According to abbreviationfinder, VoIP stands for Voice over Internet Protocol. Mobile VoIP is the voice over IP protocol (VoIP) applied in mobile phones. This means that the voice signal that is transmitted in a communication between two mobile terminals travels through the Internet using an IP protocol. With the latest advances in mobile telephony, it has been possible to make terminals powerful enough to allow an Internet connection through wireless networks, with all that this entails: surfing the Internet, sending and receiving e-mails, downloading different data files and use instant messaging applications either by text, voice or video. These last applications are the ones that allow sending and receiving voice packets that would be the basis of mobile VoIP.
Wireless networks
In order to be able to speak via VoIP through a mobile terminal, it must be equipped with a processor powerful enough to allow a wireless connection to the Internet. Whether by Wi-Fi, HSDPA, WiMAX or EV-DO rev A, the latter is more specific to mobile telephony and the EVDO rev A variant allows faster creation of packets for both the uplink and downlink.
Protocols
To establish, modify and terminate connections between two users, the SIP signaling protocol is used. In addition, it is capable of determining the location of users, thus allowing more mobility. The SIP protocol is complemented by the RTP protocol, this is the one that transports the voice data packets, that is, the conversation that we send through our mobile terminal digitized and packaged using the IP protocol.
Coding
Voice must be digitized and encrypted so that it can be sent over the IP protocol. Codecs such as G.711, G.722, G.723, G.728 or G.729 are used. These compress the audio data to use less bandwidth for transmission. In this way, many more connections are allowed in the same channel.
Mobility
When a connection has been established between two users who may be on the move, they can change the coverage area of the base station that allows them to connect. When this happens a new connection with the new base station must be re-established and takes some time. The operation is similar to the handover used in conventional mobile telephony.
Time delay
In addition to the delay introduced by changing the coverage area from one base station to another, there are others: Delays introduced by the processor when encoding, compressing and packaging the data to send it through the IP network. Delays caused by the use of the IP protocol such as packet loss, sending erroneous packets, full node queues or network congestion.
Advantages
The fact of using the IP protocol to communicate supposes a great reduction in the cost of calls, especially at an international level, since to have internet you only have to pay a fixed fee and this allows access to the whole world where there are connections with IP protocol.
It is anticipated that as this technology improves, more and more users will use mobile VoIP. The main reasons are that the call time does not imply an increase in its cost and international calls can also be made for the same price.
Applications
Due to the large number of operations that the processor must carry out in order to make a connection via the IP protocol, mobile terminals are needed to be able to make this type of connection.
Smartphones are capable of performing the necessary operations since they are equipped with increasingly powerful processors. VoIP transmissions have already been achieved through these types of mobile terminals through applications such as Skype for them.
