الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
In previous 3GPP standards’ releases, the circuit switched Adaptive Multi Rate (AMR) voice codec has proven robust performance under different radio channel conditions. With the 3GPP Release 8 Long Term Evolution (LTE) standards, the circuit switched domain is cancelled, making VolP the only way to carry voice. Despite that VolP codecs are well developed for intern et applications, these codecs are not designed to adapt according to the radio channel conditions, as in the case of AMR. In this work a novel channel adaptive technique is introduced suitable for VolP codecs operating under the L TE radio environment (eUTRAN).
With the newly proposed Adaptive Multi Lane (AML) approach, the system is to transmit I, 2 or 4 streams of speech frames in parallel lanes. The number of lanes is adaptable according to the encountered radio channel conditions. Each lane has a different fractional speech frame delay increasing the receiver’s probability getting out of fading dips. The AML technique has been modeled and simulated over OMNET++ ver4.1 including the INET framework and VolP tool extension. The VolP tool has been modified to implement the lane selection algorithm. The resulting speech quality was evaluated using the ITU P.862 Perceptual Evaluation of Speech Quality (PESQ).Deploying AML
. with optimized parameters, simulation results show improvement in the average PESQ Mean Opinion Score (MOS) readings exceeding 40% compared to the normal single path model.
In this thesis, the current challenges of carrying human speech over L TE networks are discussed together with a brief presentation of the latest advances in this regards. The evolution of 2G cellular systems to HSP A and L TE, including explanations of their corresponding radio environments and channels’ are then detailed. This is followed by an in depth description of the new Adaptive Multi Lane technique algorithm and proposed deployment scenarios. Moreover, the simulation platform and ITU standard objective speech quality assessment tools are discussed and compared. Consequently, the simulation results’ plots are listed and evaluated. The AML optimal parameters are then selected in order to maximize the resulting overall speech quality. Simulation has shown that AML is a useful technique for improving VolP codecs performance, in modern cellular systems, with efficient radio resources’ utilization.