Rate Splitting Multiple Access Assisted Cell-Free Massive MIMO for URLLC Services in 5G and Beyond Networks

With the advent of the fifth-generation (5G) and beyond mobile communications, a plethora of Internet-of-Things (IoTs) applications, such as intelligent factories, smart transportation, and others are rapidly evolving. 5G and beyond networks support three typical application scenarios, i.e., ultra-reliable and low-latency communications (URLLC), enhanced mobile broadband (eMBB) and massive machine type communication (mMTC), each of which renders a distinct set of quality of service in terms of reliability, latency, transmission rate and connectivity. URLLC is seen as a crucial technology for supporting critical applications because of its emphasis on rare and extreme events, as well as its strict demands for low latency and high reliability [1]. For example, in order to effectively support applications like robot control, autonomous vehicles, and virtual reality, it is necessary to have an end-to-end delay threshold of 1 to 10 milliseconds and a block error rate (BLER) between 10−5 and 10−7 [2]. Due to the unique limitations of increased reliability and reduced latency, URLLC traffic often involves very brief transmission blocklengths, making Shannon’s capacity theorem irrelevant [3], [4]. On the other hand, existing cellular systems face difficulties in meeting the stringent quality of service (QoS) criteria needed for URLLC due to structural constraints. Therefore, it is essential to have advanced network architectures and various access technologies in order to achieve URLLC.