Improved Link Adaptation Modelling For Lte/Lte-A Networks
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Date
2017-02
Authors
Salem, Ali Abdulqader
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Currently, data carried by wireless network devices are merged with the multimedia system such as video streaming. Therefore, the quality becomes a challenge in broadband wireless networks as it is influenced by many issues such as mobility movement and path loss, which affects the channel efficiency negatively. Long Term Evolution (LTE) and Long Term Evolution-Advanced (LTE-A) are types of broadband wireless networks. In LTE/LTE-A, Shannon capacity formula is unable to accurately predict the standard peak data rate capacities. Researchers proposed “Alpha Shannon capacity formula”, but without remarkable improvement regarding capability. Thus, a part of this thesis proposes a modified Alpha Shannon formula for better prediction of the LTE peak data rate. Results have shown that the proposed formula has a lower Relative Error (RE) with percentage 2.8% in both Single-Input and Single-Output (SISO), and Multiple-Input and Multiple-Output (MIMO) modes compared to the “Alpha Shannon”, which is 31.8 %. Consequently, the formula is used later to improve the estimation of link adaptation for achieving better network performance. In LTE/LTE-A, the link adaptation must be optimized according to the characteristics of the physical and MAC layers to enhance the channel efficiency and throughput. This thesis also proposes two link adaptation models; the first is Cross-Layer Link Adaptation (CLLA) model, which overcomes the accuracy issue of adaptive modulation in the existing system and improves the channel efficiency. The second model is Markov Decision Process over CLLA (MDP-CLLA) model, which improves the optimal modulation’s selection more accurately compared to the CLLA model and the existing system. The effectiveness of the proposed models is investigated using Matlab and Simulink environments. The experiments for evaluating throughput, channel efficiency, packet loss, and phase productivity are done for different packet sizes of SISO and MIMO modes over Rayleigh and AWGN. For the Rayleigh channel, CLLA model improves the total phase productivity by 4.25 % to 42.02 % for different packet sizes compared to the existing system. In addition, MDP-CLLA achieves better improvement of the total phase productivity by 6.7 % to 42.02 % for different packet sizes compared to the existing system and up to 15.01 % compared to CLLA model. The overhead was evaluated to determine the optimal packet size to the certain modulation during link adaptation. The results have shown that over Rayleigh channels, packet sizes of 1000, 2000, and 8000 bits are the optimal ones to be adapted during the adaptive modulations QPSK, 16-QAM, and 64-QAM respectively in the existing system and CLLA model. Whereas, in MDP-CLLA model, the 2000, 4000, and 1000 are the optimal ones. MDP-CLLA model improves the overall performance compared to CLLA model and existing system as it uses the average reward to identify the optimal solution.
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Keywords
Improved link adaptation modelling , for Lte/Lte-A networks