Software Defined Radio Implementation of a Non-Orthogonal Multiple Access System Towards 5G

Non-orthogonal multiple access (NOMA) is envisioned to be one of the essential technologies for the fifth generation mobile network. In this paper, we implement a practical downlink NOMA system based on an open-source software defined radio (SDR) platform named as OpenAirInterface (OAI). For comparison purpose, our SDR-based NOMA system follows the basic specifications of long term evolution (LTE). In this system, a codeword-level successive interference cancellation (SIC) receiver is implemented. To improve the efficiency of the baseband signal processing in an SIC receiver, a multi-thread processing method is also introduced. Due to the limitation of original downlink control information (DCI) formats in current LTE systems, a new DCI format is dedicatedly designed for signal reconstitution in our developed NOMA system. Furthermore, some parts of upper layer protocols in LTE systems are modified to support the application services over the developed NOMA system. Based on our NOMA system, a series of over-the-air experiments are carried out, and the experiment results demonstrate that the NOMA scheme has a significant throughput gain compared with an orthogonal multiple access (OMA) scheme.