VoIP Technology

Web pages use Transmission Control Protocol (TCP) transfers data from one system (a PC) to another (a server) and similarly, VoIP uses User Datagram Protocol (UDP) and Real-time Transmission Protocol (RTP) to deliver audio and video over the Internet, making it relatively faster than TCP.

When a call is made through VoIP, it begins by converting your analogue voice signal to a digital signal. This process is carried out by an Analogue-to-Digital Converter (ADC), a device that converts analogue data into small chunks and assigns a numerical value to the data pieces. The broken down chunks are called packets, which contain the audio data, origin and destination of the packets. To ensure a smooth flow of data, the digitized audio data is compressed using a coder-decoder (CODEC). During data transformation there is a certain amount of loss in audio quality. Codecs significantly convert and compress the data into digital format for transformation and then uncompress the data for replay, maintaining the audio quality. The data is encapsulated in layers to ensure proper delivery when sent over the Internet.

Data packets have to be delivered in the right sequence to their destination. RTP provides the information about the sequence of the packets and has the capability to deliver the packets if they do not arrive in time. If the software delays or fails to reassemble the data packet in time there will be subsequent loss in the audio stream.

Once the data is received at the destination the codec reassembles the jumbled data packets and the data is uncompressed. The analogue telephone adapter converts the digital audio format to analogue allowing the person to receive the call.

When reassembled, if some packets between each sample have been lost, the amount lost is so minute that it cannot be detected by the human ear and there is still enough information to make the conversation legible. The amount of data loss depends on your Internet connection and the distance between the origin and destination. To have high quality audio reception you need to have a broadband Internet connection.