Performance Analysis of Block/Zero-Comb Pilot and Nonzero-Comb Pilot Over MIMO-PLC Systems

In this paper, we consider Power Line Communications (PLC) for Smart Grid (SG) using Multiple-Input Multiple-Output and Orthogonal Frequency Division Multiplexing (MIMO-OFDM). We investigate a 2 x 2 MIMO-OFDM system and propose a novel nonzero comb pilot (NZCP) design for channel estimation that can cope with pilot contamination without the need for zero-pilot insertion in adjacent channels. The Bit Error Rate (BER) performance vs. E-b/N-0 is demonstrated using numerical simulations for uncoded and coded systems using Low Parity Density Check (LDPC) error correcting codes. The performance is compared with conventional Zero-comb pilot (ZCP) and the block pilot methods through frequency-selective multipath PLC channels and in the presence of Additive White Gaussian Noise (AWGN) and symmetric alpha-stable (S alpha S) type of impulsive noise. Additionally, a novel averaging method is introduced to reduce the effects of AWGN, S alpha S and Mean Square Error (MSE) metric is used to assess the quality of the channel estimation. The numerical results presented demonstrate that the NZCP approach using averaging outperforms all the methods considered, e.g. for the uncoded system at a BER of 10(-5) an improvement in E-b/N-0 of 3.6 and 4 dB against ZCP and block approaches, respectively. In contrast, in the coded system, the coding gain is of the order of 20 dB compared to the uncoded cases with the NZCP proposed method outperforming all the other considered approaches by at least 0.5 dB. Furthermore, the presented BER results demonstrate that the S alpha S impulsive noise has a greater impact on the performance of the MIMO-PLC system. It is shown that when utilizing a hardlimiter to limit the effects of SaS, the BER can reach 8 x 10(-5 )at an E-b/N-0 of 45 dB when alpha = 1.5. In contrast, when alpha = 1, which represents a more severe case of S alpha S, a BER level of 3.5 x 10(-4) is attained at an E-b/N-0 of 90 dB. However, the proposed averaging-NZCP system can robustly estimate the channel frequency responses (CFR) of the MIMO-PLC channel over S alpha S noise outperforming other commonly used pilot approaches.