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 that are powerful enough to allow an Internet connection through wireless networks, with all that 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 latest applications are those that allow sending and receiving voice packets that would be the basis of mobile VoIP.
To be able to talk via VoIP through a mobile terminal, it must be equipped with a sufficiently powerful processor that allows a wireless connection to the Internet . Whether it is Wi-Fi , HSDPA , WiMAX or EV-DO rev A, the latter is more specific for mobile telephony and the EVDO rev A variant allows faster package creation for both the uplink and the downlink. .
To establish, modify and terminate connections between two users, the SIP protocol is used . In addition, it is able to determine the location of the users thus allowing more mobility. The SIP protocol is complemented with the RTP protocol , this is the one that transports the voice data packets, that is, the conversation that we send through our digitized mobile terminal and packaged through the IP protocol .
The voice must be digitized and encoded so that it can be sent through the IP protocol . Codecs are used such as G.711, G.722, G.723, G.728 or G.729. These compress the audio data to use less bandwidth in the transmission. In this way many more connections are allowed in the same channel.
When a connection has been established between two users who may be in motion, they may 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 it requires a certain time. The operation is similar to the handover used in conventional mobile telephony.
In addition to the delay introduced by the change of the coverage area from one base station to another, there are others: Delays introduced by the processor when coding, compressing and packaging the data to send them through the IP network. Delays that involve the use of IP protocol such as packet loss, sending erroneous packets, queues of full nodes or network congestion.
The fact of using the IP protocol to communicate is a great cheapening of calls, especially at the international level, since to have internet you only have to pay a fixed fee and this allows access to all the world where there are connections with IP protocol .
It is expected that as this technology improves, more and more users will use mobile VoIP. The main reasons are that the call time does not mean an increase in the cost of this and international calls can be made, also for the same price.
Due to the large number of operations that the processor must perform in order to make a connection via IP protocol , mobile terminals ready to make this type of connection are needed.
The smartphones are capable of performing the necessary operations as 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 these.