Understanding BLE Range
Understand the range of your DM Dots and DM Gateways, and what can affect it
Written by Cameron Everett
Updated at May 1st, 2026
Table of Contents
Overview
The advertised range of a Bluetooth Low Energy (BLE) device is rarely the range you will see in the real world. The numbers advertised by many companies are measured in ideal lab conditions: open air, line-of-sight, perfectly aligned antennas, and no other 2.4 GHz traffic in the area. In the real world, once a Dot (or any BLE Tag) is fitted to an asset and a gateway (such as the Hawk) is mounted in a vehicle or on a wall, several factors combine to determine the effective range you will get in deployment.
This article explains how to estimate BLE range for the Dot family and DM BLE gateways, and walks through the main physical factors that affect it. If you are new to the Dots, see Getting Started with the DM Dots first.
Estimating Range with the Bluetooth Range Estimator
The Bluetooth SIG provides an online tool that lets you model the expected range based on the radio parameters of the transmitter and receiver:
How to use the Range Estimtor with the Dots and DM BLE Gateways
When using the estimator to model a Dot talking to a DM BLE gateway (such as the Hawk), use the following inputs on both the transmitter and receiver side:
- PHY: LE 1M — The Dots and DM gateways operate on the standard 1 Mbps PHY. Do not select LE 2M (shorter range) or LE Coded (longer range, but not used by the Dots).
- TX Power: 7 dBm (max) — This is the maximum transmit power supported by the Dots. Many configurations will run lower than this in practice to preserve battery, so 7 dBm represents a best-case scenario.
- Antenna Gain (Tx): 0 dBi
- Antenna Gain (Rx): 0 dBi
The Dot family and DM gateways use small integrated antennas with effectively unity gain. Plugging in higher gain figures will produce optimistic numbers that will not match real-world results.
The estimator gives you a useful upper bound on what is physically possible. Real installations almost always come in below this figure because of the factors described below.
How TX Power Affects RSSI
RSSI (Received Signal Strength Indicator) is the power level the receiver sees, measured in dBm. It is a direct function of transmit power minus path loss:
RSSI ≈ TX Power − Path Loss − Obstruction Losses ± Antenna Effects
A few practical implications:
- Increasing TX power by 3 dB roughly doubles the transmitted energy, but it does not double the range. In free space, doubling the range adds about 6 dB of path loss, so a 3 dB power bump only buys you roughly 40% more distance.
- Dropping TX power from 7 dBm to 0 dBm (an 7 dB reduction) will typically cut effective range by more than half and shows up as a corresponding 7 dBm drop in RSSI at any given distance.
- RSSI values below roughly −95 dBm on LE 1M start to approach the receiver sensitivity floor. Beyond this point, packet loss climbs quickly even though the device may still appear "in range."
- RSSI fluctuates several dB second-to-second even when nothing is moving, because of multipath interference and small environmental changes. Do not treat a single reading as a definitive distance measurement.
Higher TX power also draws more current from the battery on every advertisement, so range and battery life are a direct trade-off. See the DM Dots - Battery Life Estimator for a model of how TX power and advertising rate affect expected lifetime.
If you are seeing weaker RSSI than expected, the first thing to check is whether the Dot's TX power has been configured below maximum, or whether something is physically attenuating the signal.
Antenna Orientation
Practical guidance:
- Where possible, mount the Dot and the gateway so their long axes are roughly parallel.
- Avoid mounting Dots directly against large metal surfaces. If unavoidable, expect reduced range on the metal-facing side.
- A Dot lying flat on a horizontal surface will generally have its strongest radiation pattern in a "doughnut" around the device, with weaker performance directly above and below it.
Because asset orientation in the field is often unpredictable, real deployments see RSSI swing by 10 dB or more simply from the asset rotating relative to the gateway.
Density: Many BLE Tags in Close Proximity
BLE advertising happens on three channels (37, 38, 39) in the 2.4 GHz band. When you have many Dots in a small area — a yard full of tagged trailers, a warehouse of tagged tools, a depot of containers — they all share the same three channels. This causes a few effects:
- Advertising collisions. Two Dots that happen to advertise on the same channel at the same instant will collide; the gateway hears noise instead of either packet. Advertising slots include a small random offset to reduce this, but as the number of devices grows, the probability of overlap rises.
- Noise. Dense BLE activity increases channel occupancy and RF interference. The result is that weaker packets are less likely to be decoded cleanly, especially near the edge of range.
- Gateway processing limits. A gateway scanning for advertisements has a finite amount of time per channel. With hundreds of tags in range, the gateway may simply not get to every advertisement before it expires from its internal buffer. See DM Dot Family - Integration for details on how DM gateways scan and report tag data.
- 2.4 GHz interference from other sources. Wi-Fi, microwave ovens, other BLE devices, and Zigbee networks share the band. A busy depot environment will generally have more 2.4 GHz noise than open countryside.
Effective range shrinks in dense environments, even though nothing about the individual radios has changed. For example, a Dot that comfortably reaches 50 metres in an empty field may only be reliably seen at 15–20 metres in a yard with hundreds of other tags advertising.
If you are deploying into a dense environment, consider:
- Lowering the advertising rate, where battery life and detection latency allow, reducing transmissions per device and therefore collisions.
- Using more gateways with overlapping coverage rather than extending a single gateway's range.
Other Environmental Factors
A few additional things commonly degrade real-world range:
- The human body. The body is mostly water, which strongly absorbs 2.4 GHz energy. A person standing between a Dot and a gateway can drop the signal by 10–15 dB.
- Liquids and dense materials. Tagging an asset that contains liquid (a fuel tank, a drum) will significantly attenuate signal on the liquid-facing side.
- Walls, floors, and vehicle bodies. Each layer of construction material adds path loss. Concrete, brick, and metal-clad walls have particularly strong effects. Vehicle bodywork is essentially a Faraday cage — a Dot inside a sealed metal trailer will be difficult to detect from outside.
Putting It All Together
The Bluetooth Range Estimator gives you a useful theoretical range with the LE 1M / 7 dBm / 0 dBi settings noted above. From that figure, expect to lose budget for:
- Antenna orientation and mounting
- Body, liquid, or metal in the path
- Density and ambient 2.4 GHz noise (microwaves, industrial equipment and more)
- TX power configured below 8 dBm (1:1 dB-for-dB reduction in RSSI)
When troubleshooting a range problem, the structured approach is:
- Confirm the Dot's TX power is set to maximum.
- Check antenna orientation and what the Dot is mounted against.
- Consider what is physically between the Dot and the gateway.
- Consider how many other BLE devices are advertising in the area.
- Re-run the range estimator with realistic assumptions to set expectations.
Device placement, orientation and environmental effects may make a far bigger difference to real-world performance than any setting on the device itself.
