Subscribe

Subscribers to the boundless digital magazine will receive a regular digest of the most recently posted content.


WLAN Design for Internet of Things is All in the Prep

By Neil McRae in · Experts · August 7, 2015
Designing a WLAN for IoT? Design stage one, site survey
 
In my last post, Designing a WLAN for IoT? Define your requirements first, I summarised the importance of business/technical requirements capture to validate a project.
 
How many times have you heard these saying, “The more you prepare for something, the better it will go? Or more famously a quote from Benjamin Franklin “If you fail to plan, you are planning to fail!” So why am I quoting famous people? You will find I do this a lot. Well simple, this is a mind-set that needs to be cemented into today’s WLAN professionals. If we focus on the successes of the past, both at the business level, and personal level, we will all learn how to “plan for success” and maybe organisational amnesia wouldn’t be able to gain a foothold.
 
As you may have realised, when preforming any type of task it is imperative to do a great deal of preparation, many dependencies necessitate advanced planning and coordination. In Step 1 we defined the requirements and collated them into the CRD, so from these requirements we need to prepare a scope of works (SOW) document. The SOW is an official document that is agreed between the designer and the project stakeholders. It will detail project deliverables, project schedules, and project scope. The SOW should be well written with clearly defined objectives for both the project stakeholders and the designer to complete. Before we can consider performing any type of survey you will need to create your own SOW document, Aerohive Networks have produced an example SOW document that can be used to capture this information (Click Here). 
 
Once the scope document is completed we can start to plan for the actual survey. There are several types of surveys that can be conducted, each suited to certain environments. People have a certain preference to one-method verses another. The truth is, what you gain or lose from one type to the other is not always evident.
Here are a few different methods for site surveys:
·       Desktop survey
o   Simulated/Predictive – The Wi-Fi characteristics are predicted for the virtual environment model (walls and other obstructions) created by the surveyor and computer software simulates coverage based on the inputs
·       Onsite survey
o   Passive - the surveyor collects comprehensive data on the RF environment (signal strength, noise level, interference, etc)
o   Active – the surveyor connects to the wireless network and generates network traffic to measure actual throughput rates, ping times etc
o   Hybrid (Active/Passive) – Built into some applications to allow the surveyor to measure both active and passive data simultaneously
You will find many sources that detail each of these methods and I would encourage you to spend time researching these. My recommendation would be to read The Certified Wireless Design Professional (CWDP) book which is part of the Certified Wireless Network Professionals (CWNP) series that covers this topic in detail”)
 
One of the questions I get asked a lot (that I am frequently asked) when I’m out with customers is “Does an on-site survey need to be conducted when designing a network based on capacity?” My answer is always the same yes, no, maybe! It depends on the environment and the complexity of the project. This is a very contentious topic that is frequently debated amongst WLAN professionals. My advice would be to perform a desktop survey with inputs from someone who has knowledge of the building structures and where possible get someone to take some measurements (active/passive data) in some of the areas of concern (or just to validate your prediction). At this point you can then perform a post site survey (which we will cover in a later blog) to validate that the network is operating as expected. As I have mentioned previously, one of the most under respected stages of the design phase is design validation and optimisation based on the collected results. It is at this point where a detailed RF assessment is completed, signal quality is checked and any problem areas are defined. 

In my last post, Designing a WLAN for IoT? Define your requirements first, I summarised the importance of business/technical requirements capture to validate a project. In this article, I discuss preparation and scope of works (SOW).

How many times have you heard these saying, “The more you prepare for something, the better it will go? Or more famously a quote from Benjamin Franklin, “If you fail to plan, you are planning to fail!” So why am I quoting famous people? You will find I do this a lot. Well simple, this is a mind-set that needs to be cemented into today’s WLAN professionals. If we focus on the successes of the past, both at the business level, and personal level, we will all learn how to “plan for success” and maybe organisational amnesia wouldn’t be able to gain a foothold.

As you may have realised, when preforming any type of task it is imperative to do a great deal of preparation. Many dependencies necessitate advanced planning and coordination. At the heart of any Internet of Things deployment is a wireless LAN (WLAN), and in Step 1 of this article series on designing a WLAN for IoT, we defined the requirements and collated them into the CRD. So from these requirements we need to prepare an SOW document.

The SOW is an official document that is agreed between the designer and the project stakeholders. It will detail project deliverables, project schedules, and project scope. The SOW should be well written with clearly defined objectives for both the project stakeholders and the designer to complete.

Before we can consider performing any type of survey you will need to create your own SOW document.

Once the scope document is completed we can start to plan for the actual survey. There are several types of surveys that can be conducted, each suited to certain environments. People have a certain preference to one-method verses another. The truth is, what you gain or lose from one type to the other is not always  evident.

Here are a few different methods for site surveys:

Desktop survey

  • Simulated/Predictive – The Wi-Fi characteristics are predicted for the virtual environment model (walls and other obstructions) created by the surveyor and computer software simulates coverage based on the inputs

Onsite survey

  • Passive - the surveyor collects comprehensive data on the RF environment (signal strength, noise level, interference, etc)
  • Active – the surveyor connects to the wireless network and generates network traffic to measure actual throughput rates, ping times etc
  • Hybrid (Active/Passive) – Built into some applications to allow the surveyor to measure both active and passive data simultaneously

You will find many sources that detail each of these methods and I would encourage you to spend time researching these. My recommendation would be to read The Certified Wireless Design Professional (CWDP) book which is part of the Certified Wireless Network Professionals (CWNP) series that covers this topic in detail. 

One of the questions I get asked a lot (that I am frequently asked) is, “Does an on-site survey need to be conducted when designing a network based on capacity?” My answer is always the same: "yes, no, maybe!” It depends on the environment and the complexity of the project.

This is a very contentious topic that is frequently debated amongst WLAN professionals. My advice would be to perform a desktop survey with inputs from someone who has knowledge of the building structures - and where possible get someone to take some measurements (active/passive data) in some of the areas of concern (or just to validate your prediction). At this point you can then perform a post site survey (which we will cover in a later article) to validate that the network is operating as expected.

As I have mentioned previously, one of the most under respected stages of the design phase is design validation and optimisation based on the collected results. It is at this point where a detailed RF assessment is completed, signal quality is checked and any problem areas are defined.

Neil McRae (@neilos1985)

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.

Subscribe

Subscribers to the boundless digital magazine will receive a regular digest of the most recently posted content.