RSRQ = (N * RSRP)/ RSSI .
Where RSRP is the linear average of reference signal power seen by UE. While taking average on those PREs would be considered which carry reference signal power. (2 Physical resource elements per Physical Resource block).
RSSI is the liner average of power seen by UE for OFDM symbols referring antenna port 0 over the N resource blocks.
RSSI considers serving cell power, neighbor cells power, noise etc.
As per my knowledge, If you have ideal figure of RSRQ, I mean to say there is no interference, noise at all in the system then by comparing ideal RSRQ value actual RSRQ, SINR can be find out. But I am not sure since I never work for physical layer.
