When it comes to getting your smart device to do the smart things you intended it to do, there’s typically three “big” choices developers consider for their IoT communication solutions. Meaning — what kind of connectivity is doing the talking for your device.
The Big Three – Wi-Fi, Bluetooth, and Cellular – are what most people (and most of our clients at Brash) think of first. In the last six months alone, we’ve started several new smart device projects, and each client has asked us to help evaluate which of the Big Three makes the most sense. While there is a myriad of other options that could be considered (like Sigfox, LoRa, Sub-GHz, ultra-wideband, mesh networks, and more recently, satellite communications), we don’t see as much uptake on these technologies except in more specific use cases.
With the Big Three, we’re often asked which is the best option by clients. This seemingly innocuous question is rather loaded. The engineer in me, ever afraid of being imprecise, always wants to answer with something not very helpful like, “it depends.”
In choosing between the Big Three, we work with a client to understand what “best” means for them. This requires us to understand a wide variety of things like, end-user and product requirements; the client’s budget and timeline; the depth and strength of their internal technical team; the business model surrounding the project; any technical nuances specific to the application; the environment in which the product needs to operate; regulatory or safety concerns; and so forth. Know that we spend a lot of time and effort understanding the client and their needs before answering this question definitively.
But since “it depends” doesn’t help our readers out, I’ve put together a list of general qualifiers to consider when making this decision without a precise engineer asking you a zillion questions to gain a general understanding on the pros/cons of the Big Three.
USER EXPERIENCE
If you want reviews for your devices that sound like, “Hey, I turned it on, and it just worked,” then cellular connectivity is probably your best chance of getting there since it requires no intervention or input from the user of the device. This will offer your end-users the easiest and most seamless experience (barring issues due to connectivity and roaming, particularly when using global SIM solutions). There’s no pairing process like Bluetooth where you may have to enter a code seen on another device’s screen, or the nuisance of having to correctly input a complicated Wi-Fi network name and password.
And while many might argue that they’ve had no issues with Wi-Fi credential setup or BLE pairing with their devices, I know I’ve done my fair share of long-distance troubleshooting with my parents who live 800 miles away for exactly this reason. If you have end-users that are similar to my parents — not the most tech savvy — then don’t discount the nuisance and support challenges that BLE pairing, and Wi-Fi credential setup can create. This nuisance can be further compounded if the setup application doesn’t provide the user with guiding information. Have you ever sat around for 5 minutes watching the spinner continuously run, while the app tells you that it’s “Connecting…” and then it suddenly asks you to restart the process when it couldn’t connect? And then you have to enter the 12-digit serial number AGAIN?!?
We’ve had clients that insisted using Wi-Fi wouldn’t be an issue, but they quickly changed their minds when it came time for a test run of the device in their target user’s business environment and moved over to cellular. Connecting to your home Wi-Fi and running a smart thermometer is a very different experience over connecting to networks you don’t control like in any enterprise environment. Many Wi-Fi networks in business enterprises integrate firewalls, filters, or other safety mechanisms that limit new or previously unauthorized devices from joining the network, making it cumbersome to introduce Wi-Fi-based smart devices on the fly and easily in such networks. This is yet another win for cellular technology since it bypasses the need to negotiate access on existing networks.
RANGE
Wouldn’t it be great if your smart gadget works pretty much anywhere? Imagine a smart device working whether the user has their phone around or not, and whether they are in range of their home’s Wi-Fi network. With cellular connectivity, your smart device can be on the move and continue to send data to a central server. With Wi-Fi, and Bluetooth, your smart device is far more limited in terms of when and where it can reliably send data or trigger important notifications. So, in terms of range of use, cellular tends to have the bigger appeal for devices that are highly mobile and transmit data wherever they are.
Wi-Fi makes sense to use with a device that remains fixed in a spot where you’re bound to have reliable internet connection. A smart device with a Wi-Fi connection can communicate back and forth with a central server, and this is the mechanism that allows a phone (or website) to interact with the device from far away.
The range of a Bluetooth Low Energy (BLE) smart device is far less than that of a cellular- or Wi-Fi-based smart device. Moreover, Bluetooth relies on physical proximity between devices to communicate, and generally, doesn’t provide a direct method for connecting to a central server through the internet. With a BLE smart device, an internet-connected phone or a hub in proximity of the device, is required to communicate data from the BLE device to a central server. As a result, using a BLE-based smart remote to trigger an action on another device far away is harder because you always need a phone or hub to act as the intermediary between the BLE device and the remote device.
COST
Cost is generally one of the largest factors in choosing between the Big Three after we’ve considered any user experience-related requirements. There are different kinds of costs to consider:
· the cost per part
· the cost to develop
· the cost to the customer
· the potential for recurring costs
· the cost of not getting it right,
· or the cost of getting to market too slowly.
Even just answering which is the lowest cost option in terms of materials, parts, etc. needed to manufacture the product isn’t a straightforward answer for a precise engineer like myself.
Wi-fi or BLE modules are typically cheaper than a cellular module, but keep in mind that there’s so much variance among manufacturers and part types that the cheapest LTE-M cellular module might be a bit less expensive than a higher-end Wi-Fi 6 module.
Furthermore, while Wi-Fi hardware may be cheaper than cellular hardware, the best cost optimization can be achieved with Bluetooth hardware. Then, there’s also the question of software support. If we can save on software development time by using a part that’s well supported by a manufacturer — but slightly more expensive than an alternative — then the math and choice gets a lot tougher.
With cellular communication, you also have to factor in the recurring costs for data usage. Who’s paying for the monthly bill from the cell phone company for the data that the smart device uses? For this reason, cellular connectivity is often better used for smart devices that are amenable to the Holy Grail, a recurring revenue business model (RRBM). If your product supports a RRBM, then it’s way easier to justify the monthly cell phone bills that you as the manufacturer must pay in the background as each of your smart devices transmit data to a server.
You probably started salivating when I said RRBM, but don’t get too excited. Arguably, most people don’t want to pay a monthly fee for getting data from a smart thermostat or smart water bottle. However, a restaurant owner who needs immediate notification of a freezer malfunction that can cost a lot of money, is more likely to pay monthly for a freezer monitoring system. It’s important to keep in mind that the overall value must be justified to the end-user, and when it isn’t, cellular connectivity may not be a good choice.
SECURITY
In terms security, Bluetooth is widely regarded as one of the worst options, in large part due to the fact that many device developers are simply unaware of how to build secure connections with this protocol.
Related to security issues, is the business of pairing Bluetooth devices. To the average user, this simply means the process of connecting a Bluetooth device to their mobile phone. However, pairing is also an element of the Bluetooth protocol which can be managed in several ways (e.g., with a passcode or without). Without getting too much into the details around pairing, it’s important to be aware that trying to implement a more secure pairing method has some implications on the user interface and product complexity. For example, passcode pairing —as many users may be familiar with when connecting their phone to their vehicle — requires one device to display a passcode, and the other to take the passcode input. In other words, an additional, dedicated input or display element in the user interface may be needed to enable a more secure pairing process.
When it comes to security, Wi-Fi is also a less desirable option. In addition to end-users knowingly using very easy to guess passwords, Wi-Fi connections are generally more hackable, especially when the designers of the devices, whether by choice or ignorance, don’t enable the appropriate protection mechanisms. Cellular connectivity is still considered to be far more secure that Wi-Fi or Bluetooth connectivity, and that’s mainly because the baseline authentication and encryption mechanisms that provide the secure communication are always enabled by default. With Wi-Fi and Bluetooth, a designer or engineer has to be far more aware and proactive about enabling/integrating appropriate authentication and encryption mechanisms.
POWER CONSUMPTION
Wi-Fi and cellular connectivity are both power hungry in comparison to a Bluetooth connectivity. As such, Wi-Fi and cellular connectivity may not be well suited to battery-powered smart devices in applications requiring a continuous connection. And the difference can be quite significant in that a battery that lasts weeks with a Bluetooth-enabled device may only last a few hours in Wi-Fi- or cellular-enabled device.
Needing to remember to charge or replace batteries may not be suitable for a device that needs minimal maintenance from the user like an access card reader, or smart door locks. Accordingly low-power, battery-powered smart devices often use BLE, or Bluetooth technology. While Bluetooth-enabled devices can operate longer on a battery, they aren’t capable of transmitting large amounts of data quickly. Applications like real-time video streaming don’t work well for Bluetooth because of Bluetooth’s inherent bandwidth limitation. As such, Bluetooth is best used for applications where the device transmits a smaller amount of data, is battery-powered device, and needs to last a long time before a battery charge or replacement.
The precise engineer in me wants to once again remind our readers that choosing between the Big Three (or another communication tech option) is never simple. But this is a great jumping off point for anyone looking to start building their own IoT or smart device. A great partner who has been through the process goes a long way to help navigate the development landscape, and you can always reach out to our team at letsgo@brashinc.com at any point in your product development journey. We’re also good at math and can help you determine the best cost solution that might seem a bit daunting while balancing your user experience and product vision. It’s what we do.
It’s not just a product, it’s our passion.
Be brash.