Power Consumption

Sections of this article provide information which can help in understanding different power modes of the uBeacon hardware and impact of different settings on the energy consumption

Overview

The beacon has the following states each of which has different energy requirements:

  • Sleeping - In this state uBeacon does consume only the minimal amount of energy needed to keep the chip in "standby" state and to keep the RTC chip up to date.
  • Advertising - In advertising mode the radio of the device changes between idle and transmitting mode at regular intervals. When radio is idle it is consuming a bit more energy than in sleep mode. When the radio transmits it draws a short peak of current to send the data and quickly returns to idle state. The height of the peak is dependent on transmitter power.
  • Connected - When connected uBeacon consumes a constant amount of current with peaks at regular intervals. The device needs to be in connected mode only for setting it up so it is not common in regular life-cycle of a beacon.

In more technical details the oscillograms below show how current consumption cycle looks for a device advertising with TXPower set to 5 and advertising interval to 100ms:

peaks.jpg

A zoom in view of a single peak is shown below:

peak_detail.jpg

Saving power

In order to save power the following tips may come in useful.

Reduce TX power settings

If you don't need to cover a very big area it is good to reduce the TX power value to suit your environment. Reducing TX power from maximum value can give up to 40% of reduction of the peak current value.

If you take a look at the oscillogram above, reducing TX power makes the peaks smaller which in turn accumulates in saved power on the battery.

Reduce advertising interval

For best performance it is advised to advertise at 100ms interval but in some cases this might not be necessary. Since the peak current (when transmitting) is quite big comparing to the idle current, removing a few advertisement messages can make a big difference.

If you take a look at the oscillogram above, increasing advertising interval makes the distance between peaks bigger which in result means less power used overall in a given period of time.

Use scheduling

Scheduling can be used for situations when the beacon doesn't need to advertise 24/7. If you have a store open between 9-20 you can set up the beacon to turn on at 8 and turn off at 21. This gives a saving of 11hours per day. When the beacon is sleeping it consumes almost no energy.

Disable not used features

If you are not using mesh it's advised to disable it since it adds up to the overall power consumption of the beacon. Refer to the " Mesh " section below for more in-depth explanation.
You can also disable LED indicator to further reduce the energy consumption. uBeacon LED is not used very often but still when it's blinking it consumes a small amount of energy. If visual indication of different uBeacon states is not necessary the LED can be turned off.

Mesh

Mesh is a way for exchanging short messages between beacons which doesn't require them to connect with each other and is working without interrupting regular iBeacon advertisement messages.

All devices involved in mesh communication need to stay active to receive messages. As mesh is done over Bluetooth Low Energy radio the receiver needs to stay active which makes the energy consumption increase greatly. It is highly advised to keep mesh enabled devices connected to a charger for continuous operation.