Pilot signal generation scheme using frequency dependent cyclic shift sequence for inter-cell interference mitigation

Cyclic shifted Zadoff-Chu (CS-ZC) sequences are adopted as a uplink pilot signal in evolved universal terrestrial radio access (E-UTRA). In a single carrier frequency division multiplexing access (SC-FDMA) based cellular system, the resource blocks (RBs) are normally assigned independently among the cells. So, the assigned RBs to user equipment (UE) in different cells may partially overlap. These causes deteriorate the orthogonality between CS-ZC sequences. The deterioration of the orthogonality results in significant loss of channel estimation accuracy. The reason of the deterioration is that the different spectrum element of CS-ZC sequence is assigned at overlapped sub-carriers between cells. Therefore, we propose a frequency dependent cyclic shift sequence, which assigns the same spectrum element of CS-ZC sequence at overlapped sub-carriers between cells. Simulation results show that the proposed scheme can improve the BLER performance by 4 dB with keeping the low peak-to-average power ratio (PAPR) property compared to the conventional scheme.