An Efficient Wireless Fronthaul (EWF) Method for LTE Signal Transmission

Abstract

This paper proposes a novel EWF method for LTE signal transmission. Unlike the classical common public radio interface (CPRI) where the in-phase and quadrature (I/Q) waveforms and the control words (CWs) are transmitted as a binary sequence in the time domain, the proposed scheme transmits the analog I/Q waveforms and quadrature amplitude modulation (QAM) signals that contain CWs via frequency domain multiplexing (FDM) synchronously. The bandwidth of the proposed method is reduced by 45% compared with the digital CPRI compression method in the literature. Furthermore, we propose a novel asymmetric single tone pilot based joint I/Q imbalance, frequency offset and phase noise suppression method for the proposed system. We experimentally demonstrate the EWF transmission of one 20 MHz LTE signals with a CPRI equivalent data rate of 1.228 Gbps as a proof of the concept. The test error vector magnitude (EVM) of the OFDM-64QAM LTE signals is below 2% from -52dBm to -38dBm received power and the CWs are recovered without error. This EWF demo can be extended to support CPRI equivalent data rates of n× 1.228Gbps by aggregating more I/Q waveforms and QAM signals in the frequency domain.