Abstract
Increasing the data rate of communication systems together with the performance are main goals of the communication networks in the future. Multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) relay networks as a key technology is one the main techniques to maintain the performance and data rate. Being influenced by fading channels, the MIMO-OFDM relay networks need some reliable approaches to estimate the channel response. Compressed sensing (CS) is one of the critical approaches to maintain the accuracy together with the spectral efficiency. In this paper, we have utilized CS-based approaches to estimate the MIMO-OFDM relay channel. Specifically, forward backward prediction (FBP) is used to estimate the fading channels. This approach benefits from backward correction which distinguishes it from other iterative approaches and helps interestingly in channel estimation accuracy. Moreover, in order to improve the channel estimation, pilot allocation approaches are proposed based on the system model and probability function. Furthermore, a cross entropy-based approach is utilized to propose two different approaches called sequential cross entropy self-coherence (SCE-SC) and parallel cross entropy self-coherence. Actually, mutual coherence is divided into two parts namely cross coherence and self coherence. It is demonstrated that in FBP-based approach self-coherence is important in mutual coherence. Consequently, the computations are interestingly decreased. The superiority of the method is represented using comparing simulations with other well-known approaches.
Highlights
By increasing demand of data rate and coverage area in modern communication systems, utilizing of relay communication networks is necessitated
7 Numerical results Here, we demonstrate the performance of the proposed algorithms in channel estimation and pilot allocations called forward backward prediction (FBP), Sequential cross entropy self-coherence (SCE-SC), and parallel cross entropy selfcoherence (PCE-SC) by simulation results
7.2 Comparison of the number of pilots In order to compare the effect of the number of pilots, we have considered the proposed method and B-vCoSaMP
Summary
By increasing demand of data rate and coverage area in modern communication systems, utilizing of relay communication networks is necessitated. Qi et al in [19] utilize the estimation of distribution algorithm (EDA) to define optimized pilot positions in SISO-OFDM systems He et al [18] and Akbarpour-Kasgari and Ardebilipour [13] generate optimized pilot sequences for MIMOOFDM compressed channel estimation using a GA and cross entropy (CE)-based approach. In order to exploit the FBP-based channel estimation and ζ -norm, we have designed appropriate measurement matrix using pilot symbols. It is represented in [13] that mutual coherence is related to the self-coherence of the sub-matrices and cross coherence of the sub-matrices related to each of the transmitter antenna, simultaneously. A novel approach called SCE-SC is designed using a cross entropy-based method to optimize the self-coherence of the developed measurement matrix. Cm×n stands for the set of all complex-valued m × n matrices, and ∅ denotes the null set
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