Networking Landscape for IoT LED Lighting

LED lighting projects for IoT need a wired or wireless networking component. NXP’s Roman Budek illuminates the way for designers.
By Joe Desposito, Senior Editor
IoT: LED lighting designs for the Internet of Things need to incorporate a networking component, and there are a variety of choices available. What do you recommend to designers?

Budek: There are certainly a lot of choices for IoT lighting controls. The first choice is in the hardware platform that will be used. Will the system be wired controls, which is still popular for industrial/ commercial lighting systems? Or will the customer want a wireless standard?
Industrial/commercial lighting systems, in some cases, already have a control wire along with the mains power. This control wire might be 0-10V, but it is a piece of wire that can be converted to say DALI, KNX, or DMX. If a control wire is not present, then the designer might select a wireless standard.
There are many choices for wired controls, and some of the designs are being refreshed to take advantage of newer and cheaper processes. NXP has updated their product portfolio to include DALI, DMX, and KNX running on the latest processors. The Intellectual Property was developed by NXP and provided to the customer. That is a big factor in the selection process—will the semiconductor manufacturer provide the IP, or will there be a license fee?
For the consumer retrofit market, wireless is the clear choice since control wires are probably not present in the home at each socket. For safety reasons, low voltage control wires cannot be run in the same raceway (conduit) as the mains power. Therefore, adding wired controls in a residential home becomes cost prohibitive
IoT: More specifically, what do you think of the various wireless technologies with regards to LED Lighting?
Budek: For wireless, the first selection criteria is to decide which hardware radio to use. Wi-Fi sounds like a great hardware device to use, but it has many drawbacks for lighting applications. It does not readily support a network stack, so Wi-Fi is restricted to star configurations, which are not suitable for most building layouts. With a large room or building, a node can easily be out-of-range from the router with a star configuration.
In addition, the standby power consumption of Wi-Fi means the installation might cost more per node than any realized energy savings from converting to intelligent lighting. For a wireless lamp or node, the radio is always on, listening for control commands. In one case, a 7W Wi-Fi LED lamp could have a standby power of 1W continuous power consumption, which makes it a difficult sell for conserving energy.
IEEE 802.15.4 based systems have the advantage of being able to support a network stack, low cost, and low standby power. 802.15.4 is the hardware platform that supports ZigBee which is a mesh networking stack providing near unlimited range and self-repair of lost connections. There are also plenty of other software stacks that can run on an 802.15.4 device.
Several software stacks are competing for lighting, but for the consumer retail lamps, it is clear that the 802.15.4 hardware radio is the clear winner. The design engineer should be looking for a vendor that can supply multiple stacks, not just a single one. NXP offers ZigBee HA, ZigBee LL, ZigBee SE, 6LoWPAN, RF4CE/ZRC, and several others.
For lighting, ZigBee LL ( LightLink) and ZigBee HA (Home Automation) are the current network stack favorites. These stacks are very similar and a Zigbee LL-bulb can also join a ZigBee HA network, thus providing full interoperability.
ZigBee LL has been adopted by The Connected Lighting Alliance (TCLA), which is a wireless standard for residential connected lighting. TCLA is an industry consortium that includes the top four lighting providers (Philips, OSRAM, GE, and Panasonic), other device manufacturers, as well as semiconductor companies like NXP.
ZigBee HA is popular in the USA at major retailers and cable companies because it is interoperable with many devices, and has a very reliable and robust network stack. It is suitable for the consumer market, and is starting to find some applications in industrial installations. Work is ongoing in the ZigBee alliance to merge all relevant ZigBee flavors in ZigBee 3.0.
IoT: You mentioned 6 LoWPAN. What are your thoughts on that technology?
Budek: 6LoWPAN is another network stack that runs on the 802.15.4 radio, and it can support lighting and other hardware devices as well. It is a self-healing tree network as opposed to a mesh architecture. Some industrial lighting applications prefer this type of network layer, especially in long thin installations. The JenNet-IP 6LoWPAN stack from NXP is a good example of this with already millions of devices shipped. Recently the Thread alliance also announced a 6LoWPAN stack but this is still in development and lacks currently a standardized application interface that can ensure interoperability between various devices.
IoT: You haven’t mentioned Bluetooth. How does this wireless technology fit into the LED lighting equation?
Budek: Bluetooth Low Energy (BTLE) is a newer network stack being considered for lighting. BTLE brings the promise of allowing control by a smartphone without the need for a bridge/gateway, unlike an 802.15.4 network, and the Wi-Fi router. BTLE however has some major disadvantages compared to Zigbee. First like Wi-Fi, BTLE is a star network so only short range (10m vs. 30m for ZigBee). Next, it can only control a group of six lamps simultaneously without having to un-pair (which would introduce huge latencies). This makes BTLE potentially acceptable for room control, but certainly not for a whole house application. Finally, BTLE is a single master network, so only one person at a time in the family can control the lights in the one room. These design issues with BTLE are currently limiting it for certain niche lighting applications.
Recently, a BTLE “mesh networking” stack has been announced for lighting. Further investigation shows that it is not a true mesh network but a flood network. Messages are broadcast to all nodes and repeated (retransmitted) by every node that receives the message. Because of this, a network with multiple control inputs, from say several smartphones and sensors, will quickly get flooded leading to larger latencies and even lost commands. In response, the BTLE-SIG has now started the development of a real mesh version. NXP is also an active contributor to this BTLE-SIG for mesh networks. This work, however, will not be finished until 2016. BTLE mesh networks for lighting applications will, therefore, not be available and certainly not stable enough for several years.
IoT: Thanks, Roman.