What are Broadcasting Power, RSSI and other characteristics of a beacon's signal?

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There’s a handful of terms that will help you better understand how beacons work. Most of them describe signal characteristics and the way beacons communicate with mobile devices:

  • Broadcasting Power
  • Advertising Interval
  • RSSI
  • Measured Power
  • Proximity zones

Broadcasting Power and Beacon’s Range

Broadcasting Power (or Transmit Power) is the power with which the beacon broadcasts its signal. In Estimote Beacons, you can change it with the Estimote SDK, the Cloud interface, or the app.

The value ranges from -40 dBm to +4 dBm.

Note that there are some exceptions:

  • Proximity Beacons ordered before mid-2016 (hardware revision "D") have the minimum value of -30 dBm.
  • Location Beacons (hardware revision "F") support the minimum value of -30 dBm.
  • Location Beacons with long range (hardware revision "F3.3") have the maximum option of +10 dBm.

 

 

Broadcasting Power directly impacts signal range. The more power, the longer the range. Increasing the power can also make the signal more stable, but keep in mind it can have a negative effect on battery life.

The beacon’s range is technically up to 70 m (+ 4dBM). In real-world conditions, however, you should expect up to 40-50 m.

The long-range Location Beacons' signal travels for up to 200 m. 

Estimote Stickers have a range of up to 15 m.

Advertising Interval

Beacons do not broadcast constantly. They ‘blink’ instead. Advertising Interval describes the time between each blink. Just as with Broadcasting Power, Advertising Interval on beacons can be adjusted with Estimote SDK, Cloud, and the app.

The value ranges between 100 ms and 2000 ms. The shorter the interval, the more stable the signal. Keep in mind that adjusting Advertising Interval will impact battery life in a big way.

In the case of Estimote Stickers, the interval is adjusted automatically, depending on the sticker’s state. You can read about it in detail on our Developer Portal.

RSSI

RSSI stands for Received Signal Strength Indicator. It is the strength of the beacon's signal as seen on the receiving device, e.g. a smartphone. The signal strength depends on distance and Broadcasting Power value. At maximum Broadcasting Power (+4 dBm) the RSSI ranges from -26 (a few inches) to -100 (40-50 m distance).

RSSI is used to approximate the distance between the device and the beacon using another value defined by the iBeacon standard: Measured Power (see below).

Due to external factors influencing radio waves—such as absorption, interference, or diffraction—RSSI tends to fluctuate. The further away the device is from the beacon, the more unstable RSSI becomes.

Read How precise are Estimote Beacons? for more information.

Measured Power

Measured Power is a factory-calibrated, read-only constant which indicates what's the expected RSSI at a distance of 1 meter to the beacon. Combined with RSSI, it allows you to estimate the distance between the device and the beacon.

Proximity zones

iBeacon defines four proximity zones for estimating the distance to a beacon. Keep in mind, these are approximations.

  • immediate (very close to the beacon)
  • near (about 1-3 m from the beacon)
  • far (further away or the signal is fluctuating too much to make a better estimate)
  • unknown.

 

 

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31 Comment(s)

  • Avatar
    Gema Megantara

    On the above it was said :

    "As RSSI is derived from TxPower, changing TxPower will change the value for measured power"

    "Our default configuration sets TxPower at -12 dBm which reflects measured power at -74 dBm"

    I already do the calibration on the estimote beacon using the AirLocate app, and got the calibration value is -59. How can I set the measured power of the estimote beacon to -59 ? since I can only change the TxPower on the estimote and I don't know which TxPower value that relate with measured power equals -59

    Thanks.

  • Avatar
    Ula Kierwiak

    Hi Gema,

    Thanks for your question!

    You can't set the measured power of a beacon. We calibrated it in our laboratories to the best possible setup and we don't allow to change it.

    However, we consider changing it in the future, so it will allow setting the measured power to your desired values.

  • Avatar
    Werner Schnedl

    Hi

    How can I read the TxPower (the physical power of the transmitted signal of the iBeacon) with standard iOS methods and without a SDK.

    Werner

  • Avatar
    Wojtek Borowicz

    Hi Werner,

    It's not possible with Core Location, but you can use Core Bluetooth for that:
    writeValue:forCharacteristic:                                   type
    - (void)writeValue:(NSData *)data forCharacteristic:(CBCharacteristic *)characteristic type:(CBCharacteristicWriteType)type

    Let me know if there's anything else.

    Regards.

  • Avatar
    Christian Melchior

    After having read other iBeacon specs, I am a bit confused about your terminology.

    Most others seems to agree that TxPower sent from the iBeacon is the RSSI one meter away. Essentially what you call Measured Power.

    Is there a reason you chosen another terminology?

  • Avatar
    Agnieszka Steczkiewicz

    Hi Christian,

    Thanks for that question. We use "Measured Power" term according to the Apple iBeacon documentation:

    "measuredPower
    The received signal strength indicator (RSSI) value (measured in decibels) for the device. This value represents the measured strength of the beacon from one meter away and is used during ranging. Specify nil to use the default value for the device."

    it is used in CLBeaconRegion class reference.

    Hope it helps!

  • Avatar
    Tianhao Li

    Hi Ola,

    Thanks for sharing the information related to RSSI and actual distance. I'm a college engineering student and have worked with estimote beacon for half a year.

    One question I have always wanted to ask is what brand (type) of on-board antenna estimote beacon PCB is using. Since there is a limit on how much accuracy I can improve using approximation methods like Least Squares and XY-ratio, I would like to research into the RF propagation profile of this specific type of on-board antenna so I can adapt my Kalman Filter towards it.

    If you're authorized to share this info that would be great! Thanks a bunch.

  • Avatar
    Ula Kierwiak

    Hi Tianhao,

    I'm afraid this information is confidential and we can't share it with you. I hope it won't ruin your work.

  • Avatar
    aditya arun

    Hi All,

    I am trying to use the beacons to measure distance indoors, but the value generated by computeAccuracy varies a lot. Sometimes when I am next to the beacon, it will show 1m and when I am 10 metes away it will show 3 m - 13 m.

    The distance keeps on varying even though I am not moving. Is there any way to achieve better accuracy ?

    With Best Regards
    Aditya

  • Avatar
    Witek Socha

    Hi Aditya,

    The iBeacon standard is not primarily designed for indoor positioning. Remember that Bluetooth signal is a 2.4 GHz radio wave and as such is susceptible to factors like absorption, diffraction, interference and multipath propagation. Because of that, to achieve more than 5-6m accuracy using trilateration, you need really advanced noise cancelling algorithms.

    It's also possible to use an alternative method, we call cell network system. It requires use of multiple Beacons to more precisely track user's movement and location. Programming part is a bit easier with such solution, but much more Beacons are needed.

    We've just released a new SDK for Indoor Location. It allows for mapping and tracking location with average accuracy of 1 meter. It's still in early phase of development, but we're planning to add some exciting features soon, including combining two or more locations and Estimote Cloud integration. You can read more about it right here: http://estimote.com/indoor/

    Best,

  • Avatar
    Firas Ataya

    Hello,

    I'm looking for a way to change the Estimote Beacon range using the android SDK, I want to let the user change it using a slider, just like the Estimote iOS app. is it possible to do that using the Android SDK? and if so what characteristics should I change?

  • Avatar
    Piotr Krawiec

    Hey there,

    Take a look at the writeBroadcastingPower method.

    The Characteristics Demo should also be of help. It's one of the demos bundled with the Android SDK.

  • Avatar
    Firas Ataya

    sorry but I have another question regarding the connection with the beacons, sometimes when I try to connect to a beacon using the SDK I get authentication error even though I'm near the beacon, I need to know when this error exactly happens?

  • Avatar
    Piotr Krawiec

    Can you let me know the exact error message? Thanks!

  • Avatar
    Firas Ataya

    Hi, thanks for your response, actually I'm using the Android SDK, what's happening is that after I call the authenticate function, the "onAuthenticationError" callback function is called, I haven't been able to read any error message or to know about the error and when it usually happens.

  • Avatar
    Fahim Zafari

    i am trying to convert obtain the distance using RSSI. what formula should i go with? I found RSSI[dbm] = −(10n log10(d) − A) online where A is the the offset which is the measured RSSI 1 meter point away from the BLE device. Can you guys provide me with that? I am able to obtain the rssi values,now how do you interpret that into distance?

  • Avatar
    Wojtek Borowicz

    Hi Fahim,

    You do not need to calculate the distance from RSSI yourself, because Core Location and Estimote SDK can do that for you :) The 'distance' property does that: http://estimote.github.io/iOS-SDK/Classes/ESTBeacon.html#//api/name/distance

    Cheers.

  • Avatar
    Fahim Zafari

    Hi,
    Thanks a lot for your reply. Actually I have estimote beacons but I am working on them for my research, trying to explore ways how can the positioning accuracy be enhanced, therefore I want to know the techniques how RSSI can be interpreted in terms of distance.

  • Avatar
    Wojtek Borowicz

    Hi Fahim,

    Unfortunately, we do not make the formula for calculating the distance from RSSI public, sorry!

  • Avatar
    Fahim Zafari

    Oh Okies! Thanks a lot. what about the measured RSSI value that u guys have at 1m?

  • Avatar
    Wojtek Borowicz

    It depends on the broadcasting power you set on your beacons :)

  • Avatar
    Khaled Mohamed

    Hi I would like to ask question about RSSI Value
    do you use Kalman Filter to enhance RSSI Reading ?

  • Avatar
    Wojtek Borowicz

    Hi Khaled,

    I'm sorry, but as mentioned above in conversation with Fahim, we do not publicly disclose details about how proximity is calculated in Estimote SDK or Indoor Location.

    Hope it won't be a problem.

    Cheers.

  • Avatar
    Gustav Ehrenborg

    Fahim's question above:
    What about the measured RSSI value that u guys have at 1m?
    ... when the beacon broadcasting power is turned up to max?

  • Avatar
    Wojtek Borowicz

    H Gustav,

    Sorry for the late answer! The Measured Power (RSSI value expected at 1 meter distance from the beacon) for maximum power setting is -60 dBm.

    Cheers.

  • Avatar
    Chuan

    Hi
    As to the measured power, which you mentioned is configured in the factory and could not be changed afterwards. However, with the beacon used for a few time, say 3 months, the power is lower and I expect the measured power should be lower, too. Will this be a problem?
    Thanks

  • Avatar
    Wojtek Borowicz

    Hi Chuan,

    You can adjust the Broadcasting Power of beacons (it's not possible for now with stickers). Keep in mind though that as you change the value of Broadcasting Power, Measured Power will change as well.

    Cheers.

  • Avatar
    ahmad reshad ahmadi

    Hello

    I need to set the distance, power and time whic the beacons are broadcasting their data and I want to this with Raspberry Pi Mini Computer. Could you please advise me a good example or article for this.

  • Avatar
    Wojtek Borowicz

    Hi Ahmad,

    You can find some tips on using beacons and Raspberry Pi among the resources listed here: https://community.estimote.com/hc/en-us/articles/202254358-How-do-I-build-my-first-app-

    Keep in mind that if you want Raspberry Pi to pick up any data from beacons, you'll first need to parse the signal yourself, as there is no RasPi SDK availble right now.

    Cheers.

  • Avatar
    Amin Nikravan

    Hi,

    I have two questions:
    - Is the distance calculated by Core Locations and SDK only a function of RSSI and Measured Power?
    - Does the Measured Power differ from device (smartphone) to device or you use the same value for all devices? I presume the the front end gain/loss characteristics of smartphones are different, right?

    Thanks,

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