10.1.3 Measurements

36.3003GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Overall descriptionRelease 17Stage 2TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

10.1.3.0 General

Measurements to be performed by a UE for intra/inter-frequency/inter-RAT mobility can be controlled by E-UTRAN, using broadcast or dedicated control. In RRC_IDLE state, a UE shall follow the measurement parameters defined for cell reselection specified by the E-UTRAN broadcast. The use of dedicated measurement control for RRC_IDLE state is possible through the provision of UE specific priorities (see clause 10.2.4). In RRC_CONNECTED state, a UE shall follow the measurement configurations specified by RRC directed from the E-UTRAN (e.g. as in UTRAN MEASUREMENT_CONTROL).

In RRC_IDLE and RRC_CONNECTED the UE may be configured to monitor some UTRA or E-UTRA carriers according to reduced performance requirements as specified in TS 36.133 [21].

In RRC_IDLE, for NB-IoT UEs, BL UEs or UEs in enhanced coverage, the UE may further limit the intra-frequency and inter-frequency measurements when the relaxed monitoring criterion is fulfilled as specified in TS 36.304 [11].

In RRC_IDLE, for NB-IoT UEs, when enabled in the cell and the relaxed monitoring criterion is fulfilled, the UE may perform serving cell measurements on the non-anchor paging carrier as specified in TS 36.133 [21].

For CSI-RS based discovery signals measurements, "cell" should be interpreted as "transmission point of the concerned cell" in the following descriptions.

Intra-frequency neighbour (cell) measurements, inter-frequency neighbour (cell) measurements and inter-RAT measurements are defined as follows:

– Intra-frequency neighbour (cell) measurements: Neighbour cell measurements performed by the UE are intra-frequency measurements when the current and target cell operates on the same carrier frequency.

– Inter-frequency neighbour (cell) measurements: Neighbour cell measurements performed by the UE are inter-frequency measurements when the neighbour cell operates on a different carrier frequency, compared to the current cell.

– Inter-RAT neighbour (cell) measurements: Neighbour cell measurements performed by the UE are inter-RAT measurements when the neighbour cell operates on a different RAT, compared to the current cell.

Whether a measurement is non gap assisted or gap assisted depends on the UE’s capability and the current operating frequency. In non gap assisted scenarios, the UE shall be able to carry out such measurements without measurement gaps. In gap assisted scenarios, the UE may not be able to perform such measurements without measurement gaps. The UE determines whether a particular cell measurement needs to be performed in a transmission/reception gap and the scheduler needs to know whether gaps are needed:

– Same carrier frequency and cell bandwidths (Scenario A): an intra-frequency scenario; not measurement gap assisted.

– Same carrier frequency, bandwidth of the target cell smaller than the bandwidth of the current cell (Scenario B): an intra-frequency scenario; not measurement gap assisted.

– Same carrier frequency, bandwidth of the target cell larger than the bandwidth of the current cell (Scenario C): an intra-frequency scenario; not measurement gap assisted.

– Different carrier frequencies, bandwidth of the target cell smaller than the bandwidth of the current cell and bandwidth of the target cell within bandwidth of the current cell (Scenario D): an inter-frequency scenario; measurement gap-assisted scenario.

– Different carrier frequencies, bandwidth of the target cell larger than the bandwidth of the current cell and bandwidth of the current cell within bandwidth of the target cell (Scenario E): an inter-frequency scenario; measurement gap-assisted scenario.

– Different carrier frequencies and non-overlapping bandwidth, (Scenario F): an inter-frequency scenario; measurement gap-assisted scenario.

– Same carrier frequency, the operating frequency of the bandwidth reduced low complexity (BL) UE or the UE in Enhanced Coverage is not guaranteed to be aligned with the center frequency of the current cell (Scenario G): an intra-frequency scenario; measurement gap assisted scenario.

Figure 10.1.3-1: Inter and Intra-frequency measurements scenarios

Measurement gaps may be needed by the UE to carry out inter-RAT measurements on NR frequencies. UE may need measurement gaps to perform inter-RAT measurements on NR frequencies depending on the UE’s need for gap capability, as well as the UE capability to support independent FR measurement as specified in TS 38.306 [89]. The UE may not be able to perform inter-RAT NR measurements without measurement gaps in the following cases:

– If the UE only supports per-UE gaps and the UE is required to measure NR frequencies:

– If the UE supports per-FR gaps and the UE is required to measure at least one NR frequency in FR1;

Measurement gaps patterns are configured and activated by RRC.

When CA is configured, the "current cell" above refers to any serving cell of the configured set of serving cells. For instance, for the definition of intra and inter frequency measurements, this means:

– Intra-frequency neighbour (cell) measurements: Neighbour cell measurements performed by the UE are intra-frequency measurements when one of the serving cells of the configured set and the target cell operates on the same carrier frequency. The UE shall be able to carry out such measurements without measurement gaps.

When DC is configured, the following principles are applied:

– The configured set of serving cells includes all the cells from MCG and SCG as for CA;

– The measurement procedure of serving cells belonging to the SeNB shall not be impacted due to RLF of SeNB;

– Common gap for the MeNB and the SeNB is applied;

– There is only a single measurement gap configuration for the UE which is controlled and informed by the MeNB.

– UE determines the starting point of the measurement gap based on the SFN, subframe number and subframe boundaries of the MCG serving cells.

When LAA is configured:

– The eNB configures the UE with one DMTC window for all neighbor cells as well as for the serving cell (if any) on one frequency;

– The UE is only expected to detect and measure cells transmitting DRS during the configured DRS DMTC window;

– For channel selection in an environment where hidden nodes may exist, UE may be configured with one RMTC per a frequency to perform RSSI measurement, and to report average RSSI and channel occupancy (percentage of measurement samples that RSSI value is above a threshold) in a reporting interval.

For NB-IoT, measurements in RRC_CONNECTED are optionally supported to reduce the time taken for RRC reestablishment. The following principles are applied:

– The "current cell" above refers to the configured carrier in the serving cell. The "target cell" above refers to the anchor carrier in the target cell. For instance, for the definition of intra and inter frequency measurements, this means:

– Intra-frequency neighbour (carrier) measurements: Neighbour carrier measurements performed by the UE are intra-frequency measurements when the configured carrier in the serving cell and the anchor carrier in the target cell operates on the same carrier frequency. The UE shall be able to carry out such measurements without measurement gaps.

– Inter-frequency neighbour (carrier) measurements: Neighbour cell measurements performed by the UE are inter-frequency measurements when the configured carrier in the serving cell and the anchor carrier in the target cell operates on a different carrier frequency. The UE may not be able to perform such measurements without measurement gaps.

– The eNB configures the criteria to perform measurements via broadcast signalling;

– Dedicated measurements gaps are not supported. The UE may need to perform neighbour cell measurements during DL/UL idle periods that are provided by DRX or packet scheduling;

– Measurement reporting is not supported.

10.1.3.1 Intra-frequency neighbour (cell) measurements

In a system with frequency reuse = 1, mobility within the same frequency layer (i.e. between cells with the same carrier frequency) is predominant. Good neighbour cell measurements are needed for cells that have the same carrier frequency as the serving cell in order to ensure good mobility support and easy network deployment. Search for neighbour cells with the same carrier frequency as the serving cell, and measurements of the relevant quantities for identified cells are needed.

NOTE: To avoid UE activity outside the DRX cycle, the reporting criteria for neighbour cell measurements should match the used DRX cycle.

10.1.3.2 Inter-frequency neighbour (cell) measurements

Regarding mobility between different frequency layers (i.e. between cells with a different carrier frequency), UE may need to perform neighbour cell measurements during DL/UL idle periods that are provided by DRX or packet scheduling (i.e. gap assisted measurements).

Network may request UE to measure inter-frequency carriers in RRC_IDLE or RRC_INACTIVE via system information or via dedicated measurement configuration in RRC Connection Release. The UE performs the requested measurements and may provide an indication of the availability of measurement report to the eNB during RRC Connection Setup or Resume procedure. The network may request UE to report those measurements after security activation. The request for the measurements can be sent by the network immediately after transmitting the Security Mode Command (i.e. before the reception of the Security Mode Complete from the UE). Alternatively, during connection resume from suspended RRC connection or from RRC_INACTIVE, the eNB can request the UE to provide idle/inactive measurement results in the RRCConnectionResume message and then the UE can include the available measurement results in the RRCConnectionResumeComplete message.