PAPR reduction for carrier aggregated uplink in LTE-A system

The adoption of Carrier Aggregation (CA) technology enables the LTE-Advanced (LTE-A) system to support very-high-data-rate transmission over wide frequency bandwidths and to keep the backward compatibility of LTE system. Nevertheless, the authors have to deal with the significant increase of peak-to-average power ratio (PAPR) associated with the carrier aggregation, which determines the efficiency of Power Amplifier (PA) and the coverage of the terminal. This paper proposes an improved Selected Mapping (SLM) scheme to reduce PAPR of the LTE-A uplink data and demodulation reference signal (DMRS) symbols by 2 to 3 dB for different component carrier (CC) numbers and modulation modes, in which the signaling overhead of conventional SLM is eliminated by exploiting the features of DMRS. The linear property of Inverse Fast Fourier Transformation (IFFT) is used to reduce the computational complexity of SLM. The proposed scheme with 4 initial phase sequences reduces the complex multiplications by 63.5% and the complex additions by 68.2% compared with the conventional SLM scheme with 16 phase sequences while keeping the similar PAPR reduction performance.

1. Introduction

In order to reach peak transmission rate of 1Gbps in downlink and 500Mbps in uplink in IMT-Advanced system, the LTE-advanced system needs to support a maximum bandwidth of 100MHz. Using current spectrum allocation schemes, it is hard to find a complete frequency band capable of carrying the LTE-Advanced system. Thus, 3GPP proposed the solution of multi-carrier aggregation technology to meet the spectrum resource demand. Besides, using this method to realize the large bandwidth is beneficial to the backward compatibility of the LTE-A with the existing LTE system [1].