VoIP FAQ
General FAQ
Advanced FAQ
Voice over IP is an emerging technology based on open standards of IEEE, fundamentally the Internet Protocol, that allows voice data to travel across the Internet. There are many method to used this technology, the most common and well known are SIP, and H.323.
2. How does VoIP work?
Basically VoIP is a technic to send voice information in digital form in discrete packets over digital network rather than by using traditional circuit switch (PSTN). To do so we will need an analog to digital converter on sender side to translate the voice (analog signal) to digital than transmit it, and on the receiver end it will also need an analog to digital converter to covert the digital signal back to analog to the person being called can heard the voice.
Traditionally telephony carrier use circuit switching for carrying voice traffic. As circuit switching is designed to carry voice and it does it very well. Than why use IP for voice? As broadband booms, and technology evolve. People now want to communicate through various way not just voice such as email, instant messaging, video and so on. Traditional telephony can not evolve as quickly as the demand and develop new feature on circuit switch takes much time and money. IP is an already exist standard and many type of service already runs on IP, by using IP as a platform integrate service is now possible and low cost where traditional circuit may take long time to achieve.
4. What is the relationship between codec and VoIP
In order to transfer voice (analog signal) over IP it first need to be digitized. Codec is a technic to digitize analog signal to digital and vice versa. There are various speech codec available and can be used with VoIP each with it's advantage and disadvantage.
5. What advantage does VoIP can provide?
The advantage of VoIP is it can provide advance services such as joining e-mail, instant messaging, video, voice mail all together. Where current circuit switching (PSTN) can not.
Advanced FAQ
Voice quality is how well an person can hear the voice on the opposite end.
2. How are voice quality normally rated?
Voice quality is most commonly rated through a voice quality metric called the Mean Opinion Score (MOS) which is recommendation by ITU-T. The MOS is a 5 point scale where 5 represent excellent voice quality and 1 represent bad voice quality.
Codec is a algorithm which converts analog signal into digital signal and vice versa. There are three main type of waveform codec, source codec, and hybrid codec. Each consume different amount of bandwidth and provide different voice quality level.
4. What is the relation of codec and VoIP
As VoIP is a general term send voice information in digital form in discrete packets over digital network and this digital network is public network, thus there maybe other packet such data packet uses network at the same time. The codec choose is related to how much bandwidth voice packet will consume. In bandwidthwise aspect the smaller amount of bandwidth used the better. But in voice aspect the higher quality the better.
5. Which codec should I choose?
As which codec choose is depending on what codec is supported on both end of the VoIP host. Generally a codec with low bandwidth consumption and high voice quality is a good codec .
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