Energy Analysis of Large Antenna and Spatial Modulated System in Different Fading Channels

Abstract

In the last ten years we have seen significant advances of multi-user MIMO (MU-MIMO) in wireless communication. MU-MIMO is now being introduced in several new generation wireless standards (example LTE-Advanced, 802.16 m). The number of users is increasing with more and more applications. At the same time high data rates and communication reliability are required. Therefore, MU-MIMO systems have to satisfy the three main requirements i) serving many autonomous users in same time-frequency resource ii) having high data rate and communication reliability iii) less energy consumption/radiation. These are seemingly contradictory requirements. Since the more users are served, the system will suffer from more interference and for achieving high data rate more transmit power is required. MU-MIMO with large number of antennas located at the base station (say tens or hundreds), the channel vectors are nearly orthogonal and hence multi-user interference can be significantly reduced. As a result many users can be served with high data rates. In particular the transmit power is reduced by the number of antennas present at the base station or by the square-root of the number of antennas located at the base station depending on the CSI and fading technique used. In this thesis the energy efficiency analysis for uplink MU-MIMO using linear receivers in Rayleigh and Ricean fading channels with scaled and un-scaled transmit power is done. In analysis it is assumed that each user has single antenna for transmission and base station has large number of antennas (100 and 200) with imperfect CSI. We also consider transmit power, circuit power and loss factors for the analysis. In Rayleigh fading channel the tradeoff is observed between energy and spectral efficiency for MRC and ZF receivers considering transmit power, transmit and circuit power and transmit, circuit power and loss factors for scaled and un-scaled transmit power. It has been observed that considering circuit power and loss factors high energy efficiency is obtained with less number of antennas placed at the base station. In Ricean fading channel the tradeoff is also observed between energy and spectral efficiency using MRC receiver considering transmit and circuit power, transmit, circuit power and loss factors for un-scaled transmit power. High energy and spectral efficiency is obtained in Ricean fading channel. With scaled transmit power the spectral efficiency reduces in comparison

to the un-scaled transmit power. The energy efficiency is also analyzed by variation of transmit power in dB using imperfect CSI in Rayleigh (MRC and ZF receivers) and Ricean (MRC receiver) fading channels. At low transmit power MRC receiver performance is better in comparison to ZF receiver and at high transmit power ZF receiver performance is better in comparison to MRC receiver. Spatial Modulation technique is also analyzed using MRC receiver with imperfect CSI for single and multi users having multiple antennas for transmission and large number of antennas at base station, and radio frequency chain equal to the number of users in Rayleigh and Ricean fading channels. Energy efficiency and spectral efficiency is analyzed using spatial modulation and results are compared with single and multi users each having single antenna for transmission. The analysis is done for single user having 4 and 8 transmission antennas and 4 users each user having 4 and 8 transmission antennas and base station has 100 antennas and it has been concluded that single user having 4 and 8 antennas is preferred in comparison to single user having single antenna for transmission. High energy efficiency is obtained using spatial modulation in Ricean fading channel in comparison to user having single antenna for transmission. It has also been concluded that energy efficiency and spectral efficiency increases as users have large number of antennas for transmission and less number of radio frequency chains.