KR20210054701A - Method and apparatus for performing cell reselection on unlicensed band in next generation mobile communication system - Google Patents

Abstract

The present invention relates to a communication technique that converges a 5G communication system with an IoT technology to support higher data rates after a 4G system and a system thereof. The present invention can be applied to intelligent services (eg, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail business, security and safety related services, etc.) based on a 5G communication technology and an IoT-related technology. According to the present invention, disclosed are a method for reporting heating-related information of a terminal and a device thereof. According to the present invention, disclosed are a method for reselecting a cell on an unlicensed band and a device thereof.

Description

Method and apparatus for performing cell reselection operation in unlicensed band in next-generation mobile communication system {METHOD AND APPARATUS FOR PERFORMING CELL RESELECTION ON UNLICENSED BAND IN NEXT GENERATION MOBILE COMMUNICATION SYSTEM}

The present disclosure relates to an operation of a terminal and a base station in a mobile communication system, and specifically, to a method and an apparatus for performing a cell reselection operation in an unlicensed band.

Efforts are being made to develop an improved 5G communication system or a pre-5G communication system in order to meet the increasing demand for wireless data traffic after the commercialization of 4G communication systems. For this reason, a 5G communication system or a pre-5G communication system is called a Beyond 4G Network communication system or an LTE system and a Post LTE system. The 5G communication system defined by 3GPP is called the New Radio (NR) system.

In order to achieve a high data rate, the 5G communication system is being considered for implementation in the ultra-high frequency (mmWave) band (eg, such as the 60 Giga (60 GHz) band). In order to mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, 5G communication systems include beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO). ), array antenna, analog beam-forming, and large scale antenna techniques were discussed and applied to NR systems.

In addition, in order to improve the network of the system, in 5G communication systems, evolved small cells, advanced small cells, cloud radio access networks (cloud RAN), and ultra-dense networks. , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation And other technologies are being developed.

In addition, in 5G systems, advanced coding modulation (ACM) methods such as Hybrid FSK and QAM Modulation (FQAM) and SWSC (Sliding Window Superposition Coding), advanced access technologies such as Filter Bank Multi Carrier (FBMC), NOMA (non-orthogonal multiple access), and sparse code multiple access (SCMA) have been developed.

Meanwhile, the Internet is evolving from a human-centered connection network in which humans create and consume information, to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. Internet of Everything (IoE) technology, which combines IoT technology with big data processing technology through connection with cloud servers, is also emerging. In order to implement IoT, technological elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required. , M2M), and MTC (Machine Type Communication) technologies are being studied. In the IoT environment, intelligent IT (Internet Technology) services that create new value in human life by collecting and analyzing data generated from connected objects can be provided. IoT is the field of smart home, smart building, smart city, smart car or connected car, smart grid, healthcare, smart home appliance, advanced medical service, etc. through the convergence and combination of existing IT (Information Technology) technology and various industries. Can be applied to.

Accordingly, various attempts have been made to apply a 5G communication system to an IoT network. For example, 5G communication such as a sensor network, machine to machine (M2M), and machine type communication (MTC) is implemented by techniques such as beamforming, MIMO, and array antenna. The application of a cloud radio access network (cloud RAN) as the big data processing technology described above can be said as an example of the convergence of 5G technology and IoT technology.

On the other hand, research on unlicensed bands has been continuously conducted with the development of communication systems.

An object of the present disclosure is to support a smooth operation of a terminal in an unlicensed band by proposing a cell reselection operation performed in an unlicensed band.

A method according to an embodiment for solving the above-described problem includes: receiving system information including a parameter for cell reselection from a base station; Performing measurements on a plurality of cells on the unlicensed band; Determining a ranking of each of the plurality of cells based on the signal strength quality values measured for the plurality of cells; Selecting a cell corresponding to a registered public land mobile network (PLMN) from among one or more cells selected in the order of the highest ranking value and having the largest number of beams having a signal strength equal to or greater than a threshold value, based on the parameter; And performing reselection to the selected cell.

According to the proposed embodiments, the cell reselection operation can be efficiently performed in the unlicensed band, and thus the terminal can operate smoothly in the unlicensed band.

1A is a diagram showing the structure of a next-generation mobile communication system.
1B shows a process in which frequency-specific priority information for cell reselection in the present invention is broadcast through a system information block (SIB) or applied to a specific terminal through an RRC Connection Release message, which is a dedicated radio resource control (RRC) signaling. It is a drawing for explanation.
1C is a diagram illustrating a method of performing cell reselection by a UE in connection with the present disclosure.
1D is a diagram for explaining an operation of a terminal performing cell reselection in an intra-frequency or an inter-frequency having the same priority in relation to the present disclosure.
FIG. 1E is a diagram illustrating a terminal operation for performing cell reselection in an intra-frequency or an inter-frequency having the same priority in a licensed frequency band according to the present disclosure.
FIG. 1F is a diagram for explaining an operation of a terminal performing cell reselection in an intra-frequency or an inter-frequency having the same priority in an unlicensed frequency band according to the present disclosure.
1H is a block diagram illustrating an internal structure of a terminal according to the present disclosure.
1I is a block diagram showing the configuration of a base station according to the present disclosure.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

For the same reason, some elements in the accompanying drawings are exaggerated, omitted, or schematically illustrated. In addition, the size of each component does not fully reflect the actual size. The same reference numerals are assigned to the same or corresponding components in each drawing.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments make the disclosure of the present invention complete, and the general knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to the possessor, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

At this time, it will be appreciated that each block of the flowchart diagrams and combinations of the flowchart diagrams may be executed by computer program instructions. Since these computer program instructions can be mounted on the processor of a general purpose computer, special purpose computer or other programmable data processing equipment, the instructions executed by the processor of the computer or other programmable data processing equipment are described in the flowchart block(s). It creates a means to perform functions. These computer program instructions can also be stored in computer-usable or computer-readable memory that can be directed to a computer or other programmable data processing equipment to implement a function in a particular way, so that the computer-usable or computer-readable memory It is also possible for the instructions stored in the flow chart to produce an article of manufacture containing instruction means for performing the functions described in the flowchart block(s). Since computer program instructions can also be mounted on a computer or other programmable data processing equipment, a series of operating steps are performed on a computer or other programmable data processing equipment to create a computer-executable process to create a computer or other programmable data processing equipment. It is also possible for instructions to perform processing equipment to provide steps for executing the functions described in the flowchart block(s).

In addition, each block may represent a module, segment, or part of code that contains one or more executable instructions for executing the specified logical function(s). In addition, it should be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or the blocks may sometimes be executed in the reverse order depending on the corresponding function.

In this case, the term'~ unit' used in this embodiment refers to software or hardware components such as FPGA or ASIC, and'~ unit' performs certain roles. However,'~ part' is not limited to software or hardware. The'~ unit' may be configured to be in an addressable storage medium, or may be configured to reproduce one or more processors. Thus, as an example,'~ unit' refers to components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, and procedures. , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, database, data structures, tables, arrays, and variables. Components and functions provided in the'~ units' may be combined into a smaller number of elements and'~ units', or may be further separated into additional elements and'~ units'. In addition, components and'~ units' may be implemented to play one or more CPUs in a device or a security multimedia card.

1A is a diagram showing the structure of a next-generation mobile communication system.

Referring to FIG. 1A, as shown, a radio access network of a next-generation mobile communication system (New Radio, NR) includes a next-generation base station (New Radio Node B, hereinafter referred to as gNB) (1a-10) and an AMF (Access Management Function 1a-05). , That is, an entity of the New Radio Core Network). The user terminal (New Radio User Equipment, hereinafter referred to as NR UE or terminal) 1a-15 accesses the external network through the gNB 1a-10 and the AMF 1a-05.

In FIG. 1A, the gNB corresponds to an evolved node B (eNB) of an existing LTE system. The gNB is connected to the NR UE through a radio channel and can provide a service superior to that of the existing Node B (1a-20). In the next-generation mobile communication system, since all user traffic is serviced through a shared channel, a device that collects and schedules status information such as buffer status, available transmission power status, and channel status of UEs is required. 1a-10) is in charge. One gNB typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the existing LTE, it may have more than the existing maximum bandwidth, and an orthogonal frequency division multiplexing (hereinafter referred to as OFDM) may be used as a radio access technology, and an additional beamforming technology may be applied. . In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to a channel state of the terminal is applied. AMF (1a-05) performs functions such as mobility support, bearer configuration, and quality of service (QoS) configuration. The AMF is a device responsible for various control functions as well as a mobility management function for a terminal, and is connected to a plurality of base stations. In addition, the next-generation mobile communication system can be interlocked with the existing LTE system, and the AMF is connected to the MME (Mobility Management Entity, 1a-25) through a network interface. The MME is connected to the eNB (1a-30), which is an existing base station. A terminal supporting LTE-NR Dual Connectivity can transmit and receive data while maintaining connection to not only the gNB but also the eNB (1a-35).

FIG. 1B is a diagram for explaining a process in which frequency-specific priority information for cell reselection in LTE is broadcast through SIB or applied to a specific terminal through an RRC Connection Release message, which is dedicated RRC signaling. Cell reselection is a process of reselecting a serving cell so that a mobile terminal can be connected to a cell having the best channel state. The network assigns priority for each frequency to control cell reselection of terminals in the standby mode. For example, if one terminal receives priority information for two frequencies f1 and f2, and f1 has a higher priority than f2, the probability that the terminal will stay at f1 increases. Also, even if the terminal is in f2, if the channel state of f2 is not good, it will try to change to f1. Priority information for a frequency is broadcasted through SIB or provided to a specific terminal through an RRC Connection Release message, which is dedicated RRC signaling. Even if the UE already has priority information for frequencies through the SIB, if UE-specific priority information is provided through RRC signaling, the priority information of the SIB is ignored. The priority information of each frequency is transmitted through the cellReselectionPriority IE shown in Table 1 below, and one of the priorities of a total of X+1 steps is given. The lower the value, the lower the priority. That is, '0' means the lowest priority.

- ASN1START
- TAG-CELLRESELECTIONPRIORITY-START

CellReselectionPriority ::= INTEGER (0..7)

- TAG-CELLRESELECTIONPRIORITY-STOP
- ASN1STOP

Frequencies between radio access technology (RAT) cannot be given the same priority. If the IDLE state of the terminal is'camped on any cell state', frequency priority information received through SIB is applied, and priority information received through RRC signaling is not used and only stored. cellReselectionPriority IE is an optional IE and may not exist. In this case, priority information for the frequency is not assigned. In this case, the UE regards the priority of the corresponding frequency as the lowest level. In steps 1b-00, the UE receives priority information on frequencies used by other RATs as well as Evolved Universal mobile telecommunications system Terrestrial Radio Access (EUTRA) through the SIB. However, priority information for all frequencies is not necessarily provided to the terminal. Priority information on the frequency of the serving cell currently camped to the terminal may not be provided. The terminal checks whether priority information is provided in steps 1b-05. If priority information on the frequency of the current serving cell is not provided, the priority of the frequency is regarded as the lowest level. The UE applies priority information of each frequency in step 1b-15. When the terminal receives the RRC Connection Release message from the base station, the terminal switches from the connected mode to the idle mode (IDLE mode). The RRC message may include frequency priority information. This is UE-specific information, and is generally applied preferentially to the frequency priority information provided from the SIB. Accordingly, the UE checks whether there is frequency priority information in the RRC message in step 1b-20. If present, the first timer is driven in steps 1b-25 by applying the included first timer value. The terminal determines whether the current standby mode state is'camped on any cell state' or'camped normally state' in steps 1b-35. The'camped normally state' refers to a state in which the terminal is camping in a suitable cell. A suitable cell is a cell that can provide a normal service to a terminal, and is a cell that satisfies the detailed conditions as follows.

-A cell corresponds to a selected PLMN (public land mobile network), registered PLMN, or one PLMN in the equivalent PLMN list

-Cells not barring

-Cell that satisfies the Cell selection criterion

-'camped on any cell state' refers to a state in which the terminal is camping on an acceptable cell because it cannot camp on a suitable cell. In an acceptable cell, general services are not possible, and only an emergency call can be attempted by the terminal. Acceptable cell is a cell that satisfies the following conditions.

-Cells not barring

-Cell that satisfies the Cell selection criterion

If the terminal is in the'camped on any cell state' standby state, instead of the priority information provided from the RRC Connection Release message, it returns to step 1b-15 and applies the frequency priority information provided from the SIB. If the terminal is in the'camped normally' standby state, the terminal determines whether at least one of the following three conditions is satisfied in steps 1b-35. The three conditions are

-The terminal is switched to the connected mode

-The first timer has expired

-According to NAS request, PLMN selection process is performed

If any of the above conditions are satisfied, the UE discards the priority information provided from the RRC Connection Release message in step 1b-40, returns to step 1b-15, and returns the frequency priority information provided from the SIB. Apply. Otherwise, if none of the conditions are satisfied, the UE applies the priority information provided from the RRC Connection Release message in steps 1b-45.

The frequency priority information influences the UE to measure a specific frequency. For frequencies having a higher priority than the current serving cell, the UE always performs measurement. On the other hand, the same frequency as the serving cell (intra-frequency) or another frequency having the same or lower priority than that of the serving cell does not always perform measurement for the corresponding frequency in order to save terminal power. Whether to perform measurement is performed when the channel QoS of the serving cell is less than or equal to a specific threshold. Cell reselection is performed in order to move to a cell having a good channel state. Although the channel QoS of the current serving cell is good, there is no reason to move to a frequency with the same or lower priority. Therefore, in order to reduce power consumption due to unnecessary channel measurement, it is determined whether to perform measurement based on a specific threshold. In the case of the same frequency (intra-frequency), when the QoS (i.e., Srxlev or Squal) of the serving cell is the same or lower than the specific threshold Sintrasearch (s-IntraSearchP and s-IntraSearchQ), channel measurement for other cells of the same frequency Perform. s-IntraSearchP is a reference signal received power (RSRP)-based threshold, and s-IntraSearchQ is a reference signal received quality (RSRQ)-based threshold. When both the measured RSRP and RSRQ of the serving cell are greater than the threshold value, intra-frequency measurement is not performed. For other frequencies with the same or lower priority, if the QoS (i.e., Srxlev or Squal) of the serving cell is the same or lower than the specific threshold Snonintrasearch (s-NonIntraSearchP and s-NonIntraSearchQ), the corresponding other frequency Channel measurements are performed on the cells of. s-NonIntraSearchP is an RSRP-based threshold, and s-NonIntraSearchQ is an RSRQ-based threshold. When both the measured RSRP and RSRQ of the serving cell are greater than the threshold value, inter-frequency measurement is not performed. In the present invention, a state in which channel measurement is performed at an intra-frequency or inter-frequency through comparison with the threshold values is referred to as a normal measurement state, and a state otherwise is referred to as a no measurement state. Regardless of the measurement state, the serving cell measurement is always performed.

While performing this measurement, if the channel QoS of the cell having a high priority frequency is higher than a specific threshold ThreshX-high, the UE reselects the cell having a high priority frequency as the serving cell. When the channel QoS of the cell with a lower priority frequency is higher than the specific threshold ThreshX-low and the QoS of the serving cell is lower than ThreshServing-low, the UE reselects the cell with the lower priority frequency as the serving cell.

1C is a diagram illustrating a method of performing cell reselection by a UE in connection with the present disclosure.

The UE always performs inter-freq/RAT measurement for a high-priority frequency or RAT regardless of the strength of the measurement signal for the serving cell. If the measurement signal strength for the serving cell is lower than SintraSearch (1c-25), the UE performs intra-freq measurement. If the measured signal strength for the serving cell is lower than SnonintraSearch (1c-30), the UE performs inter-freq/RAT measurement for a frequency equal to or lower than the frequency of the current serving cell. The reason for triggering the UE measurement in stages is to reduce the power consumption of the UE due to the measurement of neighboring cells. When the channel QoS of the cell (1c-10) having a high priority frequency is higher than the specific threshold ThreshX-high (1c-35), the UE reselects the cell having a high priority frequency as the serving cell. When the channel QoS of the cell (1c-00) of a frequency with a low priority is higher than a specific threshold ThreshX-low (1c-15) and the QoS of the serving cell is lower than ThreshServing-low (1c-20), the UE is A cell of a frequency having a priority is reselected as a serving cell.

In cell reselection, received signal strength (RSRP) or received signal quality (RSRQ) may be considered. The received signal strength or received signal quality means a value calculated by S-criteria. That is, it is Srxlev or Squal, and each parameter is shown in Table 2.

Srxlev = Q _rxlevmeas- (Q _rxlevmin + Q _{rxlevminoffset} )-P _compensation -Qoffset _temp

Squal = Q _qualmeas- (Q _qualmin + Q _{qualminoffset} )-Qoffset _temp

Srxlev Cell selection RX level value (dB) Squal Cell selection quality value (dB) Qoffset _temp Offset temporarily applied to a cell as specified in TS 38.331 [3] (dB) Q _rxlevmeas Measured cell RX level value (RSRP) Q _qualmeas Measured cell quality value (RSRQ) Q _rxlevmin Minimum required RX level in the cell (dBm). If the UE supports SUL frequency for this cell, Qrxlevmin is obtained from q-RxLevMinSUL, if present, in SIB1, SIB2 and SIB4, additionally, if Q _{rxlevminoffsetcellSUL} is present in SIB3 and SIB4 for the concerned cell, this cell specific offset is added to the corresponding Qrxlevmin to achieve the required minimum RX level in the concerned cell;
else Qrxlevmin is obtained from q-RxLevMin in SIB1, SIB2 and SIB4, additionally, if Q _{rxlevminoffsetcell} is present in SIB3 and SIB4 for the concerned cell, this cell specific offset is added to the corresponding Qrxlevmin to achieve the required minimum RX level in the concerned cell. Q _qualmin Minimum required quality level in the cell (dB). Additionally, if Q _{qualminoffsetcell} is signaled for the concerned cell, this cell specific offset is added to achieve the required minimum quality level in the concerned cell. Q _{rxlevminoffset} Offset to the signaled Q _rxlevmin taken into account in the Srxlev evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN, as specified in TS 23.122 [9]. Q _{qualminoffset} Offset to the signaled Q _qualmin taken into account in the Squal evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN, as specified in TS 23.122 [9]. P _compensation If the UE supports the additionalPmax in the NR-NS-PmaxList, if present, in SIB1, SIB2 and SIB4:
max(P _EMAX1 -P _PowerClass , 0)-(min(P _EMAX2 , P _PowerClass )-min(P _EMX1 , P _PowerClass )) (dB);
else:
max(P _EMAX1 -P _PowerClass , 0) (dB) P _EMAX1 , P _EMAX2 Maximum TX power level of a UE may use when transmitting on the uplink in the cell (dBm) defined as P _EMAX in TS 38.101 [15]. If UE supports SUL frequency for this cell, P _EMAX1 and P _EMAX2 are obtained from the p-Max for SUL in SIB1 and NR-NS-PmaxList for SUL respectively in SIB1, SIB2 and SIB4 as specified in TS 38.331 [3], else P _EMAX1 and P _EMAX2 are obtained from the p-Max and NR-NS-PmaxList respectively in SIB1, SIB2 and SIB4 for normal UL as specified in TS 38.331 [3]. P _PowerClass Maximum RF output power of the UE (dBm) according to the UE power class as defined in TS 38.101-1 [15].

When the UE performs cell reselection at an intra-frequency or an inter-frequency having the same priority, cell-ranking criterion is used. The cell-ranking criterion is defined as shown in Table 3 below.

R _s = Q _meas,s +Q _hyst -Qoffset _temp

R _n = Q _{meas, n} -Qoffset-Qoffset _temp

Q _meas RSRP measurement quantity used in cell reselections. Qoffset For intra-frequency: Equals to Qoffset s, n, if Qoffset s, n is valid, otherwise this equals to zero.For inter-frequency: Equals to Qoffset s, n plus Qoffset frequency, if Qoffset s, n is valid, otherwise this equals to Qoffset _frequency . Qoffset _temp Offset temporarily applied to a cell as specified in TS 38.331 [3].

The UE derives a ranking value, Rs or Rn for each cell, and reselects one cell according to a predetermined rule. A method of reselecting one cell according to the predetermined rule will be described later.

The present invention proposes a method for a UE to perform cell reselection in an intra-frequency or an inter-frequency having the same priority in a licensed frequency band or an unlicensed frequency band. In addition to the mobile communication service provider that provides services to the terminal in the frequency band, other operators can use the band, so in the unlicensed frequency band, a cell belonging to a PLMN identified as RPLMN (Registered Public Land Mobile Network) or RPLMN It is characterized by considering only those.

FIG. 1D is a diagram for explaining an operation of a terminal performing cell reselection at an intra-frequency or an inter-frequency having the same priority in relation to the present disclosure.

In steps 1d-05, the terminal receives system information broadcast from the base station. The system information includes information necessary for the UE to perform an intra-/inter-/inter-RAT frequency cell reselection operation.

In step 1d-10, the terminal may obtain a rangeToBestCell parameter from SIB2 of the system information. The UE may also obtain the absThreshSS-BlocksConsolidation parameter applied to the intra-frequency in the SIB2. In addition, the UE may acquire the absThreshSS-BlocksConsolidation parameter applied to the inter-frequency from SIB4. The parameters are optional and may not be stored in the system information.

In step 1d-15, the UE determines whether the frequency considered for cell reselection is an unlicensed frequency band.

If it is a licensed frequency band in step 1d-15, the terminal determines whether the rangeToBestCell parameter is provided in step 1d-20.

If the parameter is not provided, the terminal performs a first ranking operation in step 1d-25.

If the parameter is provided, the terminal performs a second ranking operation in step 1d-30.

In steps 1d-35, when the UE performs the first or second ranking operation, the plmn-IdentityList information provided by each reselection candidate cell is not considered. That is, since it is a licensed frequency band, the terminal is in a state of recognizing which mobile communication service provider the licensed frequency band is being used by through a PLMN verification process in advance. Therefore, the terminal does not need to check this again in the ranking operation.

If it is the unlicensed frequency band in step 1d-15, the terminal determines whether the rangeToBestCell parameter is provided in step 1d-40.

If the parameter is not provided, the terminal performs a third ranking operation in steps 1d-45.

If the parameter is provided, the terminal performs a fourth ranking operation in step 1d-50.

In steps 1d-55, when performing the third or fourth ranking operation, the UE considers plmn-IdentityList information provided by each reselection candidate cell. That is, since it is an unlicensed frequency band, the terminal checks the PLMN of each cell and determines whether it is a cell of a mobile communication service provider supporting the terminal. Such PLMN information and operator information are provided by the cell through SIB1.

FIG. 1E is a diagram illustrating a UE operation for performing cell reselection in an intra-frequency or an inter-frequency having the same priority in a licensed frequency band in relation to the present disclosure.

This embodiment relates to the first and second ranking operations performed by a terminal in a licensed frequency band.

In steps 1e-05, the terminal receives system information broadcast from the base station. Cell reselection parameters are obtained from the system information. For example, nrofSS-BlocksToAverage, absThreshSS-BlocksConsolidation, rangeToBestCell, etc. belong to the above parameters.

In step 1e-10, the terminal derives signal strength quality for cells scanned at each licensed frequency or selected for implementation of the terminal. The terminal determines whether nrofSS-BlocksToAverage is not set, absThreshSS-BlocksConsolidation is not set, or the quality of the beam having the highest signal strength of the cell is equal to or lower than the value indicated by absThreshSS-BlocksConsolidation. The signal quality mentioned above means an RSRP value.

If the above-described condition is satisfied, in step 1e-15, the UE regards the quality of the beam having the highest signal strength as the signal strength quality of the corresponding cell.

If the above-described condition is not satisfied, the UE derives an average value of the number of beams indicated by the nrofSS-BlocksToAverage in linear units among beams having a signal strength greater than the value indicated by absThreshSS-BlocksConsolidation, and this is the signal of the corresponding cell. Regarded as century quality.

In step 1e-25, the terminal derives a ranking value of the cell by applying the derived signal strength quality value of the cell to the ranking derivation formula.

In step 1e-30, the terminal determines whether the rangeToBestCell is configured.

If rangeToBestCell is not set, the UE reselects the cell with the highest ranking value in steps 1e-35.

If rangeToBestCell is set, in step 1e-40, the UE has a higher signal strength than the value indicated by the absThreshSS-BlocksConsolidation among cells having a ranking value within a range as low as the value indicated by the rangeToBestCell based on the highest ranking value among cells. The cell with the largest number of beams is reselected.

FIG. 1F is a diagram for explaining an operation of a terminal performing cell reselection in an intra-frequency or an inter-frequency having the same priority in an unlicensed frequency band according to the present disclosure.

This embodiment relates to the third and fourth ranking operations performed by a terminal in an unlicensed frequency band.

In steps 1f-05, the terminal receives system information broadcast from the base station. Cell reselection parameters are obtained from the system information. For example, nrofSS-BlocksToAverage, absThreshSS-BlocksConsolidation, rangeToBestCell, etc. belong to the above parameters.

In step 1f-10, the terminal derives signal strength quality for cells scanned at each licensed frequency or selected for implementation of the terminal. The terminal determines whether nrofSS-BlocksToAverage is not set, absThreshSS-BlocksConsolidation is not set, or the quality of the beam having the highest signal strength of the cell is equal to or lower than the value indicated by absThreshSS-BlocksConsolidation. The signal quality mentioned above means an RSRP value.

If the above-described condition is satisfied, in step 1f-15, the UE regards the quality of the beam having the highest signal strength as the signal strength quality of the corresponding cell.

If the above-described condition is not satisfied, in step 1f-20, the UE derives an average value in linear units of the number of beams indicated by the nrofSS-BlocksToAverage among beams having a signal strength greater than the value indicated by absThreshSS-BlocksConsolidation, This is regarded as the signal strength quality of the cell.

In step 1f-25, the terminal derives a ranking value of the cell by applying the derived signal strength quality value of the cell to the ranking derivation formula.

In step 1f-30, the UE checks the PLMN information stored in SIB1 broadcast by each cell, and checks whether the corresponding cell belongs to the RPLMN or the PLMN identified with the RPLMN. The UE identifies a cell that provides the highest rank value among cells considered to be cells of a mobile communication service provider supporting the UE. For example, the UE determines whether a corresponding cell belongs to an RPLMN or a PLMN identified as an RPLMN in the order of cells having a higher rank value. If it is not its own operator, the UE checks the PLMN by repeating the operation for the next-order cell except for the cell. The excluded cells are not considered in this ranking operation.

In steps 1f-35, the terminal determines whether the rangeToBestCell is configured.

If rangeToBestCell is not set, the UE reselects the cell with the highest ranking value in step 1f-40. The cell belongs to the RPLMN or the PLMN identified with the RPLMN.

If rangeToBestCell is set, in steps 1f-45, the UE has a higher signal strength than the value indicated by the absThreshSS-BlocksConsolidation among cells having a ranking value within a range as low as the value indicated by the rangeToBestCell based on the highest ranking value among cells. The cell with the largest number of beams is reselected. All of the cells to be considered must belong to the RPLMN or the PLMN that is identified with the RPLMN, otherwise, they are excluded from the ranking operation.

In step 1f-50, if there are a plurality of cells having the same condition in step 1f-50, the UE reselects the cell having the highest ranking value among them.

In steps 1f-55, if all of the N cells with the best signal strength in a specific unlicensed frequency band do not belong to the RPLMN or the PLMN identified with the RPLMN, the UE assigns the cell reselection priority of the frequency to a predetermined time interval (e.g. For example, 300 seconds) is considered the lowest.

1G is a block diagram showing the internal structure of a terminal to which the present invention is applied.

Referring to the drawing, the terminal includes a radio frequency (RF) processing unit 1g-10, a baseband processing unit 1g-20, a storage unit 1g-30, and a control unit 1g-40. .

The RF processing unit 1g-10 performs a function of transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processing unit (1g-10) up-converts the baseband signal provided from the baseband processing unit (1g-20) to an RF band signal and then transmits it through an antenna, and an RF band signal received through the antenna. Is down-converted to a baseband signal. For example, the RF processing unit 1g-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), and the like. I can. In the drawing, only one antenna is shown, but the terminal may include a plurality of antennas. In addition, the RF processing unit 1g-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1g-10 may perform beamforming. For the beamforming, the RF processing unit 1g-10 may adjust a phase and a magnitude of each of signals transmitted/received through a plurality of antennas or antenna elements. In addition, the RF processor may perform MIMO, and may receive multiple layers when performing the MIMO operation.

The baseband processing unit 1g-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the system. For example, when transmitting data, the baseband processing unit 1g-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1g-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1g-10. For example, in the case of the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processor 1g-20 generates complex symbols by encoding and modulating a transmission bit stream, and subcarriers of the complex symbols After mapping to, OFDM symbols are constructed through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processing unit 1g-20 divides the baseband signal provided from the RF processing unit 1g-10 in units of OFDM symbols, and applies a fast Fourier transform (FFT) operation to subcarriers. After restoring the mapped signals, the received bit stream is restored through demodulation and decoding.

The baseband processing unit 1g-20 and the RF processing unit 1g-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1g-20 and the RF processing unit 1g-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, or a communication unit. Furthermore, at least one of the baseband processing unit 1g-20 and the RF processing unit 1g-10 may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit 1g-20 and the RF processing unit 1g-10 may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include a wireless LAN (eg, IEEE 802.11), a cellular network (eg, LTE), and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.NRHz, NRhz) band, and a millimeter wave (eg, 60GHz) band.

The storage unit 1g-30 stores data such as a basic program, an application program, and setting information for the operation of the terminal. In particular, the storage unit 1g-30 may store information related to a second access node performing wireless communication using a second wireless access technology. In addition, the storage unit 1g-30 provides stored data according to the request of the control unit 1g-40.

The control unit 1g-40 controls overall operations of the terminal. For example, the control unit 1g-40 transmits and receives signals through the baseband processing unit 1g-20 and the RF processing unit 1g-10. In addition, the control unit 1g-40 writes and reads data in the storage unit 1g-40. To this end, the control unit 1g-40 may include at least one processor. For example, the control unit 1g-40 may include a communication processor (CP) that controls communication and an application processor (AP) that controls an upper layer such as an application program. In addition, the control unit 1g-40 may further include a multiple connection processing unit 1g-42 for supporting multiple connections.

1H is a block diagram showing the configuration of a base station according to the present invention.

As shown in the figure, the base station includes an RF processing unit (1h-10), a baseband processing unit (1h-20), a backhaul communication unit (1h-30), a storage unit (1h-40), and a control unit (1h-50). Consists of including.

The RF processing unit 1h-10 performs a function of transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processing unit 1h-10 up-converts the baseband signal provided from the baseband processing unit 1h-20 to an RF band signal, and then transmits it through an antenna, and an RF band signal received through the antenna. Downconvert to a baseband signal. For example, the RF processing unit 1h-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. In the drawing, only one antenna is shown, but the first access node may include a plurality of antennas. In addition, the RF processing unit 1h-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1h-10 may perform beamforming. For the beamforming, the RF processing unit 1h-10 may adjust a phase and a magnitude of each of signals transmitted and received through a plurality of antennas or antenna elements. The RF processor may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 1h-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the first wireless access technology. For example, when transmitting data, the baseband processing unit 1h-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1h-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1h-10. For example, in the case of the OFDM scheme, when transmitting data, the baseband processor 1h-20 generates complex symbols by encoding and modulating a transmission bit stream, mapping the complex symbols to subcarriers, and then IFFT OFDM symbols are configured through calculation and CP insertion. In addition, when receiving data, the baseband processing unit 1h-20 divides the baseband signal provided from the RF processing unit 1h-10 in units of OFDM symbols, and reconstructs signals mapped to subcarriers through FFT operation. After that, the received bit stream is restored through demodulation and decoding. The baseband processing unit 1h-20 and the RF processing unit 1h-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1h-20 and the RF processing unit 1h-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, a communication unit, or a wireless communication unit.

The backhaul communication unit 1h-30 provides an interface for performing communication with other nodes in the network. That is, the backhaul communication unit 1h-30 converts a bit stream transmitted from the main station to another node, for example, an auxiliary base station, a core network, etc. Convert to heat.

The storage unit 1h-40 stores data such as a basic program, an application program, and setting information for the operation of the main station. In particular, the storage unit 1h-40 may store information on bearers allocated to the connected terminal, measurement results reported from the connected terminal, and the like. In addition, the storage unit 1h-40 may store information that is a criterion for determining whether to provide or stop providing multiple connections to the terminal. In addition, the storage unit 1h-40 provides stored data according to the request of the control unit 1h-50.

The control unit 1h-50 controls overall operations of the main station. For example, the control unit 1h-50 transmits and receives signals through the baseband processing unit 1h-20 and the RF processing unit 1h-10 or through the backhaul communication unit 1h-30. In addition, the control unit 1h-50 writes and reads data in the storage unit 1h-40. To this end, the control unit 1h-50 may include at least one processor. The control unit 1h-50 may further include a multiple connection processing unit 1h-52 for supporting multiple connections.

The embodiments disclosed in the present specification and drawings are merely provided specific examples for easy explanation and understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. Therefore, the scope of the present disclosure should be construed as including all changes or modified forms derived from the present disclosure in addition to the embodiments disclosed herein are included in the scope of the present disclosure.

Claims (1)

In a method for a terminal to perform cell selection in a wireless communication system,
Receiving system information including parameters for cell reselection from the base station;
Performing measurements on a plurality of cells on the unlicensed band;
Determining a ranking of each of the plurality of cells based on the signal strength quality values measured for the plurality of cells;
Selecting a cell corresponding to a registered public land mobile network (PLMN) from among one or more cells selected in the order of the highest ranking value and having the largest number of beams having a signal strength equal to or greater than a threshold value, based on the parameter; And
And performing reselection with the selected cell.

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