As the use of a mobile phone is getting cheaper by the day, the amount of data being transferred through wireless with every call goes on increasing. Speech coding techniques have been used by commercial mobile service providers to create a flexible voicing structure to allow natural sounding speech to be transmitted over long distances and making the sound robust to the presence of acoustic background noise. After over three decades of research, the international standards adopted by the telecom industries uses a compression technology
(between 64 kbps to 2.4 kbps) to provide services while maintaining sound quality.

Prof. Preeti Rao of the Department of Electrical Engineering and her students have patented a new method that can further reduce the data bits to very low bit range (under 2 kbps) without compromising the speech quality. The current compression method uses a frame-based fixed parametric speech coder whereby either by managing the frame size, predicting the interframe correlation or encoding only selective frames together with interpolation techniques, desired compression rates are achieved. The proposed patented method uses a synergistic approach of prediction and encoding. Their invention is able to provide a good "communication quality", fixed-rate speech compression method that is capable of being ported to an appropriate hardware platform to obtain an improved speech compression system while minimising losses in sound quality.

The benefits of this invention are many and the application in telecommunications is only limited by its user. This invention can be adopted by defense organisations as a standard for secure communication replacing previous systems that may be proprietary or outdated. Mobile service operators and telecommunication service providers can provide connectivity in rural India with minimum expenses as the invention can be reasonably easily implemented on the current hardware systems. With reduced bit rate, internet telephony can be used for long distance calls as the home broadband technologies in India start to match up with their western counterparts.

Indian patent application no. 273/MUM/2003 Patent grant no. 205439
Inventor: P Rao