VoIP over EDGE/3G ?

[riscbroker]

Forgive my ignorance, but is it possible (and practical) to exclude Telkom and do VoIP via EDGE/3G, both inbound and outbound, with any reliability?

 

[gmza]

If your signal is excellent and network bandwidth good in your area, then yes, it is both possible and practical.

I implemented such a solution for a call centre with 8 agents on the lines virtually 8 hours a day (predominantly inbound, but some outbound as well). Because comms were critical to the call centre and because of the poor signal where they were based (I couldn't even dial out on my cell), we got individual 3G adapters for each agent and external antennas which were mounted on the rooftop of the building, high enough up to clear the trees and neighboring buildings. Those adapters then went from 0 / 1 bar (indoors, ground floor, internal antenna) to full 5-bar (external roof-top antenna) reception strength.

But that's an extreme case. For a smaller setup, here are a couple of pointers:
1. If you can get coverage, use the following in order of preference: Telkom 3G (W-CDMA); Vodacom; MTN
2. If you don't have full strength signal, get an external antenna
3. Do NOT mix VoIP and data over the same link; this may work on ADSL but not on 3G
4. Try and get a newer 3G modem/router that supports HSUPA as well as HSDPA. This will give better bi-directional throughput and improved latency.
5. Do NOT run more than a couple of simultaneous calls per 3G connection unless you have full HSUPA (2Mb/s) upload and HSDPA (3.6Mb/s or greater) download
6. While it is possible to use regular 3G (384kb/s up/down), EDGE is impractical because of lack of bandwidth and shockingly high latency. Currently that rules out Cell C as a data carrier.
7. Make sure you buy phones which have latency resiliant adaptive jitter buffer implementations. For 3G specifically: LinkSys/Cisco are particularly good at handling high-jitter links. Snom desktop phones (but NOT the M3 cordless) are better than most, but second to Cisco/LinkSys. Yealink seem to be good, but I've only done limited testing of them over 3G.
8. Chose a service provider who is familiar with such installations. (e.g. Switch Telecom - www.switchtel.co.za)

To be frank with you, I would always recommend that you investigate options like WiMax, Neotel, iBurst, etc first. We only recommend 3G as a last resort because it often becomes costly to ensure quality (adding up costs of modems, routers, outdoor antennas, etc.).

 

[riscbroker]

Thanks gmza for your comprehensive reply. The area that my client is in does not have WiMax, Neotel, iBurst, etc so we defaulted to 3G. Perhaps it would be better to work with a WISP?

 

[warwickw]

It is possible with a WISP, just make sure your WISP is prioritizing VOIP traffic on their network.

 

[gmza]

WISP would be first prize, but 3G is fine. There are some really nice solutions now for getting excellent 3G coverage. E.g. You can set up a Mikrotik Routerboard with mini-PCI 3G card in an outdoor enclosure with self-contained antenna. The entire unit can then be wall or roof-mounted and powered via the same ethernet cable running to the house. Miro distribution sell all these components (Mikrotik, enclosure, etc). Poynting Direct have a unit that integrates all of that, but it's about R6,000. Much less complicated and almost as effective is to just get an antenna kit from Poynting Direct (about R800) and wire it back down to an off-the-shelf 3G/HSPA router like the Huawei B970 (available from MTN or Vodacom stores for around R2,000).

What area is your client in?

 

[riscbroker]

He's in George, there are a couple of WISP's there to chat to, I think we'll go in that direction

 

[gmza]

Try chat to CompuBliss - 087 550 0282. They should be able to assist with both the WISP component and installation of any Switch Telecom services in the George area.

 

[riscbroker]

Try chat to CompuBliss - 087 550 0282. They should be able to assist with both the WISP component and installation of any Switch Telecom services in the George area.

Thanks gmza, I'll give them a call

 

[s0lar]

Maybe worth to note that a decent jitter buffer on the softswitch will smooth out most glitches on the 3g network, its no secret 3g is a best effort service. Make sure you provider can give both a capable client and server for best results.

 

[Lawnchairman]

I have Skype mobile on my 3G cellphone. Would I be able to use this to minimize cellphone charge costs? Apparently cell providers are aware of this and charge a fortune cause they want you to use their network and not the data to use VOIP calls. Any comments or suggestions people?

 

[Mr K]

I have Skype mobile on my 3G cellphone. Would I be able to use this to minimize cellphone charge costs? Apparently cell providers are aware of this and charge a fortune cause they want you to use their network and not the data to use VOIP calls. Any comments or suggestions people?

You can use any voip provider if you install fring or nimzus on your phone.