Reliable wireless networks in mining

Nigel Slater, EVP Business Development, 3D-P

Technology plays a vital role in keeping operations competitive. As mining applications get more and more sophisticated, reliable wireless networks are essential in optimising their benefits and supporting the higher capacity requirements.

LTE (Long Term Evolution) and Wi-Fi technologies have been prevalent in mining for a number of years now, but each have their own limitations, pros, and cons. By using innovative tools and technologies, hybrid networks can enhance connectivity beyond any single technology and eliminate significant limitations. These innovative wireless concepts are becoming a reality and could be the way of the future for mining wireless networks.

The Challenges: Wi-Fi vs LTE, blackspots and highwalls

For many years now, miners have used unlicensed Wi-Fi spectrum to allow connectivity between mining vehicles, applications servers, and operators. The spectrum (2.4GHz and 5GHz) is free and available to anyone who wants to use it, and industrial grade Wi-Fi radio equipment is readily available with plenty of choice in terms of technology and products. The difficulties of these types of mining networks are mainly in interference and network density; that is the number of access points (APs) and supporting infrastructure (such as solar trailers) required to keep mining applications working. In terms of interference, as the Wi-Fi spectrum is unlicensed, there is often a risk that the miner’s network will be interfered with by someone else’s network. This can create ongoing headaches for miners as application performance is degraded due to a suboptimal network caused by interference.

Photo: Peter Turnbull

Also, due to the non-deterministic nature of Wi-Fi (you can’t always tell how the network will perform based on things like noise and client device contention at any given moment) and its relative inability to achieve high data rates over long distances, there is a need to have a highly dense network. That equates to many APs for connectivity to a given number of clients over a given coverage zone. The result is lots of solar trailers that must be maintained and moved regularly. When the government regulator (ACMA) allowed miners and other private businesses access to the LTE spectrum, it offered an alternative to Wi-Fi networks. LTE is licensed and therefore protected from interference. It can also be designed for capacity based on throughput, uplink, downlink, latency, and client density (the number of mining vehicles in a given area, in this case). The higher the network capacity required, the higher the network cost to achieve it. LTE also offers a less dense network in that each LTE AP can provide connectivity to a far greater area and number of client devices than an equivalent Wi-Fi AP. This becomes particularly appealing to miners, as it means less solar trailers to move and maintain. LTE isn’t all good news though - there are a number of downsides. As mining progresses, pits become deeper and dumps become higher, and resulting blackspots appear. With fewer mobile solar trailers available to move and cover the appearing blackspots (relative to Wi-Fi), there is quite often a difficult choice to make over what area you lose coverage in, to then gain it somewhere else. Moving a Cell-On-Wheels (COW), which is a more expensive unit than Wi-Fi trailers, requires more attention and skill due to the intricacies of LTE. Personnel trained and experienced in LTE are also difficult to find, and the technology is significantly more complex than Wi-Fi based technologies.

A Hybrid Solution

One promising solution that overcomes the constraints and issues of both Wi-Fi and LTE technologies is a hybrid network that combines Wi-Fi-based meshing and LTE. Wi-Fi mesh differs from simple Wi-Fi in that all mesh radios can connect to any other mesh radio within line of sight, creating multiple paths of data routing. Here’s an example of how a hybrid network operates. On initial deployment of an LTE network, the equipment is fixed to multiple locations such as towers and other available infrastructure, including COWs or cells-on-wheels. The image below shows the planned LTE coverage over a given area of a mine.

LTE client devices on mining vehicles connect to the LTE base station.

Over time, the dumps grow higher, and the working face continues to move with mining. The coverage provided by the LTE Tower is no longer available in part of the mining area, due to changing terrain which now blocks the link. This is a common occurrence on a mine site.

In a traditional LTE only network, the operator would need to rely on moving a COW.

As mentioned earlier, moving the COW is resource-intensive and can come at the cost of lost coverage in its previously deployed location. Furthermore, under ACMA’s requirements, a license amendment needs to be made each time the COW is relocated. Mine sites with current LTE networks estimate this costs about $5,000 in fees and resource every time a COW is moved – representing significantly more effort and cost than moving a small Wi-Fi trailer.

Hybrid Benefits – getting the best of both worlds

Hybrid, or heterogenous networks offer a number of benefits to miners:

• Filling in LTE coverage holes that are created as mining progresses • Increasing LTE network capacity Enhanced Coverage Our hybrid client device (mounted on a vehicle) that can operate on both LTE and Wi-Fi mesh networks presents two simple, flexible, and efficient ways of dealing with coverage holes.

The image below shows a broken link or coverage black hole to one vehicle in an area of the mine where coverage has degraded over time. Nearby is another vehicle that can connect to the LTE base-station. The hybrid client device with connection to the LTE tower also provides a mesh communications path to the vehicle that, in a traditional LTE only network, would be unable to transmit or receive data.

A second and more powerful way to leverage the hybrid technology is using a small number of mesh network nodes (think Access Points), typically several small highly mobile solar trailers. Enhanced Network Capacity When LTE networks can’t deal with any increase in data, or the number of connected clients, this is called hitting capacity ceiling. This can be very difficult to fix in a traditional LTE network and can occur for many reasons. Firstly, the density of fleet can increase dramatically as mine plans or other externalities occur. Shutting down operations in a pit and moving diggers and auxiliary equipment into another pit can see client density and throughput requirements increase substantially. Additionally, miners often look at enhancing operations by bringing in supporting technologies like additional IP cameras, new applications, etc. A traditional LTE network cannot be altered easily to adapt to these capacity changes. To do so often requires high cost and skills that miners do not have internally. The following images show how simply a hybrid network solution attends to both scenarios. The first shows a small low-cost solar trailer providing in-fill coverage where mine movements have blocked LTE coverage. Data connections are made by Wi-Fi mesh from the vehicles in the LTE blind spot to a mesh solar trailer (orange link) which is then connected via industry standard Cambium Point to Multipoint link (blue link) back to the tower.

The second example is where the magic of some meshing technologies like Rajant Instamesh come to life. In the following image the in-place LTE network is hitting capacity issues that results in an experienced loss of application performance. There is no quick way of either understanding why the applications are not performing or the ability to do anything about it with a traditional LTE network. By using mesh solar trailers, the meshing technology’s ‘cost’ measurement allows the individual client devices to determine the least-cost-route for the transmission of data. If the LTE is reaching capacity the data will automatically be routed to the small supporting Rajant network thus alleviating pressure on the LTE network. Consider it to be a pressure valve for the LTE network.

Each potential link, be it LTE or mesh, is automatically optimised for maximum performance without any manual intervention.

Rather than viewing different network technologies as competing either/or choices, with their individual pros and cons, the time has come to look at combining them in ways that enhance performance and ultimately make the life of our miners simpler. 