Proposed Modifications in ETSI GSM Full Rate Speech Codec in line with bitrates of GSM EFR Speech Codec and its Objective Evaluation of Performance using MATLAB

Today, the primary constrain in wireless communication system is limited bandwidth and power. Wireless systems involved in transmission of speech envisage that efficient and effective methods be developed (bandwidth usage & power) to transmit and receive the same while maintaining quality-of-speech, especially at the receiving end. Speech coding is a technique, since the era of digitization (digital) and computerization (computational and processing horsepower DSP) that has been a materialofresearch for quite sometime amongst the scientific and academic community. Amongst all elements of the communication system (transmitter, channel and receiver), transmission channel (carrier of information/data, also called the medium) is the most critical and plays a key role in the transmission and reception of information/data. This paper proposes some modifications in the Long Term Gain and selection of Grid position sections of 13kbps GSM Full Rate coder so that it can be mapped to bitrates of GSM Enhanced Full Rate at12.2kbps. Here, Objective analysis is carried out on a proposed system using MATLAB to evaluate its performance and the results obtained are then compared to the results of GSM Full Rate coder. Proposed coder, at bitrates of 12.2 kbps, provides moderately low computational complexity [1] as its implementation is with reference to GSM full rate coder rather than using Algebraic Code Excited Linear Prediction (ACELP) algorithm in case of standard GSM EFR coder but it offers small degradation in speech quality compared to standard GSM EFR coder. In comparison with standard GSM Full Rate coder, here the proposed coder offers other benefit of saving of 0.8kbps which can be useful for better error protection during channel coding while also provides satisfactory results for the parameters of Objective analysis.