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New-Tech Magazine Europe l 31
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
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
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