Low power reference signal for cell reselection - Patents.com

Abstract

Various examples of the present disclosure relate to using a cell-specific low power reference signal, which may be received using a low power receiver, for cell reselection.

Description

[Technical field]

[0001] Various examples of the present disclosure relate to reference signals designed for reception by a low power receiver of a wireless communication device, and to performing cell reselection based on channel measurements based on such low power reference signals. [Background technology]

[0002] Energy-efficient operation is a key design requirement for wireless communication devices (User Equipment, UE). Low power consumption facilitates extended battery life. Furthermore, smaller batteries, e.g. coin cell batteries, can be used. Internet of Things smart devices can be enabled.

[0003] One technique for facilitating low power consumption is to employ multiple receivers, a primary receiver, and a low power receiver. For example, the low power receiver may be configured for non-coherent decoding, in which knowledge of a reference phase is not required for signal detection. This can significantly reduce the energy consumption required for channel listening. For example, for UEs that communicate a wake-up signal (WUS) according to the 3rd Generation Partnership Project (3GPP®) protocol, a low power receiver is employed, see 3GPP Technical Specification (TS) 36.300, version 16.2.0, e.g., section 10.1.4. Summary of the Invention [Problem to be solved by the invention]

[0004] There is a need for energy efficient operation of UEs. [Means for solving the problem]

[0005] This need is met by the features of the independent claims. The features of the dependent claims define embodiments.

[0006] Techniques are disclosed for operating a UE at low power consumption. These techniques employ a low power reference signal (LP-RS) to support channel measurements and assessment of serving cell signal strength for the UE using a low power receiver (LP-Rx). Alternatively or additionally, neighbor cell signal strength may be assessed.

[0007] Various examples relate to performing cell reselection based on channel measurements based on the LP-RS. To perform cell reselection, it may not be required that the primary receiver (M-Rx) is operated in an active state, for example to receive signals. Cell reselection may be concluded based on channel measurements performed using only the LP-Rx, without requiring operation of the M-Rx.

[0008] A method of operating a wireless communication device in a cellular network is disclosed. The cellular network includes a number of cells, each of which broadcasts a cell-specific high power reference signal. The method includes obtaining an indication of a plurality of cells of the plurality of cells from the cellular network. Base stations of the plurality of cells each broadcast a cell-specific low power reference signal. The method also includes monitoring the cell-specific low power reference signal while operating in an idle mode. The method also includes, upon successful reception of the cell-specific low power reference signal from at least one base station of at least one of the plurality of cells, performing cell reselection from among the plurality of cells based on the cell-specific low power reference signal. The method further includes, upon failure to receive the cell-specific low power reference signal, monitoring the cell-specific high power reference signal for performing cell reselection.

[0009] For example, channel measurements may be performed based on a received cell-specific low power reference signal. Received signal strength and / or received signal quality may be determined. One or more cell reselection criteria may be considered based on the channel measurements. Depending on the result of the cell reselection evaluation, cell reselection may or may not be performed. Depending on the result of the cell reselection evaluation, a fallback to monitoring a cell-specific high power reference signal may be performed.

[0010] A computer program or computer program product or computer readable storage medium includes program code executable by at least one processor. The at least one processor, when executing the program code, performs a method of operating a wireless communication device in a cellular network is disclosed. The cellular network includes a number of cells, each of which broadcasts a cell-specific high power reference signal. The method includes obtaining an indication of a plurality of cells of the number of cells from the cellular network. Base stations of the plurality of cells each broadcast a cell-specific low power reference signal. The method also includes monitoring the cell-specific low power reference signal while operating in an idle mode. The method also includes, upon successful reception of the cell-specific low power reference signal from at least one base station of at least one of the plurality of cells, performing cell reselection from among the plurality of cells based on the cell-specific low power reference signal. The method further includes, upon failure to receive the cell-specific low power reference signal, monitoring the cell-specific high power reference signal for performing cell reselection.

[0011] The wireless communication device comprises at least one processor and a memory storing program code. The at least one processor is capable of loading and executing the program code. When the at least one processor executes the program code, a method of operating a wireless communication device in a cellular network is disclosed. The cellular network includes a number of cells, each of which broadcasts a cell-specific high power reference signal. The method includes obtaining an indication of a plurality of cells of the number of cells from the cellular network. Base stations of the plurality of cells each broadcast a cell-specific low power reference signal. The method also includes monitoring the cell-specific low power reference signal while operating in an idle mode. The method also includes performing cell reselection from among the plurality of cells based on the cell-specific low power reference signal upon successful reception of the cell-specific low power reference signal from at least one base station of at least one of the plurality of cells. The method further includes monitoring the cell-specific high power reference signal for performing cell reselection upon failure to receive the cell-specific low power reference signal.

[0012] A method of operating base stations associated with cells of a cellular network, where each cell of the multiple cells broadcasts a cell-specific high power reference signal, includes providing an indication of a plurality of cells of the multiple cells to a wireless communication device. The base stations of the plurality of cells each broadcast a cell-specific low power reference signal that enables cell reselection among the plurality of cells at the wireless communication device. The method also includes broadcasting the low power reference signals.

[0013] The computer program or computer program product or computer readable storage medium includes program code. The program code can be loaded and executed by at least one processor. When the at least one processor executes the program code, it performs a method of operating a base station associated with a cell of a number of cells of a cellular network, where each cell of the number of cells broadcasts a cell-specific high power reference signal. The method includes providing an indication of a number of cells of the number of cells to a wireless communication device. The base stations of the number of cells each broadcast a cell-specific low power reference signal that enables cell reselection among the number of cells at the wireless communication device. The method also includes broadcasting the low power reference signal.

[0014] A respective base station is disclosed that includes at least one processor and a memory that stores program code.

[0015] It is to be understood that the features mentioned above, and the features not yet described below, may be used not only in the respective combinations shown, but also in other combinations or alone without departing from the scope of the invention. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a communication system, in accordance with various examples. [Diagram 2] FIG. 2 is a diagram that illustrates a schematic of multiple cells of a cellular network, in accordance with various examples. [Diagram 3] FIG. 3 is a schematic diagram of a base station, in accordance with various examples. [Figure 4] FIG. 4 is a schematic diagram of a UE, in accordance with various examples. [Figure 5A] FIG. 5A is a flowchart of a method, according to various examples. [Figure 5B] FIG. 5B is a flowchart of a method, according to various examples. [Figure 5C] FIG. 5C is a flowchart of a method, according to various examples. [Figure 6] FIG. 6 is a diagram that illustrates generally signal levels obtained from channel measurements on low power reference signals for multiple cells, according to various examples. [Figure 7] FIG. 7 is a flowchart of a method, according to various examples. [Figure 8] FIG. 8 is a signaling diagram in accordance with various examples. [Figure 9] FIG. 9 is a signaling diagram according to various examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In the following, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the following description of the embodiments should not be interpreted in a limiting sense. The scope of the present invention is not intended to be limited by the embodiments described below or by the drawings, which are interpreted as being merely exemplary.

[0018] The drawings should be considered as schematic representations, and the elements shown in the drawings are not necessarily drawn to scale. Rather, the various elements are represented so that their function and general purpose are apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by indirect connections or couplings. Coupling between components may also be established via wireless connections. The functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0019] In the following, techniques for wirelessly transmitting and / or receiving (communicating) between multiple communication nodes are described. In various examples described herein, various types of communication systems may be used. For example, a communication network may be employed. The communication network may be a wireless network. For simplicity, various scenarios are described below with respect to an implementation of the communication network by a cellular network (NW). The cellular network includes multiple cells. Each cell corresponds to a respective subarea of ​​the overall coverage area. Other exemplary implementations include a multi-area wireless network, such as a cellular WiFi network.

[0020] Below, the techniques are described with respect to a UE communicating with a base station (BS) of a cellular network. The BS is associated with a cell of the cellular network.

[0021] Aspects related to cell reselection are disclosed. For example, if the signal strength of the serving cell does not meet a certain requirement (e.g., due to mobility), the UE performs cell reselection. As part of the cell reselection, channel measurements performed based on LP-RS broadcasted by multiple base stations (BSs) of multiple cells of the cellular NW are evaluated to determine whether to stay in the current cell or switch cells.

[0022] In general, cell reselection aims to ensure that the UE is on the best cell. For example, cell reselection may be performed in response to the further cell being better than the serving cell. For this purpose, the relative difference in signal strength between the serving cell and the further cell may be taken into account. This avoids unnecessary energy waste in channel measurements.

[0023] Energy efficiency is a key design requirement for UEs with limited energy resources, e.g., UEs that use small rechargeable and / or coin-cell batteries. Among use cases, sensors and actuators are widely deployed for monitoring, measuring, charging, etc. In general, their batteries are not rechargeable and are expected to last at most or at least several years, as described in 3rd Generation Partnership Project (3GPP) Technical Requirement (TR) 38.875. Wearables include smart watches, rings, e-health related devices, and medical monitoring devices. With typical battery capacities, it is difficult to last up to 1-2 weeks.

[0024] Various techniques disclosed herein facilitate low power consumption for such and other types of UEs.

[0025] According to various examples, the UE includes an M-Rx and an LP-Rx. Generally, the LP-Rx and the M-Rx may be implemented within the same hardware component or may be implemented by at least one different hardware component. Using an additional LP-Rx in addition to the M-Rx can significantly reduce the cost of idle channel listening, and therefore reduce UE power consumption, since the LP-Rx listens for potential DL communications.

[0026] The LP-Rx may be configured to perform time-domain processing to detect a particular signal, e.g., a reference signal (RS), a wake-up signal (WUS). The time-domain processing may be processing in baseband, i.e., a baseband waveform may be processed in the time domain. The LP-Rx may be unsuitable for performing orthogonal frequency division multiplexing (OFDM) demodulation, i.e., decoding symbols on multiple orthogonal subcarriers of a joint carrier. For example, the LP-Rx may be configured to perform non-coherent decoding, in which knowledge of a reference phase is not required for signal detection.

[0027] The M-Rx may be configured for OFDM demodulation. The M-Rx may be configured to perform both time domain and frequency domain processing.

[0028] The LP-Rx may facilitate WUS techniques. WUS techniques allow the UE to transition the M-Rx to a low power state, e.g., for power saving purposes. The M-Rx may also have transmission capabilities (i.e., a transceiver), but this is not relevant in the described context. In some examples, the low power state of the M-Rx may be an inactive state. The inactive state may be characterized by a significant reduction in power consumption compared to the active state of the M-Rx. For example, the M-Rx may be unsuitable to receive data in the inactive state, such that some or all components may be shut down. A wake-up of the M-Rx from the inactive state (i.e., transition to an active state) is then triggered by the WUS. The inactive state may relate to various operating modes of the terminal, e.g., a disconnected mode or an idle mode. Here, the data connection between the terminal and the cellular network may be released.

[0029] The WUS may be detected by the LP-Rx. The UE may use the LP-Rx to monitor the WUS at a given WUS opportunity.

[0030] Specifically, the UE may operate the LP-Rx in an active state while the M-Rx is operated in an inactive state, and the UE may operate the LP-Rx in an active state while operating in an idle mode, where a data connection between the UE and the cellular network is not maintained.

[0031] When operating in idle mode, the UE may use discontinuous reception (DRX), for example, for LP-Rx and / or M-Rx. When using LP-Rx, the UE may transition M-Rx to an inactive state while using only LP-Rx (e.g., in combination with DRX). For example, the UE may transition LP-Rx to an inactive state during the off duration of DRX. Sometimes, during the on duration of DRX, the UE transitions the LP-Rx active state. This is done for various purposes. First, it is done to check whether the cellular NW is trying to reach the UE, e.g., to transmit downlink (DL) data. This may be performed using WUS during a WUS opportunity. Second, it is done to perform channel measurements for evaluation on cell reselection. The UE may move from the coverage of the current cell to another cell, e.g., due to mobility during the off duration of DRX. This may be detected based on the channel measurements.

[0032] In the following, a technique is disclosed in which a UE may activate its LP-Rx during the on duration of a DRX cycle to monitor (i.e., attempt to receive) the LP-RS while operating in an idle mode using DRX. Then, based on such monitoring of the LP-RS, a channel measurement may be performed. For example, the signal strength of the received LP-RS may be determined. Then, under certain circumstances, cell reselection from among multiple cells of a cellular network may be performed based on the channel measurement. For example, cell reselection may be performed when the signal strength of a currently selected cell deteriorates below a predetermined threshold. Cell reselection may be performed when a further cell different from the currently selected cell is available that has a better signal strength than the currently selected cell.

[0033] Cell reselection is the process by which a UE decides to switch from camping on a first cell to camping on a second cell while operating in idle mode, i.e., to monitor signals from the second cell instead of the first cell. Cell reselection differs from handover during connected mode because the decision to reselect a cell is made autonomously by the UE rather than being commanded by the cellular NW by a handover message.

[0034] In prior art implementations, reference signals (RS) available for cell reselection, i.e., synchronization or reference signals of neighbor cells, can only be measured using M-Rx. Even if the UE is equipped with LP-Rx, there is no support for low power cell reselection evaluation mechanisms.

[0035] In this disclosure, a low power mechanism is described to support mobility and cell reselection for UEs with LP-Rx. Thus, the UE can perform channel measurements for cell reselection purposes using LP-Rx without the need to activate / use M-Rx. Procedures are disclosed so that the UE can perform cell reselection using only LP-Rx and initiate camping on a new cell without activating M-Rx. This reduces overall power consumption while maintaining accurate mobility control.

[0036] According to some examples disclosed herein, the UE may move around cells included in the LP-RS neighbor cell list without requiring additional information that is received only using M-Rx. The UE may obtain an indication of multiple cells, i.e., cells in the LP-RS neighbor cell list, from the cellular network.

[0037] Techniques for determining the LP-RS neighbor cell list are described. Various design criteria may be considered when determining the LP-RS neighbor cell list. Exemplary design criteria include one or more of: only cells operating in the same frequency or frequency range are included in the LP-RS neighbor cell list; only cells that the UE does not prohibit from accessing are included in the LP-RS neighbor cell list; only cells included in a common tracking area are considered in the LP-RS neighbor cell list; and only cells that have the same or similar WUS configuration and / or use the same timing of WUS opportunities are included in the LP-RS neighbor cell list. By using such design criteria, cell reselection that does not require additional configuration information may be facilitated, thereby avoiding the need to activate the UE M-Rx.

[0038] The LP-RS neighbor cell list may be determined by the BS or may be determined by a core network node, such as a mobility control node.

[0039] Fig. 1 shows a schematic diagram of a communication system 100. The communication system includes two nodes 101, 102 configured to communicate with each other via a data carrier 111. In the example of Fig. 1, the node 101 is implemented by an access node, more specifically a BS, and the node 102 is implemented by a UE. The BS 101 may be part of a cellular network (not shown in Fig. 1).

[0040] As shown in FIG. 1, there can be DL communication as well as UL communication.

[0041] The UE 102 and the BS 101 can communicate over a data carrier 111. The data carrier 111 may include multiple subcarriers for OFDM modulation. A data link 112 may be implemented on the data carrier 111. The data link 112 may include one or more logical channels that define a time-frequency resource grid. The data link 112 may be established, for example, based on a random access procedure of the UE 102, for example, in response to paging and wake-up events that may trigger the transmission of a WUS to the UE 102. The data link 112 may be established when operating in a connected mode, but may not be established when operating in an idle mode. The idle mode may also be referred to as an inactive mode, or, specifically, a radio resource control (RRC) idle or inactive state in the context of 3GPP New Radio (NR).

[0042] FIG. 2 shows a schematic of multiple cells of a cellular NW 870. Each cell 871-874 of the cellular NW 870 has a somewhat different coverage area. Each cell 871-874 is associated with one or more BSs, such as the BS 101 according to FIG. 1. When UE mobility of a UE, such as the UE 102, occurs, the UE may move from the coverage area of ​​a given cell to the coverage area of ​​another cell. Performing cell reselection based on channel measurements ensures that the UE monitors the signal of the BS of the appropriate cell 871-874. When the UE operates in an idle mode, the UE is said to be camped on a given cell, i.e., a serving cell, among the cells 871-874 of the cellular NW 870.

[0043] Generally, cell reselection is based on channel measurements. One or more cell reselection criteria may be taken into consideration. Cell reselection is performed only if one or more cell reselection criteria are met; otherwise, the UE does not reselect a cell. For example, based on the channel measurements, it may be determined whether the signal strength of the serving cell is at an appropriate level. If the signal strength of the serving cell does not meet one or more requirements (e.g., defined by cell reselection information), the UE enters a cell reselection evaluation procedure, and the evaluation identifies a cell on which the UE should camp. The cell reselection evaluation may include performing intra-frequency measurements on neighboring cells and / or inter-frequency measurements on neighboring cells. One exemplary cell reselection criterion or rule in 3GPP Technical Specification (TS) 38.304, version 16.7.0 (2021-12), section 5.2.4.2 for intra-frequency cell reselection purposes is that if the serving cell satisfies Srxlev>SIntraSearchP and Squal>SIntraSearchQ, the UE may choose not to perform intra-frequency measurements. Otherwise, the UE shall perform intra-frequency measurements. Here, Srxlev is the cell selection RX level value (dB), SIntraSearchP is the Srxlev threshold (in dB) for intra-frequency measurements, Squal is the cell selection quality value (in dB), and SIntraSearchQ is the Squal threshold (in dB) for intra-frequency measurements. The Rx level measurement (Srxlev threshold) is connected to the Reference Signal Received Power (RSRP) measurement, and the quality measurement (Squal threshold) is connected to the Reference Signal Received Quality (RSRQ) measurement.

[0044] In prior art implementations, signals available for cell reselection evaluation procedure, i.e., synchronization signals or reference signals of neighbor cells, can only be measured by M-Rx. Details of such prior art cell reselection are disclosed in 3GPP TS 38.331, version 17.5.0 (2022-03), section 4.2. In such prior art implementations, for cell reselection evaluation, as part of cell selection, the UE receives and decodes the Master Information Block (MIB) and System Information Block (SIB), SIB1, together with SIB2-5 of any candidate cells. The respective information is taken into account when reselecting a cell. The MIB defines the scheduling of SIB1 and whether the cell is forbidden. SIB1 defines the scheduling of other system information, including periodicity. SIB2 contains cell reselection information common to intra-frequency, inter-frequency and / or inter-RAT cell reselection. SIB4 contains information related only to inter-frequency cell reselection. SIB5 contains information related only to inter-RAT cell reselection. This means that even if a UE for performing cell reselection is equipped with an additional LP-Rx, it needs to transition the M-Rx to the active state in order to receive MIB, SIB1 to SIB5.

[0045] Activation of the M-Rx to perform cell reselection requires significant energy.

[0046] To mitigate this, a technique is disclosed that allows cell reselection to be performed based on the LP-RS without the need to activate the M-Rx. Idle mode mobility can be handled based on the LP-RS using the LP-Rx. Thus, the M-Rx may only need to be transitioned to an active state in the following scenarios: first, when there is DL payload data scheduled for transmission, e.g., as indicated by the WUS; and second, when there is UL payload data scheduled for transmission. In both scenarios, the UE may perform fine synchronization, where synchronization using the M-Rx is required.

[0047] 3 shows a schematic diagram of the BS 101. The BS 101 includes a processor 1011 and further includes a memory 1012 and a communication interface 1013. The processor 1011 can communicate with the UE 102 via the communication interface 1013. The communication interface 1013 can include analog electronics for accessing the carrier 111. The processor 1011 can load program code from the memory 1012 and can execute the program code. Upon executing the program code, the processor 1011 can perform the techniques described herein, such as activating an SSB broadcasting pattern, activating an LP-RS broadcasting pattern, sending configurations, such as properties, of an SSB, sending an SSB according to the SSB broadcasting pattern, sending configurations, such as properties, of an LP-RS, sending an LP-RS according to the LP-RS broadcasting pattern, obtaining capabilities from one or more UEs indicating whether one or more UEs can receive an LP-RS and determining whether to activate or not activate the LP-RS broadcasting pattern, sending at least one control signal indicating activation of the LP-RS broadcasting pattern, providing an indication to one or more UEs of a plurality of cells of the cellular NW that respectively broadcast the LP-RS, and / or determining an indication of a plurality of cells.

[0048] 4 shows a schematic diagram of the UE 102. The UE 102 includes a processor 1021 and further includes a memory 1022 and a communication interface 1023. The processor 1021 can communicate with the BS 101 via the communication interface 1023. The communication interface 1023 can include analog electronics for accessing the carrier 111. The processor 1021 can load program codes from the memory 1022 and execute the program codes. Executing the program code, the processor 1021 can perform techniques described herein, such as obtaining at least one control signal from the BS 101 indicating activation of the LP-RS broadcasting pattern, receiving configurations, such as properties, of the SSB and / or the LP-RS, selecting between monitoring the LP-RS and monitoring the SSB depending on one or more decision criteria, such as signal strength, mobility level, rate of change of signal strength and time hysteresis for switching, obtaining an indication from the cellular NW of multiple cells that support the LP-RS, i.e., BSs in those cells broadcast the LP-RS, performing cell reselection from among multiple cells based on the LP-RS, camping on the selected cell according to the cell reselection while operating in idle mode, etc.

[0049] FIG. 5A is a flowchart of a method, according to various examples. The method of FIG. 5A may be performed by a UE. For example, the method of FIG. 5A may be performed by the UE 102 (see FIG. 4). For example, the method of FIG. 5A may be performed by the processor 1021 upon loading and executing program code from the memory 1022. The method of FIG. 5A generally relates to performing cell reselection among multiple cells of a cellular network based on an LP-RS.

[0050] Optional boxes are shown in dashed lines in FIG. 5A.

[0051] First, in optional box 6005, the UE may indicate to the cellular NW its ability to perform cell reselection based on the LP-RS. This may include, for example, the UE's ability to monitor the LP-RS using the LP-Rx. The UE may indicate whether the UE has the LP-Rx.

[0052] Alternatively or additionally, in box 6005, the cellular NW may indicate to the UE that a broadcasting pattern for the LP-RS (LP-RS broadcasting pattern) is activated.

[0053] In general, any cell of a cellular network can conditionally activate the LP-RS broadcasting pattern. For example, even when the LP-RS broadcasting pattern is activated, the always-on broadcasting pattern of the legacy reference signal can be activated at the same time. Thus, any UE can in principle have the choice of monitoring the legacy reference signal, for example, using the M-Rx, or monitoring the LP-RS, for example, using the LP-Rx.

[0054] Such always-on legacy reference signals may be related to Synchronization Signal (SS) Blocks (SSBs). SSBs include Primary SS (PSS) and Secondary SS (SSS). SSBs are described in 3GPP TS 38.211 v17.0.0. Thus, the always-on broadcasting pattern may be referred to as an SSB broadcasting pattern. Since M-Rx is required, SSBs or PSSs or SSSs may be labeled as high power RSs to delimit against LP-RSs.

[0055] The broadcasting pattern of the LP-RS may specify a timing schedule for the transmission of the LP-RS. Alternatively or additionally, the LP-RS broadcasting pattern may specify a frequency or a frequency range, e.g., a bandwidth portion, over which the LP-RS is transmitted. The broadcasting pattern may specify time-frequency resources of an OFDM resource grid allocated for the transmission of the LP-RS.

[0056] In particular, the UE may receive a control signal from the BS indicating activation of the LP-RS broadcasting pattern. Then, when camped on the BS's cell in idle mode using DRX, the UE may select between monitoring the SSB broadcasted using the SSB broadcasting pattern and monitoring the LP-RS broadcasted using the LP-RS broadcasting pattern.

[0057] Next, some general aspects regarding the LP-RS are disclosed below.

[0058] In general, the LP-RS can be designed to have the same characteristics as the WUS, i.e., to have lower complexity than existing reference and synchronization signals. See, for example, 3GPP TS 36.211 version 17.0.0, e.g., section 6.11B or section 10.2.6B.

[0059] A typical LP-RS has a simple modulation and coding technique, which may be a pseudo-noise (PN) code sequence modulated by on-off keying modulation, and Manchester coding or spreading, for example, and can be decoded by a simple receiver consisting of an envelope detector and a correlator. Both the LP-RS and the WUS can be designed with the above design characteristics.

[0060] The configuration of the WUS may be provided separately from the configuration of the LP-RS.

[0061] WUS opportunities are generally UE specific, while LP-RS are cell specific.

[0062] For example, the LP-RS may include two synchronization signals immediately adjacent to each other in the time domain, i.e., mimicking an SSB structure including a PSS and an SSS.

[0063] The LP-RS may be allocated within the same bandwidth portion (BWP) as the WUS. The BWP for the transmission of the LP-RS and WUS may be part of the initial BWP or may be a BWP dedicated to the LP-RS and WUS transmission. Thus, for example, in response to a wake-up event associated with a given UE, the BS may transmit to that UE a WUS that is also designed for non-coherent decoding, and the WUS and the LP-RS are transmitted in a joint BWP.

[0064] The LP-RS may be transmitted in a different BWP than the SSB, which may be captured by a respective predefined relationship between the LP-RS and SSB broadcasting patterns. The LP-RS may be transmitted in a BWP with a specific numerology, which may be a different numerology than the BWP for the SSB. It is also possible that the SSB and the LP-RS are transmitted on the same frequency, for example in the same BWP or at the same center frequency.

[0065] A BWP is generally defined by a frequency range that is a portion of the entire bandwidth of a carrier. A BWP may be implemented by a contiguous time-frequency resource set selected from a contiguous subset of common time-frequency resources for a given numerology on a given carrier. BWPs are described in 3GPP Technical Specification (TS) 38.211, version 16.4.0, 2021-01-08. That is, different BWPs share the same carrier. In the reference implementation, for a UE, only a single BWP can be active at a time (active BWP). Various techniques are available for switching between BWPs. A particular BWP can be activated by a BWP indicator in DCI format 0_1 ​​(UL grant) and DCI format 0_1 ​​(DL schedule). An inactivity timer can be used. RRC signaling can be used.

[0066] The LP-RS periodicity is configurable and can be configured to have the same periodicity as the SSB periodicity. The LP-RS periodicity can also be an integer multiple of the SSB periodicity. The LP-RS periodicity can also be a fraction of the SSB periodicity. The transmission timing of the LP-RS and SSB is spaced apart by a fixed time distance t d can be offset relative to each other by a time distance t d can be set long enough to accommodate the WUS and the transition time for the primary radio to wake up. With this configuration, both the latency to wake up the device and the UE power consumption are reduced.

[0067] The BS transmits the LP-RS in a specific assigned frequency and time resource such that the LP-RS is detectable by the LP-Rx without causing interference with other OFDM transmissions. To this end, the transmitter may apply techniques such as those disclosed in WO2020 / 074454 to embed the LP-RS in the OFDM transmission to ensure orthogonality to both other OFDM transmissions and reception by the non-coherent LP-Rx. The LP-RS may be accommodated in more than one OFDM symbol as required.

[0068] For simplicity and to avoid additional configuration and design efforts, the LP-RS may carry the same information bits as those carried by the PSS and SSS in the SSB. The LP-RS is cell-specific, i.e., it may encode cell identification information. Thus, the signal shape may vary from cell to cell. Thus, if a UE receives an instance of the LP-RS from a BS of a first cell and another instance of the LP-RS from another BS of a second cell, the UE may be able to associate the received instance of the LP-RS with each of the first cell and the second cell, respectively.

[0069] The UE can then decide, in box 6010, whether to monitor the LP-RS or instead monitor the SSB, which can be based on the capabilities exchange of box 6005. Alternatively or additionally, UE power management considerations can also be taken into account.

[0070] If the UE decides to opt for monitoring the SSB, legacy techniques (including monitoring the SSB and receiving MIBs, SIBs using M-Rx) may be employed.

[0071] If not, the method begins at box 6015 .

[0072] In box 6015, the UE obtains an indication of multiple cells in the cellular network, each of which has a BS broadcasting an LP-RS.

[0073] The multiple cell indication may provide information that a particular cell supports and has activated LP-RS broadcasting. The multiple cell indication may be a list of neighboring cells. In general, such an indication may enable the UE to find a cell to camp on without being required to switch on the M-Rx. The multiple cell indication may have a list, table, rule format, or any other suitable format. For simplicity, this indication is referred to as the LP-RS neighbor cell list in the following, although other formats are possible.

[0074] The LP-RS neighbor cell list may contain cell identity information for each respective cell.

[0075] The LP-RS neighbor cell list may contain information of a group of neighbor cells with one or more criteria, i.e., any cell in the LP-RS neighbor cell list prohibits UEs with LP-Rx, all cells in the LP-RS neighbor cell list support signaling for LP-Rx operation, and / or all cells in the LP-RS neighbor cell list are within the same geographical area.

[0076] For example, the LP-RS neighbor cell list may define a portion or subset of a paging area (PA) used for paging and / or WUS transmissions, and the LP-RS neighbor cell list may also be equal to the PA, i.e., include all cells of the PA. The PA may be referred to as a registration area or a tracking area. The UE may be configured with information regarding time-frequency resources for monitoring WUS and / or paging signals in the PA. The cellular NW may be configured to search for UEs operating in idle mode in the PA. For example, the UE may be configured with information regarding time-frequency resources of wake-up signal opportunities for each cell in the PA. Alternatively or additionally, the UE may be configured with paging opportunities for each cell in the PA. The UE may trigger a PA update when it leaves the PA.

[0077] The UE may be informed about the LP-RS neighbor cell list in different ways depending on the implementation scenario. For example, the LP-RS neighbor cell list may be included in the system information as part of an existing SIB that also contains other information, or as part of a dedicated SIB. In such a scenario, the UE can obtain the LP-RS neighbor cell list even while operating in idle mode by monitoring the respective SIB broadcast. No data connection is required. Alternatively or additionally, the LP-RS neighbor cell list can be included in a connection release message, e.g. an RRC release message, that triggers or performs a transition from connected mode to idle mode by releasing the data link 112 (see Fig. 1).

[0078] At box 6016, along with the LP-RS neighbor cell list, optionally additional information may be obtained.

[0079] For example, a cell-specific transmission configuration of the LP-RS in the cell that is included in the LP-RS may be obtained, which may include sequence information / cell ID, its periodicity, the time and frequency location of the LP-RS, or in general, one or more parameters of the LP-RS broadcasting pattern, etc.

[0080] Alternatively or additionally, a cell-specific transmission configuration of the WUS in a cell included in the LP-RS may be obtained, which may include sequence information / cell ID, its periodicity, time and frequency location of the WUS, or in general one or more parameters of the WUS opportunity, etc. This allows the UE to monitor the WUS when camped on a cell included in the LP-RS neighbor cell list without the need to activate M-Rx to obtain such a cell-specific transmission configuration of the WUS.

[0081] Alternatively or additionally, cell reselection information may be obtained, which may correspond to the cell reselection information in SIB2 to SIB5, for example a variable threshold for triggering cell reselection may be signaled for each cell.

[0082] For example, according to 3GPP TS 38.331 version 16.7.0 (2021-12) "SIB3 information element", it is possible for the cell reselection information to include all or part of the SIB3 information. Intra-frequency channel measurements may be defined. This may be useful if the cells in the LP-RS neighbor cell list all operate in the same frequency band. A minimum required received reference signal received quality (RSRQ) may be indicated. A minimum required reference signal received power (RSRP) level may be indicated. For example, cell offsets may be defined, e.g. with respect to received signal levels. Quality level offsets may be defined. Such information may be useful to calibrate channel measurements in the respective cells, e.g. to determine whether the measured signal levels indicate low or high path loss, strong fading, etc.

[0083] It is possible that a given cell reselection information is valid for all cells in the LP-RS neighbor cell list. In another scenario, different cell reselection information could be provided for at least two cells in the LP-RS neighbor cell list. It is possible to provide respective bitmap data structures in which different entries indicate different cell reselection information for different cells. If two or more cells share the same cell reselection information, this may be adequately represented in a compact manner, for example, by indicating the cell reselection information once in relation to a listing of all applicable cell identities. In other words, generally speaking, it is possible that the cell reselection information includes at least one information element that is valid for (i.e., associated with) two or more of the multiple cells in the LP-RS neighbor cell list. For example, a particular reselection threshold may be applicable to two or more cells, or even all cells, in the LP-RS neighbor cell list, and then the respective information element indicating the reselection threshold is signaled only once.

[0084] In general, the information in box 6015 and the information in box 6016 can be included in a single message, such as a single SIB or a single connection release message. It is also possible for each piece of information to be included in multiple separate messages.

[0085] To limit signaling overhead, common parameter values ​​for cells in the LP-RS neighbor cell list may be signaled only once. For example, if the same time and / or frequency resources are assigned to LP-RS or WUS in multiple cells, such time and / or frequency resources may be indicated once and associated with each cell. Different specific parameter values ​​for each cell in the LP-RS neighbor cell list may be signaled multiple times, i.e., respective values ​​may be provided, for example, in a bitmap structure for each cell in the LP-RS neighbor cell list.

[0086] The UE eventually operates in idle mode in box 6020. Block 6020 may be performed before block 6015, e.g., box 6016 and / or the information in 6016 is included in a SIB that may be obtained while the UE is operating in idle mode.

[0087] Operating in the idle mode may include switching the M-Rx to an inactive state. The data link / data connection is not maintained. While the M-Rx is in the inactive state, DRX may be performed using the LP-Rx. This may include periodically transitioning the LP-Rx between an inactive state and an active state according to an on duration and an off duration of the DRX cycle. During the on duration of the DRX cycle, the UE may monitor the WUS. This may be based on additional information obtained in box 6016. The WUS may be an indication of DL data scheduled for transmission in the cellular NW. Upon receiving the WUS, the UE may transition the M-Rx to an active state. For example, the M-Rx may then monitor a paging signal, such as a paging indicator and a subsequent paging message. Alternatively or additionally, the UE may also perform a random access procedure to set up a data connection to transition to the connected mode.

[0088] The UE may then monitor the LP-RS transmitted by the BS for cells in the LP-RS neighbor cell list (box 6025) while operating in idle mode (box 6020), which facilitates cell reselection.

[0089] From time to time, LP-RS monitoring or LP-RS based cell reselection may be conditionally activated. This is illustrated in relation to optional box 6021. In box 6021, one or more trigger criteria may be checked, such as UE power efficiency requirements, and / or UE mobility level, and / or service requirements of payload data scheduled for UE-to-UE transmission.

[0090] If one or more trigger criteria are met, the method starts at box 6025 where the UE monitors the LP-RS, otherwise, at box 6031, using, for example, a legacy cell reselection procedure, thereby allowing conditional monitoring of the LP-RS.

[0091] Next, details regarding monitoring of the LP-RS are described.

[0092] In box 6025, the UE attempts to receive the LP-RS (monitors the LP-RS). The UE searches for the LP-RS. The UE uses the LP-Rx for this purpose. The M-Rx may be continuously inactive during box 6025. For example, the UE may primarily monitor the LP-RS on the current cell on which the UE is camped, i.e., the serving cell. Only if the UE is unable to receive the LP-RS of the current cell, the UE may perform an attempt to receive the LP-RS in one or more other cells included in the LP-RS neighbor cell list. For example, such monitoring may be based on additional information, such as time and / or frequency resources and / or timing parameters of the LP-RS broadcasting pattern obtained in box 6016.

[0093] The monitoring can be based on time-domain processing of the received baseband waveform.

[0094] Receiving the LP-RS may include time domain processing to detect the waveform in baseband. Receiving the LP-RS may or may not include determining the signal level of the received signal. If the signal level is below a threshold, the received signal may be rejected as meaningless (e.g., related to interference or noise).

[0095] In box 6030, it is determined whether the LP-RS was successfully received.

[0096] Determining whether LP-RS reception is successful may mean that it may be determined whether the LP-RS is found. Optionally, it may be determined whether an LP-RS with a signal level above a certain predefined threshold is received. Determining whether LP-RS reception is successful may be based on one or more such and other criteria. A hardware and / or software level check of the LP-Rx may be performed to determine whether LP-RS reception is successful. In some embodiments, the determination that the LP-RS reception is successful is based on a criterion or rule. In some embodiments, the criterion or rule is implementation dependent. The rule or criterion is based on various aspects such as power efficiency, risk of dropping a connection, etc. In some embodiments, determining whether the LP-RS reception is successful includes the received LP-RS meeting a predefined criterion. In some embodiments, the rule or criterion is at least partially UE implementation dependent.

[0097] If the UE fails to receive the LP-RS (or at least any valid LP-RS from a cell in the LP-RS neighbor cell list), it may activate and follow legacy procedures in box 6031. Here, M-Rx may be transitioned to an active state, and the UE may then monitor the SSB using M-Rx. Upon receiving the SSB, the UE may monitor the MIB and SIB using M-Rx. The UE may then reselect a suitable cell based on the SSB, MIB, and SIB received using M-Rx.

[0098] On the other hand, if in box 6030 it is determined that the LP-RS was successfully received, the method begins in box 6035. In box 6035, a channel measurement is performed based on the received LP-RS. For example, a received signal strength of the LP-RS may be determined. This may reuse the signal level that may be determined in box 6025. An RSRQ and / or an RSRP may be determined. The channel measurement may distinguish between the LP-RS received from different ones of the cells included in the LP-RS neighbor cell list. Again, the channel for the serving cell may be determined first, and only if degradation of the channel of the serving cell is observed, proceed to determining the channel for one or more other cells of the cells included in the LP-RS neighbor cell list. A cell reselection evaluation may be performed.

[0099] It should be noted that although box 6035 and box 6025 are shown as separate boxes, in general, channel measurements may be performed together with box 6025 .

[0100] Then, in box 6040, based on the channel measurements of box 6035, it may be determined whether cell reselection from among the multiple cells should be performed. This may be based on cell reselection evaluation. As part of the cell reselection evaluation, one or more cell reselection criteria may be checked (details will be described in relation to FIG. 5B). In other words, the UE may determine whether the UE may move to one of the multiple cells from which the LP-RS is transmitted. If this is possible, it is typically feasible for power saving reasons.

[0101] Generally, various options are available for cell reselection evaluation. One option is described next, and specific options are also disclosed below in relation to FIG. 5B. For example, the check in box 6040 can include determining the received signal strength of the LP-RS in box 6035 and comparing the received signal strength of the LP-RS of the serving cell with a predefined threshold in box 6040. This corresponds to checking a cell reselection criterion. The predefined threshold can be defined in absolute terms and / or with respect to neighbor cell signal levels. If the determined received signal strength of the LP-RS of the serving cell is above the predefined threshold, reselection may not be performed, whereas if the determined received signal strength of the LP-RS of the serving cell is below the predefined threshold, for example for a certain duration, cell reselection may be performed. The received signal strength of one or more other cells included in the LP-RS neighbor cell list can be evaluated and then in box 6040 the strongest cell can be selected to camp on. This corresponds to the cell reselection criterion. The one or more parameters specified by the cell reselection information may be considered to have been obtained, for example, as part of box 6016. In general, the cell reselection information may parameterize or specify one or more cell reselection criteria.

[0102] Generally, the decision-making in box 6040 can vary according to the scenario. Exemplary detailed implementation forms of the decision-making are disclosed below. For example, when the signal strength (γ) of the LP-RS in the serving cell is sufficient, that is, γ > l1, exceeding a specific level (specified by the cell reselection information of that cell), the UE continues to camp on the cell. This can be determined based on the secondary synchronization signal included in the LP-RS (without considering the primary synchronization signal included in the LP-RS). When the signal strength of the LP-RS of the serving cell does not meet the measurement criteria, that is, l2 < γ < l1, the UE monitors the LP-RS of the neighbor cells. Here, the UE can receive and evaluate both the primary synchronization signal and the secondary synchronization signal included in the LP-RS if available. As soon as the signal strength of the serving cell becomes weak, that is, γ < l2, falling below a specific level, the UE can no longer camp on that cell. The UE then needs to perform cell search on the LP-RS of the cells in the LP-RS neighbor cell list to find a cell suitable for camping. If the UE moves outside the coverage area defined by the cells included in the LP-RS neighbor cell list where all measurements based on the LP-RS are shown to be below the threshold (l2), the UE fails to receive such LP-RS from the cells in the LP-RS neighbor cell list (see box 6030), and the UE activates M-Rx to perform cell reselection using legacy methods. For example, FIG. 6 shows the signal strength 881 measured in the LP-RS of the serving cell over time and the respective thresholds 882. Also shown is the signal strength 885 of the LP-RS broadcast by the neighboring cells over time, which tends to increase.

[0103] 5A, if cell reselection is not performed, the method starts at box 6020, i.e., the UE continues to operate in idle mode and camp on the serving cell. Otherwise, the method starts at box 6050, where cell reselection is performed. The UE may then camp on the reselected cell without the need for a MIB or SIB. More specifically, based on additional information obtained, for example, at box 6016, the UE may assume that the UE is not barred and satisfies the reselection requirements according to such cell reselection information.

[0104] In summary, the method of FIG. 5A allows the UE to move within cells included in the LP-RS neighbor cell list by evaluating only the LP-RS of the neighbor cell. While camped on the cell, the UE needs to monitor the WUS using the LP-Rx. When performing cell reselection, as long as the UE can camp on one of the cells listed in the LP-RS neighbor cell list, the UE does not need to receive any information related to SIB1-SIB5, making it unnecessary to power up the M-Rx to its active state. The M-Rx can be operated continuously in its inactive state until after performing cell reselection, e.g., until it receives the WUS. This is due to the fact that the LP-RS is sufficient for cell reselection evaluation and cell reselection procedures. The advantage of this approach is that the UE does not need to read the MIB / SIB when moving to a new cell.

[0105] Note that in some scenarios, the order of the boxes in Figure 5A may change: for example, it is possible to perform channel measurements together with monitoring the LP-RS, i.e., in a single process.

[0106] Figure 5B is a flow chart illustrating a particular implementation of boxes 6025, 6030, 6035, and 6040 of Figure 5A. Figure 5B illustrates aspects relating to cell reselection evaluation.

[0107] In box 6705, the UE first selectively attempts to receive the LP-RS transmitted by the BS of the serving cell. A respective filter may be used. In other words, the UE may search for the LP-RS transmitted by the BS of the serving cell. The UE may monitor a specific resource. Thus, box 6710 corresponds to evaluating whether the serving cell is detected and strong enough for the UE to be allowed to camp on the cell. Thus, box 6705 corresponds to box 6025.

[0108] The UE then determines whether the UE was able to receive the LP-RS of the serving cell in box 6710. This may include determining whether the respective signal levels are above a threshold, which corresponds to box 6030.

[0109] If a LP-RS related to the serving cell is received, the UE performs channel measurement based on this LP-RS of the serving cell in box 6715. The RSRQ and / or RSRP may be determined. This corresponds to box 6035.

[0110] Box 6715 may be implemented as part of box 6705.

[0111] Then, in box 6720, each quantity of channel measurements can be compared with a certain threshold. This implements the Tier 1 cell reselection criteria. This is part of the cell reselection evaluation. For example, it can be checked whether the RSRQ and / or RSRP is better than a certain fixed value / threshold. If the threshold comparison yields a positive result (i.e., the serving cell is strong enough), no cell reselection is required, which corresponds to the No branch of box 6040.

[0112] In box 6725, triggered by the inability to receive the LP-RS from the serving cell (box 6710), the UE attempts to receive the LP-RS from the neighboring cells according to the LP-RS cell list, which also corresponds to box 6025. If the UE is not successful in box 6725 (a respective check is performed in box 6728), a fallback to monitoring the SSB is performed, which corresponds to box 6031. Otherwise, the UE performs channel measurements for the received LP-RS in box 6735 (corresponding to box 6035).

[0113] Also, if it is determined in box 6720 that the LP-RS of the serving cell is not good enough (e.g., RSRQ and / or RSRP below a threshold), the UE attempts to receive the LP-RS from a neighboring cell according to the LP-RS cell list in box 6726. Thus, box 6726 corresponds to box 6725. In box 6727, a check is performed whether the LP-RS has been received (which thus corresponds to box 6728). If yes, box 6735 is performed and channel measurements are performed.

[0114] In box 6735, the UE determines whether the cell from which the LP-RS was received is above a certain predefined threshold, and if not, a fallback to SSB monitoring in box 6031 is performed. The threshold in box 6735 may be different (i.e., lower) than the threshold in box 6720.

[0115] Box 6735 may be performed in conjunction with box 6726 or box 6725, respectively.

[0116] For example, RSRP and / or RSRQ may be compared to respective thresholds in both box 6720 and box 6735. The RSRP and / or RSRQ threshold in box 6720 may be higher than the RSRP and / or RSRQ threshold in box 6735.

[0117] If the threshold comparison in box 6735 is successful (i.e., at least one sufficiently strong cell), it is determined in box 6740 whether cell reselection should be performed in box 6050 or whether to continue camping on the serving cell.

[0118] Different implementations are possible for box 6740. For example, if box 6715 is performed, the RSRP and / or RSRQ of the neighboring cell (as determined in box 6735) may be determined against a threshold that depends on the RSRP and / or RSRQ of the serving cell determined from box 6715. In other cases, a fixed threshold may be used. Alternatively, a threshold based on the last measured RSRP and / or RSRQ of the serving cell may be used. All these options described above implement the Tier 2 cell reselection criteria.

[0119] Figure 5C is a flow chart illustrating a particular implementation of boxes 6025, 6030, 6035, and 6040 of Figure 5A. Figure 5C illustrates an aspect relating to cell reselection evaluation.

[0120] Figure 5C generally corresponds to Figure 5B, however, in Figure 5C channel measurements are performed in conjunction with searching for the LP-RS from either the serving cell in box 6805 (corresponding to boxes 6705 and 6715) or a neighboring cell in box 6815 (corresponding to boxes 6725, 6726, 6735).

[0121] Also, in box 6810 for the serving cell (corresponding to boxes 6710, 6720) and box 6820 (corresponding to boxes 6728, 6727, 6735), a check is combined between successful reception and whether a minimum threshold is met. The threshold in box 6820 may be different (i.e., lower) than the threshold in box 6810.

[0122] The reselection evaluation in box 6825 corresponds to box 6740.

[0123] The combination of LP-RS searching and channel measurements as shown in FIG. 5C is generally an option available for all scenarios disclosed herein.

[0124] As can be seen from Figures 5A, 5B, and 5C, generally, if an LP-RS is received from at least one cell, it is possible to perform a cell reselection evaluation based on the LP-RS. Based on the received LP-RS, one or more reselection criteria may be evaluated. Reselection may or may not actually be performed depending on whether the one or more cell reselection criteria are satisfied. The one or more cell reselection criteria may be signaled by the network, for example, using cell reselection information.

[0125] FIG. 7 is a flowchart of a method, according to various examples. The method of FIG. 7 may be performed by a BS associated with a cell of a cellular network. For example, the method of FIG. 7 may be performed by the BS 101 (see FIG. 3). For example, the method of FIG. 7 may be performed by the processor 1011 upon loading and executing program code from the memory 1012. The method of FIG. 7 generally relates to control signaling by one or more UEs to facilitate cell reselection by the one or more UEs based on the LP-RS.

[0126] Optional boxes are shown in dashed lines in FIG.

[0127] In optional box 6105, information is exchanged between the BS and one or more further BSs of the cellular network. For example, the information may be provided to the one or more BSs or may be obtained from one or more further BSs. Based on such information, it is possible to determine an LP-RS neighbor cell list. For example, it is possible to determine which reselection configuration parameters and / or WUS parameters and / or LP-RS broadcasting pattern parameters include similar values ​​for various cells. For example, it is possible to determine which cells should be grouped in an LP-RS neighbor cell list, for example based on coverage area considerations and / or based on capability considerations. For example, such cells may be included in an LP-RS neighbor cell list that have the same cell reselection information and / or the same WUS opportunity timing and / or the same LP-RS broadcasting pattern.

[0128] If the BSs exchange information, it is possible to determine the LP-RS neighbor list, which is included in the radio access network (RAN), which can be useful for an RRC inactive mode that is transparent to the core network.

[0129] Alternatively or in addition to exchanging such information between multiple cells, at least a part of the information may be obtained from the core network, for example from a mobility control node of the core network. An exemplary mobility control node is the 3GPP NR Access and Mobility Function (AMF).

[0130] In some scenarios, it is possible that the LP-RS neighbor cell list is obtained from a core network mobility control node of the cellular network.

[0131] It is also possible that the LP-RS neighbor cell list is predetermined, for example, fixedly configured.

[0132] At box 6110, capabilities for activating the LP-RS broadcasting pattern may be exchanged between the BS and the UE. Box 6110 corresponds to box 6005 of the method of FIG. 5A.

[0133] In some scenarios, the LP-RS broadcasting pattern may then be conditionally activated in box 6115. Sometimes, the LP-RS broadcasting pattern is activated only if there is a minimum count of UEs camped on the respective cell that supports monitoring of the LP-RS, to name just one example.

[0134] The LP-RS broadcasting pattern is activated simultaneously with the SSB broadcasting pattern.

[0135] The LP-RS broadcasting pattern is activated and the BS repeatedly broadcasts the LP-RS, which enables cell reselection in the UE among cells included in the LP-RS neighbor list.

[0136] In box 6125, the BS can provide the UE with an indication of the cells that each broadcast the LP-RS. In other words, the LP-RS neighbor cell list can be provided to the UE. Such information can be broadcast or transmitted in a directed message, such as an RRC control message. A connection release message can be used to provide the LP-RS neighbor cell list. A SIB can be used.

[0137] Box 6125 corresponds to box 6015 of the method of FIG. 5A.

[0138] Additional information related to the LP-RS neighbor cell list may be provided to one or more UEs at box 6126. Box 6126 corresponds to box 6016 of the method of FIG.

[0139] Box 6125 and box 6126 may be implemented together, that is, the information for each is included in a single message.

[0140] In box 6130, it may be checked whether SL data is scheduled for transmission to the UE. If yes, in box 6135, a WUS may be transmitted, the WUS being associated with the UE. For example, the WUS may be transmitted during the on duration of the DRX cycle associated with the UE. Information regarding downlink data scheduled for transmission to the UE may be obtained from a mobility control node of the cellular NW.

[0141] FIG. 8 is a signaling diagram of communication between a BS 101 and a UE 102, as well as a further BS 105 located in the vicinity of the BS 101 and associated with another cell of the cellular network.

[0142] In the scenario of FIG. 8, the UE 102 continues to operate in idle mode.

[0143] For example, the signaling of FIG. 8 may implement the method of FIG. 5A in the method of FIG.

[0144] At 5002, configuration information is optionally exchanged between BS101 and BS105. Based on such configuration information, BS101 and / or BS105 may determine an LP-RS neighbor cell list.

[0145] For example, in a cell associated with BS101 and in a cell associated with BS105, information on whether the respective LP-RS broadcasting patterns are activated may be exchanged. Information on time and / or frequency resources used for LP-RS transmission may be exchanged. It may be determined whether the WUS opportunities match or are even the same. It may be determined whether BS101, 105 provide carriers in the same frequency range or at the same frequency.

[0146] Based on such and other considerations, it may be determined whether the cells associated with BS101 and BS105 should be grouped in a common LP-RS neighbor cell list.

[0147] The signaling in 5002 is generally optional. For example, in some scenarios, the LP-RS neighbor list may be pre-determined. It is also possible that the BS 101 obtains the LP-RS neighbor list from a mobility control node of the core network. In another scenario, such configuration may also be implemented by an operation and maintenance interface during the deployment phase.

[0148] At 5005, the UE 102, while operating in an idle mode, performs cell reselection to a cell associated with the BS 101. For example, the cell reselection may be based on monitoring the SSBs, including the PSS and the SSS.

[0149] The UE 102 may then receive 5010 the MIB 4005 and, at 5015, one or more SIBs 4006 broadcast by the BS 101.

[0150] One or more of the SIBs indicate the LP-RS neighbor cell list 4098 and, optionally, additional information 4099, as previously described in relation to boxes 6015 and 6016, respectively (see FIG. 5A), and boxes 6125 and 6126, respectively (see FIG. 7). The additional information 4099 may relate to a WUS configuration for each cell in the LP-RS neighbor cell list 4098 and / or a cell reselection information configuration for each cell in the LP-RS neighbor cell list 4098.

[0151] In box 5020, the UE 102 then determines that the LP-RS broadcasting pattern is activated and that cell reselection based on LP-RS monitoring is supported, based on the information obtained in 5015.

[0152] Thus, in box 5025, the UE monitors the LP-RS broadcast by BS101 and BS105 since their respective cell identities are both listed in the LP-RS neighbor cell list 4098. The UE is said to be searching for the LP-RS.

[0153] UE 102 receives LP-RS 4010 broadcast by BS 101 at 5030 and receives LP-RS 4010 broadcast by BS 105 at 5040 (see box 6025 in FIG. 5A ). UE 102 can perform channel measurements based on LP-RS 4010 broadcast by BS 101 and LP-RS 4010 broadcast by BS 105, respectively.

[0154] At 5035, the UE 102 also monitors the WUS 4015 at each WUS opportunity. In the illustrated scenario, the BS 101 does not transmit the WUS 4015 (e.g., there is no DL data scheduled for transmission to the UE 102).

[0155] At 5045, the UE 102 determines to continue camping on the cell associated with BS 101. No cell reselection is performed to the cell associated with BS 105 (see box 6040 of FIG. 5A). For example, the signal strength of the LP-RS 4010 transmitted by BS 101 may be above a certain threshold and / or may be greater than the signal strength of the LP-RS 4010 broadcast by BS 105, each aspect of which was disclosed above in connection with FIG. 6.

[0156] After a certain duration, e.g., the next on duration of a DRX cycle, the UE 102 may again monitor the LP-RS 4010 broadcast by the BS 101 and BS 105 at 5050 and 5060. The UE may also again monitor the WUS 4015 at 5055.

[0157] The UE monitors the LP-RS 4010 when the LP-Rx is in the active state.

[0158] At 5065, cell reselection is performed from the cell associated with BS 101 to the cell associated with BS 105. The decision may be made at the UE 102 based on the signal level of the LP-RS 4010 broadcast by BS 101 and the signal level of the LP-RS broadcast by BS 105, respectively. Details regarding cell reselection were disclosed above in connection with box 6040 of the method of FIG. 5A. M-Rx is not required for any of 5030, 5035, 5040, 5050, 5055, and 5060.

[0159] Upon performing cell reselection, the UE 102 continues to operate in idle mode. At 5070 and 5075, the UE 102 then monitors, for example, the LP-RS broadcast by BS 101 and the new serving BS 105 (and possibly further neighboring cells), respectively. The UE monitors 5080 the WUS 4015 of the new serving cell associated with BS 105. The UE may use the respective WUS configuration included in the information 4099.

[0160] FIG. 9 is a signaling diagram of communication between a BS 101 and a UE 102, as well as a further BS 105 located in the vicinity of the BS 101 and associated with another cell of the cellular network.

[0161] In the scenario of FIG. 9, the UE initially operates in a connected mode (different from the scenario of FIG. 8).

[0162] For example, the signaling of FIG. 9 may implement the method of FIG. 5A and the method of FIG.

[0163] The signaling of Figure 9 generally corresponds to that of Figure 8. However, it differs in that the LP-RS neighbor cell list, and optionally related information 4099, is included in the RRC release message sent by BS 101 to UE 102, thereby triggering a transition of UE 102 from operating in a connected mode in box 5105 to operating in an idle mode in box 5125.

[0164] Other than this, 5120 corresponds to 5002, 5115 corresponds to 5020, 5130 corresponds to 5025, 5135 corresponds to 5030, 5140 corresponds to 5035, 5445 corresponds to 5040, 5150 corresponds to 5045, 5155 corresponds to 5050, 5160 corresponds to 5055, 5165 corresponds to 5060, 5170 corresponds to 5065, 5175 corresponds to 5070, 54180 corresponds to 5075, and 5185 corresponds to 5080.

[0165] In summary, a low power mechanism to support cell reselection and mobility for UEs with LP-RX has been disclosed.

[0166] The UE may be configured to perform cell reselection monitoring using the LP-RX upon release to idle mode via RRC signaling. Alternatively, the information is provided in the SIB.

[0167] Such neighbor cell information includes information that enables the UE to measure and reselect to neighbor cells using LP-Rx, and to monitor / measure LP-RS in the serving cell and, when necessary, in neighbor cells.

[0168] The UE does not need to use M-Rx to perform cell reselection.

[0169] Also, information on whether a cell is suitable and not barred can be found via the LP-RS in the cell or via system information in the last serving cell, indicating the barring status of the set of neighbor cells that are indicated as available for LP cell reselection.

[0170] While the present invention has been shown and described with respect to specific preferred embodiments, equivalents and modifications will occur to those skilled in the art upon reading and understanding this specification. The present invention includes all such equivalents and modifications, and is limited only by the scope of the appended claims.

Claims

1. A method of operating a wireless communication device (102) in a cellular network including a number of cells, each cell of the number of cells broadcasting a cell-specific high power reference signal, the method comprising: - obtaining (6015) from said cellular network an indication of a number of cells (871-874) of said plurality of cells (871-874), said base stations (101, 105) of said plurality of cells each broadcasting a cell-specific low power reference signal (4010); - monitoring (6025) said cell-specific low power reference signal (4010) while operating in idle mode; - performing (6050) a cell reselection among said plurality of cells based on said cell-specific low power reference signal (4010) upon successful reception of said cell-specific low power reference signal (4010) from at least one base station (101, 105) of at least one of said plurality of cells; - upon failure to receive said cell-specific low power reference signal, monitoring (6031) said cell-specific high power reference signal for performing said cell reselection; A method comprising:

2. - acquiring (6016) cell-specific transmission configurations of said cell-specific low power reference signals (4010) for said plurality of cells (871-874) from said cellular network, said monitoring said cell-specific low power reference signal (4010) is in accordance with said cell-specific transmission configuration. The method of claim 1.

3. - Obtaining (6016) cell-specific transmission configurations (4099) of wake-up signals (4015) for said plurality of cells (871-874) from said cellular network; - monitoring said wake-up signal (4015) according to said cell specific transmission configuration while operating in said idle mode, The method according to claim 1 or 2.

4. - acquiring (6016) cell reselection information (4099) from the cellular network for the plurality of cells (871-874) and related to the cell-specific low power reference signal (4010); the cell reselection is performed according to the cell reselection information. The method according to any one of claims 1 to 3.

5. the cell reselection information includes at least one information element valid for two or more of the plurality of cells. The method according to claim 4.

6. the cell reselection information specifies one or more cell reselection criteria to be evaluated at the wireless communication device before performing the cell reselection. The method according to claim 4 or 5.

7. the indication (4098) of the plurality of cells (871-874) is broadcast in a system information block (4006) by the base station (101) of each cell (871-874) of the plurality of cells (871-874); The method according to any one of claims 1 to 6.

8. the indication (4098) of the plurality of cells (871-874) is included in a connection release message (4100) that triggers the operation in the idle mode; The method according to any one of claims 1 to 7.

9. - controlling a low power receiver of said wireless communication device (102) to perform said monitoring of said cell specific low power signals; - controlling a primary receiver of said wireless communication device to perform said monitoring of said cell-specific high power reference signal; The method of any one of claims 1 to 8, further comprising:

10. - continuing to operate the primary receiver in an inactive state while monitoring the cell-specific low power reference signal and until after the cell reselection has been performed (6050); The method of claim 9 further comprising:

11. said monitoring said cell-specific low power reference signal includes performing time domain processing of a baseband waveform. The method according to any one of claims 1 to 10.

12. the cell reselection is selectively performed based on the cell-specific reference signal if one or more trigger criteria are met; If the one or more trigger criteria are not met, the monitoring of the cell-specific high power reference signal is performed to perform the cell reselection. The method according to any one of claims 1 to 11.

13. the one or more trigger criteria include at least one of a power efficiency requirement, a level mobility of the wireless communication device, or a service requirement of a service related to payload data scheduled for transmission; The method of claim 12.

14. - upon successful reception of said cell-specific low power reference signal (4010) from at least one base station (101, 105) of at least one of said plurality of cells, evaluating based on said cell-specific low power reference signal (4010) whether one or more cell reselection criteria are fulfilled, The cell reselection is selectively performed if the one or more cell reselection criteria are satisfied. The method according to any one of claims 1 to 13.

15. - monitoring the cell-specific high power reference signal for performing the cell reselection upon successful reception of the cell-specific low power reference signal (4010) from the at least one base station of the at least one of the plurality of cells and if a signal level or signal quality of the cell-specific low power reference signal falls below a predefined threshold. The method of any one of claims 1 to 14, further comprising:

16. A method of operating a base station (101) associated with a cell (871-874) of a number of cells (871-874) of a cellular network, each cell of the number of cells broadcasting a cell-specific high power reference signal, the method comprising: providing (6125) to the wireless communication device (102) an indication of a number of cells (871-874) of said plurality of cells, and base stations (101, 105) of said plurality of cells each broadcasting a cell-specific low power reference signal (4010) enabling cell reselection between said plurality of cells in said wireless communication device; - broadcasting (6115) said low power reference signal (4010); A method comprising:

17. determining said indication of said plurality of cells based on information exchanged between said base station and one or more further base stations of said cellular network; 20. The method of claim 16, further comprising:

18. obtaining said indication of said plurality of cells from a core mobility control node of said cellular network; 20. The method of claim 17, further comprising:

19. the plurality of cells (871-874) forming part of a tracking area associated with the wireless communication device (102); The method according to any one of claims 16 to 18.

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