What is the RSS (Received Signal Strength)?

The RSS (Received Signal Strength) sometimes referred as RSSI (Received signal strength indicator) is a measurement of the power present in a received radio signal. The nodes used by the Accuware WiFi Location Monitor and Bluetooth Beacon Tracker are capable of measuring the RSS of nearby Wi-Fi and BLE devices.

The RSS values are measured in dBm and have typical negative values ranging between 0 dBm (excellent signal) and -110 dBm (extremely poor signal). Please keep always in mind that the RSS does NOT decrease linearly as the distance increases and it is affected by many factors, including:

  • the antenna of the device that is transmitting.
  • the antenna of the node itself.
  • the number of walls and other obstructions in proximity of the nodes.
  • the presence of water in proximity of the nodes.
  • the material of the objects inside the environment.
  • the number of people.

Some empirical tests can be done to determine how the RSS varies with the distance from the nodes in a specific environment but it must be kept in mind that the problem of calculating the distance based on RSS is a noisy process by default. On top of that, the error tends to increase with the distance. So it can be relatively easy to determine when a device transmitting is very close to a node (<1m), but as distance increases the estimates become more and more erratic.

In the next paragraphs it is explained how to proceed in order to find the correlation between the RSS and the distance.

How the RSS varies as the distance from a node varies

WiFi Location Monitor

Prerequisites:

  • 1 node.
  • 1 power adapter or 1 battery pack.
  • a set of Accuware credentials (to access the Accuware dashboard, use the API).
  • a Wi-Fi enabled smartphone.
  • a PC/tablet/laptop.

Instructions:

  1. Setup Accuware Wi-Fi Location Monitor as described in this page.
  2. Disconnect and dissociate the smartphone from any other Wi-Fi network that might be used.
  3. Disable the automatic lock-screen and leave the smartphone inside the menu where all the Wi-Fi networks are visible. This is necessary to ensure that the smartphone is actively transmitting Wi-Fi traffic during the whole duration of the test.
  4. Login to the Accuware dashboard.
  5. Add the MAC address of your smartphone among the list of Known devices. This can be done by clicking on Accuware Wi-Fi Location Monitor > Devices as explained in this page.
  6. Ask to one of your colleague to stand still with the smartphone at a specific distance from the node.
  7. Put the following URL in your browser and type ENTER:
    • https://its.accuware.com/api/v1/sites/{siteID}/stations/{mac}/?rss=yes
    • {siteID} is the ID of your site contained in the Accuware Activation email.
    • {mac} is the MAC address of the smartphone that you are using for this test.
  8. Type the Accuware credentials contained in the Accuware Activation email when requested.
  9. The JSON returned will contain the RSS value detected by the node with the smartphone at the chosen distance. Take note of this pair of values (distance and RSS).

By repeating the steps starting from Step 6 you will be able to create a correlation between distances and RSS that will be useful for the analysis that you will do with the data collected by Accuware Wi-Fi Location Monitor.

Bluetooth Beacon Tracker

Prerequisites:

  • 1 node.
  • 1 power adapter or 1 battery pack.
  • a set of Accuware credentials (to access the Accuware dashboard and use the API).
  • a BLE beacon.
  • a PC/tablet/laptop.

Instructions:

  1. Setup Accuware Bluetooth Beacon Tracker as described in this page.
  2. Login to the Accuware dashboard.
  3. Add the MAC address of your BLE beacon among the list of Known devices. This can be done by clicking on Accuware BT Beacon Tracker > Devices as explained in this page.
  4. Ask one of your colleagues to stand still with the BLE beacon at a specific distance from the node.
  5. Put the following URL in your browser and type ENTER:
    • https://its.accuware.com/api/v1/sites/{siteID}/stations/{mac}/?rss=yes
    • {siteID} is the ID of your site contained in the Accuware Activation email.
    • {mac} is the MAC address of the BLE beacon that you are using for this test.
  6. Type the Accuware credentials contained in the Accuware Activation email when requested.
  7. The JSON returned will contain the RSS value detected by the node with the BLE beacon at the chosen distance. Take note of this pair of values (distance and RSS).

By repeating the steps starting from Step 4 you will be able to create a correlation between distances and RSS that will be useful for the analysis that you will do with the data collected by Accuware Bluetooth Beacon Tracker.