What are some ways to control my robot while it is outside WIFI range?

[Pito Salas]

Every ROS2 robot I’ve built to date relied on wifi. The Raspi on board connects to my local wifi. The raspi runs Micro-ros and a few other things. My laptop on the same wifi is used to ssh into the robot to launch stuff and also to run several other ROS2 nodes.

Now I want to go outside the range of my local wifi. The options that I can think of are:

1) Put all the nodes “on board” so that no wifi is required. Questions: I think I still need to ssh into the robot to launch stuff, but I could do that when I first turn on the robot and before it goes outside. The remote nodes could run on the onboard Raspi but would it have enough capacity?

2) Use some kind of cellular modem on the robot to connect it to the open internet and in turn connect the remote computer to the same. This may pose some firewall challenges but they can be overcome. But does that cellular modem need to have its own expensive plan with Verizon? Also wouldn’t latency and speed be problems?

3) Create some kind of local hotspot between my laptop and the robot so that as long as they are close to each other they can communicate but not with the open internet. I think that might be possible but I am not sure how to do it.

Have you seen this scenario and do you have suggestions?

Best,

Pito

Boston Robot Hackers &&
Comp. Sci Faculty, Brandeis University

[e...@okerson.com]

You might want to look into WiFi HaLow. It is a wifi system that runs in
the 900MHz band and has much longer range, advertised as 1km but
experiments have gone much farther than that. It would require a HALOW
capable access point and a HALOW radio on the robot, but other than that
everything would work the same. If you want even longer range you can
explore LORA, but it is much lower bandwidth.

Ed Okerson

https://www.morsemicro.com/2024/09/09/pushing-the-limits-wi-fi-halow-testing-in-joshua-tree-national-park/

[Marco Walther]

On 8/25/25 06:25, Pito Salas wrote:
> Every ROS2 robot I’ve built to date relied on wifi. The Raspi on board connects to my local wifi. The raspi runs Micro-ros and a few other things. My laptop on the same wifi is used to ssh into the robot to launch stuff and also to run several other ROS2 nodes.
>
> Now I want to go outside the range of my local wifi. The options that I can think of are:
>
> 1) Put all the nodes “on board” so that no wifi is required. Questions: I think I still need to ssh into the robot to launch stuff, but I could do that when I first turn on the robot and before it goes outside. The remote nodes could run on the onboard Raspi but would it have enough capacity?

That usually does not work very well. You will always want to connect a
'laptop' or something, that's not really on the robot, if it's just for
diagnosing things.

>
> 2) Use some kind of cellular modem on the robot to connect it to the open internet and in turn connect the remote computer to the same. This may pose some firewall challenges but they can be overcome. But does that cellular modem need to have its own expensive plan with Verizon? Also wouldn’t latency and speed be problems?

That could work. But it's expensive for 'hobby' adventures.

>
> 3) Create some kind of local hotspot between my laptop and the robot so that as long as they are close to each other they can communicate but not with the open internet. I think that might be possible but I am not sure how to do it.

That's the way, I'm usually doing things. There are different ways going
about this.

* The Pi can be configured as access point and there are even
setups/scripts out there, which switch between 'being a node in a known
WiFi network' and 'acting as AP' otherwise automatically.

* Use one of those little 'travel routers', which can do the same. I'm
using an [older] GL.iNet GL-AR750S-Ext (
https://www.amazon.com/dp/B07GBXMBQF ). Now you can connect the Pi and
potentially other things via ethernet and have the WiFi for external
things. The range seems to be a bit better than witn the Soft-AP on the Pi.

-- Marco

[Marco Walther]

On 8/25/25 07:10, ed via HomeBrew Robotics Club wrote:
> You might want to look into WiFi HaLow. It is a wifi system that runs in
> the 900MHz band and has much longer range, advertised as 1km but
> experiments have gone much farther than that. It would require a HALOW
> capable access point and a HALOW radio on the robot, but other than that
> everything would work the same. If you want even longer range you can
> explore LORA, but it is much lower bandwidth.

Even 'WiFi HaLow' is 'low bandwidth' compared to 'normal' WiFi. So it
might work for some 'control signals' (starting things, ...), but
probably not for high throughput, like 'remote rviz' or 'remote ros bag'
or things of that nature.

-- Marco

>
> Ed Okerson
>
> https://www.morsemicro.com/2024/09/09/pushing-the-limits-wi-fi-halow-

[Chris Albertson]

The cheapest, zero-cost thing to do is it run an Access Point on the robot. It will then be the center of its own WiFi network. Then if you do need to connect a notebook computer to the robot the notebook has to log into the robot’s WiFi. Of if the robot uses a Web-based interface you can rin the robot and get diagnostics using the browser on your phone. I think this is the first step, Put the WiFi on the robot so the robot will never be out of renge of WiFi.

The next step is more expensive. Place an iPhone on the robot. iPhones can connect to Robot’s Pi4 to the cell network. They can do netwoking over USB. But this ties up an exppenise iPhone. I’ve only done it for maybe an hour at a time.

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[Pito Salas]

Chris,

I wonder whether a decommissioned older or preowned iPhone would work - without a plan. 

Pito

On Aug 25, 2025, at 11:50 AM, Chris Albertson <alberts...@gmail.com> wrote:

The next step is more expensive.  Place an iPhone on the robot.  iPhones can connect to Robot’s Pi4 to the cell network.    They can do netwoking over USB.    But this ties up an exppenise iPhone.  I’ve only done it for maybe an hour at a time.

[Chris Albertson]

Old iPhones work fine, except for the one thing you need, connecting to the celular network.   The Pi can run as an access point with software only.    The only reason for the phone is for cellular networking

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[Karim Virani]

If you want to use a mobile modem or hotspot - you have to pay for a plan. You can "loan" your robot your iphone or android phone with a hotspot plan enabled, so you don't have to pay for an additional device plan, but then you need to accompany your bot or mount it on the bot when roaming. This may be acceptable for tests and is maybe the most flexible method for taking the robot into random environments, but it means you give up your phone at times or you buy a device with a plan for your bot.

And of course satellite networks are a thing ...

You didn't give any details about the environment your bot is operating in. My house is in a forested area, so higher frequency radio options can be blocked by the foliage. But I do have a long driveway where an outdoor directional wifi extender, mast mounted over my house, comes in very handy. 

Other areas of my property can be covered with lower frequency radio tech (LoRa) as a fail-over connection - but this is a hassle. It's ok for very limited telemetry and activation commands. But this requires a configured topic-to-serial bridge, which is implementation dependent on the stack you choose. Even if you have a stack that can emulate tcp/ip, you'll flood LoRa immediately if you try to send normal traffic over something equivalent to 9600 baud serial. Research LoRaWAN, Meshtastic, MeshCore, Reticulum, etc. if you are interested in setting up a low power, low bandwidth backup outdoor network.

I hadn't heard of WiFi HaLow before Ed mentioned it. That sounds like something I need to look into.

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[e...@okerson.com]

On 2025-08-25 10:48, Marco Walther wrote:
> On 8/25/25 07:10, ed via HomeBrew Robotics Club wrote:
>> You might want to look into WiFi HaLow. It is a wifi system that runs
>> in the 900MHz band and has much longer range, advertised as 1km but
>> experiments have gone much farther than that. It would require a HALOW
>> capable access point and a HALOW radio on the robot, but other than
>> that everything would work the same. If you want even longer range you
>> can explore LORA, but it is much lower bandwidth.
>
> Even 'WiFi HaLow' is 'low bandwidth' compared to 'normal' WiFi. So it
> might work for some 'control signals' (starting things, ...), but
> probably not for high throughput, like 'remote rviz' or 'remote ros
> bag' or things of that nature.

WiFi HaLow Data rates can vary significantly depending on the modulation
and coding scheme (MCS) used, channel bandwidth, and distance. For
example, it can range from 150 kbps using a single 1 MHz channel to
potentially 86.7 Mbps with a 16 MHz channel and short guard intervals,
though such high speeds are likely limited to shorter distances. So yes,
less than 2.4GHz or 5GHz WiFi, but much higher than LoRa, so potentially
still useful.

Ed Okerson

[Sergei Grichine]

For connections over a cell phone network, or between LANs, there's a VPN designed specifically for ROS:

https://github.com/slgrobotics/robots_bringup/blob/main/Docs/ROS-Jazzy/README-Husarnet.md

I tried it over the home WiFi, it works fine - providing persistent IPv6 addresses to all robots. It was an overkill for the home network, of course.

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Best Regards,

-- Sergei