KR20180112217A - Apparatus and method of radio link management in new radio - Google Patents

Abstract

The present invention provides a method for managing a radio link for a next generation/5G wireless access network (new radio, NR). More specifically, the present invention provides a method for operating a specific radio link and an HARQ with respect to a situation in which an enhancement mobile broadband (eMBB) terminal is multiplexed with ultra reliable and low latency communications (URLLC) terminals. The method for managing a radio link for a next generation wireless network comprises the following steps of: puncturing a part of a data channel for a first terminal to allocate to a data channel for a second terminal; the first terminal failing to detect data; and the first terminal holding a radio link failure (RLF) declaration, and performing a retransmission operation.

Description

[0001] The present invention relates to a radio link management method and apparatus for a next-generation radio network,

The present embodiments propose a radio link management method for a next generation / 5G radio access network (hereinafter referred to as "NR [New Radio]").

In one embodiment, a radio link management method for a next generation wireless network includes puncturing a portion of a data channel for a first terminal to allocate the data channel as a data channel for the second terminal, And the first terminal holds the RLF declaration and performs a retransmission operation.

FIG. 1 shows an example of symbol level alignment among different SCS.
Figure 2 shows the concept of LTE BRP Tx. Architecture (refer to TS 36.212).
Figure 3 shows an example of eMBB and URLLC multiplexing.
FIG. 4 illustrates an RRC connection reestablishment procedure performed by a UE when an RLF occurs.
Fig. 5 shows an example of CBG and CB definition in TB.
Figure 6 shows an example of repetition-based CBG retransmission.
7 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.
FIG. 8 is a diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Herein, the MTC terminal may mean a terminal supporting low cost (or low complexity) or a terminal supporting coverage enhancement. In this specification, the MTC terminal may mean a terminal supporting low cost (or low complexity) and coverage enhancement. Alternatively, the MTC terminal may refer to a terminal defined in a specific category for supporting low cost (or low complexity) and / or coverage enhancement.

In other words, the MTC terminal in this specification may mean a newly defined 3GPP Release-13 low cost (or low complexity) UE category / type for performing LTE-based MTC-related operations. Alternatively, the MTC terminal may support enhanced coverage over the existing LTE coverage or a UE category / type defined in the existing 3GPP Release-12 or lower that supports low power consumption, or a newly defined Release-13 low cost low complexity UE category / type.

The wireless communication system in the present invention is widely deployed to provide various communication services such as voice, packet data and the like. A wireless communication system includes a user equipment (UE) and a base station (BS, or eNB). The user terminal in this specification is a comprehensive concept of a terminal in wireless communication. It is a comprehensive concept which means a mobile station (MS), a user terminal (UT), an SS (User Equipment) (Subscriber Station), a wireless device, and the like.

A base station or a cell generally refers to a station that communicates with a user terminal and includes a Node-B, an evolved Node-B (eNB), a sector, a Site, a BTS A base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and a small cell.

That is, the base station or the cell in this specification is interpreted as a comprehensive meaning indicating a partial region or function covered by BSC (Base Station Controller) in CDMA, NodeB in WCDMA, eNB in LTE or sector (site) And covers various coverage areas such as megacell, macrocell, microcell, picocell, femtocell and relay node, RRH, RU, and small cell communication range.

Since the various cells listed above exist in the base station controlling each cell, the base station can be interpreted into two meanings. i) the device itself providing a megacell, macrocell, microcell, picocell, femtocell, small cell in relation to the wireless region, or ii) indicating the wireless region itself. i indicate to the base station all devices that are controlled by the same entity or that interact to configure the wireless region as a collaboration. An eNB, an RRH, an antenna, an RU, an LPN, a point, a transmission / reception point, a transmission point, a reception point, and the like are exemplary embodiments of a base station according to a configuration method of a radio area. ii) may indicate to the base station the wireless region itself that is to receive or transmit signals from the perspective of the user terminal or from a neighboring base station.

Therefore, a base station is collectively referred to as a base station, collectively referred to as a megacell, macrocell, microcell, picocell, femtocell, small cell, RRH, antenna, RU, low power node do.

Herein, the user terminal and the base station are used in a broad sense as the two transmitting and receiving subjects used to implement the technical or technical idea described in this specification, and are not limited by a specific term or word. The user terminal and the base station are used in a broad sense as two (uplink or downlink) transmitting and receiving subjects used to implement the technology or technical idea described in the present invention, and are not limited by a specific term or word. Here, an uplink (UL, or uplink) means a method of transmitting / receiving data to / from a base station by a user terminal, and a downlink (DL or downlink) .

There are no restrictions on multiple access schemes applied to wireless communication systems. Various multiple access schemes such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), OFDM-FDMA, OFDM- Can be used. An embodiment of the present invention can be applied to asynchronous wireless communication that evolves into LTE and LTE-advanced via GSM, WCDMA, and HSPA, and synchronous wireless communication that evolves into CDMA, CDMA-2000, and UMB. The present invention should not be construed as limited to or limited to a specific wireless communication field and should be construed as including all technical fields to which the idea of the present invention can be applied.

A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

In systems such as LTE and LTE-advanced, a standard is constructed by configuring uplink and downlink based on a single carrier or carrier pair. The uplink and the downlink are divided into a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel, a Physical Uplink Control CHannel (PUCCH), an Enhanced Physical Downlink Control Channel (EPDCCH) Transmits control information through the same control channel, and is configured with data channels such as PDSCH (Physical Downlink Shared CHannel) and PUSCH (Physical Uplink Shared CHannel), and transmits data.

On the other hand, control information can also be transmitted using EPDCCH (enhanced PDCCH or extended PDCCH).

In this specification, a cell refers to a component carrier having a coverage of a signal transmitted from a transmission point or a transmission point or transmission / reception point of a signal transmitted from a transmission / reception point, and a transmission / reception point itself .

The wireless communication system to which the embodiments are applied may be a coordinated multi-point transmission / reception system (CoMP system) or a coordinated multi-point transmission / reception system in which two or more transmission / reception points cooperatively transmit signals. antenna transmission system, or a cooperative multi-cell communication system. A CoMP system may include at least two multipoint transmit and receive points and terminals.

The multi-point transmission / reception point includes a base station or a macro cell (hereinafter referred to as 'eNB'), and at least one mobile station having a high transmission power or a low transmission power in a macro cell area, Lt; / RTI >

Hereinafter, a downlink refers to a communication or communication path from a multipoint transmission / reception point to a terminal, and an uplink refers to a communication or communication path from a terminal to a multiple transmission / reception point. In the downlink, a transmitter may be a part of a multipoint transmission / reception point, and a receiver may be a part of a terminal. In the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of multiple transmission / reception points.

Hereinafter, a situation in which a signal is transmitted / received through a channel such as PUCCH, PUSCH, PDCCH, EPDCCH, and PDSCH is expressed as 'PUCCH, PUSCH, PDCCH, EPDCCH and PDSCH are transmitted and received'.

In the following description, an indication that a PDCCH is transmitted or received or a signal is transmitted or received via a PDCCH may be used to mean transmitting or receiving an EPDCCH or transmitting or receiving a signal through an EPDCCH.

That is, the physical downlink control channel described below may mean a PDCCH, an EPDCCH, or a PDCCH and an EPDCCH.

Also, for convenience of description, the PDCCH, which is an embodiment of the present invention, may be applied to the PDCCH, and the PDCCH may be applied to the portion described with the EPDCCH.

Meanwhile, the High Layer Signaling described below includes RRC signaling for transmitting RRC information including RRC parameters.

The eNB performs downlink transmission to the UEs. The eNB includes a physical downlink shared channel (PDSCH) as a main physical channel for unicast transmission, downlink control information such as scheduling required for reception of a PDSCH, A physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission in a Physical Uplink Shared Channel (PUSCH). Hereinafter, the transmission / reception of a signal through each channel will be described in a form in which the corresponding channel is transmitted / received.

[5G NR (New Rat)]

3GPP recently approved the study item "Study on New Radio Access Technology" for research on next generation / 5G radio access technology, and based on this, RAN WG1 has frame structure, channel coding and modulation , waveform & multiple access scheme and so on. NR is required not only to improve data transmission rate as compared with LTE, but also to design various QoS requirements that are required according to granular and specific usage scenarios. In particular, enhancement mobile broadband (eMBB), massive MTC (MMTC) and URLLC (Ultra Reliable and Low Latency Communications) are defined as typical usage scenarios of NR. structure design is required. Since each usage scenario has different requirements for data rates, latency, reliability, coverage, etc., it is a method to efficiently satisfy the requirements of each usage scenario through frequency bands constituting an NR system. there is a need for an efficient multiplexing of radio resource units based on subcarrier spacing, subframe, TTI, etc., for example.

One method is to support TDM, FDM or TDM / FDM based multiplexing on one or more NR component carriers (s) for numerology with different subcarrier spacing values, and a scheduling unit in the time domain A discussion was made on how to support more than one time unit in composition. In this regard, NR is a type of time domain structure defined as a subframe. Reference numerology for defining the subframe duration is defined as 14 OFDM symbols of 15 kHz sub-carrier spacing (SCS) based normal CP overhead equivalent to LTE To define a single subframe duration. Thus, subframes in NR have a time duration of 1ms. However, unlike LTE, NR subframes are absolute reference time durations, and slots and mini-slots can be defined as time units that are the basis of actual uplink and downlink data scheduling. In this case, the number of OFDM symbols constituting the slot, y value is defined as y = 7 and 14 for the numerology having the SCS value of up to 60 kHz, and for the numerology having the SCS value larger than 60 kHz, y = Lt; / RTI >

Accordingly, any slot can be composed of 7 or 14 symbols, and all symbols are used for DL transmission according to the transmission direction of the corresponding slot, or all symbols are used for UL transmission, or the DL portion + (gap) + UL portion.

Also, a mini-slot composed of a smaller number of symbols than a corresponding slot is defined in an arbitrary numerology (or SCS), and a short-time time-domain scheduling interval is set for uplink / downlink data transmission or reception, A long-time time-domain scheduling interval for uplink / downlink data transmission and reception can be configured. In particular, in the case of transmission and reception of latency critical data such as URLLC, scheduling is performed in units of 0.5 ms (7 symbols) or 1 ms (14 symbols) based on a numerology-based frame structure having a small SCS value, such as 15 kHz , it is difficult to satisfy the latency requirement. Therefore, it is possible to define a mini-slot composed of a smaller number of OFDM symbols than the corresponding slot and to schedule the latency critical data such as the URLLC based on the defined mini-slot.

Alternatively, as described above, by supporting the numerology having different SCS values in one NR Carrier by multiplexing the TDM and / or FDM scheme, it is possible to reduce the number of slots based on the slot (or mini-slot) length defined for each numerology Scheduling of data according to latency requirement is also considered. For example, as shown in FIG. 1, when the SCS is 60 kHz, the symbol length is reduced to about 1/4 of that of the SCS 15 kHz. Therefore, when one slot is composed of 7 OFDM symbols, While the slot length based on 60 kHz is reduced to about 0.125 ms.

In this way, the NR is discussing how to satisfy the requirements of URLLC and eMBB by defining different SCSs or different TTI lengths.

[ NR PDSCH / PUSCH  TB, CB, CBG  Configuration]

In the case of the existing LTE system, when the data channel is allocated (PDSCH / PUSCH), the processing is performed in TB units as a whole. That is, the best gNB determines the TB size considering the channel state (CQI) of the UE.

For the next determined TB, segmentation takes place considering the maximum input size of the encoder. In case of LTE, the maximum input size for the data channel is configured as shown in FIG. 2 at 6144 bits. Therefore, TB is divided into several CBs considering this CB size.

: Number of Input bits or the size of transport block

: Number of Input bits or the size of transport block

: The size of entire transport block (B = A+L)

: The size of the entire transport block (B = A + L)

: CRC length (e.g. in DL-SCH, CRC-length is 24)

: CRC length (eg, in-DL-SCH, CRC-length is 24)

: The maximum code block size (Zmax = 6144)

: The maximum code block size (Zmax = 6144)

In addition, retransmission also causes all of the CBs to retransmit the entire TB if a nack occurs. However, at present, NR is currently under discussion as follows.

At the 3GPP RAN1 # 88 meeting, the following matters related to the code block were determined.

Working assumption:

* CBG-based transmission with single / multi-bit HARQ-ACK feedback is supported in Rel-15, which shall have the following characteristics:

o Only allow CBG based (re) -transmission for the same TB of a HARQ process

In this case, the UE reports a single HARQ ACK bits for the TB

o CBG can include one CB

o CBG granularity is configurable

That is, the entire procedure design is considered to enable not only HARQ ack / nack transmission in TB units but also A / N transmission in a specific code block group unit. In this way, it can be predicted that, when an error occurs in some CBs of the TB, retransmission can be performed except for a portion in which no error occurs. In other words, it can be seen that efficiency can be increased by eliminating the redundancy of retransmission.

The present invention proposes a radio link management and HARQ operation method of an eMBB terminal considering a URLLC service in NR.

In the present invention, a radion link management method of an eMBB terminal considering a URLLC service in NR is proposed. As shown in FIG. 3, the URLLC and the eMBB can be multiplexed on the same resource, and details of the URLLC and the eMBB are currently being discussed.

In the situation where such eMBB and URLLC data are multiplexed, a concrete method of applying pre-emption to URLLC is basically under discussion. Basically, it punctures the eMBB data of the area overlapped with the URLLC data and transmits the puncturing indication information to the eMBB terminal. At this time, since the error probability increases in the PDSCH of the eMBB terminal, retransmission may occur frequently. This is because the probability of frequent inconsistency of the channel status information is increased.

- CSI estimation of eMBB terminal: feedback to gNB after deriving CSI using channel estimation reference signal such as CSI-RS

- Issue point: Data loss due to URLLC (eg puncturing loss) is not reflected in CSI derivation through reference signal like CSI-RS.

Therefore, eMBB terminals may experience a surge in retransmission or data transmission failure due to too many URLLC puncturing losses. In this case, a radio link failure may occur between the terminal and the base station extremely. Therefore, the channel status of the actual eMBB terminal newly defines the terminal operation for the situation in which the CQI loss due to the URLLC is continuously generated although the RLF is not generated.

Basically, the environment in which a radio link failure (RLF) occurs can be summarized into the following three cases. Since actual operation is an implementation issue, accurate prediction is impossible.

* The measured RSRP is too low (under a certain limit)

* It failed to decode PDCCH due to power signal quality (eg, low RSRP, RSRQ)

* It failed to decode PDSCH due to power signal quality (eg, low RSRP, RSRQ)

Here, it can be seen that the failure of continuous detection of the PDSCH can occur as a cause of the RLF.

Method 1. The base station With URLLC  Multiplex eMBB  Even if the terminal continuously fails to detect data, By RLF  Do not declare.

In this proposal, as described above, the eMBB terminal defines the terminal operation in a situation in which PDSCH data detection fails continuously by URLLC puncturing loss. Generally, when an RLF occurs, the UE generally performs an RRC connection reestablishment procedure. That is, it is assumed that the state of the UE and the BS is out of sync, and the synchronization acquisition procedure using the PRACH is performed again. The operation below is shown in Fig. However, in this proposal, the exception operation of the terminal is given so that the RLF does not occur. That is, when the gNB occurs in an environment where the PDSCH detection failure of the current eMBB UE is multiplexed with the URLLC, the gNB may temporarily hold the RLF declaration and perform a persistent retransmission operation to the UE. This makes it unnecessary to perform an RLF recovery procedure unnecessary for the UE.

2. The base station With URLLC  Multiplex eMBB  Even when the terminal continuously performs retransmission, By RLF  Do not declare.

In this proposal, it means that the eMBB terminal defines the terminal operation in a situation in which PDSCH data detection fails continuously by URLLC puncturing loss as in the above-mentioned 'Method 1'. That is, even if the retransmission continues, the CQI estimated and fed back from the actual UE is different from the CQI currently experienced by the UE. This is not a problem to be solved by shortening the CQI feedback period, but can be solved by reflecting the CQI loss that the eMBB terminal currently receives from the URLLC.

Therefore, as proposed in the proposal, the BS keeps the current procedure even if the UE continuously generates the retransmission due to the CQI mismatch.

3. The base station With URLLC  Multiplex eMBB  When the UE continuously performs retransmission, the corresponding code-block group ( CBG ) Only flexible  Retransmission.

In this proposal, we propose a HARQ procedure operation method in URLLC multiplexing transmission situation of eMBB terminal. Basically, the eMBB terminal can receive the puncturing indication information that indicates the location of the URLLC resource in the PDSCH which is its data transmission area. TB can also be divided into several code-blocks (CBs). Currently, there is a debate about defining these CBs as CB-groups (CBGs). The UE can transmit Ack / Nack information in CBG units, and CBG can be composed of a single CB and N CBs.

The proposal here suggests a new HARQ operation when retransmission is performed in an environment in which an eMBB UE is overlapped with a URLLC.

Specifically, as shown in FIG. 5, it is assumed that TB is divided into a total of 8 CBs, and CBG is composed of 2 CBs.

In the proposed method, to increase the detection accuracy of the continuous retransmission situation, only the CBGs to which the error-detected CB belongs are retransmitted, but the size of the CBGs can be larger than the corresponding CBG size. For example, when only the CBG # 0 is retransmitted, the CBG # 0 is repeatedly transmitted to the empty CBG # 1, 2, and 3 space as shown in FIG. 6 when the resource allocation size of the TB # 0 is maintained and retransmitted . This is because CBG # 1-3 was transmitted without errors in the previous transmission. That is, it can be seen that the size of the CBG to be retransmitted can be flexible.

Therefore, flexible CBG retransmission can have the following flexible range.

1. Retransmitting only the corresponding CBG : Only the CBG to be retransmitted is allocated within the subframe or within the TTI and retransmitted.

2. Repetitive transmission based retransmission : The retransmission CBG is repeatedly transmitted within a subframe or within a TTI by a certain number 'K'. Here, the number of CBG repetitions K in a subframe can be set through RRC signaling or can be set by dynamic signaling by adding a specific field to the DL / UL grant.

3. Retransmission based on retention of TB size : When the error CBG is retransmitted, the retransmission size is the same as the existing TB number, and the CBGs are allocated in the subframe or in the TTI in a repetitive manner according to the space. For example, when the TB is divided into four CBGs, the number of repetitions is determined according to the number of CBGs in which the error occurs.

- Total number of CBG = 4, Error CBG = 1: Repeat 4 times in the corresponding CBG subframe

- Total number of CBG = 4, Error CBG = 2: Repeat 2 times in the corresponding CBG subframe

- Total number of CBG = 4, Error CBG = 3: One transmission in the corresponding CBG subframe

7 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.

Referring to FIG. 7, a base station 1000 according to another embodiment includes a control unit 1010, a transmission unit 1020, and a reception unit 1030.

The controller 1010 controls the overall operation of the base station 1000 according to the above-described method of performing a radio link management method for a next-generation radio network according to the present invention.

The transmitting unit 1020 and the receiving unit 1030 are used to transmit and receive signals, messages, and data necessary for carrying out the present invention to and from the terminal.

FIG. 8 is a diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

Referring to FIG. 8, a user terminal 1100 according to another embodiment includes a receiving unit 1110, a control unit 1120, and a transmitting unit 1130.

The receiving unit 1110 receives downlink control information, data, and messages from the base station through the corresponding channel.

The controller 1120 controls the overall operation of the user terminal 1100 according to the above-described method of performing the radio link management method for the next generation radio network.

The transmitter 1130 transmits uplink control information, data, and a message to the base station through the corresponding channel.

The standard content or standard documents referred to in the above-mentioned embodiments constitute a part of this specification, for the sake of simplicity of description of the specification. Therefore, it is to be understood that the content of the above standard content and portions of the standard documents are added to or contained in the scope of the present invention.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (1)

A radio link management method for a next generation wireless network,
Puncturing a part of the data channel for the first terminal and allocating the data channel as a data channel for the second terminal;
The first terminal failing to detect data; And
Wherein the first terminal holds the RLF declaration and performs a retransmission operation.

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