.99} and {0.9, 0.9, 0.9} cases. For Rth = 2 bps/Hz, the throughput of the system saturates to ~0.7 at 22.5 dB approximately for {0.99, 0.99, 0.99} case, whereas for imperfect CSI case of {0.9, 0.9, 0.9}, system throughput saturates to <0.3 at ~30 dB. It illustrates the adverse effect of both imperfect CSI and the high data rates over the system performance. 6 Energy Harvested Device-to-Device MIMO Systems for Beyond 5G. {0.99,0.99,0.99}-a:00.2 {0.99,0.99,0.99}-a=0.5 {0.99,0.99,0.99}-a=0.7 {0.95,0.95,0.95}-a=0.2 {0.95,0.95,0.95}-a=0.5 {0.95,0.95,0.95}-a=0.7 Transmit SNR (dB) Fig. 6.4 2 X 1 X 2 MIMO ACs: Outage probability VS SNR for different a values [13] 6.4 Impact of Outdated CSI In the earlier section, the impact of imperfect CSI over the SWIPT-enabled D2D communications is analyzed. In this section, the outdated CSI and its affects are considered in the analysis. As all the nodes are multi-antenna nodes, the effects of outdated CSI over antenna selection and the EH are important metrics of concern. SWIPT-enabled D2D communications in the presence of feedback error are also highly motivated. Hence, in this section, we present the effects of feedback delays and EH in the analysis of an overlay non-regenerative D2D MIMO relay system over generalized Nakagami-m fading channels. System performance is investigated through outage probability and asymptotic outage probability expressions. For a delay-limited transmission mode, throughput of the system is presented. 6.4.1 Mathematical Modeling To model the feedback errors, consider a scenario where the CSI received at the transmitter is outdated due to the time-varying nature of the channel when fed back from the receiver. Thus, the resultant CSI at the transmitter is outdated and results non-zero feedback link delay. Let's consider hpo an estimated channel vector to be P. Shaik and V. Bhatia =1bps/Hz-{ 0.99, 0.99, 0.99}-Ana. Rth=1bps/Hz-, 0.99, 0.99, 0.99}-Asym. Rth=2bps/Hz-{, 0.99, 0.99, 0.99}-Ana. Rth==2bps/Hz-{, 0.99, 0.99, 0.99}-Asym.. 0.9, 0.9, 0.9}-Ana.. R+ =1b