How to Keep Cable Costs Down When Deploying Ultra-wideband RTLS Utilizing PoE Passthrough Devices

By Lubomir Mraz | November 24th, 2020 | 6 min read

• Overview
• Using a PoE Passthrough Device to Reduce Cabling
• Other Use-cases for PoE Passthrough
• PoE Passthrough Device List

It is no secret that the cabling of anchor devices is one of the most significant contributors to RTLS infrastructure costs. Mission-critical applications like production tracking or safety systems require highly accurate positioning data, high availability and very low jitter. To achieve these effectively, cable backhaul is the only option, making Power over Ethernet (PoE) a natural choice for both the power supply and data transfer anchors. If we take a closer look at a breakdown of the costs of installation, it is possible to divide them into the following items (in order of price, highest first):

• Cable placement (tooling, wiring, manpower)
• Port activation and configuration within a switch in a rack
• Design cost
• The cable itself

Since we have designed our anchors to consume very low power (approximately 2.5 W), this means we can use the PoE passthrough feature. This approach is nothing new and has already been in use for quite a while in the Security IP camera industry. It is available on some network switches, where they do not just power the connected devices through PoE but also power themselves via Ethernet. So, you can place a small PoE passthrough device mounted on a DIN rail close to the anchors without the need to use the mains supply. This setup enables you to eliminate a significant portion of the cable, thereby also reducing all related costs. Moreover, with PoE passthrough devices, you can extend the Ethernet 100-metre-distance limitation by double or simplify the use of additional anchors later on without the need for any cable placement from the rack.

In the example below, you can see the difference between having four anchors connected directly to the rack versus four anchors connected through a PoE passthrough. As the illustration shows, if a rack is at a greater distance from the anchors, cable savings might start to become noticeable.

In the next example, the anchors are deployed within a warehouse. Incorporating PoE passthrough devices can help significantly reduce the length of the cables required.

• Extending the Ethernet cable length limit: By employing PoE passthrough, you can double the Ethernet cable length to 200 m using a standard CAT5E cable.

• Daisy-chaining: Some PoE passthrough switches allow you to daisy-chain them, typically to a max of two hops, enabling you to reduce cabling by even more.

• Finally, the PoE passthrough switch enables us to add additional anchors to an already running RTLS. You need to disconnect the cable from an anchor in the area of interest and place new anchor(s) and use PoE passthrough. This allows you to deploy one or more anchors without the need to use a line from the rack.

There are plenty of PoE passthrough devices on the market, but not all of them provide a suitable level of quality for industrial environments. Some of them are unstable, while others might not be able to deliver PoE to all ports. Here is the PoE-recommended passthrough switch that we have tested:

• Planet  IPOE-E174 (recommended, ready to be used out of the box)

Disclaimer: Since Sewio neither produces nor has an established contract with the PoE passthrough vendors, Sewio, therefore, does not take any responsibility for using the listed devices. You are solely responsible for any damage to your network system or loss of data that result from such activities.

As you have seen in this overview of PoE passthrough devices, using them can help you with three common infrastructure challenges: a) reducing cabling costs b) extending the Ethernet range c) expanding an infrastructure that is already in place.