A buyer’s guide to wireless in a warehouse
Achieving good wireless network coverage in a warehouse can seem like a daunting task. How do I go about filling such a large space with enough Wi-Fi coverage to avoid black spots? What do I need to know? What problems might I encounter?
This buyers guide provides you with some thoughts and considerations to allow you make a more informed decision when purchasing a wireless network solution for your warehouse. Knowing the basics will help you achieve your aims and get the best value for money.
Besides the more obvious variables, such as the size of the warehouse and the number of users, there are more underlying complex issues to consider when implementing Wi-Fi in such a large working area.
To Survey or not to Survey?
Is your warehouse already occupied and full of stock?
An active wireless survey, with live access points (APs), is always preferable as it provides a realistic picture of the expected wireless foot print. However, if your warehouse is not built and populated then an active survey can be of little value, (although, it will be worth having an empty warehouse tested for possible Wi-Fi interference). Both wireless frequency bands in use today are unlicensed and therefore all sorts of devices can use the same frequencies, and interfere with the Wi-Fi signal as a result. For example, tri-state alarm sensors, door openers and other sensors
Predictive surveys and wireless solutions can be based on plans but they should be carried out by an experienced engineer who understands exactly what you are looking to achieve.
It is important to have a post-deployment active survey to confirm the solution works as expected.
What’s on the Racks?
When you consider the ever-changing nature of the inventory in a warehouse, the challenge really starts to become clear. Stock will affect signal strength and different materials cause different reflections and levels of attenuation. For example, a specific rack may be storing paper, but the next day it may be a car engine. Metal and paper will have different effects on the wireless signal.
A traditional wireless access point (AP) with an internal antenna, will provide network coverage in a 360 degree, omnidirectional ‘donut’ around the Access Point. This sort of coverage works fine in an office environment, but is often not ideal in a warehouse. This is due to the typically linear layout of racking. By utilizing directional antennas at the ends of the bays, you can increase network performance and reduce signal losses caused by the stock. Imagine an omni-directional antenna being a bit like a lightbulb on a cord. It provides light in a circle around it and the further you move away, the dimmer it gets. A directional antenna is more like a torch beam, shinning a narrow beam of light in a particular direction but able to push the light much further.
The most effective solution is to place an AP at the end of each lane, on alternating ends. As the client moves to the far end of the lane their wireless device should connect to the alternate lane’s AP. Again, post implementation checks can ensure this is working.
When broadcasting Wi-Fi to every corner of a space, adjacent AP’s signal will overlap. This sounds simple enough but overlapping signal can cause interference and problems. A controller-based deployment will deal with this. A deployment plan will avoid interference and signal clashes or you can design the solution to give adjacent AP’s non-overlapping channels to provide the most efficient use of the airspace. Clever use of these channels will enable you to create a Wi-Fi map that avoids frequency clashes.
Access point failure can be an issue and, remembering that most access points in warehouses are often high up and fairly inaccessible, it is worth considering overlapping access points to cover failed hardware in critical areas.
This may sound complicated, but the plan overlap is something that Lynx Networks can provide for you.
It’s likely that wireless devices will be in used at every level of the racking. It almost goes without saying that the solution should cover all three dimensions of the entire working area. This dictates the antenna types and the locations.
A well designed Wi-Fi map will always employ power level adjustments in order to create comprehensive coverage. It is wise to plan a wireless network with access points NOT set to full power. That way you have options for areas that are difficult to reach. By adjusting the power output of each AP, a network engineer can increase or decrease its signal reach.
Power output is designed at the planning stage, but it is likely that power levels will need to be adjusted after the network is up and running to ensure the best possible results.
You can spend all the time in the world creating a great coverage plan for your APs, but if the right physical network infrastructure is not there to support it then you will still experience slow wireless throughput.
Due to the number of devices contending for the bandwidth in a warehouse, it is recommended that you have at least a 1GB link to each AP. The latest wireless standard 802.11ac wave 2 supports data rates of well over 1GB, therefore connectivity to the wired network should be 1GB as a minimum. Imagine creating more lanes on a busy motorway, the cars will get to their destination much faster.
Cat 6a cabling is preferable because it allows for 10Gb links in the future and, due to better heat dispersion, for the latest power over Ethernet (PoE) applications. Many 802.11ac access points require the higher PoE standard (802.3at) to support full power output. Most will work with standard PoE (802.3af) but will have a reduced power output as a consequence.
Another consideration for access points that are mounted 15 meters up or higher might be to consider running a cable up to the console port as well as the network port. This will give admin access in case of problems.
Finally, you should remember that appropriate switching architecture is also critical as mentioned above. 10Gb links back to the core will give much better bandwidth and minimize bottlenecks. Additional edge switches may be required to provide the additional ports for the access points with the right amount of PoE budget. Some switches will not provide full power PoE out of all ports at the same time. Therefore, a switch populated by more than 50% of access points or other full power PoE devices such as CCTV will need to be checked for its maximum power budget.
Lynx Networks Can Help
Though this article outlines some of the key things to consider when implementing a wireless network in a warehouse, it only goes into the basics. It is important that you consult with expert network engineers to get the best possible results and ensure your business can perform its day to day operations. To see how we can help you or to arrange a site survey please contact us.
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