By Wolfgang Keller
Draft
Originally written 2023-10-18
Last modified 2023-10-18
Under Understanding Bluetooth Range | Bluetooth® Technology Website [visited 2023-10-16T22:36:40Z] (German version: Verstehen Bluetooth Reichweite | Bluetooth® Technologie Website [visited 2023-10-16T22:37:35Z]), one can find an explanation of the Bluetooth range. At the bottom of this website, a Bluetooth Range Estimator is embedded as an iframe: Bluetooth Range Estimator [visited 2023-10-16T22:39:59Z].
Let's analyze the model that it uses. For this, we use the following ressources as basis:
The following explanations of the model parameters are directly quoted from the JavaScript source code part of the Bluetooth Range Estimator (https://www.bluetooth.com/tools/range-estimator/app.js?v=1.0.1 [visited 2023-10-16T23:38:05Z]):
Receiver Sensitivity (\([\mathrm{dBm}]\)): Receiver Sensitivity is the minimum power level required by an input signal to be identified by the receiver. A lower value for the receiver sensitivity means a longer range.
Path Loss: Path loss is the reduction in signal strength that occurs as a radio wave propagates through the air. Path loss, or path attenuation, occurs naturally over distance and is impacted by the environment in which the signal is being transmitted.
Transmit Power (\([\mathrm{dBm}]\)): Transmit Power is actual amount of power or radio frequency energy that a transmitter produces at its output. A higher value for the transmit power means a longer range.
Transmitter Antenna Gain (\([\mathrm{dBi}]\)): Transmitter Antenna Gain is a measure of the maximum effectiveness with which the antenna can radiate the power delivered to it by the transmitter towards a target. A higher value for the transmitter antenna gain means a longer range.
Receiver Antenna Gain (\([\mathrm{dBi}]\)): Receiver Antenna Gain is a measure of the maximum effectiveness with which the antenna can absorb incident power in a given direction. A higher value for the receiver antenna gain means a longer range.
For an explanation of the \(\mathrm{dBi}\) unit for the forward gain of an antenna, see for example dBi, dB, dBm dB(mW): Defined, Explained and Differentiated - Data-alliance.net [visited 2023-10-17T00:23:30Z].
One can choose between the following seven Bluetooth PHYs for Receiver Sensitivity:
By looking at (https://www.bluetooth.com/tools/range-estimator/app.js?v=1.0.1 [visited 2023-10-16T23:38:05Z]), one obtains the following model parameters and parameter ranges for the seven Bluetooth PHYs:
| Bluetooth PHY | Sensitivity (\((\text{min}, \text{recommendedMin}, \text{default}, \text{recommendedMax}, \text{max})\ [\mathrm{dBm}]\)) | Number of RF Channels |
|---|---|---|
| EDR 3M | \((-110, -93, -87, -83, -70)\,\mathrm{dBm}\) | \(79\) |
| EDR 2M | \((-110, -96, -90, -83, -70)\,\mathrm{dBm}\) | |
| BR 1M | \((-110, -95, -90, -83, -70)\,\mathrm{dBm}\) | |
| LE 2M | \((-110, -93, -89, -89, -70)\,\mathrm{dBm}\) | \(40\) |
| LE 1M | \((-110, -96, -94, -90, -70)\,\mathrm{dBm}\) | |
| LE 500K (coded) | \((-110, -101, -99, -97, -75)\,\mathrm{dBm}\) | |
| LE 125K (coded) | \((-110, -105, -101, -99, -82)\,\mathrm{dBm}\) |
Remark: Despite the fact that the maximum sensitivities of LE 500K (coded) and LE 125K (coded) are \(-75\,\mathrm{dBm}\) and \(-82\,\mathrm{dBm}\), in the GUI of the Bluetooth Range Estimator, one can nevertheless select smaller values (down to \(-110\,\mathrm{dBm}\)) for them.
In Europe and the USA, Bluetooth operates in the frequency range of \(2402\,\mathrm{MHz}-2480\,\mathrm{MHz}\). At the bottom of this range, there exists a guard band of \(2,\mathrm{MHz}\), and at the top a guard band of \(3.5,\mathrm{MHz}\). If one includes these guard bands, Bluetooth operates in the range of \(2400\,\mathrm{MHz}-2483.5\,\mathrm{MHz}\):
The model uses \(2440\,\mathrm{MHz}\) as default frequency.
One can choose between the following four environments for Path Loss:
Under Path Loss (Propagation) Models [visited 2023-10-16T22:58:08Z], it is documented that the following models and model parameters are used for the four environments:
| Environment | Model | Link Margin | Tx Antenna Height | Rx Antenna Height | Range estimate (\((\text{min}, \text{max})\ [\mathrm{m}]\)) |
|---|---|---|---|---|---|
| Outdoor | Two-Ray Ground Reflection Model
|
\(15\,\mathrm{dB}\) | \(1\,\mathrm{m}\) | \(1\,\mathrm{m}\) | - |
| Industrial | Log-Normal Shadowing Model
|
\(7\,\mathrm{dB}\) | \(6\,\mathrm{m}\) | \(2\,\mathrm{m}\) | \((15, 140)\,\mathrm{m}\) |
| Home | NIST PAP02-Task 6 Model [visited 2023-10-16T23:08:15Z] | \(0\,\mathrm{dB}\) | - | - | \((5, 45)\,\mathrm{m}\) |
| Office |
For Transmit Power, Transmitter Antenna Gain, and Receiver Antenna Gain, the model offers the following parameter ranges:
| Parameter | Value Range (\((\text{min}, \text{default}, \text{max})\)) |
|---|---|
| Transmit Power | \((-20, 0, 20)\,\mathrm{dBm}\) |
| Transmitter Antenna Gain | \((-10, 0, 10)\,\mathrm{dBi}\) |
| Receiver Antenna Gain | \((-10, 0, 10)\,\mathrm{dBi}\) |