm (100 mW) EiRP limit.

 From what I've seen, it's relatively easy to get long range with
directional antennae if BOTH endpoints are so aligned.  If one
end (the mobile vehicle) has to use an omnidirectional antenna,
then it may be able to receive broadcasts but not initiate, well.

[Remember, the vehicle is seen as a *room* that just so happens
to move, from time to time.  I don't have special handling for
"the vehicle is not in the garage"]

>> In a "home" environment, most residential areas have reasonably
>> low speed limits because it's not practical for folks to pull
>> out of their driveway into fast-moving traffic.  15 & 25MPH seem
>> to be the most common (though folks always abuse those limits
>> in the absence of "enforcers").
> 
> The NBFM mobile flutter is quite harmless on 400 MHz. I don't know
> about 900 MHz but already on 1300 MHz and higher the mobile flutter
> can be quite annoying. At those frequencies the multipath null is
> often in places close to traffic lights, so if you stop at traffic
> lights, you might fail to communicate :-) until the car is moving
> again.

The closest traffic signal to home is just about 1/2mile -- which
has been the limit of my testing (with the audio link).  I can't,
of course, speak to the environments around future installations
(or, the many types of interference -- physical and RF -- that
may be present, esp in commercial/industrial setting.  My goal
is simply to show that there is a *need* to provide a bit of
"service loop" in the connection to the vehicle (because it can be
in motion before the system realizes it *may* be leaving!) AND
a possible solution to the problem.

The real problem is psychological/behavioral -- folks who have
entered a vehicle have made a cognitive shift from being *in* the
home (or workplace) to *away* from the home/workplace.  They're
thought are more future-bound (what they will be doing
when they get to their destination) instead of past/present-bound
(what they *just* did or are doing).  So, there is some lag
introduced bringing them back to the past/present... but the
vehicle keeps moving (and the limits of the connection taxed)
while they are making this adjustment.

[I am notorious for getting to the next street corner and then
questioning whether or not I closed the garage door.  Invariably,
I have done so as a matter of SUBCONSCIOUS habit.  But, the prospect
of driving off and leaving it open (with associated access to the
house's interior) forces me to make a --WASTED-- U-turn and double
back for a second look.  OTOH, there have been times when a
lawn tool may have fallen into the path of the garage door and
the opener dutifully aborted the close cycle so the unassisted
policy should be to wait for the door to completely close
BEFORE leaving... ain't gonna happen!  An audio link can announce
this problem to me, as it is detected, saving me the trouble of
this wasted trip]

On Saturday, November 4, 2023 at 6:53:07 PM UTC-7, Don Y wrote:
> I currently have a long distance (> 1/2mi) *audio* 
> link between my automation system and our vehicles. 
> This is sufficient to interact with it and for it 
> to interact with us (without having to resort to 
> cell phone connections). 
> 
> I'm looking at fattening the pipe so I can send 
> video and encrypted data (the audio link is licensed 
> for voice only -- though I can get around that 
> for low bandwidth data). 
> 
> In the US, it seems like WiFi is limited to shorter ranges 
> (maybe 600 ft, with a tailwind)? Possibly longer for 
> PtP connections -- but that is challenging with a 
> moving vehicle (the house could track the vehicle's 
> r/theta but the vehicle would be hard pressed to 
> reciprocate) 
> 
> Any other "unlicensed" solutions I can look at?

Sort of sounds like the standard 2-way radio problem. The mobile antenna needs to be vertical omni, but co-linear (to get some gain). That seems very possible at the usual high carrier frequencies for WiFi. But "can you buy one" is another question to be answered. The base antenna can have gain in the same way. And, if say you only drive away to the West, then it can also be directional in that way to also get additional gain.

In the US, 1 W is legal for the 2.4G band. But the cheap WiFi stuff will be at least 10 dB and possibly 20 dB lower than that. If you could figure out how to splice in a 1W amp for the TX'er on both base and mobile ends, ha ha ha, then you can increase your link budget.

If you don't have 2 diverse antennas on each end, then MIMO can't work for your WiFi. It will "downshift."

In the early days of WiFi, experimenters were shooting it across the SF bay with dishes. Not mobile tho.

On 11/7/2023 4:04 PM, Simon S Aysdie wrote:
> On Saturday, November 4, 2023 at 6:53:07 PM UTC-7, Don Y wrote:
>> I currently have a long distance (> 1/2mi) *audio* link between my
>> automation system and our vehicles. This is sufficient to interact with it
>> and for it to interact with us (without having to resort to cell phone
>> connections).
>> 
>> I'm looking at fattening the pipe so I can send video and encrypted data
>> (the audio link is licensed for voice only -- though I can get around
>> that for low bandwidth data).
>> 
>> In the US, it seems like WiFi is limited to shorter ranges (maybe 600 ft,
>> with a tailwind)? Possibly longer for PtP connections -- but that is
>> challenging with a moving vehicle (the house could track the vehicle's 
>> r/theta but the vehicle would be hard pressed to reciprocate)
>> 
>> Any other "unlicensed" solutions I can look at?
> 
> Sort of sounds like the standard 2-way radio problem. The mobile antenna
> needs to be vertical omni, but co-linear (to get some gain). That seems very
> possible at the usual high carrier frequencies for WiFi. But "can you buy
> one" is another question to be answered. The base antenna can have gain in
> the same way. And, if say you only drive away to the West, then it can also
> be directional in that way to also get additional gain.

You also need to be able to connect when returning to the residence/edifice.

> In the US, 1 W is legal for the 2.4G band. But the cheap WiFi stuff will be
> at least 10 dB and possibly 20 dB lower than that. If you could figure out
> how to splice in a 1W amp for the TX'er on both base and mobile ends, ha ha
> ha, then you can increase your link budget.

There are some commercial offerings at higher power levels.

> If you don't have 2 diverse antennas on each end, then MIMO can't work for
> your WiFi. It will "downshift."
> 
> In the early days of WiFi, experimenters were shooting it across the SF bay
> with dishes. Not mobile tho.

The bigger problem seems like it will be installing any such kit in
any random vehicle.  It is considerably easier to fit something to
a home -- regardless of floorplan, elevation, etc.

I think  I will have to resign myself to putting more intelligence in
the vehicle and "coding" data over the audio-only link to be expanded
(or compressed) at the mobile end.

That's unfortunate, but do-able.