WO2017061939A1

WO2017061939A1 - Wireless device, network node and methods performed therein

Info

Publication number: WO2017061939A1
Application number: PCT/SE2016/050955
Authority: WO
Inventors: Santhan THANGARASA; Muhammad Kazmi; Kazuyoshi Uesaka
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-10-05
Filing date: 2016-10-05
Publication date: 2017-04-13

Abstract

Embodiments herein relate to a method performed by a network node (12) for enabling a wireless device (10) in a wireless communication network (1) to perform radio link monitoring, RLM, of a cell (11) within which the wireless device (10) is served by the network node (12). The network node determines a repetition level for a transmission of a Downlink, DL, control channel for the wireless device (10) based on a coverage level of the wireless device (10) with respect to the cell. The network node (12) transmits the DL control channel repeatedly a number of times in accordance with the determined repetition level.

Description

WIRELESS DEVICE. NETWORK NODE AND METHODS PERFORMED THEREIN

TECHNICAL FIELD

Embodiments herein relate to a wireless device, a network node and methods performed therein regarding wireless communication. Particularly, embodiments herein relate to enabling radio link monitoring by the wireless device in a wireless communication network.

BACKGROUND

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 areas or cell areas, with each area or cell area being served by an access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be called, for example, a "NodeB" or "eNodeB". The area or cell area is a geographical area where radio coverage is provided by the access node. The access node operates on radio frequencies to communicate over an air interface with the wireless devices within range of the access node. The access node communicates over a downlink (DL) to the wireless device and the wireless device communicates over an uplink (UL) to the access node. Such an access node may in the following also be denoted network node.

A Universal Mobile Telecommunications System (UMTS) is a third generation telecommunication network, which evolved from the second generation (2G) 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 communication with user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for radio communication networks, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UMTS, several access 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 access nodes connected thereto. The RNCs are typically connected to one or more core networks. Specifications for the Evolved Packet System (EPS) have been completed within the 3^rd Generation Partnership Project (3GPP) and development continues in the coming 3GPP releases. 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 3GPP radio access technology wherein the access nodes are directly connected to the EPC core network. As such, the Radio Access Network (RAN) of an EPS has an essentially "flat" architecture comprising access nodes connected directly to one or more core networks.

Machine-to-machine (M2M) communication or machine type communication

(MTC) is used for establishing communication between wireless devices such as machines and between machines and humans. The M2M communication may comprise exchange of data, signaling, measurement data, configuration information etc. The size of the wireless device may vary from that of a wallet to that of a base station. The wireless devices are referred to as MTC devices and are quite often used for applications like sensing environmental conditions e.g. temperature reading, metering or measurement e.g. electricity usage etc., fault finding or error detection etc. In these applications the MTC devices are active very seldom but over a consecutive duration depending upon the type of service e.g. about 200 ms once every 2 seconds, about 500 ms every 60 minutes etc. The MTC device may also perform measurements on other frequencies or other RATs.

The MTC device is expected to be of low cost and low complexity regarding components and functions, i.e. to be a low complexity/cost wireless device. A low cost wireless device envisaged for M2M operation may implement one or more low cost features like smaller downlink and uplink maximum transport block size e.g. 1000 bits, and/or reduced downlink channel bandwidth of e.g. 1.4 MHz for a data channel such as a Physical Downlink Shared Channel (PDSCH). A low cost wireless device may also support half duplex frequency division duplex (HD-FDD) operation and comprise one or more of the following additional features: single receiver (1 Rx) at the wireless device, smaller downlink and/or uplink maximum transport block size, e.g. 1000 bits, and reduced downlink channel bandwidth of e.g. 1.4 MHz for a data channel. The low cost wireless device may also be termed or referred to as low complexity wireless device or UE.

Path loss between the MTC device and the access node, such as a base station, may be very large in some scenarios e.g. when the MTC device is used as a sensor or a metering device located in a remote location such as in a basement of a building. In such scenarios the reception of a signal from the access node is very challenging. For example the path loss can be worse than 20 dB compared to normal operation. In order to cope with such challenges the coverage in uplink and/or in downlink has to be substantially enhanced. This is realized by employing one or plurality of advanced techniques in the wireless device and/or in the access node for enhancing the coverage. Some non-limiting examples of such advanced techniques are, but not limited to, transmit power boosting, repetition of transmitted signal, applying additional redundancy to the transmitted signal, use of advanced/enhanced receiver etc. In general when employing such coverage enhancing techniques the M2M communication is regarded to be operating in a 'coverage enhancing mode', also denoted enhanced coverage mode of operation or extended coverage mode of operation herein. A low cost wireless device, e.g. a wireless device with 1 Rx, may also be capable of supporting enhanced coverage mode of operation.

The purpose of Radio Link Monitoring (RLM) is to monitor a radio link quality of a connected serving cell and use that information to decide, at the wireless device, whether the wireless device is in in-sync or out-of-sync with respect to that serving cell. RLM is carried out by the wireless device performing measurement on downlink reference symbols e.g. Cell-specific reference Symbols/signals (CRS), in a Radio Resource Control (RRC)_CONNECTED state. If the results of the radio link monitoring indicate a number of consecutive out-of-sync indications then the wireless device may declare radio link failure (RLF) until the RLM indicates several consecutive in-sync indications. The actual procedure is carried out by comparing the link quality estimated from downlink reference symbol measurements to thresholds representing some target Block Error Rate (BLER) e.g. a CW and a Q_in. CW and Q_in correspond to Block Error Rate (BLER) of hypothetical Physical Downlink Control channel (PDCCH) or physical control format indicator channel (PCFICH) transmissions from the serving cell.

Radio measurements done by the wireless device are typically performed on the serving cell as well as on neighbour cells over some known reference symbols or pilot sequences. The radio measurements are done on cells on an intra-frequency carrier, inter-frequency carrier(s) as well as on inter-Radio Access Technology (RAT) carriers(s), depending upon the wireless device capability and whether it supports that RAT. To enable inter-frequency and inter-RAT measurements for the wireless device gaps may be required, and the access node or another radio network node may have to configure the measurement gaps.

The radio measurements are done for various purposes. Some example measurement purposes are: mobility, positioning, self-organizing network (SON), minimization of drive tests (MDT), operation and maintenance (O&M), network planning and optimization etc. Examples of measurements in LTE are Cell identification aka Physical Cell ID (PCI) acquisition, Reference Symbol Received Power (RSRP), Reference Symbol Received Quality (RSRQ), cell global ID (CGI) acquisition, Reference Signal Time Difference (RSTD), UE RX-TX time difference measurement, Radio Link Monitoring (RLM), which RLM comprises: Out of Synchronization (out of sync) detection and In Synchronization (in-sync) detection etc. The detection of out of sync (OoS) and in-sync is based on the wireless device estimating the channel quality of the serving cell. If it is detected that wireless device is OoS, the wireless device start a certain timer and if OoS is detected a number of times, the wireless device finally declares RLF and turns OFF the transmitter chain. Channel State Information (CSI) measurements performed by the wireless device are used for scheduling, link adaptation etc. by a network node. Examples of CSI measurements or CSI reports are CQI, PMI, Rl etc. They may be performed on reference signals like CRS, Channel State Information-Reference signal (CSI-RS) or Demodulation Reference Signal (DMRS).

A DL subframe # 0 and DL subframe # 5 carry synchronization signals, i.e. both Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS). In order to identify an unknown cell, e.g. new neighbor cell, the wireless device has to acquire a timing of that cell and eventually the PCI. This is called cell search or cell identification. Subsequently the wireless device also measures RSRP and/or RSRQ of the newly identified cell in order to use the radio measurement itself and/or in order to report the radio measurement to the network node. In total there are 504 PCIs. The cell search is also a type of radio measurement. The radio measurements may be done in all Radio Resource Control (RRC) states i.e. in RRC idle and connected states.

In an existing RLM procedure the wireless device performs radio measurements on downlink reference symbols to estimate downlink radio link quality e.g. Signal to Interference plus Noise Ratio (SINR). This radio measurement is then used by the wireless device to determine the hypothetical BLER of a DL control channel, e.g. the PDCCH taking into account PCFICH errors, by using a pre-defined mapping between the estimated quality, e.g. SINR levels, and the BLER of the PDCCH taking into account PCFICH errors. There are two thresholds associated with RLM procedure, namely Q_out and Qin. These two thresholds refer to a certain target BLER: Q_out corresponds to 10 % target BLER of hypothetical PDCCH and Q_in to 2% target BLER of hypothetical PDCCH taking into account PCFICH errors. These targets were developed for legacy network operation and the legacy wireless device characteristics. The operation of enhanced MTC wireless devices is very different from the legacy operation, e.g. Rel-8 cellular operation, both from the network perspective and the wireless device perspective. One main difference is that the enhanced MTC wireless device can operate in an extended coverage, which is 15 dB larger compared to a legacy coverage. This means the enhanced MTC wireless device will operate down to very low SINR e.g. -18 dB. Another difference is that a Radio Frequency Bandwidth (RF BW) of the enhanced MTC wireless device is 1.4 MHz. To enable wireless device operation at such low SINR level the physical characteristics of the DL control channels is also very different e.g. shorter Bandwidth (BW) such as six Resource Blocks (RB) etc.

As a consequence, if the wireless device uses the existing mapping mechanism between signal quality and hypothetical BLER to determine the C and Q_in levels then the wireless device will not be able to maintain the serving cell coverage. This means under low SINR, e.g. below -8 dB, the wireless device may lose the connection with the serving cell since the wireless device may in this case detect that it is out-of-sync although it is not. The wireless device may also do a wrong detection in the other direction, i.e. in- sync instead of out-of-sync. The wireless device may then continue to keep its transmitter ON when it should not do that. This can cause severe interference to other wireless devices and network nodes leading to a limited performance of the wireless

communication network.

SUMMARY

An object of embodiments herein is to provide a mechanism that improves the reliability of the RLM and thus the performance of the wireless communication network.

According to an aspect the object is achieved by providing a method performed by a network node for enabling a wireless device in a wireless communication network to perform RLM of a cell within which the wireless device is served by the network node. The network node determines a repetition level for a transmission of a DL control channel for the wireless device based on a coverage level of the wireless device with respect to the cell. The network node further transmits the DL control channel in the cell repeatedly a number of times in accordance with the determined repetition level.

According to another aspect the object is achieved by providing a method performed by a wireless device for performing RLM of a cell within which the wireless device is served by a network node in a wireless communication network. The wireless device determines a repetition level for a transmission of a DL control channel for the wireless device based on a coverage level of the wireless device with respect to the cell. The repetition level indicates a number of times that the DL control channel is to be repeatedly transmitted in the cell by the network node. The wireless device further performs RLM based on the determined repetition level for the transmission of the DL control channel.

To perform the methods herein a wireless device and a network node are provided. Hence, it is herein provided a network node for enabling a wireless device in a wireless communication network to perform RLM of a cell within which the network node is configured to serve the wireless device. The network node is configured to determine a repetition level for a transmission of a DL control channel for the wireless device based on a coverage level of the wireless device with respect to the cell. The network node is further configured to transmit the DL control channel in the cell repeatedly a number of times in accordance with the determined repetition level.

Furthermore, it is herein provided a wireless device for performing RLM of a cell within which the wireless device is configured to be served by a network node in a wireless communication network. The wireless device is configured to determine a repetition level for a transmission of a DL control channel for the wireless device based on a coverage level of the wireless device with respect to the cell. The repetition level indicates a number of times that the DL control channel is to be repeatedly transmitted in the cell by the network node. The wireless device is further configured to perform RLM based on the determined repetition level for the transmission of the DL control channel.

An advantage of embodiments herein is that the wireless device is enabled to perform RLM functionality when e.g. being an enhanced MTC wireless device, i.e. a wireless device capable of operating in an enhanced coverage mode. Such a wireless device may be a sensor or similar. Embodiments herein enable more accurate operation of RLM by taking into account the different operational scenarios of both the network node and the wireless device. Embodiments herein enable the wireless device to maintain a connection with the serving cell even when operating at an extended cell coverage e.g. at very low SI R such as at -12 dB or below. The number of repetitions used for transmitting the DL control channel depends on the coverage level. For example, more repetitions of the DL control channel will be needed when SNR is≤ -12 dB and fewer repetitions when SNR > is -12 dB, to enable accurate operation of the radio link monitoring at the wireless device.

Thus, this results in a more reliable RLM for wireless devices having poor or limited capability or channel conditions and this results in an improved performance of the wireless communication network. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described in more detail in relation to the enclosed drawings, in which:

Fig. 1 is a schematic overview depicting a wireless communication network according to embodiments herein;

Fig. 2a is a schematic flowchart depicting a method performed by a network node

according to embodiments herein;

Fig. 2b is a schematic flowchart depicting a method performed by a network node

according to embodiments herein;

Fig. 3a is a schematic flowchart depicting a method performed by a wireless device

according to embodiments herein;

Fig. 3b is a schematic flowchart depicting a method performed by a wireless device

according to embodiments herein;

Fig. 4 is a combined signalling scheme and flowchart according to embodiments herein; Fig. 5 is a block diagram depicting a network node according to embodiments herein; Fig. 6 is a block diagram depicting a wireless device according to embodiments herein; Fig. 7 M-PDCCH BLER with DCI format 1C (13bits w/o CRC) for single Tx antenna; and Fig. 8 M-PDCCH BLER with DCI format 1 A (27bits w/o CRC) for single Tx antenna.

DETAILED DESCRIPTION

Embodiments herein relate to wireless communication networks in general. Figure 1 is a schematic overview depicting a wireless communication network 1. The wireless communication network 1 comprises one or more RANs and one or more CNs. The wireless communication network 1 may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, Fifth Generation (5G), 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 herein relate to recent technology trends that are of particular interest in a 5G context, however, embodiments are also applicable in further development of the existing wireless communication systems such as e.g. WCDMA and LTE. In the wireless communication network 1 , wireless devices e.g. a wireless device 10 such as a mobile station, a non-access point (non-AP) STA, a STA, a user equipment and/or a wireless terminal, communicate via one or more Access Networks (AN), e.g. RAN, to one or more core networks (CN). It should be understood by the skilled in the art 5 that "wireless device" is a non-limiting term which means any terminal, wireless

communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station capable of communicating using radio communication with a network node within an area served by the network node.

10 The wireless communication network 1 comprises a first network node 12

providing radio coverage over a geographical area, a first cell 11 or first area, of a first radio access technology (RAT), such as LTE, Wi-Fi, WiMAX or similar. The first network node 12 may be a transmission and reception point e.g. a radio network node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA),

15 an access node, an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit or node capable of communicating with a wireless device within the area served by the first network node

20 12 depending e.g. on the first radio access technology and terminology used. The first network node may be referred to as a serving network node wherein the first cell may be referred to as a serving cell, and the serving network node communicates with the wireless device 10 in form of DL transmissions to the wireless device 10 and UL transmissions from the wireless device 10.

25 Furthermore, the wireless communication network 1 comprises a second network node 13 providing radio coverage over a geographical area, a second cell 14 or second area, of a second RAT, such as LTE, Wi-Fi, WiMAX or similar. The second network node 13 may be a transmission and reception point e.g. a radio network node such as a WLAN access point or an Access Point Station (AP STA), an access controller, an access node,

30 a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of communicating with a wireless device within the area served by the second network node 13 depending e.g. on the second

35 radio access technology and terminology used. The first and second RAT may be the same or different RATs. The second network node 13 may be referred to as a neighbor network node.

The first network node 12 may communicate with the second network node 13 in the wireless communication network 1. This is done by the network nodes communicating with one another over a backhaul connection, e.g. an X2 connection, an S1 connection or similar, between the first network node 12 and the second network node 13.

Embodiments herein relate to a method that may be implemented in the wireless device 10 and a method that may be implemented in the first network node 12 to monitor/determine the downlink radio link quality of a cell, such as the first cell 11. The wireless device 10 estimates DL link quality, QL, based on one or more radio

measurements on downlink reference symbols, e.g. CRS, transmitted by the first network node 12. The wireless device 10 compares the estimated DL link quality with radio link monitoring thresholds Q_out and Q_in based on a coverage level of the wireless device, The wireless device 10 may have different Q_out and Q_in for different coverage levels, and additionally or alternatively, the wireless device 10 may require different number of transmission repetitions to meet the same thresholds for different coverage levels.

Qout is a quality level at which the downlink radio link cannot be reliably received and corresponds to X1% block error rate (BLER) of a hypothetical DL control channel, e.g. M-PDCCH, as a function of at least 'X2' number of times the same DL control channel, e.g. M-PDCCH, with 'X3' Orthogonal Frequency Division Modulation (OFDM) resource elements is repeatedly transmitted by the first network node 12 during a first time period, T1; and

Qin is a quality level at which the downlink radio link can be reliably received and corresponds to Y1 % block error rate of a hypothetical DL control channel, e.g. M-PDCCH, as a function of at least 'Y2' number of times the same DL control channel, e.g. M-PDCCH, with Ύ3' OFDM resource elements is repeatedly transmitted by the serving cell during a second time period, T2.

The wireless device 10 performs the DL radio link monitoring of the serving cell based on the comparison, e.g. it determines whether the wireless device 10 is in in-sync or out-of-sync. For example, the wireless device 10 may evaluate a radio link to the serving cell on periodic basis, e.g. every radio frame, while it is in RRC_CONNECTED state.

The first network node 12 enables the wireless device 10 to perform radio link monitoring of a serving cell. The first network node 12 determines that the wireless device 10 that is capable of operating in enhanced coverage level is performing or is expected to perform radio link monitoring of the serving cell. The first network node 12 may then adapt the number of times, Z, which may be X2 or Y2, the same DL control channel (e.g. M- PDCCH) is to be repeated for transmitting DL control channel, e.g. M-PDCCH, during a 5 third time period (T3), said DL control channel, e.g. M-PDCCH, is used or expected to be used by the wireless device 10 for RLM. Thus, the wireless device 10 may use hypothetical BLER from channel estimation for the M-PDCCH when comparing the estimated DL link quality QL to radio link monitoring thresholds Qin and CW. The first network node 12 then transmits DL control channel, e.g. M-PDCCH, in the serving cell of

10 the wireless device 10 repeatedly Z times. In non- Discontinuous reception (non-DRX), wireless device 10 is required to assess the radio link quality, evaluated over a time period against the thresholds Qin and CW- In Discontinuous reception (DRX), the wireless device 10 is required to assess the quality once every DRX cycle, evaluated over the time period against the thresholds Qm and CW-

15 In some embodiments Z=X2 and T3=T1 if it is determined that the wireless device

10 is or is expected to be in out-of-sync while performing the RLM. In some embodiments Z=Y2 and T3=T2 if it is determined that the wireless device 10 is or is expected to be in in-sync while performing the RLM. In some embodiments X1 =10, X2=2, and X3 = 288, i.e. BLER=10%, 2 repetitions and 288 REs, is applied for OoS or Y1 =2 and Y2=4, and Y3 =

20 144, i.e. BLER=2%, 4 repetitions and 144 REs, is applied for in-sync.

A scenario herein comprises at least one network node such as the first network node 12 serving the first cell 11 , say Primary Cell (PCell) aka serving cell etc. The wireless device 10 may also be configured with one or more additional cells on a need basis e.g. second cell 14, e.g. a Secondary Cell (SCell) in a carrier aggregation (CA)

25 operation. In some embodiments one or more SCells may be served by the second

network node 13. The embodiments presented in this disclosure apply regardless of whether the PCell and the one or more SCells are served by the same or different network nodes.

In some embodiments the wireless device 10 may be configured with the PCell 30 and a Primary Secondary Cell (PSCell) or with a PCell, a PSCell and one or more SCells such as in dual connectivity. The configured cells are wireless device specific aka serving cells of the wireless device 10.

There may be one or more wireless devices in a cell. The embodiments are applicable for a wireless device in a high activity state e.g. RRC CONNECTED state, 35 active mode etc. The wireless device 10 may operate under either normal coverage or under extended coverage, also denoted enhanced coverage. The normal and extended coverage operations may typically take place on narrower RF bandwidth compared with the system bandwidth aka cell BW, cell transmission BW etc. The RF bandwidth is the part of the cell BW that can be used for operation for the wireless device 10. The cell BW may be much larger, and the wireless device 10 may only be scheduled on certain parts of the cell BW, i.e. UE bandwidth or RF bandwidth. In some embodiments the narrower RF BW can be the same as the system bandwidth. Examples of narrow RF BWs are 200 kHz, 1.4 MHz etc. Examples of system BW are 200 kHz, 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz etc. In case of extended/enhanced coverage, the wireless device 10 may be capable of operating under lower signal quality level, e.g. Signal to Noise Ratio (SNR), SINR, ratio of average received signal energy per subcarrier to total received power per subcarrier (Es/lot), RSRQ etc, compared to a wireless device in normal coverage operation in legacy systems. Thus, in enhanced coverage mode the wireless device 10 may be able to operate under lower SNR levels, lower signal quality than in normal coverage mode. The enhanced coverage level may vary with the operational scenario and may also depend on a type of the wireless device 10. For example, the wireless device 10, which is located in a basement with bad coverage, may need a larger or higher level of enhanced coverage, e.g. 10 dB, compared to a wireless device which is at a cell border, which may e.g. need a 5 dB level of enhanced coverage.

The wireless devices operating under low coverage enhancement, i.e. enhanced coverage, may be a different type of wireless devices than typical handheld wireless devices. The wireless devices capable of enhanced coverage could for example be mounted in a wall/tower or other fixed position and could therefore be less mobile than traditional handheld devices. To support enhanced coverage and narrower bandwidth operation, e.g. 200 kHz, 1.4 MHz etc, of such wireless devices, new DL control channels are introduced. The new DL control channel is denoted M-PDCCH and may particularly be used by the wireless device 10 for RLM operation. The method actions performed by a network node, in the following exemplified by the first network node 12 depicted in Fig. 1 , for enabling a wireless device in a wireless communication network, such as the wireless device 10 in the wireless communication network 1 , to perform RLM of the cell within which the wireless device is served by the network node, such as the first cell 11 of the first network node 12 within which the wireless device 10 is served, as depicted in Fig. 1 , according to some embodiments will now be described with reference to a flowchart depicted in Fig. 2a. For simplicity, the terminology introduced in relation to Fig. 1 is kept also in the following description, although the method applies to any network node serving a wireless device in a cell where the wireless device is to perform RLM. 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, but not necessarily all, embodiments are marked with dashed boxes.

Action 201. The first network node 12 may broadcast information indicating one or more repetition levels supported by the first network node 12. Alternatively or additionally, the first network node 12 may broadcast information indicating a determined repetition level currently applied for the for the transmission of the DL control channel for the wireless device 10.

Action 202. The first network node 12 may then receive information from the wireless device 10, said information indicating at least one repetition level supported by that wireless device. In some embodiments, the reception of this information, e.g. in a RACH request transmitted by the wireless device 10, may serve to make the first network node 12 aware of that the wireless device 10 has the repetition level supported by the wireless device 10. Hence, the first network node may determine or find out the repetition levels that may be necessary/needed for this particular wireless device 10 for successful reception at a certain SNR level or enhanced coverage level.

Action 203. The first network node 12 may obtain information that the wireless device 10 is capable of operating under enhanced coverage with respect to the first cell 1 1 and is performing or is expected to perform radio link monitoring of the first cell 11.

Action 204. The first network node 12 may determine a coverage level of the wireless device 10 with respect to the first cell 1 1. The first network node 12 may determine the coverage level of the wireless device 10 with respect to the first cell 11 based on one or more of the following: Random access transmission of the wireless device 10 in the first cell 1 1 ; Signal quality of wireless device 10 with respect to the first cell, Path loss between the wireless device 10 and the first cell 11 ; and Transmit power of the wireless device 10.

Action 205. The first network node 12 determines the repetition level for a transmission of a DL control channel for the wireless device 10 based on a coverage level of the wireless device 10 with respect to the first cell. The repetition level indicates or prescribes a number of times that the DL control channel is to be repeatedly transmitted in the first cell 11. The number of times may be dependent on whether the wireless device is in out-of-sync operation or in-sync operation. For example, the first network node 12 may determine a first repetition level for a transmission of the DL control channel associated with a first link quality threshold indicating an out-of-sync operation of the wireless device 10 and a second repetition level for the transmission of the DL control channel associated with a second link quality threshold indicating an in-sync operation of the wireless device 10. The thresholds are associated with the coverage level of the wireless device 10 with respect to the first cell 11. The first network node 12 may determine the repetition level based on an assumption that the wireless device 10 is in an enhanced coverage mode with respect to the first cell 1 1. The first network node 12 may determine the repetition level by using a mapping table which maps, i.e. provides a mapping between, a required repetition level for the DL control channel and the determined coverage level. The first and second link quality thresholds will be different within a certain coverage level. The thresholds may also change for other coverage levels.

Action 206. The first network node 12 may determine an aggregation level for the DL control channel based on the coverage level of the wireless device 10 with respect to the first cell 1 1 .

Action 207. The first network node 12 transmits the DL control channel in the first cell 11 repeatedly a number of times in accordance with the determined repetition level. The first network node 12 may further transmit the DL control channel with the determined aggregation level in the first cell 1 1. The first network node 12 may transmit the DL control channel using a certain reference value for the repetition level and adapting the reference value for the repetition level depending upon the actual coverage level of the wireless device 10, and then the first network node 12 may transmit the DL control channel using the adapted reference value for the repetition level in order to enable the wireless device 10 to perform the RLM even if the coverage level changes over time. In one example, referring to action 205 above, the first network node 12 may transmit the DL control channel a number of times prescribed by the determined first repetition level when the wireless device (10) is in out-of-sync operation and a number of times prescribed by the determined second repetition level when the wireless device (10) is in in-sync operation.

Action 208. The first network node 12 may then adapt the repetition level for the transmission of the DL control channel when the coverage level changes; The DL control channel is used or expected to be used by the wireless device 10 for performing RLM.

As explained above, embodiments herein may be implemented in a network node, e.g. the first network node 12. An embodiment of the overall procedure performed by the first network node is as follows described with reference to Fig. 2b. Action 211. The first network node 12 obtains information that the wireless device 10 is capable of operating under enhanced coverage and is performing or is expected to perform radio link monitoring of the serving cell 11 , see also action 203 above. This may be determined at the first network node 12 based on information that may be obtained from within the first network node 12 or from a different network node. This may also be determined at a different network node and sent to the first network node 12. In the first action 211 the first network node 2 may determine which one or more of its connected wireless devices, i.e. wireless devices served by the first network node12, that are operating in or expected to operate in or with enhanced coverage. This may be determined as follows. The first network node 12 indicates in its broadcast information that it supports enhanced coverage operation. All receiving wireless devices in the first cell 11 are then required to respond to that request accordingly. The wireless device 10 may send a Random Access Channel (RACH) request using the information provided in the broadcast channel and by that the first network node 12 may become aware that this particular wireless device 10 requires service under enhanced coverage. All wireless devices determined to be or need to be operating under enhanced coverage in the first action 21 1 may perform radio link monitoring as it is a fundamental procedure to maintain for RRC_CONENCTED state. It is by using RLM procedure that the wireless device 10 detects whether it is in in-sync or out-of-sync with the serving cell.

Action 212. The first Network node 12 adapts the number of times (Z) the same one or more DL control channels, e.g. M-PDCCH, is to be repeated for transmitting said one or more DL control channels, e.g. M-PDCCH, during a certain time period; said DL control channels, e.g. M-PDCCH, is/are used or expected to be used by the wireless device 10 for performing RLM. The value of Z may correspond to X2, which is the number of times the same DL control channel is repeated for enabling the wireless device 10 to do an out-of-sync process or operation during the first time period, T1. Alternatively or additionally, the value of Z may correspond to Y2, which is the number of times the same DL control channel is repeatedly transmitted for enabling the wireless device 10 to do an in-sync process or operation during the second time period, T2. In the second action 212, the first network node 12 adapts the Z-value and may further determine one or more parameters associated with the one or more DL control channels (e.g. M-PDCCH transmission) that need to be adapted to enable the RLM operation under enhanced coverage.

More specifically the first network node 12 may adapt the repetition level of at least one DL control channel used by the wireless device 10 for RLM or involved in RLM. The repetition level herein means the number of times, Z, the same M-PDCCH is to be repeated for transmitting M-PDCCH during a time period. There are several ways for the first network node 12 to find out the required repetition levels as explained below.

In a first example, the first network node 12 may indicate in its broadcast 5 information what repetition level it supports, e.g. see action 201 above. The broadcast information may for example include 1-4 levels which correspond to 1-4 enhancement coverage levels. A coverage level may be defined in terms of a range in link quality, e.g expressed in terms of SNR or SINR. Coverage levels may be defined for normal coverage mode as well as enhanced coverage mode. Examples of 4 enhanced coverage levels,

10 e.g. 1 , 2, 3 and 4, corresponding to 4 different repetition levels are SNR or SINR down to - 8 dB, -12 dB, -14 dB and -18 dB respectively. The wireless device 10 may indicate in its message sent to the first network node 12, e.g. RACH request, the required repetition level of DL control channel(s) and/or the coverage enhancement level under which it may operate with respect to the serving cell 1 1 , see action 202 above. The first network node

15 12 receiving the request then becomes aware of the repetition level of that particular wireless device 10.

In a second example, the first network node 12 may indicate in its broadcast information what repetition level is supported by the first network node 12, see action 201 above. The broadcast information may for example include 1 -4 levels which correspond to

20 1 -4 coverage enhancement levels. In addition to this information, the wireless device 10 may perform downlink measurements on the reference symbols to estimate the downlink link quality, QL. The wireless device 10 may use the estimated information on Ql_ to more reliably choose the repetition level. The first network node 12 may then receive information from the wireless device 10, action 202 above, and then become aware of the

25 repetition level of that particular wireless device 10.

In addition to the two examples above, the wireless device 10 could also use information on path loss information, wireless device transmission power information alone or in combination with the indication information from the first network node 12 to reliably choose the repetition level.

30 In a third example the first network node 12 may autonomously determine the coverage level of the wireless device 10, e.g. SINR or SNR of the wireless device with regards to the serving cell 1 , see action 204 above. For example the first network node 12 may measure uplink received signal from the wireless device 10 and translate it to downlink received signal quality at the wireless device 10 by taking into account cell load,

35 e.g. BS transmit power, number of active wireless devices in the first cell 1 etc. The first network node 12 may then use a mapping table which maps, i.e. provides a mapping between, the required repetition level of the DL control channel and the coverage level i.e. the estimated DL signal quality, to determine number of repetitions, i.e. the repetition level.

5 Action 213. The first network node 12 transmits said one or more DL control channels (e.g. M-PDCCH) in the serving cell 1 1 of the wireless device 10 in accordance with the determined value of Z. In action 213, the first network node 12 may transmit at least one DL control channel (e.g. M-PDCCH) in the serving cell 11 of the wireless device 10 according to the adapted or selected repetition level, Z. this corresponds to the action 10 207 above.

The first network node 12 may also adapt one or more additional transmission parameters associated with at least one DL control channel, e.g. M-PDCCH, and transmit the at least one DL control channel, e.g. M-PDCCH, using the adapted value of Z as well as adapted values of one or more additional transmission parameters. Examples of 15 additional parameters are transmit power, DL control channel element (CCE) level etc.

For example the first network node 12 may adapt transmit power by increasing Tx power when the wireless device 10 is in enhanced coverage above a threshold, i.e. SINR is below a threshold.

In another exemplary implementation if the first network node 12 is unable to

20 determine or unable to accurately determine the wireless device 10 enhanced coverage level, then the first network node 12 may transmit the DL control channel(s) using a certain reference value of the repetition level (Zr). The Zr may be pre-defined, indicated by the wireless device 0 or decided by the first network node 12. In one example Zr may correspond to the maximum value of Z e.g. Zr = 4.

25 Action 214. The first network node 12 may further adapt the parameter Z (e.g. X2 or Y2) depending upon the actual coverage level of the wireless device 10 e.g. received signal quality from the wireless device 10 in the serving cell 11. The first network node 12 may continuously adapt the repetition level, Z, of at least one DL control channel on regular basis and may also transmit, see action 213, at least one DL control channel using 30 such an adapted or updated repetition level in order to enable the wireless device 10 to continuously perform the RLM even if its coverage level changes over time.

The method actions performed by the wireless device for performing RLM of the cell within which the wireless device is served by the network node in the wireless

35 communication network according to some embodiments will now be described with reference to a flowchart depicted in Fig. 3a. The wireless device may for example be the wireless device 10 which is served by the first network node 12 in the first cell 11 as depicted in Fig. 1. For simplicity, the terminology introduced in relation to Fig. 1 is kept also in the following description, although the method applies to any wireless device being served by a network node in a cell where the wireless device is to perform RLM. 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, but not necessarily all, embodiments are marked with dashed boxes.

Action 301. The wireless device 10 may receive broadcasted information indicating a repetition level supported by the first network node 12. Alternatively or additionally, the wireless device 10 may receive broadcasted information indicating a determined repetition level currently applied for the for the transmission of the DL control channel for the wireless device 10.

Action 302. The wireless device 10 may transmit to the first network node 12, information that the wireless device 10 is capable of operating under enhanced coverage and is performing or is expected to perform radio link monitoring of the first cell 11. In some embodiments information may be transmitted from the wireless device 10, said information indicating the repetition level supported by that particular wireless device 10.

Action 303. The wireless device 10 may estimate the DL link quality by performing a radio measurement on downlink reference symbols of the first cell 11.

Action 304. The wireless device 10 may further determine the coverage level of the wireless device with respect to the first cell 11 based on the estimated DL link quality. The wireless device may determine the coverage level of the wireless device 10 with regards to the first cell 11 based on one or more of the following: Random access transmission of the wireless device 10 in the first cell 1 1 ; Path loss between the wireless device 10 and the first cell 11 ; and Transmit power of the wireless device 10.

Action 305. The wireless device 10 determines the repetition level for a transmission of the DL control channel for the wireless device 10 based on the coverage level of the wireless device 10 with respect to the first cell 11. The repetition level indicates a number of times that the DL control channel is to be repeatedly transmitted in the first cell 11 by the network node 12.

Action 306. The wireless device 10 may further determine the aggregation level for the transmission of the DL control channel based on the coverage level of the wireless device 10 with respect to the first cell 11. Action 307. The wireless device 10 may receive the DL control channel repeatedly the number of times within the first cell 11 in accordance with the repetition level; and combining all or certain number of repetitions.

Action 308. The wireless device 10 may select, based on the determination of the coverage level, one of a plurality of mapping tables, which selected mapping table is used for estimating a hypothetical Block Error Rate, BLER, which in turn is used to determine whether the wireless device (10) is in in-sync or out-of-sync when performing the RLM in action 310.

Action 309. The wireless device 10 may then compare the estimated DL link quality with the first link quality threshold indicating an out-of-sync operation and the second link quality threshold indicating an in-sync operation, which thresholds are associated with the coverage level and a respective number of repetitions of a transmission of the DL control channel. The thresholds may be different for different coverage levels.

Action 310. The wireless device 10 performs the RLM based on the determined repetition level for the transmission of the DL control channel. The RLM may comprise that the wireless device 10 declares out-of-sync or in-sync. I.e. the RLM comprises the comparison to detect in-sync or out-of-sync. The wireless device 10 may perform the RLM based on the comparison and the wireless device 10 may further perform the RLM based on the determined aggregation level for the transmission of the DL control channel. The wireless device 10 may perform the RLM based on the comparison and the repetitively received DL control channel.

This embodiment discloses a method performed by the wireless device 0 for adapting the radio link monitoring procedure under enhanced coverage. The overall method can be summarized as shown in Fig. 3b.

Action 311. The wireless device 10 performs the radio measurement on downlink reference symbols of the serving cell 11 to estimate DL link quality. An RLM procedure requires the wireless device 10 to estimate the downlink link quality which is denoted as QL. The wireless device 10 may measure on downlink reference symbols like CRS which are always transmitted in the downlink subframes. CRS measurements are typically used to estimate the downlink channel and it is for example used to perform RSRP

measurement. The wireless device 10 may further include radio measurements using other reference symbols like DMRS or discovery signals such as PSS, SSS, CSI-RS etc. The main difference is that CRS are cell specific symbols while DMRS may be wireless device specific. The radio measurement may measure a signal quality or strength, e.g. SINR, SNR, RSRQ, RSRP etc. indicating the signal to noise ratio of that link for that particular signal. The method for performing the radio measurement may depend on coverage operation scenario, i.e. level of coverage enhancement as explained below.

In a first example it is assumed that the wireless device 0 is operating under normal coverage with narrowband RF bandwidth e.g. 200 KHz, 1.4 MHz etc. Normal coverage operation means that wireless device 10 has good coverage e.g. SINR is not below -6 dB. The wireless device 10 could perform the radio measurement in this case using the legacy measurement procedure, i.e. measuring the signals over all resource elements in a subframe every 40 ms and then averaging that over a time known as measurement period.

In a second example it is assumed that the wireless device 10 is operating under enhanced coverage also referred to as coverage enhancement with narrower RF bandwidth. Coverage enhancement operation means that the wireless device 10 has worse DL link quality QL compared to normal coverage operation. As an example under the coverage enhancement operation the wireless device 10 may experience R dB larger path loss from the serving cell 11 compared to the path loss the wireless device 10 may experience under the normal coverage. In another example under the coverage enhancement operation the wireless device 10 may experience S dB lower received signal strength from the serving cell 1 1 compared to the signal strength it may experience under the normal coverage. In another example under the coverage enhancement operation the wireless device 10 may experience Q dB lower received signal quality from the serving cell 11 compared to the signal quality it may experience under the normal coverage. It is assumed that the coverage is enhanced by 7 dB in this example. Typically coverage enhancement is achieved by repetition of e.g. the DL control channel i.e. by the first network node 12. Then the wireless device 10 combines all or certain number of repetitions, which are received at the wireless device 10 on e.g. the DL control channel. In some examples it may be enhanced by 15 or even 20 dB or even by larger value.

The legacy measurement method may not yield good measurement accuracy since wireless device 10 is under bad coverage meaning that the received energy in all resource elements may not be sufficient to mitigate the interference and noise. It is more useful to perform measurements over 2 or more consecutive subframes in this case as it increases the number of resource elements available for radio measurement. The measured energy in Resource elements (RE) are then coherently averaged and this may improve the total average measurement accuracy over the measurement period. The number of subframes used for coherent averaging for downlink reference symbol measurement may depend on the signal level (e.g. SINR, SNR levels etc). At moderate coverage enhancement levels the measurement accuracy can be greatly improved if the reference symbols are coherently averaged over 2 or more subframes. However at high coverage enhancement levels this has a negative impact as the measured symbols are dominated by the noise and the wireless device 10 is not able to separate the noise from the useful signals. Averaging of multiple subframes in this case may increase overall noise level of the measurement. Thus measurement may be performed over small number subframes at very high coverage enhancement levels.

Action 312. The wireless device 10 compares the estimated DL link quality with radio link monitoring thresholds C and Qm. Embodiments herein describe a solution, which involves the applying the obtained measurement from the first part as described in action 311. There are two target thresholds which correspond to X1 % block error rate and Y1 % block error rate of hypothetical DL control channel e.g. M-PDCCH transmissions. The first BLER target, X1 %, associated with the Q_out threshold, corresponds to out-of- sync, i.e. the BLER level at which the downlink radio link cannot be reliably received. C is signal quality, e.g. SNR, that corresponds to certain BLER of DL control channel i.e. X1 %. There is a mapping between SNR and BLER. BLER target is fixed = X1 %. All the wireless device 10 does is that it measures SNR and see if it is at X1 %. If so then the wireless device declares to be out-of-sync. The second target BLER, Y1%, associated with the Qin threshold, corresponds to the BLER level at which the downlink radio link can be reliably received. Qm is signal quality, e.g. SNR, that corresponds to certain BLER of DL control channel i.e. Y1 %. There is a mapping between SNR and BLER. BLER target is fixed = Y1 %. All the wireless device 10 does is that it measures SNR and see if it is at Y1 %. If so then the wireless device 10 declares to be in-sync. The RLM is performed within the wireless device 10, and the indications of out-of-sync and in-sync, or the declaration of out-of-sync and in-sync, are done by the lower layer such as physical layer to a higher-layer.

The obtained signal quality measurement is compared to Q_out corresponding to X1 and Qin corresponding to Y1 to detect whether the wireless device 10 is in-sync or out-of- sync with the serving first network node 12. This determination is based on a pre-defined mapping table mapping the signal quality and parameters X1 and Y1 . When the wireless device 10 is operating under enhanced coverage, the DL control channels may be transmitted by the first network node 12 with a number of times (Z) over a certain duration The number Z may also depend on the enhanced coverage level of the wireless device with regards to its serving cell e.g. SNR, SINR level. The relation between the target BLER, the number of times the control signals are transmitted and the period over which the transmissions are repeated is determined by the first network node 12. As described in Fig. 2b the first network node 12 transmits one or more DL control channels with the adapted parameters e.g. with selected value of Z. As an example typical BLER targets are 10% for out-of-sync (X1 =10) and 2% for in-sync (Y1 =2%). The values of repetition parameters X2 and Y2 for enabling in-sync and out-of-sync respectively may depend on the level of coverage enhancement. This number may be determined by the first network node 12 based on for example the information related to the wireless device coverage level as described in Fig. 2a action 204. These thresholds or targets may be held at same levels as for legacy systems but different number of repetitions may be needed to meet these thresholds.

Action 313. The wireless device 10 performs the DL radio link monitoring of the serving cell 11 based on the comparison e.g. determines whether the wireless device 10 is in-sync or out-of-sync. Hence, the wireless device 10 is to determine the hypothetical BLER of the DL control channel, e.g. M-PDCCH, by using a mapping table which maps the estimated signal quality (QL) to the hypothetical BLER of the DL control channel, e.g. of M-PDCCH transmissions, such mapping further depends on at least enhanced coverage level, which in turn corresponds to certain value of repetition level. For example assume 4 different coverage levels e.g. SINR down to -6, -8, -12 and -18 dB. In this example there is one mapping table between QL and the hypothetical BLER for each coverage level. This means 4 mapping tables in this example. Furthermore each mapping table is derived assuming certain number of repetition level with which the at least one DL control channel used by the wireless device 10 for RLM is transmitted by the first network node 12. The wireless device 10 then determines its coverage level, e.g. estimated SINR or SNR, and based on this determination it selects one of the plurality of mapping tables. The selected mapping table is then used for estimating the hypothetical BLER, which in turn is used to determine whether the wireless device 10 is in-sync or out-sync. If the wireless device 10 experiences certain number of consecutive out-of-sync then the wireless device 10 initiates radio link failure (RLF) procedure by starting a timer. After the expiry of the RLF timer the wireless device 10 may turn off its transmitter.

As an example Table 1 and Table 2 show the SNR to BLER mapping for Additive White Gaussian Noise (AWGN) for Q_out in Table 1 and Qin in Table 2. As stated earlier Qout and Qin are expressed in terms of hypothetical BLER. For sake of briefness, the same tables show the achievable BLER for different SNR values as function of aggregation level (AL) and number of repetitions. AL indicates what aggregation level is assumed and bundle indicates the number of repetitions that have been assumed. Table 1 and 2 compare the difference between -PDCCH configurations and legacy PDCCH performance taking into account the PCFICH decoding errors. For Q_out 27 bits are set with PDCCH aggregation level 8, giving 288 OFDM symbols and for Q_in 11 bits are set with PDCCH aggregation level 4, giving 144 OFDM symbols. For M-PDCCH, 5 different configurations are shown with aggregation levels 4, 8, and 16, corresponding to 144, 288, and 576 OFDM symbols. For aggregation levels 16, we also show 10 repetitions and 50 repetitions. No power boosting is used for PDCCH and M-PDCCH. Similar tables can be defined for other propagation conditions e.g. fading channel. These tables can be stored in the memory of the wireless device 10 for determining Q_in and Q_out levels when operating at different coverage level, e.g. SNR or SINR. The tables can also be predefined in the specification to allow the first network node 12 to select an appropriate combination of transmission parameters, e.g. AL, bundle (repetitions) for transmitting M- PDCCH for enabling the wireless device 10 for performing RLM, e.g. determining Q_in and Qout. These tables show that the BLER may be improved with higher aggregation level and repetition levels. It is shown that it is quite bad with low AL and no repetition, but then when repetition is applied the BLER goes down. So for a certain SNR level, the BLER may be improved by using AL or repetition level, or a combination of these.

This relation between measured signal quality, e.g. SNR, and hypothetical BLER of the DL control channel, e.g. M-PDCCH, may further depend on one or several additional parameters for enhanced coverage operation compared to legacy RLM operation as listed below:

Number of receive antennas at the wireless device 10

- Number of transmit antennas at the serving cell

- Configured or transmission bandwidth or BW of M-PDCCH and/or of DL reference signal

- Duplex mode, e.g. Full Duplex (FD)-FDD or HD-FDD

- Channel format, e.g. Downlink Control Information (DCI) format

- Size of DL control channel e.g. number of OFDMA symbols for M-PDCCH

- Transmit power of M-PDCCH e.g. ratio of M-PDCCH power to DL reference signal (RS) power

- Frequency hopping, e.g., change the transmitted frequency every 10 subframes, etc. Number of receive antennas at the wireless device 10

The wireless device 10, e.g. an enhanced MTC wireless device, may operate under both normal coverage and enhanced coverage is expected to have single receive antennas at the wireless device 10. The Rel-12 MTC RLM procedure is based on SNR- BLER table of PDCCH channel. The SNR-BLER has not been studied for the new channel M-PDCCH with single receive antenna as capability. Number of receive antennas are expected to have a strong influence on what SNR can be achieved while maintaining a certain threshold. Compared to legacy RLM procedure using PDCCH channel, the enhanced MTC operation under normal and enhanced coverage is very challenging and requires some new mechanism, e.g. repetitions, to counteract e.g. the noise and interference when operating at very low SNR levels. This relation between number of receive antennas at the wireless device 10 and the achievable SNR and BLER for M- PDCCH assuming repetitions under normal and enhanced coverage has not been considered earlier.

Number of transmit antennas at the serving cell (first cell 11)

The number of transmit antennas used at the serving cell will also impact the SNR-BLER table for M-PDCCH. As explained in the earlier text, the wireless device 10 may measure on cell specific reference symbols (CRS) on its serving cell. Both CRS and M-PDCCH are be transmitted by the serving cell and how many antennas used for transmissions will certainly affect the achievable SNR and BLER targets. Compared to legacy RLM procedure using PDCCH channel, the eMTC operation under normal and enhanced coverage is very challenging and require some new mechanism, e.g.

repetitions, to counteract e.g. the noise and interference when operating at very low SNR levels. This relation between number of transmit antennas at the serving cell and the achievable SNR and BLER for M-PDCCH assuming repetitions under normal and enhanced coverage is something new which has not been considered earlier.

Configured or transmission bandwidth or BW of M-PDCCH and/or of DL reference signal Both system bandwidth and wireless device RF bandwidth may affect the SNR-

BLER performance of M-PDCCH. The downlink reference signals, e.g. CRS, are transmitted over the system bandwidth and the wireless device 10 measures on the reference symbols in order to compare that to hypothetical BLER of M-PDCCH. If the system bandwidth is wide then the wireless device 10 may have to retune its receiver to any downlink frequency within the system bandwidth and perform radio measurement on any received downlink subframe. This also allows the wireless device 10 to measure on multiple consecutive downlink subframes which may be necessary to achieve good measurement accuracy especially at low SNR levels, e.g. at high coverage enhancement levels. Since downlink reference symbol measurements are used for RLM procedure the configured or transmission bandwidth of DL reference signals may affect the SNR-BLER of M-PDCCH.

In legacy RLM procedure PDCCH was transmitted over the entire system bandwidth. Nevertheless, M-PDCCH transmissions may be limited to wireless device RF bandwidth which can be 6 PRBs or 1.4 MHz in case of enhanced MTC operation under both normal and enhanced coverage. Wireless device's capability to measure M-PDCCH may certainly depend on the bandwidth the M-PDCCH is transmitted. In addition, enhanced MTC wireless devices may need to retune its receiver frequency to central Physical Resource Blocks (PRB) in order to measure PSS/SSS which are necessary to carry out cell search procedure. While the wireless device 10 is retuned to central 6 PRBs the same wireless device 10 may not be able to receive M-PDCCH transmissions which are transmitted to the configured wireless device RF bandwidth. This may reduce the M- PDCCHs receiving opportunities and may consequently affect the SNR-BLER of M- PDCCH.

The duplex mode may also affect SNR-BLER relation of M-PDCCH.

In HD-FDD operation the wireless device 10 has to switch between UL and DL time resources e.g. UL and DL subframes. The switching can be from UL to DL time resources or from DL to UL time resources. The switching operation is interchangeably called as RX-TX or TX-RX switching or transition etc. The switching causes interruption due to change in the frequency of operation and also to account for timing advanced which in turn depends upon the maximum cell range. Therefore time resources, e.g., subframes, may be unused by the wireless device 10 to account for switching between UL and DL time resources (e.g. subframes). These unused time resources at the wireless device 10 are interspersed between UL and DL time resources. The switching between UL and DL time resources may be done dynamically, i.e., as frequent as after every UL or DL time resource. In this case, the switching is typically realized by scheduling i.e.

sending grant to the wireless device 10 for UL or DL scheduling in M-PDCCH. The switching between UL and DL time resource may also be done on static or semi-static basis. In this case the wireless device 10 can be configured with a pattern of UL and DL time resources by the first network node 12 or it may use a pre-defined pattern of UL and DL time resources. The HD-FDD wireless device cannot measure on downlink subframes and therefore the opportunities to measure on downlink reference symbols and M-PDCCH are considerably reduced when the HD-FDD wireless device is in uplink subframes and the subframes during which the switching from uplink to downlink and vice versa occurs. The HD-FDD operation under enhanced coverage which involves repetitions may further affect the SNR-BLER relation of M-PDCCH. This is because in HD-FDD operation where there are fewer DL subframes per frame, e.g. 2 DL subframes, the first network node 12 may not be able to send repetition with the same periodicity like in FDD, where all DL subframes are transmitted in every frame. Therefore for HD-FDD the mapping tables may be different compared to those used for FDD. This has not been considered in earlier RLM procedure.

TDD operation includes different TDD-configurations, or UL-DL configurations. The number of available downlink subframes depends on the TDD-configuration. It has been observed that measurements over multiple consecutive subframes are essential to achieve good measurement accuracy in coverage enhancement. The number of consecutive downlink subframes available for downlink reference signal measurements and M-PDCCH measurement depends on configured TDD-configuration of the wireless device 10. The impact of TDD-configuration on SNR-BLER of M-PDCCH has not been considered in legacy RLM procedure. This is because in TDD operation where there are fewer DL subframes per frame, e.g. 2 DL subframes, the network node may not be able to send repetition with the same periodicity like in FDD, where all DL subframes are transmitted in every frame. Therefore for TDD the mapping tables may be different compared to those used for FDD. Furthermore one set of mapping tables may be associated with one particular TDD configuration. The TDD configurations differ in terms of number of UL and DL subframes per frame.

Channel format, e.g. DCI format

In the legacy RLM measurements, in-sync and out-of-sync threshold is derived from the assumption that the wireless device 10 decodes DCI format 1 C and 1A on PDCCH, respectively. DCI format 1C is used to allocate random access response, paging message, and system information. On the other hand DCI format 1A is used for the compact scheduling of one PDSCH codeword in one cell. The necessary numbers of bits before channel coding may be reduced for Rel-13 MTC because, for example, network node only indicate at most 6 PRBs for PDSCH, although it needs to indicate 100PRBs in the legacy system. Size of DL control channel e.g. number of OFDM A symbols for M-PDCCH

In the legacy RLM measurements, in-sync and out-of-sync threshold is derived from the assumption wireless device 10 decode PDCCH with 288 OFDM symbols and

144 OFDM symbols respectively. Network node can configure the number of OFDM symbols to transmit PDCCH, e.g., 72, 144, 288, and it is called aggregation level. Larger aggregation level means the network mode can transmit the DL control channel information more redundant and thus it reduces the required SNR.

The first network node 12 can also modify the aggregation level for M-PDCCH.

One difference from PDCCH is that the number of OFDM symbols for M-PDCCH changes according to the control region. Since Rel-13 MTC will co-exist with the LTE legacy system, the a few first OFDM symbols may be occupied by the legacy wideband DL control channels such as PCFICH and PDCCH. The number of M-PDCCH OFDM symbols change according to the number of DL control channel OFDM symbols configured in the network.

Transmit power of M-PDCCH e.g. ratio of M-PDCCH power to DL RS power

The transmit power of M-PDCCH may certainly affect the SNR of M-PDCCH. In cases with bad coverage, e.g. cell-edge, basements, it may be necessary to boost the transmit power of M-PDCCH to reach the wireless device 10. The power boosting level and the reception level used may affect the SNR-BLER of M-PDCCH. The legacy RLM procedure depends on the ratio of DL control channel, e.g. PDCCH, power to the DL RS power. The impact of transmit power of M-PDCCH on achievable SNR-BLER of M- PDCCH has to be considered for enhanced MTC RLM procedure. For example when transmit power is below a threshold then the enhanced coverage can be realized by using larger number of repetitions of the DL control channel transmitted by the first network node 12. But when transmit power is equal or to larger than a threshold then the enhanced coverage can be realized by using fewer number of repetitions of the DL control channel transmitted by the network node.

In some embodiments it may be natural to assume that a wireless device that is out-of-sync with the serving network node may require higher repetitions than a wireless device that is in-sync. In one example configuration, the M-PDCCH may be repeated 2 times (Y1=2) when the wireless device 10 is in-sync while the first network node 12 may use 4 repetitions (Y2=4) when out-of-sync. Frequency hopping Since M-PDCCH used only 6 PRBs regardless of the system bandwidth, it is possible for the first network node 12 to change the transmitting frequency. The frequency hopping may, as in addition to repeatedly transmitting the DL control channel, improve M- PDCCH decoding performance if the wireless device 10 is located on the heavy frequency selective environment. However it has not been considered in the earlier RLM procedure.

Table 1 : BLER versus SNR under Additive White Gaussian Noise (AWGN) for Q for different combination of aggregation level (AL) and bundle (repetition level) transmission of M-PDCCH

in terms of BLER under AWGN

SNR PDCCH M-PDCCH M-PDCCH M-PDCCH M-PDCCH M-PDCCH

(dB) AL8 AL4 AL8 AL16 AL16 AL16

Bundlel Bundlel Bundlel Bundlel 0 Bundle50

-20 1 0,99995 0,89585 0,26085

-19 1 1 1 0,99995 0,7697 0,1954

-18 1 0,99995 0,99995 0,60645 0,14735

-17 1 0,9999 0,4589 0,1113

-16 1 1 1 0,9995 0,3421 0,08415

-15 1 1 0,99735 0,25385 0,06195

-14 1 1 0,99995 0,98795 0,18495 0,04495

-13 0,9995 0,9479 0,13475 0,03255

-12 0,9931 1 0,99795 0,83255 0,09675 0,0228

-11 0,9661 1 0,9899 0,5891 0,06215 0,01525

-10 0,86845 0,99975 0,9579 0,2775 0,02935 0,00805

-9 0,64255 0,999 0,8529 0,07705 0,00825 0,00315

-8 0,33135 0,99285 0,6196 0,0113 0,00125 0,0006

-7 0,11485 0,9653 0,31335 0,0011 5.00E-05 0,0002

-6 0,0318 0,87565 0,09195 5.00E-05 0 0

-5 0,01065 0,6677 0,0158 0 0 0

-4 0,0032 0,3712 0,0019 0 0 0

-3 0,00115 0,1297 0,00015 0 0 0

-2 0,0002 0,02775 0 0 0 0

-1 5.00E- 0,0043 0 0 0 0

05

0 0 0,00035 0 0 0 0

1 0 0 0 0 0 0 Table 2: BLER versus SNR under Additive White Gaussian Noise (AWGN) for Qin for different combination of aggregation level (AL) and bundle (repetition level) transmission of M-PDCCH

Fig. 4 is a combined flowchart and signaling scheme according to some embodiments herein.

Action 401. The first network node 12 may determine if the wireless device 10 is capable of enhanced coverage i.e. to use different coverage enhancement levels for RLM and/or whether the wireless device 10 is performing or is to perform RLM in the first cell 11.

Action 402. The first network node 12 determines or adapts number of repetitions of a transmission of a DL control channel for the wireless device 10 based on an assumption or actually determining that the wireless device is in an enhanced coverage mode. For example, the first network node 12 may assume the wireless device 10 is in the enhanced coverage mode and adapt the number of repetitions to a preconfigured value or the first network node 12 may determine number of repetitions based on estimated quality at the first network node 12 or by using feedback from the wireless device 10, indicated with the dashed double arrow line. For example, as stated above the number of repetitions of the DL control channel may depend on feedback from the wireless device 10. The wireless device 10 may receive broadcasted information what repetition level the first network node 12 supports. The broadcast information may for example include 1-4 levels which correspond to 1-4 coverage enhancement levels. The wireless device 10 may indicate in its message sent to the first network node 12, e.g. RACH request, the required repetition level of DL control channel(s) and/or the coverage enhancement level under which it may operate with respect to the serving cell 11.

Additionally, or alternatively, the wireless device 10 may perform downlink measurements on the reference symbols to estimate the downlink link quality, QL. The wireless device 10 may use the estimated information on QL to more reliably choose the repetition level. In addition to the two examples above, the wireless device 10 could also use information on path loss information, wireless device transmission power information alone or in combination with the indication information from the first network node 12 to reliably choose the repetition level.

Action 403. The first network node 12 then transmits the DL control channel the determined number of repetitions within the cell 11.

Action 404. The wireless device 10 estimates a DL link quality of the DL control channel.

Action 405. The wireless device 10 compares the estimated DL link quality with a first threshold indicating an out of sync operation and a second threshold indicating an in sync operation, which thresholds are associated with different enhanced coverage levels and number of repetitions of a transmission of a DL control channel.

Action 406. The wireless device receives the DL control channel the number of repetitions within the cell, and performs RLM based on the comparison.

E.g. a method in wireless device 10 may comprise the actions of: - Performing measurement on downlink reference symbols (e.g. CRS) of the serving cell to estimate DL link quality (QL);

- Determining the coverage level of the WIRELESS DEVICE 10 wrt the serving cell based on estimated QL;

- Comparing the estimated DL link quality with radio link monitoring thresholds

Qout and Qin based on the determined coverage level of the wireless device 10:

... Qout is the level at which the downlink radio link cannot be reliably received and corresponds to X1 % block error rate (BLER) of a hypothetical DL control channel (e.g. M- PDCCH) as a function of at least 'X2' number of times the same DL control channel (e.g. M-PDCCH) with X3 OFDM resource elements is repeatedly transmitted by the serving cell during certain time period, T1 ; and

...Qin is the level at which the downlink radio link can be reliably received and correspond to Y1% block error rate of a hypothetical DL control channel (e.g. M-PDCCH) as a function of at least Ύ2' number of times the same DL control channel (e.g. M- PDCCH) with Y3 OFDM resource elements is repeatedly transmitted by the serving cell during certain time period, T2.

- Performing the DL radio link monitoring of the serving cell based on the comparison e.g. determine whether the wireless device 10 is in in-sync or out-sync.

For example; X1=10, X2=2, and X3 = 288 and/or Y1 =2 and Y2=4, and Y3 = 144. The wireless device 10 may be in out of sync if the BLER >= X1 %. In some embodiments the Qout corresponds to X1 % BLER of the hypothetical M-PDCCH, which is also the function of one or more of the following additional parameters: Number of receive antennas at the wireless device 10; Number of transmit antennas at the serving cell; Enhanced coverage level (e.g. coverage extension of 5 dB, 10 dB etc.); Configured or transmission bandwidth or BW of M-PDCCH and/or of DL reference signal; Duplex mode (e.g. FD-FDD, HD-FDD); Channel format (e.g. DCI format); Size of control channel e.g. number of OFDMA symbols for M-PDCCH; Transmit power of M-PDCCH e.g. ratio of M- PDCCH power to DL RS power; Frequency hopping occasion.

The wireless device 10 may be in in-sync if the BLER <= Y1%. The Qin may correspond to Y1% BLER of the hypothetical M-PDCCH, which is also the function of one or more of the following additional parameters: Number of receive antennas at the wireless device 10; Number of transmit antennas at the serving cell; Enhanced coverage level (e.g. coverage extension of 5 dB, 10 dB etc.); Configured or transmission bandwidth or BW of M-PDCCH and/or of DL reference signal; Duplex mode (e.g. FD-FDD, HD-FDD); Channel format (e.g. DCI format); Size of control channel e.g. number of OFDMA symbols for M-PDCCH; Transmit power of M-PDCCH e.g ratio of M-PDCCH power to DL RS power; Frequency hopping occasion.

In some embodiments a method provided in the first network node 12 enabling a wireless device 10 to perform radio link monitoring of a serving cell comprises the actions of:

- determining that the wireless device 10 capable of operating in enhanced coverage level is performing or is expected to perform radio link monitoring of the serving cell;

- adapting the number of times (Z, which may be X2 or Y2) the same DL control channel (e.g. M-PDCCH) is to be repeated for transmitting DL control channel (e.g. M-

PDCCH) during certain time period (T3), said DL control channel (e.g. M-PDCCH) is used or expected to be used by the wireless device 10 for RLM; and

- transmitting DL control channel (e.g. M-PDCCH) in the serving cell of the wireless device 10 with the determined value of Z.

The values may be Z=X2 and T3=T1 if it is determined that the wireless device 10 is or is expected to be in out-of-sync while performing the RLM.

The values may be Z=Y2 and T3=T2 if it is determined that the wireless device 10 is or is expected to be in in-sync while performing the RLM.

According to an aspect an object of improving the performance of the wireless communication network is achieved by a method performed by a network node for enabling a wireless device in a wireless communication network to perform radio link monitoring within a cell of the network node. The network node determines or adapts a number of repetitions of a transmission of a DL control channel for the wireless device based on an assumption that the wireless device is in an enhanced coverage mode. The network node then transmits the DL control channel the determined number of repetitions within the cell.

According to another aspect the object is further achieved by providing a method performed by a wireless device for performing RLM in a cell of a network node in a wireless communication network. The wireless device estimates a DL link quality and compares the estimated DL link quality with a first threshold indicating an out of sync operation and a second threshold indicating an in sync operation, which thresholds are associated with different enhanced coverage levels and number of repetitions of a transmission of a DL control channel. The wireless device receives the DL control channel a number of repetitions within the cell. The wireless device then performs RLM based on the comparison. In order to perform the methods herein a network node, exemplified by the first network node 12, is provided. Fig. 5 is a block diagram depicting the first network node 12 for enabling the wireless device 10 to perform radio link monitoring of the first cell 1 1 within which the first network node 2 is configured to serve the wireless device 10. The first network node 12 may comprise processing circuitry 501 to perform the methods disclosed herein.

The first network node 12 may be configured to obtain information indicating that the wireless device 10 is capable of operating under enhanced coverage, i.e. with one or more coverage enhancement levels, and information indicating that the wireless device 10 is performing or is expected to perform radio link monitoring of the first cell 1 1. E.g. the first network node 12 may comprise an obtaining module 502. The processing circuitry 501 and/or the obtaining module 502 may be configured to obtain information indicating that the wireless device 10 is capable of operating under enhanced coverage, i.e. with one or more coverage enhancement levels, and information indicating that the wireless device 10 is performing or is expected to perform radio link monitoring of the first cell 11.

The first network node 12 may be configured to adjust/determine or set repetition level or number of repetitions for the transmission of the DL control channel for the wireless device 10 based on an assumption that the wireless device is in an enhanced coverage mode or capable of enhanced coverage and that the wireless device 10 is performing or is to perform RLM. E.g. the first network node 12 may comprise an adjusting module 503. The processing circuitry 501 and/or the adjusting module 503 may be configured to adjust/determine or set repetition level or number of repetitions of the transmission of the DL control channel for the wireless device 10 based on an assumption that the wireless device is in an enhanced coverage mode or capable of enhanced coverage and that the wireless device 10 is performing or is to perform RLM.

The first network node 12, the processing circuitry 501 and/or the adjusting module 503 may be configured to broadcast information what repetition level the first network node 12 supports. The first network node 12, the processing circuitry 501 and/or the adjusting module 503 may then be configured to receive a message e.g. a request from the wireless device 10 informing the repetition level of that particular wireless device 10. Additionally or alternatively, the first network node 12 the processing circuitry 501 and/or the adjusting module 503 may then receive information based on downlink measurements on the reference symbols from the wireless device 10 informing the repetition level of that particular wireless device 10. The first network node 12, the processing circuitry 501 and/or the adjusting module 503 may be configured to determine the coverage level of the wireless device 10, e.g. SINR or SNR of the wireless device with regards to the first cell 11. For example the first network node 12, the processing circuitry 501 and/or the adjusting module 503 may be configured to measure uplink received signal from the wireless device 10 and translate it to downlink received signal quality at the wireless device 10 by taking into account cell load, e.g. BS transmit power, number of active wireless devices in the first cell 11 etc. The first network node 12, the processing circuitry 501 and/or the adjusting module 503 may be configured to use a mapping table which maps the required repetition level of the DL control channel and the coverage level i.e. the estimated DL signal quality, to adjust the number of repetitions.

The first network node 12 is configured to transmit one or more DL control channels in the first cell 11 of the first network node 12 the adjusted number of repetitions or times. E.g. the first network node 12 may comprise a transmitting module 504. The processing circuitry 501 and/or the transmitting module 504 may be configured to transmit the DL control channel in the first cell 11 of the first network node 12 repeatedly the adjusted number of repetitions or times.

The processing circuitry 501 and/or the adjusting module 503 may be configured to adjust/adapt the number of repetitions of the transmission of the DL control channel for the wireless device 10 based or depending upon the actual coverage level of the wireless device 10 e.g. received signal quality from the wireless device 10 in the first cell 11.

The first network node 12 further comprises a memory 505. The memory comprises one or more units to be used to store data on, such as wireless device capability, SNR, SINR, link quality, thresholds, repetition levels, number of repetitions, coverage enhancement levels, applications to perform the methods disclosed herein when being executed, and similar.

The methods according to the embodiments described herein for the first network node 12 may be implemented by means of e.g. a computer program 506 or a computer program product, 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 first network node 12. The computer program 506 may be stored on a computer-readable storage medium 507, e.g. a disc or similar. The computer-readable storage medium 507, having stored thereon the computer program, 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 first network node 12. In some embodiments, the computer-readable storage medium may be a non-transitory computer-readable storage medium.

In order to perform the methods herein a wireless device, exemplified by wireless device 10, is provided. Fig. 6 is a block diagram depicting the wireless device 10 for performing RL in the first cell 1 1 within which the wireless device (10) is configured to be served by the first network node 12. The wireless device 0 may comprise processing circuitry 601 to perform the methods disclosed herein.

The wireless device 10 is configured to perform a radio measurement on downlink reference symbols of the first cell 11 to estimate DL link quality. For example, the wireless device 10 may comprise an estimating module 602. The processing circuitry 601 and/or the estimating module 602 may be configured to perform the radio measurement on downlink reference symbols of the first cell 1 1 to estimate DL link quality.

The wireless device 10 is configured to compare the estimated DL link quality with radio link monitoring thresholds. For example, the wireless device 10 may comprise a comparing module 603. The processing circuitry 601 and/or the comparing module 603 may be configured to compare the estimated DL link quality with radio link monitoring thresholds.

The wireless device 10 is configured to perform the RLM of the first cell 11 based on the comparison e.g. to determine whether the wireless device 10 is in-sync or out-of- sync. For example, the wireless device 10 may comprise an RLM module 604. The processing circuitry 601 and/or the RLM module 604 may be configured to perform the RLM of the first cell 11 based on the comparison e.g. determining whether the wireless device 10 is in-sync or out-of-sync.

The wireless device 10 may configured to receive broadcasted information indicating what repetition level the first network node 12 supports. The broadcasted information may for example include 1-4 levels which correspond to 1-4 coverage enhancement levels. The wireless device 10 may further be configured to indicate in its message sent to the first network node 12, e.g. RACH request, the required repetition level of DL control channel(s) and/or the coverage enhancement level under which it may operate with respect to the serving cell 11. The wireless device 10 may be configured perform downlink measurements on the reference symbols to estimate the downlink link quality, QL. The wireless device 10 may then be configured to use the estimated information on QL to more reliably choose the repetition level. In addition the wireless device 10 may also be configured to use information on path loss information, wireless device transmission power information alone or in combination with the indication information from the first network node 12 to reliably choose the repetition level. For example, the wireless device 10 may comprise a communicating module 605. The processing circuitry 601 and/or the communicating module 605 may be configured to receive broadcasted information indicating what repetition level the first network node 12 supports. The broadcasted information may for example include 1-4 levels which correspond to 1-4 coverage enhancement levels. The processing circuitry 601 and/or the communicating module 605 may further be configured to indicate in its message sent to the first network node 12, e.g. RACH request, the required repetition level of DL control channel(s) and/or the coverage enhancement level under which it may operate with respect to the first cell 11. The processing circuitry 601 and/or the estimating module 602 may be configured to perform downlink measurements on the reference symbols to estimate the downlink link quality, QL. The processing circuitry 601 and/or the communicating module 605 may then be configured to use the estimated information on QL to more reliably choose the repetition level. In addition the processing circuitry 601 and/or the communicating module 605 may be configured to use information on path loss information, wireless device transmission power information alone or in combination with the indication information from the first network node 12 to reliably choose the repetition level.

The wireless device 10 further comprises a memory 606. The memory comprises one or more units to be used to store data on, such as wireless device capability, SNR, SINR, link quality, thresholds, repetition levels, coverage enhancement levels, applications to perform the methods disclosed herein when being executed, and similar.

The methods according to the embodiments described herein for the wireless device 10 are respectively implemented by means of e.g. a computer program 607 or a computer program product, 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 10. The computer program 607 may be stored on a computer-readable storage medium 608, e.g. a disc or similar. The computer-readable storage medium 608, having stored thereon the computer program, 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 10. In some embodiments, the computer-readable storage medium may be a non-transitory computer-readable storage medium. In some embodiments a more general term "network node" is used and it can correspond to any type of radio network node or any network node, which communicates with a UE and/or with another network node. Examples of network nodes are NodeB, MeNB, SeNB, a network node belonging to MCG or SCG, base station (BS), multi- standard radio (MSR) radio node such as MSR BS, eNodeB, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS), core network node (e.g. MSC, MME etc), O&M, OSS, SON, positioning node (e.g. E-SMLC), MDT etc.

In some embodiments the non-limiting term user equipment (UE) is used and it refers to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile communication system. Examples of UE are target device, device to device (D2D) UE, proximity capable UE (aka ProSe UE), machine type UE or UE capable of machine to machine (M2M) communication, PDA, PAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles etc.

The embodiments are applicable to single carrier as well as to multicarrier or carrier aggregation (CA) operation of the UE in which the UE 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 embodiments are described for LTE. However the embodiments are applicable to any RAT or multi-RAT systems, where the UE receives and/or transmit signals (e.g. data) e.g. LTE FDD/TDD, WCDMA/HSPA, GSM/GERAN, Wi Fi, WLAN, CDMA2000 etc.

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 wireless device or 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. Other hardware, conventional and/or custom, may also be included. Designers of communications devices will appreciate the cost, performance, and maintenance tradeoffs inherent in these design choices.

Modifications and other embodiments of the disclosed embodiments will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the embodiment(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

ABBREVIATIONS

ACK Acknowledged

ADC Analog-to-digital conversion

AGC Automatic gain control

ANR Automatic neighbor relations

AP Access point

BCH Broadcast channel

BLER Block error rate

BS Base station

BSC Base station controller

BTS Base transceiver station CA Carrier aggregation

CC Component carrier

CG Cell group

CGI Cell global identity

CP Cyclic prefix

CPICH Common pilot channel

CQI Channel Quality Indicator

CSG Closed subscriber group

DAS Distributed antenna system

DC Dual connectivity

DFT Discrete Fourier Transform

DL Downlink

DL-SCH Downlink shared channel

DRX Discontinuous reception

EARFCN Evolved absolute radio frequency channel number

ECGI Evolved CGI

eNB eNodeB

FDD Frequency division duplex

FFT Fast Fourier transform

HD-FDD Half duplex FDD

HO Handover

ID Identity

M2 machine to machine

MAC Media access control

MCG Master cell group

MDT Minimization of drive tests

MeNB Master eNode B

MIB Master information block

MME Mobility management entity

MRTD Maximum receive timing difference

MSR Multi-standard radio

NACK Not acknowledged

OFDM Orthogonal frequency division multiplexing

Rl Rank Indicator

SI System Information PCC Primary component carrier

PCI Physical cell identity

PCell Primary Cell

PCG Primary Cell Group

PCH Paging channel

PDU Protocol data unit

PGW Packet gateway

PHICH Physical HARQ indication channel

PLMN Public land mobile network

PMI Precoding Matrix Indicator

PSCell Primary SCell

PSC Primary serving cell

PSS Primary synchronization signal

RAT Radio Access Technology

RF Radio frequency

RLM Radio link monitoring

RNC Radio Network Controller

RRC Radio resource control

RRH Remote radio head

RRU Remote radio unit

RSCP Received signal code power

RSRP Reference Signal Received Power

RSRQ Reference Signal Received Quality

RSSI Received signal strength indication

RSTD Reference signal time difference

RV Redundancy version

Rx Receiver

sec Secondary component carrier

SCell Secondary Cell

SCG Secondary Cell Group

SeNB Secondary eNode B

SFN System frame number

SGW Signaling gateway

SI System information

SIB System information block SIB1 System information block type 1

SINR Signal to interference and noise ratio

SON Self-organizing networks

SSC Secondary serving cell

SSS Secondary synchronization signal

TA Timing advance

TAG Timing advance group

TDD Time division duplex

Tx Transmitter

UARFCN UMTS Absolute Radio Frequency Channel Number

UE User equipment

UL Uplink

APPENDIX RAN4 has discussed RRM measurement performance for normal and enhanced coverage for the last few meetings. The next steps include defining the core requirements, and radio link monitoring is a core part of that. RAN4 did define new RLM requirements for Rel-12 categories 0 UEs in section 7.1 1 of TS 36.133 because of its single receive antenna property as main difference. Similarly, RAN4 needs to develop new RLM requirements for Rel-13 MTC UEs which have different capabilities than Rel-12 category 0 UEs. In this paper we discuss the motivation to define new RLM requirements. Our companion paper includes simulation assumptions for RLM [1].

Discussion on RLM for Rel-13 MTC UEs

The purpose of radio link monitoring is to monitor the radio link quality of the connected serving cell and use that information to decide whether UE is in in-sync or out-of-sync to that serving cell. UE performs measurement on downlink cell-specific reference symbols (CRS) for this purpose and this procedure is carried out by UEs in RRC_CONNECTED state.

Both PDCCH and PCFICH performance are used to evaluate the RLM performance in legacy RLM procedure. PCFICH is a cell-specific channel meaning that all UEs in a cell will share the same PCFICH parameters. According to latest RA 1 agreements [2], Rel- 13 MTC UEs are not required to monitor the wideband channels, e.g. PDCCH/PCFICH. This will have an impact on existing way of performing RLM procedure since existing procedure uses PDCCH/PCFICH.

Observation #1: Rel-13 low complexity UEs and enhanced coverage UEs are not required to receive legacy PCFICH and legacy PDCCH.

Since Rel-13 LC/EC UEs support operation in both normal coverage and enhanced coverage, it is expected that RLM requirements will be different. For example, one set of transmission parameters of the control channels may be used for normal coverage operation while another set of transmission parameters may be used in enhanced coverage. Therefore the requirements and the SNR levels may depend on the coverage scenario.

Proposal #1 : RAN4 needs to define RLM requirements for UEs under normal coverage and enhanced coverage separately for Rel-13 MTC.

Normal Coverage:

Although Rel-13 MTC normal coverage UEs are expected to have the same or similar coverage as legacy Rel-12 category 0 UEs, new RLM requirements are necessary to be specified to secure the same RLM performance as Rel-12 category 0 UE. The main motivation is that Rel-12 category 0 RLM requirements are based on PDCCH and PCFICH which is not the case for Rel-13. With reference to Observation#1 , Rel-13 MTC UEs are not required to receive legacy wideband channels including PDCCH/PCFICH. As a result the existing RLM procedure cannot be reused. With reference to RAN1 agreements [2], however, a new channel, namely M-PDCCH, has been introduced for Rel-13 MTC UEs. RAN4 needs to study RLM performance using the new M-PDCCH channel and the new RLM requirements should be defined accordingly. It should be also noted that M-PDCCH is transmitted on 6 or smaller number of PRBs regardless of the system bandwidth, and it is assumed to be demodulated with DM-RS. Moreover, RAN1 has agreed to introduce the frequency hopping which changes the resource blocks within the system bandwidth and it will combat frequency fading.

Proposal #2: RAN4 needs to study RLM performance using M-PDCCH channel for Rel-13 MTC UEs under normal coverage.

Enhanced Coverage:

The main motivation of Rel-13 MTC operation under enhanced coverage is to enable UE to operate under low SNR levels by extending the coverage. Various enhancement techniques are used to achieve this, e.g. additional aggregation level and repetitions of control channels including M-PDCCH. RAN1 has agreed to introduce a new aggregation level 24 that would be useful for enhancement coverage. The repetition level will be a function of coverage enhancement level. For instance, coverage extension of 5 dB may require N number of repetition of M-PDCCH while coverage extension of 10 dB may require N+M number of repetitions. Obviously, this has a strong relation to achievable BLER of the channel. Since RLM is based BLER performance of control channel (M- PDCCH), this needs to be studied when defining the RLM requirements for enhanced coverage.

Proposal #3. RAN4 needs to study RLM performance using M-PDCCH and repetitions for Rel-13 UEs under enhanced coverage.

RLM Performance Parameters:

The main RLM parameters used to define RLM requirements are:

Out of Sync (OOS) and In Sync (IS) thresholds

Evaluation period of DL radio signal quality for OOS and IS detections

Control channel transmission parameters for applicability of OOS and IS detection

OOS and IS thresholds correspond to 10% and 2% of hypothetical BLER of the control channel (PDCCH in Rel-12). It is our view that same OOS and IS thresholds can be made applicable also for Rel-13 MTC UEs. The legacy RLM procedure comprises a mapping between measured reference symbols and hypothetical BLER of PDCCH transmissions. A similar mapping between the RS and hypothetical BLER of M-PDCCH transmissions is needed for Rel-13 MTC UEs. This mapping is implementation specific. It is expected that the SNR levels which correspond to the OOS and IS threshold may change for this new type of UEs due to the new channel, characteristics of the UE, and operating scenario. As mentioned earlier, M-PDCCH channel may use repetitions and frequency hopping.

The new BLER mapping of M-PDCCH transmissions may depend on several parameters such as repetition levels, coverage areas, number of receive antennas, transmit antennas, DCI format, duplex mode, aggregation level, control channel region etc. As an example, at legacy SNR levels, e.g. -6 dB SNR, BLER may be as good as in legacy RLM procedure, but at even lower SNR levels for coverage enhancement, e.g. -12 dB the BLER performance might be significantly degraded. The BLER of new channel may depend on these parameters and the new requirements should take into account them.

Proposal #4: A new BLER mapping of hypothetical M-PDCCH transmissions are needed for Rel-13 MTC UEs.

Initial Link Simulation Results for normal coverage In this section we present initial link level simulation results for RLM under normal coverage.

Figure 7 and Figure 8 show RLM simulation results for ETU30 channel according to simulation parameters in respectively in the proposed simulation assumptions in [1], For reference, we compare M-PDCCH with PDCCH/PCFICH. Note that no power boosting was applied to any of the control channels.

It should be noted that RAN1 is still discussing the DCI formats corresponding to DCI 1C and 1A, frequency hopping pattern parameter, and repetition level. Therefore, in this simulation, we set the same number of bits used for PDCCH, i.e., 13 bits for in-sync scenario and 27 bits fir out-of-sync scenario. Also no frequency hopping was enabled. The results in Figure 7 and 8 show the result of repetition level 10 and 50 only with the aggregation level 16.

It is observed from these figures that a higher aggregation level might be needed for M- PDCCH to meet the same SNR-BLER target as PDCCH. One reason is that fewer number of OFDM channel symbols are used for M-PDCCH compared to PDCCH; this means the coding rate of M-PDCCH is higher than PDCCH. Another reason is that M- PDCCH is transmitted within 6 PRBs whereas PDCCH is transmitted over 50RPB when the system bandwidth is 10MHz. the narrowband transmission degrades performance especially in the fading condition such as ETU30. Therefore aggregation level 16 for out- of-sync and 8 for in-sync may be considered. Frequency hopping should also be considered because of narrower band transmissions.

The presented results and discussion above is for the normal coverage scenario. For the enhanced coverage case, RLM should be studied with more repetitions as well as with higher aggregation levels. However RAN4 should wait for the RAN1 conclusion regarding the coverage enhancement parameters such as repetition level, PDSCH MCS, etc... It should be also noted that the measurement period may need to be extended with the increased repetition level. RAN4 should discuss the extension of T1 -T5 used for in-sync and out-of-sync requirement.

Observation #3: RLM performance is degraded with M-PDCCH compared to PDCCH. More specifically, the required SNR levels to meet the in-sync and out-of-sync BLER targets are much higher for M-PDCCH compared to PDCCH.

Conclusion

RLM requirements are discussed herein for Rel-13 MTC UEs under normal and enhanced coverage. The rationale for defining two separate requirements for normal and enhanced coverage is also explained. Based on the discussions, we make the following

observations and proposals:

Observation #1 : Rel-13 low complexity UEs and enhanced coverage UEs are not required to receive legacy PCFICH and legacy PDCCH.

Observation #2: Due to that Rel-13 MTC UEs do not read PCFICH some change in M- PDCCH decoding technique is expected compared to legacy RLM procedure which is based on PDCCH and PCFICH.

Proposal #1 : RAN4 needs to define RLM requirements for UEs under normal coverage and enhanced coverage separately.

Proposal #3: RAN4 needs to study RLM performance using M-PDCCH and repetitions for Rel-13 UEs under enhanced coverage.

[1] R4-156301 , "Simulation Assumptions for RLM", Ericsson, October. 2015

[2] RP-141785, "Status Report to TSG" Ericsson, December 2014.

Claims

A method performed by a network node (12) for enabling a wireless device (10) in a wireless communication network (1) to perform radio link monitoring, RLM, of a cell (11) within which the wireless device (10) is served by the network node (12), the method comprising:

- determining (205) a repetition level for a transmission of a Downlink, DL, control channel for the wireless device (10) based on a coverage level of the wireless device (10) with respect to the cell (11), and

- transmitting (207) the DL control channel in the cell (11) repeatedly a number of times in accordance with the determined repetition level.

2. A method according to claim 1 , wherein the determining (205) comprises: - determining a first repetition level for the transmission of the DL control channel associated with a first link quality threshold indicating an out-of-sync operation of the wireless device (10) and a second repetition level for the transmission of the DL control channel associated with a second link quality threshold indicating an in- sync operation of the wireless device (10), which thresholds are dependent on the coverage level of the wireless device (10) with respect to the cell (11); and then - transmitting (207) the DL control channel a number of times prescribed by the determined first repetition level when the wireless device (10) is in out-of-sync operation and a number of times prescribed by the determined second repetition level when the wireless device (10) is in in-sync operation.

A method according to any of the claims 1-2, wherein the determining (205) the repetition level is based on an assumption that the wireless device (10) i in an enhanced coverage mode with respect to the cell (11).

A method according to any of the claims 1-3, further comprising

determining (206) an aggregation level for the DL control channel based on the coverage level of the wireless device (10) with respect to the cell (1 1), and

transmitting (207) the DL control channel with the determined aggregation level in the cell (11).

A method according to any of the claims 1-4, further comprising:

- obtaining (203) information that the wireless device (10) is capable of operating under enhanced coverage with respect to the first cell (11) and is performing or is expected to perform radio link monitoring of the cell (11).

A method according to any of the claims 1-5, further comprising:

- adapting (208) the repetition level for the transmission of the DL control channel when the coverage level changes, said DL control channel being used or expected to be used by the wireless device (10) for performing RLM.

A method according to any of the claims 1-6, further comprising:

- broadcasting (201) information indicating the repetition level for the transmission of the DL control channel for the wireless device (10).

A method according to any of the claims 1-6, further comprising:

- broadcasting (201) information indicating one or more repetition levels supported by the network node (12); and

- receiving (202) information from the wireless device (10), said information indicating at least one repetition level supported by that wireless device (10).

A method according to any of the claims 1-8, further comprising:

- determining (204) the coverage level of the wireless device (10) with respect to the cell (11) and wherein the determining (205) the repetition level comprises using a mapping table which maps a required repetition level for the DL control channel and the determined coverage level.

10. A method according to any of the claims 1-9, wherein the transmitting (207) further comprises transmitting the DL control channel using a certain reference value for the repetition level and adapting the reference value depending upon the actual coverage level of the wireless device (10), and then transmitting the DL control channel using the adapted reference value for the repetition level in order to enable the wireless device (10) to perform the RLM even if the coverage level changes over time.

1 1. A method according to any of the claims 1-10, wherein the determining (204) the coverage level of the wireless device (10) with respect to the cell (11) is based on one or more of the following:

random access transmission of the wireless device (10) in the cell (11); signal quality of wireless device (10) with respect to the cell (11), path loss between the wireless device (10) and the cell (11); and

- transmit power of the wireless device (10).

12. A method performed by a wireless device (10) for performing Radio Link

Monitoring, RLM, of a cell (1 1) within which the wireless device (10) is served by a network node (12) in a wireless communication network (1), the method comprising:

- determining (305) a repetition level for a transmission of a Downlink, DL, control channel for the wireless device (10) based on a coverage level of the wireless device (10) with respect to the cell (11), and

- performing (310) RLM based on the determined repetition level for the transmission of the DL control channel, wherein the repetition level indicates a number of times that the DL control channel is to be repeatedly transmitted in the cell (11) by the network node (12).

13. A method according to claim 12 further comprising:

- estimating (303) a downlink, DL, link quality by performing a radio measurement on downlink reference symbols of the cell (11);

- comparing (309) the estimated DL link quality with a first link quality threshold indicating an out-of-sync operation of the wireless device 10 and a second link quality threshold indicating an in-sync operation of the wireless device 10, which thresholds are associated with the coverage level and a respective number of repetitions of a transmission of the DL control channel; and wherein the performing (310) the RLM is based on the comparison.

14. A method according to claim 13, further comprising:

- determining (304) the coverage level of the wireless device with respect to the cell (11) based on the estimated DL link quality.

15. A method according to claim 14, wherein the determining (304) the coverage level of the wireless device (10) with respect to the cell (11) is based on one or more of the following:

random access transmission of the wireless device (10) in the cell (11); - path loss between the wireless device (10) and the cell (11); and

- transmit power of the wireless device (10).

16. A method according to any of the claims 12-15, further comprising:

determining (306) an aggregation level for a transmission of the DL control channel based on the coverage level of the wireless device (10) with respect to the cell (11); and wherein the performing (310) the RLM is based on the determined aggregation level for the transmission of the DL control channel.

17. A method according to any of the claims 12-16, further comprising:

- receiving (307) the DL control channel repeatedly the number of times within the cell (11); and combining all or certain number of repetitions and then performing (310) the RLM based on the comparison and the repetitively received DL control channel.

18. A method according to any of the claims 12-17, wherein the thresholds are different for different coverage levels.

19. A method according to any of the claims 12-18, further comprising:

- transmitting (302), to the network node (12), information that the wireless device (10) is capable of operating under enhanced coverage and is performing or is expected to perform radio link monitoring of the cell (11).

20. A method according to any of the claims 12-19, further comprising:

- receiving (301) broadcasted information indicating a repetition level supported by the network node (12); and

- transmitting (302) information from the wireless device (10), said information indicating the repetition level supported by that particular wireless device (10).

21 A method according to any of the claims 12-20, further comprising: - selecting (308), based on the determination of the coverage level, one of a plurality of mapping tables, which selected mapping table is used for estimating the hypothetical Block Error Rate, BLER, which in turn is used to determine whether the wireless device (10) is in in-sync or out-sync when performing (310) the RLM.

22. A network node (12) for enabling a wireless device (10) in a wireless

communication network (1) to perform radio link monitoring, RLM, of a cell (11) within which the network node (12) is configured to serve the wireless device (10), the network node (12) being configured to:

determine a repetition level for a transmission of a Downlink, DL, control channel for the wireless device (10) based on a coverage level of the wireless device (10) with respect to the cell (11), and to

transmit the DL control channel in the cell (1 1) repeatedly a number of times in accordance with the determined repetition level.

23. A network node (12) according to claim 21 , being configured to determine the number of repetitions by being configured to determine a first repetition level for the transmission of the DL control channel associated with a first link quality threshold indicating an out-of-sync operation of the wireless device (10) and a second repetition level for a transmission of the DL control channel associated with a second link quality threshold indicating an in-sync operation of the wireless device (10), which thresholds are dependent on the coverage level of the wireless device (10) with respect to the cell (11), and the network node (12) is further configured to transmit the DL control channel a number of times prescribed by the determined first repetition level when the wireless device (10) is in out-of-sync operation and a number of times prescribed by the determined second repetition level when the wireless device (10) is in in-sync operation.

24. A network node (12) according to any of the claims 22-23, being configured to determine the repetition level based on an assumption that the wireless device (10) is in an enhanced coverage mode with respect to the cell (11).

25. A network node (12) according to any of the claims 22-24, further being configured to determine an aggregation level of the DL control channel based on the coverage level of the wireless device (10) with respect to the cell (11), and to transmit the DL control channel with the determined aggregation level in the cell (11).

26. A network node (12) according to any of the claims 22-25, further being

configured to obtain information that the wireless device (10) is capable of operating under enhanced coverage with respect to the cell (11) and is performing or is expected to perform radio link monitoring of the cell (11).

27. A network node (12) according to any of the claims 22-26, further being

configured to adapt the repetition level for the transmission of said DL control channel when the coverage level changes, said DL control channel being used or expected to be used by the wireless device (10) for performing RLM.

28. A network node (12) according to any of the claims 22-27, further being

configured to broadcast information indicating one or more repetition levels supported by the network node (12); and to receive information from the wireless device (10), said information indicating at least one repetition level supported by that wireless device (10).

29. A network node (12) according to any of the claims 22-28, further being

configured to determine coverage level of the wireless device (10) with respect to the first cell (11) and then to determine the repetition level by using a mapping table which maps a required repetition level for the DL control channel and the determined coverage level.

30. A network node (12) according to any of the claims 22-29, being configured to transmit the DL control channel using a certain reference value for the repetition level and adapting the reference value depending upon the actual coverage level of the wireless device (10), and then to transmit the DL control channel using the adapted reference value for the repetition level in order to enable the wireless device (10) to perform the RLM even if coverage level changes over time.

31. A network node (12) according to any of the claims 22-30, being configured to determine coverage level of the wireless device (10) with respect to the cell (11) based on one or more of the following:

- random access transmission of the wireless device (10) in the cell (11); signal quality of wireless device (10) with respect to the cell (11), path loss between the wireless device (10) and the cell (11); and

- transmit power of the wireless device (10).

32. A wireless device (10) for performing Radio Link Monitoring, RLM, of a cell (11) within which the wireless device (10) is configured to be served by a network node (12) in a wireless communication network (1), the wireless device (10) being configured to:

perform RLM based on the determined repetition level for the transmission of the DL control channel, wherein the repetition level indicates a number of times that the DL control channel is to be repeatedly transmitted in the cell (11) by the network node (12).

33. A wireless device (10) according to claim 32 further being configured to:

estimate a downlink, DL, link quality by performing a radio measurement on downlink reference symbols of the cell (11);

compare the estimated DL link quality with a first link quality threshold indicating an out-of-sync operation and a second link quality threshold indicating an in-sync operation, which thresholds are associated with the coverage level and a respective number of repetitions of a transmission of the DL control channel; and

to perform the RLM based on the comparison.

34. A wireless device (10) according to claim 33, further being configured to

determine the coverage level of the wireless device with respect to the cell (11) based on the estimated DL link quality.

A wireless device (10) according to claim 34, being configured to determine the coverage level of the wireless device (10) with respect to the cell (11) based on one or more of the following:

random access transmission of the wireless device (10) in the cell (11); path loss between the wireless device (10) and the cell (11); and

- transmit power of the wireless device (10).

. A wireless device (10) according to any of the claims 32-35, further being configured to

determine an aggregation level for a transmission of the DL control channel based on the coverage level of the wireless device (10) with respect to the cell (11); and to perform the RLM based on the determined aggregation level for the transmission of the DL control channel.

37. A wireless device (10) according to any of the claims 32-36, further being

configured to

receive the DL control channel repeatedly the number of times within the cell (11); and combining all or certain number of repetitions and then to perform the RLM based on the comparison and the repetitively received DL control channel.

38. A wireless device (10) according to any of the claims 32-37, wherein the

thresholds are different for different coverage levels.

39. A wireless device (10) according to any of the claims 32-38, further being

configured to transmit, to the network node (12), information that the wireless device (10) is capable of operating under enhanced coverage and is performing or is expected to perform radio link monitoring of the cell (11).

. A wireless device (10) according to any of the claims 32-39, further being configured to

receive broadcasted information indicating a repetition level supported by the network node (12); and to

transmit information from the wireless device (10), said information indicating the repetition level supported by that particular wireless device (10). A wireless device (10) according to any of the claims 32-40, further being configured to

select, based on the determination of the coverage level, one of a plurality of mapping tables, which selected mapping table is used for estimating the hypothetical Block Error Rate, BLER, which in turn is used to determine whether the wireless device (10) is in in-sync or out-sync when performing the RLM.