| A VoIP PBX System is often associated with | | | | Apart from delays, another problem associated with |
| bandwidth savings and reduced cost. However, since | | | | VoIP networks is jitter. Jitter is caused by the |
| this is a relatively new technology, there are many | | | | inter-packet delay in the network. This causes |
| quality related issues to be dealt with. Many of these | | | | distortion in the talks. Jitters can be minimized by |
| issues arise owing to the use of packet switched | | | | holding the packets until the slowest packets arrive at |
| networks. | | | | the destination. This can however increase the delay in |
| A significant problem that is associated with a VoIP | | | | playing the voice. Various approaches are being tried |
| system is the delay in packet transmission. This delay | | | | at to compromise between delays and jitters. |
| results in echo and talk overlaps. An echo is usually | | | | Another severe problem affecting a packet network is |
| caused if the round trip delay of the signal from the | | | | packet losses. IP networks usually have high |
| destination back to the source is more than 50 | | | | incidences of packet loss as compared to ATM |
| milliseconds. In packet switched network, given the | | | | networks. During peak traffics, the problem of packet |
| number of routers and networks a voice packet has | | | | losses can be enormous. Data packets can be |
| to traverse, the delay can be considerable for long | | | | retransmitted, but in case of voice packets a different |
| distance calls. Modern VoIP systems therefore | | | | approach is required. Some of the solutions proposed |
| implement echo control and cancellations methods to | | | | for solving this problem include replaying the last |
| deal with the problem. Another problem caused with | | | | packets until new packets arrive, sending redundant |
| packet delays is talk overlaps. This problem occurs if | | | | information to compensate for the loss, and a hybrid |
| the packet delay in any direction exceeds 250 | | | | approach combining the previous two methods. |
| milliseconds. | | | | |