Human ear cannot generally perceive mouth-to-ear delay under 200 milliseconds.
If you perceive a delay during call, chances are that is between 300 and 500 milliseconds, which is perfectly acceptable to have a conversation on phone.
Higher delay in the order of 1-2 seconds (such as satellite communications) makes phone call more difficult, but still doable with some practice.
There are two main causes for perceivable delay using EVSS:
- network jittering: audio data packets arrives irregularly, with variable delay, depending on network issues and structure. PrivateGSM is constantly measuring jittering and automatically adapts to it, adding a delay buffer, in order to produce a constant and smooth audio flow
- network latency: audio data packets flows from caller PrivateGSM -> PrivateServer -> called PrivateGSM and in the opposite direction. If both parties are far from PrivateServer the transmission of audio data will get a delay.
|2G||500 - 2000 ms|
|EDGE||2.5G||200 - 500 ms|
|3G||3G||100 - 300 ms|
|HSDPA||3.5G||100 - 300 ms|
|LTE||4.G||100 - 200 ms|
While GPRS provides enough bandwidth for PrivateGSM to play crystal-clear audio, it exhibits a high jitter, which introduces a perceivable delay.