Yoshihiko Ogawa

System Performance of Clustered DFT-S-OFDM Considering Maximum Allowable Transmit Power

Support of non-contiguous frequency resource allocation (FRA) based on clustered discrete Fourier transform-spread orthogonal frequency division multiplexing (clustered DFT-S-OFDM) is considered a key element of LTE-Advanced uplink to enhance the spectrum efficiency via an enhanced frequency domain scheduling. However, reduction of out-of-band emissions due to multiple clusters is a critical issue for clustered DFT-S-OFDM in an actual system. This paper verifies the system performance gain of clustered DFT-S-OFDM using power control (PC) with maximum power reduction (MPR) for suppression of out-of-band emissions, under realistic assumptions, including channel quality measurement error and power setting error. Simulation results show that the clustered DFT-S-OFDM improves the average throughput over DFT-S-OFDM, even with PC with MPR, but suffers some degradation due to the large fixed MPR. By applying a novel PC with autonomously adjusted MPR that depends on the separation of the clusters, no degradation of the performance gain is observed while satisfying the spectrum emission requirements.

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 4dB with keeping the low Peak-to-Average power ratio (PAPR) property compared to the conventional scheme.