We propose applying pulse amplitude modulated code shift keying (CSK/PAM) to indoor power line communication (PLC) for the high-speed data transmission at the low electromagnetic wave leakage. However, CSK/PAM system using conventional binary sequence, for example Gold sequence and M sequence, has error floor for real power line channels even with rake receiver because of the poor properties of odd auto and cross-correlation. Therefore, we propose extending binary sequence to real-valued sequence and we optimize performance in real-valued sequence by minimizing the even and odd, autoand cross-correlation values. We show that the CSK/PAM system using the optimized real-valued sequence can achieve better BER (Bit Error Rate) performance as compared with that using Gold sequence by computer simulation.