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Adaptive Modulation, Adaptive Power Allocation, and Adaptive Medium Access
Published in Mohamed Ibnkahla, Wireless Sensor Networks, 2017
The receiver is responsible for receiving data, demodulating the received information, and estimating the CSI after the wireless channel. Hence a feedback channel is further required so that the estimated CSI can be fed back to the transmitter. Normally there might be estimation errors and delays involved in this feedback process, which negatively affects the transmitter decisions. However, we assume that the channel estimation is perfect for the receiver and the delay from the feedback channel is negligible.
Realization of New Radio 5G-IoT Connectivity Using mmWave-Massive MIMO Technology
Published in Parag Chatterjee, Robin Singh Bhadoria, Yadunath Pathak, 5G and Beyond, 2022
Priyanka Pateriya, Rakesh Singhai, Piyush Shukla, Jyoti Singhai
Figure 6.4 shows the SU mmWave-mMIMO system with hybrid precoding. In this system, the BS is furnished with Nt antennas for transmitting Ns data streams simultaneously to a UT equipped with Nr antennas. Multi-stream transmission is enabled if the BS is employed with NtRFradio frequency chains so that Ns≤NtRF≤Nt. The BS employs a digital precoder D of dimension NtRF×Ns utilizing its NtRF radio frequency chains, followed by an analog beamformer A of dimension Nt × NtRF utilizing analog circuits like PSs. The X can be expressed as: X=ADs where s is the message vector of dimension Ns × 1 prior to precoding with normalized power of E(ssH) = (1/Ns)INs. The y of dimension Nr × 1 can be expressed as: y=ρHADs+n In this realistic system, the receiver can determine the CSI through training and afterwards feed the CSI back to the transmitter.
Performance of a multihop cognitive radio network with diversity under imperfect CSI
Published in International Journal of Electronics Letters, 2023
S. Mondal, D. Bepari, S. Biswas
In practical, due to channel estimation errors, feedback delay etc., achieving perfect CSI is quite difficult. The imperfect CSI of the secondary transmitter-to-primary receiver link has been considered to make analysis more realistic. The imperfect CSI can be modelled as follow (Zhang et al., 2012):