Letting your sensor platform go while keeping it close

It’s the span that matters

So what is a distributed sensing platform? Basically, as in any distributed system, its a coalition of nodes/devices working together towards a common goal, only now it’s towards a mutual sensing capability such as thermally mapping an object/area, surveillance, presence, theft detection or basically any task that involves multiple, independent sensor units working together to provide a broad yet high-resolution view over a certain area.

Deployment schema of a Smart-Road sensing platform mapping highway traffic to a single vehicle resolution

So why distribute?

In recent years, distributed platforms are becoming more and more common as technology evolves and communication, computing power and energy advance rapidly allowing deployments of decentralizing systems towards scalable, redundant and highly available platforms. Examples range from storage systems, communication platforms and even currency (blockchain). Thus distributed sensing platforms are inevitable to become more and more common in coming years. Amongst the advantages of such system are:

  • Span — the ability to uniformly cover large and varying areas/terrains
  • Scalability — by nature, these systems are built to scale and could seamlessly scale as much as needed
  • Robustness — no single point of failure, allowing for significantly more robust systems
  • Redundancy — even in case of a node momentary failure, other nodes act to “cover” for him and keep the correctness and availability of the system
  • Accuracy —Overcoming the induced dependence of accuracy on the distance from the sensor in centralized systems (e.g. a cameras sensitivity drops as you move further away) thus increasing overall accuracy and resolution
  • Cost — while deploying hundreds of units intuitively sounds a costly solution, often the “loosening” of requirements per node (as 100% per-node availability is not needed) allows for much cheaper solutions, especially with the decreasing costs of IoT hardware in recent years
  • New dimensions — reach insights and data granularity often unobservable otherwise, and on that note do read Avi Tel-or’s article IoT — Paradigm Shift in Traffic Monitoring on the how and why now

Breaking it down, it comes out to 3 main challenges:

  1. Physically installing the system
  2. Initializing it (both individually and as a whole)
  3. Remote (and on premise) maintenance

1. Installation Flow

A critical and often overlooked flow is the physical installation of the sensors, even more so when installing a few hundreds of them per day.

2. Initializing a distributed sensory system in a harsh, hard to reach environment

Let us, for the sake of the example, imagine we wish to install 1500 temperature and pressure sensors along an oil pipeline laid across some section of ocean. Naturally, we would like to know where each sensor is along the pipe (so we know where the potential issue is), and we would also like to make sure it knows its own location (because it configures its communication params, its sensing needs or plenty of other reasons)

3.1. But what if we mis-configured them?

Nevertheless, apparently, sensors 3,4 and 5 were configured to a wrong channel, we now need a way to remotely access them, re-configure and send them back out. What could presumably seem like an easy task with a distributed internet based system, becomes a challenge when your sensory platform is radio based, without access and partially asynchronous.

  • Monitoring device health metrics — having devices periodically transmit back their health metrics such as battery state, charging, operation mode and any other relevant metric. This should actually be a must-have feature in any such platform.
  • Two-way communication — while having the sensors transmit their readings is naturally a must (as it’s their job), having the ability to transmit back to them certain pre-defined parameters configuring anything from their working state to specific thresholds is also a key and useful feature.
  • Configuration management utils — both to monitor devices current configuration as well as load and update all or certain sub-sets of sensors for different tasks and operational modes.
  • Watch-dogs — a programmatic mechanism for detecting and overcoming software or hardware bugs. You better have a whole pack of those to save you from unfortunately inevitable situations.
  • Firmware-update Over the Air — see next clause for more details, but definitely don’t underestimate its importance.

3.2. Firmware-update Over The Air (FoTA)

What might seem as a trivial feature in many applications today, is a crucial and tricky feature in distributed radio-based systems where accessibility is an issue but so is bandwidth and synchrony. Nevertheless, maintaining the ability to remotely upgrade and upload new images to the sensors is a must and could not only allow the ability to upgrade the system but also save you when finding (inevitable) bugs in the software.

3.3. A Maintenance State of Mind

When all fails remotely, often one would need to physically access the sensor and check/repair it. While in some system maintenance ops can be done on premies, in those hard, harsh environments often the trivial yet very effective method of swapping the unit with a new one and testing/refurbishing the old unit in the shop is the right path to go with.

  • A mechanical design allowing for easy swapping of devices. So adhering the sensor to the ceiling with epoxy is probably not a very good approach.
  • A software protocol for easy replacement of sensors, initializing the new sensor with the correct parameters.

A True Story About a Smart Road Platform

At Valerann, we developed a smart road platform with a proprietary and unique data source embedded in the asphalt and installed across and about highways, generating a live and stable traffic map to a single vehicle level regardless of weather, visibility and traffic conditions.

The Valerann Smart Road-Sensing platform

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