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.