Sidewalk is a wireless protocol for IoT devices developed by Amazon, using BLE (Bluetooth Low Energy) for short-range connections and FSK or LoRa (Long Range) for long-range communications as modulation techniques. The available bandwidth is limited, making Sidewalk suitable only for transmitting small amounts of data (e.g., sensor data). Due to the low bandwidth and the use of modern wireless protocols, ranges of more than a kilometer can be achieved. Amazons own smart speakers like Echo and Echo Show serve as bridges (Gateways) between the end device and the cloud. This article explains how Sidewalk works and provides an initial practical test.

What can Amazon Sidewalk do?

With Sidewalk, Amazon is creating a wireless service that, as the name "Sidewalk" suggests, will reach right onto the sidewalk. In future, this will allow devices to be networked not only in the home, but also outdoors. A high density of sidewalk bridges makes it possible to operate your own devices in another city or even in another country without incurring high costs. Not only are the operating costs lower compared to mobile communications, but energy efficiency is also significantly better when using Sidewalk. Since 2023, Amazon has also been offering external developers the opportunity to test this wireless protocol and develop their hardware for Sidewalk. Amazon is also likely to launch its own products such as GPS trackers or temperature sensors on the market and offer a software solution for them.

Where Amazon Sidewalk already works

As of today (April 2024), Sidewalk is only available in the United States (mainland and surrounding islands such as Hawaii). In addition to BLE on 2.4 GHz, the ISM frequency band on 915 MHz (FSK/CSS 900) is also used for wireless data transmission in the United States. There is currently no information on whether and when Sidewalk will also be rolled out and activated in other countries. In the United States, Sidewalk has been available almost nationwide since summer 2021. There are no consumer devices for Sidewalk yet, only a GPS tracker (field tester) and some development boards from chip manufacturers such as Texas Instruments, Semtech or Nordic Semiconductor are available for developers.

How does Sidewalk work?

An end device (weather station, GPS tracker, etc.) sends the recorded data to a bridge either via BLE or FSK. The bridge or gateway (bridge between the wireless interface and the Sidewalk cloud) can be an Amazon Echo or Echo Show, for example. It makes no difference whether it is your own bridge in the household or a third-party bridge from the neighborhood. Every Sidewalk Bridge within a radius of a few kilometers is therefore a gateway for Sidewalk end devices. If at least one bridge receives data packets from an end device, these data packets are forwarded from the bridge to the Sidewalk network server via the Internet connection. The network server forwards the received data to a defined end point (e.g. app or website). The following diagram shows the topology of Amazon Sidewalk:

Sidewalk Bridge is enabled by default on supported devices in the United States and can be disabled in the Alexa app. According to Amazon, the Sidewalk service uses a maximum upload bandwidth of 80 kilobits, which should not be a problem for most internet connections. The maximum monthly data volume is limited to 500 megabytes.

When will Sidewalk be launched in Europe?

There is currently no information on when Sidewalk will be available in Europe. As with LoRaWAN, Sidewalk will also use the ISM band in the frequency range around 868 MHz for FSK/CSS.

Sidewalk - An alternative IoT network

Various IoT networks have been in existence for a number of years, which are often limited to a specific hardware manufacturer or national network provider. One example would be Apple with the AirTag, where every newer iPhone serves as a bridge or gateway for this tracker. This service is only available to Apple customers and currently only works with the AirTag or Apples own devices. The alternative would be LoRaWAN, but there is currently no nationwide network that covers the whole of Europe, for example. There are many network operators who set up their own LoRaWAN networks on a commercial basis, but again there is no roaming function, so there is usually no cross-border coverage. One exception is the Helium LoRaWAN, but this is also a community network based on crypto mining, which has been in decline in many places in recent years due to low mining yields. There is also the LoRaWAN network TTN (The Things Network), which can be used free of charge. However, here too, it is voluntary enthusiasts who are building this network and it is unlikely that it will ever be available nationwide. Mobile networks such as LTE-M and M2M offer an alternative, but are associated with higher operating costs.

From the IoT networks mentioned, you can see that every network has some disadvantages that Sidewalk partially eliminates. Now that Sidewalk can already be used by external developers, there should be a large number of devices for it in the future. The availability should be very good, as the possible bridges are already available and active in many private households. Of course, Sidewalk should not be expected to have the same availability as commercial mobile networks, but it will certainly be better than many LoRaWAN networks. It is not yet clear whether Sidewalk will remain free or be limited.

Security and data protection

Amazon has provided a White Paper on data protection for Sidewalk. As with LoRaWAN, the data to be transmitted is encrypted in the end device and only decrypted again at the network server. In between, intercepted radio signals cannot be decoded and the owners of a bridge cannot read any data. The network server does not pass on any sensitive information via the application interface, such as information on bridges that have received the data. It is not possible for third parties to determine the exact location of the bridges and end devices. If desired by the owner, the Sidewalk service can be completely deactivated on all devices via the Alexa app.

First test in Europe

Sidewalk can currently only be tested properly in America. If you want to test Sidewalk in Europe, you currently need an OPENVPN gateway with an American IP address to which bridges such as the Amazon Echo 4 are connected. Only the American ISM frequency range at 915 MHz is currently used for FSK/CSS. It is illegal to use Sidewalk with FSK/CSS on this frequency band in Europe! If you already want to test Sidewalk, you can carry out initial tests with various development boards and restrict the radio standard to BLE only. We highly recommend the LauchPad with the CC1352 from Texas Instruments, for which there is also a detailed tutorial on this blog. This board also offers the option of using Sidewalk exclusively with BLE wireless technology, which should enable test operation outside the United States. A request was made to the Austrian telecommunications authority for a special permit for research purposes with Sidewalk on FSK/CSS in the 915 MHz band, but this has not yet been answered. A range test on Amazon Sidewalk with the FSK/CSS radio standard could therefore not yet be carried out.