Patent Description:
Secure and reliable wireless communication is an important part of modern infrastructure. The usage of machine-to-machine (M2M) communications and other Internet of Things (IoT) applications increases significantly, e.g., as communication devices (UEs) shrink in size and costs.

One example of wireless communication is communication according to the Third Generation Partnership Project (3GPP) framework. Here, M2M communication, industrial IOT, and vehicle-to-vehicle (V2V) or vehicle-to-everything (V2x) communication is expected to require highly reliable connectivity. Network failures or coverage issues are to be avoided or, at least, detected. For example, within the 3GPP New Radio (NR) access system, ultra-reliable-low-latency is used to describe a toolset to achieve such highly reliable connectivity, along with low latency. Thereby, occurrence of network failures or coverage issues are to be monitored such that appropriate countermeasures may be taken, if needed. This is to facilitate a quick reaction to situations when a UE is no longer reachable or otherwise exhibits limited connectivity.

<CIT> relates to a paging profiling method for determining a number of page repetition and a time interval between the page repetitions. The method comprises triggering the paging profiling by causing a page relating to one or more wireless communication devices. In some embodiments the method may further comprise updating an entry of a paging pattern database based on the paging profiling, wherein the entry is associated with a geographical area in which the one or more wireless communication devices reside. The paging pattern database may, for example, be comprised in a server. In some embodiments, the method may also comprise detecting that the paging profiling is needed by detecting that the entry of the paging pattern database is not valid, and triggering the paging profiling may be enabled responsive to detecting that the paging profiling is needed. Corresponding paging profiling arrangement, computer program product, wireless communication device and server are also disclosed.

<NPL> further discusses methods for coverage enhancement.

<CIT> relates to wireless communications, and more specifically to enhanced paging procedures for devices with limited communications resources, such as machine type communication (MTC) devices and enhanced or evolved MTC (eMTC) devices. An example method generally includes determining a set of subframes corresponding to a paging occasion for the UE to receive a paging message from a base station (BS), determining, within the set of subframes, at least one narrowband region for receiving the paging message, and monitoring for the paging message in the at least one narrowband region within the set of subframes.

Therefore, a need exists for advanced techniques of monitoring connectivity of UEs.

A method of operating a communication device includes receiving at least one downlink signal transmitted by a base station of a network. The at least one control message is received while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network. The method further includes determining a receive property of the at least one downlink signal based on said receiving. The method may optionally further include transmitting an uplink report signal indicative of the receive property of the at least one downlink signal.

A computer program product includes program code that may be executed by at least one processor. Executing the program code causes the at least one processor to perform a method of operating a communication device. The method includes receiving at least one downlink signal transmitted by a base station of a network. The at least one control message is received while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network. The method further includes determining a receive property of the at least one downlink signal based on said receiving. The method may optionally further include transmitting an uplink report signal indicative of the receive property of the at least one downlink signal.

A computer program includes program code that may be executed by at least one processor. Executing the program code causes the at least one processor to perform a method of operating a communication device. The method includes receiving at least one downlink signal transmitted by a base station of a network. The at least one control message is received while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network. The method further includes determining a receive property of the at least one downlink signal based on said receiving. The method may optionally further include transmitting an uplink report signal indicative of the receive property of the at least one downlink signal.

A communication device includes control circuitry which is configured to perform: while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and a network: receiving at least one downlink signal transmitted by a base station of the network; and determining a receive property of the at least one downlink signal based on said receiving; and, optionally, transmitting an uplink report signal indicative of the receive property of the at least one downlink signal.

A method of operating a base station of a network includes transmitting at least one downlink signal. The method further includes receiving, from a communication device, an uplink report signal. The uplink report signal is indicative of a receive property of the at least one downlink signal. The at least one downlink signal is received by the communication device while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network.

A computer program product includes program code that may be executed by at least one processor. Executing the program code causes the at least one processor to perform a method of operating a base station. The method includes transmitting at least one downlink signal. The method further includes receiving, from a communication device, an uplink report signal. The uplink report signal is indicative of a receive property of the at least one downlink signal. The at least one downlink signal is received by the communication device while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network.

A computer program includes program code that may be executed by at least one processor. Executing the program code causes the at least one processor to perform a method of operating a base station. The method includes transmitting at least one downlink signal. The method further includes receiving, from a communication device, an uplink report signal. The uplink report signal is indicative of a receive property of the at least one downlink signal. The at least one downlink signal is received by the communication device while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network.

A base station of a network includes control circuitry configured to perform: transmitting at least one downlink signal; receiving, from a communication device, an uplink report signal indicative of a receive property of the at least one downlink signal received by the communication device while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network.

A method of operating a base station of a network includes transmitting at least one downlink signal. The at least one downlink signal is transmitted while a communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network. The method further includes receiving, from the communication device, an uplink report signal. The uplink report signal is indicative of a receive property of the at least one downlink signal.

A computer program product includes program code that may be executed by at least one processor. Executing the program code causes the at least one processor to perform a method of operating a base station. The method includes transmitting at least one downlink signal. The at least one downlink signal is transmitted while a communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network. The method further includes receiving, from the communication device, an uplink report signal. The uplink report signal is indicative of a receive property of the at least one downlink signal.

A computer program includes program code that may be executed by at least one processor. Executing the program code causes the at least one processor to perform a method of operating a base station. The method includes transmitting at least one downlink signal. The at least one downlink signal is transmitted while a communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network. The method further includes receiving, from the communication device, an uplink report signal. The uplink report signal is indicative of a receive property of the at least one downlink signal.

A base station of a network includes control circuitry configured to perform: transmitting at least one downlink signal while a communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network; and receiving, from the communication device, an uplink report signal. The uplink report signal is indicative of a receive property of the at least one downlink signal.

A system includes a base station of a network, the base station including first control circuitry. The system also includes a communication device including second control circuitry. The first control circuitry is configured to transmit at least one downlink signal. The second control circuitry is configured to receive the at least one downlink signal, while the communication device operates in a disconnected mode in which a data connection is not set-up between the communication device and the network. The at least one downlink signal may or may not be directed to the communication device. The second control circuitry is configured to determine a receive property of the at least one downlink signal based on said receiving. The second control circuitry may optionally be configured to transmit an uplink report signal which is indicative of the receive property of the at least one downlink signal. The first control circuitry may optionally be configured to receive the uplink report signal.

It is to be understood that the features mentioned above and those yet to be explained below may be used not only in the respective combinations indicated, but also in other combinations or in isolation.

The embodiments described hereinafter or by the drawings are taken to be illustrative only.

Hereinafter, techniques of monitoring connectivity of UEs are described. In particular, by means of the techniques described herein, it may be possible to reliably and flexibly detect limited connectivity.

Limited connectivity may be associated with reduced or no reachability of the respective UE. A latency of communication between a network and the UE may be significantly increased in the state of limited connectivity. Limited connectivity may be associated with a certain degraded reachability level of the UE. By the techniques described herein, functionality to supervise the reachability may be provided. Thereby, the network can ensure that it is capable of contacting the UE if need be, e.g., at a certain connection probability that is associated with the connectivity. Here, a reachability level may correspond to the success ratio of communicating uplink signals and/or downlink signals between the UE and the network.

Various techniques described herein enable monitoring connectivity of UEs across different operation modes of the UE. In particular, techniques described herein may enable monitoring the connectivity of a UE even if the UE operates in a disconnected mode.

Typically, a data connection between the UE and the network is not set up in the disconnected mode. Examples of disconnected mode include: idle mode; wake-up mode; power-save mode; etc. It is possible that a registry entry of the UE is maintained at the network while the UE operates in the disconnected mode. Typically, it may not be possible or only possible to a limited degree to communicate payload data - e.g., data associated with an application layer of a transmission protocol stack - between the UE and the network while the UE operates in disconnected mode. Then, if there is data to be transmitted between the network and the UE, it may be possible to page the UE. For this, a paging signal or wake-up signal may be employed. A data communication may be set up in order to transition operation of the UE from the disconnected mode to the connected mode. In this connection, it is possible to employ a random access procedure.

Such techniques of monitoring connectivity of the UE across different operation modes of the UE may be beneficial, in particular, when being applied to M2M, IOT, V2V or V2x scenarios. In particular, for such use cases, it is expected that the overall amount of data to be communicated between the respective UE and the network is comparably limited; however, if there is in fact data to be communicated between the UE and the network, this should typically occur at a high reliability and low latency. Hence, it is possible that in such use cases, the respective UEs operate in the disconnected mode over an extended duration of time, e.g., in more than <NUM>% or <NUM>% or even <NUM>% of the overall operational time. Hence, by means of the techniques described herein, it is possible to monitor the connectivity of the UEs even when they operate in disconnected mode. This is an advantage if compared to conventional channel sounding techniques where in connected mode pilot signals are communicated between the network and the UE.

By means of at least some of the techniques described herein, it is possible to inform an application layer of the transmission protocol stack if limited connectivity is experienced. The application layer may take appropriate countermeasures. Alternatively or additionally, countermeasures may be taken by the network. Such countermeasures may help to increase connectivity of the UE and/or to mitigate negative impact of the limited connectivity on one or more applications implemented by the UE and the network.

According to examples, a UE receives at least one downlink (DL) signal which is transmitted by a base station (BS) of the network. The UE receives the at least one DL signal while the UE operates in a disconnected mode. Hence, the BS transmits the at least one DL signal while the UE operates in the disconnected mode. Here, the data connection is not set up between the UE and the network. Then, the UE may determine a receive property of the at least one DL signal and may then transmit, to the network, an uplink (UL) report signal which is indicative of the receive property. The BS may receive the UL report signal. In response to said receiving of the UL report signal, one or more countermeasures for facilitating the connectivity with the UE may be selectively triggered, e.g., by taking into account the receive property.

By receiving the at least one DL signal even while operating in the disconnected mode, it is possible to monitor the connectivity of the UE while operating in the disconnected mode based on the respective receive property of the at least one DL signal. This helps to monitor connectivity over an extended duration of time.

The UL report signal may be transmitted by the UE while the UE operates in disconnected mode or while the UE operates in connected mode. Likewise, the UL report signal may be received by the BS while the UE operates in disconnected mode or while the UE operates in connected mode.

Depending on the connectivity, it would be possible to trigger one or more countermeasures. For example, if the network identifies limited connectivity - e.g., if a negotiated reachability level cannot be sustained -, the network and notify the UE. The UE may then provide this information on the limited connectivity to a higher layer such as the application layer. The claimed invention corresponds to <FIG>, <FIG> and to the related text in the description. The remaining figures and the text of the description are intended to better explain the invention.

<FIG> illustrates aspects with respect to the architecture of a cellular network <NUM> according to some examples implementations. In particular, the cellular network <NUM> according to the example of <FIG> implements the 3GPP LTE architecture, sometimes referred to as evolved packet system (EPS). This, however, is for exemplary purposes only. In particular, various scenarios will be explained in the context of a wireless link <NUM> between a UE <NUM> and the cellular network <NUM> operating according to the 3GPP LTE radio access technology (RAT) for illustrative purposes only. Similar techniques can be readily applied to various kinds of 3GPP-specified RATs, such as Global Systems for Mobile Communications (GSM), Wideband Code Division Multiplex (WCDMA), General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), Universal Mobile Telecommunications System (UMTS), and High Speed Packet Access (HSPA), and corresponding architectures of associated cellular networks. The network <NUM> may be operating according to the 3GPP NR framework. A further particular example is the 3GPP NB-IoT RAT. The 3GPP NB-IoT RAT may be based on the 3GPP LTE RAT, i.e., the Evolved UMTS Terrestrial Radio Access (E-UTRA). Further, the NB-IoT RAT may be combined with the EPS as illustrated in <FIG>. The various examples disclosed herein may be readily implemented for the 3GPP NB-IoT RAT, alternatively or additionally. Similarly, the techniques described herein may be employed for MTC. Other examples include other types of networks, e.g., Institute of Electrical and Electronics Engineers (IEEE) <NUM>. 11X Wireless Local Area Network, Bluetooth or Zigbee.

The 3GPP LTE RAT implements a HARQ protocol. The HARQ protects data communicated via the wireless link <NUM>. FEC and retransmission are employed in this respect.

The UE <NUM> is registered to the network <NUM>. In the example of <FIG>, the UE <NUM> is connected to the network <NUM> via the wireless link <NUM> to a BS <NUM> of the cellular network <NUM>. The BS <NUM> and the UE <NUM> implement the evolved UMTS terrestrial radio access technology (E-UTRAN); therefore, the BS <NUM> is labeled evolved node B (eNB) in <FIG>. In other examples, the UE <NUM> may be registered to the network <NUM>, but no active data connection may be maintained.

For example, the UE <NUM> may be selected from the group including: a smartphone; a cellular phone; a table; a notebook; a computer; a smart TV; a MTC device, an IoT device; a sensor; an actuator; etc..

An MTC or IoT device is typically a device with a low to moderate requirement on data traffic volumes and loose latency requirements. Additionally, communication employing MTC or IoT devices should achieve low complexity and low costs. Further, energy consumption of an MTC or an IoT device should be comparably low in order to allow battery-powered devices to function for a comparably long duration: The battery life should be sufficiently long. For example, the IoT device may be connected to the EPS via the NB-IoT RAT.

Communication on the wireless link <NUM> can be in UL and / or DL direction. The BS <NUM> is connected with a gateway node implemented by a serving Gateway (SGW) <NUM>. The SGW <NUM> may route and forward payload data and may act as a mobility anchor during handovers of the UE <NUM>.

The SGW <NUM> is connected with a gateway node implemented by a packet data network Gateway (PGW) <NUM>. The PGW <NUM> serves as a point of exit and point of entry of the cellular network <NUM> for data towards a packet data network (PDN; not shown in <FIG>): for this purpose, the PGW <NUM> is connected with an access point node <NUM> of the packet data network. The access point node <NUM> is uniquely identified by an access point name (APN). The APN is used by the UE <NUM> to seek access to the packet data network.

The PGW <NUM> can be an endpoint of an data connection <NUM> for packetized payload data of the UE <NUM>. The data connection <NUM> may be used for communicating payload data of a particular service. Different applications/services may use different data connections <NUM> or may share, at least partly, a certain data connection.

In a 3GPP NR scenario, the SGW <NUM> and PGW <NUM> functionality may be implemented by a user plane function (UPF).

The data connection <NUM> may be implemented by one or more bearers which are used to communicate service-specific data. An EPS bearer which is characterized by a certain set of quality of service parameters indicated by the QoS class identifier (QCI). The data connection may be, at least partly, defined on a Layer <NUM> or Layer <NUM> of a transmission protocol stack implemented by the BS <NUM> and the UE <NUM> for communicating on the wireless link <NUM>. For example, in connection with the 3GPP LTE E-UTRAN, the data connection <NUM> may be implemented on the Radio Resource Control (RRC) layer.

A control layer of the core network includes a mobility management entity (MME) <NUM>. The MME <NUM> functionality may be implemented by a Access and Mobility Management Function (AMF) and the Session Management Function (SMF) in a 3GPP NR framework.

The MME <NUM> handles mobility and security tasks such as paging and access credentials. The MME <NUM> also keeps track of the operational mode of the UE <NUM>, e.g., whether the UE <NUM> operates in connected or disconnected mode. The MME <NUM> is the termination point of the non-access stratum (NAS) connection, i.e., a control connection implemented on the layer above the RRC layer.

A home subscriber server (HSS) <NUM> includes a repository that contains user- and subscriber-related information such as authentication and subscription information. In 3GPP NR, such functionality may be implemented by the Authentication Server Function (AUSF) and/or the Unified Data Management (UDM) functionality.

A Policy and Charging Rules Function (PCRF) implements policy control to thereby facilitate a certain QoS. The respective function is implemented by the Policy Control Function (PCF) in the 3GPP NR framework.

<FIG> illustrates aspects with respect to different modes <NUM>-<NUM>, <NUM> in which the UE <NUM> can operate. In all states illustrated in <FIG>, the UE <NUM> may be registered with the network <NUM>, i.e., may be EMM-REGISTERED in 3GPP LTE or MM-REGISTERED in 3GPP NR. Thus, a corresponding entry may be kept at the MME <NUM>. The network <NUM> may page the UE <NUM>.

In connected mode <NUM>, the data connection <NUM> is set up. For example, a default bearer and optionally one or more dedicated bearers may be set up between the UE <NUM> and the network <NUM>.

In order to reduce the power consumption, it is then possible to transition from the connected mode <NUM> to a connected mode <NUM> which employs a discontinuous reception (DRX) cycle (Connected mode DRX).

The DRX cycle includes on durations and off durations (not illustrated in <FIG>). During the off durations, an interface of the UE <NUM> is unfit to receive data; e.g., an analog and/or digital frontend may at least be partially powered down. The timing of the DRX cycle is synchronized between the UE <NUM> and the BS <NUM> such that the BS <NUM> can align any DL transmission with the on durations of the connected mode DRX cycle. The data connection <NUM> is maintained established in mode <NUM> even during the off durations. The data connection <NUM> is not released.

To achieve a further power reduction, it is possible to transition into one or more disconnected modes <NUM>, <NUM>. Here, the data connection <NUM> is released and not set up.

One example of a disconnected mode <NUM>, <NUM> is the idle mode <NUM>. The idle mode <NUM> is, again, associated with an idle mode DRX cycle of the UE <NUM>. However, during the on durations of the DRX cycle in idle mode <NUM>, the interface of the UE <NUM> is only fit to receive paging messages on the channel <NUM>. For example, this may help to restrict the frequency bandwidth that needs to be monitored by the UE during the on durations of the DRX cycles in idle mode <NUM>. This may help to further reduce the power consumption - e.g., if compared to the connected mode <NUM>.

For example, when transitioning from the connected mode <NUM> to the idle mode <NUM>, it would be possible to release the data connection <NUM>.

A further example of a disconnected mode is the wake-up mode <NUM>; here, instead of paging signals wake-up signals may be received, e.g., by a dedicated low-power receiver of the UE <NUM>.

<FIG> is an example scenario only. In other examples fewer, more, or different modes may be used. For example, in the 3GPP NR context, a RRC-INACTIVE CONNECTED mode may be used, see 3GPP (Technical Report) TR <NUM>, Study on Architecture for Next Generation System, V. <NUM> (Nov. Here, the UE keeps parts of the RAN context; these parts remain valid when re-connecting to the network. Such parts may include the Access Stratum (AS) security context, UE capability information, etc..

<FIG> illustrates aspects with respect to transitioning between the different modes <NUM> - <NUM>. Furthermore, <FIG> illustrates aspects of employing DRX cycles.

First, the UE <NUM> operates in the connected mode <NUM>. This causes a persistent power consumption at a high level. The interface of the UE <NUM> is in an active state <NUM>.

Then, in order to reduce the power consumption, the connected mode <NUM> employing DRX is activated. Here, the on durations <NUM> and the off durations <NUM> of the DRX cycle are illustrated. During the off durations <NUM>, the interface <NUM> is in an inactivate state <NUM> in which it is unfit to receive signals and to transmit signals. The inactive state <NUM> is associated with a low energy consumption.

To further reduce the power consumption, next, the idle mode <NUM> is activated. This is accompanied by releasing the data connection <NUM>. Again, the idle mode <NUM> employs a DRX cycle including on durations <NUM> and off durations <NUM>. The on durations <NUM> in mode <NUM> are associated with a lower power consumption if compared to the on durations <NUM> in connected mode <NUM>, because in the idle mode <NUM>, the capability of the interface can be reduced if compared to the connected mode <NUM>. Thus the interface of the UE <NUM> operates in a power-save state <NUM> during the on durations <NUM>. During idle mode <NUM>, the receiver of the interface may only expect reception of paging signals. This may help to restrict the bandwidth and / or restrict the need for complex demodulation functionality.

<FIG> illustrates aspects with respect to transitioning between operation in the connected mode <NUM> and in the idle mode <NUM>. <FIG> is a signaling diagram schematically illustration communication between the UE <NUM> and the BS <NUM>.

First, payload data <NUM> is communicated at <NUM>. For example, UL payload data <NUM> and/or DL payload data <NUM> may be communicated. For communicating the payload data <NUM>, the data connection <NUM> is employed. The UE <NUM> operates in connected mode <NUM>.

The payload data <NUM> may be associated with one or more applications implemented on an application layer of a transmission protocol stack implemented by the UE <NUM> and the BS <NUM> for communicating on the wireless link. For example, the payload data <NUM> may be latency-sensitive.

Then, there is no more payload data <NUM> to be communicated, i.e., the respective transmission /reception buffers of the UE <NUM> and/or the BS <NUM> are empty. A corresponding timer <NUM>, sometimes referred to as inactivity timer, is triggered upon concluded communication of the payload data <NUM> at <NUM>. Upon expiry of the inactivity timer <NUM>, a transition to idle mode <NUM> occurs at <NUM>. At <NUM>, the data connection <NUM> is released.

In idle mode <NUM>, the UE <NUM> remains registered at the network <NUM>. For example, the MME <NUM> maintains a respective entry of the identity of the UE <NUM> and/or of the identity of the subscriber associated with the UE <NUM>. This facilitates paging of the UE <NUM>, e.g., if there is DL data to be transmitted from the network <NUM> to the UE <NUM>.

There are paging occasions <NUM> defined at which the UE <NUM>, according to the respective DRX cycle, listens for paging signals <NUM>. For example, the paging occasions <NUM> may be coincident with the on durations <NUM> of the DRX cycle. For example, the UE <NUM> can time-align the DRX cycle with the paging occasions <NUM>. For example, the UE <NUM> may receive broadcasted information to obtain fraim numbering and time synchronization with the cell. Then, the UE may calculate when the paging occasions will occur, e.g., by using the DRX cycle length and other frame timing information available. The paging occasion may be a function of the UE identity, e.g., the International Mobile Subscriber Identity (IMSI); thereby, different UEs may use different paging occasions. Once the UE <NUM> has obtained knowledge on the paging occasions <NUM> - e.g., the time in-between subsequent paging occasions <NUM> - the appropriate DRX cycle may be selected. Thereby, it can be ensured that the on durations <NUM> of the DRX cycle are synchronized with the paging occasions <NUM>.

As illustrated in <FIG>, eventually, the network <NUM> makes a paging attempt; therefore, the BS <NUM> transmits a paging signal <NUM> at <NUM>. In response to receiving the paging signal <NUM> with the respective paging occasions <NUM>, the UE <NUM> transitions into operating in the connected mode <NUM>, <NUM>. This transition may involves a random access procedure and a RRC setup procedure for setting up the data connection <NUM>.

While in the example of <FIG> the transition to the connected mode <NUM> is in response to receiving the paging signal <NUM>, in other examples, the UE <NUM> may proactively trigger the transition to the connected mode <NUM>, e.g., in response to a need to transmit UL payload data.

<FIG> illustrates aspects with respect to mobility of the UE <NUM>. <FIG> illustrates multiple cells <NUM> - <NUM> of the cellular network <NUM>. The different cells <NUM> - <NUM> are associated with one or more BSs (not illustrated in <FIG>). The cells <NUM> - <NUM> form a tracking area. Hence, if the network <NUM> attempts to page the UE <NUM> in the idle mode <NUM>, paging signals <NUM> may be transmitted by the various BSs of the cells <NUM> - <NUM> of the tracking area.

<FIG> schematically illustrates the BS <NUM> in greater detail. The BS <NUM> includes an interface <NUM>. The interface <NUM> is configured to wirelessly transmit and/or receive (communicate) signals on the wireless link <NUM>. The interface may include an analog front end, a digital front end, one or more antennas, etc. The BS <NUM> also includes control circuitry <NUM>, e.g., implemented by one or more processors, in hardware and/or software. The BS <NUM> also includes a memory <NUM>, e.g., a non-volatile memory. It is possible that program code is stored by the memory <NUM>. The program code may be executed by the control circuitry <NUM>. Executing the program code may cause the control circuitry <NUM> to perform techniques as described herein in connection with, e.g., transmitting one or more DL signals; receiving a UL report signal; triggering one or more countermeasures if limited connectivity of the UE is identified; etc..

<FIG> schematically illustrates the UE <NUM> in greater detail. The UE <NUM> includes an interface <NUM>. The interface <NUM> is configured to wirelessly communicate signals on the wireless link <NUM>. The interface may include one or more receivers, e.g., a main receiver and a wake-up receiver. The wake-up receiver may be configured to selectively receive wake-up signals, e.g., using a lower-or the modulation, limited frequency bandwidth, etc.. The interface <NUM> may include an analog front end, a digital front end, one or more antennas, etc. Transmit and/or receive beamforming is possible. The UE <NUM> also includes control circuitry <NUM>, e.g., implemented by one or more processors. The UE <NUM> also includes a memory <NUM>, e.g., a non-volatile memory. It is possible that program code is stored by the memory <NUM>. The program code may be executed by the control circuitry <NUM>. Executing the program code may cause the control circuitry <NUM> to perform techniques as described herein in connection with, e.g., receiving one or more DL signals while operating in a disconnected mode; transmitting a UL report signal; triggering one or more countermeasures if limited connectivity of the UE is identified; informing upper layers of a transmission protocol stack of the limited connectivity; etc..

<FIG> is a signaling diagram schematically illustrating communication between the UE <NUM> and the BS <NUM>. First, at <NUM> and <NUM>, DL signals <NUM> are transmitted by the BS <NUM> and received by the UE <NUM>.

At <NUM> and <NUM>, the UE <NUM> operates in a disconnected mode <NUM>, <NUM>. For example, the UE <NUM> may be operating in idle mode <NUM> when receiving the DL signals <NUM> at <NUM> and <NUM>. For example, the data connection <NUM> may have been previously released, e.g., due to expiry of an inactivity timer <NUM> (cf. Then, the DL signals <NUM> may be received in response to releasing the data connection <NUM>.

In the various examples described herein, different DL signals <NUM> may be used when monitoring the connectivity of the UE <NUM>. Examples of DL signals <NUM> that may be used include, but are not limited to: system information block; synchronization signal; paging signal directed to the UE <NUM>; paging signaled directed to a number UE different from the UE <NUM>; a cell-specific reference signal; a BS antenna specific reference signal; and a broadcasted signal.

For example, system information blocks may be broadcasted by the BS <NUM> at a comparably high repetition rate. Examples of sets system information blocks include the Master Information Block (MIB) and the Secondary Information Block (SIB) in the 3GPP LTE framework. Information blocks may be received by UEs operating in a disconnected mode prior to performing a random access procedure for setting up the data connection <NUM>. In particular, information blocks may include configuration data that is required for appropriately setting up the data connection <NUM>. Example configuration data that may be included in the information blocks includes, but is not limited to: a cell identity; a frequency bandwidth employed by the BS; access barring information; an operator associated with the cell; etc..

The synchronization signal may be used in order to define a mutual time reference between the UE <NUM> and the BS <NUM>.

Paging signals can be used to trigger a connection attempt of the UE <NUM> or of a different UE to the network. The paging signals may be UE specific. The paging may be triggered by the MME <NUM>. The paging may be based on the registration of the UE <NUM> at the network <NUM>.

Cell-specific and/or antenna specific reference signals can be used in order to perform channel sounding.

Thus, as will be appreciated, a wide variety of different DL signals <NUM> may be used in the various examples described herein. In particular, will be appreciated from the above, certain DL signals that are anyway transmitted for another purpose - e.g., facilitating random access, time synchronization, channel sounding, etc. - may be reused for the purpose of monitoring the connectivity of the UE <NUM> while the UE is in a disconnected mode. This reduces or avoids additional signaling overhead. Generally, the DL signals used in connection with monitoring the connectivity may be dedicated to the UE <NUM> or may not be dedicated to the UE <NUM>. It would be even possible that the DL signals used for monitoring the connectivity are dedicated to one or more different UEs. Then the UE <NUM> may eavesdrop on these DL signals that are directed to one or more different UEs for the purpose of monitoring the connectivity - this may be possible, because in some examples it may not even be required to demodulate and decode the DL signals, e.g., if the receive property relates to a signal level.

Then, at <NUM>, the UE <NUM> determines receive properties of the DL signals <NUM> received at <NUM> and <NUM>. At <NUM>, the UE transmits an UL report signal <NUM> which is indicative of the receive property as determined in <NUM>.

In the various examples described herein, different kinds of types of receive properties may be employed. In the invention, a signal strength, signal-to-noise ratio, an error rate of decoding a plurality of DL signals <NUM>, or (not in the invention) a decoding reliability may be considered.

This receive property may then be stored, for further use in connection with an UL report signal.

For example, determining the receive property may or may not include decoding and/or demodulation of the DL signals <NUM>. For example, if the UE <NUM> eavesdrops on DL signals <NUM> directed to one or more other UEs <NUM>, the UE may not even be capable to decode and/or demodulate the DL signals <NUM>, e.g., because appropriate configuration data and/or credentials are missing. In such scenarios, the signal strength or signal-to-noise ration may be considered. The signal strength may define the amplitude of the signal at an analog stage of the receiver. The signal-to-noise ratio may define the amplitude of the signal at the analog stage if compared to a background level prior to and after the signal.

The decoding reliability may define the degree of confidence with which a certain decoder, e.g., a Viterbi decoder, outputs decoded data. Decoding may be combined with demodulation.

The error rate may be a bit error rate (BER) or block error rate (BLER) or a packet error rate (PER).

The BS <NUM> receives the UL report signal <NUM>. Based on the UL report signal <NUM>, the BS <NUM> may judge whether the connectivity of the UE <NUM> is limited. This is possible even though the UE <NUM> operates in idle mode <NUM> or, generally, another disconnected mode when receiving the DL signals <NUM> at <NUM> and <NUM>.

Based on the receive properties of the DL signals <NUM>, it may be possible to determine whether the connectivity is limited. For example, if the receive properties indicate reduced reliability of the reception, a limited connectivity may be assumed.

While in the example of <FIG>, the UE <NUM> receives two DL signals <NUM> at <NUM> and <NUM>, generally, the UE <NUM> may receive a smaller or larger number of DL signals <NUM> before determining the receive property and transmitting a respective UL report signal <NUM>.

Illustrated in <FIG> is a scenario in which the connectivity of the UE <NUM> is continuously monitored. Hence, at <NUM> and <NUM>, the UE <NUM>, again, receives DL signals <NUM>; at <NUM>, the UE <NUM>, again, determines the receive property and transmits the respective UL report signal <NUM> at <NUM>. This process may be repeated from time to time; the time offset between subsequent UL report signals <NUM> being transmitted by the UE <NUM> may correlate with a time resolution with which the connectivity of the UE <NUM> can be monitored.

Reception of the DL signals <NUM> by the UE <NUM> occurs in receive timeslots <NUM> of a repetitive probing schedule. For example, a frequency of occurrence of the receive timeslots <NUM> may be set such that energy consumption by receiving the DL signals <NUM> on the one hand side, and time resolution of monitoring the connectivity of the UE <NUM> are balanced.

The receive timeslots <NUM> are intermittedely arranged. A strict periodicity of the receive timeslots <NUM> is not required.

For example, it is possible that the frequency of occurrence of the receive timeslots <NUM> is aligned with the typical mobility pattern expected for the UE <NUM>: For example, it would be possible that the frequency of occurrence of the subsequent receive timeslots is in the range of <NUM> - <NUM> seconds, optionally in the range of <NUM> - <NUM> seconds. This frequency of occurrence of the receive timeslots <NUM> may correlate with the time offset between subsequent receive timeslots <NUM>. It has been observed that by setting the receive timeslots <NUM> such that they have a respective frequency of occurrence, a favorable balance between energy consumption on the one hand side and time resolution of monitoring the connectivity of the UE <NUM> can be obtained; this is because the connectivity may vary on a timescale associated with the typical mobility pattern.

<FIG> illustrates aspects with respect to the repetitive probing schedule. <FIG> also illustrates aspects with respect to paging occasions <NUM> while the UE <NUM> is operating in idle mode <NUM>. <FIG> also illustrates aspects with respect to the DRX cycle including on durations <NUM> and off durations <NUM>: the paging occasions <NUM> are implemented by the on durations <NUM>.

As illustrated in <FIG>, the repetitive probing schedule is time-aligned with the DRX cycle. Hence, the receive timeslots <NUM> of the repetitive probing schedule are at least partially overlapping with the on durations <NUM> of the DRX cycle. In other words, the receive timeslots <NUM> of the repetitive probing cycle are coincident in time domain with the paging occasions <NUM>.

In the scenario of <FIG>, not every on duration <NUM> of the DRX cycle implements a receive timeslot <NUM> of the repetitive probing schedule. In particular, the receive timeslots <NUM> of the repetitive probing schedule are defined as integer multiples of the on durations <NUM> of the DRX cycle (in the non-limiting example of <FIG>, every fourth on duration <NUM> is at least partially overlapping with the respective receive timeslot <NUM> of the repetitive probing cycle).

Thus, as illustrated in <FIG>, the frequency of occurrence of the receive timeslots <NUM> of the repetitive probing schedule defines a time offset <NUM> between adjacent receive timeslots <NUM> which is larger by a certain factor (factor of <NUM> in the non-limiting example of <FIG>) than the respective time offset <NUM> between adjacent on durations <NUM> of the DRX cycle.

For example, the duration of the receive timeslots <NUM> may be extended if compared to the duration of the on durations <NUM> of the DRX cycle which are not at least partially overlapping with the receive timeslots <NUM>. Therefore, by implementing a reduced frequency of occurrence for the receive timeslots of the repetitive probing cycle if compared to the on durations of the DRX cycle, energy consumption can be reduced. In a further example, the bandwidth which is used for receiving the DL signals <NUM> in the receive timeslots <NUM> may be extended if compared to the bandwidth which is used for receiving any potential paging signals in the paging occasions <NUM> of the on durations <NUM> of the DRX cycle. Thereby, by implementing a reduced frequency of occurrence for the repetitive probing cycle if compared to the DRX cycle, energy consumption can be reduced.

As will be appreciated from <FIG>, the interface <NUM> - and, in particular, the receiver of the interface <NUM> - of the UE <NUM> is transitioned between the inactive state <NUM> and the power-save state <NUM> in accordance with the repetitive probing cycle (cf. This is due to the receive timeslots <NUM> being arranged intermittedly.

The DL signals <NUM> may be communicated according to a fixed, pre-defined schedule. This may correspond to "pinging" the UE with a certain frequency of occurrence to ensure that the connectivity is not limited, e.g., if DL signals <NUM> directed to the UE <NUM> are employed. For example, certain time-frequency resource elements may be allocated to the DL signals <NUM>. For example, information blocks broadcasted by the BS <NUM> may be fixedly allocated to certain time-frequency resource elements of a time-frequency resource grid. Thereby, also the repetition rate of communicating the DL signals <NUM> is well-defined.

In <FIG>, a scenario is illustrated where the time offset <NUM> between adjacent DL signals <NUM> is much smaller than the time offsets <NUM>, <NUM> (illustrated in the magnified in set of <FIG>). For example, if the DL signals <NUM> used when monitoring the connectivity of the UE <NUM> are implemented by information blocks, then such information blocks may be repeated on frame or even subframe level of the wireless link <NUM>. Hence, the repetition rate of the information blocks may be in the order of tens of milliseconds. Generally, the repetition rate of communication of the DL signals <NUM> may be larger than the frequency of occurrence of the receive timeslots <NUM>, e.g., at least by a factor of <NUM>, further optionally at least by a factor of <NUM>. Such a scenario may ensure that whenever a receive timeslot <NUM> is scheduled, there are sufficient opportunities for receiving a DL signal <NUM> available.

<FIG> is a signaling diagram illustrating communication between the UE <NUM> and the BS <NUM>. The example of <FIG> generally corresponds to the example of <FIG>. In the example of <FIG>, a larger count of DL signals <NUM> is received at <NUM> - <NUM>, prior to transmitting the UL report signal <NUM> at <NUM>. At <NUM>, the receive property is determined for the DL signals <NUM> previously received. By receiving a larger count of DL signals <NUM> per UL report signal <NUM>, the control signaling overhead can be reduced. For example, a count of at least <NUM> or at least <NUM> or at least <NUM> DL signals <NUM> could be received per UL report signal <NUM>.

Further, in various scenarios it would be possible that the UL report signal <NUM> does not include information indicative of the individual receive properties of each and every DL signal <NUM>; but rather includes information indicative of a combined receive property across the received DL signals <NUM>. In other words, it would be possible that the receive property includes statistics of said receiving of the plurality of DL signals <NUM>. By indicating statistics on the receiving of a plurality of DL signals <NUM>, on the one hand side, a reliable monitoring of the connectivity of the UE <NUM> becomes possible. In particular, one-time exceptions or off-trend behavior of the connectivity of the UE <NUM> can be put into relation by considering that statistics. Further, by including the information indicative of the statistics of the receiving of the plurality of DL signals <NUM>, the overall amount of data to be included in the UL report signal <NUM> may be reduced; thereby, control signaling overhead on the wireless link <NUM> may be reduced.

Example statistics include the number of successful and/or unsuccessful reception attempts of the DL signals <NUM>. For example, the unsuccessful reception attempts may be defined as such reception attempts with the signal-to-noise ratio of the DL signal <NUM> at the receiver of the UE <NUM> is below a threshold. Alternatively or additionally, the unsuccessful reception attempts may be defined as such reception attempts which do not allow for a successful decoding of data encoded by the DL signal <NUM>. It has been found that the number of unsuccessful reception attempts is an accurate measure for the connectivity of the UE <NUM>.

<FIG> also illustrates aspects with respect to a repetitive reporting schedule. In particular, the UL report signals <NUM> are transmitted and/or received (communicated) in accordance with a repetitive reporting schedule. As illustrated in <FIG>, the repetitive reporting schedule defines transmit timeslots <NUM> during which the UL report signals <NUM> are communicated. This is also illustrated in connection with <FIG>.

<FIG> illustrates aspects with respect to the repetitive reporting schedule. <FIG> illustrates a time arrangement of the receive timeslots <NUM> of the repetitive probing schedule and of the transmit timeslots <NUM> of the repetitive reporting schedule. As illustrated in <FIG>, the time offset <NUM> between adjacent transmit timeslots <NUM> is larger than the time offset <NUM> between adjacent receive timeslots <NUM>. This resembles the observation that in various scenarios it is possible to include information on the receive properties of a plurality of DL signals <NUM> in each UL report signal <NUM>, e.g., by considering the statistics on said receiving of the plurality of DL signals <NUM>. Hence, to accumulate sufficient information on the receive properties, it is possible to dimension the time offset <NUM> to be larger than the time offset <NUM>. For example, a typical length/duration of the time offsets <NUM> may be in the order of <NUM> seconds - <NUM> minutes, optionally in the range of <NUM> minutes - <NUM> minutes.

Alternatively or additionally to employing the repetitive reporting schedule, an UL report signal <NUM> may be transmitted in the various examples described herein if reception attempts for a certain number of DL signals <NUM> have been completed, and/or upon demand by the network, and/or if the data connection, and/or if a significance of statistics on the receive properties of a plurality of DL signals <NUM> exceeds a threshold, etc..

In the various examples described herein, different techniques are conceivable for transmitting the UL report signal <NUM>. For example, it would be possible that for transmitting the UL report signal <NUM> a random access procedure is performed and the data connection <NUM> is set up. Then, it is possible to transmit the UL report signal using the data connection <NUM>. Here, it may be desirable to avoid inefficient and overhead-expensive setting up of the data connection <NUM> by accumulating information on the receive properties of a comparably large count of DL signals <NUM> before transmitting the UL report signal <NUM>. Hence, it may be possible that the frequency of occurrence of the transmit timeslots <NUM> is dimensioned to be comparably small. Alternatively or additionally, it would also be possible to re-use a data connection <NUM> that is anyway set up due to other reasons, e.g., for transmitting a tracking area update message.

At the same time, the data connection <NUM> may also be quickly released in response to communication of the UL report signal <NUM>. In particular, the data connection <NUM> may be released by overriding the inactivity timer <NUM> (cf. Thereby, battery consumption of the UE <NUM> can be reduced. Such a scenario is illustrated in <FIG>.

<FIG> is a signaling diagram illustrating communication between the UE <NUM> and the BS <NUM>. <FIG> schematically illustrates such a setup of the data connection <NUM> between the UE <NUM> and the network <NUM> for transmitting the UL report signal <NUM> at <NUM>.

At <NUM>, a transition to the connected mode <NUM>, <NUM> is performed. This may include setting up the data connection <NUM>, e.g., by performing a random access procedure and a RRC setup procedure. Then, at <NUM>, the UL report signal <NUM> is transmitted using the previously set-up data connection <NUM>. Then, in response to transmitting the UL report signal <NUM> at <NUM>, at <NUM>, a transition to the disconnected state, e.g., the idle mode <NUM> is performed. The inactivity timer <NUM> is not implemented (cf. This helps to minimize the duration of the timeslot <NUM>.

<NUM> may be triggered by occurrence of the timeslot <NUM>. However, in other scenarios, other trigger criteria may be used for <NUM>. For example, to further reduce battery consumption and signaling overhead on the wireless link <NUM>, it would be possible that the data connection <NUM> used for transmitting the UL report signal <NUM> is set up in response to the need of communicating a tracking area update message. In particular, from time to time, while the UE <NUM> is operating in idle mode <NUM>, the UE may transmit a tracking area update message. The tracking area update message may be indicative of whether the UE is still located in the same tracking area (cf. <FIG>); or whether the UE <NUM> has moved into a different tracking area. Based on the tracking area update message, the network <NUM> can implement the paging of the UE <NUM>. For example, a typical frequency of occurrence of transmitting the tracking area update message may be in the order of <NUM> minutes; and, hence, may be suitable for synchronization with the transmit timeslots <NUM>.

As will be appreciated from the above, a time resolution with which the connectivity of the UE <NUM> can be monitored correlates with the frequency of occurrence of the transmit timeslots <NUM>. Therefore, in some scenarios, it may be desirable to implement a lower or higher time resolution by appropriately tailoring the frequency of occurrence of the transmit timeslots <NUM>. In particular, it would be possible that the reporting schedule is set up between the network <NUM> and the communication device <NUM>, e.g., using an appropriate configuration message. For example, it would be possible that the reporting schedule - and hence, the frequency of occurrence of the transmit timeslots <NUM> - is set up in accordance with at least one of the device category of the UE <NUM> and a reliability category associated with the UE <NUM>. This may occur during RRC setup or in connected mode <NUM>, <NUM>.

For example, the device category of the UE <NUM> may be selected from the following group: handheld device; smart phone; a MTC device; IOT device; vehicle; etc..

For example, the reliability category may specify a level of connectivity that should be implemented for the UE <NUM>. For example, it would be possible that certain UEs require a classification within the higher reliability category than others, e.g., due to the sensitivity or importance of the data communicated between the UE and the network. An example would be sensors or actuators in connected fabrication where it must be ensured with high reliability that each sensor or actuator is quickly reachable.

By taking into consideration the device category and/or the reliability category associated with the UE <NUM> when configuring the frequency of occurrence of the transmit timeslots <NUM>, it is possible to tailor the accuracy with which the connectivity of the UE <NUM> can be monitored to the respective needs, e.g., on a per-UE basis. At the same time, excessive control signaling overhead on the wireless link <NUM> due to repeated connections of the UE <NUM> to the network <NUM> can be avoided.

Thus, in some examples, a new UE type may be introduced. This UE type may indicate that the UE needs to be guaranteed application access by the network on a higher performance level then legacy UEs. One implementation for the UE to indicate that it belongs to this new UE type, could be to introduce it as a UE capability. Hence, it is possible that the UE reports its category/capability, e.g., as part of setting up the data connection <NUM>, e.g., as part of a RRC connection procedure. Then, the UE may indicate to the network <NUM> its higher-reliability access preference. The UE capability may be comparably static or semi-static within the network <NUM>, i.e., the UE <NUM> may update this capability information, but this is typically not done very often, e.g., on the order of hours or days or even months. The UE capability could also be coupled to a reachability configuration with the UE and the network may negotiate the reachability level that should be provided to the UE <NUM>.

In some examples, the control signaling overhead on the wireless link <NUM> can be further reduced by specifying certain time-frequency resource elements that can be used by the UE <NUM> to transmit the UL report signals <NUM> while continuously operating in idle mode <NUM> or, generally, a disconnected mode <NUM>, <NUM>. Then, it is not required to set up the data connection <NUM> each time the UL report signal <NUM> is to be transmitted. Such a scenario is illustrated in connection with <FIG>.

<FIG> illustrates aspects with respect to communicating the UL report signal <NUM>. <FIG> is a signaling diagram schematically illustrating communication between the UE <NUM> and the BS <NUM>.

Initially, at <NUM>, a capability control message <NUM> is communicated from the UE <NUM> to the BS <NUM>. The capability control message <NUM> is optional. The capability control message <NUM> may not only be employed in connection with the scenario as illustrated by <FIG>, but may alternatively or additionally also be employed in connection with the other scenarios illustrated herein, e.g., in connection with the scenario of <FIG> or <FIG>.

For example, the capability control message <NUM> may be indicative of whether the UE <NUM> supports receiving the DL signal <NUM> while operating in disconnected mode <NUM>, <NUM>. The capability control message <NUM> could also be indicative of at least one of the device could category of the UE <NUM> and the reliability category associated with the UE <NUM>. The capability control message <NUM> could be transmitted during RRC setup or using a RRC control message in connected mode <NUM>, <NUM>.

Then, based on such information that may be included in the capability control message <NUM>, the BS <NUM> can appropriately allocate time-frequency resource elements <NUM> to the transmission of the UL report signal <NUM>. For example, the time offset <NUM> between adjacent transmit timeslots <NUM> can be set in accordance with the information included in the capability control message <NUM>.

These time-frequency resource elements <NUM> may be dedicated to the UE <NUM> such that interference or collision by one or more further UEs attempting to transmit on these resources is avoided. The time-frequency resource elements <NUM> could also be shared between multiple UEs.

At <NUM>, the BS <NUM> transmits a DL control message <NUM>. The DL control message <NUM> is optional. The DL control message <NUM> may not only be employed in the scenario of <FIG>, but also in connection with the other examples described herein.

The DL control message <NUM> generally includes configuration information for configuring the monitoring of the connectivity. In the example of <FIG>, the DL control message <NUM> is indicative of the time-frequency resource elements <NUM> scheduled at each transmit timeslots <NUM> for transmission of the respective UL report signal <NUM>. As such, the DL control message <NUM> may include scheduling information for reoccurring time-frequency resource elements <NUM>. Alternatively or additionally, the DL control message <NUM> may also be indicative of the type of DL signal <NUM> to be used when monitoring the connectivity of the UE <NUM>. The DL control message <NUM> may be, generally, indicative of the repetitive probing schedule and/or the repetitive reporting schedule. The DL control message <NUM> may be generally indicative of a codebook for reporting the received property of one or more DL control message <NUM> in a compressed format. For example, the DL control message <NUM> may be indicative of a threshold of unsuccessful reception attempts which is used when reporting to the network <NUM>. The DL control message <NUM> may be indicative of reachability levels, e.g., the probability of missed communication, that is acceptable for the UE <NUM>.

<NUM> corresponds to <NUM>. <NUM> corresponds to <NUM>.

Reception of DL signals <NUM> is not illustrated in <FIG> for sake of simplicity.

At the transmit timeslot <NUM>, the UE <NUM> uses one of the previously allocated time-frequency resource elements <NUM> to transmit the UL report signal <NUM> at <NUM> (the inset of <FIG> illustrates a time-frequency resource mapping/grid defined in frequency and time domain and the black-filled time-frequency resource elements which are allocated to the transmission of the UL report signal <NUM>; the time-frequency resource mapping may be defined by an Orthogonal Frequency Division Multiplexing modulation scheme).

By using previously allocated time-frequency resource elements <NUM> to transmit the UL report signal <NUM> while the UE is operating in idle mode <NUM> or, generally, in disconnected mode, it becomes possible to avoid frequent re-establishment of the data connection <NUM> which is generally resource expensive and allocates significant overhead on the wireless link <NUM>. At the same time, the UL report signal <NUM> may be transmitted at a comparably high frequency of occurrence such that the accuracy of monitoring the connectivity of the UE <NUM> is high.

<FIG> illustrates aspects with respect to the UL report signal <NUM>. In the example of <FIG>, the UL report signal <NUM> is indicative of the receive properties for a plurality of previously received DL signals <NUM>. In particular, the UL report signal <NUM> indicates for each one of a plurality of DL signals <NUM> if the respective DL signal <NUM> has been correctly received ("+" in <FIG>) or has not been correctly received ("-" in <FIG>). While the scenario <FIG> offers comparably large information depth to be processed by the network <NUM>, also the size of the UL report signal <NUM> is comparably large due to individually reporting one each receive DL signal <NUM>.

<FIG> illustrates aspects with respect to the UL report signal <NUM>. In the example of <FIG>, the UL report signal <NUM> is indicative of statistics of receiving multiple DL signals <NUM>. In particular, in the example of <FIG>, the UL report signal <NUM> illustrates a ratio of unsuccessful reception attempts of the plurality of DL signals if compared to the total number of reception attempts. For example, the number of unsuccessful reception attempts may be determined based on knowledge of the repetition rate with which the DL signals <NUM> are communicated according to a predefined pattern (cf. The scenario of <FIG> reduces the size of the UL report signal <NUM> if compared to the scenario <FIG>.

<FIG> illustrates aspects with respect to the UL report signal <NUM>. In the example of <FIG>, the UL report signal is indicative of statistics of receiving multiple DL signals <NUM>. In particular, in the example of <FIG>, the UL report signal <NUM> is indicative of a number of unsuccessful reception attempts of the plurality of DL signals <NUM>. In this example, the <NUM>-bit UL report signal <NUM> is indicative of whether the number of unsuccessful reception attempts is larger or smaller than the predefined threshold. For example, the predefined threshold may be defined in accordance with an initial control message <NUM>, i.e., as part of a respective codebook (cf. The scenario <FIG> further reduces the size of the UL report signal <NUM> if compared to the scenarios of <FIG>.

For example, the UL report signal <NUM> of <FIG> may be selectively transmitted on-demand if limited connectivity is identified, e.g., because the number of unsuccessful reception attempts exceeds the predefined threshold. By such selective transmission of the UL report signal <NUM> depending on the receive property of the at least one DL signal <NUM>, it becomes possible to reduce control signaling overhead on the wireless link <NUM>.

Such a scenario using a <NUM>-bit UL report signal <NUM> may be, in particular, desirable when using predefined time-frequency resource elements <NUM> that are allocated for use by the UE <NUM> and transmitting the UL report signal what <NUM> while operating in a disconnected mode <NUM>, <NUM>. This is because in such a scenario, typically, the overhead imposed on the wireless link <NUM> is to be reduced due to the number of UEs simultaneously registered with the in a specific cell.

<FIG> illustrates aspects with respect to triggering a countermeasure depending on the connectivity of the UE <NUM>. <FIG> is a signaling diagram schematically illustrating communication between the UE <NUM> and the BS <NUM>.

At <NUM>, the UE <NUM> determines a receive property of previously received DL signals <NUM> (not illustrated in <FIG> for sake of simplicity).

Then, at <NUM>, the UL report signal <NUM> is transmitted by the UE <NUM> and received by the BS <NUM>. For example, the UL report signal <NUM> could be communicated using the data connection <NUM>, i.e., by previously setting up the data connection <NUM> (not illustrated in <FIG>). Alternatively, it would also be possible that the UL report signal <NUM> is communicated using reoccurring time-frequency resource elements <NUM> without transitioning operation of the UE <NUM> from the disconnected more <NUM>, <NUM> to a connected mode <NUM>, <NUM>.

Based on the UL report signal <NUM> received at <NUM>, the BS <NUM> selectively triggers one or more countermeasures for facilitating the connectivity with the UE <NUM>. Hence, in response to receiving the UL report signal <NUM> at <NUM>, one or more such countermeasures may be triggered or may not be triggered, depending on the connectivity.

Generally, there is a wide range of potential countermeasures conceivable. In the specific example of <FIG>, the countermeasure includes transmitting a DL control signal <NUM> from the BS <NUM> to the UE <NUM> at <NUM>. The DL control signal <NUM> is indicative of the limited connectivity of the UE <NUM>. For transmitting the DL control signal <NUM>, it would be possible that the UE <NUM> - by means of paging - is transitioned into the connected mode <NUM>, <NUM> (not illustrated in <FIG>).

Based on the DL control signal <NUM>, the UE <NUM> may then provide notification of the limited connectivity to an application layer implemented by a transmission protocol stack at the UE <NUM>, <NUM>. Therefore, one or more applications that rely on low-latency and high-connectivity communication between the UE <NUM> and the BS <NUM> may be timely informed of the limited connectivity; these applications may then trigger further countermeasures, if required. For example, these applications could transition into a protected mode or the like.

Countermeasures that may be employed in connection with the various examples described herein are not limited to the communication of the DL control signal <NUM> is illustrated in connection with <FIG>. Alternatively or additionally, it would be possible that one or more of the following countermeasures are triggered: increasing a repetition level of a coverage enhancement (CE) policy for communicating between the UE <NUM> and the network <NUM>; triggering cell re-selection or handover of the UE <NUM> to a further BS of the network; and adjusting beamforming parameters for communicating between the UE <NUM> and the network <NUM>.

A comparably large coverage can be achieved by CE. CE is envisioned to be applied for MTC and NB-IOT. A key feature of the CE is to implement multiple transmission repetitions of a signal, e.g., corresponding to encoded data or a random access preamble. Here, each repetition may include the same redundancy version of the encoded data. The repetitions may be "blind", i.e., may not be in response to a respective retransmission request that may be defined with respect to a HARQ protocol. Rather, repetitions according to CE may be preemptive. Examples are provided by the 3GPP Technical Report (TR) <NUM> version <NUM>. <NUM> (<NUM> - <NUM>), section <NUM>. By employing CE, a likelihood of successful transmission can be increased even in scenarios of poor conditions of communicating on a corresponding wireless link. Thereby, the coverage of networks can be significantly enhanced - even for low transmission powers as envisioned for the MTC and MB-IoT domain. Thus, according to examples, a signal is redundantly communicated using a plurality of repetitions. The count of repetitions is defined by the repetition level of the CE policy. The signal may be encoded according to one and the same redundancy version: Hence, the same encoded version of the signal may be redundantly communicated a number of times according to various examples. Each repetition of the plurality of repetitions can include the signal encoded according to the same redundancy version, e.g., redundancy version <NUM> or redundancy version <NUM>, etc. Then, it is possible to combine the plurality of repetitions of the encoded signal at the receiver side. Such combination may be implemented in analog or digital domain, e.g., in the baseband. The combination yields a combined signal. Then, the decoding of the encoded signals can be based on the combined signal. Thus, by aggregating the received information across the multiple repetitions, the probability of successfully decoding of the encoded signal increases.

Beamforming may rely on a phased array of antennas. Antenna weights may define the phase and amplitude relationship between each one of the antennas. Thereby, a well-defined spatial profile for transmitting and/or receiving may be set. Spatial multiplexing becomes possible.

<FIG> is a flowchart of a method according to various examples. For example, the method according to <FIG> may be executed by the control circuitry <NUM> of the UE <NUM>, e.g., based on respective program code loaded from the memory <NUM> (cf.

At <NUM>, one or more DL signals are received. The one or more DL signals may be one or more of an information block, a paging signal, or any other signal transmitted by a BS. The DL signals may be directed to the receiving UE; or may be directed to another UE. For example, the DL signal may be received in a receive timeslot of a repetitive probing schedule (cf. It would be possible that, per receive timeslot, multiple DL signals are received (cf.

At <NUM>, a receive property or multiple receive properties of the one or more DL signals are determined. For example, a signal strength, signal-to-noise ratio, or a decoding reliability may be considered. This receive property may then be stored, for further use in connection with an UL report signal. It would be possible to store / update statistics of the receive property.

At <NUM>, it is checked whether a further DL signal is to be received. This check may be in accordance with a reporting schedule that may be predefined. Alternatively or additionally, it could also be checked if the current receive properties indicate non-limited connectivity. If one or more DL signals are to be further received, then <NUM> - <NUM> are re-executed in a further iteration.

If, at <NUM>, it is determined that there is no further DL signal to be received - e.g., because limited connectivity has been detected and/or because a reporting schedule (cf. <FIG>) requires reporting -, then, at <NUM>, an UL reports signal is transmitted. The UL report signal may be transmitted in a transmit timeslot of a reporting schedule. A data connection may be set up for transmitting the UL report signal or pre-allocated time-frequency resource elements may be used (cf. <FIG> and <FIG>).

The UL report signal can be indicative of the previously determined receive properties of the receive DL signals. For example, the UL report signal could be indicative of statistics of the receive properties (cf.

Generally, transmitting the UL report signal is optional. In some examples, the UE may locally detect limited connectivity and, then, may perform one or more countermeasures to facilitate connectivity locally.

<FIG> is a flowchart of a method according to various examples. For example, the method according to <FIG> may be executed by the control circuitry <NUM> of the BS <NUM>, e.g., based on respective program code loaded from the memory <NUM> (cf.

First, at <NUM>, one or more DL signals are transmitted. <NUM> is inter-related with <NUM>. The DL signals may be transmitted in accordance with the repetitive probing schedule implemented at the receiving UE; then, knowledge of the repetitive probing schedule is to be provided at the network side. Alternatively, the DL signals may be anyway transmitted, e.g., if they are not specifically directed to the receiving UE. The DL signals may be transmitted at a given repetition rate (cf.

At <NUM>, an UL report signal is received. <NUM> may be inter-related with <NUM>. The UL report signal may be received in accordance with a repetitive reporting schedule, e.g., in transmit timeslots of the repetitive reporting schedule (cf.

Based on information included in the UL report signal, at <NUM>, it can be judged whether a countermeasure is to be triggered. The countermeasure may be triggered if the connectivity of the UE is limited. If it is judged that the countermeasure is to be triggered, then at <NUM>, the countermeasure is triggered.

Various countermeasures are conceivable. For example, a DL control message may be transmitted from the BS to the UE; the DL control message may be indicative of the limited connectivity. Then, the application layer of the transmission protocol stack implemented by the UE <NUM> may be notified accordingly (cf. Other countermeasures may include the adjustment of the repetition level of the CE policy; beamforming parameters; and reselection of the sun on which the UE comes or is connected to.

Summarizing, above, techniques have been described which enable to monitor the connectivity of a UE in a lean and efficient manner. In particular, if compared to application layer-based implementations where the application repeatedly "pings" the UE-network connection, significantly reduced control signaling overhead may be achieved. Furthermore, the power consumption may be reduced. Furthermore, the various parameters of such techniques can be flexibly defined, e.g., the type and/or frequency of occurrence of DL signals for which reception attempts are undertaken. Thereby, the radio access network and/or the core network, and thereby, the operator, may have control of the UE-type requirements and the reachability performance.

While above various scenarios have been described in which the connectivity of the UE is monitored using DL signals, in other scenarios, it would also be possible that the connectivity of the UE is at least partially monitored using UL signals. For example, the UL signals may be transmitted by the UE while the UE is operating in the disconnected mode in which the data connection is not set up between the UE and the network. In such a scenario, it may be possible that the UL signals are transmitted using predefined time-frequency resource elements of the UE. For example, the network, e.g. one or more BSs, may monitor such UL signals and determine whether the connectivity is limited or not. Further a network node may transmit a DL report signal to the UE based on such monitoring of UL signals.

For further illustration, above various examples have been described in which an UL report signal indicative of a receive property of at least one DL signal is transmitted in accordance with a repetitive probing schedule. This is optional. In other examples, the UL report signal may be transmitted on-demand, e.g., if the UE determines limited connectivity based on the receive property. Thus, no pre-defined or fixed reporting schedule may be implemented in such an on-demand scenario.

For still further illustration: Above, various scenarios have been described in which the UE transmits an UL report signal to the BS. Then, the limited connectivity of the UE can be monitored at the network, e.g., at the BS. The network may trigger appropriate countermeasures. However, in other examples, other distributions of logic between the UE and the network are conceivable. For example, it would be possible that the UE, based on the receive property of at least one DL signal determines that the connectivity is limited. Then, the UE may take appropriate countermeasures, e.g., adjusting beamforming parameters, informing an application layer of the transmission protocol stack, etc.. In particular in such a scenario, and thus generally, it may even not be required to transmit the UL report signal to the network.

Claim 1:
A method of operating a communication device (<NUM>), comprising:
- while the communication device (<NUM>) operates in a disconnected mode (<NUM>, <NUM>) in which a data connection (<NUM>) is not set-up between the communication device (<NUM>) and a network (<NUM>), receiving at least one downlink signal (<NUM>) transmitted by a base station (<NUM>) of the network (<NUM>),
- determining a receive property of the at least one downlink signal (<NUM>) based on said receiving, and
- transmitting an uplink report signal (<NUM>) indicative of the receive property of the at least one downlink signal (<NUM>),
wherein the receive property comprises at least one of a signal strength, signal-to-noise ratio, an error rate of decoding a plurality of downlink signals (<NUM>), or a decoding reliability,
wherein the at least one downlink signal (<NUM>) comprises a plurality of downlink signals (<NUM>),
wherein the plurality of downlink signals (<NUM>) are received in receive timeslots (<NUM>) of a repetitive probing schedule,
wherein the receive timeslots (<NUM>) are coincident in time domain with paging occasions (<NUM>), and
characterized in that
the repetitive probing schedule is time-aligned with a discontinuous reception cycle of the disconnected mode (<NUM>, <NUM>) such that not every on duration (<NUM>) of the discontinuous reception cycle includes a receive timeslot (<NUM>) of the repetitive probing schedule.