This paper studies the performance of a IoT-relaying node transmission with massive multiple-input multiple-output (MIMO) system network. The system is a simple schematic setup which includes one user, one IoT-relaying node and one base station (BS). The user and IoT-relaying node have a single antenna while the BS is equipped with a hundred and/or even a thousand of antennas array. The transmission protocol is performed based on a very simple amplify-and-forward (AF) relaying scheme. To decode the transmitted signal from the user, the BS applies maximum-ratio (MR) combining technique (the combined channel of the links from the user to BS and the IoT-relaying node to the BS) under assumption of perfect channel station (CSI). The exact closed-form of the throughput and the results for the signal-to-interference-plus-noise ratio (when the number of relay antennas goes to large) are analyzed.

The fifth generation (5G) cellular network has been commercialized recently to fulfill the new demands such as very high data exchange rate, extra low latency and high reliability. Many new technologies have been introduced and exploited since the early of the 2010s. Among these emerging technologies, full-duplex relaying cognitive radio networks, device-to-device communications and cell-free massive multiple-input and multiple-output have been considered as promising technologies/systems for 5G and beyond. This work provides a comprehensive study on the concepts, advantages and challenges of the above-mentioned technologies. In addition, we also introduce four new research directions which are challenges of 5G and beyond.