Recieved Signal Strenght Indicator (RSSI) with obstacles

In summary, a smartphone's RSSI meter can sense when a person is in the way of a wireless signal. The field surrounding the person will be distorted, and there will be more signal points with a +3dB boost. The signal from the transmitter will also be affected, causing a flutter in the reading.
  • #1
Quinten
2
0
Hi there,

I'm trying to design a positioning system that makes use of RSSI.
When a wireless signal would propagate through a human body, the signal strength would be weaker than when it wouldn't have to overcome any obstacles. My question is: would this difference in signal strength be measurable? (Keep in mind, the sensor that measures the RSSI is a smartphone, so sensitivity is limited)
If anybody has any information on the subject I would really appreciate it! ;)
 
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  • #2
Welcome to PF.
The human body contains so much salt water that a smartphone signal will not easily pass all the way through it. The presence of a body moving nearby will distort the signal received by the phone. The field will tend to move in multiple paths around the body. Sometimes there will be +3dB more signal, other-times there will be deep nulls with much less, probably –30dB. That is more than sufficient to sense using RSSI.
 
  • #3
So it is possible that the signal strenght doubles? If it would be -3dB it would be perfect...
Is the +3dB the result of superposition of several waves passing around the body? (If so, would it occur a lot? Or is it more an exception?)
 
  • #4
Yes, all the significant effects are due to the constructive and destructive interference pattern created by the multiple paths around the moving body. The body dimensions are less than 60 wavelengths, so the body will be in the near field of the receive antenna.

There will be a few signal points with more than +3dB. The deep nulls will occur where two similar amplitude signals via different paths cancel due to opposite phase.

You will see very little effect from signals passing through the body.

There is also the problem of the transmitters field. Any change in the illumination due to changes in the propagation path to the body will produce local variation. Aircraft, motor vehicles or other people nearby will give the RSSI a fluttering level. That flutter may easily have amplitude variations greater than 3dB.
 
  • #5


Hi there,

Yes, it is possible to measure the difference in signal strength with obstacles using RSSI. RSSI is a measurement of the received power level of a wireless signal and can be affected by various factors including obstacles. However, it is important to keep in mind that the sensitivity of the sensor, in this case a smartphone, may limit the accuracy of the measurements. Factors such as the type and thickness of the obstacles, distance between the wireless signal source and the sensor, and the frequency of the signal can also affect the RSSI measurements. It would be beneficial to conduct experiments and gather data to determine the accuracy and limitations of using RSSI for positioning with obstacles. Additionally, there may be other technologies or techniques that can be used in conjunction with RSSI to improve the accuracy of the positioning system. I recommend further research and experimentation in this area to fully understand the capabilities and limitations of using RSSI in your positioning system.
 

1. What is RSSI and how is it measured?

RSSI stands for Received Signal Strength Indicator and is a measure of the power level of a received signal. It is usually measured in units of decibels (dB) and can be obtained by using a wireless device, such as a smartphone, or through specialized equipment.

2. How does RSSI change with obstacles present?

RSSI can be affected by a variety of factors, including the presence of obstacles between the transmitter and receiver. In general, obstacles can cause a decrease in RSSI due to signal attenuation. This means that the signal loses power as it travels through the obstacle, resulting in a lower RSSI value.

3. What types of obstacles can affect RSSI?

Obstacles that can affect RSSI include physical objects such as walls, trees, or buildings, as well as environmental conditions like weather or interference from other electronic devices.

4. How can RSSI be used to estimate signal quality?

RSSI can be used as an indicator of signal quality, with higher RSSI values generally indicating a stronger and more reliable signal. However, it is important to note that RSSI is not the only factor that affects signal quality, and other factors such as interference and noise should also be considered.

5. Is RSSI a reliable measure of signal strength?

While RSSI can provide a general indication of signal strength, it is not always a completely accurate measure. Factors such as multipath interference, which occurs when a signal is reflected off of multiple surfaces before reaching the receiver, can affect RSSI readings. Additionally, different wireless devices may have varying ways of measuring and reporting RSSI, making comparisons between devices difficult.

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