LTE UE Physical Layer Measurements

Physical layer measurements in LTE UE and also eNB is carried out on both the downlink as well as uplink. It is carried out at layer-1 and reported to higher layers for various functions as listed below.
•   Intra and inter frequency handover
•  Inter RAT (Radio Access Technology) handover
•  Timing measurements
•  funtions to support RRM

LTE UE physical layer measurements are defined in 3GPP 36.214 document. Following are the measurements done in UE. As LTE UE is mobile in nature and hence need to work with GSM, CDMA200, UMTS TDD and UMTS FDD networks. Measurements with respect to those RATs are also need to be carried out in LTE UE.

Reference Signal Receive Power(RSRP)

Reference Signal Receive Power(RSRP) is linear average power across channel bandwidth for the LTE reference signals(RSs). RS exists only in one symbol at any time. It is measured using REs which contain cell specific RS. The absolute limit range is from +/-6 dB to +/-11 dB.

Reference Signal Receive Quality(RSRQ)

Reference Signal Receive Quality(RSRQ) provides measure of signal quality. It is defined as ratio of RSRP tp E-UTRA carrier RSSI. Reference signal receive quality is measured only during connected states. Absolute RSRQ accuracy range is from +/-2.5dB to +/-4dB. It is almost same as inter frequency relative RSRQ range of +/-3dB to +/-4dB.

UTRA FDD CPICH RSCP

UTRA FDD CPICH RSCP is derived from UMTS. It is a measure of absolute power of one code channel within overall UTRA CDMA signal. UTRA FDD CPICH RSCP is measure of code power of CPICH. It is used for interworking between LTE and UMTS RATs. It is similar to RSRP of LTE. It is used in LTE inter RAT IDLE and CONNECTED states.

UTRA FDD carrier RSSI

UTRA FDD carrier RSSI is also derived from UMTS. It is measure of total received power including thermal noise and noise generated in the receiver. It is measured across the receiver pulse shaping filter bandwidth. It is same as E-UTRA carrier RSSI defined as RSRQ.

UTRA FDD CPICH Ec/No

UTRA FDD CPICH Ec/No is basically ratio of CPICH to power density in the channel. If diversity is not enabled than it is equal to (CPICH RSCP/RSSI). Typically it will be about -10dB.UTRA FDD CPICH Ec/No is used in LTE inter-RAT IDLE and CONNECTED STATES.

GSM Carrier RSSI

GSM Carrier RSSI is measured by LTE UE when it has to interwork with GSM/EGPRS systems. It is measured on BCCH channel. It is used when UE is in IDLE and CONNECTED states.

UTRA TDD Carrier RSSI

UTRA TDD Carrier RSSI is used for interworking with UTRA TDD based systems. It is similar to other RAT RSSI. It is carried out when UE is in inter-RAT IDLE and CONNECTED states.

UTRA TDD P-CCPCH RSCP

UTRA TDD P-CCPCH RSCP is a measure of code power of the primary common control physical channel (P-CCPCH). It is used in LTE inter-RAT IDLE and CONNECTED states. It is same as UTRA TDD RSRP.

CDMA2000 1xRTT Pilot Strength

CDMA2000 1xRTT Pilot Strength is RSRP equivalent of CDMA2000 system. It is as per 1.22Mcps chip rate system. The CDMA2000 pilot is carried on walsh code 0. It is typically about -7dB from the total downlink power.

CDMA2000 HRPD Pilot Strength

CDMA2000 HRPD Pilot Strength is defined in the time domain. It exists about 9.375% of the frame. It is important when UE is interworking with HRPD(High Rate Packet Data) systems. It is another variant of LTE RSRP.

Reference signal time difference(RSTD)

Reference signal time difference(RSTD) is measured during inter and intra frequency RRC CONNECTED states. It is relative time difference between UE receives subframe from one cell j and another cell i at the antenna connector.

UE GNSS Timing of Cell Frame for UE positioning

UE GNSS Timing of Cell Frame for UE positioning is applicable when UE is in RRC CONNECTED intra frequency state. The timing between cell j and a GNSS-specific reference time for a given GNSS (e.g., GPS/Galileo/Glonass system time).

UE GNSS code measurements

UE GNSS code measurements not related to E-UTRAN/UTRAN/GSM signals. Hence it is independent of the UE state. The GNSS code phase (integer and fractional parts) of the spreading code of the ith GNSS compliant signal. Antenna connector of UE is taken as reference point.

UE Rx CE Tx time difference

UE Rx CE Tx time difference is carried out when UE is in RRC CONNECTED intra frequency. The UE Rx - Tx time difference is defined as T_UE-RX - T_UE-TX
Where:
T_UE-RX is the UE received timing of DL frame #i from the serving cell, defined by the first detected path in the time.
T_UE-TX is the UE transmit timing of uplink radio frame #i. The reference point for the UE Rx - Tx time difference measurement shall be the UE antenna connector.

Article on Physical layer Measurement

This article describes physical layer measurements as per OFDM physical layer specifications. The OFDM baseband measurements covers power, EVM, EVM per subcarrier, EVM per symbol, CCDF, I& Q constellations, spectral flatness, CFR, READ MORE.

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