Bluetooth is a low power, short-range wireless communication standard. In more technical terms, Bluetooth operates in the 2400 to 2483.5 MHz range within the ISM 2.4 GHz frequency band, which is available without license in much of the world. Unlike the sub-GHz bands, and because this band has similar regulations everywhere, it has proved to be much more popular for many consumer devices (and is also used for most Wi-Fi connections). Data is split into packets and exchanged via one of 79 designated Bluetooth channels—each of which have one MHz in bandwidth. It was originally designed for continuous data streaming applications that exchange data at a close range. Thus, it is used for applications like wireless speakers, headsets, keyboards, and more.
But there is one glaring problem that has quite a few implications for Bluetooth-based smart sensor networks—and that issue is range performance.
In other words, it can be very challenging for a distributed network using such a low-power system. The way around this issue is to form a mesh, where a network of nodes are all communicating with one another and relaying data. However, with mesh Bluetooth networks comes a barrage of potential issues, which manifest in a number of ways.
Within this article, we’ll walk through those implications and highlight a few scenarios where Bluetooth-based smart sensor networks work well (and when they do not). Bear in mind that these implications are based on the idea that you may build a mesh network to solve Bluetooth range issues.
Implications Of Range Performance Issues
- Battery life: When nodes are in a mesh, each node has to act as both a sensor and a repeater. It must constantly listen for, relay, and route network traffic. Thus, you’ll likely experience decreased battery life.
- Reliability: If one node in a key location drops out of your mesh, it could take down a good chunk of the network.
- Cost: Bluetooth is relatively inexpensive, but this cost will vary drastically depending on network coverage in a mesh. Covering a small home, for example, may not be too expensive—but covering a large office building will be. Part of that is because you have to add repeater nodes where they aren’t necessarily needed just to ensure that your network reaches to the furthest points.
- Latency: To get a message from point A to point B in a mesh network, the data will have to travel through points C, D, E, F, and G first. Thus, to get a message where it needs to go, you could introduce a few seconds of latency.
Scenarios Where Bluetooth-Based Smart Sensor Networks Work Well
Isolated Sensor Networks
An example of an isolated sensor network may be a small house (where you’re not talking extreme ranges). You could probably cover the furthest reaches with only a few nodes—or you may be able to cover the area with a centrally located access point and avoid using nodes at all. Short-range remotes that control televisions, radios, gaming systems, or smart home lighting are examples of good Bluetooth-based networks.
Nearly all new vehicles (and many older vehicles) are Bluetooth-enabled, offering you the chance to listen to music on your phone or talk through car speakers. Vehicles offer a perfect Bluetooth environment, because they are self-contained and all devices are close to each other.
Scenarios Where Bluetooth-Based Smart Sensor Networks Do Not Work Well
If you’re considering integrating a Bluetooth-based smart sensor network at a college campus, you might want to think about a different sensor technology. Not only will the range be difficult to tackle, but you’ll be trying to work in a congested band with interference problems. This is where reliability can become a major issue. If someone microwaves one too many Hot Pockets, the microwaves could interfere with the radio and take out a chunk of your mesh network—causing a huge headache.
Dynamic Or Mobile Networks
If you’re trying to plan a Bluetooth network that deals with constant movement or a dynamic radio frequency (RF) environment, you’re in for a challenge. Determining how to ensure that your nodes can talk to your gateway adequately is challenging enough, but it is even more difficult if part of your network is mobile.
There’s a fair amount of technology out there to implement wireless sensor networks, and they all have strengths and weaknesses. You need to consider your particular application and business model and use those elements to help you determine the best fit. And if you run into any questions, feel free to contact us—we’re happy to help.