Emergency Network Cell Tower

Portable devices capable providing messaging services via WiFi in the event cell networks fail during an emergency.

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This project is aimed towards building a portable cell tower that is not only economic and reliable for sending valuable information, like Global Positioning System (GPS) locations, but also intuitive to deploy and use. The cell tower will act as a WiFi hotspot (mainly for mobile connectivity and short-distance voice calls and text) as well as utilize the Automatic Packet Reporting System (APRS) for long-distance text communication and GPS location reporting.

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aaaaaa wrote 11/30/2023 at 17:42 point

@abram morphew APRS is not good protocol

I think about whole FAX.25 (AX+crc correction, compatible with ax)

meybe using MMDVM sound modem ?

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aaaaaa wrote 08/07/2023 at 15:41 point

"FCC regulations states that in an emergency situation, any person is legally permitted to use any frequency to prevent damage"

But what this testing in normal situation?

Ham operators are not willing to develop software for non-ham. Therefore, I believe that using APRS on non-shortwave bands is stealing bandwidth and airtime.

Either cooperate and develop common software, or fight for resources.

The choice is yours.

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aaaaaa wrote 07/15/2023 at 18:30 point

not every people using aprs on ham radio. better way is using reticulum not aprs

and more band like lora,433MHz and wifi mesh (for example batman-adv in linux)

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abram morphew wrote 07/17/2023 at 16:37 point

Given from your comment here, I suspect you don't understand how the system really works. Using APRS worked quite well for connecting the node to the SMS network allowing the user to communicate via two-way text messaging without a connection to a commercial cell tower. It just uses the APRS network as a proxy for SMS messaging as well as reporting the users GPS coordinates to the APRS network, thus increasing visibility during an emergency. This is similar to emergency traffic voice nets that relay 3rd party messages between non-hams when needed.

You're certainly right about LORA and WIFI mesh networking allowing for better connectivity between individual nodes. In fact, WIFI mesh networking was already included in the spec and configured by default (using batman-adv). However, being a device intended for use only in emergency situations, there is the potential that only a single node could be active over a large area where higher bandwidth modulation schemes might not be suitable. Having a system that can use every possible means of reporting your location and allowing the user to send out a message to family and loved ones was the main goal of the project. If our small team had the resources to go back and do this again, we would probably include some sort of SDR hardware capable of transmitting so we could even include a modulation that has the narrowest bandwidth and, thus, the furthest reaching propagation, CW (aka Morse Code).

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aaaaaa wrote 08/04/2023 at 17:28 point

You probably haven't looked into what a reticulum is ;)

In an emergency situation the most important thing is to have one device , power and the ability to use this device without additional devices such as a keyboard or cell phone.  People are willing to write a program, even in assembler, but they need to have a lot of communication options. Modems. You can always add an irda

APRS, however, is a closed system for ham radio operators only and is not even full X.25.

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a_r_murton wrote 04/12/2018 at 20:22 point

I've often thought  a temporary cell phone base station for emergency situations would be useful but I wasn't sure whether they already exist. Also I don't know how it would connect to the 'outside world' or be powered. Have you already solved these problems?

My usage scenario is say after a hurricane or  earthquake  eg Haiti where people need to contact their loved ones and find online lists of those missing or found, and safe places to go.

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abram morphew wrote 04/12/2018 at 21:17 point

Some definitely do exist, but the ones we've found are quite expensive and not always easy to deploy. Your usage scenario is very much what we envision as well. In order to connect it to the "outside world," we're taking advantage of the amateur radio-based Automatic Position and Reporting System (APRS). This was an old FEMA system developed in the 90s that amateur radio operators use when coordinating disaster relief.  In our system, if someone connects to the tower using their Android phone, it reports their status (OK/not OK), their position, and allows anyone on the APRS network to send information direct to the user. Combining this with a WiFi mesh network, we're hoping this adds a higher degree of visibility to anyone who is in direct need of assistance as well as allow users to be in direct contact with their loved ones in the event they're separated. 

The power supply is a 12V system. There's an internal battery, as well as a way to connect the battery to a wall-charger or additional 12V supply (e.g. car battery, solar panel). 

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aaaaaa wrote 08/04/2023 at 17:34 point

look this

or gotenna

but this is comercials or not working yet ;(

many people have 3.7V (flashlight on 18650) or 1.5V AA or ... solar paneld 5V

problem is with distance. one small cell on lora,433MHz is 500m in town (There are unlikely to be tall buildings in wartime)

Why not using esp8622 or esp32 s3 with screen and touch screen? cheap, power eficient etc. or similar t-deck ;)

make a PCB, add some cpu, power input, keyboard , screen if necessary like a armachat or wiphone or notkia

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abram morphew wrote 08/04/2023 at 19:05 point

Thanks for sharing! all of these are super cool projects/slash ideas and would be cool to integrate into future versions of the project.

to provide a little context for what the impetus for this project, the overall requirements were provided by the fine folks at Intel for a EE capstone project. one of the restrictions was that they wanted the students to only use COTS hardware and for it to be used with currently produced (or at least produced in 2018) cell phone technology. the requirements dictated that we had to make it act like a "cell tower" of sorts. the tower actually does run on 3x 18650s. we just had to buy a pre-made battery pack which we then modified to include the 5v regulator for budget purposes.

that being said, APRS is not exclusive to ham radio operators. for one, FCC regulations states that in an emergency situation, any person is legally permitted to use any frequency to prevent damage to property or loss of life. also, many WX stations, fire and police departments are active on APRS. if we had intended to push this into an actual commercially available solution, we would apply for a group call sign from the FCC and provide 3rd party message forwarding as a service. this has been a common practice in ham radio since the inception of the ARRL and is written into part 15 of the FCC. this is also exactly why and how SMS gates can exist. some programming had to be done on the server-side of the unit to handle delivering the 3rd SMS messages back through the gateway to the end-user, but it works and has been repeatedly tested. from the tower, the end-user can send and receive text messages to other people on the SMS network and it can all be done in some seriously remote areas. this was a part of our testing procedures to simulate emergency situations.

i certainly agree with you that mesh networking and long distance communications without APRS would be super rad and extremely useful. if I had unlimited time, i would even like to include some really low bandwidth modulations that are currently used in DX communications like (JST8, or FT8) on bands that aren't exclusive to ham radio (like 27 MHz! we should really use that band for something worthwhile). while these are extremely low bandwidth modulation schemes, their long distance propagation abilities are quite astounding. most likely i will branch off a different project from this one that focuses more on off-grid communication as opposed to emergency applications. i have 120 mile link that i need to establish with a wilderness monitoring site anyhow that would have to be solar powered as well. i have been doing a lot of ESP32 projects lately, and will likely do something more along what you're describing than what this project entailed. if you're interested in working on something similar, feel free to stay in contact via email.

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aaaaaa wrote 11/30/2023 at 17:38 point


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