Abstract
In this paper, we experimentally evaluate and compare the robustness against interference of the OQPSK-DSSS (Offset Quadrature Phase Shift Keying-Direct Sequence Spread Spectrum) and the SUN-OFDM (Smart Utility Network-Orthogonal Frequency Division Multiplexing) physical layers, as defined in the IEEE 802.15.4-2015 standard. The objective of this study is to provide a comprehensive analysis of the impact that different levels of interference produce on these modulations, in terms of the resulting PDR (Packet Delivery Ratio) and depending on the length of the packet being transmitted. The results show that the SUN-OFDM physical layer provides significant benefits compared to the ubiquitous OQPSK-DSSS in terms of interference robustness, regardless of the interference type and the packet length. Overall, this demonstrates the suitability of choosing the SUN-OFDM physical layer when deploying low-power wireless networks in industrial scenarios, especially taking into consideration the possibility of trading-off robustness and spectrum efficiency depending on the application requirements.
Highlights
The IEEE 802.15.4 standard [1] was first released in May 2003 and defined a physical layer (PHY)and a MAC (Medium Access Control) layer for WPAN (Wireless Personal Area Networks) operating in the sub-GHz (868 MHz in Europe, 915 MHz in America) and the 2.4 GHz worldwide ISM (Industrial, Scientific and Medical) frequency bands [2]
Results obtained using the research methodology and the experiment setup described in the previous section are presented for each interferer modulation (OFDM1-MCS1, OFDM2-MCS2, OFDM3-MCS3, OFDM4-MCS5 and OQPSK-DSSS) and packet length (20 bytes and 120 bytes) in Figures 5–9, respectively
This section discusses the results outlined in the previous section and presents recommendations to researchers and practitioners, serving as a tool to understand the behavior of each particular modulation under interference conditions, and motivating the use of the Smart Utility Networks (SUN)-OFDM for deploying low-power wireless systems in industrial scenarios
Summary
A MAC (Medium Access Control) layer for WPAN (Wireless Personal Area Networks) operating in the sub-GHz (868 MHz in Europe, 915 MHz in America) and the 2.4 GHz worldwide ISM (Industrial, Scientific and Medical) frequency bands [2]. The 2015 standard revision adopted the MAC layer protocols defined in the IEEE 802.15.4e-2012 [7] amendment. Among others, this amendment defined the TSCH (Time Slotted Channel Hopping), a channel access mechanism that combines TDMA (Time Division Multiple Access) and FDMA (Frequency Division Multiple Access) to support industrial requirements, including reliable packet delivery (i.e., 99.999%) in adverse conditions such as multi-path propagation and external interference
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