Amazon Sidewalk: A Technical Deep Dive
In September 2019 at the Devices & Services event, Amazon announced Sidewalk, a new low-bandwidth, low power wireless protocol, and hinted at building an ecosystem around it. Other than highlighting the 900 MHz spectrum usage, not many technical details have been officially released.
Before long, due to the lack of official information, the connectivity market started speculating what kind of technology Sidewalk was built upon.
I have followed numerous discussions like these about new technology over the past decade, but this one did not feel like it was heading in any meaningful direction. Additionally, most of what I read and heard was a high level management summary for the general public. I wanted to have a meaningful, fact-based discussion and I wanted the technical details rather than a general summary.
Because of that, I started my own research on Amazon Sidewalk. I researched Amazon’s history with Internet of Things and connectivity technologies, and found an indication of future products that could be Sidewalk-powered. I have collected my findings and all the publicly available evidence of what Sidewalk could be and produced this article.
Amazon Echo Plus and Echo Show
Starting with Amazon’s more advanced Alexa-powered smart speakers, Echo Plus and Echo Show, their IoT connectivity capabilities are no secret. They both have a built-in Zigbee modem. That means they can connect to Zigbee devices directly, without needing an external hub to translate the protocols.
Zigbee has a long history — the longest out of all technologies mentioned in this article. It is based on the IEEE 802.15.4 specification, and was released as a separate specification in 2003, more than 15 years ago. In general, Zigbee and 802.15.4 has a relationship similar to that of Bluetooth profiles and Bluetooth MAC layer. Arguably, the main motivation behind Zigbee is being able to produce generic smart home devices and smart home components that interact with those devices.
In alignment with the compatibility goals, the Zigbee Alliance (with support of Amazon, Apple and Google) announced on December 18, 2019 its plan to develop a new royalty-free connectivity standard, with the aim being to achieve compatibility between different vendors of smart home devices.
While this is great news for interoperability, it is unlikely that this is Sidewalk, given all the existing branding and history of the standard.
Amazon’s Acquisition of Eero
Amazon acquired Eero in March 2019. The 2nd generation of Eero hardware , including Eero Pro and Eero Beacons, was built with support for Thread.
From the perspective of branding, Thread is a well-known brand and a registered trademark of Google. Its stack is: PHY and MAC are IEEE 802.15.4–2006, network layer is 6LoWPAN, a standard method of running IPv6 networks on small low-power devices. Its routing is governed by Distance Vector Routing, and its transport is UDP + DTLS.
As such, Thread can be considered both an evolution of Zigbee and its competitor, as they are not compatible. However, like Zigbee, Thread is based on the IEEE 802.15.4 specification. Because thread and Zigbee have the same base, it would be possible (at least in theory) to add Thread compatibility to existing Zigbee devices through a software update. However, in practice, the ability to do this largely depends on specific hardware decisions made when building the devices and the architecture of the devices, which makes this an unlikely candidate for Sidewalk.
Amazon’s Acquisition of Ring
Amazon acquired Ring in 2018. Ring’s entire product portfolio was built on top of Z-Wave.
As with Thread, Z-Wave is a competitor of Zigbee and, while similar, is not compatible. Z-Wave’s underlying technology is not 802.15.4. It is also the only technology that highlights the usage of the sub-gigahertz (in US it’s 908.4 to 916 MHz) spectrum.
Due to lack of compatibility between Z-Wave and Zigbee, the Echo Plus and Echo Show cannot talk to Ring products directly. A hub would be required in order for these Alexa-powered devices to communicate with Z-Wave components. The Z-Wave Alliance says that “with a compatible smart hub, [some of Z-Wave Alliance products] may be voice controlled”.
Again, given the existing Z-Wave branding, it does not look like a suitable candidate for Sidewalk either. However, Amazon officially announced that Ring’s new lighting products are running on Sidewalk, so Z-Wave could provide some interesting clues to what Sidewalk evolved from.
What Sidewalk Is Not
The review of Amazon’s IoT devices reveals that Amazon has products that use three very different (and mutually incompatible) technologies: Zigbee, Thread and Z-Wave. Amazon’s overall marketing of products that are powered by these technologies is balanced, indicating that Amazon has no preference of one over the other.
Given the strength of the existing brands, Sidewalk is unlikely to be as simple as a label on top of Zigbee, Thread or Z-Wave. From Amazon’s marketing, it is also likely not a technology that bridges these three by addressing their compatibility issues.
Sidewalk: Amazon’s Own Horse in the Connectivity Race
Amazon has shown great aptitude in the connectivity area, and has expertise in the three technologies discussed above. The incompatibility of the technologies, along with recognition of Amazon’s competency in this area, leads me to believe that Amazon is building something new, something that is a better fit for applications than what is currently on the market. Enter Sidewalk.
Adding Sidewalk to the connectivity race means Amazon wants to have a horse of their own. They no longer want to solely rely on technology from third parties.
At the same time, it doesn’t mean all the bets are on their own horse. On the contrary. I would argue that Amazon’s size allows it to employ a hedging strategy to the IoT world, investing both in established technologies, and in building a technology of its own.
Surely Amazon wants to create something more advanced than what is currently available on the market. Perhaps something that works outdoors, can be used to build coverage from the bottom-up, can be shared between participants of the network, and has long range. Sound familiar?
A Link Between Amazon, Sidewalk and LoRa?
When Amazon announced Sidewalk at the Devices & Services event, Amazon provided some limited details about the technology. But it did not explicitly mention anything about LoRa or other radio technologies powering Sidewalk. However, based on my own experience in the LoRa ecosystem, my review of Amazon’s IoT products, and parallels to the language that the LoRa ecosystem has been using for ages, I strongly suspected a link between Sidewalk and LoRa.
Amazon shared that Sidewalk is a 900 MHz technology and that new wireless lighting devices were built and tested by Amazon in LA. Given that Ring has products in the 900 MHz band and was the only company acquired by Amazon with a portfolio of wireless lighting devices, it follows that Ring was the force behind the new wireless lighting devices Amazon was talking about. In a written statement released after the Devices & Services event, Amazon confirmed this.
A review of products Ring is preparing to launch into the market could provide clues as to the inner workings of Sidewalk. For any new wireless devices that are going to consumers in the US market, an FCC certification is needed. FCC certifications often provide technical details and, luckily for anybody seeking those details, FCC filings are public and could provide some concrete evidence.
Deciphering Ring’s FCC Filings for Lighting Products
Ring’s FCC filings indicate that, apart from other wireless radio technologies, Ring has built in a LoRa radio into the Ring Bridge and into a number of Ring lighting products: a spotlight, a pathlight and a floodlight. All of the outdoor lights are linked to Ring’s first known acquisition — Mr. Beams.
The Ohio-based Mr. Beams developed off-grid LED lights that are simple and easy to install without having to run wires through a home. These LED lights are LoRa-powered and were developed before Mr. Beams was acquired by Ring. This leads me to believe that the usage of LoRa technology was inherited by Amazon through the chain of acquisitions.
Nevertheless, at least in the lighting arena, Ring seems ready to use LoRa, if it is not already using it.
Do New Ring Smart Light Bulbs Speak LoRa?
In line with Amazon’s announcement of Sidewalk being used with lighting products, in January 2020, Ring filed an application for a smart light bulb. It is a PAR38 bulb, and it has been granted certification in the 915 MHz band as well as 2.4 GHz band.
Radio compliance tests for both bands were conducted and submitted to the FCC. The FCC reports indicate the 2.4 GHz band was tested for use with Bluetooth Low Energy (BLE). The test reports related to the 915 MHz band were less obvious. The results show a number of Frequency Hopping Spread Spectrum (FHSS) test cases that match frequency, bandwidth, and datarate of a typical LoRa transceiver.
The FHSS tests are in two categories, “bandwidth” and “datarate”.The “bandwidths” tested were 125kHz, 250kHz, and 500kHz. The shape of the spectrum appears to be a chirp spread spectrum. The “datarates” tested were 150 kbps, 50 kbps, and 5 kbps, and their spectrum resembles a FSK modulation.
Though this may resemble a Z-Wave radio, this is not the case. Z-Wave only operates at 40 kbps and 9.6 kbps for legacy devices. Additionally, the band for those datarates does not match either Zigbee or Thread.
Although the tests do not explicitly mention LoRa, there are not many spread spectrum technologies that use this kind of bandwidth in this frequency band, which indicates that LoRa is involved.
After researching and reviewing the above, I finally discovered a document called “Report_DSS”. Page 8 of the document states that the tests in the 915 MHz band are for “LoRa DTS” (Digital Transmission System), “LoRa FHSS”, and “FSK FHSS”.
Amazon, Ring Fetch and Iotera
Back in 2015, while exploring the competitive landscape of the US LoRa / LoRaWAN market, I stumbled upon a company called Iotera. Iotera was building a citizen-powered network for pet trackers. You would buy a pet tracker with a base station from them. The tracker would connect to your own base station, as long as it was in its range. Once it got out of range of the home base station, the tracker would connect to any other base station in the Iotera network — any base station of another customer.
Iotera was acquired by Ring in 2017, and as we already established, Ring was acquired by Amazon in 2018.
When Amazon announced Sidewalk in September 2019, Amazon also announced that the first use-case and reference design for Sidewalk will be a pet tracker. But it will not bear the Iotera branding. It is going to be called Ring Fetch.
The disappointing news is that Iotera always labeled their communication technology as their own, proprietary solution. Except for this Skyworks press release and Iotera’s FCC filing, there is no public information that reveals what long range technology Iotera used.
The FCC filing indicates a proprietary channel hopping scheme in the 900 MHz band, and 125 kHz, 250 kHz, and 500 kHz bandwidth. Furthermore, the spectrum charts from the test reports look just like the one of Ring’s smart light bulbs, and specifically state the use of chirp spread spectrum.
Overall, the Smart Light Bulbs and the Iotera devices have a number of similarities. As of today, there are no FCC filings for a Ring pet tracking device, so I can’t draw any formal conclusions. However, based on everything discussed above, I would bet the upcoming Ring Fetch pet tracking device will be surprisingly similar to the Iotera devices.
Amazon Sidewalk — Research Summary
Even though Amazon has made significant investments in Z-Wave, Zigbee, and Thread, none of these protocols are a good candidate for Sidewalk.
It’s also unlikely Amazon Sidewalk would be an overarching protocol, unifying the other protocols.
Given that Amazon officially announced that Ring’s new lighting products are running on Sidewalk and the communication technology for these lighting products do not match the specs of Z-Wave, Zigbee, or Thread, it is undeniable that Sidewalk does not run on Z-Wave, Zigbee, or Thread.
It appears that Sidewalk utilizes a technology similar to that used by Iotera, a company that Ring acquired in 2017. Iotera was building a pet tracking product that bears striking resemblance to what Amazon announced as Ring Fetch.
The common features of the underlying radio technology are
- 902 MHz — 928 MHz spectrum
- (chirp) spread spectrum with 125 kHz, 250 kHz and 500 kHz wide channels
- FSK with datarates of 150 kbps, 50 kbps and 5 kbps
To be even more specific, the FCC filings for all the lighting products and even the new smart lightbulb list LoRa in the test reports.
Although this has little to do with the MAC layer or the higher layers of the Sidewalk protocol, it outlines what underlying physical layer (radio technology) Sidewalk is likely going to leverage.
If the evidence I provide doesn’t seem enough, I leave it as an exercise to the reader to try to input the spread spectrum bandwidths into their favorite search engine and see what results come out, and how it aligns with my findings.
The bottom line is that Sidewalk is using frequencies that are on the course of getting standardized globally, and with modulation that allows for great range / datarate flexibility, spectrum usage, and optimal battery consumption. This will for sure be an advantage for future consumers of Sidewalk-powered devices when deciding which connectivity technology to use for their smart home.
