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Wireless Communication for Wearable Devices

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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

Published in: Devices & Hardware
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Wireless Communication for Wearable Devices

  1. 1. Wireless Communication for Wearable Devices Howard M. Harte – November 8, 2014 hharte@cyngn.com
  2. 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. 3. Anatomy of a Smart Watch
  4. 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. 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. 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. 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. 8. Example Wearable Software Stack (courtesy of Samsung)
  9. 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. 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. 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. 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. 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. 14. Thank You

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