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LAUNCHXL-CC13-90: transmission power adjustment calculation

Zhiyong Li (FT)
Expert 2920 points
Part Number: LAUNCHXL-CC13-90
Other Parts Discussed in Thread: CC1190, CC1310

Hi,

Not sure if the title conveys my question. Here is what I am trying to accomplish:

We have two radios (A & B) installed at two fixed locations. When the transmission power of radio A is set at 26dBm, the RSSI measured by the receiving radio (B) is at -35dBm on average. Apparently the transmission power set on radio A is more than enough, and we want to reduce it to increase battery life and also to avoid saturation on other nearby radios.

Regarding this, I have two questions:

1) What is the minimum RSSI as measured by receiving radio (B) that will ensure reliably communication? The stated receiver sensitivity of CC1310 at 50kbps is -110dBm, plus the gain of 2dBm from LNA on CC1190. Can we expect reliably communication when average RSSI measured by receiving radio is around -70~-80dBm? I understand this is likely affected by how noisy the installation environment, but a rule of thumb will still be helpful.

2) How do we calculate how much transmission power to reduce?  -35dBM (Current RSSI) - -70dBm (minimum RSSI required for reliable communication)?

Please advise and thanks in advance.

ZL

  • +1
    Mastermind 6620 points

    If you look at https://www.ti.com/tool/RF-RANGE-ESTIMATOR, the calculation include what margin TI uses. The margin is an installation margin mainly since you could have negative interference some places etc. You should also look at the noise level where you want to install since, as an example, Chine and India, have very high noise floor some places. You can also consider a dynamic approach where you start at a low level and if you fail to get connection, increase the output power until you do.

    Note that the PA table is limited for CC1310 + CC1190 meaning that you will not be able to reduce the output power that much. 

  • 0 in reply to TheGhostOf
    Expert 2920 points

    Thanks for your reply. The range estimator does help a lot. But I was hoping there might be a simple and easy way to calculate.