DIY intercom project over WiFi

[deepBlue]

Hello,

I am very noobish in networking domain so I am looking for advice for following project idea…. I want to build communication system for motorcycle riders. Because quality intercom products like Sena and Cardo are expensive I am looking for diy solution. I am thinking of following:

- buying travel router with OpenWRT, like this: https://www.gl-inet.com/products/gl-ar300m/

- installing some kind of voice server on it, like Asterisk: https://forum.openwrt.org/t/how-to-...full-voip-server-asterisk-13-on-openwrt/44362

- mounting router on one motorcycle in group, and let other riders connect to Asterisk server via smartphone VOIP client applications

NOTE: system must work without internet connection.

Is it reasonable idea? If it is, how much is range of such routers (in open space)? I know I am missing much informations about this, but at least I have great will to do such project myself.

Please feel free to give any proposals and thanks in advance for answers

 

[Trip]

My initial gut reaction is you'd have potentially a fair amount of RF challenges in trying to keep cycle-mates connected while in-transit.

The architecture should be easy enough to setup with Asterisk on OpenWRT hardware. The question would be whether the you could keep the smartphone of each rider connected well enough. I would suspect everyone would have to ride within no more than 50-75 feet of the bike with the router on it. Depending on the size of the group, potentially doable, potentially not. But even if it's only a group of 3 or 4 riders, the high level of fluctuating RF send/receive paths as you're moving along may nix the whole idea altogether. Would make for an interesting proof-of-concept test, if nothing else.

 

[deepBlue]

Hi @Trip ! Thanks for constructive answer. Now I understamd what could be potentially big challenge, except the operating range. I done a little wifi range test, with equipment I currently have:

Setup:

RaspberryPi 2 B Model with Raspbian Buster Lite (kernel 4.19) installed;
- operating as wireless access point,
- with mumble server installed.
- Wifi antenna LB-LInk BL-LW05-AR5:
- Chipset: RTL8188CUS
- Speed: 150Mbps
- Gain: 5dBi
- Standards; IEEE 802.11n, IEEE 802.11g, IEEE 802.11b
- Wireless Signal Rates, With Automatic Fallback:
- 11g: Up to 54Mbps (dynamic)
- 11n: Up to 150Mbps (dynamic)
- 11b: Up to 11Mbps(dynamic)
- Frequency Range: 2.4~2.4835GHz
- Wireless Transmit Power: 17dBm (Max.)
- Modulation Type: OFDM / CCK / 16-QAM / 64-QAM
- Receiver Sensitivity (without antenna);
- 135M: -74dBm@10% PER
- 108M: -74dBm@10% PER
- 54M: -76dBm@10% PER
- 11M: -89dBm@8% PER
- 6M: -90dBm@10% PER
- 1M: -92dBm@8% PER
- Work Mode: Ad-Hoc, Infrastructure


Results:

Range was tested outdoors (without signal obstacles) using Xiaomi Mi A1 smartphone with Plumble application (Mumble client).

After 100-110 meters wifi signal becomes poor.
After 180 meters wifi signal is lost.
Within this operational perimeter (<180 m) voice is clear and without significant interruptions.

 

[sfx2000]

Hi @Trip ! Thanks for constructive answer. Now I understamd what could be potentially big challenge, except the operating range.

Sounds like a fun project

Pi2 should be good enough for your needs.

Alternate approach might be AR-150-Ext with OpenWRT and uMurmur maybe.

https://openwrt.org/docs/guide-user/services/voip/umurmur
https://github.com/umurmur/umurmur

AR-150 will use less power, more reliable over time (SPI-NOR vs. MicroSD card on the Pi), and better range perhaps
​

I like the AR150 mostly because of the ath9k driver, it's rock solid, and in the AR9331 implementation, it scales well as an access point, much better than RealTek/MediaTek client chipsets.

 

[deepBlue]

Hi @sfx2000 . Thanks for info about AR150. I have been looking for this router for quite some time for doing WiFi Pineapple project... now I have reason more to buy it
When I get it, i will do a tests and post them here.