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SIGNAL CHAIN BASICS (Part 35): ANT–A unique option for wireless sensor networking

(Editor's note : there is a complete, linked list of previous installments of the Signal Chain Basics series below the About the Author section at the end.)

It's quite an amazing time to be working with low-power wireless, focused on technologies that include IEEE 802.15.4, ZigBee™, RF4CE, Bluetooth® Low Energy (BLE), and ANT™.

Earlier in the Signal Chain Basics series, we published a few articles ranging from the lower layers of these short-range, low-power wireless solutions to the application layer. Determining which market spaces and products these technologies are most suitable is very exciting. Also, determining which standard or proprietary solution that is most appropriate for different solutions in different markets such as home automation, smart metering, industrial monitoring, remote control or consumer electronics presents its own form of challenges. New standards such as ANT and BLE promise to be an extensive market space and continue to grow.

The ANT+ Alliance Symposium took place on October 5 – 7, 2009. Participants included premier sports and fitness equipment manufacturers that build state-of-the-art body-worn sensors, and expanded into other markets such as consumer health, medical and more. As a follow-up to this conference, I'd like to discuss ANT and ANT+ technology, and the ecosystem it supports.

ANT is an ultra-low-power solution that operates in the 2.4 GHz space and supports point-to-point, many-to-one (star), and even many-to-many (extended tree and potentially multi-hop) topologies. The “special-sauce” of ANT is that the ANT transceiver (containing the RF communication and software protocol stack) is isolated with an extremely easy-to-use interface into a black box, and isolates the system's RF / networking component as shown in Figure 1 . Inside this black box, ANT supports bi-directional and uni-directional logical channels independently, managed by a slave and master endpoint.



Figure 1: ANT/ANT+ OSI protocol stack breakdown


ANT implements truly low-power communication (achieving years of operation out of a small coin cell battery). It provides diversity of supported network topologies, implements pairing with secure communication, allows sophisticated file transfers, and does so through an extremely easy-to-use serial interface to which virtually any MCU can connect.

Figure 1 also shows the OSI equivalent for ANT and ANT+. The ANT+ profile or application level “standard” builds on ANT to homogenize interaction and communication between devices that interoperate or share data within an operational network. Interoperability allows multiple vendors to build products without direct collaboration, and sell those products into an ecosystem comprising complementary sensors within a specific market space.

An example is in the bicycle community where one company builds a bike computer that monitors sensors provided from several other specialized companies including heart rate straps, power, speed, cadence and other sensors that allow bike riders to achieve peak training and performance. In addition to supporting the biking community, ANT+ has profiles to support indoor (gym) and outdoor fitness, wellness, health, control (MP3 players or other devices), with several other profiles currently in development. ANT also bridges (to integrate ANT into other technologies like Wi-Fi), and has many additional profiles under development.

Through the simple API, ANT is designed for sensor and control networks utilizing master / slave connectivity when appropriate, but supporting broadcast communication or non-connection-based data transfer when appropriate. ANT slave devices can scan a network for potential connections (scanning algorithm optimized for low-power operation), potentially using proximity to differentiate between devices nearby or across the room.

Conclusion
Devices can use a low-priority search algorithm to maintain prioritized communication, while simultaneously establishing new connections. Communication is supported by up to eight channels, depending on which ANT transceiver is selected, where the ANT “master” controls the channel. Channel IDs are maintained through advanced channel management, and ANT channels allow transitions between available frequencies to combat any potential interference sources. For each channel of communication established, ANT also supports individual channel output power control.

Please join us next month as we continue our discussion on digital audio interfaces.For more information about other low-power RF solutions mentioned, visit http://www.ti.com/lprf-ca.

About the Author
Brian M. Blum is a Product Marketing Engineer with Texas Instruments, where he is responsible for 802.15.4 and ZigBee Low Power RF product line. He received his Master's of Computer Science w/ focus on Wireless Sensor Networking from University of Virginia. In his spare time he enjoys rock climbing, volleyball, yoga and nature. Brian can be reached at lpw-pme-zigbee@list.ti.com.

Previous installments of this series:

  • SIGNAL CHAIN BASICS (Part 34): Designing the audio-signal chain for non-audio experts (Part 2), click here
  • SIGNAL CHAIN BASICS (Part 33): Use an op amp to drive a precision ADC, click here
  • SIGNAL CHAIN BASICS (Part 32): Digital interfaces (con't) — The I2 C Bus, click here
  • SIGNAL CHAIN BASICS (Part 31): Digital interfaces (con't) — The SPI Bus, click here
  • SIGNAL CHAIN BASICS (Part 30): Protocol selection over IEEE 802.15.4 silicon, click here
  • SIGNAL CHAIN BASICS (Part 29): Digital interfaces – Single-ended versus differential interfaces, click here
  • SIGNAL CHAIN BASICS (Part 28): Building (Electrical) Bridges, click here
  • SIGNAL CHAIN BASICS (Part 27): Control EMI resulting from board-level clock distribution, click here
  • SIGNAL CHAIN BASICS (Part 26): How to close timing on High-Speed ADCs, click here
  • SIGNAL CHAIN BASICS (Part 25): Designing the audio-signal chain for non-audio experts, Part 1, click here
  • SIGNAL CHAIN BASICS (Part 24): Basic networking using the IEEE 802.15.4 PHY/MAC protocol, click here
  • SIGNAL CHAIN BASICS (Part 23): EIA-485: Receiver equalization boosts networking performance, click here
  • SIGNAL CHAIN BASICS (Part 22): Phantom microphone power–the ghost in the machine, click here
  • SIGNAL CHAIN BASICS (Part 21): Understand and configure analog and digital grounds, click here
  • SIGNAL CHAIN BASICS (Part 20): Understand the basics of op amps and speed, click here
  • SIGNAL CHAIN BASICS (Part 19): Exploring and understanding linear voltage regulators, click here
  • SIGNAL CHAIN BASICS (Part 18): The op amp as integrator, click here
  • SIGNAL CHAIN BASICS (Part 17): Hysteresis–Understanding more about the analog voltage comparator, click here
  • SIGNAL CHAIN BASICS (Part 16): Understanding the analog voltage comparator, click here
  • SIGNAL CHAIN BASICS (Part 15): Analog/digital converter–dynamic parameters, click here
  • SIGNAL CHAIN BASICS (Part 14): Analog/digital converter–static parameters, click here
  • SIGNAL CHAIN BASICS (Part 13): Putting the Bode plot to use, click here
  • SIGNAL CHAIN BASICS (Part 12): The Bode plot, an essential ac-parameter display tool, click here
  • SIGNAL CHAIN BASICS (Part 11): Introducing voltage- and power-conditioning circuits, click here
  • SIGNAL CHAIN BASICS (Part 10): Exploring the Delta-Sigma Converter, click here
  • SIGNAL CHAIN BASICS (Part 9): SAR Converter Operation Explored, click here
  • SIGNAL CHAIN BASICS (Part 8): Flash- and Pipeline-Converter Operation Explored, click here
  • SIGNAL CHAIN BASICS (Part 7): Op Amp Performance Specification–Bias Current, click here
  • SIGNAL CHAIN BASICS (Part 6): Op Amp Input Voltage Offset, click here
  • SIGNAL CHAIN BASICS (Part 5): Introduction to the Instrumentation Amplifier, click here
  • SIGNAL CHAIN BASICS (Part 4): Introduction to analog/digital converter (ADC) types, click here
  • SIGNAL CHAIN BASICS (Part 3): Analog and the digital world, click here
  • SIGNAL CHAIN BASICS (Part 2): Op Amp–Basic operations, click here
  • SIGNAL CHAIN BASICS: Operational Amplifier–The Basic Building Block, click here

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