Radio Channel Quality in Industrial Wireless Sensor Networks

Abstract

-Wireless Mesh Sensor Networks are being deployed today in various monitoring and control applications. Some radio network designs, such as ZigBee, presume that radio connectivity is reasonably consistent over time. Others take the opposite approach of presuming that links are entirely unreliable, and build large degrees of physical redundancy into the network in the hope that a collection of redundant but unreliable individual links will result in a reliable overall system. Surprisingly little work has been done in the middle ground, endeavoring to understand the root cause of link failure in real-world factory environments and applying this knowledge in the design of protocols that adaptively detect and use workable radio channels.In collaboration under a Department of Energy grant for the Industries of the Future, General Electric and Sensicast Systems have studied theoretical and actual performance of 2.4 GHz IEEE 802.15.4 radio transceivers on the lab bench and on the factory floor, with particular attention to jamming from 802.11 and multipath fading. Temporal and frequency variations in link quality are explored. The implications for network reliability and protocol design are discussed.

NIST channel sounder overview and channel measurements in manufacturing facilities

“…Comment 1: The slopes from the linear regression fits for large-range values agreed with previous studies and research for industrial facilities environments [13,14,15,16,17].…”

“…Using a two-slope polynomial fit, we performed a linear regression on the path gain results with a break point at 11 or 13 m for all measurement runs. This break point is kept the same for all of the similar dimensional campaign routes in this document [13]. This allows for ease of comparison over all of the measurement campaigns.…”

Reliability Analysis of Wireless Real-Time Control Networks

“…In particular, we investigate the success probability for multihop mesh networks considering different path loss exponents and links impaired with different multipath fading processes. Measurements also confirm channel fading being the most significant cause of packet losses in industrial networks [4]. We show that the link outage-based approach accurately predicts the end-to-end reliability, and consideration of realistic transmission models leads to better insight into cross-layer interactions between physical layer parameters, link scheduling, and multipath routing in WirelessHART.…”

“…The per-link outage combined with the link schedule provides us with the end-toend reliability for a certain flow within the network. Channel models applicable to indoor industrial scenarios in the literature generally assume Rician or Nakagami-m fading [4], [10]. We primarily focus on Nakagami-m fading with fading parameter m as it lends itself for analytic treatment for random networks, providing more insight.…”

Reliable RSS-based routing protocol for Industrial Wireless Sensor Networks

“…In another scenario of their measurement, when two nodes were apart from 30 meters away NLOS, the RSSI values drop to -71± 3.2 dBm. Another measurement from an industrial factory [15] also shows that the fluctuations of RSS are about 25 dBm. It is notable that, in industrial environments, although the RSSI varies from different packets, most of the values are scattered in a limited range and objectively indicates the link quality between two nodes.…”