Abstract
New use cases and applications in factory automation scenarios impose demanding requirements for traditional industrial communications. In particular, latency and reliability are considered as some of the most representative Key Performance Indicators (KPI) that limit the technological choices addressing wireless communications. Indeed, there is a considerable research effort ongoing in the area of wireless systems, not only from academia, but also from companies, towards novel solutions that fit Industry 4.0 KPIs. A major limitation for traditional wireless architectures is related to the harsh nature of the industrial propagation channel. Accordingly, this paper addresses these challenges by studying the reliability and latency performance of the joint use of different retransmission schemes in combination with Non-Orthogonal Multiple Access (NOMA) techniques. Two general retransmission schemes have been tested: time-based and spatial diversity-based retransmissions. An adaptive injection level NOMA solution has been combined with the retransmission schemes to improve the reliability of critical information. In all cases, a particular set of simulations has been carried out varying the main parameters, such as modulation, code rate and the injection level. Moreover, the impact of the number of transmitters in relation to the communication reliability has been analyzed. Results show that spatial diversity-based retransmissions overcome considerably the reliability obtained with time-domain retransmissions while maintaining assumable latency rates.
Highlights
Wireless communications are considered one of the most challenging and promising research areas of the so-called Industry 4.0 [1], [2]
In this work, a case of partial uncorrelation is assumed, where the instantaneous Signal-to-Noise Ratio (SNR) of each node has been modeled as a combination of two components: the mean SNR, which is a static value that depends on the reception characteristics, and the variable attenuation of the channel which varies with time: SNRi,k = θi + αi,j,k, (1)
EVALUATION The reliability results obtained with time-domain retransmissions are presented in Fig. 5, which is based on Packet Error Rate (PER) and Packet Loss Rate (PLR) measurements
Summary
Wireless communications are considered one of the most challenging and promising research areas of the so-called Industry 4.0 [1], [2]. A different strategy, based on improving the architecture of the access network is explored in [17], where several MAC level techniques in combination with the Wi-Fi PHY layer in challenging wireless channels are tested. In [19], the use of Non-Orthogonal Multiple Access (NOMA) in combination with the IEEE 802.11n standard to meet the strict industrial requirements is considered. These results show that NOMA has the potential for enabling highly robust communications for industrial environments. In this paper, we propose and evaluate the joint use of NOMA and different diversity schemes to enhance the latency and reliability in industrial wireless networks.
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