Why we do we need PRS when we have SSB and CSI RS in NR
When i went through qualcomm paper on otdoa it is mentioned as
“However, these DL signals suffer from poor hearability, which is crucial for OTDOA positioning when multiple neighbour cell signals have to be detected by the UE. A neighbour cell with its synchronization signals (Primary-/Secondary Synchronization Signals) and reference signals is seen as detectable, when the Signal-to-Interference-and- Noise Ratio (SINR) is at least 6 dB . However, this is not enough to detect a sufficient number of (geographically dispersed) eNodeB’s.
Therefore, Positioning Reference Signals (PRS) have been introduced in the 3GPP LTE Release-9 standard to allow proper timing (ranging) measurements of a UE from eNodeB signals to improve OTDOA positioning performance.”
Can anyone explain me what is “poor hearability,” and “Signal-to-Interference-and- Noise Ratio (SINR) is at least 6 dB”