SINR (Signal to Interference & Noise Ratio) is a measure of signal quality as well but it is not defined in the 3GPP specs but defined by the UE vendor.
It is not reported to the network. SINR is used a lot by operators, and the LTE industry in general, as it better quantifies the relationship between RF conditions and Throughput. UEs typically use SINR to calculate the CQI (Channel Quality Indicator) they report to the network.
Relation between SINR and RSRQ
Credit: http://tech.queryhome.com/78263/what-is-the-relationship-between-rsrp-and-sinr
