Abstract
Superposed multicarrier transmission scheme is known to improve frequency utilization efficiency where several wireless systems share spectrum. In superposed multicarrier transmission scheme froward error correction (FEC) coding is applied over subcarriers so that the effects of interference caused by superposition is mitigated by interleaving effects. When the interference power is large, the effects of FEC become smaller particularly owing to the mis-setting of initial log likelihood ratio (LLR). To solve this problem, FEC metric masking is proposed where initial LLRs for interfered subcarriers are replaced by neutral value in the receiver followed by decoding. Since the knowledge of interfered band had been considered as pre-known in early studies, we proposed interfered band detection technique based on packet error rate (PER) by using FEC metric masking. In this technique the subcarriers where FEC metric masking is applied are changed and PER is measured. Based on the masked subcarriers corresponding to the minimum PER, we can detect the interfered band. In this report we alter the estimation scheme of interfered band for the detection technique proposed. Altered estimation scheme is based on the gradients of PER instead of minimum PER. We evaluate the detection technique by computer simulation and show that it can detect the interfered band with higher probability when E_b/N_0 is low and superposed rate is high.
