Some GSM, UMTS and LTE Measurement Units

GSM
Here, the world is still quite simple. Once the mobile has found a cell it keeps monitoring it's received signal power and computes the Received Signal Strength Indicator (RSSI) over the complete carrier frequency (200 kHz). Neighboring cells use different frequencies and the same value is calculated for those as well.
UMTS
Here, things get a bit more complicated as all cells use the same frequency. As a result not only the received signal strength is important but also the noise level generated by neighboring cells. In the end, what good does it do to you when the signal level is strong but most of it is interference? That's why there are three values:

• 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).

• RSSI: In UMTS that's the signal power over the complete 5 MHz carrier which includes all components received, including the signals from neighboring cells on the same frequency.

• EcNo: (Signal to Noise ratio): 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 the signal can be distinguished from the noise and the faster the data transmission will be. 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.

LTE
LTE networks also use the same carrier frequency in neighboring cells so again the signal level and interference are important:

• RSRP: That's the Received Power of the Reference Signal.

• RSSI: That's the total received power including Interference from neighboring cells and other sources.

• RSRQ: That's the Reference Signal Received Quality and equals the RSRP divided by the RSSI. As above the better this value, the better can the signal of the cell be received against the interference generated by other cells. It's kind of the EcNo of LTE...

Quite a lot of similarities between UMTS and LTE from a high level point of view even though the values are measured in quite a different way due to the different air interface natures (WCDMA vs. OFDMA).

source:internet