By the end of this guide, you will have a basic understanding of the components needed to set up a mesh network, strategies to overcome common roadblocks for long-range, ground networks and the steps required to get the network up and running.

Advanced Ground Robotics Need Advanced Networking Solutions
Advanced Ground Robotics Need Advanced Networking Solutions

Article from | Doodle Labs

Uncrewed ground vehicles (UGVs) can be leveraged to support outdoor industrial,  commercial and public safety endeavors in countless ways, including scanning and  mapping, surveillance and delivery to name just a few. 

But outdoor environments present numerous challenges to maintaining a network on  which these advanced machines rely to connect, transmit data and get their work done. 

This guide will walk you through the process of creating a wireless network that allows  multiple UGVs to communicate with each other and a central control station.  

By the end of this guide, you will have a basic understanding of the components needed  to set up a mesh network, strategies to overcome common roadblocks for long-range,  ground networks and the steps required to get the network up and running.

 

THE PROBLEM WITH ‘TRADITIONAL’  NETWORKING APPROACHES 

Using an existing Wi-Fi network doesn’t always reliably support connectivity. 

Designed for High Throughput over Short Range 

When it comes to setting up an outdoor mesh network for uncrewed ground  vehicles, relying solely on existing Wi-Fi networks can present certain challenges.  Wi-Fi technology is primarily designed for high throughput over short distances,  typically within the range of a few hundred feet. Beyond this range, the  effectiveness of Wi-Fi connectivity diminishes significantly. Even with the latest  enhancements in Wi-Fi standards such as wider bandwidth and higher  modulation schemes like 256-QAM (Quadrature Amplitude Modulation), the  benefits start to decline beyond approximately 50 meters. 

 

Limitations on Improving Connectivity 

Moreover, utilizing more than two antennas in a Wi-Fi setup may not yield  substantial improvements in connectivity. While multiple antennas can enhance  signal reception and transmission in certain scenarios, they have limited  effectiveness when it comes to extending the range of Wi-Fi networks in an  outdoor environment. This limitation poses a significant challenge in achieving  reliable connectivity for UGVs operating at larger distances from the Wi-Fi access points.

 

LTE coverage is not always available. 

Reliant on existing infrastructure 

Another hurdle in establishing an outdoor mesh network for UGVs is the inconsistent  availability of LTE coverage. LTE networks provide wireless communication capabilities over  cellular infrastructure, offering greater coverage compared to Wi-Fi networks. However, the  reach of LTE networks is not ubiquitous, especially in remote or sparsely populated areas.  This limited coverage can be problematic when deploying UGVs in diverse environments,  such as rural or off-grid locations.

 

Higher Latency 

Furthermore, in many LTE deployments, traffic often passes through a cloud server, leading  to higher end-to-end latency. This additional delay in data transmission can impact real-time  communication and control of UGVs, affecting their responsiveness and overall performance.  Depending solely on LTE networks for establishing a robust mesh network may not always  be feasible or optimal due to these coverage limitations and increased latency. 

 

COMMON NETWORKING CHALLENGES 

(And How Doodle Labs Mesh Rider Radios address them) Topology 

Line of Sight 

In general, the best link quality is achieved when there is a line-of-sight (LOS) between  the UGV antennas and the GCS antennas, plus sufficient Fresnel Zone clearance.  Obstructions such as hills and foliage can attenuate or even block the signal entirely. 

Penetration 

Lower frequency RF transmission offers better penetration of foliage and a larger  antenna surface to capture signals, but comes with a larger Fresnel Zone. As a rule of  thumb, with the antennas around shoulder height, we recommend the 2-3 GHz range for  optimal tradeoff between free-space path-loss and fading due to inadequate Fresnel  Zone clearance. 

We recommend starting with a Fresnel Zone calculator to help decide the best  frequency-to-height ratio for your particular use-case. 

 

Application Requirements 

Bandwidth and Latency 

In practical terms, these two parameters determine the usability of your link for your  UGV application. Depending on what you’re using the robot(s) for, the type of data you  need to send will determine your bandwidth, and your tolerance for delays on the link  will determine your max acceptable latency. 

For reference, streaming HD video is approximately 2-3 Mbps, and remotely operating a  vehicle requires latency sub 10 ms. 

 

Urban environments 

Interference 

Urban environments are typically very noisy in terms of RF, especially in the Unlicensed bands. If you’ve ever tried using your phone at a concert or music festival, you’ve  experienced trying to connect over a congested network; the interference on a network  limits range and throughput. 

 

Ground level challenges 

High speed, low to the ground 

When RF signals hit the ground, they bounce and scatter in different directions  depending on the terrain. The constructive and destructive interference between the  multiple signal paths leads to wide variations in received signal strength over just tens of  centimeters, and if the UGV is moving at high speed, it is difficult for the radio’s rate  control algorithms to keep up. 

 

Large networks 

Number of nodes 

Scaling a mesh network up in terms of number of nodes can be one of the most  challenging parts of building a mesh network. 

The amount of background traffic and number of peer-to-peer associations in a single  localized mesh network grows with the square of the number of nodes. If more than 10  nodes are required, advanced configurations are most often required. 

 

Type of traffic 

Building out a large-scale mesh network to support the operation of UGVs and other  team members and/or equipment must naturally allow for the transmission of many  different types of data, which could include HD video, LIDAR, sensor data, command and-control, telemetry and/or any number of other options, all at once. 

Each has different associated throughput requirements and latency tolerances, so  determining a full picture of the traffic that the mesh network needs to pass is among  the most important steps to properly configure it. 

Standard network bandwidth measuring tools such as iperf do not typically take into  account the different types of traffic present in a real deployment. For example,  broadcast transmissions operate very differently from unicast ones. In general, we  recommend limiting broadcasting to very light usage such as periodic service discovery.  If anything more than that is required, then it should be accounted for in the network design. 

 

HOW TO SET UP AN OUTDOOR MESH NETWORK FOR UGVs 

1. Determine System Requirements 

The first and most important step to setting up an outdoor mesh network for UGVs is to  map out your use-case: What is it you’re are trying to achieve with the UGV technology  and what thresholds do your network have to clear in order to achieve it? 

Questions to ask at this stage include: 

- What make up the nodes of your network? Strictly UGVs, or some mix of ground  vehicles, UAVs, other equipment or connected teams of people? 

- What type of data will you need to traffic in your network? 

- What is the maximum allowed latency for each type of data? 

2. Determine Coverage Area 

As a next step, determine the size of area you wish to cover with the mesh network. 

Map out the terrain in your desired coverage area, including natural terrain like hills and  obstacles such as trees or buildings. 

Take special care to identify dead-zones in the coverage area. Consider ease of access  for UGVs – are there trails to get to a destination point? Is there dense terrain? Take  stock of the time it takes to hit every mapped-out location.

A few tools that can be especially useful during this first step: 

• The Elevation tool in ATAK 

• RF performance / Prediction analysis tools like Cloud RF 

• Google Earth. One can’t overvalue this classic source’s accurate estimate height  on map points, and the ability to drop your own pins. 

3. Choose appropriate hardware

Doodle Labs offers the Mesh Rider Radio in multiple form factors relevant to UGV use cases, including OEM, mini-OEM, nano-OEM and the Wearable. 

The OEM form-factor, along with the mini-OEM and nano-OEM, are appropriate for  UGVs that call for a fully-embedded datalink solution. The mini-OEM and nano-OEM are  best fit for platforms that call for radios with a small footprint. 

If you’re in need of a rugged, fixed installation and/or one mounted on a vehicle, the  Wearable form-factor is the best choice. It is fully enclosed. 

On the controller side, you can go with the Wearable or any of the OEM options,  depending upon your choice of controller model. 

Mesh Rider is available in many frequency options: unlicensed - 900Mhz, 2.4GHz,  5.8GHz, and licensed 1.3GHz, 2.2GHz etc. We can cover many scenarios – including NLOS  where foliage and/or building penetration are required. 

4. Plan network layout

Antenna alignment and height play a crucial role in the success of a mesh network for  UGVs. It is important to position the antennas in a way that maximizes line-of-sight  between the UGV and other network nodes. This can be achieved by placing the  antennas at a sufficient height, such as on masts or elevated platforms. Additionally,  careful alignment of the antennas should be done to minimize interference and signal  degradation. 

Cable considerations are also important, here. High-quality cables with proper shielding  should be used to minimize signal loss and maintain signal integrity over longer  distances. It is crucial to select cables of appropriate length to ensure efficient network  connectivity without excessive cable runs that can introduce signal attenuation. 

Antenna gain is a significant factor in determining the coverage range and signal  strength of the network. Higher gain antennas can transmit and receive signals over  longer distances and are particularly useful in situations where the UGV may operate at  extended ranges from the control station or other nodes. However, it's important to  strike a balance between gain and beam width to ensure both long-range coverage and  sufficient coverage in the immediate vicinity of the UGV. 

5. Configure nodes 

Mesh Rider Radios are designed to effectively bridge all devices that are connected on  their ethernet interface. 

Similar to an ethernet switch in an office, into which any computer is plugged and will be  on the same LAN and they’ll be able to talk directly one another, so long as they are on  the same IP sub-net, Mesh Rider radios essentially extend a LAN over the entire mesh, so  any device that’s plugged into the internet ports on the devices will be on the same LAN.  No configuration is required, other than a simple change to username and password.

6. Test the network 

Since you planned the network layout in step four and know what type of network traffic  you’ll be sending, you need to check the network to see how much margin you have and  measure how real-world performance compares to expected outcomes. 

A useful tool in Mesh Rider to assist in this process is the “Link status log.” 

The Link Status Log utility is designed to log the each radio's link status over time. It  keeps very detailed logs on the performance of each node. Aside from downloading the  logs, you can also get the latest status from any particular node. 

7. Integrate with Control Station Software 

You’re likely to want to integrate your control station software directly to the nodes in  your network.  

Control Station Software can make use of Mesh Rider Radio’s API to talk to the radio and  get status information from the radio including things like signal strength, network load  and any warning signs. 

8. Deploy UGVs 

You’ve successfully planned and configured an outdoor mesh network for UGVs – now it’s  time to deploy. 

Get your robots out in the field, watch the nodes on the dynamic mesh network establish  and maintain connectivity and observe real-time data payload transfer. 

9. Scale the network 

The beauty of a true mesh network is that the initial deployment of UGVs is just the start – you can build on the foundation you’ve designed to develop larger, scaled deployments  with additional nodes and cover even more ground. 

The only limitation is your imagination.

 

The content & opinions in this article are the author’s and do not necessarily represent the views of RoboticsTomorrow

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