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?

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?

Even with a spotty connection, a house station which knows
theta can communicate the best reply azimuth angle to the vehicle, eventually?
Or, at least send the info in a text to a cellphone.

The obvious other solutions are in the LoRaWAN category,
and not easily available in off-the-shelf onesies. Those too aren't
fat pipes. Even before 802.11b WiFi, there were point-to-point solutions good
for a mile, line-of-sight, with dish antennae (fixed aim); you could conceivably
make a mesh, routing narrow-focus links to omnidirectional nodes.

On 11/4/2023 7:30 PM, whit3rd 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?
>
> Even with a spotty connection, a house station which knows
> theta can communicate the best reply azimuth angle to the vehicle, eventually?

The vehicle would actually have an easier time of communicating
theta (wrt the house). The house's location AND ORIENTATION
never change. The vehicle's location *and* orientation will
be in a state of flux so the angle from the "center of mass"
of the vehicle may be knowable but the angle at which a
directional antenna (fixed relative to the vehicle's
orientation) needs to track back to the house would vary.

It's relatively easy to fit a transceiver to a vehicle.
Adding an antenna that can be dynamically aimed makes
that considerably harder (without constraining the vehicle
choice).

> Or, at least send the info in a text to a cellphone.

The goal is to treat the vehicle as yet another "room"
in the house -- until it gets too far away.

E.g., if I put something on the stove and step into a bedroom
for "too long", I can be reminded of this (at an "appropriate"
time). If I step into the *garage*, the same should apply.

I.e., in each case, my freedom of movement shouldn't be limited
because of an action that I took -- until it looks like I may
be creating a hazard (did I forget the stovetop?)

OTOH, when I get *in* a vehicle and start to move away from
the house, it's quite likely that I plan on leaving and may
have truly forgotten the risk I've created. I am not REQUIRED
to carry a cell phone so there are few ways to get my attention
once in the vehicle and "headed out".

Also, keep in mind that 1/2 mile doesn't allow for much time
before you may have moved out of range of any transceiver
built into the vehicle. At which point, the only alternative
*is* a cell phone.

The industrial/commercial equivalents are tugs/motorized carts/
personal transports that allow a person to quickly travel
outside their normal "working range". The farther afield
an individual can "stray" before you reel him back in, the
more annoying the behavior will be seen as. ("why couldn't
you tell me BEFORE I left?")

> The obvious other solutions are in the LoRaWAN category,
> and not easily available in off-the-shelf onesies. Those too aren't
> fat pipes. Even before 802.11b WiFi, there were point-to-point solutions good
> for a mile, line-of-sight, with dish antennae (fixed aim); you could conceivably
> make a mesh, routing narrow-focus links to omnidirectional nodes.

But the back channel from the omnidirectional node (vehicle) needs
to be as fat as the forward channel.

On Sat, 4 Nov 2023 18:52:38 -0700, Don Y <blockedofcourse@foo.invalid>
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?

If the vehicle has a GPS receiver, it could send the coordinates to
the house in each message and the house antenna can aim at that
direction.

With direct line-of-sight (LOS) this should work reasonably, but
requires a high tower at the house to maintain LOS. The receive signal
drops only by the square of distance. To triple the distance, 9x the
power (nearly 10 dB) stronger signal is required.

Below LOS, especially in urban areas, the signal will propagate trough
multiple reflections, this the strongest signal may come from a
direction other than the geometry would suggest. Thus do not use too
narrow antenna beams.In urban areas below LOS the signal strength may
drop relative to the forth power of distance. To triple the distance
81x (19 dB) more power is required.

Low data rate systems can operate at lower RF frequencies (HF/VHF) and
do not suffer too hard from vegetation losses, when operating below
LOS. To transfer high data rates (such as video) a higher
UGF/microwave frequency must be used and it suffer more from
vegetation.

To increase the bit rate 100 times for video, 100x (20 dB) more power
is required. Also the transmission method must tolerate ,multiple
reflections (such as COFDM) especially with paths below LOS.

Thus extending the range requires a lot of power and / or higher base
station mast, which limits the licence free system range quite
severely.

On a sunny day (Sat, 4 Nov 2023 22:46:47 -0700) it happened Don Y
<blockedofcourse@foo.invalid> wrote in <ui7a8j$3req2$1@dont-email.me>:

>The industrial/commercial equivalents are tugs/motorized carts/
>personal transports that allow a person to quickly travel
>outside their normal "working range". The farther afield
>an individual can "stray" before you reel him back in, the
>more annoying the behavior will be seen as. ("why couldn't
>you tell me BEFORE I left?")
>
>> The obvious other solutions are in the LoRaWAN category,
>> and not easily available in off-the-shelf onesies. Those too aren't
>> fat pipes. Even before 802.11b WiFi, there were point-to-point solutions good
>> for a mile, line-of-sight, with dish antennae (fixed aim); you could conceivably
>> make a mesh, routing narrow-focus links to omnidirectional nodes.
>
>But the back channel from the omnidirectional node (vehicle) needs
>to be as fat as the forward channel.

My solution was:
A drone.
https://panteltje.nl/panteltje/quadcopter/index.html
A drone high up can relay to a wide area.
To keep it up I used power transfer using some hundreds of volts at a hundred kHz over a thin coax:
https://panteltje.nl/pub/h501s_drone_remote_power_test_ground_control_1_IMG_6276.JPG
note the thin coax over the fence
transformer and rectifier at the drone site:
https://panteltje.nl/pub/h501s_drone_remote_power_drone_side_IMG_6278.JPG
You can use the coax at the same tome for the WiFi RF
All GPS controlled.

Some WiFi repeater PCB should weight nothing. a small drone like this should do.
Of course it is weather dependent.
If you want to send video or whatever, have the drone deliver a 1 TB SDcard or USB stick.
Much faster than a RF link!!

And there is of course Starlink...

On 11/5/2023 12:45 AM, upsidedown@downunder.com wrote:
> On Sat, 4 Nov 2023 18:52:38 -0700, Don Y <blockedofcourse@foo.invalid>
> 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?
>
> If the vehicle has a GPS receiver, it could send the coordinates to
> the house in each message and the house antenna can aim at that
> direction.

Yes, but that doesn't handle the return path from the vehicle.
(that is the tougher nut to crack -- without requiring
tedious modifications on that end)

> With direct line-of-sight (LOS) this should work reasonably, but
> requires a high tower at the house to maintain LOS. The receive signal
> drops only by the square of distance. To triple the distance, 9x the
> power (nearly 10 dB) stronger signal is required.

The audio link (900MHz?) works quite well without directional
antennae *or* a high-mount antenna. I.e., I can get a bit more
than 1/2mi with a desk-mounted base and handheld transceiver.

This was, initially, sufficient as speech is one of my supported
interface modalities.

But, *now* attempting to extend that to incorporate video
(e.g., for a deaf user and/or to augment the material that
can be presented over the link), a fatter pipe is required
with attendant problems...

> Below LOS, especially in urban areas, the signal will propagate trough
> multiple reflections, this the strongest signal may come from a
> direction other than the geometry would suggest. Thus do not use too
> narrow antenna beams.In urban areas below LOS the signal strength may
> drop relative to the forth power of distance. To triple the distance
> 81x (19 dB) more power is required.

I was initially thinking of just seervoing the azimuth control
to signal strength and let the antenna "hunt" for the best
orientation -- hoping it could keep up with the movement of the
vehicle.

But, as above, the vehicle would have a similar problem
keeping its antenna oriented properly.

Eliminating that complexity seems essential for a practical solution.

> Low data rate systems can operate at lower RF frequencies (HF/VHF) and
> do not suffer too hard from vegetation losses, when operating below
> LOS. To transfer high data rates (such as video) a higher
> UGF/microwave frequency must be used and it suffer more from
> vegetation.
>
> To increase the bit rate 100 times for video, 100x (20 dB) more power
> is required. Also the transmission method must tolerate ,multiple
> reflections (such as COFDM) especially with paths below LOS.
>
> Thus extending the range requires a lot of power and / or higher base
> station mast, which limits the licence free system range quite
> severely.

If *both* endpoints were fixed, it would be considerably easier.
But, "allowing" (!) one to move complicates things.

I can "cheat" and put some (a fair bit!) local intelligence at each end
to convert video images to low bandwidth messages which could
then be encoded into speach-ish signals for transmission. But,
that also increases the problem's complexity (as well as constraining
the material that can be presented).

On Sun, 5 Nov 2023 04:27:56 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:

>On 11/5/2023 12:45 AM, upsidedown@downunder.com wrote:
>> On Sat, 4 Nov 2023 18:52:38 -0700, Don Y <blockedofcourse@foo.invalid>
>> 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?
>>
>> If the vehicle has a GPS receiver, it could send the coordinates to
>> the house in each message and the house antenna can aim at that
>> direction.
>
>Yes, but that doesn't handle the return path from the vehicle.
>(that is the tougher nut to crack -- without requiring
>tedious modifications on that end)

RF paths are usually quite bidirectional so if the house has a high
directivity antenna and the car has an omnidirectional antenna, the
sum of antenna gains (in dBi) is the same, so if you have the house
antenna in proper direction, it also helps the uplink from the car.

>> With direct line-of-sight (LOS) this should work reasonably, but
>> requires a high tower at the house to maintain LOS. The receive signal
>> drops only by the square of distance. To triple the distance, 9x the
>> power (nearly 10 dB) stronger signal is required.
>
>The audio link (900MHz?) works quite well without directional
>antennae *or* a high-mount antenna. I.e., I can get a bit more
>than 1/2mi with a desk-mounted base and handheld transceiver.

You are not gain to get high speed video on quite narrow 900 MHz band
but need to use at least the 2450 MHz band with plenty of bandwidth.
However, for an omnidirectional antenna, the caption area is
proportional to the wavelength squared, thus going from 900 MHz to
2450 MHz will give about 1/10 signal thus require nearly 10x more
power. The higher bit rate may require up to 100 x (20 dB) more power.
Thus you may require up to 1000x (30 dB) more power. Alternatively use
directional antenna at the house and the power requirement can be
reduced.

>This was, initially, sufficient as speech is one of my supported
>interface modalities.
>
>But, *now* attempting to extend that to incorporate video
>(e.g., for a deaf user and/or to augment the material that
>can be presented over the link), a fatter pipe is required
>with attendant problems...

Why not let the deaf person use ordinary cellular video and the rest
of the users use your own narrow band private system.

>
>> Below LOS, especially in urban areas, the signal will propagate trough
>> multiple reflections, this the strongest signal may come from a
>> direction other than the geometry would suggest. Thus do not use too
>> narrow antenna beams.In urban areas below LOS the signal strength may
>> drop relative to the forth power of distance. To triple the distance
>> 81x (19 dB) more power is required.
>
>I was initially thinking of just seervoing the azimuth control
>to signal strength and let the antenna "hunt" for the best
>orientation -- hoping it could keep up with the movement of the
>vehicle.

That is one option.

How fast is the car moving ? If it is moving fast, there can be quite
bad multipath flutter, so select a proper modulation method.

>
>But, as above, the vehicle would have a similar problem
>keeping its antenna oriented properly.
>
>Eliminating that complexity seems essential for a practical solution.
>
>> Low data rate systems can operate at lower RF frequencies (HF/VHF) and
>> do not suffer too hard from vegetation losses, when operating below
>> LOS. To transfer high data rates (such as video) a higher
>> UGF/microwave frequency must be used and it suffer more from
>> vegetation.
>>
>> To increase the bit rate 100 times for video, 100x (20 dB) more power
>> is required. Also the transmission method must tolerate ,multiple
>> reflections (such as COFDM) especially with paths below LOS.
>>
>> Thus extending the range requires a lot of power and / or higher base
>> station mast, which limits the licence free system range quite
>> severely.
>
>If *both* endpoints were fixed, it would be considerably easier.
>But, "allowing" (!) one to move complicates things.

Just for this reason, modern cellular phone systems use MIMO (Multiple
Input Multiple Output) multibeam antennas at base stations and some
phones has also some MIMO capability to avoid the problems with
capture area problems in mobile phones.

>
>I can "cheat" and put some (a fair bit!) local intelligence at each end
>to convert video images to low bandwidth messages which could
>then be encoded into speach-ish signals for transmission. But,
>that also increases the problem's complexity (as well as constraining
>the material that can be presented).

On 2023-11-05, Don Y wrote:
> [...]
> 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)

It's not so much that it's "limited to X distance", but rather that 4
watts (36dBm EIRP) is only going to get you so far, especially with
omnidirectional antennas. Directional antennas will help, provided you
can keep them pointed more-or-less the right way.

Then there's the rules for fixed point-to-point, which allow you to put
high-gain antennas up (with a commensurate reduction in transmitted
power at the radio itself).

At least on 2.4 GHz ... 5 GHz gets fun, because you have to consider
which band, etc.

--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

On 11/5/2023 5:54 AM, upsidedown@downunder.com wrote:
> On Sun, 5 Nov 2023 04:27:56 -0700, Don Y <blockedofcourse@foo.invalid>
> wrote:
>> The audio link (900MHz?) works quite well without directional
>> antennae *or* a high-mount antenna. I.e., I can get a bit more
>> than 1/2mi with a desk-mounted base and handheld transceiver.
>
> You are not gain to get high speed video on quite narrow 900 MHz band
> but need to use at least the 2450 MHz band with plenty of bandwidth.

Yes. I use WiFi to make the connection to the car while
*proximate* to the house -- i.e., so it is treated as a "room"
WHILE there. This lets me display obstructions on one of the
in-dash displays to show the driver why he shouldn't pull in/out
of the garage (under those conditions), let him interact with the
automation system (e.g., "please lock the doors in the house",
"please prep the house for my immediate occupancy as I have
returned home", etc.).

[Some *driveways*, here, would tax that 1/2mi range and easily
exceed the range of the wifi I've deployed!]

But, if the driver is not planning on interacting with the house,
it gives the house very limited opportunities to interact with
him without inconveniencing him (i.e., "please pull over before you
drive out of range for this conversation to continue to its
intended conclusion").

The audio link provides that channel for a longer distance
without that inconvenience ("Did I shut the garage door?
If not, please shut it for me! What do you mean, you
*can't*??! Oh, OK, I will have to return home and move those
items that are in the path of the door's closing... BRB")

I would like to be able to use the video modality for
folks who can't process audio -- as well as offer more
features for those who can.

> However, for an omnidirectional antenna, the caption area is
> proportional to the wavelength squared, thus going from 900 MHz to
> 2450 MHz will give about 1/10 signal thus require nearly 10x more
> power. The higher bit rate may require up to 100 x (20 dB) more power.
> Thus you may require up to 1000x (30 dB) more power. Alternatively use
> directional antenna at the house and the power requirement can be
> reduced.
>
>> This was, initially, sufficient as speech is one of my supported
>> interface modalities.
>>
>> But, *now* attempting to extend that to incorporate video
>> (e.g., for a deaf user and/or to augment the material that
>> can be presented over the link), a fatter pipe is required
>> with attendant problems...
>
> Why not let the deaf person use ordinary cellular video and the rest
> of the users use your own narrow band private system.

It requires them to carry a cell phone and necessitates the
initiation of a "call" (which adds further latency). Here,
you can not "operate" a phone while you are driving a vehicle
so the driver would have to pull over for the call.

And, it makes the deaf/mute user a different type of user.
(they don't have to carry a phone around the interior of the
house so why require them to carry one in this "special
room"?)

[All users have to use a phone if they are "remote" so there
is no bias, there]

>>> Below LOS, especially in urban areas, the signal will propagate trough
>>> multiple reflections, this the strongest signal may come from a
>>> direction other than the geometry would suggest. Thus do not use too
>>> narrow antenna beams.In urban areas below LOS the signal strength may
>>> drop relative to the forth power of distance. To triple the distance
>>> 81x (19 dB) more power is required.
>>
>> I was initially thinking of just seervoing the azimuth control
>> to signal strength and let the antenna "hunt" for the best
>> orientation -- hoping it could keep up with the movement of the
>> vehicle.
>
> That is one option.
>
> How fast is the car moving ? If it is moving fast, there can be quite
> bad multipath flutter, so select a proper modulation method.

[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]

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").

In an industrial/commercial environment, 15MPH is more common
because the vehicle (a tug/PTD/motorized cart/etc) won't
be designed for "on-road" travel so its top speed will be
less - and it will likely be operated in traffic that can't
tolerate high speeds (e.g., pedestrian traffic).

By far, the worst market is dealing with elderly folks trying
to live at home without assistance. In those cases, there is
no one to interact with the user as they undertake some "bad"
behavior (e.g., "Where are you planning on going, in the car,
Sharon? No, you don't need to do that; why don't you come
back into the house?"). You want to leave these people with
as much freedom as possible (i.e., don't lock the garage door
to prevent them from driving off). Yet, still need to keep
them on a "short leash" (sad metaphor). So, you need to be
able to "talk" (interact) with them after you've discovered
they have done something "wrong" and hope they come around
to your line of thinking before they are out of range for you
to continue that interaction (because they may not be "aware"
enough to realize they should stop moving while trying to
get their wits).

[We had a neighbor that we (the remaining neighbors) were
convinced would be the subject of a "silver alert"[1], one
day, as she was in the habit of driving off for <whatever>
and we suspected her memory not sufficient to always get her
back home, intact. Her (remote) kids eventually acknowledged
the risk and hired 24/7/365 in-home caregivers essentially
to prevent her from driving off, leaving the stove on,
falling in the swimming pool, etc.]

[1] Here, we have different BROADCAST "alerts" for different
high-stakes events: <https://en.wikipedia.org/wiki/Silver_Alert>,
<https://en.wikipedia.org/wiki/Amber_Alert>

On 11/5/2023 7:38 AM, Dan Purgert wrote:
> On 2023-11-05, Don Y wrote:
>> [...]
>> 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)
>
> It's not so much that it's "limited to X distance", but rather that 4
> watts (36dBm EIRP) is only going to get you so far, especially with
> omnidirectional antennas. Directional antennas will help, provided you
> can keep them pointed more-or-less the right way.

They also help with the (inevitable) other users of the frequency
range in which you're operating -- a reason I opted NOT to use
wireless comms for the other communications paths in the system.

> Then there's the rules for fixed point-to-point, which allow you to put
> high-gain antennas up (with a commensurate reduction in transmitted
> power at the radio itself).
>
> At least on 2.4 GHz ... 5 GHz gets fun, because you have to consider
> which band, etc.
>
>

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.