Современные информационные технологии/3. Программное обеспечение

Doctor of Physical and Mathematical Sciences Baymankulov A.T.

MA student Urazova Elmira Kalkamanovna

Kostanai State University named after A.Baitursynov

Internet telephony solution for mobile devices running OS Android

It is an open secret that in the modern world, new technologies replace each other at the speed of sound. Nowadays, laptops have replaced computers; smart phones have replaced phones and so on. Twenty years ago computers were huge, weighing more than ten kilograms, now the owners of electronic devices can enjoy the lightest ultra-thin laptop, whose thickness is no more than the thickness of the usual magazine. Electronic upgrades didn’t leave behind phones, huge and ugly handsets for just a few years turned into a quick and convenient device. Also with them functions are changing, day by day a huge number of applications both for computers and for mobile phones appear in the world. Every time the mobility of devices is growing exponentially. Voice communication over the Internet became familiar for PC users long ago, but for mobile devices qualitative decisions until recently did not exist. However, the development of advanced mobile technologies, namely the emergence of mobile devices with fast access to the Internet and working under operational system Android, opens up new possibilities. The official release of the first smart phone HTC Dream (G1), under control of OS Android, to the U.S. market was on 22 October 2008.

After the appearance of first devices under control of Android, it became possible to give the user the ability to use Internet telephony as well as GSM telephony. Broadband Internet access, multi-tasking of operating system enabled the user to forget about the problems associated with the Internet connection. Before Android the most convenient applications for Internet telephony offered iPhone OS, but with its limited multitasking, you can not use several documents, and it means, for example, inability to read documents and receive calls simultaneously. Anyway there are several solutions to provide Internet telephony for Android, but they all have significant restrictions on use.

At the moment, the goal of humanity is to improve the existing solutions for OS Android Internet telephony. For the study I have decided to create a SIP application for Android. For example, the application should not be inferior to other applications in sound quality and speed, and work in the background, without setting the user of a communicator a time limit. For user convenience, the application must be able to carry out switching a call type from SIP to GSM and back - so-called "Handover". That is, when there is a wide Internet channel, call goes to SIP, and if the width of the channel starts not to sufficing, there is a call switching from SIP to GSM imperceptibly for the user. As soon as the channel width is sufficient again, there is a switch back to the SIP. I would also like to note that most applications do not work on all versions of OS Android, so this problem should be fixed.

SIP (Session Initiation Protocol) – standard of setting and completion of Internet session, that include exchanging of multimedia content (video - and audio conferencing, instant messaging). In the Open Systems Interconnection model SIP is a network protocol of application layer.

The protocol describes how a client application (for example, MC Client) requests a start of connection from another, perhaps physically remote client, situated in the same network, using its unique name. The protocol defines the way of coordination between clients on opening exchange channels, based on other protocols that can be used for direct data transmission (for example, RTP). It is possible to add or remove these channels within the specified session, and also the connection and disconnection of additional clients (that is participation in an exchange more than two sides — conference communication is allowed). The protocol also defines the order of the session end. In the basis of the protocol lye such principles as simplicity, because it includes only six methods, independence of tranportny level, personal mobility of users, network scalability, integration of existing Internet protocols into a stack and interaction with other protocols of the alarm system.

To implement SIP telephony application for Android, modules would be written, libraries of Android would be used. All the tasks above are only minor, in the future, it is planned to introduce global changes, such as, the ability of textual chat in a client, as well as the possibility of making video calls. To reduce the traffic between a client and a server it is planned to use a more advanced audio codec iLBC. It is also planned to make the traffic more secure by implementing TLS to encrypt SIP messages and implement SRTP protocol instead of unprotected RTP for sound transmission. It will much more simplify the life of simple users of communicators.