RSCP. The Received Signal Code Power: That’s the power level the pilot channel of a cell is received with and usually expressed in dBm (mW on a logarithmic scale). With this parameter, different cells using the same carrier can be compared and handover or cell reselection decisions can be taken.

RSSI. In UMTS that’s the signal power over the complete 5 MHz carrier which includes all components received, including the signals from the current and neighboring cells on the same frequency. In an isolated cell having only CPICH power to transmit and with none of the other channels utilized, the effective RSSI can be seen by the UE would be (fraction of) PCPICH power. However RSSI changes when the 5MHz carrier will carry power for other dedicated or control channels. In that case, the effective power perceived By the UE would be the transmitted power of the serving cell + the power transmitted by neighbor cells over the same carrier frequency.

EcNo. That’s the received energy per chip (Ec) of the pilot channel divided by the total noise power density (No). In other words the EcNo is the RSCP divided by the RSSI. And Again in other words: The better this value the better can a signal of a cell be distinguished from the overall noise. The EcNo is usually expressed in dB as it’s a relative value. The value is negative as the RSCP is smaller than the total received power. As the RSCP this Value can be used to compare different cells on the same carrier and handover or cell reselection decisions can be taken.