Adaptive modulation based cooperative MIMO in fading channel for future wireless technology

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Addis Ababa University


With the rapid growth of multimedia services, future generations of cellular communications require higher data rates and a more reliable transmission links while keeping satisfactory quality of service. The data rate and reliability of wireless communication links can be improved by employing multiple antennas at both ends, thereby creating Multiple-Input Multiple-Output (MIMO) channels. However, the use of multiple antennas in mobile terminals may not be very practical. Certainly there is limited space and other implementation issues which make this a challenging problem. Therefore, to harness the diversity gains order by MIMO transmitter diversity techniques, while maintaining a minimal number of antennas on each handset, cooperative diversity techniques have been proposed. The main drawback of cooperative diversity is the throughput loss due to the extra resources needed for relaying. Therefore, cooperative MIMO together with adaptive modulation is used to meet the demands for high data rate and transmission reliability. This thesis presents performance analysis of a cooperative MIMO schemes with adaptive modulation for different detection techniques in Long Term Evolution network. In this scheme, each link uses MIMO Vertical Bell-Labs Layered Space Time architecture over Rayleigh flat fading channels and the cooperation strategy uses amplify and forward protocol with one relay node. For cooperative and non-cooperative MIMO, the SNR criterions to switch from one modulation order to the next for attaining maximum spectral efficiency subject (SE) at a target bit-error rate are determined. The simulation results shown that the cooperative MIMO system with adaptive modulation not only compensate for the throughput loss but also achieve considerable throughput gain compared with fixed modulation at comparable complexity. The switching criterion of optimal schemes for adaptive modulation of cooperative hybrid network with minimum mean square error (MMSE) detection, as it has a lower complexity compared to maximum likelihood (ML) detection, is also investigated. As an example, in the downlink scenario adaptive modulation based cooperative and non-cooperative MIMO network have shown optimal SE performance for and for respectively, while satisfying target BER constraint, . Key words: Adaptive Modulation, Cooperative Diversity, MIMO, LTE, SNR, Spectral Efficiency



Adaptive Modulation, Cooperative Diversity, MIMO, LTE, SNR, Spectral Efficiency