RT X-LAN drop in communication

Introduction

RT-XLANs units are supplied with RT-Range systems to provide the WLAN connection between the Hunter and Target(s).

In some circumstances, you can experience loss in communication between the Hunter and Target. There are several potential causes of this drop in communication. One of the potential causes is due to noise on the 2.4GHz spectrum. 

This article covers how to identify if this is an issue, and the steps that you can take to address it

What is the issue?

Sometimes communications between the Hunter and Target(s) is lost. This has been witnessed as multiple momentary communication loss cases and even complete communications loss. This communications loss results in a disconnect between the Hunter and Target(s). Often showing as loss of communication and relative data being observed or captured between the Hunter and Target(s) vehicles.

What is the cause of the issue?

Currently most WiFi devices operate on the 2.4 GHz frequency band. Noise is developed in the 2.4 GHz frequency spectrum due to these high traffic levels causing interference. This interference may result in the loss of RT-Range communications between the Hunter and Target vehicle(s). This article covers how to address this loss of RT-Range communications.

How do I identify the issue?

The issue can be identified by a stoppage in updates witnessed through NAVdisplay. For example, the AEB test template in NAVdisplay shows vehicle data from Hunter and Target(s). See the example AEB test template screen capture below.

The issue can be directly identified with use of a spectrum analyzer or similarly with use of the Ubiquity AirView tool.

See the sample spectrum analyzer capture of the background noise levels present in both the 2.4 GHz and 5 GHz frequency bands. 

Note: These readings were taken on the same day and show that there was more noise on the 2.4 GHz frequency band.

Possible Solutions

If you identify that noise on the 2.4 GHz range is an issue, there are some steps that you can take to improve performance.

Changing the Frequency to 5 GHz

The 2nd generation RT-XLANs are able to use both the 2.4 GHz and 5 GHz frequency bands. If one of these bands are very noisy (in this case 2.4 GHz), try using the other band. This is a simple change in the configuration of the 2nd generation RT-XLANs. For instructions on how to access the RT-XLAN configuration via web interface, see this guide.

Note: For optimum 5 GHz performance, use of a 5 GHz specific antenna is required. Contact OxTS sales or your local OxTS Channel Partner. for assistance. Switching to the 5 GHz frequency band may result in reduce range.

The GIF below shows how the frequency can be changed from 2.4 GHz to 5 GHz.

Changing the 2.4 GHz Band Configuration

If changing to the 5 GHz frequency band is not feasible, please follow the configuration steps below for the 2.4 GHz frequency band: 

• Fixing the operating frequency (Central frequency): 
  The default configuration of the 2nd generation RT-XLANs has the central frequency of the Base and Client RT-XLANs set to 'Auto'. With this setting, the Base RT-XLAN will scan the frequencies in the configured band and choose the frequency with the lowest noise to use as it's fixed operating frequency. The Client RT-XLAN will scan through frequencies until it finds the frequency used by the Base RT-XLAN as they must be on the same frequency to communicate. If this auto selection has poor results, this could lead to loss of communications.

Alternatively, it is possible to fix the frequency for the Base RT-XLAN. The Client RT-XLAN can then be fixed to the same frequency.

Note: There have been no reported issues with the 1st generation RT-XLANs as they use a fixed operating frequency by default.

• Channel width: 
  The default RT-XLAN configuration is 20 MHz. Reducing this to 10 MHz will improve the signal-to-noise and make the RT-XLANs less susceptible to noise. However, it does also reduce the bandwidth and thus theoretically reduce the throughput.

Note: all RT-XLANs on the network must be configured to the same channel width to communicate. 

• Wireless mode:
  Test work done by OxTS shows that using the "Access Point PtMP airMAX Mixed" wireless mode improved the communication link stability.

The GIFs below shows how the frequency can be fixed (in this example to 2427 MHz) for the Base and Client. Also, how the channel width is configured from auto to a fixed frequency range.

Note: Special attention must be taken to make sure that the frequency selected is legal in the country that the XLAN will be used.

Changing settings on the Base RT-XLAN.

Changing settings on the Client RT-XLAN

Summary

There isn't one fix all solution to deal with interference since the background noise won't be at the same frequency for all users. Even in one particular location, the background noise can vary between frequencies from one day to the next.

However, these are the steps you can try to improve performance: 

1. Change frequency band. You can use a spectrum analyzer or the Ubiquiti AirView tool to measure the noise of both the 2.4 GHz and the 5 GHz bands to check that swapping to the other band would help. For optimum 5 GHz performance, use of a 5 GHz specific antenna is required. Contact OxTS sales or your local OxTS Rep. for assistance. Switching to the 5 GHz frequency band may result in reduce range.
2. Change the channel width. This may improve signal to noise.
3. Fixing the operating frequency (Central frequency). You may need to use a spectrum analyzer or the Ubuiquity AirView tool to identify the quietest channel. 
4. Change the wireless mode. This may improve the communication link stability.