There are many potential reasons to why you may experience range issues between sensors/meters and a gateway in your property. It can feel a bit like a jungle and sometimes multiple factors can contribute to a certain result. In this first article on the subject, you will learn more about the potential reasons to why you’re experiencing range issues, as well as potential solutions to solve the issue. In the future, we will deep-dive further into the many aspects of range issues mentioned in this article. Stay tuned!
Physical obstacles
Any obstacle between sensors/meters and gateways plays a huge role in how much radio signals are affected. Examples of obstacles can be everything from walls, furniture, fireproof doors or gates, to the type of material a building is made of.
For example, a building made from concrete affects the radio signal more negatively compared to a more light-weight material, such as wood. Furthermore, buildings with reinforcing bars also affect the radio signal negatively.
Even windows can affect radio signals. In recent years, a film is often applied on the outside of windows to prevent radiance; However, this film makes it harder to retrieve or transmit signals to and from a building.
Floorplan and layout
The design and layout of a building can also cause issues. In a high-rise building it is quite easy to achieve a good signal from all your sensors and meters to the gateway, since gateways are mostly installed in basements or roofs. In this scenario one simply needs to ensure that the sensors/meters are installed horizontally to get maximum range.
However, if a building is shaped like a U or an L, it is not as trivial to tell where to install sensors/meters to get the necessary range to a gateway. In some cases, one gateway might not even be enough to cover the whole building. In this scenario, it is advantageous to use Lansen's repeaters to extend the range between sensors/meters and the gateway.
Another reason for lack of coverage can be if the building has too many floors between a sensor/meter and the gateway. In these cases, it may be required to adapt your metering solution to the building in question. Again, one easy solution is to install one, or more, Lansen repeater in the part of the building where one is experiencing range issues.
Case: Improving range by removing units from physical obstacles
Sometimes, the reason for poor range can be less obvious than the material of the building or the floorplan. On one occasion, a customer experienced problems during evenings with a Lansen repeater installed on a lamp post near an apartment-building. During the day everything worked as intended, but when the evening came, the signal suddenly weakened. After some investigation it turned out that the radio signal from the meters/sensors inside the building was weakened when the residents parked their cars outside the building, which sometimes prevented the signal from coming through. The solution was simply to move the repeater to a lamp post one step closer to the building itself.
This is a good example on how range can be affected by many different types of circumstances, which one might not think of at a first glance when troubleshooting an issue.
Wired vs wireless
Before proceeding onto potential reasons to why your wireless solution may experience range issues, we quickly want to touch on wired meters/sensors. In many buildings there are preinstalled wires to communicate with meters/sensors throughout a building from a gateway.
However, if you ever want to add more sensors/meters onto the existing infrastructure solution, there is a risk that there are no wired connections where the meters/sensors are to be mounted. Wired infrastructure works as long as everything is thought out, and no additions are going to be made in the future. However, if one needs to change the infrastructure in a building to add more meters or sensors, one has two options in case wires are not available at the location of the meters/sensors:
While wired meters/sensors provides an easy solution and typically doesn’t have range issues, it comes at the expense of not being flexible or adaptable in case one wants to add more sensors.
Low vs high frequencies
So, what factors affect range of wireless solutions on a technical level? One big factor is frequency where one has to decide between a lower or higher frequency. From a range perspective, lower frequency is always better because the radio signal can penetrate through material better. However, a higher frequency gives the possibility to make the devices themselves smaller, since the antenna can be made smaller compared to a device using a lower frequency. Higher frequency can sometimes also give a longer battery time.
Low vs high bitrate
Another factor that should be taken into consideration is bitrate. Bitrate is the amount of data that can be transferred to one unit to another during a certain amount of time. A lower, and thereby slower, bitrate enables the frequency bands to be closer to one another in typical FSK modulation. A higher bitrate on the other hand, gives faster shifts between the frequency bands, which means that the frequency bands needs to be further apart from each other. Therefore, the lower bitrate gives better range since the gateway can listen to the shifts between the frequency bands better compared to a higher bitrate.
So why not just use the lowest possible bitrate?
Well, the downside of a lower bitrate is that is takes longer time to transmit data. For battery operated devices, longer transmission times require more power which in the end results in a shorter battery lifetime. So from this perspective, a higher bitrate is better to achieve a longer battery lifetime. You can still compensate the shorter battery life by sending data less often. However, this might not be desirable in many systems where data is required as often as possible.
Therefore, one has to take all these factors into consideration and choose a frequency and bitrate that gives the best compensated result between having good range and sufficiently quick send interval to have good battery lifetime. Everything depends on the situation and needs.
Radiated power and design of antennas
Another big factor for range is the radiated power of a device. Typically, the more energy that is radiated from the antennas, the longer the range will be. It’s worth knowing that different frequencies are bound by law on an upper limit on how much power a device can transmit with. For example, for frequencies at 868 MHz, typically used by wM-Bus or mioty, the upper limit is 25 mW (~14 dBm) while Wi-Fi at 2.5 GHz is bound by 100 mW. However, limitations on the hardware such as antenna design typically lowers the true radiated power from a device.
Many manufacturers only state the radiated power internally on the device, which is 25 mW in the case of 868 MHz, but has a considerably lower effective radiated power (ERP). Therefore, it is of great importance to look for the ERP of a device to better know what range can be expected from a device.
Disturbances
Another big contributing factor of poor radio signals are disturbances such as the following:
A way to avoid these types of disturbances is to use some kind of filtering amplifier, such as Lansen's filtered amplifier. This device is mounted on a receiver, such as a gateway, to filter out unwanted signals and amplify the desired radio signal.
Worth mentioning is that our long range repeaters are fitted with components that amplifies the desired radio signal and filters out disturbances, thus making it suitable for heavy-duty areas.
Radio technology
Lastly, the type of radio technology you use will of course affect the range and collection of data. Which radio technology that is best suited for you depends on several factors, such as your desired range, how often data is needed, the level of resilience in a system, I.e., how many telegrams from a device is acceptable to lose, and how scalable your solution needs to be. There are several radio technologies one can choose from, such as:
We offer both wireless M-Bus and mioty. For more information on our technologies, click here.
Electrical outlets and polarization
The number one factor to have in mind here is where electrical outlets are placed, as well as where you have outlets for wired communication. For wireless solutions it is important to think about how and where you can place meters/sensors in relation to the gateway to prevent polarization issues. Antennas should always be aiming towards one another for the signal to be received correctly. For example, if you have an antenna that sends out data horizontally you want to have a gateway that receives the data horizontally.
On many of our sensors we have antennas on both the side and the bottom to reduce any potential polarization issues. Thanks to this, the sensor is more flexible to use in different solutions since it can send out data both vertically and horizontally.
There are of course both advantages and disadvantages to having one or two antennas. Two antennas give a larger circular range, however you may lose some signal strength. One antenna gives a more limited range, but it has a greater signal strength in the direction it is aiming towards. In this case it is therefore important to make sure that the receiver or sensor is in the right direction in relation to the unit.
Example: Optimize your placements for the best range
Let’s imagine you have a three-floor apartment building you want to collect data from. You place a gateway at the roof. To get full coverage of the whole building, you need to install repeaters. Let’s say that you install one repeater on the middle floor to cover all meters/sensors.
Now, let's say you want to collect data from three buildings in the same area. Going with the option above, one would need to install one repeater and one gateway in each building, which is expensive.
Instead, you can install one repeater in each building and a single gateway on the roof on one of the buildings. And then add a repeater outside, for example on a lamp post or mast. In this way, repeaters from two buildings will be be forwarded to the gateway located in the third building via the repeater mounted outside. This is a much more cost-effective approach while also dramatically increasing the range between repeaters and gateway.
Lastly, the placements of the meters and sensors themselves can also be a reason to why a signal can’t be retrieved. There are many examples of this, such as:
Please note that all illustrations are simplified examples that are meant to visualize the concept or use of product.
All factors mentioned in this article will affect how strong the signal to the gateway will be. As mentioned, potential reasons to range issues can be anything from the layout of a building, which radio technology you choose, to the placement of a sensor itself. We hope that this has shed som light on the subject, and hopefully contributed with insights regarding how to optimize range in your smart metering system.
If you are interested in any of our solutions presented in this article, don't hesitate to reach out to our sales team, or take a closer look at our assortment.