Hybrid AF/DF Cooperative Relaying Technique with Phase Steering for Industrial IoT Networks

Sangku Lee,Bang Chul Jung,Janghyuk Youn

doi:10.3390/en14040937

Abstract

For the next generation of manufacturing, the industrial internet of things (IoT) has been considered as a key technology that enables smart factories, in which sensors transfer measured data, actuators are controlled, and systems are connected wirelessly. In particular, the wireless sensor network (WSN) needs to operate with low cost, low power (energy), and narrow spectrum, which are the most technical challenges for industrial IoT networks. In general, a relay-assisted communication network has been known to overcome scarce energy problems, and a spectrum-sharing technique has been considered as a promising technique for the radio spectrum shortage problem. In this paper, we propose a phase steering based hybrid cooperative relaying (PSHCR) technique for the generic relay-assisted spectrum-shared WSN, which consists of a secondary transmitter, multiple secondary relays (SRs), a secondary access point, and multiple primary access points. Basically, SRs in the proposed PSHCR technique operate with decode-and-forward (DF) relaying protocol, but it does not abandon the SRs that failed in decoding at the first hop. Instead, the SRs operate with amplify-and-forward (AF) protocol when they failed in decoding at the first hop. Furthermore, the SRs (regardless of operating with AF or DF protocol) that satisfy interference constraints to the primary network are allowed to transmit a signal to the secondary access point at the second hop. Note that phase distortion is compensated through phase steering operation at each relay node before second-hop transmission, and thus all relay nodes can operate in a fully distributed manner. Finally, we validate that the proposed PSHCR technique significantly outperforms the existing best single relay selection (BSR) technique and cooperative phase steering (CPS) technique in terms of outage performance via extensive computer simulations.

Highlights

The fourth industrial revolution (Industry 4.0) is a new generation of technology that allows collecting and processing data across machines, enabling monitoring, decision-making and automation to improve productivity, product quality, and services at low costs
The result that phase steering based hybrid cooperative relaying (PSHCR) is better than original cooperative phase steering (CPS) is because additional channel gain from secondary relays (SRs) that operates with AF relaying protocol is much larger than the effect of amplified noise of AF relaying protocol
It is observed that the proposed PSHCR technique achieves the same performance as the original CPS technique with high transmit signal-to-noise ratio (SNR) because all available SRs succeeded in decoding and operating with DF protocol, which is the same operation as the original CPS technique

Summary

Introduction

The fourth industrial revolution (Industry 4.0) is a new generation of technology that allows collecting and processing data across machines, enabling monitoring, decision-making and automation to improve productivity, product quality, and services at low costs. For the massive connectivity in the future wireless communication networks in the industry, the Internet of Things (IoT) has been considered as a key technology to provide wireless control of the systems in Industry 4.0 [1]. In the industrial field, industrial IoT is considered that connects manufacturing robots, sensors, and control systems with the internet, such as smart factory. All sensors and actuators are wirelessly connected with the internet and their data are usually critical for operating factory so that highly reliable wireless communication is needed for wireless sensor networks (WSNs) in industrial IoT [2]. Sensors usually are powered by internal batteries, they cannot utilize high power for reliable data transmission To solve this problem, the relaying technique can be a reasonable solution to help communication between power limited nodes and access points (AP). Because of the coexistence of networks using the same spectrum bands, there is interference among the different networks, which might cause performance degradation

Methods

Results

Conclusion