When considering an RTLS, not all technologies measure up

When considering an RTLS, particularly in Greenfield deployment, the Total Cost of Ownership hurdle can be difficult to overcome (let alone measure), and when executives are looking for a Return on Investment inside 18 months, making a case for an RTLS deployment of any significance difficult to shift into a “compelling” category. While many of the tangible benefits of an RTLS are well documented, what appears to be less understood (and poorly represented) is how influential the choice of technology has on the TCO & ROI equation, particularly in a like-for-like comparison.

This article elaborates on the technologies and methodologies that sit behind RTLS projects (that have the biggest impact on TCO), contrasts them across similar deployment scenarios, and provides evidence that validates how influential a good decision here will have on the TCO of your planned deployment.

RTLS Vendors will use many different techniques and capabilities to differentiate their solution from everybody else. Some will suggest they have the best accuracy, and some will talk about having the lowest power, and others will even espouse having great support. Few, however, talk around how their proposition delivers the lowest TCO or the shortest ROI. While accuracy or low power are valid considerations, pivoting your RTLS selection around them may negatively impact the up-front investment. Contrary to much of the messaging, this article attempts to illustrate how managing just 3 factors will help to protect the up-front cost of an RTLS deployment, one of the biggest contributors to the TCO equation. These factors are;

The frequency utilised to communicate between the anchor and the tag
The methodology used by the RTLS to determine the location of a tag
The requirement for an anchor to be hard-wired back to a central hub or gateway

**Frequency**

Firstly, let’s consider the frequency used for the wireless communication link that occurs between the anchors and the tags of the RTLS. By itself, this aspect may appear innocuous, but let’s consider briefly that a lower frequency propagates further and penetrates more readily through various building materials (timber, concrete) than higher frequencies. When implemented then, an anchor using a lower frequency can see a tag that is further away, suggesting that fewer anchor points would be required. To illustrate this contrasting nature clearly, the table summarises the various frequencies utilised by the key RTLS technologies.

**Methodology**

The Second factor impacting up-front costs is the methodology utilised in determining a tag’s location within the RTLS environment (as described in the summary below). Multiple methodologies are often combined/augmented to improve the accuracy of an RTLS and are applied in different ways across the various technologies described above. What is not immediately evident is the impact that the methodology may have on the network, and while not explicitly expressed in the summary table, some methodologies (like AoA) generate a lot of data, and others (like TDoA) demand stringent synchronisation across the anchors.

**Anchor Connectivity**

Which leads us to the third factor that influences the TCO, being the methodology for sharing position data of a tag with the system. Ideally, the established wireless network plays this role, and several technologies/methodologies support this. But as eluded above, the mechanism for determining and bringing the position information back to the server simply cannot be accommodated within it. As such, an RTLS based around AoA or TDoA are typically deployed with the anchors hardwired back to the server. The table below summarises the connectivity method for various RTLS deployments in association with the RTLS type.

Other techniques are used to differentiate between vendors (application of maths, topology of network (point-to-point, star, mesh), size of anchor, size of tag, etc.), offering subtle improvements in performance, but in the scheme of things, have little bearing on the TCO. While vendors will go to great lengths to market these differentiators, their campaigns disregard the TCO aspect of selecting an RTLS solution, and don’t warrant elaboration in this article.

Deployment Scenario (1000x200m Floorspace)

From here I’d like to provide a clear illustration how the technology you choose will impact the TCO of an RTLS using a scenario that should be trivial to visualise (and a picture will tell a thousand words!). Picture a large warehouse (100x200m), it is a new build, constructed with materials such as concrete, rebar, Steel Framework, and cladding. It needs to be fitted out with an RTLS that will be used to locate various assets that will be moved in and around the warehouse. Tags will be fitted to tools, fork-lifts, trolleys, scissor lifts, ladders, gas bottles, etc., and when an asset is requested by a worker, picture that person being able to see that asset via a dashboard accessible from a mobile handset and be directed to its current location with an accuracy of about <5 metres.

The scenario described typifies an RTLS deployment and most technologies have the capacity to accommodate it. This exercise will contrast the three leading contenders for this deployment (Bluetooth AoA, UWB, and 6LoWPAN) to illustrate how significant the impact to up-front costs each of them have. When we distil the above factors to differentiating aspects of each of these, a clearer picture around anchor pitch becomes very evident, as depicted in this table. It could be argued that the accuracy of the system could be relaxed by increasing the anchor pitch, and in some cases this is valid. But for technologies like UWB, increasing the distance between anchors to >20m tends to disrupt the interaction of the tag with RTLS system altogether.

Anchor Pitch

This table suggests that the anchor pitch for a Bluetooth AoA deployment is about a 4:1 ratio compared to 6LoWPAN, which at face value is compelling. But pitch alone doesn’t tell the whole story, and when deployed over the width and breadth of a site, this translates into a much higher ratio (more like 6:1). These illustrations below provide an indication of what the anchor density would look like when deployed across the described warehouse.

**Comparing Deployments:** Number of Anchors required; A comparison for various RTLS deployments

Up-front cost to Deploy

One of the stand-out observations from this comparison is the vast number of anchor points required to populate the entire floor space, and how significant the choice of technology has on this outcome. And when you factor in that an RTLS deployment using Bluetooth AoA or UWB requires wired connectivity back to the server, this observation is compounded even further. To illustrate the significance of this further, the graph below depicts how a deployment based around either of these technologies may incur an up-front cost that is >8x higher than a 6LoWPAN deployment.

Technology Choice – Your launching pad for lowering the TCO of your RTLS deployment

With establishing infrastructure being recognised as the biggest cost bucket for any RTLS deployment, it stands to reason to make a measured assessment of the applicable technologies and how each of them could influence the size of this bucket. While this article is not conclusive, it does offer some insights into how influential your technology choice is likely to be, and makes a compelling case for an RTLS based around a 6LoWPAN network using a combination of RSSI and AoA to determine position.

When considering an RTLS, not all technologies measure up

Frequency

Methodology

Anchor Connectivity

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