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Part II: “Birdhouse in Your Soul”

December 13, 2017 - Wirepas

Our next stop on the musical tour of smart lighting is courtesy of They Might be Giants. There’s an obvious link to lighting, but more interesting is to consider the relevance of the eponymous Blue Canary of the song. Bear with me…

To realise the true potential of smart connected lighting, that is not limited to new build installations, it’s intuitively obvious that wireless connectivity is required. The cost and effort to retrofit existing buildings and outdoor spaces with new cabling would be prohibitive. In some places control cables are possible to install, but why bother when with the right wireless technology, one can have reliable, future-proof connectivity without the hassle of data cabling?

Now that we understand the need to embrace wireless connectivity for lighting control, the first thing to consider is the right network topology for the job. Here we have two main options: star or mesh. In both cases, a gateway is required to connect the network to the outside world, such as BEMS or the cloud. However, in a star network, a central gateway exists to which all devices directly connect. To pass a message between two devices in a star network, for ex. a sensor and a light point, that message must go via the gateway. Compare this to a mesh network, where all devices can send messages directly to their peers in the network without going via a central gateway.

The mesh approach is a much better fit to the needs of lighting control platforms, due to low latency, autonomous operation and de-centralised decision making. It naturally minimizes the amount of data that needs to be sent in the uplink direction to the network gateway. The alternative is that the topology forces “hub and spoke” thinking, where there is centralised decision making regarding the behaviour of each individual light point. There’s different strategies to employ a mesh network, let’s look in to a few.

There are a lot of choices for wireless connectivity indoors and outdoors. Over the years many attempts at providing connectivity have resulted in standards such as ZigBee Light control and the Bluetooth Mesh profile. Is the latter the Blue Canary that They Might be Giants referred to? It certainly is the great white hope of the industry to provide “interoperability” between vendor equipment. Before we go there, let’s consider the network requirements.

The challenge with smart lighting is that the technical requirements placed on the connectivity include low latency node to node communication (think about it – when you actuate a light switch you expect the lighting group to activate immediately. In this context immediately is typically less than 200ms to cheat the human brain). On the other hand, in truly distributed networks with sensor fusion, uplink and downlink bandwidth requirements reach into the 100’s of kbit/s. Not to mention that these control systems must work in a typical office environment, with already deployed wireless networks such as Wi-Fi or Bluetooth. These are hard trade-offs to balance!

Up until now, these standards have relied on the vertical integration of the networking stack, from the physical layer up to application layer. However, has this genuinely resulted in interoperability between systems? I would argue not. Therefore, why are we sacrificing link layer performance by not taking advantage of advances in the physical and layer 2? It doesn’t buy us anything in terms of interoperability. The Blue Canary is compromised by not providing state of the art throughput on the one hand and limited vendor interoperability on the other.

Wirepas believes that this is the way the open systems will ultimately evolve by unleashing de-coupled innovation at all layers of the network stack. So, there might be a Blue Canary in your light switch but will it answer the throughput, latency and interoperability requirements of the lighting backbone mesh – probably not.

Richard Kinder, VP, Head of Product Marketing