Today, every enterprise has Wi-Fi infrastructure in place to enable connectivity and mobility in the environment. It is safe to say Wi-Fi is ubiquitous and is the primary mode of connectivity for mobile phones, laptops, and a multitude of other things. But is using Wi-Fi for connecting all things a good solution? It certainly helps the consumers/end users to have a single connectivity solution to use and manage. But if you are product developer or someone involved in decision making of a connectivity solution for your Internet of Things (IoT) application this might be helpful. In this blog post, I dive into some of things that need to be considered to evaluate the suitability of Wi-Fi for different applications. For this blog purposes, any object that needs network connectivity is treated to be part of IoT. It can be a laptop that has great compute resources or a sensor that merely detects temperature and transmits it. The following factors will help in determining how effective it would be to use Wi-Fi for connectivity.
Scale
When it comes to IoT, scalability is a key requirement that drives much of the technology conversations. How many devices does your application require? We can talk a lot about the theoretical number of simultaneous connections an 802.11a/b/g/n/ac access point (AP) can support but in reality, the number of devices that can have reliable connection simultaneously depends on the throughput requirements which we will be discussed later. A few motion detector sensors, temperature sensors, security cameras and other smart home devices work great on home Wi-Fi but when you scale the numbers into hundreds and thousands in a smart enterprise environment, Wi-Fi may not scale well enough to meet the requirements. As a rule of thumb, you can expect a typical 802.11a/b/n/ac access point to serve tens of client devices with individual throughput requirements of less than 1 Mbps. But capacity analysis and determining how many reliable connections an access point can provide is a much more complicated discussion. Advanced algorithms might have to be implemented to make the client devices turn on/off their radios when necessary so that the number of simultaneous connections at any time is within the Wi-Fi limits. However, things change when you consider 802.11ah (Halow) standard. This Wi-Fi technology operates in sub 1 GHz band and was developed specifically for internet of things to be able to support large number of devices with low throughput requirements. Theoretically each Halow access point can support 8,191 client devices but I haven’t seen products in the market that support more than 250 connections. While this technology has promising features, there are not a lot of products in the market today.
Support for IPv4/IPv6
Devices need to support IPv4/IPv6 to be able to communicate over Wi-Fi. Supporting these protocols might require the client devices to have more compute than they would typically need to perform their intended tasks. Adding support for IP can add more overhead than the actual data making the system inefficient. Support for IP on devices like mobile phones and laptops is a necessity without which they can’t transfer the large amounts of data they are typically designed for. But adding IP support to a motion sensor detector can result in more overhead and less data. The overhead only increases with scale and is a good trade off to having a different connectivity solution to manage. One other thing to consider is IPv4 may not be sufficient at scale and could require IPv6. IPv4 is supported by all enterprises but IPv6 is still in adoption phase. So the support might have to be considered on both client device as well as the consumer networks.
Power
802.11 capable devices tend to have less battery life when compared to 802.15.4 based devices that support protocols like LoRa, ZigBee etc. If client devices can be recharged frequently and has support to continue to operate while charging, using them on Wi-Fi can be great but a lot of connected objects like temperature sensors operate on coin cell batteries. Using the low powered devices that are expected to have longer life (months or years) on Wi-Fi may not be an ideal solution. These devices operate more efficiently on 802.15.4 based protocols.
Throughput
One of the best attributes of Wi-Fi is the throughput capabilities it can offer. This is especially true when compared with other wireless protocols like Bluetooth, ZigBee and LoRa. Wi-Fi offers better throughput at an individual client device level as well as an aggregate level although both the values fall with increased number of connections per AP. Throughput requirements must be evaluated along with scale factor because both are interdependent. Thousands of RFID tags might require few Kbps per tag and an aggregate of few Mbps of throughput but a single inventory management robot that requires higher throughout to continuously scans and transmit data is a better client device to be connected on Wi-Fi.
To be able to determine if Wi-Fi is the right connectivity solution for an IoT application a combination of all these factors also need to be considered. More throughput means more resource utilization which translates to more power consumption which makes the need to have client device be recharged frequently more critical. On the other hand, if the throughput requirements are low, adding an IP support can add enough overhead at scale making the solution impractical. 802.15.4 based connectivity solutions might make more sense in those use cases. There could be a hundred other reasons to choose or not choose Wi-Fi for an IoT application but these four factors are foundational to determining the suitability of the solution.
Wireless Gnan 