Received signal code power
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RSCP is an acronym used in UMTS and other CDMA cellular communications systems and stands for Received Signal Code Power.
While RSCP can be defined generally for any CDMA system, it is more specifically used in UMTS. Also, while RSCP can be measured in principle on the downlink (DL) as well as on the uplink (UL), it is usually associated only with the downlink and thus it is presumed to be measured by the UE and reported to the Node-B. It is defined by 3GPP as follows:
Definition: the received power on one code after de-spreading measured by UE on the pilot bits on a given channel. The reference point for the RSCP is the antenna connector of the UE. If Tx diversity is applied on the measured channel then the received code power from each antenna is separately measured and summed together in watt to produce a total received code power on the measured channel.
RSCP is used in UMTS as a handover criterion and in DL and UL open loop power control, UL open loop power control and for calculation of pathloss using the formula:
- Pathloss = Transmitted channel power [dBm] - RSCP [dBm]
In UMTS FDD-mode RSCP is measured on Primary CPICH, in TDD-mode it is measured on the pilot bits of Primary CCPCH.
In UMTS RSCP is measured in dBm (decibels relative to 1 watt power) within a bandwidth of 3.84 MHz. In UMTS FDD messages RSCP is transmitted as an integer value in the range of -115 dBm to -25 dBm. The value is coded into integers from 0 to 99 according to the following table:
| Reported value | Measured quantity value |
|---|---|
| CPICH_RSCP_LEV _00 | CPICH RSCP <-115 |
| CPICH_RSCP_LEV _01 | -115 ≤ CPICH RSCP < -114 |
| CPICH_RSCP_LEV _02 | -114 ≤ CPICH RSCP < -113 |
| ... | ... |
| CPICH_RSCP_LEV _89 | -27 ≤ CPICH RSCP < -26 |
| CPICH_RSCP_LEV _90 | -26 ≤ CPICH RSCP < -25 |
| CPICH_RSCP_LEV _91 | -25 ≤ CPICH RSCP |
| CPICH_RSCP_LEV _92 | (spare, value not assigned) |
| CPICH_RSCP_LEV _93 | (spare, value not assigned) |
| ... | ... |
| CPICH_RSCP_LEV _99 | (spare, value not assigned) |
The accuracy with which RSCP is reported in UMTS FDD is in the range of 6 dB to 11 dB (absolute accuracy) and ±3 dB (relative accuracy).
References and further reading
- RSCP is defined by 3GPP for UMTS in 25.133 Requirements for support of radio resource management (FDD). This source contains the above table for coding the values of RSCP in UMTS messages. It also specifies the error margin when measurening RSCP in UMTS.
- Some additional information about sending RSCP measured values in UMTS messages can be found in 3GPP 25.331 Radio Resource Control (RRC);Protocol Specification