Joint power loading of data and pilots in OFDM using imperfect channel state information at the transmitter

Abstract- The search for optimality in the design of channel precoders and training symbols in block processing communication systems is one of paramount importance. Finding the best tradeoff in terms of power distribution between information and pilot symbols for frequency selective channels, when channel estimation via feedback is available, however, has not been fully addressed. In this paper, we solve the problem of finding the optimal power distribution between pilots and data symbols in the mean-square-error (MSE) sense when a delayless error-free channel feedback path is available to the transmitter. The novel approach adaptively designs the optimal precoders and training vectors based on the frequency domain estimates of the channel

A robust joint linear precoder and decoder MMSE design for slowly time-varying MIMO channels

The joint linear precoder and decoder Minimum Mean Squared Error (MMSE) design represents a low complexity yet powerful solution for spatial multiplexing MIMO systems. Its performance, however, critically depends on the availability of timely Channel State Information (CSI) at both transmitter and receiver. In practice, the latter assumption can be severely challenged, due to channel time variations that lead to outdated CSI at the transmitter. State-of-the-art designs mistakenly use the outdated CSI to design the linear precoder and rely on the receiver to reduce the induced degradation. In this paper, we propose a robust Bayesian joint linear precoder and decoder solution that takes into account the uncertainty on the true channel given the outdated CSI at the transmitter. We finally assess the robustness of our design to channel time variations through Monte-Carlo analysis of the system’s MMSE and average Bit-Error Rate (BER) performance. 1

MIMO Systems

In recent years, it was realized that the MIMO communication systems seems to be inevitable in accelerated evolution of high data rates applications due to their potential to dramatically increase the spectral efficiency and simultaneously sending individual information to the corresponding users in wireless systems. This book, intends to provide highlights of the current research topics in the field of MIMO system, to offer a snapshot of the recent advances and major issues faced today by the researchers in the MIMO related areas. The book is written by specialists working in universities and research centers all over the world to cover the fundamental principles and main advanced topics on high data rates wireless communications systems over MIMO channels. Moreover, the book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity