Zero-Forcing-Based Downlink Virtual MIMO–NOMA Communications in IoT Networks

Abstract

To support massive connectivity and boost spectral efficiency for internet of things (IoT), a downlink scheme combining virtual multiple-input multiple-output (MIMO) and nonorthogonal multiple access (NOMA) is proposed. All the singleantenna IoT devices in each cluster cooperate with each other to establish a virtual MIMO entity, and multiple independent data streams are requested by each cluster. NOMA is employed to superimpose all the requested data streams, and each cluster leverages zero-forcing detection to de-multiplex the input data streams. Only statistical channel state information (CSI) is available at base station to avoid the waste of the energy and bandwidth on frequent CSI estimations. The outage probability and goodput of the virtual MIMO-NOMA system are thoroughly investigated by considering Kronecker model, which embraces both the transmit and receive correlations. Furthermore, the asymptotic results facilitate not only the exploration of physical insights but also the goodput maximization. In particular, the asymptotic outage expressions provide quantitative impacts of various system parameters and enable the investigation of diversity-multiplexing tradeoff (DMT). Moreover, power allocation coefficients and/or transmission rates can be properly chosen to achieve the maximal goodput. By favor of Karush-Kuhn-Tucker conditions, the goodput maximization problems can be solved in closed-form, with which the joint power and rate selection is realized by using alternately iterating optimization.

Beamforming Optimization and Power Allocation for User-Centric MIMO-NOMA IoT Networks

“…In order to make full user of the advantages of NOMA and MIMO, the integration of NOMA with MIMO has been drawn a lot of attentions. [15] proposes a downlink scheme combining virtual MIMO and NOMA to support massive connectivity and boost spectral efficiency for IoT networks. In [15], the outage probability and goodput of the virtual MIMO-NOMA system are thoroughly investigated by considering the Kronecker model, which embraces both the transmit and receive correlations.…”

“…[15] proposes a downlink scheme combining virtual MIMO and NOMA to support massive connectivity and boost spectral efficiency for IoT networks. In [15], the outage probability and goodput of the virtual MIMO-NOMA system are thoroughly investigated by considering the Kronecker model, which embraces both the transmit and receive correlations. Then, the goodput maximization problems is solved in closed form by the Karush-Kuhn-Tucker conditions, with which the joint power and rate selection is realized by using alternately iterating optimization.…”

“…where (15) and (16) represent the maximum power constraint of the MBS and APs, respectively; (17) means that the achievable rate of each device should be less than the available data rate of backhaul links due to the limited backhual capacity. It is obvious that the joint resource allocation problem P1 is a nonconvex optimization problem with high computational complexity which is extremely difficult to solve.…”

Enhancing physical layer security via a UAV friendly jammer for NOMA‐based IoT systems with imperfect CSI

“…1 Differing from traditional orthogonal multiple access (OMA) techniques, nonorthogonal multiple access (NOMA) exploits power domain to allow multiple users to share the same frequency band, time slot and space resources, 2 and has been recognized as a promising technique for realizing ubiquitous connectivity in the IoT systems. [3][4][5][6] Specifically, in NOMA systems, different transmit power is allocated to users according to their channel strength, and successive interference cancellation (SIC) is applied to cancel the multiuser interference. 7 As compared with OMA systems, generally, NOMA systems can perform much better in realizing a better trade-off between system throughput and fairness among users.…”

UAV Relaying Enabled NOMA Network With Hybrid Duplexing and Multiple Antennas

“…Removing orthogonal characterization from the traditional OMA, the same time and frequency resources are shared among multiple NOMA users. With advantages of NOMA, it is relevant approach to provide advantages (massive connectivity and boost spectral efficiency) for Internet of Things (IoT) [6], [7]. According to the channel conditions, NOMA users are classified into two categories namely the far and the near users.…”