An improved multicarrier differential CDMA system with synchronization errors in HF channels

Under the time variant and fading HF channel, an improved Multicarrier CDMA System using Frequent Domain Differential Detection (MC-FDDD-CDMA) for low SNR links is proposed. With synchronization errors, including frequent offset and timing offset, we analyze the system BER performance under the fast fading HF channel, where the adjacent subcarriers have different channel responses. The results show that the synchronization errors reduce the desired signal amplitude, and introduce ICI. In addition, a Common Phase Error is generated by differential detection, which causes the rotation of signal constellation and limits the system BER performance. Therefore, we exploit a novel phase estimation method applicable to the MC-FDDD-CDMA system. Finally, computer simulations prove that the improved system can effectively reduce the CPE and considerably promote the BER performance under the low SNR HF channels.