Overview of wireless communication technologies used today in Wearable and IoT devices. This was presented at the SIPA Wearables Conference on November 8, 2014. A video of the presentation is available here, starting at 32 minutes into the clip: https://www.youtube.com/watch?v=BbueyK_dNDI

1. Wireless Communication
for Wearable Devices
Howard M. Harte – November 8, 2014
hharte@cyngn.com

2. Wireless Technologies for Wearables
Several technologies are being used today in wearables, with
Bluetooth being the most prevalent.
 Bluetooth Low Energy (BLE)
 Low power, low data rate, <100 meter range.
 Wireless LAN (WiFi)
 Medium power, high data rate,100 meter range.
 Near Field Communications (NFC)
 Low power, low data rate, short range (20 cm.)
 Mobile network (GSM)
 GPS for positioning.

3. Anatomy of a Smart Watch

4. Bluetooth SMART (BT 4.1, Bluetooth Low
Energy, BLE)
 Good for medium range communication at low data rate.
 Very low stand-by current, maximum current consumption < 15mA.
 Data Rate <1Mbit/S.
 Radio operates in 2.4GHz frequency band
 Uses Frequency Hopping Spread Spectrum (FHSS.)
 Bluetooth and WiFi can interfere with each other since they both use the 2.4GHz
band.
 iOS and Android provide API support for BLE.
 Android 5.0 introduced Bluetooth SMART Peripheral Role.
 BLE devices can Advertise their presence to nearby devices.

5. Wireless LAN (WiFi)
 Medium to long-range, high data rate, medium power consumption.
 Peer-to-Peer communication alleviates the need for a infrastructure network
 Two devices can communicate directly with each other using WiFi-Direct (P2P.)
 One device in “Group Owner” role. This role is similar to a WiFi Access Point. Usually this
will be the device with more battery capacity due to the increased current consumption in
the Group Owner role.
 Wearable in the “Group Client” role. This role is similar to a WiFi Station, and can take
advantage of standard WiFi power-saving modes.
 Radio operates in 2.4GHz or 5GHz frequency bands.
 Average standby current consumption ~1mA.
 Peak current can be much higher (>100mA) when transmitting.
 High data rate, >100Mbit/S for the latest 802.11ac devices.
 Even legacy 802.11g and 802.11n devices are >10Mbit/S.
 WiFi-Direct APIs are available in Android and Windows 8. Apple AirDrop is not
WiFi-Direct.

6. Near-Field Communication (NFC)
 Short Range, low data rate, low power consumption.
 Point-to-Point Communication between card and reader.
 Radio operates at 13.56MHz.
 Power consumption similar to Bluetooth SMART.
 Higher when illuminating a passive tag.
 Low data rate of 424Kbit/S maximum.
 Maximum distance of about 20cm.
 Two modes of operation:
 Passive communication (target device is not powered.)
 Active communication (both initiator and target are powered.)

7. Impact on Wearables
 Wearables today typically use Bluetooth LE. This is a compromise:
 Low power, but at the expense of data throughput.
 Limited range, and needs to be tethered to a host device such as a phone.
 Transferring large amounts of data (Photos, Music) between wearable and host takes
time:
 Creates a poor user experience
 Increases power consumption because the wearable’s CPU (and maybe even display) will be on
longer.
 Some wearables (such as Google Glass) use WiFi:
 Higher data throughput, but at the expense of battery life.
 Using WiFi, a wearable can connect directly to the Internet via a WiFi Access Point (AP.)
 Still others (Apple iWatch) combine BLE, WiFi, and NFC.
 NFC for Mobile Payments.
 Some wearables use GSM for connectivity when out of WiFi range.
 This trend is expected to increase going forward.

8. Example Wearable Software Stack
(courtesy of Samsung)

9. Applications for Wearable Devices
 Generally, App Developers don’t need to worry about how the
communications between smartphone and smartwatch are handled.
 For example, Android Wear and Samsung Gear provide transport-independent APIs
to transfer data between the device and phone.
 Sending a message to an Android Wear device:
Node node; // the connected device to send the message to
GoogleApiClient mGoogleApiClient;
public static final START_ACTIVITY_PATH = "/start/MainActivity";
...
SendMessageResult result = Wearable.MessageApi.sendMessage(
mGoogleApiClient, node, START_ACTIVITY_PATH, null).await();
if (!result.getStatus().isSuccess()) {
Log.e(TAG, "ERROR: failed to send Message: " + result.getStatus());
}

10. Implications for Developers
 Having an understanding of the underlying wireless technology can help
developers write better Apps that are:
 More efficient
 More responsive.
 Conserving of battery on both Wearable and phone.

11. Creating Your Own Wearable / IOT
Device
 Development Kits are available for Bluetooth SMART and WiFi:
 Broadcom WICED SMART
 $20 Development Kit for Bluetooth SMART (BLE.)
 Apps (with source code) for iOS and Android.

12. Broadcom WICED WiFi
 Trend is towards moving more networking
functionality into the WiFi module.
 Eases implementation.
 Reduces Power.
 Legacy Laptop/PC WiFi typically perform L2
and WiFi link management in the host.
 Current smartphones and wearables move
L1/L2 functionality into the WiFi Module.
 WICED moves all networking functionality into
the WiFi Module and presents a Sockets-based
interface to the host CPU.
 Development kit and module for WiFi-based
designs.
(Courtesy of Universal Scientific Industrial)

13. References
 http://developer.samsung.com/technical-doc/view.do?v=T000000160
 https://developer.android.com/training/building-connectivity.html
 http://www.broadcom.com/products/wiced/sense/
 http://www.broadcom.com/products/wiced/wifi/
 http://www.usish.com/english/products_wiced.php

14. Thank You