DATA/DOCUMENT MANAGEMENT
STRENGTHENING THE SENSOR SIGNAL
Matthew Owen, Co-founder of internet of things (IoT) connectivity specialist M2M Intelligence, explains how to overcome variable signal quality in fixed BMS sensors.
Wireless is often the only viable option for connecting sensors, especially when retro-fitting building management systems (BMS) to large blocks or campus sites. Commonly this involves the use of low-power radio to connect sensors to a gateway with 3G or 4G GSM to send the data to the BMS.
Although providing greater installation flexibility, wireless connectivity can lack the reliability of cabled alternatives, and the seemingly inexplicable loss of signal from sensors can become a time consuming and cost-generating frustration for facilities managers.
“Commonly, proprietary radio
frequency (RF) protocols such as Zigbee or Z-wave are used for the short-range sensor-to-gateway connection”
Diagnosis can be tricky – connections can fail between the sensors and the gateway or from the gateway to the network. Commonly, proprietary radio frequency (RF) protocols such as Zigbee or Z-wave are used for the short- range sensor-to-gateway connection, which are subject to interference from sources as diverse as microwave ovens, production machinery and laboratory equipment.
Further disruption can be traced to the surrounding landscape: new buildings between sensor and gateway for example, and even the emergence of tree leaves in springtime can affect some frequencies.
Making the network more resilient can help mitigate the impact of these factors. Innovations such as the overlay meshing application Wirepas, that will sit on virtually any sensor regardless of RF protocol, can help enable your sensors to move data back to the gateway independently via indirect ‘hops’ to reroute the connection.
Alternative solutions include changing frequencies and even looking at direct connectivity via low-power wide-area network (LPWAN) rather than a gateway hub and spoke.
Further challenges arise when connecting the gateways back through the internet to the BMS, especially in retrofit scenarios or where third-party access is required. Building tenants often prohibit network access in line with cybersecurity policies, leaving the FM provider to find an alternative such as 3G or 4G mobile data.
Using a single-network SIM to connect gateways to BMS may superficially seem cost effective, but can lead
48 | TOMORROW’S FM
to problems needing expensive site visits. Commonly, engineers perform a site survey to identify the best mobile network to use, before installing the appropriate SIM. However, this only provides a snap-shot of signal strength on the day, and subsequent problems with GSM connectivity can often be traced to changes in network load causing a cell to contract, or environmental factors such as new buildings affecting signal propagation.
Roaming for long-term connectivity FMs can overcome this by using multi-network SIMs to allow devices to switch to the best network if the original connection is lost, however a further consideration is that IoT devices generally use GSM 2G voice carrier data to measure signal strength. This is not a reliable guide to 3G or 4G data availability though, because lower frequency 2G achieves wider coverage deeper building penetration than 3G or 4G data signals.
As a result, many operators offer ‘steered’ SIMs that will allow use of alternative networks, but maintain a preference for the operator network. This means they can get stuck on a home network with strong GSM 2G signal but with no 3G or 4G data.
Gateway design also plays a part in connection reliability. Device module firmware can be reconfigured to take advantage of non-steered, multi-network, SIMs by testing for the availability of 3G and 4G data availability to select the next best network.
Finally, while it’s easy to assume that mobile coverage is universal and that SIMs are a commodity to be bought on price, many FMs now prefer to use a premium non- steered multi-network solution to ensure they never need to call out an engineer simply to swap out a SIM card.
www.m2mintelligence.com
twitter.com/TomorrowsFM
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86
