Abstract
In this paper, a joint non-orthogonal multiple access and time division multiple access (NOMA-TDMA) scheme is proposed in Industrial Internet of Things (IIoT), which allowed multiple sensors to transmit in the same time-frequency resource block using NOMA. The user scheduling, time slot allocation, and power control are jointly optimized in order to maximize the system -fair utility under transmit power constraint and minimum rate constraint. The optimization problem is nonconvex because of the fractional objective function and the nonconvex constraints. To deal with the original problem, we firstly convert the objective function in the optimization problem into a difference of two convex functions (D.C.) form, and then propose a NOMA-TDMA-DC algorithm to exploit the global optimum. Numerical results show that the NOMA-TDMA scheme significantly outperforms the traditional orthogonal multiple access scheme in terms of both spectral efficiency and user fairness.
Highlights
Industrial Internet of Things (IIoT) offers interconnection and interoperability to industrial systems through sensing nodes and actuators with ubiquitous communication and computation abilities [1], and has been applied in numerous areas such as industrial production, traffic monitoring, and so on [2,3,4]
The performance of the proposed non-orthogonal multiple access (NOMA)-time division multiple access (TDMA) scheme is evaluated through simulations, where we set the noise as an additive white Gaussian variable with zero mean and unit variance, and the transmit signal-to-noise-ratio (SNR) is equivalent to the transmit power
NOMA-TDMA scheme is significantly better than TDMA scheme, since NOMA allows two sensors transmitting at the same time-frequency resource block, which enhances the spectrum efficiency and improve the throughput of the system
Summary
Industrial Internet of Things (IIoT) offers interconnection and interoperability to industrial systems through sensing nodes and actuators with ubiquitous communication and computation abilities [1], and has been applied in numerous areas such as industrial production, traffic monitoring, and so on [2,3,4]. As a significant component of the future transformation of industrial systems, IIoT has attracted enormous attention from academics and industries. TDMA only supports access of a single node in each time slot, which cause low spectrum efficiency and high transmission delay, it cannot meet the requirement of the IIoT with massive nodes to access [6]. The non-orthogonal multiple access (NOMA) technique has attracted significant research interest for its potential to enhance spectrum efficiency and to support different QoS requirements by allowing multiple users to transmit in the same time-frequency resource block, which is different from conventional orthogonal multiple access (OMA) techniques (e.g., TDMA, frequency division multiple access (FDMA)) [7,8,9]. To avoid the inter-user interference in NOMA network, successive interference cancellation (SIC) technique is applied to decode the received
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