Combined channel estimation and PAPR reduction technique for MIMO–OFDM systems with null subcarriers

Abstract

In this article, we address the challenges regarding the provision of channel state information as well as reducing peak-to-average power ratio (PAPR) of a multiple input multiple output orthogonal frequency multiplexing (MIMO-OFDM) system. The mean squared error (MSE) of the channel estimate is adopted as the optimization criterion to design pilot symbols for channel estimation in MIMO-OFDM systems with null subcarriers. We design the placement and power distribution to the pilot symbols for multiple transmit antennas to minimize the MSE of the least square (LS) channel estimates. To reduce interference of the pilot symbols transmitted from different antennas, an algorithm to guarantee that pilot symbols are disjoint from any other transmitter pilot set is proposed. To efficiently reduce the PAPR of the MIMO-OFDM signals, a method that mixes dummy symbols and phase information of the pilot symbols is presented. Simulation results based on IEEE 802.16e are presented to illustrate the superior performance of our proposed channel estimation method over the existing standard and the partially equi-spaced pilot symbols. We also demonstrate that, by mixing the dummy symbols and phase information of the pilot symbols, the PAPR of the MIMO-OFDM signals can significantly be reduced.

Computationally efficient variational Bayesian method for PAPR reduction in multiuser MIMO ‐ OFDM systems

“…To facilitate the development of the FITRA [15], in order to minimize the largest magnitude of all antennas' signals, (12) can be restated in Lagrangian form as min x λkxk 1 þ ky À Hxk 2 2 ;…”

“…To frame the PAPR reduction as a sparse signal-recovery problem, the equality constraint in (12) can be relaxed to the following form…”

Low Complexity Pilot Allocation Scheme for a Large OFDM Block with Null Subcarriers

“…Differently 2 Wireless Communications and Mobile Computing from the 3rd order polynomial-based pilot allocation, the 5th order polynomial-based pilot allocation performed well with both the OFDM block sizes, 512 and 1024. In [13], the 5th order polynomial-based pilot allocation was also applied to MIMO-OFDM systems. However, the 5th order polynomial-based pilot allocation requires more complicated implementation than the 3rd order polynomial-based pilot allocation because the 5th order polynomial-based pilot allocation applies exhaustive search of two parameters by using two fractional unit resolutions.…”

“…The averaged MSEs in terms of a / when p = /16 and SNR = 20 dB in the cases of (a) = 2048 and (b) = 4096. The 푘 / 푘 results as shown in(13) with respect to the 16 smallest eigenvalues of (1/ p )D 퐻 p D p when = 2048, a = 1884, and p = 128.…”

Joint Sequence Design for Robust Channel Estimation and PAPR Reduction for MIMO-OFDM Systems

“…Combination of TR and clipping methods have also been proposed in [17]. Recently, a combined channel estimation and PAPR reduction technique was proposed by [18] in which phase information of the pilot, together with TR, were used to mitigate PAPR of the information-bearing signal for MIMO-OFDM system with null subcarriers. An overview of previous proposed PAPR reduction techniques are given in [19], [20].…”