3GPP ACLR measurements for millimeter-wave wireless backhaul link with self-heterodyning mixing

This paper analyzes the signal quality achievable with a novel system architecture for low-power small cell remote units with integrated millimeter-wave wireless backhaul. The data signal on the backhaul link uses the same 3GPP compliant signal as with the access link serving the users. In contrast to existing systems, the small cell remote unit (RU) only consists of a simple frequency conversion from backhaul to access frequencies based on the self-heterodyning mixing concept with suppressed local oscillator (LO) signal. Therefore, it omits the LO source and greatly reduces power consumption and hardware complexity. Its sufficient linearity and phase noise performance at 60GHz was proven with measurements of an LTE signal easily meeting the 3GPP ACLR and EVM requirements, even with varying LO suppression levels on the backhaul link. Moreover, the required frequency stability of the access signal is demonstrated even when using a very unstable LO source.