Electronic Design
Select the Right Network Protocol  for Your Connected-Home Device

Select the Right Network Protocol for Your Connected-Home Device

A network protocol using a low data rate is better sized for the simple command and control functions of connected-home devices; it's more cost-effective and can enable simulcasting.

Just in case you haven’t noticed, the home automation space is heating up fast. In 2014, technology giants from Google and Apple to Microsoft and Samsung have all made announcements regarding their particular stake in the race. 

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A growing number of manufacturers wish to join the connected-home parade, too. If you’re involved in designing new devices for the market, you should know that a handful of network protocols are vying for your attention. They include radio-only communication protocols such as Z-Wave and ZigBee, Bluetooth, and Wi-Fi, as well as hybrid technologies that use both powerline and radio. Each has its pros and cons. 

Z-Wave and ZigBee are going to head-to-head toward creating a connectivity standard, partnering with some heavy hitters in the electronics space. But when installed inside concrete walls or other RF-blocking locations, can radio alone deliver the absolute dependability consumers will demand?

Bluetooth encounters an even greater problem in that department with its limited range and node count. Wi-Fi is designed for large amounts of data, but suffers significant inefficiencies and overhead just to turn on a light. As home automation begins taking hold in the mass market, will Wi-Fi’s large data capabilities scale affordably? 

A few lesser-known, high-speed powerline protocols are also on the market. However, most are far too complex and expensive to be built into commodity products.

The truth of the matter is, similar to the mobile devices we interact with every day, different radio and powerline connectivity options will likely be available in the home to suit consumers’ specific needs and applications. However, if you were limited to only one network protocol for a connected-home product, the optimum technology should include simulcast capabilities and repeat mechanisms, distributed intelligence, and dual-band powerline and radio transmission to help ensure your integrations are as scalable, reliable, and affordable as possible. The protocol should also be able to coexist nicely with other network contenders as the connected home expands in the coming years.

Up to this point, networks inside the average home have been complex and required intricate hardware and software to implement. Broadband, for instance, needs sophisticated networking protocols to support the high speeds required to transport massive data to your PC. But what kind of network does it take to link together light switches, door locks, remote controls, and thermostats?

A protocol using a low data rate is better sized for the simple command and control functions of connected-home devices. In addition to being more cost-effective, a lower-data-rate protocol can enable simulcasting (a synchronous transmission of identical signals by all devices within range). Therefore, powerline and radio signals can increase signaling energy over their respective media without infringing regulatory limits. Impractical with higher-data-rate protocols, simulcasting radically increases reliability.

With lower data rates, devices can be peers as well by transmitting, receiving or repeating other messages without requiring a master controller or complex routing software. Adding more devices creates a more robust network, because devices can repeat each other’s messages by simulcasting them at precisely the same time. In other words, the network actually gets stronger with more devices.

Product design engineers should also consider whether the protocol they choose possesses built-in distributed intelligence. This intelligence not only makes the products easy to install, but as electronic home-improvement devices are added, they can all “talk” to each other and become part of a home control network.

Products incorporating the leading radio protocols often cannot communicate with other products from different manufacturers, nor, in some cases, with devices that incorporate earlier versions of the protocol. Consumers may also need a network controller and enrollment for each device, setting up installation hurdles to multi-node, fully automated homes.

Shown is an example of simulcast signal improvements on powerline, using one originator (five data packets) and then 5 simulcast repeaters (first three of five data packets) on an oscilloscope. The simultaneous repeated signals are significantly greater in amplitude than the original transmission.

A dual-band powerline and radio transmission network can solve the limitations exhibited by these technologies when used individually. Dual-band communications ensures that messages can travel multiple physical pathways, creating redundancies that reduce the possibility of a message not getting through and strengthening reliability.

Dual-band devices also solve a significant problem encountered by networking technologies that can only communicate via the powerline. Electrical power is most commonly distributed to homes in North America as split-phase, 220-V alternating current (220 V ac). At the main electrical junction box to the home, the single three-wire 220-V ac powerline is split into a pair of two-wire 110-V ac powerlines, known as Phase 1 and Phase 2. Phase 1 wiring usually powers half the circuits in the home and Phase 2 powers the other half.

The problem is that powerline signals originating on one phase needing to reach a receiver on the other phase are severely attenuated, because in many cases there’s no direct circuit connection for them to travel over.

A traditional solution to this problem is to connect a signal coupling device between the powerline phases, either by hardwiring it in at a junction box or by plugging it into a 220-V ac outlet. The powerline phase coupling problem can be solved through the use of dual-band devices—RF messages can automatically couple the phases when received by a dual-band device on the “other” phase.

In addition, you will want to make sure the protocol you choose has simple and affordable IP connectivity via Ethernet, USB, and serial bridges to allow for communications with the Internet, computers, smartphones, tablets and wide variety of security and wiring panels.

The five images below represent, in 2D and only on one physical layer, the propagation of a simulcast signal in a cluster of nodes:

 

Each circle represents an Insteon-compatible product. The “T” represents the transmitter (e.g., a keypad you are pressing), and the “R” represents a receiver (e.g., a switch you want to control remotely).

In a typical home, the original message will reach the majority of the Insteon-compatilbe products in the house.

On this screen and the following screens, you’ll see how Insteon gets the signals to every product in the home. As each Insteon-compatible device is a repeater, every product in the home that received the original tramsmission repeats the message simultaneously. These “simulcasts” build on one antoher like musical instruments in a symphony, greatly amplifying the signal. Most, if not all, products will receive the first repeated signal, if they haven’t alread y received the original signal.

As a factor of safety, another repeat is sent. Again, every product that received the transmission, either the original or the first repeat, will now repeat the transmission again. With almost the entire network repeating the message, virtually every device in an Insteon network will receive the signal.

While rarely required, a third repeat of the transmission goes out to further boost reliability.

Imagine, a TV automatically turns on the surroundsound amplifier; a smart microwave oven downloads new cooking recipes; a thermostat automatically changes to its energy-saving setpoint when the security system is enabled; bathroom floors and towel racks heat up when the bath runs; or an email alert goes out when water is in the basement.

This is the world craved by many consumers, and it’s only the beginning. With the right network features, your product will be ready for what the future brings.

Download this article in .PDF format
This file type includes high resolution graphics and schematics when applicable.

Dan Cregg, CTO of Insteon, has been in the smart-home space for over 20 years and was part of the Insteon team that gave the world the first network-controlled bulb in 2012. He founded HomeRun Automation and SmartLinc, which were purchased by Insteon’s corporate entity, SmartLabs, in 2000. Cregg holds a Master’s degree in engineering from California State University, Long Beach, and is an adjunct professor as well as a member of the engineering school's executive advisory council.

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