Wireless communication device, access node and operation method

Abstract

The present application relates to wireless communication devices, access nodes and operation methods. A method of operating a wireless communication device (101) comprises: when operating in a connected mode (301), before switching (309) to a disconnected mode (302, 303): receiving at least one downlink message (4021, 4011) from a communication network (100), the downlink message comprising configuration information indicating at least one configuration of occasionally starting transmission (900) of a reference signal (901, 4001). The method further comprises: when operating in the disconnected mode (302, 303) according to a discontinuous reception cycle (390): monitoring a reference signal (901, 4001) occasionally transmitted by the communication network (100) according to at least one configuration. The reference signal (901, 400) is adapted to maintain synchronization with the communication network (100) in another communication during an on period (396) of the discontinuous reception cycle.

Description

Technical Field

[0001] Various examples generally relate to sleep mode operation of a wireless communication device. Various examples specifically relate to transmission of a reference signal when the wireless communication device operates in a disconnected mode. Background Art

[0002] There is a need to reduce the power consumption of a wireless communication device (UE). One strategy to reduce the power consumption of a UE is to operate the UE in a disconnected mode. As a general rule, the disconnected mode provides limited connectivity compared to the connected mode, but can reduce power consumption. This is because the data connection is deactivated at least along the radio link between the UE and the communication network. The disconnected mode may then include paging operations and / or random access accesses to reestablish the data connection. For example, in the context of the Third Generation Partnership Project (3GPP), example implementations of the disconnected mode include a radio resource control (RRC) idle mode and an RRC inactive mode.

[0003] As a general rule, when operating in disconnected mode, the UE may expect transmissions from the communication network to be limited to the on period of a discontinuous reception (DRX) cycle; therefore, during the off period of the DRX cycle, the UE may transition certain parts of its radio interface to an inactive state (sometimes also referred to as a sleep state). For example, more parts of the analog front end and / or digital front end and / or other parts may be turned off. This helps reduce power consumption.

[0004] In order to be able to receive data during the on-duration of the DRX cycle, typically the radio interface is (re)transferred to the active state some time before the on-period begins. This is because the transition from the inactive state to the active state takes some time and, moreover, typically requires resynchronization with the timing reference of the communication network and / or otherwise adjusting the radio interface to be able to receive data.

[0005] To resynchronize (ie, maintain synchronization during another transmission), the UE may monitor a Reference Signal (RS) transmitted by the communication network when attempting to transition the radio interface to an active state.

[0006] It has been found that the process of monitoring RS is sometimes rather inefficient as it requires a significant amount of time and consumes a significant amount of power. Summary of the invention

[0007] Therefore, there is a need for advanced techniques for operating a UE in disconnected mode using a DRX cycle. In particular, there is a need for advanced techniques for reacquiring synchronization with a communication network before an on period of a DRX cycle.

[0008] According to the techniques described herein, a UE operating in disconnected mode may be configured to occasionally turn on transmission. Then, when operating in disconnected mode, the UE may monitor the RS (reference signal) for occasional transmission. For example, the monitoring may be based on a DRX cycle. Alternatively or additionally, the UE may monitor the RS for occasional turn-on transmission before or at the start of a paging occasion for a paging operation associated with the disconnected mode.

[0009] A method for operating a UE includes receiving at least one downlink message. At least one downlink message is received from a communication network. Before switching to disconnected mode, when the UE is operating in connected mode, at least one downlink message is received. At least one downlink message includes configuration information. The configuration information indicates at least one configuration of transmission of an RS that is occasionally turned on. The method also includes monitoring an RS that is occasionally transmitted by a communication network (NW) according to at least one configuration of occasionally turning on transmission. The UE monitors the RS when operating in disconnected mode according to a discontinuous reception cycle. The RS is adapted to be synchronized with the communication network in another communication during the on period of the DRX cycle.

[0010] A computer program or a computer program product or a computer-readable storage medium includes a program code. The program code can be executed by at least one processor. Executing the program code causes the at least one processor to perform a method for operating a UE. The method includes receiving at least one downlink message. At least one downlink message is received from a communication network. Before switching to disconnected mode, when the UE is operating in connected mode, at least one downlink message is received. At least one downlink message includes configuration information. The configuration information indicates at least one configuration of transmission of an RS that is occasionally turned on. The method also includes monitoring an RS that is occasionally transmitted by a communication NW according to at least one configuration of occasionally turning on transmission. The UE monitors the RS when operating in disconnected mode according to a discontinuous reception cycle. The RS is adapted to be synchronized with the communication network in another communication during the on period of the DRX cycle.

[0011] The UE includes a control circuit. The control circuit is configured to receive at least one downlink message from a communication network when operating in a connected mode before switching to a disconnected mode. The at least one downlink message includes configuration information indicating at least one configuration of occasional on-transmission of a reference signal. The control circuit is further configured to monitor RSs occasionally transmitted by the communication network according to the at least one configuration when operating in the disconnected mode according to a discontinuous reception cycle. The RSs are adapted to be synchronized with the communication network in another communication during an on period of a DRX cycle.

[0012] A method of operating an access node of a communication network includes sending at least one downlink message to a UE operating in a connected mode. The at least one downlink message includes configuration information indicating at least one configuration of transmission of an occasionally turned-on RS. The method also includes performing transmission of the occasionally turned-on RS when the UE operates in a disconnected mode using a DRX cycle. The RS is adapted to maintain synchronization with the communication network in another communication during an on period of a discontinuous reception cycle.

[0013] The computer program or computer program product or computer readable storage medium includes program code. The program code can be executed by at least one processor. Executing the program code causes the at least one processor to perform a method for operating an access node. The method includes sending at least one downlink message to a UE operating in a connected mode. The at least one downlink message includes configuration information indicating at least one configuration of transmission of an occasionally turned-on RS. The method also includes performing transmission of an occasionally turned-on RS when the UE operates in a disconnected mode using a DRX cycle. The RS is adapted to maintain synchronization with a communication network in another communication during an on period of a discontinuous reception cycle.

[0014] An access node of a communication network includes a control circuit. The control circuit is configured to send at least one downlink message to a UE operating in a connected mode. The at least one downlink message includes configuration information indicating at least one configuration of transmission of an occasionally turned-on RS. The control circuit is also configured to perform transmission of the occasionally turned-on RS when the UE operates in a disconnected mode using a DRX cycle.

[0015] The system includes an access node and a UE as described above. The system may also include one or more core network nodes, for example, to configure transmission of a paging signal in a paging operation in a paging occasion aligned with a DRX cycle.

[0016] It is to be understood that the features mentioned above and those yet to be explained below can be used not only in the respective combination indicated but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A cellular communication network according to various examples is schematically illustrated.

[0018] Figure 2 A number of modes in which a UE connectable to a cellular communication network may operate are schematically illustrated according to various examples.

[0019] Figure 3 Various aspects regarding a DRX cycle that a UE may use when operating in disconnected mode are schematically illustrated according to various examples.

[0020] Figure 4 A base station according to various examples is schematically illustrated.

[0021] Figure 5 A UE according to various examples is schematically illustrated.

[0022] Figure 6 is a flow chart of a method according to various examples.

[0023] Figure 7 is a flow chart of a method according to various examples.

[0024] Figure 8 is a flow chart of a method according to various examples.

[0025] Fig. 9 is a signaling diagram of communications between a base station and multiple UEs according to various examples.

[0026] Fig.10 An always-on transmission of a reference signal according to various examples is schematically illustrated. DETAILED DESCRIPTION

[0027] Some examples of the present disclosure generally provide multiple circuits or other electrical devices. All references to circuits and other electrical devices and the functions provided by each device are not intended to be limited to only the contents illustrated and described herein. Although specific labels can be assigned to the various circuits or other electrical devices disclosed, these labels are not intended to limit the operating range of circuits and other electrical devices. Such circuits and other electrical devices can be combined and / or separated from each other in any way based on the desired specific type of electrical implementation. It should be recognized that any circuit or other electrical device disclosed herein may include any number of microcontrollers, graphics processor units (GPUs), integrated circuits, storage devices (e.g., flash memory, random access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM) or other suitable variants), and software that cooperates with each other to perform the operations disclosed herein. In addition, any one or more electrical devices may be configured to execute a program code contained in a non-temporary computer-readable medium, which is programmed to perform any number of functions disclosed.

[0028] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the following description of the embodiments should not be understood as limiting. The scope of the present invention is not intended to be limited by the embodiments or drawings described below, which are considered to be illustrative only.

[0029] The drawings should be considered as schematic representations, and the elements shown in the drawings need not be shown to scale. Instead, the various elements are represented so that their functions and general purposes become apparent to those skilled in the art. Any connection or coupling between the functional blocks, devices, components or other physical or functional units shown in the drawings or described herein may also be achieved by indirect connections or couplings. Couplings between components may also be established by wireless connections. Functional blocks may be implemented with hardware, firmware, software or a combination thereof.

[0030] Various aspects relate to a communication system. For example, the communication system may be implemented by a UE and an access node of a communication network (NW). For example, the access node may be implemented by a base station (BS) of a cellular communication NW (hereinafter referred to as cellular NW). In the following, for simplicity, various examples will be described in conjunction with a communication system implemented by a UE that can be connected to a cellular NW. However, similar techniques can be easily used for other kinds and types of communication systems.

[0031] The communication system may include a wireless link between a UE and a BS. A downlink (DL) signal may be sent by the BS and received by the UE. An uplink (UL) signal may be sent by the UE and received by the BS.

[0032] In the following, a technique for facilitating the operation of a UE in disconnected mode will be described. The disconnected mode may limit connectivity, for example, in terms of when the UE can receive data and / or what signal the UE can receive. The disconnected mode may generally enable the UE to partially or completely shut down one or more components of its wireless interface. When the UE is operating in disconnected mode, the cellular NW may discard certain information associated with the UE, such as certain information of the UE context, etc. The UE-specific data connection between the cellular NW and the UE on the wireless link may be released; on the other hand, a portion of the data connection may remain in the core of the communication NW. As a general rule, a UE operating in disconnected mode may use a DRX cycle, i.e., iteratively switching the wireless interface between an active state and an inactive state (sometimes referred to as a sleep state). When in an inactive state, the wireless interface may not be suitable for receiving data. When switching from an inactive state to an active state, the UE may monitor RS. The UE may also monitor another transmission, for example, a paging signal. As a general rule, the disconnected mode may be associated with a paging operation. Here, one or more paging signals are sent to the UE by the communication NW at a paging occasion (PO). The PO may be aligned in time with the on period of the DRX cycle.

[0033] In order to receive the paging signal, the UE may need to synchronize with the communication NW. In order to maintain synchronization, the UE may receive the RS.

[0034] The RS typically represents a signal with well-defined transmit properties (e.g., amplitude, phase, symbol sequence and / or precoding, etc.), which is also known to the receiver. Based on the receive (RX) properties of the RS (e.g., based on the receive amplitude or receive phase of the RS), one or more properties of the wireless interface can then be adjusted. For example, a radio frequency oscillator can be tuned. The RS is adapted / configured to keep in sync with the communication NW. One or more channels (e.g., belonging to different spatial streams) can be played on the wireless link.

[0035] The UE may then attempt to demodulate another transmission from the communication NW based on the RX properties of the RS. For example, the UE may attempt to demodulate another transmission during or before the on period of the DRX cycle. Alternatively or additionally, the UE may modulate another transmission to the communication NW based on the RX properties of the RS. Thus, as a general rule, the RS may be adapted to maintain synchronization in another communication between the UE and the NW.

[0036] The other transmission may include UE-originated UL data, such as at least one of a UE mobility indicator, a random access preamble of a random access procedure for establishing a data connection, or an activity indicator.

[0037] Another transmission may include DL data, such as a system information block, a paging signal, a paging area update, etc.

[0038] In the following, techniques are described that facilitate efficient synchronization with a cellular NW (eg, low latency and / or energy efficient and / or low overhead synchronization). Efficient synchronization may be obtained through an appropriate DL RS transmission strategy.

[0039] For example, a UE operating in disconnected mode can utilize RS that is already available (e.g., for one or more other UEs that can operate in connected mode). In other words, it will be possible to utilize transmissions of RS configured for the UE and at least one other UE. Thus, spectrum utilization can be increased. For example, at least one other UE can be in connected mode.

[0040] For example, a UE-specific RS may be used for a UE operating in an idle mode. Such a UE-specific RS may be configured by the cellular NW when the corresponding UE registers with the cellular NW. In this way, such a UE-specific RS may not always be activated, but may be activated on demand for the corresponding UE. When a given one of the multiple UEs enters, for example, a connected mode, it is usually possible for multiple UEs to share such an on-demand activated RS.

[0041] For example, the transmission of RS that is occasionally turned on can be used. That is, the transmission of RS that is not always turned on can be relied upon. This means that the UE will not assume that there is an RS on the wireless link unless the UE is configured to occasionally turn on the transmission and the UE receives corresponding signaling from the cellular NW (in contrast to always turning on the transmission). The transmission of RS that is occasionally turned on can be configured on demand by the cellular NW. The transmission of RS that is occasionally turned on can be activated by the cellular NW and then deactivated again. Therefore, there may be no indication of occasionally turning on the transmission in the broadcast information block. The transmission of RS that is occasionally turned on can use the time-frequency resources in the time-frequency resource grid that is specially allocated when the occasionally turned on transmission is configured. The corresponding configuration can indicate such time-frequency resources. This may be different from always-on transmission, where each re-occurring resource can be statically allocated, for example, in certain reserved parts of the subframe of the transmission protocol used for communication on the wireless link.

[0042] As a general rule, the RS that occasionally turns on transmission may indicate the cell identity of the cell of the cellular NW. The RS that occasionally turns on transmission may be sequence-based. For example, a symbol sequence such as a Zadoff-Chu sequence or a maximum length sequence may be used. Scrambling and / or interleaving may be requested. The RS that occasionally turns on transmission may be mapped to multiple subcarriers within an orthogonal frequency division multiplexing (OFDM) symbol.

[0043] Any example implementation of transmission of RS that is occasionally turned on may rely on channel state information RS (CSI-RS) or tracking RS (TRS). In contrast, always-on transmission of RS may rely on one or more of, for example, a primary synchronization signal (PSS), a secondary synchronization signal (SSS), or a cell-specific reference signal. The PSS and / or SSS signals may be included in a repeatedly broadcast synchronization signal block (SSB), which also includes other components such as a physical broadcast channel, carrying information blocks including cell-specific information.

[0044] The transmission of RS that is occasionally turned on can define a repetitive transmission scheme. This can be associated with the corresponding repetition rate of RS. The schedule of RS can be specified. The sequence design of TRS can be specified.

[0045] Because the always-on transmission of the corresponding other RS ​​is always available, the transmission of the occasionally-on RS is simultaneous with the always-on transmission (i.e., available at the same time). Therefore, in principle, the UE can choose to try to receive (monitor) the other RS ​​of the always-on transmission or the RS of the occasionally-on transmission, or both.

[0046] As a general rule, the repetition rate of transmission of an RS that is occasionally turned on (e.g., TRS) may be greater than the repetition rate of transmission of another RS ​​that is always turned on (e.g., PSS). This may have the benefit that the waiting time until the RS that occasionally turns on transmission is received is shorter. Therefore, when the UE monitors the RS that occasionally turns on transmission when operating in disconnected mode, the synchronization time can be reduced.

[0047] As a further general rule, the bandwidth of a transmission of an occasionally-on RS may be larger than the bandwidth of an always-on transmission of another RS. This means that an occasionally-on transmission can cover a wider frequency range than an always-on transmission. Wider bandwidth RS transmissions will enable fine frequency / time synchronization. For example, multiple RSs may be spread over a wider bandwidth, or a single RS may occupy a considerable bandwidth.

[0048] The various techniques are based on the finding that since a UE operating in disconnected mode using a DRX cycle may use transmissions of an RS that is occasionally turned on, the UE (once the radio interface is transitioned from an inactive state back to an active state in preparation for an on period of the DRX cycle) may need some additional information about whether the transmissions of the RS that are occasionally turned on are currently configured by the communication NW (in particular, compared to always-on transmissions of an RS for which the UE can simply start monitoring because it is always active and the UE makes corresponding assumptions in the absence of dedicated DL signaling from the cellular NW).

[0049] According to various examples described herein, techniques are provided to facilitate corresponding exchange of configuration information indicating at least one configuration of transmission of an occasionally-on RS between a communicating NW and a UE.

[0050] For example, before switching to disconnected mode, when the UE (still) operates in connected mode, the communication NW may send at least one DL message including configuration information for occasionally turning on transmission, and the UE may receive at least one DL message. Then, after switching to RRC-idle or RRC-inactive mode (so-called disconnected mode), when operating in disconnected mode according to the corresponding DRX cycle, the UE may monitor the RS occasionally transmitted by the communication NW according to at least one configuration. The RS is suitable for maintaining synchronization in another communication between the UE and the communication NW.

[0051] As a general rule, the other communication may include a UL signal and / or a DL signal.

[0052] Figure 1 A cellular NW 100 is schematically shown. Figure 1The example shows a cellular NW 100 according to the 3GPP 5G architecture. The details of the 3GPP 5G architecture are described in 3GPP TS 23.501 version 15.3.0 (2017-09). Figure 1 The following and other parts of the description show the technology in the 3GPP 5G framework of cellular NW, but similar technology can be easily applied to other communication protocols. Examples include 3GPP LTE 4G (for example, in the MTC or NB-IoT framework), and even non-cellular wireless systems such as IEEE Wi-Fi technology.

[0053] exist Figure 1 In the scenario, UE 101 may be connected to cellular NW 100. For example, UE 101 may be one of the following: a cellular phone; a smart phone; an IoT device; an MTC device; a sensor; an actuator, etc. UE 101 has a corresponding identity 451, such as a subscriber identity.

[0054] UE 101 may be connected to a core NW (CN) 115 of cellular NW 100 via RAN 111, which is typically formed by one or more BSs 112 (for simplicity, Figure 1 Only a single BS 112 is shown in the figure. A wireless link 114 is established between the RAN 111 and the UE 101 (particularly between one or more BSs 112 of the RAN 111 and the UE 101). In order to perform channel sounding, the BS 112 may provide one or more transmissions of one or more RSs. For example, the BS 112 may provide an always-on transmission of a first RS. The BS 112 may also provide a transmission of a second RS that is occasionally turned on. To this end, the BS 112 may configure corresponding occasionally turned-on transmissions for one or more UEs that are connected or have been connected to a corresponding cell of the cellular NW 100, for example, by maintaining a corresponding registry.

[0055] The radio link 114 implements a time-frequency resource grid. OFDM is typically used: here, one carrier comprises a number of subcarriers. The subcarriers (frequency domain) and the symbols (time domain) then define the time-frequency resource elements of the time-frequency resource grid. Thus, the protocol time base is defined, for example, by the duration of frames and subframes comprising a number of symbols and the start and stop positions of the frames and subframes. Different time-frequency resource elements may be allocated to different logical channels of the radio link 114. Examples include: Physical DL Shared Channel (PDSCH); Physical DL Control Channel (PDCCH); Physical Uplink Shared Channel (PUSCH); Physical Uplink Control Channel (PUCCH); Random Access Channel, etc.

[0056] CN 115 includes a user plane (UP) 191 and a control plane (CP) 192. Application data is usually routed through UP 191. For this purpose, a UP function (UPF) 121 is provided. UPF 121 can implement a router function. Application data can pass through one or more UPFs 121. Figure 1 In the scenario of , UPF 121 acts as a gateway toward data NW 180 (eg, the Internet or a local NW). Application data can be transmitted between UE 101 and one or more servers on data NW 180.

[0057] The cellular NW 100 also includes a mobility control node, here implemented by an access and mobility management function (AMF) 131 and a session management function (SMF) 132 .

[0058] The cellular NW 100 also includes a policy control function (PCF) 133; an application function (AF) 134; an NW slice selection function (NSSF) 134; an authentication server function (AUSF) 136; and a unified data management (UDM) 137. Figure 1 The protocol reference points N1-N22 between these nodes are also described.

[0059] AMF 131 provides one or more of the following functions: connection management, sometimes also referred to as registration management; NAS termination for communications between CN 115 and UE 101; connection management; reachability management; mobility management; connection authentication; and connection authorization. For example, if the corresponding UE 101 is operating in idle mode, AMF 131 controls the CN of UE 101 to initiate paging. AMF 131 may trigger the sending of a paging signal to UE 101; this may coincide in time with a paging occasion (PO). The timing of the PO may be determined based on the UE identity 451. After the UE registers with the NW, AMF 131 creates a UE context 459 and maintains the UE context, at least as long as the UE 101 is registered with the NW. UE context 459 may save one or more identities of UE 101, for example, a temporary identity for paging as described herein.

[0060] If the corresponding UE 101 operates in connected mode, a data connection 189 is established by the SMF 132. The data connection 189 is characterized by UE subscription information hosted by the UDM 137. In order to track the current mode of the UE 101, the AMF 131 sets the UE 101 to CM-CONNECTED or CM-IDLE. During CM-CONNECTED, a non-access stratum (NAS) connection is maintained between the UE 101 and the AMF 131. The NAS connection implements an example of a mobile control connection. The NAS connection can be established in response to paging of the UE 101.

[0061] SMF 132 provides one or more of the following functions: session management, including session establishment, modification and release, including establishment of UP bearer between RAN 111 and UPF 121; selection and control of UPF; configuration of traffic steering; roaming functions; termination of at least some NAS messages, etc. In this way, both AMF 131 and SMF 132 implement CP mobility management required to support mobile UEs.

[0062] A data connection 189 is established between the UE 101 and the RAN 111 and continues to the UP 191 of the CN 115 and towards the DN 180. For example, a connection to the Internet or another packet data NW may be established. In order to establish the data connection 189, i.e., to connect to the cellular NW 100, the corresponding UE 101 may perform a random access (RACH) procedure, for example, in response to the reception of a paging signal. This establishes at least one RAN portion of the data connection 189. A server of the DN 180 may host a service that transmits payload data over the data connection 189. The data connection 189 may include one or more bearers, such as a dedicated bearer or a default bearer. The data connection 189 may be defined on the RRC layer, for example, typically layer 3 of the OSI model.

[0063] Figure 2 Various aspects are schematically shown regarding a number of operating modes 301 - 303 in which a UE may operate.

[0064] The data connection 189 is established in the connected mode 301. Specifically, the RAN part of the data connection 189 is established in the connected mode 301. Data can be transmitted between the UE 101 and the BS 112 using PDSCH, PDCCH, PUSCH, PUCCH. RRC control messages can be transmitted on PDSCH and / or PUSCH. Connected mode DRX can be used. The connected mode 301 can be implemented by 3GPP RRC connection mode.

[0065] Figure 2 Also shown are disconnected modes 302-303. The first disconnected mode is an idle mode 302, for example, implemented by a 3GPP RRC idle mode. The second disconnected mode is an inactive mode 303, for example, implemented by a 3GPP RRC inactive mode. Typically, the inactive mode 303 is transparent to the CN 115; whereas the idle mode 302 may be signaled to the CN 115. Thus, when the UE 101 operates in the inactive mode 303, the UE context 459 may be maintained at the CN 115.

[0066] Figure 2Also shown are aspects of transitions 309 between the various modes 301-303. For example, to trigger a transition 309 from the connected mode 301 to one of the disconnected modes 302-303, a connection deactivation message may be transmitted, for example using RRC control signaling on the PDSCH or PUSCH. This may be a connection inactivity control message for transition 309 to the inactive mode 303; or a connection release message for transition 309 to the idle mode 302. The connection release message triggers the release 189 of the data connection. The connection deactivation message may include an information element carrying additional data.

[0067] The transition 309 from idle mode 302 or inactive mode 303 to connected mode 301 includes a RACH procedure. The RACH procedure may be triggered by a paging signal, such as a paging indicator on the PDCCH and a paging message on the PDSCH. In inactive mode 303, paging may be triggered by the RAN; whereas in idle mode 302, paging is triggered by the CN.

[0068] The paging signal is sent at the paging occasion. The timing of the paging occasion is based on the identity 451 of the UE 101. The UE 101 can configure the DRX cycle based on the timing of the paging occasion (PO). In particular, the UE 101 can control its radio interface so that it is active and ready to receive data (e.g., by blindly decoding the PDCCH of the paging indicator) at the beginning of the on period of the DRX cycle. Details on the operation of the UE 101 using the DRX cycle are described in Figure 3 Shown in.

[0069] Figure 3 Schematically illustrated are various aspects regarding a DRX cycle 390. The DRX cycle 390 may be used by the UE 101 in one or both of the disconnected modes 302-303, or even in the connected mode 301. Figure 3 The activity of various components of the radio interface of the UE 101 is shown as a function of time to implement the DRX cycle 390. More specifically, Figure 3 The activity of the various components of the radio interface is shown by indicating the UE power consumption.

[0070] When using DRX cycle 390, UE 101 periodically switches between inactive state 391 ( Figure 3 1801 and 1804) and activity state 392 ( Figure 3The modem switches its wireless interface between the active state 392 and the active state 392 during the period 1803 in the active state 392. Periods 1801 and 1804 correspond to the off period of the DRX cycle 390; and period 1803 corresponds to the on period of the DRX cycle 390. Period 1803 of the active state 392 is aligned in time with the PO 396 during which the cellular NW 100 can send a paging signal. Figure 3 A respective cycle duration 399 of the DRX cycle 390 , ie the periodicity or duration of the individual periods of the DRX cycle 390 , is shown.

[0071] The timing of PO 396 is given by (i) the system frame number (SFN) and (ii) the subframe within that frame and (iii) the UE_ID (e.g., 3GPP NR), which is derived from the corresponding identity 451 of UE 101.

[0072] The UE 101 cannot receive paging signals when operating the modem in the inactive state 391; for example, the analog front end and / or the digital front end of the modem can be powered off. For example, the amplifier and the analog-to-digital converter can be turned off. For example, the decoding digital block can be turned off. The UE hardware enters the inactive state 391 when power can be saved. When the UE hardware is in the inactive state 391, one or more clocks may be turned off, all radio modules and most modem modules may be turned off, and when the time for the next PO 396 can be maintained, there is only minimal activity of the low-frequency (RTC) clock to start the platform. Therefore, the inactive state 391 is associated with relatively small power consumption.

[0073] When operating the modem in active state 392, UE 101 may monitor for paging signals. Various hardware components of the modem of the wireless interface are powered on and running. For example, UE 101 may perform blind decoding of the PDCCH to detect a paging indicator. Active state 392 is therefore associated with relatively high power consumption.

[0074] like Figure 3 As shown, there is a period 1802 required to convert the UE 101 from the inactive state 391 to the active state 392 (wake-up time). This conversion may require (re)adjusting the frequency and timing, and starting the modem to be able to receive the paging signal. The UE 101 can receive one or more RS 901 during the period 1802 to (re)synchronize.

[0075] exist Figure 3 In the scenario of , UE 101 does not receive a paging signal during period 1803 (paging occasion); and accordingly, it switches back to inactive state 391 during period 1804. The process is repeated after period 399 of DRX cycle 390 (eg Figure 3Once the paging indicator is detected, the UE 101 then reads the paging message on the PDSCH or paging channel (PCH) (not shown). Based on the paging message, a data connection 189 can be established.

[0076] As will be Figure 3 As will be appreciated, period 1802 is significant. That is, there is significant power consumption at UE 101 to facilitate synchronization with cellular NW 100 prior to PO 396. In the following, strategies are described that facilitate shortening period 1802 through fast synchronization. In particular, strategies are described that facilitate such shortening of period 1802 by facilitating transmission of fast and / or finely synchronized RS 901 during period 1802 prior to PO 396.

[0077] Figure 4 BS112 is schematically shown. BS112 includes a control circuit 1122 that can load program code from a memory 1123. BS112 also includes an interface 1125 that can be used to communicate with a node of a CN 115 of a cellular NW 100 on a wireless link 114. Therefore, the interface 1125 may include an analog front end and a digital front end, as well as an antenna port, etc., for communicating on the wireless link 114. The control circuit 1122 can load program code from the memory 1123 and execute the program code. When executing the program code, the control circuit 1122 can perform the techniques described herein, such as: configuring and providing transmission of RS, for example, occasionally turning on transmission and / or always turning on transmission; when operating in disconnect mode 302-303, receiving an indication of the ability of UE101 to monitor RS 901 that occasionally turns on transmission; providing configuration of transmission of RS to UE 101, etc.

[0078] Figure 5UE 101 is schematically shown. UE 101 includes control circuit 1012 that can load program code from memory 1013. UE 101 also includes a wireless interface 1015 that can be used to communicate with BS 112 of cellular NW 100 over wireless link 114. Therefore, wireless interface 1015 can include analog front end and digital front end, antenna port, etc. Control circuit 1012 can load program code from memory 1013 and execute the program code. When executing the program code, the control circuit 1012 can perform the techniques described herein, such as: for example, monitoring the RS when operating in the disconnect mode 302-303; sending an indication to the cellular NW 100 indicating the ability to monitor the RS that occasionally turns on transmission when operating in the disconnect mode 302-303; obtaining the configuration of the RS's transmission from the cellular NW 100 and monitoring the RS according to the configuration; controlling the wireless interface 1015 to switch between the inactive state 391 and the active state 392; operating in one of the modes 301-303, etc.

[0079] Figure 6 is a flow chart of a method according to various examples. Figure 6 The method may be performed by a UE. For example, Figure 6 The method may be performed by UE 101. More specifically, Figure 6 The method may be executed by the control circuit 1012 of the UE 101 when the program code is loaded from the memory 1013.

[0080] At block 2001, configuration information for possible occasional on-transmission of an RS (when the UE is in disconnected mode) is received (e.g., upon request of the UE or triggered in other ways, e.g., by the UE receiving an indication of the corresponding capability of the RS to occasionally on-transmission when operating in disconnected mode 302-303). Occasional on-transmission is not guaranteed, but may need to be activated separately.

[0081] One or more DL messages including configuration information may be received. Therefore, in some scenarios, the configuration information may be distributed in multiple DL messages.

[0082] For example, the one or more DL messages may include a data connection deactivation message that triggers a transition from the connected mode to the disconnected mode 302-303.

[0083] When operating in connected mode, such as in connected mode 301 or Figure 2 Thus, higher layer control signaling along an established control channel or data channel of a data connection may be used to deliver one or more DL messages.

[0084] At least one of the one or more DL messages may be received at a predetermined time before switching to disconnect mode 302-303. That is, there may be a time offset between receiving at least one DL message and switching to disconnect mode 302-303, which is defined at or before receiving at least one of the one or more DL messages.

[0085] For example, at least one of the one or more DL messages may be received within 10 ms, or within 100 ms, or within 1 s before transitioning to disconnected mode 302 - 303 ; this may correspond to a predetermined time.

[0086] For example, one or more 3GPP RRC control messages may be used to provide configuration information.For 3GPP scenarios, when the UE is in RRC connected mode, RRC control messages may be transmitted on the PDSCH.

[0087] The configuration information may indicate at least one configuration of the transmission of the RS that is occasionally turned on. Therefore, in some examples, the configuration information may indicate multiple configurations of the transmission of the RS that is occasionally turned on, for example, with various attributes such as time-frequency resources, repetition rate or schedule. This will give the UE the possibility to select from multiple configurations.

[0088] When switching from connected mode to disconnected mode (e.g., switching from connected mode 301 to idle mode 302 (inactive mode 303, see Figure 2 )), configuration information indicating at least one configuration of transmission of RS that is occasionally turned on may also be valid for the UE; therefore, the configuration information may be marked as expected configuration information.

[0089] As a general rule, there are multiple options available for implementing configuration information. Some of these options are shown in Table 1 below.

[0090]

[0091]

[0092] Table 1: Implementation variants of configuration information for indicating at least one configuration of transmission of an RS that is occasionally turned on

[0093] The QCL indicator (see Table 1, variant B or C) can help monitor the transmission of RS that is occasionally turned on. For example, the receiving operation of the antenna array of the wireless interface of the UE can be selected based on the QCL indicator. That is, the amplitude and phase of the various antenna elements of the antenna array can be appropriately selected. This is sometimes also referred to as monitoring using a given receive beam, that is, the spatial properties of the receive sensitivity. In addition, this is sometimes also referred to as monitoring using given channel properties, such as Doppler spread / frequency shift, average delay, delay spread and / or average gain. In particular, the receiving operation can be selected using the QCL assumption with the previous transmission. For example, the previous transmission may include a transmission during connected mode, before switching to sleep mode, for example, on a PDSCH shared channel. Alternatively or additionally, the previous transmission may include the transmission of another RS ​​(e.g., SSB). As a general rule, if the radio channel properties of the channel transmitting the symbols on one antenna port can be inferred from the channel transmitting the symbols on another antenna port, the two antenna ports are referred to as quasi-co-located. The radio channel properties shared across the antenna ports may be selected from the following: Doppler spread / shift, average delay, delay spread, average gain and / or spatial receiver parameters. Thus, the QCL assumption may require the transmitter (e.g., BS) to use the same or QCL antenna port for transmissions of the occasionally turned-on RS and previous transmissions. As a general rule, the QCL assumption may be fixedly configured, e.g., according to a communication standard (e.g., instead of signaling it).

[0094] As a general rule, such variants illustrated in Table 1 may also be combined with each other. For example, in variant A of Table 1, a flag may be provided (e.g. as part of a data connection deactivation message triggering a transition from connected mode to disconnected mode) indicating that a previously provided complete configuration with occasional on-transmission may also be reused in idle mode (variants A+B). For further illustration, multiple configurations of multiple BWPs and multiple groups may be envisioned (variants D+E).

[0095] After performing the transition from connected mode to disconnected mode 302-303, at block 2002 the UE monitors possible RSs, ie listens to the radio link 114 and attempts to receive in the configured allocation. This is consistent with at least one configuration of transmission of RSs occasionally turned on at block 2001.

[0096] The RS is adapted to keep synchronization with the communication NW in another communication, for example during the on period of the DRX cycle. This means that the RS may have a sequence-based structure, for example similar to PSS and / or SSS.

[0097] For example, as shown in Table 1, appropriate time-frequency resources may be selected according to the configuration information. An appropriate BWP and / or UE group may be selected, and based on the selection, an appropriate configuration may be selected from a plurality of configurations.

[0098] Next, at optional block 2003, if received based on monitoring at block 2002, then based on at least one received attribute of the RS, attempt to demodulate another transmission. For example, the analog receiver chain can be tuned based on time / frequency synchronization to derive the phase of the received RS. Gain control can be used.

[0099] By using at least one configuration of transmission of the RS that is occasionally turned on at block 2002, the synchronization time can be reduced. Figure 3 For example, the period 1802 can be shortened. The UE power consumption can be reduced.

[0100] Figure 7 is a flow chart of a method according to various examples. Figure 7 The method may be performed by an access node of a communication NW. For example, Figure 7 The method may be performed by a BS of a cellular NW. For example, Figure 7 The method may be performed by the BS 112 of the cellular NW 100 (see Figure 1 ). More specifically, Figure 7 The method may be executed by the control circuit 1122 of the BS 112 when the program code is loaded from the memory 1123 .

[0101] Figure 7 The method is usually Figure 6 For example, Figure 7 The method can be used with Figure 6 methods are aligned and executed in coordination with each other.

[0102] At block 2011, the access node sends configuration information for transmission of the RS that is occasionally turned on. For example, one or more DL control messages including the configuration information may be sent. The configuration information may be sent to the UE; in particular, the UE may operate in a connected mode (see Figure 2 : Connection mode 301). Box 2011 is associated with box 2001 (see Figure 6 ).

[0103] Configuration information for transmission of an occasionally enabled RS may be included in a connection deactivation message that triggers a transition from connected mode to disconnected mode (see Figure 2 , disconnection mode 302-303). For example, the transmission of the connection deactivation message may be triggered by a core NW node of the communication NW.

[0104] In box 2012, the access node provides transmission of RS that is occasionally turned on, that is, RS is sent according to the time-frequency resources, timing and / or repetition rate of the occasionally turned on transmission. Therefore, occasionally turning on transmission usually defines the transmission framework of RS. This is consistent with the configuration information of box 2011. Box 2012 and box 2002 are interrelated.

[0105] Any other transmission that may be provided may then be demodulated by the receiver of the transmission of the RS that is occasionally turned on, based on the reception properties of the RS.

[0106] Figure 8 is a flow chart of a method according to various examples. For example, Figure 8 The method can be Figure 6 A more specific implementation of a more general method. Figure 8 The method can be performed by the UE. Figure 8 The method of 1000 is described in various examples performed by UE 101. In addition, various examples are described in the context of using a corresponding TRS that occasionally turns on transmission. For example, see 3GPP TS 38.211 V15.8.0 (2019-12), Section 7.4.1.5.

[0107] At block 2100, the UE 101 operates in RRC connected mode 301. That is, a data connection 189 is established. The UE 101 is connected through the BS 112 of the serving cell of the cellular NW 100.

[0108] At block 2101, UE 101 is configured with transmission of an occasionally turned-on TRS by cellular NW 100. To this end, UE 101 receives a DL message including configuration information indicating at least one configuration of TRS transmission. Each TRS configuration may specify (e.g., among other attributes) a time-frequency resource and a schedule for occasionally turned-on transmission (see Table 1, variant B). Multiple TRS configurations may be provided (see Table 1, variant DE).

[0109] The UE 101 then monitors the TRS while operating in connected mode 101. This is consistent with the TRS configuration. The TRS helps maintain synchronization with the cellular NW 100.

[0110] In block 2102, UE 101 sends a UL message to cellular NW 100. The UL message indicates the capability of UE 101 to monitor TRS while operating in idle mode 302 or inactive mode 303, for example, using the same TRS configuration used for monitoring in block 2101 or another configuration.

[0111] Thus, when operating in disconnected mode 302-303, the UE may indicate whether it supports TRS processing for occasional on TRS transmissions.

[0112] At block 2103, the UE 101 receives a DL message including (further) configuration information indicating a configuration of the transmission of the occasionally turned-on TRS to be used when operating in idle mode. For example, this may be a one-bit flag (see Table 1, variant A) indicating that the previously provided configuration of the transmission of the occasionally turned-on TRS used at block 2101 may also be used by the UE when performing a transition to disconnected mode 302-303. In another case, a new complete TRS configuration (or multiple complete TRS configurations) is provided, see Table 1, variant B.

[0113] The UE then performs a transition to one of the disconnected modes 302-303 and operates in the corresponding disconnected mode 302-303 at block 2104. This is consistent with the DRX cycle 390. For example, the transition to the disconnected mode 302-303 may be triggered by a data connection deactivation message received from the cellular NW 100 and the data connection deactivation message may include the one-bit flag discussed above in conjunction with block 2103.

[0114] In block 2105, it is checked whether preparations need to be made for the on period of the DRX cycle 390. The on period may be aligned with the PO. In particular, this may involve a corresponding lead time for powering up the components of the wireless interface 1015, as previously described in connection with Figure 3 In addition, time period 1802 is used to monitor TRS.

[0115] The UE 101 then continues operation at block 2106 in case of an upcoming on-period of the DRX cycle 390 (otherwise the wireless interface 1015 remains in the inactive state 391).

[0116] In block 2106, the UE 101 determines whether one or more predetermined criteria are met.

[0117] One or more predetermined criteria may enable a UE 101 (ie, in principle possessing a TRS configuration of disconnected mode 302-303) to abandon TRS monitoring.

[0118] When executing block 2106, the connectivity of UE 101 (i.e., the ability to communicate with cellular NW 100) is limited, if any. This is because there is no or only inaccurate synchronization. This has been combined with Figure 3 Explanation is made: period 1802. Therefore, the one or more predetermined criteria may be a decision criterion mainly centered on the UE. Therefore, the UE 101 may determine whether the one or more predetermined criteria are met without receiving corresponding data from the cellular NW 100.

[0119] Monitoring of the TRS is then selectively performed based on whether one or more predetermined criteria are met. This helps avoid expending effort on processing unqualified TRS, for example, producing unreliable estimates of timing reference or synchronization.

[0120] As a general rule, there are multiple options available for achieving such one or more predetermined criteria. Some options are described in conjunction with Table 2.

[0121]

[0122]

[0123] Table 2: Options for predefined criteria for monitoring RS occasionally turning on transmission at UE

[0124] As a general rule, various scenarios can be combined according to Table 2. For example, multiple decision criteria can be configured. A hierarchy can be configured between decision criteria, such that if a higher level decision criterion is met, then some lower level decision criteria do not need to be met.

[0125] As a general rule, one or more decision criteria may be partially or fully configured by the NW, or partially or fully configured by the UE. One or more decision criteria may be fixed, for example, according to a standard. When configured by the communicating NW, the corresponding decision criterion configuration information may be provided as part of the same DL message that carries the configuration information for transmission of the RS that is occasionally turned on (see Table 1).

[0126] If the check at box 2106 concludes that UE 101 is to monitor TRS that occasionally turns on transmission, the method starts at box 2107.

[0127] At block 2107, UE 101 monitors TRS. Block 2107 thus corresponds to Figure 6 Box 2002.

[0128] As a general rule, UE 101 may have received configuration information indicating multiple configurations of transmission of TRS that is occasionally turned on (see Table 1, variants D and E). Then, in block 2107, UE 101 may select an appropriate configuration from the multiple configurations. For example, the multiple configurations may be related to multiple BWPs and / or multiple groups of UEs. The UE may then check which part it is operating on and / or which group it belongs to, and select an appropriate configuration.

[0129] At block 2108, the UE checks whether the TRS has been successfully received at block 2107. If yes, the method starts at block 2110.

[0130] At block 2110, the UE checks whether sufficiently accurate synchronization with the cellular NW 100 has been established. In a simple scenario, this check may be based on the number of received TRS and / or PSS and / or further RS. If synchronization is complete, regular idle mode operation may begin at block 2111. This may include, for example, receiving one or more paging signals, for example, receiving a paging indicator on the PDCCH by blind decoding, and optionally receiving a paging message on the PDSCH based on the paging indicator. One or more further periods of the DRX cycle 390 may also be triggered, such as Figure 8 Alternatively, UE 101 may also perform a transition to connected mode 101 (in which case UE 101 may request or be configured with an updated configuration for transmission of an occasionally enabled TRS, or be provided with an indication that the configuration used when operating in disconnected mode 302-303 may continue to be used).

[0131] On the other hand, if synchronization with the cellular NW 100 at block 2110 is not (fully) completed or successful, further iterations of block 2106 may be triggered.

[0132] There is also a case where the decision at block 2106 indicates disabling (further) monitoring of the TRS because one or more decision criteria for TRS monitoring are not met (see Table 2). The method then starts directly at block 2109, where the UE 101 monitors the SSB and can establish synchronization based on the PSS included in the SSB.

[0133] In a scenario where receive beamforming is implemented at the UE, the same spatial receive filter may be used to monitor TRS at block 2107 and monitor SSB at block 2109 .

[0134] exist Figure 8 In the scenario, if the monitoring of TRS at box 2107 is judged to be unsuccessful at box 2108, fallback to SSB-based synchronization is also implemented. In this case, after box 2108, box 2109 is executed.

[0135] As will be understood, in Figure 8 In the scenario of , the UE 101 monitors not only the TRS transmitted using the occasional on transmission (at block 2107), but also monitors the always on PSS included in the SSB at block 2109. Synchronization may then be established on both the reception properties of the TRS and the reception properties of the PSS and subsequent transmissions during idle mode operation at block 2111; and any demodulation of the PDCCH, for example, may be based on the reception properties of both the TRS and the PSS.

[0136] exist Figure 8In the scenario, if reception of TRS fails at box 2107, monitoring of SSB at box 2109 is selectively performed. Failure of reception of TRS at box 2107 may have multiple reasons: for example, RAN 111 may stop TRS transmission and UE 101 is still in disconnected mode 302-303. Then, the UE may not be aware that TRS is no longer available (for example, due to limited connectivity in disconnected mode 302-303). RAN 111 may terminate TRS transmission because another target UE operating in connected mode 301 (TRS transmission may be initially configured for the target UE) changes its state to disconnected mode 302-303. In this case, UE 101 fails TRS reception at box 2107. Failure of TRS reception may have other reasons, such as path loss, low signal-to-noise ratio, etc.

[0137] This conditional execution of SSB monitoring that relies on TRS reception failure is usually optional. Other variants that combine TRS-based synchronization with PSS-based synchronization can be imagined. For example, in a first variant, it is conceivable that UE 101 always attempts to monitor TRS and PSS / SSS. In another variant, UE 101 may first monitor TRS for coarse synchronization with cellular NW 100, and secondly monitor SSB for fine synchronization with cellular NW 100, which takes into account coarse synchronization. In another variant, UE 101 may initially receive SSB and perform coarse synchronization based on PSS / SSS. If necessary, UE 101 can then continue to receive TRS for fine synchronization. Therefore, two-step synchronization can be achieved, wherein the first stage can be implemented by PSS / SSS and the second stage can be implemented by TRS, or vice versa. Therefore, demodulation accuracy can be improved.

[0138] Fig. 9 is a signaling diagram of communication between BS 112 and UE 101. Fig. 9 Also shown is the communication between the BS 112 and another UE 102. The other UE 102 continues to operate in the connected mode 301, while the UE 101 (as combined with e.g. Figure 8 309 (here in Fig. 9 Middle: Idle mode 302).

[0139] At 5000, BS 112 sends a DL control message 4021 to both UE 101 and UE 102. For example, RRC signaling may be used. DL control message 4021 indicates the configuration of the transmission of the occasionally turned-on TRS. For example, DL control message 4021 may include multiple configurations of multiple BWPs. DL control message 4021 may indicate the various time-frequency resources used to transmit the TRS. DL control message 4021 may indicate the repetition rate of the schedule for the transmission of the occasionally turned-on TRS. See Table 1, variant B.

[0140] And in Fig. 9 In the scenario of , the DL control message 4021 is sent to both UE 101 and UE 102 substantially simultaneously, in other cases, there may be a time offset; for example, the transmission of the occasionally turned-on TRS may first be configured for the first UE, and then after the time gap configured for the second UE. Another option is that UE 101 and UE 102 (while operating in connected mode 301 respectively) may be configured with different TRS transmissions, for example, with different repetition rates, schedules and / or sequence designs of the TRS. Then, when preparing to transition 309 to disconnected mode 302, UE 101 may be configured with the transmission of the occasionally turned-on TRS that was initially configured for UE 102.

[0141] At 5001 , UE 101 and UE 102 may then monitor TRS 4001 based on the TRS configuration of TRS 4001 providing at 5000 to occasionally turn on transmission.

[0142] Based on the reception properties of the TRS, UE 101 and UE 102 can demodulate the PDSCH of the PDCCH ( Fig. 9 (not shown). Channel detection can be implemented. Beamforming can be adjusted.

[0143] At 5002, UE 101 sends a UL message to BS 112. UL message 4022 indicates the ability of UE 101 to monitor TRS when operating in disconnected mode 302-303. More specifically, UL message 4022 may indicate the ability of UE 101 to monitor TRS using the specific TRS configuration provided at 5000. UE 101 may also request another TRS configuration. For example, UL message 4022 may be an RRC connection release request message indicating the intention of UE 101 to transition to disconnected mode 302-303. UL message 4022 may also be another RRC control message sent, for example, at initial access.

[0144] Based on the ability of UE 101 to monitor TRS when operating in disconnected mode 302-303, BS 112 may then configure corresponding occasional on transmissions 303 of TRS 4001 for UE 101 operating in disconnected mode 302-303. For example, BS 112 may maintain corresponding logs of UEs 101-102 for which corresponding occasional on transmissions of TRS 4001 are currently configured. For example, the corresponding logs may include the duration or validity period of each occasional on transmission.

[0145] At 5003, BS 112 sends a connection deactivation message 4011, which triggers a transition 309 from the connected mode 301 to the disconnected mode 302-303 (specifically, at Fig. 9 In the scenario shown, idle mode 302). The connection deactivation message 4011 includes an indicator indicating that the UE 101 is authorized to continue monitoring the TRS 4001 according to the TRS configuration provided at 5000 when operating in idle mode 302; this may be a one-bit flag (see Table 1, variant A).

[0146] Subsequently, the UE 101 transitions to idle mode 302. The data connection 189 between the UE 101 of the RAN 111 is released.

[0147] BS112 then continues to send TRS 4001 with occasional on-transmission using the TRS configuration provided at 5000. For example, BS112 sends TRS 4001 at 5004. This TRS 4001 sent by BS112 at 5004 is received by UE 102, which continues to operate in connected mode 301, but is not received by UE 101. At time 5004, UE 101 operates its interface in inactive state 391. Therefore, UE 101 does not attempt to receive TRS 4001 sent at 5004. This is different at 5005. Again, BS112 sends TRS 4001 at 5005 using the corresponding TRS configuration with occasional on-transmission of TRS 4001. This time, UE101 (preparing for the on period of DRX cycle 390) monitors TRS 4001 and successfully receives TRS 4001. Refer to Fig. 9 , at 5006, UE 101 also receives SSB 4002 sent by BS 112, but this is generally optional. For example, if sufficiently accurate synchronization can be established based solely on the reception properties of TRS 4001, UE 101 can skip monitoring of SSB 4002 or more specifically PSS / SSS. This helps save power. In addition, although in Fig. 9In the scenario of FIG. 5 , UE 101 first receives TRS 4001 at 5005 and only then receives SSB 4002 at 5006, but in other scenarios, UE 101 may first receive SSB 4002 and later receive TRS 4001. In such a scenario, two-step synchronization may be achieved, i.e., coarse synchronization based on PSS / SSS included in SSB 4002 and then fine synchronization based on TRS 4001. This reduces the need to receive multiple SSBs 4002 to obtain accurate synchronization, thereby reducing power consumption.

[0148] Based on the amplitude and / or phase and / or timing of the PSS in TRS 4001 and SSB 4002, UE 101 may then establish synchronization with BS 112. Alternatively or additionally, gain control may be implemented. UE 101 may then continue idle mode operation and Fig. 9 In the illustrated scenario, one or more paging signals 4012 are received at 5007. For example, UE 101 may perform blind decoding of PDCCH at 5007 based on establishing synchronization to receive a paging indicator. Therefore, UE 101 monitors TRS 4001 at 5005 before receiving the corresponding paging occasion of one or more paging signals 4012 at 5007 (see Figure 3 :Duration: 1802).

[0149] As will be Fig. 9 It is contemplated that the BS 112 configures the occasional on transmission of the TRS 4001 for the UE 101 operating in the idle mode 302 and for the UE 102 operating in the connected mode 301. Thus, it can be said that the UE 101 reuses the occasional on transmission of the TRS 4001 that is required anyway for the connected mode operation of the UE 102. In other examples, the occasional on transmission of the TRS 4001 may be configured specifically for the UE 101 operating in the idle mode 302, such as in the case where the UE 101 is released to the idle mode 302.

[0150] As a general rule, the BS 112 may primarily configure the occasional on transmission of the TRS 4001 for one or more first UEs operating in the connected mode 301, and then secondarily configure the occasional on transmission for one or more second UEs operating in the disconnected mode 302, 303. Then, upon detecting that the one or more first UEs operating in the connected mode 301 have transitioned to the disconnected mode 302, 303 and / or have left the coverage of the BS 112 and / or upon detecting another triggering event associated with the one or more first UEs, the BS 112 may deactivate the occasional on transmission, e.g., regardless of whether the one or more second UEs are still in the disconnected mode 302, 303 and / or in the coverage of the BS 112. The BS 112 may take into account the time that has passed since the configuration of the one or more second UEs, e.g., the validity of the respective configuration at the time when the decision is made.

[0151] Fig.10 Various aspects of occasionally turning on transmission 900 with respect to RS 901 are shown. Various examples described herein may be used in conjunction with Fig.10 Such a technique is described in the occasionally-on transmission 900.

[0152] The occasional on transmission 900 of the RS 901 may be characterized by a number of attributes of the corresponding configuration. For example, a schedule 952 and a repetition rate 953 at which the RS 901 is transmitted may be associated with the occasional on transmission 900. Fig.10 Also shown is a scenario where the occasionally-on transmission 900 has a certain effective duration 951. The occasionally-on transmission 900 can also be characterized by a set of time-frequency resources allocated to the RS 901.

[0153] like Fig.10 As shown, there is a control message 4021 including configuration information indicating the configuration of occasional on transmission 900. Unlike the always on transmission of RS, before receiving the configuration information included in the message 4021, the UE 101 cannot make an assumption about the presence of occasional on transmission.

[0154] In summary, various techniques have been described to help configure transmission of an RS that is occasionally turned on for a UE operating in a disconnected mode. For example, transmission of a TRS that is occasionally turned on can be configured for a UE operating in a disconnected mode.

[0155] Such techniques can typically be combined with conventional always-on transmission of RS, for example, always-on transmission of PSS and SSS included in SSB. For example, the UE can combine the reception of TRS with the reception of SSB, and can even replace or reduce the amount of SSB reception with TRS reception. For example, when the UE is relatively stationary (i.e., has long mobility) and has strong received signal strength, it may rely only on TRS. Therefore, the power consumption of the UE can be reduced without compromising the demodulation performance, for example, when attempting to modulate the PDCCH in the on period of the DRX cycle.

[0156] Although the invention has been shown and described with respect to certain preferred embodiments, equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalents and modifications and is limited only by the scope of the appended claims.

[0157] For illustration, various examples have been described in connection with a scenario where an RS that occasionally turns on transmission is implemented by a TRS. The corresponding techniques can be easily applied to other kinds and types of RSs that are provided by occasionally turning on transmission.

[0158] Further explanation, various examples of receiving an RS that occasionally turns on transmission have been described, where the RS is suitable for maintaining synchronization with the communication NW in another transmission from the communication NW to the UE. However, similar techniques can be easily applied to UL communications from the UE to the communication NW; in such examples, using an RS suitable for maintaining synchronization is also helpful.

[0159] For further explanation, although various examples have been explained in connection with implementing the disconnect mode through an idle mode or an inactive mode, other scenarios may include other implementations of the disconnect mode, ie, other power saving modes.

Claims

1. A method of operating a wireless communication device, the method comprising: - when operating in connected mode, before transitioning to disconnected mode: receiving from the communication network at least one downlink message comprising configuration information indicating at least one configuration of transmission of an occasionally switched-on reference signal, - when operating in the disconnected mode according to a discontinuous reception cycle: monitoring the reference signal occasionally transmitted by the communication network according to the at least one configuration, The reference signal is suitable for maintaining synchronization with the communication network in another communication during an on period of the discontinuous reception cycle.

2. The method according to claim 1, in, The configuration information includes a flag indicating whether the wireless communication device can continue to use the at least one configuration after completing the transition to the disconnect mode.

3. The method according to claim 1, in, The configuration information includes a multi-bit information element indicating a plurality of attributes of the at least one configuration.

4. The method according to claim 1, in, The at least one configuration includes at least one of time-frequency resources allocated for transmission of the reference signal that is occasionally turned on, spatial resources allocated for transmission of the reference signal that is occasionally turned on, a quasi-co-location indicator with respect to another reference signal, a repetition rate, and a schedule for transmission of the reference signal that is occasionally turned on.

5. The method according to claim 1, in, The configuration information relatively defines at least a part of the at least one configuration with respect to another configuration of another transmission of another reference signal.

6. The method according to claim 1, in, The at least one downlink message comprises a data connection deactivation message triggering a transition to the disconnected mode.

7. The method according to claim 1, in, The occasionally turned-on transmission of the reference signal is configured for at least one further wireless communication device.

8. The method according to claim 7, in, The at least one further wireless communication device is in the connected mode.

9. The method according to claim 1, in, The at least one configuration includes a plurality of configurations associated with a plurality of groups of wireless communication devices.

10. The method according to claim 1, in, The at least one configuration includes a plurality of configurations for a plurality of bandwidth portions.

11. The method according to claim 1, further comprising: - when operating in the connected mode: sending an uplink message to the communications network, the uplink message indicating a capability of the wireless communications device to monitor the reference signal according to the at least one configuration when operating in the disconnected mode.

12. The method according to claim 1, further comprising: - when operating in said disconnected mode: determining whether one or more predetermined criteria are met, Wherein, the monitoring of the reference signal is selectively performed according to whether the one or more predetermined criteria are met.

13. The method according to claim 12, in, The one or more predetermined criteria include a received signal strength threshold for received signal strength determined based on monitoring another reference signal transmitted by the cellular network in accordance with the always-on transmission.

14. The method according to claim 12, in, The one or more predetermined criteria include a mobility state threshold for mobility of the wireless communication device.

15. The method according to claim 12, in, The one or more predetermined criteria include cell identities of cells of the communication network that are within coverage of the wireless communication device.

16. The method according to claim 12, in, The one or more predetermined criteria include one or more of the following: a timing threshold for the time elapsed since the configuration information was received; a cycle duration threshold for the cycle duration of the discontinuous reception cycle; a threshold traffic load for communications between the wireless communication device and the communication network; and a success rate of said monitoring of said reference signal.

17. The method according to claim 5, further comprising: - when operating in the disconnected mode according to the discontinuous reception cycle: monitoring an always-on reference signal transmitted according to an always-on transmission, The another transmission is attempted to be demodulated further based on another reception property of the always-on reference signal.

18. The method according to claim 17, in, The monitoring of the always-on reference signal is selectively performed if reception of the reference signal fails.

19. The method according to claim 17, in, The monitoring of the always-on reference signal and the monitoring of the reference signal are accomplished using a common spatial receive filter.

20. The method according to claim 17, further comprising: - performing a coarse synchronization with the communication network based on the further reception property of the always-on reference signal, - performing a fine synchronization with the communication network based on the coarse synchronization and further based on the reception properties of the reference signal.

21. The method according to claim 1, in, The communication network provides an always-on transmission of another reference signal, The repetition rate of the transmission of the reference signal that is occasionally turned on is greater than another repetition rate of the transmission of the other reference signal that is always turned on.

22. The method according to claim 21, in, The communication network provides an always-on transmission of another reference signal, The bandwidth of the occasionally turned-on transmission of the reference signal is greater than the bandwidth of the always-on transmission of the other reference signal.

23. The method according to claim 5, in, performing said monitoring of said reference signal prior to a paging occasion, Wherein, the another transmission includes at least one paging signal.

24. A method of operating an access node of a communication network, the method comprising: - sending at least one downlink message to a wireless communication device operating in a connected mode, the at least one downlink message comprising configuration information indicating at least one configuration of transmission of an occasionally turned-on reference signal, and - performing transmission of the reference signal turned on occasionally when the wireless communication device operates in disconnected mode using a discontinuous reception cycle.

25. The method according to claim 24, further comprising: - configuring the wireless communication device and at least one further wireless communication device operating in the connected mode to occasionally switch on the transmission of the reference signal.

26. The method according to claim 24, further comprising: - configuring the transmission of the reference signal to be occasionally turned on specifically for the wireless communication device operating in the disconnected mode.

27. The method according to claim 24, further comprising: - when the wireless communication device is operating in the connected mode: receiving an uplink message from the wireless communication device, the uplink message indicating a capability of the wireless communication device to monitor the reference signal according to the at least one configuration when operating in the disconnected mode, - selectively configuring transmission of the reference signal to be occasionally turned on for the wireless communication device operating in the disconnected mode based on the capabilities of the wireless communication device.

28. A wireless communication device, comprising a control circuit, wherein the control circuit is configured to: - when operating in connected mode, before transitioning to disconnected mode: receiving from the communication network at least one downlink message comprising configuration information indicating at least one configuration of transmission of an occasionally switched-on reference signal, - when operating in the disconnected mode according to a discontinuous reception cycle: monitoring the reference signal occasionally transmitted by the communication network according to the at least one configuration, in, The reference signal is suitable for maintaining synchronization with the communication network in another communication during an on period of the discontinuous reception cycle.

29. The wireless communication device according to claim 28, in, The control circuit is configured to perform the method of any one of claims 2 to 23.

30. An access node of a communication network, the access node comprising a control circuit, the control circuit being configured to: - sending at least one downlink message to a wireless communication device operating in connected mode, the at least one downlink message comprising configuration information indicating at least one configuration of transmission of an occasionally turned-on reference signal, and - performing transmission of the reference signal turned on occasionally when the wireless communication device operates in disconnected mode using a discontinuous reception cycle.

31. The access node according to claim 30, wherein: The control circuit is configured to perform the method according to any one of claims 25 to 27.

Images