# Performance Comparisons of Broadband Power Line Communication Technologies
## 4 BER Comparisons and Discussion  
### Computer Simulation Blocks  
The communication reliability for the PLC physical layer is investigated in terms of BER. Figure 11 shows the computer simulation block diagram for BER measurement. Randomly generated bits are processed at the transmitter, and the output OFDM signal of the transmitter enters the PLC channel. The channel output corrupted by noise is input to the receiver. The receiver specifications for the three PLC technologies are not given in the standards. Thus, the algorithm used for each PLC receiver is designed to achieve the best performance possible. In this context, impulsive noise is not included since our purpose is to obtain the upper performance bound for each PLC. For background noise, colored noise is known to reflect the noise of the PLC environment better. However, AWGN is also considered useful when comparing the upper performance bound of the PLC technologies. Thus, for the noise, AWGN is used in the simulation. The performance comparisons are based on the upper limit of the performance that each PLC specification can achieve.  
The IoT PLC receiver in Figure 11 consists of several functional blocks. In this paper, it is assumed that symbol and carrier synchronization between the transmitter and the receiver is perfect. That is, there is no timing error and no carrier frequency error at the receiver. CP and CS are removed from the received signal, which is then converted to the frequency domain by FFT. There are pilot symbols or pilot carriers in the transmitted signal to help channel estimation. Algorithms to estimate the channel response from the pilot tones have been described, and each algorithm has pros and cons [34]. Since our goal is to evaluate the upper limit of the BER performance, we assume a perfect channel and signal-to-noise ratio (SNR) estimation. The channel response is used to equalize each distorted subcarrier signal by a frequency domain one-tap equalizer using the minimum mean square error (MMSE) algorithm.  
The equalized subcarrier signals are demodulated. The demodulator produces soft decision values since CTC decoding uses soft decision inputs. The demodulated in-phase or quadrature components are combined by the diversity demapper. The combined values are sent to the channel deinterleaver and subblock deinterleaver, which function as an inverse channel interleaver and subblock deinterleaver, respectively.  
For CTC decoding, several methods are described in the literature [35; 36; 37]. Maximum a posteriori (MAP) or log-MAP, which is the log-domain implementation of the MAP, is the optimal decoding algorithm. Log-MAP provides less computational burden than MAP, but the complexity is still high. The max-log-MAP algorithm with a correction term has viable complexity and provides equivalent performance to the log-MAP. Thus, the max-log-MAP with a correction term is used for CTC decoding  
Figure 11: Simulation block diagram for BER measurements.  
This algorithm is also used when the performance of HPGP is evaluated. Finally, the decoded bit stream is compared to the input bit stream and the BER is computed.