New-Tech Europe Digital Magazine | Feb 2016

within range, typically somewhere between 5 metres and 50 metres of the beacon. Key design criteria for beacons are that the infrastructure around them does not restrict where they can be placed, so they need to be small and unobtrusive. And, as with most consumer electronic devices, low cost is crucial. Bluetooth Smart differs from Classic Bluetooth in a number of important ways that make it an attractive option for beacons: Classic Bluetooth radios typically draw around 40 mA at 3 volts but best-in-class Bluetooth Radios producing 0 dBm output (a power level perfectly suited to most beacon applications) can draw less than 5 mA at 3 volts while still offering a range of up to 50 m in many environments. Average power consumption in some applications may be only 100th of that of Classic Bluetooth, due to the relatively long periods during which a Bluetooth Smart device will be in sleep mode. Wake up time is just 6 ms, versus around 100 ms for Classic Bluetooth. It can send authenticated data in just 3 ms, versus up to 1 second for Classic Bluetooth. It offers 128-bit banking-level (AES-128) security to keep data safe. Not all Bluetooth Smart implementations are created

equal Despite the energy savings promised by Bluetooth Smart, how the technology is implemented can have a dramatic affect on system energy consumption and battery life. The primary criteria for choosing a Bluetooth Smart radio system-on-chip (SoC) to form the heart of a beacon are peak current consumption, energy consumption over time (taking into account the requirements of the application), receiver sensitivity (the beacons need to receive a signal from your smartphone to know that you’re in range), and the ability to work from a single small battery, usually a coin cell, to keep the size down. In real- world applications, battery life will also depend upon the advertising

interval - how often the beacon is required to transmit data - so when comparing device data, you need to ensure that the operating conditions under which the figures are quoted are the same, or at least very similar. To gain a more detailed understanding of how energy is consumed while a beacon is operating, you need to determine the charge consumed versus time for each advertising operation. These parameters include: The advertising interval and charge per advertisement The time taken and charge consumed from cold boot until the first advertisement The time, peak current and charge consumed by each of the

Figure 1: Bluetooth Classic and Bluetooth Smart compared

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