Can I get BLE Other Signal Indicator not just RSSI?

Question

I'd like to collect other device's Signal information for more delicate communication. 
 For example, Some Peripheral device which is just next to Smartphone (which can interfere signal -> RSSI value changes capriciously) might be scanned by central, but it is not guaranteed that It will have safety Connection. 
 As in this case, I'd like to rip off such devices fickle like this from my connection queue. 
 To Make it simple, I can't rely on this Not so sure RSSI Value, So I'd like to make it sure. 
 As I found I can make this RSSI Value by using SNR (Signal Noise Ratio) or other Siganl Parameter such as (COI, CNR, TX Ratio or Etc... Actually I'm not sure about this acronym....) 
 Q1. How Can I make this RSSI Value to be reliable values? Any other ways to back-up this RSSI? 
 Q2.Is there any other signal parameter that I can use to make more elaborate RSSI Value? or make more safe connection?

endnode · Accepted Answer

There is nothing "sure" with 2.4GHz radio, so from this point of view you might be setting unrealistic goals. In normal situation missing CONNECT_REQ packet on Peripheral side (this is what you are afraid of?) is mostly because of direct interference by another CONNECT_REQ or SCAN_REQ packet (remember that Peripheral listens only during very narrow 1~2us window at 150us mark right after the end of ADV_IND Tx packet). The other reason is that devices are too "far" (from radio point of view: arriving CONNECT_REQ signal strength is close to sensitivity threshold of the receiver). There is pretty much no defense against first scenario (one of inherently week points of BLE design) and the countermeasure to second is simply "don't try to connect to objects which appear to be very far = RSSI is lower then -60/-70/-80/-90dBm (depending on sensitivity you want to target and your own Tx signal strength, antenna performance/directivity etc...)". 
 To your questions: 
 A1: There is nothing to be done with single chip and antenna, you have just RSSI with all the variations caused by changing environment (because 2.4GHz radio is simply too complex problem). 
 A2: You can start to combine multiple antennas (+ one BLE chip and RF spliter which allows you to rotate Rx periods over these) or even better multiple antennas and multiple RF front-ends (= BLE chips). There were several Q&As on this forum about this idea, however it's real science to design the system HW and SW wise in order to get some better understanding about what is happening around in real time. 
 Good luck!
Jan

Can I get BLE Other Signal Indicator not just RSSI?

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