Opportunistic Transmission Empowered Rate-Splitting Multiple Access for Military Communications: Approaches and Challenges

Rate splitting multiple access (RSMA) is a promising multiple access (MA) technology that can be used to enhance the performance of military multiple-input multiple-output (MIMO) systems. By virtue of its rate-splitting method, this technology can flexibly regulate the interference management strategy, achieving superior spectrum efficiency (SE) compared to traditional MA schemes. It is well-suited to meet the requirements of the modern battlefield, such as secure tactical data transmission, enhanced energy efficiency (EE)-enabled edge computing offloading, and satellite-terrestrial tactical communication. However, due to the complexity of the actual combat electromagnetic environment, it is extremely difficult to obtain perfect channel state information (CSI), which results in performance limitations. The opportunistic beamforming (OBF) technique can only feed back signal-to-noise ratio (SNR) values and utilize a multi-tactical-node selection mechanism to free the system from the constraints of perfect CSI, thereby improving the robustness of the military networks. This article analyzes the advantages brought by the combination of RSMA and OBF technologies, and proposes an OBF-aided RSMA (ORSMA) scheme. The article describes three types of performance improvements that ORSMA can achieve and analyzes current applicable tactical scenarios. Subsequently, we analyze the challenges faced by ORSMA in future combat scenarios.