EE Times Article - Choosing RF Protocols - Part II - Bluetooth/Bluetooth Smart
May 28, 2013
EE Times - 5/28/2013 - The RF protocols that developers use for industrial, scientific, and medical (ISM) applications must meet exacting requirements for robustness, reliability, and connectivity. Today, developers can choose among several good options.
This article gives designers the pros and cons of each of the five leading RF protocols − Wi-Fi, Bluetooth, Bluetooth Low Energy, ZigBee, and DECT – used for ISM applications. The article also explains which protocols are most often chosen for which types of applications. In this way, designers can make informed decisions as they develop devices for ISM applications. The expertise for this article comes from Symmetry Electronics' years of advising designers as a distributor specializing in RF.
Bluetooth is a short-range communications technology best known for its robustness, high levels of security, and low power consumption (range and power consumption are class dependent, see table below). Bluetooth devices create wireless personal area networks (WPANs) that operate in the ISM band. Low-cost transceiver microchips control each Bluetooth device.
Bluetooth Smart is a feature of Bluetooth Version 4.0, which is the most recent version of the standard. This feature enables wireless devices to operate within a short range (up to 50 meters) on coin cell batteries, making it ideal for portable devices. Bluetooth Smart features include ultra-low peak-, average-, and idle-mode power consumption, low cost, and multi-vendor interoperability. With Bluetooth Smart, developers and manufacturers can develop smaller form factor devices for markets such as healthcare, sports and fitness, security, and home entertainment.
Bluetooth devices connect by pairing, creating ad hoc networks called piconets. Each device in a piconet can connect to up to seven other devices and can also belong to several other piconets simultaneously, which means the connectivity options are vast. Bluetooth is easy to install and commission, ensuring personal safety (a technician does not need to be physically next to a device to configure it).
Bluetooth uses Frequency Hopping Spread Spectrum (FHSS) to "hop" between 79 different 1 MHz-wide channels in this band to avoid channel conflicts with other wireless technologies sharing the 2.4 GHz spectrum. Each pair of devices has its own frequency-hopping schema to help avoid conflicts with other technologies, including Wi-Fi or ZigBee devices operating on the band. Frequency planning also can help ensure that devices coexist on the same network.
Bluetooth offers high security. The combination of Bluetooth's frequency hopping technique and authentication and encryption functions, which enables devices to become invisible to other "unpaired" Bluetooth devices, means that Bluetooth is practically impossible for a hacker to access.
Common applications for Bluetooth include human machine interfaces (HMI) programming, and real-time control tasks in industrial environments such as automotive manufacturing, energy plants, and warehouses.
While health device manufacturers were already using Bluetooth wireless technology, they realized that they needed an interoperable wireless standard. The Bluetooth Health Device Profile provides an additional level of interoperability, enabling support for mobile, in-home, in-clinic and in-hospital applications. The profile allows health device "sources," such as blood pressure meters, weighing scales, and thermometers to interoperate with health device "receivers" or "sinks," such as PCs, PDAs, mobile phones and displays from various manufacturers.
In a hospital, Bluetooth transceivers might communicate information from portable patient monitoring devices (sources) such as ECG monitors and blood oximeters to monitoring stations (sinks). Home applications comprise those in which the sources might be pulse oximeters, glucose meters, weight scales, thermometers, or blood pressure monitors, for which the sink might be a cell phone, a PDA, tele-health station, or a personal computer.
Read Part III - Zigbee
Written by: David Beck - Director of Technical Marketing - Symmetry Electronics Corp.
This article originally appeared as an online article on eetimes.com.