Bluetooth technology is reliable by design

Martin Woolley of Bluetooth SIG

Wireless communication systems usually employ radio as the underlying, physical basis to transport data from one device to another. Bluetooth technology is a radio communication technology, and radio technology is often seen as unreliable. With this in mind, a question arises can Bluetooth technology be described as reliable?

Interference challenges

One of the biggest issues that wireless technology faces in attempting to provide reliable data communication is interference, says Martin Woolley, senior developer relations manager, EMEA, Bluetooth SIG. Wireless solutions must share the transmission medium, and multiple devices may try to communicate over the same channel, in the same general area, and at the same time. When this happens, in-air collisions between data packets occur which can make a packet unreadable by the receiving device and effectively lost.

This challenge is especially true in unlicensed spectrum bands where a communications technology needs to accommodate potential interference from other devices using the same communications technology, as well as devices using other communications technologies that operate in the same band.

To circumvent potential interference, Bluetooth technology uses various techniques including adaptive frequency hopping and compact, efficient packets transmitted at a relatively high data rate.

Avoiding interference with adaptive frequency hopping

The risk of collisions is especially high in busy radio environments that contain large numbers of devices, transmitting data often. Spread spectrum techniques can improve the reliability of a wireless technology. Bluetooth technology mitigates the risk of collisions and avoids interference by using a spread spectrum method known as Adaptive Frequency Hopping (AFH).

Like all frequency-hopping spread spectrum (FHSS) technologies, Bluetooth divides the radio band it operates within into multiple, smaller radio channels (e.g. 40 in the case of Bluetooth Low Energy). Bluetooth technology hops between transmission channels to further decrease the probability of collisions with other in-range transmissions. Splitting the ISM band into 40 channels also has the benefit of increasing the overall capacity for communication.

The power of packets

When trying to avoid collisions, small and fast packets are proven to be the most efficient. For example, compared with other low power mesh networking technologies, Bluetooth mesh packets are typically half the size and are transmitted at 4 times the data rate.

Having small, fast packets enables more efficient use of spectrum and significantly lowers the probability of collisions. The small packet size of Bluetooth mesh and the high symbol rate of the Bluetooth LE radio reduces the required airtime for a packet and means that Bluetooth mesh networks fare well in this respect.

To put simply, as the smaller Bluetooth packets are less likely to be impacted by interference, its mesh networking is considered to be the first low power mesh networking technology capable of meeting the scalability and reliability demands of modern smart buildings.

Reliable wireless communication

It is clear that achieving full reliability is unlikely in any real-world system, whether it uses wire-based communication or radio technology. A system can fail in a great many ways, including those relating to communication of data.

However, Bluetooth-based technology was designed with reliability in mind. Using smaller and faster packets to transmit data as well as techniques such as AFH, Bluetooth is capable of achieving highly reliable communication in even the most challenging circumstances and helps product designers address the challenges of interference.

The author is Martin Woolley, senior developer relations manager, EMEA of Bluetooth SIG.

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