Designing a Wi-Fi Network for the Internet of Things? Think Capacity

In my last post, WLAN Design For IoT Is All In The Prep, I summarized the importance of preparation and scope of works for a project. In this article, I discuss the importance of designing the WLAN for capacity.

Vint Cerf, one of the founding fathers of the internet, once said, “There’s nothing special about wireless networks except that wireless capacity is sometimes less than what you can get, for example, from optical fiber.” While part of this quote holds true still to this day, I don’t think Vint Cerf realized approximately 21 billion devices are predicted to be connected via IoT by 2020!

With all this in mind, when designing a wireless network, the key is adopting the right approach. Today’s networks must deal with the proliferation of all mobile devices and other IoT devices, even while continuing to supporting the normal business applications and use cases of old.

In the past, many wireless networks had been designed to provide basic connectivity for casual internet browsing and other low bandwidth applications within a defined service area. This coverage-based design model has previously worked in providing basic wireless access. However, a different approach is required to support the explosion of IoT.

So what am I telling you? In essence we need to start thinking about, and accommodating for, the current, and also anticipated, capacity.  We also need to think about performance levels you require rather than just focusing on providing basic coverage (unless this is all that is required).

So why do we need to change the approach? When using a coverage-based design model, we are only taking into consideration one metric, signal strength, to define acceptable user experience which has demonstrated to be a poor indicator of network success. A coverage-based design in most cases will not take into consideration many critical variables required to meet both capacity and performance needs, such as:

  • Reducing (where possible) co-channel interference
  • Meeting bandwidth, latency, and jitter requirements of specific applications
  • Understanding device capabilities and quantities
  • Load balancing between APs/radios (based on airtime/load)
  • Providing spectral capacity
  • Provide QoS end-to-end 

Is there a better approach to take?

A better approach is to take a capacity-based design approach which takes into account high-capacity planning and design. It is also important to use networking equipment that is high performance and has smart features built in to assist in optimizing the RF (Tip: Dual 5GHz radios can help).

Only through the use of good requirements gathering, network design, configuration, and optimisation can wireless networks meet the demands of dense user and device populations.

As we have seen in one of my previous blogs, by using the process of capturing business and technical requirements, we can identify network design objectives and design the network accordingly to provide the desired performance levels. The key to getting this right is understanding the following:

  • The client devices being used on the network
  • The capabilities of these devices (A great source of device capabilities here)
  • Client device density per coverage area
  • Applications required per device

I now understand my device capabilities, what comes next?

Network design involves a mixture of identifying requirements into a network architecture that meets the capacity and performance requirements. This would need to be backed up by understanding and adopting design principles for capacity-based design over the traditional coverage-based design method. 

This process will allow you to determine access points required and radio capacity needed to support the total client and application requirement, as previously defined. Additionally, it is recommended to follow Wi-Fi best practices of selecting the right placement for the access points, antennas, and other required accessories for optimal coverage and importantly performance.

As I have discussed previously, Wi-Fi surveys and WLAN preparation is key to preparation; once you have completed a survey it will translate into the network configuration. Once the network has been configured as required there is always a need to optimize and adapt to changes –  a network management platform can assist in providing these type of statistics and metrics.

Next in the series we will look into WLAN configuration. This is an important stage in defining how the WLAN network should be configured. This next post will detail configurations for security, QoS, application control, rate limiting, radio setting, SSID settings, and so on. Stay tuned.

All posts in this series:

Designing a Wi-Fi Network for the Internet of Things? Think Capacity

WLAN Configuration For Internet Of Things

What Does A Solution Design For Internet Of Things Look Like?

Neil is a Systems Engineer at Aerohive and has an extensive background in wireless technology, including performing site surveys, complex planning, RF design, installations, and troubleshooting with multi vendor products.

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