- This topic has 1 reply, 1 voice, and was last updated 18 years, 2 months ago by Patrick Gannon.
29th January 2003 at 17:59 #23435Neil MGuest
I use the earthlink sat. connection – uploads are a little sketchy, usually 35 or so… I’ve been trying to make net2phone work with this… when I dial out via my pc to a standard phone, I can hear the other party cleary… but my voice gets buried on static & what sounds like feedback.
Is this likely to be the sat.conn… or net2phone… or the headset… or something else?
Neil30th January 2003 at 19:23 #23436Patrick GannonGuest
The satellite connection is the problem.
The Earthlink satellite solution is provided by DirecWay. This consumer class broadband satellite service uses old technology and it will not support VoIP satisfactorily. This is indicated on Hughes’ web site. The primary reasons are:
1. The contention method used is similar to shared Ethernet, where multiple stations attempt to transmit when they have data to send. This causes collisions, the stations back off, wait a random time and retransmit. This lack of transmission consistency leads to excessive jitter, and it is highly inefficient. That’s why you only get 35 Kbps or so, on average, when 128 Kbps is advertised.
2. The frame length on DirecWay is 250 ms. That means voice is only sampled 4 times/ second. That’s not enough to provide decent voice quality.
There are enterprise class broadband satellite systems available that deliver clear business class VoIP, but they are more costly and generally require slightly larger dishes.
Satellite systems have been used for decades to deliver analog voice all over the globe, very reliably and with high quality – albeit a bit of latency. To send VoIP over satellite can be performed just as reliably and clearly, but it requires that the customer inquire carefully about the satellite provider’s technology.
Dedicated bandwidth solutions, called SCPC work fine, but are very expensive.
Shared bandwidth solutions must have a deterministic bandwidth allocation method and shorter frame length.