Cellular vs WiFi for IoT: Choosing the Best Connectivity Option

Eseye

IoT Hardware and Connectivity Specialists

LinkedIn

The real value delivered by IoT applications is in the data provided by the end-point devices. Or more specifically, in the analysis of that data and how it can be used to positively influence business decisions.

To unlock this value, data needs to be transferred from the end-point device to some compute resource, possibly on the network edge, but more likely in a centralized cloud or data center. And transferring this data requires connectivity.

Along with the almost infinite number of use cases for IoT applications, the choices for connectivity are diverse. NB-IoT, LoRa, Sigfox, WiFi, GPS, and then of course cellular, including 3G, 4G, and both public and private 5G, to name a handful of options.

Choosing the best connectivity option for your IoT application can be challenging and depends a lot on the specific use case as well as engineering costs and resources.

In this article we will specifically explore the potential for both cellular and WiFi connectivity, the benefits of each option in specific circumstances, and when it makes sense to double down and use both.

Comparing cellular and WiFi connectivity

Connectivity technologies are in a constant state of innovation. Just look at how successive generations of cellular networks, from the earliest 1G analog networks of the 1980s, through four generations of digital technology, have delivered throughput and latency that now competes with fixed line.

As these advancements have been made, IoT applications have moved from a LAN (Local Area Network) to a WAN (Wide Area Network) environment, creating even more demand for lower latency, higher performance connectivity.

It is this LAN versus WAN deployment that is a key consideration when assessing WiFi and cellular connectivity. Does the IoT device need to be able to communicate with the centralized controller or ‘brain’ directly? Or can your network of IoT devices communicate through some edge device or gateway that collates the data and passes it back to the central controller, acting as a local proxy? 

Cost

Cost is a significant factor in the comparison of WiFi versus cellular and it starts at the design and engineering level.

Where WiFi and cellular radio chipsets and antennas take up similar amounts of real estate in the device (WiFi antennas may be slightly smaller), WiFi is generally accepted to operate in the 2.4GHz and 5GHz bands globally, meaning one universal antenna in a device that can be used anywhere in the world. Different types of cellular network on the other hand will require a specific antenna depending on whether you opt for 3G, 4G, or 5G, as well as regional differences in terms of frequency adoption.

This could mean a device designed for Europe would not be usable in the Americas, and would bump the engineering cost up when designing cellular-based IoT devices.

Another consideration is that every cellular-based device will require certification by the local operator(s), which also carries a cost as well as a time-to-market consideration.

Furthermore, once deployed, cellular data plans are generally more expensive than comparable WiFi plans. So if the application is likely to generate large amounts of data to be transferred on a regular basis, WiFi could work out cheaper when compared to cellular.

Taking all this into account however, cellular does offer considerable benefits.

Range and coverage

One of the key benefits cellular delivers over WiFi is range and coverage. GSM (2G and 3G) and LTE (4G and 5G) can provide connectivity between an IoT device and a cell tower or base station at ranges up to 10km, getting the data directly onto the internet.

WiFi on the other hand requires some kind of router or gateway to connect to devices up to 50m away. Then the router or gateway also needs its own connectivity, which could be provided by any wireless or fixed line technology, to backhaul the data onto the internet.

Cellular is ideal for a wide variety of applications, especially in more remote or complex environments where connectivity infrastructure is non-existent or would be difficult to install, like sensors for a remote environment, for example.

Cellular is also a good choice for moving IoT devices because of its range.

That said, although cellular networks today cover around 98% of populated areas, they’re a long way short of territory coverage, which is often closer to 60%. Because a population is not equally divided across a territory, 3G/4G coverage by geography falls some 30% below population coverage statistics, resulting in mobile ‘not spots’. So it’s possible that some of those remote applications are too remote. This is especially true of IoT devices that must have access to a consistent, secure, and reliable connection always.

For applications that might be very deep underground, a cellular signal might not reach and it may make more sense to set up a local WiFi network and connect that into the rest of your infrastructure via a gateway. Cellular radio penetration can be surprisingly effective however.

Mobility

As we have already discussed, cellular was designed with mobility in mind and is therefore well suited for applications where the IoT device is mobile, such as inventory or asset tracking. Examples include cattle, construction equipment, or containers.

If the IoT device has support for multiple frequencies, it could also provide mobility on an international level through roaming. Again, equipment or shipping containers would be a good use case, and multi-IMSI SIMs and eSIM’s with eUICC network switching innovations help avoid restrictions around permanent roaming.

WiFi offers fewer benefits in terms of mobility as the IoT devices will require additional infrastructure such as routers, gateways, or repeaters, that would all need to be pre-configured.

That said, WiFi is ideal for stationary devices in a fixed location, such as vending machines, or devices that only move within a specific environment, such as equipment in a warehouse, for example.

Bandwidth

4G and 5G cellular or WiFi connections are both preferred options for applications that require real-time streaming or substantial data throughput, such as security cameras or monitoring devices.

High-bandwidth options such as 5G are especially well-suited for real-time applications with low-latency requirements, especially when rapid transmission of large data volumes is involved, such as medical robotics used in surgery.

WiFi also delivers high data rates, but it can be slower compared to LTE in some scenarios, especially if the local network is congested. There is also more infrastructure involved, with a higher chance of misconfiguration or failure.

To this end, cellular is likely to provide more advantageous bandwidth geographically, when compared with many commercially available network options that are required to backhaul WiFi.

Ultimately, data bandwidth values are highly subjective and dependent on the use-case, local environment, and different generations of technology. But both WiFi and LTE 4G, 5G and beyond are capable of delivering performance in excess of 1Gbps.

Data rate & power consumption

Power consumption and battery life are the biggest trade-offs when it comes to higher data rates and smaller form factors.

Higher speed cellular options such as 4G/5G LTE have higher power requirements and require more uptime for cell switching, shortening the lifespan of a device’s battery. WiFi is often more efficient for when battery life is a concern, since it draws less power.

The application is also a consideration. The smaller the form factor of the device, the smaller the battery.

For very small form factor devices, or those where maximum battery life is a concern, other low-power connectivity options, like Low Power Wide Area Network (LPWAN) technologies (LTE-M, LoRa, NB-IoT), may be more suitable.

Connection reliability and redundancy

Cellular connections such as GSM or LTE are dependent on network infrastructure owned and operated by geographically local mobile network operators. As these networks are designed for the mass-market, high-availability is baked in, making cellular a good option in terms of reliability, redundancy, and security.

IoT devices will also connect to the nearest cell tower directly, unlike WiFi, which requires routers, gateways, or access points for network availability within a more restricted radius.

As a result, WiFi tends to be less reliable, especially in the event of scenarios like a local power outage, which could shut down the WiFi network, taking the IoT devices offline, whereas cellular benefits from overlapping coverage provided by different operators and more resilient infrastructure.

Security

Cellular networks (3G, 4G, and 5G) provide strong encryption and subscriber authentication mechanisms, making them suitable for applications requiring high levels of security.

Mobile network operator infrastructure is a reliable trust point, indeed many governments consider national mobile networks to be ‘critical infrastructure’, and part of this recognition sits with the specialist security skills the operators maintain.

WiFi security is less resilient by default, although it can be improved through encryption protocols and password protection, but requires additional overheads in terms of resources and management. WiFi also requires that the organization trusts whoever deployed the infrastructure, or they must secure it themselves at potentially great expense.

In this regard, cellular is attractive because the network operator already employs more experts than any organization could likely justify.

Another consideration in terms of the way WiFi creates a local area network, is how vulnerable WiFi-based IoT devices could be a jumping off point granting a hacker access to other entities on the same network.

This again feeds in to the benefit of having access to security skills and know-how to ensure misconfigurations are minimized and best practices followed.

Scalability

Because cellular, especially the LTE flavors, was designed for broad coverage and wide-scale installations, it is especially well suited to IoT networks with a large number of devices.

WiFi on the other hand is well suited for smaller-scale deployments within a defined boundary, or in particularly complex applications where cellular infrastructure is not available, such as very rural locations, underground (mining) or offshore deployments like oil rigs.

Understanding Cellular Connectivity for IoT

Cellular IoT connectivity transmits data packets over-the-air through wireless spectrum to mobile network operator’s cell towers, where it travels onward to the internet. They typically use licensed spectrum, adhere to open, global industry standards, and are operated by wireless network providers.

For Eseye customers, data flows from cell towers to one of our points of presence (PoPs) through our high-speed Multiprotocol Label Switching (MPLS) network. It then goes over the internet to the customer’s network for processing and storage.

Advantages and limitations of cellular IoT connectivity

As we have investigated above, the advantages of cellular IoT connectivity are many.

• Its inherently wide-scale design makes it particularly well suited to large and/or geographically diverse deployments
• Multi SIM and network support makes it well suited for mobile and international applications as well as providing redundancy of connection
• It is highly scalable
• It offers increased security
• It offers high bandwidth connectivity and low latency in some options
• It’s very reliable and the infrastructure is managed by the network operators themselves

But it does have its limitations:

• Cellular generally works out to be more expensive than WiFi in terms of upfront and ongoing costs
• Although well suited for international connectivity, not every device will work in every location unless you have access to multiple networks
• Higher data rates and more frequent network polling can put a strain on the battery
• Some environments could discount cellular completely. It might still be possible to deploy a private cellular network, but these have their own challenges
• Operators are shutting down older cellular networks and sunsetting 2G and 3G to reuse the spectrum for modern technologies. This will make some existing deployments obsolete. 

Example use cases for cellular IoT

The use cases for cellular IoT connectivity are many, including agriculture and farming – both for tracking cattle and equipment; consumer tech, such as smart wearables and connected cars; smart city infrastructure like EV charge points, traffic lights and parking meters; smart vending machines; hospital and healthcare equipment; and tracking construction equipment; and emergency services, such as pop-up temporary networks.

WiFi Connectivity for IoT

WiFi connectivity for IoT transmits data packets over-the-air through unlicensed wireless spectrum that is generally adopted on a universal level (2.4GHz and 5GHz in most cases). The IoT endpoint device connects to a WiFi router or gateway, that in turn is either directly connected to the internet on a different connection type, or backhauls the data on to another router.

The WiFi infrastructure is deployed and managed, and remains the responsibility of the application owner.

Advantages and limitations of WiFi IoT connectivity

As we have investigated above, the advantages of WiFi IoT connectivity are:

• Cheaper to deploy and to operate than cellular
• Well-suited to local environments, where cellular is not present or where a reliable presence of cellular cannot be established.
• Devices will generally work anywhere in the world, as long as they are pre-configured to the local area network, making devices cheaper and widely reusable
• Reasonable data rates (but not as good as cellular)
• Low power consumption

And WiFi does have its limitations:

• Better suited to fixed deployment, or limited mobility within a defined boundary
• Lower security
• Difficult to scale
• Infrastructure deployment and management overheads
• Lower reliability
• No redundancy without adding additional connection types

How to choose the right connectivity for your IoT project

In summary, there are four key considerations when deciding on the best IoT connectivity for your device.

1. Device design: What is the required form factor and the resulting impact in terms of real estate for radio chips and antennas, as well as battery footprint? Will the device be stationary or mobile? What will be the scale of the deployment?
2. Environmental factors: Where the application is deployed could make the decision about connectivity for you. Is a cellular network even an option? If the IoT devices are mobile will they require international connectivity? If WiFi is the preferred option, do you have the resources and capital to build and manage the infrastructure?
3. Data transmission: What data volumes and transmission frequency does your application require? What are your data security and data sovereignty requirements? Does the application require real-time connectivity, or low latency connections, or is batch processing sufficient? What about reliability and redundancy?
4. Power constraints: Again, the application may make the decision for you. Form factor will be a significant factor in terms of battery size. While data transmission will also influence what kind of demands are put on the battery. The environment could also be a factor, depending on how accessible the devices are in terms of being able to do a battery swap, or whether the IoT device is intended to be in-situ and inaccessible for years at a time.

Why choose? Using both Cellular and WiFi

Depending on the above considerations – if the device form factor allows and the application demands – multi connectivity is also an option.

Known as Multi-RAT (multi-Radio Access Type), these connectivity solutions give IoT devices freedom to choose which radio type they connect to, improving both the capabilities and the reliability of the device.

Demand for multi-RAT connectivity is increasing, especially as it’s getting more economically feasible to have multiple radios in a single device. You can now get to sub-$1 pricing for a WiFi Bluetooth chip, for example.

For example, drinks manufacturer Costa Coffee makes use of a router that can handle multiple radio-access types including 3G, 4G/LTE and Wi-Fi connections in its Costa Express vending machines.

Being able to mix cellular and WiFi connectivity can meet unique requirements for the device and application, making it much more resilient to changing connectivity environments and future-proofing the IoT initiative and estate.

Eseye

IoT Hardware and Connectivity Specialists

LinkedIn

Eseye brings decades of end-to-end expertise to integrate and optimise IoT connectivity delivering near 100% uptime. From idea to implementation and beyond, we deliver lasting value from IoT. Nobody does IoT better.

In this article

• Comparing cellular and WiFi connectivity
• Understanding Cellular Connectivity for IoT
• WiFi Connectivity for IoT
• Choosing the right connectivity
• Using both Cellular and WiFi