Abstract
Due to the lack of spectrum resources, effective methods must be proposed to meet the needs of the Internet of Things (IoT) massive connectivity. In this paper, two effective techniques to improve spectral efficiency, namely, sparse code multiple access (SCMA) and wireless multicast, are used together for the IoT system to expand network capacity. Different from existing works, we introduce layered coding into the SCMA-based IoT system and consider two channel state information (CSI) feedback scenarios, which can make full use of the diversity gain of multiple receivers. The original multicast data are divided into one basic layer (BL) and several enhancement layers (ELs) by layered coding. IoT receivers with good channel gain can achieve better quality of service by receiving more data layers. In the transmission scheme with CSI, the physical resources allocated to the BL and ELs can be dynamically adjusted. In the transmission scheme without CSI, a fixed resource allocation scheme is performed because it is impossible to calculate the multicast rate of each codebook in real time. To further improve the system capacity, we have proposed resource allocation algorithms for these two schemes according to different requirements for computational complexity. The simulation results show that the proposed schemes can provide a higher system capacity than unicast SCMA and nonlayered multicast SCMA.
Highlights
A S 5G technology comes into service and continues to grow, smart cities have become a reality and are rapidly changing urban life [1]
We introduce layered multicast into the sparse code multiple access (SCMA)-based Internet of Things (IoT) system, and two transmission schemes are considered according to the availability of channel state information (CSI)
We focus on a SCMA-based IoT network, where the base station (BS) is at the center of the cell with a radius of R
Summary
A S 5G technology comes into service and continues to grow, smart cities have become a reality and are rapidly changing urban life [1]. A large number of connected devices have improved production efficiency and exacerbated the shortage of spectrum resources To meet these challenges, many new technologies, such as satellite communications, non-orthogonal multiple access (NOMA), wireless multicast and ultra-dense networks, continue to emerge. In literature [21], the authors proposed a new framework that includes joint control of the dynamic uplink resource dimensioning for SCMA-based 5G and IoT networks In these SCMA unicast strategies, while some receivers have a common interest (e.g., live sports streaming, streaming media, etc.), the same data must be sent separately, resulting in low spectral efficiency and low link utilization. The other is that the CSI is absent from the transmitter and called the transmission scheme without CSI (T-CSI-free), in which the transmitter allocates physical resources to the BL and ELs at a fixed ratio In these proposed schemes, the outage probability and capacity are used to evaluate the system performance.
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