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BSchorr
@24.121.188.x

BSchorr

Anon

Local VOIP Conference Calls - DIY?

I have a project I'm working on and I think VOIP might be a solution.

I need to create a short-range (300 yards or less) intercom type system - voice only. The users need to be mobile and will all have some sort of headsets and there will be a "base station" that can be a laptop or a Raspberry Pi or something like that. I'm hopeful the whole thing will run over 802.11n.

I was envisioning this as a small VOIP system that hosts "conference calls" for the participants. There would likely never be more than half a dozen participants (total) and it would be great if there could be 2-3 conference calls going on that they could select from. It does not need to be able to connect to the PSTN or Internet - this is entirely self-contained.

The users would all connect to the "conference calls" around the same time, the calls would stay open for 2-3 hours probably, then it would all get broken down at that point.

I was considering Asterisk on a Raspberry Pi or maybe Mumble? Perhaps the clients would be a VOIP softphone running on iOS or Android? But I'm getting stuck a little on what the clients would be or how it would all come together.

Anybody already try doing this? Any suggestions or tips?
w1ve
Premium Member
join:2007-12-28
Hancock, NH

w1ve

Premium Member

Asterisk meetme conferencing would work fine; something like the Beaglebone Black would be able to host that many participants without issue. PBX-
in-a-Flash builds for beaglebone would take about 15 minutes to install. Run a Wifi hotspot that all the participants would log in to.. give asterisk a fixed IP in the address space, and give it a DNS name that makes sense. The clients could be SIP phone clients for IOS or Android -- there are plenty around.
Stewart
join:2005-07-13

Stewart to BSchorr

Member

to BSchorr
For 300 yards, you may need quite a few access points, depending on the site (open field, factory floor, warehouse, hotel, etc.) The system may need careful setup to avoid audio gaps or dropped calls when a user roams from one AP to another.

If you already have Wi-Fi installed in the target area, set up an app on a smartphone and walk around while talking. For this purpose, you could use a SIP app with a commercial VoIP provider, though a quick test with Skype or Hangouts should give similar results. Also, run a speed test in several locations -- you'll need ~1 Mbps up and down to handle 12 users on the same AP.
kaila
join:2000-10-11
Lincolnshire, IL

kaila to BSchorr

Member

to BSchorr
I agree with Stewart, the networking piece will be the biggest challenge. Regardless if this is over an open space or building-to-building type deployment, you're looking at backhauling to get AP's close enough to the users. Probably wireless as the radius of 300yds (~150m) exceeds ethernet limits, unless you add equipment in-between (meaning you'll need power available at that point).

At even 50yds in an open space, it starts to become a challenge for jitter sensitive real time applications using mobile devices as they tx back to AP's- remember these are low powered, non-fixed, with non-directional antennas- and users will often have their head between the device and AP.

Bschorr
@24.121.188.x

Bschorr to Stewart

Anon

to Stewart
said by Stewart:

For 300 yards, you may need quite a few access points, depending on the site (open field, factory floor, warehouse, hotel, etc.) The system may need careful setup to avoid audio gaps or dropped calls when a user roams from one AP to another.

If you already have Wi-Fi installed in the target area, set up an app on a smartphone and walk around while talking. For this purpose, you could use a SIP app with a commercial VoIP provider, though a quick test with Skype or Hangouts should give similar results. Also, run a speed test in several locations -- you'll need ~1 Mbps up and down to handle 12 users on the same AP.

Upon reflection it's probably more like 200 yards (largely outdoors; we'd even have line-of-sight most of the time) and it's not omni-directional. Basically it would be linking two groups of people and while the groups might be as far as 200 yards apart (and sometimes barely 50) the people within the group would be relatively close together.

Skype won't work because we're not likely to have Internet access (and if we did it would rarely be fast Internet access). That's why I was hoping for some sort of self-contained VOIP server that would run on a laptop or Raspberry Pi. These groups only need to communicate with each other at the site.
Stewart
join:2005-07-13

Stewart to BSchorr

Member

to BSchorr
In an open field 200 yards in diameter, you could put up an AP with an omnidirectional antenna on a pole in the center and it will work fine. Or, if there's a wooden house near the center, one AP on the roof will probably be adequate. But if you are dealing with concrete and steel buildings, you'll need at least one AP in each, plus one or more APs to serve the outside.

I had suggested Skype only as an easy way to evaluate the suitability of existing Wi-Fi, not realizing that it may not be connected to the Internet. In that case, configuring SIP apps on two phones to call each other directly should be fairly easy and a good test.

If push-to-talk and the possibility of two people on a channel trying to talk at the same time are not serious issues in your application, some cheap FRS radios with headsets may be an easier and more robust solution.