Near Field Communication (NFC)

NFC works best for wearables that require low power consumption. It involves the transfer of tiny amounts of data over a very short range, essentially by touching two devices together. The devices will switch between two different modes: Active and passive. The power consumption for NFC is similar to what we see in Bluetooth Low Energy, although higher when communicating with a passive tag.

If you need your wearable to transfer data over a longer range, you should look for other options.

Bluetooth Low Energy (BLE)

Today, most wearables are running on Bluetooth Low Energy (BLE, formerly called Bluetooth Smart).
This technology is known as an easy to implement, low-cost option that requires very little power from your wearable. Your product can be powered by a coin cell battery for months - even years in some cases. But BLE comes with a compromise: Your data throughput will be limited. As most wearables generally transfer very little data, product owners can usually live with this.

The BLE chip is small, and fits nicely into an esthetically pleasing wearable that is convenient for the user to wear. A line-of-sight range of up to 100 meters is possible.

Using BLE requires your device to be paired with a host, most usually a cellphone with an app activated.

If you plan for your wearable to transfer higher amounts of data frequently, Bluetooth Low Energy may not be the best choice. Limited data transfer capacity makes this technology unsuitable for audio and video streaming, for example.

ANT

The wireless network technology ANT is a good option for sports wearables. A subsidiary of Garmin, ANT is huge in the sports and fitness segment where it is typically used for monitoring of heart rate, cycling power, distance and speed. Many of today’s cycling and fitness brands use ANT for their wearables. In fact, it has almost become a de facto standard in cycling.

The sensors and other nodes will act as either slaves or masters within a wireless network. Each node can transmit, receive or even function as a repeater to increase the range of the network. You can configure the network to spend long periods in low-power sleep mode, consuming extremely little power. 

Bluetooth Classic

Initially a standard intended to cover a lot of use cases for wireless communication, Bluetooth Classic (originally named simply 'Bluetooth', of course) found its niche in audio. Today it is the de facto standard for audio streaming, whether from your smartphone to a headset, speaker or in-car multimedia system.

Compared to BLE, Bluetooth Classic provides much higher bandwith and therefore the application consumes more power. The network topology is limited and not suitable for large sensor networks.

Wi-Fi

If your wearable needs to transfer a lot of data with as little lag as possible, Wi-Fi is your best option. The technology is best when streaming huge amounts of data, like video, but its main drawback is high power consumption that will require daily battery charging.

By using Wi-Fi, your wearable product can connect directly to the Internet via a Wi-Fi Access point.

Google Glass uses Wi-Fi to transfer graphics at high data rates for a better user experience. But the high power consumption of the display, and the high CPU load, requires the consumer to charge the device frequently. Be aware that such charging requirements will be a very important factor in overall customer satisfaction. 

Cellular

In a similar way to how your smartphone operates, using a cellular radio means that your wearable device can talk directly to the cellular network. Although convenient, as there is no need for a bridge device such as a smart phone to access the cloud, today’s cellular technologies are not suitable for small wearable devices. Power consumption is high and the physical dimensions are usually rather large. In the future, we will see new cellular technologies that are more competitive in the wearable space. But we're not there yet.

The best of all worlds?

Some wearables combine different wireless technologies to take advantage of different aspects of each method. The Apple Watch uses Bluetooth Classic, BLE, Wi-Fi, and even NFC for mobile payments. Nordic Semiconductor is currently the only manufacturer delivering chips that support both ANT and Bluetooth Low Energy (BLE), as well as NFC - all in one low power, 'system on chip' solution.

Hopefully, you’re now a little clearer on which wireless technology is best for you. If you’re still struggling, consider your product priorities. Is it size, power consumption, user experience, cost, or something else? Once you're clear on the priorities for your wearable, your wireless communication options become a lot clearer, too.