Millimeter-Wave NOMA Transmission in Cellular M2M Communications for Internet of Things

Massive connectivity and low latency are two important challenges for the Internet of Things (IoT) to achieve the quality of service provisions required by the numerous devices it is designed to service. Motivated by these challenges, in this paper we introduce a new millimeter-wave nonorthogonal multiple access (mmWave-NOMA) transmission scheme designed for cellular machine-to-machine (M2M) communication systems for IoT applications. It consists of one base station (BS) and numerous multiple machine type communication (MTC) devices operating in a cellular communication environment. We consider its down-link performance and assume that multiple MTC devices share the same communication resources offered by the proposed mmWave-NOMA transmission scheme, which can support massive connectivity. For this system, a novel MTC pairing scheme is introduced the design of which is based upon the distance between the BS and the MTC devices aiming at reducing the system overall overhead for massive connectivity and latency. In particular, we consider three different MTC device pairing schemes, namely: 1) random near and the random far MTC devices; 2) nearest near and the nearest far MTC devices (NNNF); and 3) nearest near and the farthest far MTC device. For all three pairing schemes, their performance is analyzed by deriving closed-form expressions of the outage probability and the sum rate. Furthermore, performance comparison studies of the three MTC device pairing schemes have been carried out. The validity of the analytical approach has been verified by means of extensive computer simulations. The obtained performance evaluation results have demonstrated that the proposed cellular M2M communication system employing the mmWave-NOMA transmission scheme improves outage probability as compared to equivalent systems using mmWave with orthogonal multiple access schemes.

I. Introduction

Through the development of numerous applications, the Internet of Things (IoT) [1], [2] aims at providing a host of new services to citizens, private and public companies as well as to governmental administrations [3]–[5]. In general, it is envisioned that the IoT will provide a platform which will connect a huge number of devices in order to gather, share, and forward information between devices as well as their users [6]–[8]. It is estimated that by the year 2020 almost 50 billion of devices will connected to this platform [9]. To accommodate the drastically increasing number of these devices, the resulting huge increase in data traffic will have a great impact on the design and implementation of fifth generation (5G) wireless communication systems. In particular, there will be challenging requirements for their efficient operation, including massive connectivity and low latency [10], [11]. On the one hand, machine-to-machine (M2M) communications have been regarded as one of the promising new technologies to realize IoT employing the 5G network [12]. M2M communication systems realize automated data communications among machine type communication (MTC) devices thus constituting the basic communication infrastructure for the emerging IoT [13], [14]. In addition, long term evolution (LTE) for MTC and narrow band IoT have been proposed on top of existing cellular standards, which can provide reliable solutions for M2M communications [15]. On the other hand, nonorthogonal multiple access (NOMA), which has been proposed as a multiple access scheme to be employed with 5G wireless communication systems, has the ability to support massive connectivity by means of nonorthogonal resource allocation while simultaneously reducing latencies by its grant-free scheduling. For example, in [16], an interesting power-domain user multiplexing scheme for future radio access has been proposed. Note that, in conjunction with NOMA transmission, the joint use of superposition code at the transmitter and successive interference cancellation (SIC) at the receiver has been also studied [16]–[20].