Patent Description:
In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or user equipments (UE), communicate via a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, with each service area or cell area being served by a radio network node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a gNodeB, a NodeB, or an eNodeB. A service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with wireless devices within range of the radio network node.

A Universal Mobile Telecommunications System (UMTS) is a third generation (<NUM>) telecommunication network, which evolved from the second generation (<NUM>) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UTRAN, several radio network nodes may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural radio network nodes connected thereto. This type of connection is sometimes referred to as a backhaul connection. The RNCs and BSCs are typically connected to one or more core networks.

Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (<NUM>) network, have been completed within the <NUM>rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (<NUM>) network. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of an RNC are distributed between the radio network nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially "flat" architecture comprising radio network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio network nodes, this interface being denoted the X2 interface.

Reduction of power consumption is important for wireless devices using battery or an external power supply and its importance increases with the continued growth of device populations and more demanding use cases. The importance can be illustrated by the following scenarios, e.g.:.

To facilitate reduction of power consumption in the wireless device, 3GPP defined Discontinuous reception (DRX) operation for wireless devices in Radio Resource Control (RRC) states or modes such as RRC_CONNECTED state or mode and RRC_IDLE state or mode, and recently also defined eDRX operation for wireless devices in RRC_CONNECTED mode and RRC_IDLE mode in LTE, as well as eDRX operation for wireless devices in RRC_IDLE mode in UTRA.

To reduce power consumption in radio network nodes such as eNodeBs, a Work Item (Wl) on network-based Cell-specific Reference Signal (CRS) mitigation was approved in RP-<NUM>, "New Work Item on UE requirements for network-based CRS mitigation for LTE", Ericsson, 3GPP RAN#<NUM>, June <NUM>.

Right from the start in Release <NUM> (Rel-<NUM>), LTE has been designed to rely on CRSs, which are transmitted using full system bandwidth and in all downlink (DL) subframes of an LTE radio frame. CRS serves quite many important purposes for wireless devices to perform measurements such as for cell search, cell mobility, time/frequency synchronization, channel estimation and radio resource management.

However, currently CRS is transmitted independently of the actual load in the network or cell and as such it causes a considerable interference floor in cellular networks. Especially in times of low and medium network load, transmitting less CRS leads to lower inter-cell interference levels, which directly results in significantly higher data rates for the wireless devices in the network. Network-based CRS mitigation is especially powerful when being combined with higher order modulation, e.g., <NUM> Quadrature Amplitude Modulation (QAM), since the cell coverage area for higher order modulation is then significantly increased. In addition, the always-on CRS transmissions require radio network nodes to stay 'on' all the times, whereas network-based CRS mitigation allows radio network nodes to save energy.

Removing CRS completely, e.g., as it was done for DL Licensed Assisted Access (LAA) using Frame Structure <NUM> and as it has been envisioned for the <NUM> New Radio, (NR) would have the greatest effect but it renders the LTE carrier non-backwards compatible meaning that legacy wireless devices would not be able to use such a carrier. However, CRS can also be reduced cautiously and selectively such that legacy wireless devices can still be served and that inter-cell interference can be significantly reduced.

The approved WI on network-based CRS mitigation also enable reduction of inter-cell interference caused by CRS see RP-<NUM>, "New Work Item on UE requirements for network-based CRS mitigation for LTE", Ericsson, 3GPP RAN#<NUM>, June <NUM>.

For frequency domain CRS reduction one can distinguish between RRC IDLE and RRC CONNECTED mode operation. For supporting wireless devices in IDLE mode, CRS can be reduced to the inner <NUM> physical resource blocks (PRBs) as wireless devices can be configured to only use those PRBs for cell selection. However, during paging occasions, system information transmissions, and random access windows CRS has to be transmitted using full bandwidth. For supporting wireless devices in CONNECTED mode, also known as CONNECTED state, CRS has to be transmitted using full bandwidth whenever a UE is active. But for instance during (e)DRX sleep periods CRS is not needed and can be reduced.

Frequency domain CRS reduction can be accompanied by time domain CRS reduction by means of configuring Multi Broadband Single Frame Network (MBSFN) subframes, which contain CRS only in <NUM> or <NUM> out of <NUM> orthogonal frequency division multiplexing (OFDM)-symbols.

<FIG> illustrates an example operation with network-based CRS mitigation, where "muted CRS" refers to using the shortened CRS bandwidth, center <NUM> Resource Blocks (RB). Thus, CRS are periodically transmitted over a reduced bandwidth during wireless device inactive periods and over full bandwidth during wireless device active periods. There may also be a warm-up period before the wireless device active period, and a cool-down period after the wireless device active period, when transmission of CRS over full bandwidth may be required.

In carrier aggregation (CA) operation the wireless device is able to receive and/or transmit data to and from more than one serving cells. In other words, a CA capable wireless device can be configured to operate with more than one serving cell. The carrier of each serving cell is generally called a component carrier (CC). In simple words the component carrier (CC) means an individual carrier in a multi-carrier system. The term carrier aggregation (CA) is also called, e.g. interchangeably called, "multi-carrier system", "multi-cell operation", "multi-carrier operation", "multi-carrier" transmission and/or reception. This means that the CA is used for transmission of signaling and data in the uplink and downlink directions. One of the CCs is designated as the primary component carrier (PCC) or simply primary carrier or even anchor carrier. The remaining ones are designated as secondary component carriers (SCC) or simply secondary carriers or even supplementary carriers. The serving cell is interchangeably called primary cell (PCell) or primary serving cell (PSC). Similarly the secondary serving cell is interchangeably called secondary cell (SCell) or secondary serving cell (SSC).

In another multicarrier operation called dual connectivity (DC), the wireless device is configured with a Master Cell Group (MCG) and a Secondary Cell Group (SCG). Cell Group (CG) is a group of serving cells associated with either master radio network node such as a master eNB (MeNB) or secondary radio network node such as a secondary eNB (SeNB). Master Cell Group (MCG) is a group of serving cells associated with the MeNB, comprising the PCell and optionally one or more SCells. Secondary Cell Group (SCG) is a group of serving cells associated with the SeNB comprising PSCell (Primary Scell) and optionally one or more SCells.

The purpose of radio link monitoring (RLM) is to monitor a radio link quality of a serving cell of the wireless device and to use that information to decide whether the wireless device is in in-sync or out-of-sync with regards to that serving cell. In LTE RLM is carried out by the wireless device performing measurement on downlink reference symbols, such as CRS, in RRC_CONNECTED mode. If results of the RLM indicate a number of consecutive out of sync (OOS) indications then the wireless device may start a radio link failure (RLF) procedure and may declare RLF after the expiry of an RLF timer, e.g. T310. The actual wireless device procedure is carried out by comparing the estimated downlink reference symbol measurements to some target Block Error Rate (BLER), Qout and Qin. Qout and Qin correspond to BLER of hypothetical Physical Downlink Control Channel (PDCCH)/ Physical Control Format Indicator Channel (PCFICH) transmissions from the serving cell. Examples of Qout and Qin are <NUM>% and <NUM>% respectively.

The current RLF procedure in LTE has two phases, as depicted in <FIG>. The first phase starts upon radio problem detection and leads to radio link failure detection. The second phase, e.g. Radio Resource Control (RRC) recovery, starts upon radio link failure detection or handover failure and leads to RRC_IDLE mode in case the RRC recovery fails.

For single carrier and CA, re-establishment is triggered when the PCell experiences RLF. The wireless device does not monitor the RLF of SCells, which are monitored by the radio network node.

For Dual Connectivity (DC), the first phase of the radio link failure procedure is supported for PCell and PSCell. Re-establishment is triggered when PCell experiences RLF. However, upon detecting RLF on the PSCell, the re-establishment procedure is not triggered at the end of the first phase. Instead, the wireless device informs the radio link failure of PSCell to the MeNB.

RLF can be triggered by layer <NUM> (L1), a. physical layer or PHY, or layer <NUM> (L2), which is then reported to layer <NUM> (L3). RLM is responsible for L1-triggering, upon receiving a number (N310) of consecutive "out-of-sync" indications from lower layers and no recovery, no "in-sync" indication. L2-triggering may be, e.g., upon indication from RLC that the maximum number of retransmissions has been reached or upon random access problem indication from media access control (MAC).

RLM is performed based on CRS, at least once every radio frame, when not configured with DRX, or periodically with DRX cycle, when configured with DRX, over the full cell bandwidth which is also the control channel bandwidth, e.g. PDCCH and PCFICH.

Upon start of T310 timer or T313 timer as specified in clause <NUM>. <NUM> in TS <NUM> v. <NUM> , the wireless device shall monitor the link of PCell or PSCell for recovery using the evaluation period and Layer <NUM> indication interval corresponding to the non-DRX mode until the expiry or stop of T310 timer or T313 timer. The transmitter power of the wireless device shall be turned off within <NUM> after expiry of T310 timer and the transmitter power of PSCell, if configured, shall be turned off within <NUM> after expiry of T313 timer as specified in clause <NUM>. <NUM> in TS <NUM> v. T310 is also called the RLF timer in that the RLF procedure starts upon triggering the RLF timer, which is triggered upon receiving N310 number of consecutive out-of-sync indications from its lower layers. When T310 timer expires then the RLF is declared. But T310 timer is reset upon receiving N311 number of consecutive in-sync indications from its lower layers.

Timers T310 and T313 are specified in <NUM> v. <NUM> as follows:.

The timers can have values: ms0, ms50, ms100, ms200, ms500, ms1000, ms2000.

In e.g. lean carrier operation the Bandwidth (BW) of the CRS in a cell can be reduced (e.g. to <NUM> RBs) at some times when there is no wireless device activity requiring full CRS BW. However the network is not always fully aware when and for which procedure the wireless device needs to receive CRS over larger BW or full BW in the cell. The wireless device performance may be degraded or the wireless device may fail certain operations if the CRS bandwidth is reduced in the serving or neighbor cell, especially when the wireless device is not aware of the CRS BW reduction. On the other hand to achieve sufficient system gain, e.g. higher system throughput, the network should not unnecessarily transmit CRS over full or larger BW in the cell. This is particularly challenging for the wireless device configured for multicarrier operation under lean carrier operation, since e.g. CA operation should ensure higher user throughput.

The document <NPL>), discloses when CRS muting can be applied by the network and if/ how this may impact the UE.

An object of embodiments herein is to provide a mechanism for improving performance of the wireless communication network in an efficient manner.

According to an aspect the object is achieved by providing a method performed by a radio network node for handling communication of a wireless device in a wireless communication network. The radio network node is configured to provide a serving cell for the wireless device on a lean carrier where reference signals are transmitted with a bandwidth that is variable between a first bandwidth and a second bandwidth. The second bandwidth is narrower than the first bandwidth, and the wireless device is configured with a discontinuous reception cycle. The radio network node transmits reference signals over a bandwidth that alternates between the first bandwidth and the second bandwidth in accordance with the discontinuous reception cycle configured for the wireless device. The radio network node obtains an indication from the wireless device or from a second radio network node, which indication indicates that a signal strength or quality of the serving cell for the wireless device is below a threshold. The radio network node further transmits, in response to the obtained indication, one or more reference signals over the first bandwidth.

According to another aspect the object is achieved by providing a method performed by a wireless device for handling communication of the wireless device in a wireless communication network. The wireless device is served by a radio network node in a serving cell on a lean carrier where reference signals are transmitted with a bandwidth that is variable between a first bandwidth and a second bandwidth, the second bandwidth being narrower than the first bandwidth. The wireless device is configured with a discontinuous reception cycle. The wireless device receives, on the serving cell, reference signals that are assumed by the wireless device to have been transmitted by the radio network node over a bandwidth that alternates between the first bandwidth and the second bandwidth in accordance with the discontinuous reception cycle. The wireless device measures a signal strength or quality of the serving cell from the radio network node. The wireless device then receives, on the serving cell, one or more reference signals, wherein the wireless device assumes, in response to the measured signal strength or quality being below a threshold, the one or more reference signals to have been transmitted by the radio network node over the first bandwidth.

According to yet another aspect the object is achieved by providing a radio network node for handling communication of a wireless device in a wireless communication network. The radio network node is configured to provide a serving cell for the wireless device on a lean carrier where reference signals are transmitted with a bandwidth that is variable between a first bandwidth and a second bandwidth. The second bandwidth is narrower than the first bandwidth, and the wireless device is configured with a discontinuous reception cycle. The radio network node is configured to transmit reference signals over a bandwidth that alternates between the first bandwidth and the second bandwidth in accordance with the discontinuous reception cycle configured for the wireless device. Furthermore, the radio network node is configured to obtain an indication from the wireless device or from a second radio network node, which indication indicates that a signal strength or quality of the serving cell for the wireless device is below a threshold. The radio network node is further configured to transmit, in response to the obtained indication, one or more reference signals over the first bandwidth.

According to still another aspect the object is achieved by providing a wireless device for handling communication of the wireless device in a wireless communication network. The wireless device is configured to be served by a radio network node in a serving cell on a lean carrier where reference signals are transmitted with a bandwidth that is variable between a first bandwidth and a second bandwidth, the second bandwidth being narrower than the first bandwidth. The wireless device is configured with a discontinuous reception cycle. The wireless device is configured to receive, on the serving cell, reference signals that are assumed by the wireless device to have been transmitted by the radio network node over a bandwidth that alternates between the first bandwidth and the second bandwidth in accordance with the discontinuous reception cycle. The wireless device is configured to measure a signal strength or quality of the serving cell. The wireless device is further configured to receive, on the serving cell, one or more reference signals, wherein the wireless device is configured to assume, in response to the measured signal strength or quality being below a threshold, the one or more reference signals to have been transmitted by the radio network node over the first bandwidth.

It is furthermore provided herein a computer program product comprising instructions, which, when executed on at least one processor, cause the at least one processor to carry out any of the methods above, as performed by the radio network node or the wireless device respectively. It is additionally provided herein a computer-readable storage medium, having stored thereon a computer program product comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any of the methods above, as performed by the radio network node or the wireless device respectively.

Embodiments herein provide a manner of enabling lean carrier operation where the BW of the RS in a cell can be reduced while ensuring that reference signals are provided over a different bandwidth, e.g. a wider bandwidth, when the wireless device experiences or measures signal strength or quality of e.g. a low level. when the radio network node receives indication of RLF the radio network node transmits e.g. CRSs over the full BW. Thereby degradation of the performance due to failed RLM/RLF procedures because of non-available RS, e.g. CRS, can be avoided and thus performance of the wireless communication network as such is improved in an efficient manner.

Embodiments herein relate to communication networks in general. <FIG> is a schematic overview depicting a wireless communication network <NUM>. The communication network <NUM> comprises one or more RANs e.g. a first RAN (RAN1), connected to one or more CNs. The communication network <NUM> may use one or a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, New Radio (NR) of <NUM>, Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/Enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments are applicable to <NUM> and also in further development of the existing communication systems such as e.g. <NUM> and LTE.

In the wireless communication network <NUM>, wireless devices e.g. a wireless device <NUM> such as a mobile station, a non-access point (non-AP) STA, a STA, a user equipment and/or a wireless terminal, are connected via the one or more RANs, to the one or more CNs. It should be understood by those skilled in the art that "wireless device" is a non-limiting term which means any terminal, wireless communication terminal, communication equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or user equipment e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or any device communicating within a cell or service area.

The wireless communication network <NUM> comprises a first radio network node <NUM>, or a radio network node <NUM> for short. The first radio network node <NUM> is exemplified herein as a RAN node providing radio coverage over a geographical area, a first service area <NUM>, of a radio access technology (RAT), such as NR, LTE, UMTS, Wi-Fi or similar. The first radio network node <NUM> may be a radio access network node such as radio network controller or an access point such as a wireless local area network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNodeB), a base transceiver station, Access Point Base Station, base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of serving a wireless device within the service area served by the first radio network node <NUM> depending e.g. on the radio access technology and terminology used and may be denoted as a scheduling node, serving radio network node or primary serving radio network node providing a primary serving cell for the wireless device <NUM>.

The wireless communication network <NUM> may further comprise a second radio network node <NUM>. The second radio network node <NUM> is exemplified herein as a RAN node providing radio coverage over a geographical area, a second service area <NUM>, of a radio access technology (RAT), such as NR, LTE, UMTS, Wi-Fi or similar. The second radio network node <NUM> may be denoted as a secondary node, secondary serving radio network node providing a secondary serving cell for the wireless device <NUM>. It should be noted that a service area may be denoted as 'cell', beam, beam group or similar to define an area of radio coverage.

It should further be understood that the first and second service area may also be provided by a single radio network node such as the first radio network node <NUM> or the second radio network node <NUM>.

When configured with Discontinuous reception (DRX), the wireless device <NUM> typically performs RLM during the ON duration periods (configured by the network and thus known to the network, which makes it possible to ensure full bandwidth CRS in those subframes), while when not configured with DRX the wireless device <NUM> is required to perform RLM at least once every radio frame (<NUM>), in any DL subframe (and thus not known to the network), which means the network would have to always transmit full-bandwidth CRS when there is at least one wireless device in RRC_CONNECTED mode not configured with DRX.

More specifically, the problem addressed herein is that a wireless device configured with DRX is required to operate in a non-DRX mode, e.g., continuous channel monitoring, when bad link quality is determined, while it is the key assumption for the lean carrier that wireless device in RRC_CONNECTED configured with DRX do not require full bandwidth CRS except for a relatively short period, e.g., <NUM>-<NUM> subframes, warm-up period prior the configured DRX ON duration. This is explicitly stated in the standard as a wireless device behavior requirement:
Upon start of T310 timer or T313 timer as specified in clause <NUM>. <NUM> in TS <NUM> v. <NUM>, the wireless device <NUM> shall monitor the link of PCell or PSCell for recovery using the evaluation period and Layer <NUM> indication interval corresponding to the non-DRX mode until the expiry or stop of T310 timer or T313 timer. The transmitter power of the wireless device <NUM> shall be turned off within <NUM> after expiry of T310 timer and the transmitter power of PSCell if configured shall be turned off within <NUM> after expiry of T313 timer as specified in clause <NUM>. <NUM> in TS <NUM> v.

According to embodiments herein the radio network node <NUM> adapts a bandwidth of a reference signal (RS), e.g. CRS, transmitted in the first cell (cell <NUM>) in which a lean carrier operation is used, based on a radio link quality of cell <NUM> experienced by at least N wireless devices (e.g., N=<NUM>, <NUM>,. , which may be configurable or pre-defined or received in a message from another network node such a controlling network node). In the lean carrier operation considered and exemplified herein, in at least certain time resources cell <NUM> transmits reference signals, e.g. CRS, over a reduced bandwidth, denoted second bandwidth (BW2), and transmits RS over full cell1's BW, denoted first bandwidth (BW1), in another set of time resources; where BW2 < BW1, and where BW1 is the bandwidth of cell <NUM>. Examples of radio link quality are signal quality measurements performed by the wireless device <NUM> on at least signals of cell <NUM> e.g. any one or a combination of: Reference Signal Received Quality (RSRQ), Reference Signal - Signal to Interference plus Noise Ratio (RS-SINR), Signal to Interference plus Noise Ratio (SINR), Reference Signal Received Power (RSRP), Received Signal Strength Indicator (RSSI), etc..

The bandwidth of RS, e.g. CRS, transmitted by the first radio network node <NUM> (e.g., serving BS, MeNB, SeNB, etc.) in cell <NUM> is changed from BW2 to BW1 (BW1>BW2) upon determining that the radio link quality of cell <NUM> experienced by at least one wireless device is below a threshold. Otherwise if radio link quality of cell <NUM> experienced by all the wireless devices in cell <NUM> are equal to or larger than the threshold then the first radio network node <NUM> transmits RS over the reduced BW e.g. BW2. The first radio network node <NUM> configures the wireless device <NUM> to perform radio link measurement on signals of cell <NUM> and report the results to the first radio network node <NUM>. The configured value of threshold (e.g. RS-SINR = -<NUM> dB or RSRQ=-<NUM> dB) corresponds to a radio link quality at which the wireless device <NUM> triggers or is expected to trigger a radio link failure operation. The above rule can be pre-defined or configured at the wireless device <NUM> by the first radio network node <NUM>. The above method will enable the wireless device <NUM> to correctly estimate radio link quality over full BW of cell <NUM> when this wireless device <NUM> triggers or is close to triggering a radio link failure procedure or operation with regards to cell <NUM> with lean carrier operation.

The above rule, which requires cell <NUM> to adapt RS BW based on the wireless device <NUM> estimated radio link quality, is also applied in the wireless device operating in cell <NUM>. For example, the wireless device <NUM> upon triggering a radio link failure operation with regards to cell <NUM> assumes that during the radio link failure procedure, cell <NUM> transmits RS (e.g. CRS) over the full cell1's BW, e.g. BW1. The RS, e.g. CRS, is used by the wireless device <NUM> for performing the radio link monitoring procedure. This assumption in the wireless device <NUM> will enable the wireless device <NUM> to perform RLF operation over the full cell11's BW. This in turn enhances the radio link quality estimated by the wireless device <NUM> during the RLF procedure. This in turn may result in that the wireless device <NUM> may recover from RLF and therefore prevent the loss of the radio link in cell <NUM>.

Embodiments herein relate to methods of adapting reference signal BW configuration based on the reported signal strength or quality and the corresponding methods in the wireless device. Embodiments herein provide: compliance of the lean carrier with legacy wireless device operation; No wireless device performance degradation on a lean carrier or in a cell performing CRS bandwidth adaptation due to failed RLM/RLF procedures because of non-available CRS; and no network performance degradation due to failed RLM/RLF procedures because of non-available CRS.

Furthermore, the lean carrier operation is applied in a cell when the wireless device <NUM> is configured with DRX or eDRX cycle. For example if the wireless device <NUM> is in a Radio Resource Control (RRC) connected state then the serving cell of that wireless device <NUM> transmits RS (e.g. CRS) over the entire bandwidth of the serving cell. In other words during OFF and ON durations of the DRX cycle the RS are transmitted over reduced BW and full BW respectively. This means that the radio network node transmits reference signals over a bandwidth that alternates between a first bandwidth, being used for transmission of reference signals during ON duration periods of the DRX cycle, and a second bandwidth, being used for transmission of reference signals during periods in-between the ON duration periods of the DRX cycle. The periods in-between the ON duration periods of the DRX cycle may be the parts or portions of the OFF duration periods that are not part of any warm-up or cool-down period.

<FIG> is a combined signaling scheme and flowchart according to some embodiments herein relating to a wireless device in a lean carrier operation and being served by a primary and a secondary serving cell.

Action <NUM>. The radio network node <NUM>, <NUM> transmits reference signals over the second bandwidth.

Action <NUM>. The wireless device <NUM> measures a signal strength or quality of the serving cell from the radio network node <NUM>, <NUM>.

Action <NUM>. The wireless device <NUM> may then transmit an indication such as the measurements to the radio network node <NUM>, <NUM>.

Action <NUM>. The radio network node <NUM>, <NUM> determines to switch to the first bandwidth based on the received indication e.g. indicating a RLF.

Action <NUM>. The radio network node <NUM>, <NUM> then transmits RS(s) over the first bandwidth.

The method actions performed by the wireless device <NUM> for handling the communication of the wireless device <NUM> in the wireless communication network <NUM> according to embodiments herein will now be described with reference to a flowchart depicted in <FIG>. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Features performed in some embodiments are marked with a dashed line. The wireless device <NUM> is served by the radio network node in a serving cell on a lean carrier where reference signals are transmitted with a bandwidth that is variable between a first bandwidth and a second bandwidth, the second bandwidth being narrower than the first bandwidth. The wireless device <NUM> is configured with a discontinuous reception cycle and the radio network node transmits reference signals alternately over the first bandwidth and the second bandwidth in accordance with the discontinuous reception cycle configured for the wireless device. The term "alternately" here refers to a manner by which the bandwidth used for transmission of reference signals alternates between the first bandwidth being used for the transmission of reference signals that are transmitted during a first set of time resources and the second bandwidth being used for the transmission of reference signals that are transmitted during a second set of time resources. For example, the reference signals may be transmitted over the first bandwidth during ON duration periods of the discontinuous reception cycle and over the second bandwidth in-between the ON duration periods of the discontinuous reception cycle.

Action <NUM>. The wireless device <NUM> may receive a measurement configuration message from the radio network node for setting up operations of the wireless device.

Action <NUM>. The wireless device <NUM> receives, on the serving cell, reference signals that are assumed by the wireless device <NUM> to have been transmitted by the radio network node alternately over the first bandwidth and the second bandwidth, i.e. with a bandwidth that alternates between the first and second bandwidths, in accordance with the discontinuous reception cycle.

Action <NUM>. The wireless device <NUM> measures a signal strength or quality of the serving cell from the radio network node.

Action <NUM>. The wireless device <NUM> may transmit, in response to the measured signal strength or quality being below a threshold, an indication to the radio network node indicating the measured signal strength or quality. The threshold may be related to a (possible) radio link failure, RLF, e.g. by being set to a level where the wireless device <NUM> triggers, or is close to triggering, a radio link failure (RLF) procedure or operation with regards to the serving cell with lean carrier operation. The indication may be an indication of radio link failure or measurements from the wireless device <NUM>. The wireless device <NUM> may, when the measured signal strength or quality is below the threshold, trigger the radio link failure (RLF) procedure or operation by starting an RLF timer. The wireless device <NUM> may start the RLF timer in response to or shortly after the measured signal strength or quality going below the threshold.

Action <NUM>. The wireless device <NUM> receives, on the serving cell, one or more reference signals, wherein the wireless device <NUM> assumes, in response to the measured signal strength or quality being below the threshold, the one or more reference signals to have been transmitted by the radio network node over the first bandwidth. the wireless device <NUM> may thus assume, in response to the measured signal strength or quality being below the threshold, that the transmission, from the radio network node, of one or more reference signals is made over the first bandwidth. the wireless device <NUM> may assume that the transmission, from the radio network node, of one or more reference signals is made over the first bandwidth over or for at least a duration during which the wireless device will perform an RLF procedure. The expected duration of RLF (T2) may correspond to the RLF timer (e.g. T310 or T313).

The method actions performed by the radio network node, such as the first radio network node <NUM> or the second radio network node <NUM>, for handling the communication of the wireless device in the wireless communication network <NUM> according to embodiments herein will now be described with reference to a flowchart depicted in <FIG>. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some embodiments are marked with dashed boxes. The radio network node is configured to provide a serving cell for the wireless device on a lean carrier where reference signals are transmitted with a bandwidth that is variable between a first bandwidth and a second bandwidth. The second bandwidth is narrower than the first bandwidth, and the wireless device is configured with a discontinuous reception cycle.

Action <NUM>. The radio network node transmits reference signals alternately over the first bandwidth and the second bandwidth, i.e. with a bandwidth that alternates between the first and second bandwidths, in accordance with the discontinuous reception cycle configured for the wireless device <NUM>. the reference signals are transmitted over the first bandwidth during ON duration periods of the discontinuous reception cycle and over the second bandwidth in-between the ON duration periods of the discontinuous reception cycle.

Action <NUM>. The radio network node <NUM>, <NUM> obtains the indication from the wireless device <NUM> or from a another or second radio network node, e.g. the respective other one of the first radio network node <NUM> or the second radio network node <NUM>, which indication indicates that a signal strength or quality of the serving cell for the wireless device <NUM> is below the threshold. The threshold may be related to a possible RLF, e.g. by being set to a level where the wireless device <NUM> triggers, or is close to triggering, a radio link failure (RLF) procedure or operation with regards to the serving cell with lean carrier operation. The indication may be an indication of radio link failure. The indication may e.g. be measurements from the wireless device <NUM>, an RLF flag, or may be uplink (UL) signals that the radio network node performs measurements on.

Action <NUM>. The radio network node may determine to transmit the one or more reference signals over the first bandwidth or the second bandwidth based on the indication.

Action <NUM>. The radio network node transmits, in response to the obtained indication, one or more reference signals over the first bandwidth. the one or more reference signals over the first bandwidth over or for at least a duration during which the wireless device will perform an RLF procedure. The radio network node <NUM> may transmit one or more reference signals over the first bandwidth when the signal strength or quality is below the threshold.

Some actions performed by the wireless device <NUM> and the radio network node <NUM> are summarized below:
Methods performed by the wireless device <NUM> served by the first radio network node <NUM> and may also be served by the second radio network node <NUM>, see <FIG>, comprise:.

The wireless device <NUM> may while performing the actions above, also be required to meet one or more requirements related to RLM/RLF performance, e.g., correctly and in a timely manner indicate in-sync, out-of-sync, or declare RLF, without delays due to BW changes.

Thus, the wireless device <NUM> performs the configured signal quality measurement and may compare the results of the measurement with H. Based on the results comparison the wireless device <NUM> may perform the following actions:
If the signal quality measured on the first cell is below the threshold, H, then the wireless device <NUM> performs the following task:.

<FIG> is a flowchart depicting a method performed by the radio network node such as the first radio network node <NUM> for handling communication of the wireless device <NUM> in the wireless communication network <NUM>. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some embodiments are marked with dashed boxes.

Action <NUM>. The first radio network node <NUM> may configure at least N (e.g., N=<NUM>, <NUM>,. ; can be pre-defined or configurable by this or another radio network node) wireless devices <NUM> to perform a signal quality measurement on signals transmitted by the first cell <NUM>, which is associated with lean carrier operation so that cell transmits reference signals (e.g., CRS) over a reduced BW at least during a subset of time resources. Thus, the radio network node <NUM> configures one or more wireless devices to perform one or more signal quality measurements on signals transmitted by the first cell (cell <NUM>). Cell <NUM> operates under lean carrier operation e.g. RS (e.g. CRS) are transmitted over the first bandwidth e.g. reduced BW (BW2) in DRX OFF and over the second bandwidth e.g. full cell BW (BW1) in DRX ON. Examples of the first cell <NUM> may be PCell, PSCell etc. The configuration message sent to the wireless device <NUM> may further contain additional information e.g. type of signal quality measurement (e.g. RS-SINR, RSRQ etc), carrier frequency of cell <NUM>, cell ID of cell <NUM>, type of event comparing cell <NUM> signal quality, signal quality threshold (H), type of reporting (e.g. period or event triggered), first bandwidth e.g. reduced bandwidth BW2, etc..

The term signal quality is also interchangeably called as radio link quality and it can comprise any of the metrics described herein, e.g.:.

The radio network node may further determine the parameter H before transmitting the measurement configuration message to the wireless device <NUM>. The value of H may be associated with triggering of a radio link failure procedure by a wireless device in the first cell <NUM>. Threshold or Parameter H may also depend on the coverage level, e.g., H1 for normal coverage and H2 (H2<H1) for extended coverage. For example, when the measured signal quality of the cell <NUM> falls below H, then the wireless device <NUM> is expected to start a radio link failure procedure. The value of H can be different for different types of signal quality measurement. For example H can be -<NUM> dB for RS-SINR while it can be -<NUM> dB for RSRQ. In one example the first radio network node <NUM> configures the wireless device <NUM> to report the results when the measured signal quality of cell <NUM> falls below H (otherwise not reporting) e.g. event triggered reporting. This mechanism is used to reduce signaling overheads. In another example the radio network node <NUM> configures the wireless device <NUM> to periodically report the results of the measured signal quality of the cell <NUM> to the first radio network node <NUM>. In this approach the comparison between the measured signal quality reported to the first radio network node <NUM> and the threshold, H, is performed by the first radio network node <NUM> itself.

Action <NUM>. The radio network node receives from the at least one or N wireless devices, i.e. at least the wireless device <NUM>, the indication of one or more results of the measurement of signal strength or quality performed by the wireless device <NUM> on signals of the first cell <NUM>. The indication may be the actual measurement value or data stating that the measurement is below the threshold.

Action <NUM>. The radio network node may optionally then determine to transmit one or more reference signals such as CRS on the first or second bandwidth based on the indicated signal strength or quality. For example, upon determining that for N wireless devices (one or more wireless devices e.g. the wireless device <NUM>):.

Action <NUM>. The radio network node transmits the one or more RSs over the first or the second BW as determined. The radio network node may reconfigure the first cell <NUM> to transmit RS over the first bandwidth (BW2) after at least a certain time DeltaT and/or when the wireless device <NUM> has terminated or is expected to terminate the RLF procedure, where BW2 < BW1 e.g. BW1 = <NUM> RBs, BW2 = <NUM> RBs. Thus, the first bandwidth is smaller than the second bandwidth. Thus, in case cell <NUM> is configured to transmit RS over full BW (as described above) then after the wireless device <NUM> has terminated or is expected to terminate the RLF, the radio network node may further reconfigure the cell <NUM> to reduce the RS BW (first BW e.g. BW2).

As an example of what is stated in action <NUM>, if the signal quality measured on cell <NUM> is below the threshold, H, as determined by the wireless device <NUM> or the radio network node, then the radio network node may perform the following task:.

But if the signal quality measured on cell <NUM> is equal to or above the threshold, H, (as determined by the wireless device <NUM> or the radio network node), then the radio network node performs the following task:.

In a further embodiment, the radio network node may determine that the signal strength or quality experienced by one or more wireless devices is below the threshold and indicates to the first radio network node the need to increase the CRS bandwidth in at least one of the first and the second radio network node.

For example, MeNB determines RLF for the wireless device <NUM> on the radio link with the served by SeNB, and instructs SeNB to increase its CRS bandwidth; SeNB receives an indication from MeNB that at least one SeNB's wireless device <NUM> experiences RLF and increases its CRS bandwidth; MeNB may also increase its bandwidth if the radio link quality for the wireless device <NUM> with MeNB is below a threshold.

In another example, the second radio network node <NUM> indicates via X2 a high load to the first radio network node. In yet further embodiment, the N wireless devices, for which the radio link quality is determined to be poor, comprise the wireless device <NUM> with specific properties, e.g., software, hardware, or middleware release (below LTE release X), wireless devices not indicating its capability of a certain type, e.g., to determine or operate under reduced CRS bandwidth, MTC wireless devices, MTC wireless devices with specific coverage level (e.g., enhanced coverage or CE mode B), etc..

In the above embodiments the radio network node may determine the signal quality threshold, H, based on one or more following mechanisms:
In one example the radio network node obtains statistics of the signal quality measurement results reported by the wireless device <NUM> at which the wireless device <NUM> triggers radio link failures and uses them to set the value of H. For examples such statistics can be obtained during field tests or during live network operation. The radio network node may set H to the reported signal quality at which X% of RLF occurs e.g. X = <NUM>%.

In another example the radio network node uses the load (Lm) in a measurement cell within the signal quality measurement bandwidth and also the load (Lt) in entire cell bandwidth to determine the value of H. The signal quality measurement bandwidth is known to the radio network node since it is configured at the wireless device <NUM> by the radio network node. Examples of measurement BW are <NUM> RBs, <NUM> RBs etc. The radio network node may determine the load for each resource block over cell BW or within the measurement BW by receiving load information from the cell e.g. over X2 interface between network nodes, internally if the cell is served by the radio network node etc. Typically the radio network node configures the signal quality measurement BW to be equal to BW2 (e.g. reduced BW) when RS muting is used in the network. Examples of load are average DL transmit power per resource block (RB) in the cell, average DL bit rate or throughput per resource block in the cell etc. For example the value of H = F(G, Lm, Lt, K) where G is a fixed value (e.g. G = -<NUM> dB, K is a scaling factor, where a special case is K = <NUM>). As an specific example H = G + K*log10(Lt/Lm). The signal quality is measured over measurement BW but radio link monitoring is performed by the wireless device <NUM> over the cell BW. Therefore this scheme enables the radio network node to more accurately determine when the wireless device <NUM> actually triggers the RLF especially if the measurement BW is smaller than the cell BW, and the cell load is not evenly distributed across the cell BW (e.g. load is different in different RBs).

<FIG> is a block diagram depicting the (first or second) radio network node <NUM>, <NUM>, in two embodiments, for handling communication of the wireless device <NUM> in the wireless communication network <NUM>. The radio network node is configured to provide a serving cell for the wireless device on a lean carrier where reference signals are transmitted with a bandwidth that is variable between the first bandwidth and the second bandwidth. The second bandwidth is narrower than the first bandwidth, and the wireless device is configured with a discontinuous reception cycle. The radio network node may provide radio coverage over a first cell transmitting reference signals over the first bandwidth e.g. BW2. The wireless device <NUM> may be served by the radio network node. The wireless device <NUM> may further be served by the secondary cell as a secondary serving cell. The wireless device <NUM> may be served by SCell (i.e. secondary serving cell on SCC) even when SCell is deactivated i.e. SCell is the serving cell regardless of whether it is activated or deactivated.

The radio network node may comprise processing circuitry <NUM>, e.g. one or more processors, configured to perform the methods herein.

The radio network node may comprise a receiving module <NUM>. The radio network node, the processing circuitry <NUM>, and/or the receiving module <NUM> is configured to obtain or receive the indication from the wireless device <NUM> or from a second radio network node, which indication indicates that the signal strength or quality of the serving cell for the wireless device <NUM> is below the threshold. the first radio network node <NUM> may receive the indication from the wireless device <NUM> or from the second radio network node <NUM>, which indication indicates the signal strength or quality of the first and/or second cell for the wireless device, e.g. RSRP, RSSI or just that the value is below/above the threshold. The threshold may be related to a (possible) radio link failure, RLF.

The radio network node may comprise a determining module <NUM>. The radio network node, the processing circuitry <NUM>, and/or the determining module <NUM> may be configured to determine to transmit one or more reference signals such as CRSs over the first bandwidth or the second bandwidth based on the indication.

The radio network node may comprise a transmitting module <NUM>, e.g. a transmitter, a transceiver or similar. The radio network node, the processing circuitry <NUM>, and/or the transmitting module <NUM> is configured to transmit one or more reference signals alternately over the first bandwidth and the second bandwidth, i.e. with a bandwidth that alternates between the first and second bandwidths, in accordance with the discontinuous reception cycle configured for the wireless device <NUM>. The reference signals may be transmitted over the first bandwidth during ON duration periods of the discontinuous reception cycle and over the second bandwidth in-between the ON duration periods of the discontinuous reception cycle. the reference signals may be transmitted over the second bandwidth or the first bandwidth as determined. The second bandwidth is different than the first bandwidth. The radio network node, the processing circuitry <NUM>, and/or the transmitting module <NUM> is further configured to transmit, in response to the obtained indication, one or more reference signals over the first bandwidth, e.g. over or for at least a duration during which the wireless device will perform an RLF procedure.

The radio network node may comprise a configuring module <NUM>. The radio network node, the processing circuitry <NUM>, and/or the configuring module <NUM> may be configured to configure one or more wireless devices such as the wireless device <NUM> to perform one or more signal quality measurements on signals transmitted by the first cell over the first BW and the second BW.

The methods according to the embodiments described herein for the radio network node may be respectively implemented by means of e.g. a computer program product <NUM> or a computer program, comprising instructions, i.e., software code portions, which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the radio network node. The computer program product <NUM> may be stored on a computer-readable storage medium <NUM>, e.g. a disc, a universal serial bus (USB) stick, or similar. The computer-readable storage medium <NUM>, having stored thereon the computer program product, may comprise the instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the radio network node. In some embodiments, the computer-readable storage medium may be a non-transitory computer-readable storage medium.

The radio network node may further comprise a memory <NUM>. The memory comprises one or more units to be used to store data on, such as bandwidth configurations, measurements, serving cells, wireless device information, applications to perform the methods disclosed herein when being executed, and similar. Thus, the radio network node may comprise the processing circuitry and the memory, said memory comprising instructions executable by said processing circuitry whereby said radio network node is operative to perform the methods herein.

<FIG> is a block diagram depicting, in two embodiments, the wireless device <NUM> according to embodiments herein for handling communication of the wireless device <NUM> in the wireless communication network <NUM>. The wireless device is configured to be served by the radio network node in the serving cell on a lean carrier where reference signals are transmitted with a bandwidth that is variable between a first bandwidth and a second bandwidth. The second bandwidth is narrower than the first bandwidth. The wireless device <NUM> is configured with a discontinuous reception cycle and the radio network node is configured to transmit reference signals alternately over the first bandwidth and the second bandwidth, i.e. with a bandwidth that alternates between the first and second bandwidths, in accordance with the discontinuous reception cycle configured for the wireless device, wherein e.g. the reference signals are transmitted over the first bandwidth during ON duration periods of the discontinuous reception cycle and over the second bandwidth in-between the ON duration periods of the discontinuous reception cycle.

The wireless device <NUM> may comprise processing circuitry <NUM>, e.g. one or more processors, configured to perform the methods herein.

The wireless device <NUM> may comprise a measuring module <NUM>. The wireless device <NUM>, the processing circuitry <NUM>, and/or the measuring module <NUM> is configured to measure a signal strength or quality of the serving cell e.g. the signal strength or quality of the first and/or secondary serving cell from the radio network node.

The wireless device <NUM> may comprise a transmitting module <NUM>, e.g. a transmitter or transceiver. The wireless device <NUM>, the processing circuitry <NUM>, and/or the transmitting module <NUM> may be configured to transmit, in response to the measured signal strength or quality being below the threshold, the indication to the radio network node indicating the measured signal strength or quality. The indication may be an indication of radio link failure. The wireless device <NUM>, the processing circuitry <NUM>, and/or the transmitting module <NUM> may be configured to, when the measured signal strength or quality is below the threshold, start the RLF timer.

The wireless device <NUM> may comprise an assuming module <NUM>. The wireless device <NUM>, the processing circuitry <NUM>, and/or the assuming module <NUM> is configured to receive, on the serving cell, reference signals that are assumed by the wireless device <NUM> to have been transmitted by the radio network node alternately over the first bandwidth and the second bandwidth, i.e. with a bandwidth that alternates between the first and second bandwidths, in accordance with the discontinuous reception cycle. The wireless device <NUM>, the processing circuitry <NUM>, and/or the assuming module <NUM> is further configured to receive, on the serving cell, the one or more reference signals, wherein the wireless device <NUM> is configured to assume, in response to the measured signal strength or quality being below the threshold, the one or more reference signals to have been transmitted by the radio network node over the first bandwidth. configured to assume that the transmission, from the radio network node, of one or more reference signals is made over the first bandwidth. The wireless device <NUM>, the processing circuitry <NUM>, and/or the assuming module <NUM> may be configured to assume that the transmission, from the radio network node, of one or more reference signals is made over the first bandwidth over or for at least a duration during which the wireless device will perform an RLF procedure. The wireless device <NUM>, the processing circuitry <NUM>, and/or the assuming module <NUM> may be configured to assume that the transmission, from the radio network node, of one or more reference signals is made over the first bandwidth or the second bandwidth based on the measured signal strength or quality. Thus, the wireless device <NUM> may adapt reception for transmission of the RS over the second bandwidth. The second bandwidth is different than the first bandwidth.

The wireless device <NUM> may comprise a configuring module <NUM>. The wireless device <NUM>, the processing circuitry <NUM>, and/or the configuring module <NUM> may be configured to receive configuring information from the radio network node for setting up the wireless device <NUM> to perform one or more signal quality measurements on signals transmitted on the serving cell over the first BW and the second BW. The wireless device may comprise a receiving module configured to receive transmissions from the radio network node. The assuming module <NUM> may be configured to receive the reference signals and the one or more reference signals via the receiving module.

The methods according to the embodiments described herein for the wireless device <NUM> may be respectively implemented by means of e.g. a computer program product <NUM> or a computer program, comprising instructions, i.e., software code portions, which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the wireless device <NUM>. The computer program product <NUM> may be stored on a computer-readable storage medium <NUM>, e.g. a disc, an USB stick, or similar. The computer-readable storage medium <NUM>, having stored thereon the computer program product, may comprise the instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the wireless device <NUM>. In some embodiments, the computer-readable storage medium may be a non-transitory computer-readable storage medium.

The wireless device <NUM> may further comprise a memory <NUM>. The memory comprises one or more units to be used to store data on, such as BW information, serving cells, applications to perform the methods disclosed herein when being executed, and similar. Thus, the wireless device <NUM> may comprise the processing circuitry and the memory, said memory comprising instructions executable by said processing circuitry whereby said wireless device is operative to perform the methods herein.

As will be readily understood by those familiar with communications design, that functions means or modules may be implemented using digital logic and/or one or more microcontrollers, microprocessors, or other digital hardware. In some embodiments, several or all of the various functions may be implemented together, such as in a single application-specific integrated circuit (ASIC), or in two or more separate devices with appropriate hardware and/or software interfaces between them. Several of the functions may be implemented on a processor shared with other functional components of a radio network node, for example.

Alternatively, several of the functional elements of the processing means discussed may be provided through the use of dedicated hardware, while others are provided with hardware for executing software, in association with the appropriate software or firmware. Thus, the term "processor" or "controller" as used herein does not exclusively refer to hardware capable of executing software and may implicitly include, without limitation, digital signal processor (DSP) hardware, read-only memory (ROM) for storing software, random-access memory for storing software and/or program or application data, and non-volatile memory. Designers of radio network nodes will appreciate the cost, performance, and maintenance trade-offs inherent in these design choices.

Any two or more embodiments described in this document may be combined in any way with each other. Furthermore, in a more general case when the wireless device may need to configure measurement period adaptively to one or more conditions, e.g., channel quality, Ês/Iot, Signal to Interference pule Noise ratio (SINR), received signal quality, total interference or interference on a specific resources or from a specific interferer(s), etc. Other non-limiting examples where the described herein methods are particularly beneficial include measurement s for Discontinuous Reception (DRX) or extended DRX, and measurement s in high speed train environments.

In some embodiments a non-limiting term "wireless device" is used. The wireless device herein can be any type of UE capable of communicating with network node or another UE over radio signals. The wireless device may also be radio communication device, target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine communication (M2M), a sensor equipped with UE, iPAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE) etc..

Also in some embodiments generic terminology "network node", is used. It can be any kind of network node which may comprise of a radio network node such as base station, radio base station, base transceiver station, base station controller, network controller, evolved Node B (eNB), Node B, multi-RAT base station, Multi-cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., Mobility Managing Entity (MME), Self-Organizing Network (SON) node, a coordinating node, positioning node, Minimizing Drive Test (MDT) node, etc.), or even an external node (e.g., <NUM>rd party node, a node external to the current network), etc..

The term "radio node" used herein may be used to denote the wireless device or the radio network node.

The embodiments are applicable to single carrier as well as to multicarrier or carrier aggregation (CA) operation of the wireless device <NUM> in which the wireless device <NUM> is able to receive and/or transmit data to more than one serving cells. The term carrier aggregation (CA) is also called (e.g. interchangeably called) "multi-carrier system", "multi-cell operation", "multi-carrier operation", "multi-carrier" transmission and/or reception. In CA one of the component carriers (CCs) is the primary component carrier (PCC) or simply primary carrier or even anchor carrier. The remaining ones are called secondary component carrier (SCC) or simply secondary carriers or even supplementary carriers. The serving cell is interchangeably called as primary cell (PCell) or primary serving cell (PSC). Similarly the secondary serving cell is interchangeably called as secondary cell (SCell) or secondary serving cell (SSC).

The term "signaling" used herein may comprise any of: high-layer signaling, e.g., via Radio Resource Control (RRC), lower-layer signaling, e.g., via a physical control channel or a broadcast channel, or a combination thereof. The signaling may be implicit or explicit. The signaling may further be unicast, multicast or broadcast. The signaling may also be directly to another node or via a third node.

The term time resource used herein may correspond to any type of physical resource or radio resource expressed in terms of length of time. Examples of time resources are: symbol, time slot, subframe, radio frame, Transmission Time Interval (TTI), interleaving time, hyper System Frame Number (H-SFN), etc..

The term "radio measurement" used herein may refer to any measurement performed on radio signals. Radio measurements can be absolute or relative. Radio measurements can be e.g. intra-frequency, inter-frequency, CA, etc. Radio measurements can be unidirectional (e.g., DL or UL) or bidirectional (e.g., Round Trip time (RTT), Reception-Transmission (Rx-Tx), etc.). Some examples of radio measurements: timing measurements (e.g., Time of Arrival (TOA), timing advance, RTT, Reference Signal Time Difference (RSTD), Synchronization Signal Time Difference (SSTD), Rx-Tx, propagation delay, etc.), angle measurements (e.g., angle of arrival), power-based measurements (e.g., received signal power, RSRP, received signal quality, RSRQ, SINR, Signal to Noise Ratio (SNR), interference power, total interference plus noise, RSSI, noise power, Channel Quality Indicator (CQI), Channel state information (CSI), precoding matrix indicator (PMI), etc.), cell detection or cell identification, beam detection or beam identification, RLM, system information reading, etc..

The term measurement performance used herein may refer to any criteria or metric which characterizes the performance of the measurement performed by a radio node. The term measurement performance is also called as measurement requirement, measurement performance requirements etc. The radio network node has to meet one or more measurement performance criteria related to the performed measurement. Examples of measurement performance criteria are measurement time, number of cells to be measured with the measurement time, measurement reporting delay, measurement accuracy, measurement accuracy with regards to a reference value (e.g. ideal measurement result) etc. Examples of measurement time are measurement period, cell identification period, evaluation period, etc. In some embodiments, the term "RS" is used, which most frequently refers to CRS but in principle may also refer to other RS types or physical signals.

In some embodiments a term bandwidth (BW) is used. Over the BW the radio network node transmits to and/or receives signal from one or more wireless devices in a cell. The bandwidth is interchangeably called as operating BW, channel bandwidth, system bandwidth, transmission bandwidth, cell bandwidth, cell transmission BW, carrier bandwidth, measurement bandwidth, maximum allowed measurement bandwidth, common bandwidth of plurality of cells on a carrier etc. The BW may also correspond to BW of specific signals (e.g. BW of any of: Sounding reference signal (SRS), CRS, Demodulation Reference Signal (DMRS), Discovery Reference Signal, synchronization signal, data channel, control channel etc). The BW may be expressed in different units. Examples of units are KHz, MHz, number of resource blocks, number of resource elements, number of subcarriers, number of physical channels, number of frequency resource units etc. The frequency channel or carrier frequency over which a RAT operates is enumerated or addressed by a channel number aka absolute radio frequency channel number (ARFCN) e.g. E-UTRA ARFCN (EARFCN) in LTE etc. In case, a signal is transmitted in a number of discontinuous in frequency RBs, the term bandwidth may also comprise the total span of all RBs of the signal.

The embodiments described herein may apply to any Radio Access Technology (RAT) or their evolution, e.g., LTE Frequency Duplex Division (FDD), LTE Time Duplex Division (TDD), LTE with frame structure <NUM> or unlicensed operation, UTRA, GSM, WiFi, short-range communication RAT, narrow band RAT, RAT for <NUM>, etc..

With reference to <FIG>, in accordance with an embodiment, a communication system includes a telecommunication network <NUM>, such as a 3GPP-type cellular network, which comprises an access network <NUM>, such as a radio access network, and a core network <NUM>. The access network <NUM> comprises a plurality of base stations 3212a, 3212b, 3212c, such as NBs, eNBs, gNBs or other types of wireless access points being examples of the radio network node <NUM> herein, each defining a corresponding coverage area 3213a, 3213b, 3213c. Each base station 3212a, 3212b, 3212c is connectable to the core network <NUM> over a wired or wireless connection <NUM>. A first user equipment (UE) <NUM>, being an example of the wireless device <NUM>, located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE <NUM> in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a.

The wireless connection <NUM> between the UE <NUM> and the base station <NUM> is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE <NUM> using the OTT connection <NUM>, in which the wireless connection <NUM> forms the last segment. More precisely, the teachings of these embodiments may improve usage of resources that may affect the latency and thereby provide benefits such as reduced user waiting time, and better responsiveness.

According to an aspect it is herein provided a method performed by a radio network node for handling communication of a wireless device in a wireless communication network. The radio network node transmits reference signals over a first bandwidth. The radio network node obtains or receives an indication from the wireless device or a second radio network node, which indication indicates a signal strength or quality of a first and/or secondary serving cell for the wireless device, e.g. RSRP, RSSI or just that the value is below/above a threshold. The radio network node determines to transmit one or more reference signals over the first bandwidth or a second bandwidth based on the indication. The radio network node then transmits one or more reference signals over a second bandwidth or the first bandwidth as determined. The second bandwidth is different than the first bandwidth, and the first and second bandwidth may be preconfigured.

According to another aspect it is herein provided a method performed by a wireless device for handling communication of the wireless device in a wireless communication network. The wireless device may be served by the radio network node in a first and/or secondary serving cell and the radio network node transmits reference signals over a first bandwidth, such as CRS. The wireless device measures a signal strength or quality of the first and/or secondary serving cell from the radio network node. The wireless device transmits an indication to the radio network node indicating the measured signal strength or quality. The wireless device then assumes that a transmission, from the radio network node, of one or more reference signals is made over the first or a second bandwidth, which second bandwidth is different than the first bandwidth, based on the measured signal strength or quality.

According to yet another aspect it is herein provided a radio network node and a wireless device configured to perform the methods herein.

Claim 1:
A method performed by a radio network node (<NUM>,<NUM>) for handling communication of a wireless device (<NUM>) in a wireless communication network (<NUM>), wherein the radio network node (<NUM>,<NUM>) is configured to provide a serving cell for the wireless device (<NUM>) on a lean carrier where reference signals are transmitted with a bandwidth that is variable between a first bandwidth and a second bandwidth, the second bandwidth being narrower than the first bandwidth, and wherein the wireless device (<NUM>) is configured with a discontinuous reception cycle, characterized in that the method comprises:
- transmitting (<NUM>) reference signals over a bandwidth that alternates between the first bandwidth and the second bandwidth in accordance with the discontinuous reception cycle configured for the wireless device (<NUM>);
- obtaining (<NUM>) an indication from the wireless device (<NUM>) or from a second radio network node (<NUM>,<NUM>), which indication indicates that a signal strength or quality of the serving cell for the wireless device (<NUM>) is below a threshold; and
- transmitting (<NUM>), in response to the obtained indication, one or more reference signals over the first bandwidth.