WO2017192014A2 - Method and apparatus for transmitting and receiving control information and data in frame structure of short transmission time interval - Google Patents

Abstract

The present embodiments relate to a method for transmitting and receiving control information and data between a terminal and a base station in a short TTI frame structure. In one embodiment, a search space of a legacy PDCCH and a search space of a sPDCCH are separated from each other on the basis of the type of the search space or aggregation level, etc., and information on the separated search space is signaled to the terminal, thereby enabling the terminal to detect a DCI while reducing the complexity of a blind decoding.

Description

Method and apparatus for transmitting and receiving control information and data in frame structure of short transmission time interval

The present embodiments relate to the operation of a terminal and a base station for transmitting and receiving control information and data in a 3GPP LTE / LTE-Advanced system.

Research and discussion for latency reduction in 3GPP LTE / LTE-Advanced systems are underway. The main purpose of latency reduction is to standardize shorter TTI (hereinafter referred to as 'short TTI' or 'sTTI') operation to improve TCP throughput.

To this end, RAN2 performs performance verification on short TTI, and discussions on the feasibility and performance of TTI length between 0.5ms and one OFDM symbol, and maintaining backward compatibility are ongoing.

While research on the physical layer for such a short TTI is underway and discussions on DCI configuration and detection are ongoing, search space configuration and blind decoding of sPDCCH and legacy PDCCH, short TTI based PUCCH configuration, transmission of sPUSCH and legacy SRS and There is no specific procedure for reception.

An object of the present embodiments is to provide a specific method for the search space configuration and blind decoding of the sPDCCH and legacy PDCCH in a short TTI frame structure.

In addition, an object of the present embodiment, the transmission and reception method of the uplink control channel and the uplink data channel in the short TTI-based frame structure and the specific operation of the terminal and the base station when the simultaneous transmission of the uplink data channel and sounding reference signal To provide.

In one aspect, the present invention provides a method for detecting downlink control information in a frame structure of a short transmission time interval, the method comprising: receiving a downlink control channel of a first transmission time interval set to a first aggregation level; Receiving a downlink control channel of a second transmission time interval set to a second aggregation level, and performing blind decoding based on the first aggregation level and the second aggregation level; The two aggregation levels provide a separate method from each other.

In another aspect, embodiments of the present invention provide a method for a user equipment to transmit an uplink channel in a frame structure of a short transmission time interval, the method comprising: receiving downlink data from a base station through a downlink data channel having a short transmission time interval; Transmitting an Ack / Nack for downlink data to the base station through an uplink control channel having a short transmission time interval; and uplink data and a sounding reference signal through an uplink data channel having a short transmission time interval to the base station. And transmitting at least one of uplink data and sounding reference signals through at least one of uplink data channels of short transmission time intervals included in one subframe.

In another aspect, embodiments of the present invention provide a method for a user equipment to transmit an uplink channel in a frame structure of a short transmission time interval, the method comprising: receiving downlink data from a base station through a downlink data channel having a short transmission time interval; Configuring an uplink control channel of short transmission time intervals including Ack / Nack by assigning individual cyclic shift values to Ack / Nack, and downlink data through an uplink control channel of short transmission time intervals It provides a method comprising the step of transmitting the Ack / Nack for the base station.

According to the present embodiments, a specific scheme for configuring a search space for transmitting and receiving downlink control information (DCI) in a short TTI frame structure is provided.

In addition, according to the present embodiments, a specific scheme for sPUCCH configuration and transmission and reception in a short TTI-based frame structure and an uplink channel transmission / reception scheme for solving an overlap problem between sPUSCH and SRS symbol intervals are provided.

1 is a diagram illustrating eNB and UE processing delays and HARQ RTT.

2 is a diagram illustrating resource mapping per PRB in one subframe.

3 is a conceptual diagram illustrating a search space definition.

4 is a conceptual diagram illustrating a common search space definition.

5 is a conceptual diagram illustrating UE-specific search space definition.

FIG. 6 is a diagram illustrating a conceptual search space separation scheme 1-1 for sTTI according to the present embodiments.

7 is a diagram illustrating a conceptual diagram of search space separation (Method 1-3) for sTTI according to the present embodiments.

8 is a diagram illustrating a search space based CCE indexing method according to a method 1-4-1 when separating search spaces according to the present embodiments.

9 is a diagram illustrating a search space based CCE indexing method according to a method 1-4-2 when separating search spaces according to the present embodiments.

FIG. 10 is a diagram illustrating a search space based CCE indexing method according to a method 1-4-3 when separating search spaces according to the present embodiments.

11 and 12 illustrate a process of a method for detecting DCI in an sTTI frame structure according to the embodiments.

13 is a diagram illustrating an example of an uplink channel transmission scheme in an sTTI based frame structure.

14 is a diagram illustrating a transmission conceptual diagram of sPUSCH and SRS.

15 illustrates a conceptual diagram of SRS and legacy PUSCH allocation.

16 is a conceptual diagram illustrating SRS protection through sPUSCH drop.

17 is a conceptual diagram illustrating sTTI bundling.

18 is a diagram illustrating a configuration of a base station according to the present embodiments.

19 illustrates a configuration of a user terminal according to the present embodiments.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

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

In other words, in the present specification, the MTC terminal may mean a newly defined 3GPP Release-13 low cost (or low complexity) UE category / type for performing LTE-based MTC related operations. Alternatively, in the present specification, the MTC terminal supports enhanced coverage compared to the existing LTE coverage, or supports UE category / type defined in the existing 3GPP Release-12 or lower, or newly defined Release-13 low cost (or lower power consumption). low complexity) can mean 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. The wireless communication system includes a user equipment (UE) and a base station (base station, BS, or eNB). In the present specification, a user terminal is a generic concept meaning a terminal in wireless communication. In addition, user equipment (UE) in WCDMA, LTE, and HSPA, as well as mobile station (MS) in GSM, user terminal (UT), and SS It should be interpreted as a concept that includes a 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, an Sector, a Site, and a BTS. Other terms such as a base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and a small cell may be called.

That is, in the present specification, a base station or a cell is interpreted in a comprehensive sense to indicate some areas or functions covered by a base station controller (BSC) in CDMA, a NodeB in WCDMA, an eNB or a sector (site) in LTE, and the like. It is meant to cover various coverage areas such as mega cell, macro cell, micro cell, pico cell, femto cell and relay node, RRH, RU, small cell communication range.

Since the various cells listed above have a base station for controlling each cell, the base station may be interpreted in two senses. i) the device providing the megacell, the macrocell, the microcell, the picocell, the femtocell, the small cell in relation to the wireless area, or ii) the wireless area itself. In i) all devices which provide a given wireless area are controlled by the same entity or interact with each other to cooperatively configure the wireless area to direct the base station. The eNB, RRH, antenna, RU, LPN, point, transmit / receive point, transmit point, receive point, and the like, according to the configuration of the radio region, become an embodiment of the base station. In ii), the base station may indicate the radio area itself to receive or transmit a signal from the viewpoint of the user terminal or the position of a neighboring base station.

Therefore, megacells, macrocells, microcells, picocells, femtocells, small cells, RRHs, antennas, RUs, low power nodes (LPNs), points, eNBs, transmission / reception points, transmission points, and reception points are collectively referred to as base stations. do.

In the present specification, the user terminal and the base station are two transmitting and receiving entities used to implement the technology or technical idea described in this specification in a comprehensive sense and are not limited by the terms or words specifically referred to. The user terminal and the base station are two types of uplink or downlink transmitting / receiving subjects used to implement the technology or the technical idea described in the present invention, and are used in a generic sense and are not limited by the terms or words specifically referred to. Here, the uplink (Uplink, UL, or uplink) refers to a method for transmitting and receiving data to the base station by the user terminal, the downlink (Downlink, DL, or downlink) means to transmit and receive data to the user terminal by the base station It means the way.

There is no limitation on the multiple access scheme applied to the wireless communication system. Various multiple access techniques 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-TDMA, OFDM-CDMA Can be used. One embodiment of the present invention can be applied to resource allocation in the fields of asynchronous wireless communication evolving to LTE and LTE-advanced through GSM, WCDMA, HSPA, and synchronous wireless communication evolving to CDMA, CDMA-2000 and UMB. The present invention should not be construed as being limited or limited to a specific wireless communication field, but should be construed as including all technical fields to which the spirit of the present invention can be applied.

The uplink transmission and the downlink transmission may use a time division duplex (TDD) scheme that is transmitted using different times, or may use a frequency division duplex (FDD) scheme that is transmitted using different frequencies.

In addition, in a system such as LTE and LTE-advanced, a standard is configured by configuring uplink and downlink based on one carrier or a pair of carriers. The uplink and the downlink include a Physical Downlink Control CHannel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel (PHICH), a Physical Uplink Control CHannel (PUCCH), an Enhanced Physical Downlink Control CHannel (EPDCCH), and the like. Control information is transmitted through the same control channel, and data is configured by a data channel such as a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH).

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

In the present specification, a cell means a component carrier having a coverage of a signal transmitted from a transmission / reception point or a signal transmitted from a transmission point or a transmission / reception point, and the transmission / reception point itself. Can be.

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

The multiple transmit / receive point is at least one having a high transmission power or a low transmission power in a macro cell region, which is connected to an eNB or a macro cell (hereinafter referred to as an 'eNB') and wired controlled by an optical cable or an optical fiber to an eNB. May be RRH.

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

Hereinafter, a situation in which a signal is transmitted and received through a channel such as a PUCCH, a PUSCH, a PDCCH, an EPDCCH, and a PDSCH may be described in the form of 'sending and receiving a PUCCH, a PUSCH, a PDCCH, an EPDCCH, and a PDSCH.'

In addition, hereinafter, a description of transmitting or receiving a PDCCH or transmitting or receiving a signal through the PDCCH may be used as a meaning including transmitting or receiving an EPDCCH or transmitting or receiving a signal through the EPDCCH.

That is, the physical downlink control channel described below may mean PDCCH or EPDCCH, and may also be used to include both PDCCH and EPDCCH.

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

Meanwhile, high layer signaling described below includes RRC signaling for transmitting RRC information including an RRC parameter.

The eNB performs downlink transmission to the terminals. The eNB includes downlink control information and an uplink data channel (eg, a physical downlink shared channel (PDSCH), which is a primary physical channel for unicast transmission, and scheduling required to receive the PDSCH. For example, a physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission on a physical uplink shared channel (PUSCH) may be transmitted. Hereinafter, the transmission and reception of signals through each channel will be described in the form of transmission and reception of the corresponding channel.

Latency reduction in RAN1

Latency reduction Study Items were approved at the RAN plenary # 69 meeting [1]. The main purpose of latency reduction is to standardize shorter TTI operations to improve TCP throughput [2]. To this end, RAN2 has already performed performance verification on short TTI [2].

Carry out a study of potential impacts related to RAN1 in the following ranges [1]:

O Assess specification impact and study feasibility and performance of TTI lengths between 0.5ms and one OFDM symbol, taking into account impact on reference signals and physical layer control signaling

O backwards compatibility shall be preserved (thus allowing normal operation of pre-Rel 13 UEs on the same carrier);

Latency reduction can be achieved by the following physical layer techniques:

short TTI

reduced processing time in implementation

new frame structure of TDD

Additional agreements reached at the 3GPP RAN WG1 # 84 conference are as follows:

Agreements:

● Following design assumptions are considered:

O No shortened TTI spans over subframe boundary

O At least for SIBs and paging, PDCCH and legacy PDSCH are used for scheduling

● the potential specific impacts for the followings are studied

O UE is expected to receive a sPDSCH at least for downlink unicast

■ sPDSCH refers PDSCH carrying data in a short TTI

O UE is expected to receive PDSCH for downlink unicast

■ FFS whether a UE is expected to receive both sPDSCH and PDSCH for downlink unicast simultaneously

O FFS: The number of supported short TTIs

O If the number of supported short TTIs is more than one,

Agreements:

● Following design assumptions are used for the study

O From eNB perspective, existing non-sTTI and sTTI can be FDMed in the same subframe in the same carrier

FFS: Other multiplexing method (s) with existing non-sTTI for UE supporting latency reduction features

Agreements:

In this study, following aspects are assumed in RAN1.

O PSS / SSS, PBCH, PCFICH and PRACH, Random access, SIB and Paging procedures are not modified.

● Following aspects are further studied in the next RAN1 meeting

O Note: But the study is not limited to them.

O Design of sPUSCH DM-RS

Alt.1: DM-RS symbol shared by multiple short-TTIs within the same subframe

Alt.2: DM-RS contained in each sPUSCH

O HARQ for sPUSCH

Whether / how to realize asynchronous and / or synchronous HARQ

O sTTI operation for Pcell and / or SCells by (e) CA in addition to non- (e) CA case

Additional agreements reached at the 3GPP RAN WG1 # 84bis Conference are:

Working Assumption:

-1-OFDM-symbol sTTI length will not be further studied

Agreement:

● sPDCCH (PDCCH for short TTI) needs to be introduced for short TTI.

-Each short TTI on DL may contain sPDCCH decoding candidates

Working Assumption:

● CRS-based sPDCCH is recommended to be supported

-FFS whether CRS-based sPDCCH can be transmitted in the legacy PDCCH region

● DMRS-based sPDCCH is recommended to be supported

● Design of both CRS-based sPDCCH and DMRS-based sPDCCH will be studied further.

Conclusions:

A maximum number of BDs will be defined for sPDCCH in USS

● In case 2-level DCI is adopted, any DCI for sTTI scheduling carried on PDCCH may be taken into account in the maximum total number of BDs

● FFS whether the maximum number is dependent on the sTTI length

● FFS whether the maximum number of blind decodes for (E) PDCCH is reduced in subframes in which the UE is expected to perform blind decodes for sPDCCH

● FFS whether a UE may be expected to monitor both EPDCCH and sPDCCH in the same subframe

● FFS whether the maximum number of BDs on PDCCH is changed from the legacy number

● if DCI on PDCCH is for sTTI scheduling

Conclusion for study till RAN1 # 85:

Two-level DCI can be studied for sTTI scheduling, whereby:

-DCI for sTTI scheduling can be divided into two types:

● "Slow DCI": DCI content which applies to more than 1 sTTI is carried on either legacy PDCCH, or sPDCCH transmitted not more than once per subframe

● FFS whether "Slow DCI" is UE-specific or common for multiple UEs

● "Fast DCI": DCI content which applies to a specific sTTI is carried on sPDCCH

● For a sPDSCH in a given sTTI, the scheduling information is obtained from either:

A combination of slow DCI and fast DCI, or

Fast DCI only, overriding the slow DCI for that sTTI

Compare with single-level DCI carried on one sPDCCH or one legacy PDCCH.

-It is not precluded to consider schemes in which the slow DCI also includes some resource allocation information for the sPDCCH.

Methods for reducing the overhead of single-level DCI can also be studied

-Single-level DCI multi-sTTI scheduling for a variable number of sTTIs may be included

Aim to reduce the number of schemes under consideration at RAN1 # 85.

● Both CRS based TMs and DMRS based TMs are recommended to be supported for DL sTTI transmission

No change for CRS definition

● FFS: Supporting more than 2 layers for sPDSCHs

-Further study is needed about DMRS design (s) for sPDSCH demodulation

For a certain TTI length, increased PRB bundling sizes may be necessary to achieve sufficient channel estimation accuracy.

FFS: the number of DMRS antenna ports that can be supported for a given short-TTI length.

● For a certain TTI length, new DMRS design (s) may be needed

Agreements:

A UE is expected to handle the following cases in the same carrier in a subframe

Receiving legacy TTI non-unicast PDSCH (except FFS for SC-PTM) and short TTI unicast PDSCH

Receiving legacy TTI non-unicast PDSCH (except FFS for SC-PTM) and legacy TTI unicast PDSCH (s)

● FFS between:

Alt 1: A UE is not expected to receive legacy TTI unicast PDSCH and short TTI unicast PDSCH simultaneously on one carrier

-Alt 2: If the UE is scheduled with legacy TTI unicast PDSCH and short TTI unicast PDSCH simultaneously on one carrier, then it may skip the decoding of one of them (FFS rules for determining which one)

Alt 3: A UE is expected to receive legacy TTI unicast PDSCH and short TTI unicast PDSCH simultaneously on one carrier

● FFS UE behavior in case of being scheduled with legacy TTI unicast PDSCH and short TTI unicast PDSCH simultaneously with legacy TTI non-unicast PDSCH (except FFS for SC-PTM) on the same carrier

A UE can be dynamically (with a subframe to subframe granularity) scheduled with legacy TTI unicast PDSCH and / or (depends on outcome of FFS above) short TTI PDSCH unicast

Agreements:

A UE can be dynamically (with a subframe to subframe granularity) scheduled with PUSCH and / or sPUSCH

A UE is not expected to transmit PUSCH and short TTI sPUSCH simultaneously on the same REs, i.e. by superposition

-FFS whether a UE may transmit PUSCH and short TTI sPUSCH in the same subframe on one carrier by puncturing PUSCH

-FFS whether a UE may transmit PUSCH and short TTI sPUSCH in different PRBs on the same symbol (s)

-Dropping / prioritization rules (if any) are FFS

Agreements:

● It is recommended to support PHICH-less asynchronous UL HARQ for PUSCH scheduled in a short TTI (i.e. for sPUSCH)

● If DL data transmission is scheduled in a short TTI, the processing time for preparing the HARQ feedback by UE and the processing time for preparing a potential retransmission by eNB are assumed to be reduced

FFS: the extent of processing time reduction

● If UL data transmission is scheduled in a short TTI, the processing time for preparing UL data transmission upon UL grant reception at UE and the processing time for scheduling a potential retransmission by eNB are assumed to be reduced

FFS: the extent of processing time reduction

● Study whether it is beneficial to limit the maximum TA value supported in conjunction with latency reduction

-Note that this would restrict the deployment scenarios for latency reduction.

● FFS whether processing time reductions can also be applied to legacy TTI transmissions for UEs that support short TTI

Basically, in the average down-link latency calculation, the following procedure calculates latency [3].

Following the same approach as in section B.2.1 in 3GPP TR 36.912, the LTE U-plane one-way latency for a scheduled UE consists of the fixed node processing delays and 1 TTI duration for transmission, as shown in Figure 1 below. Assuming the processing times can be scaled by the same factor of TTI reduction keeping the same number of HARQ processes, the one way latency can be calculated as

D = 1.5 TTI (eNB processing and scheduling) + 1 TTI (transmission) + 1.5 TTI (UE processing) + n * 8 TTI (HARQ retransmissions)

    = (4 + n * 8) TTI.

Considering a typical case where there would be 0 or 1 retransmission, and assuming error probability of the first transmission to be p, the delay is given by

D = (4 + p * 8) TTI.

So, for 0% BLER, D = 4 * TTI,

And for 10% BLER, D = 4.8 * TTI.

Average UE initiated UL transmission latency calculation

Assume UE is in connected / synchronized mode and wants to do UL transmission, e.g., to send TCP ACK. Following table shows the steps and their corresponding contribution to the UL transmission latency. To be consistent in comparison of DL and UL, we add the eNB processing delay in the UL after the UL data is received by the eNB (step 7).

Resource mapping of short TTI  [3]

In Figure 2 the resource map above is the legacy resource mapping per PRB in one subframe, considering 2 Antenna ports and 2 OFDM symbols control field. In Figure 2 the resource map below is the short TTI resource mapping, considering 2 OFDM symbols used for the control field in order to ensure the backward compatibility. The loss rates (L _legacy , eg 5%-50%) of the PHY layer in short TTI duration are assumed.

TBS Calculation of short TTI

According to the resource mapping and the TBS calculation formula given above, the loss rate of PHY layer for legacy PDSCH is calculated as follows:

For different short TTI duration, The TBS of short TTI PDSCH is calculated as the following table 2:

As described above, the research on the physical layer for the short TTI is in progress, and the discussion on the DCI configuration and detection is in progress. Specifically, there is no method for configuring search space and blind decoding of sPDCCH and legacy PDCCH.

The present invention proposes a search space configuration and blind decoding scheme of sPDCCH and legacy PDCCH for short TTI frame.

Basically, PDCCH detection performs blind decoding based on a given hashing function based on the following aggregation level and PDCCH candidate.

FIG. 3 is a conceptual diagram of search space definition, FIG. 4 is a conceptual diagram of common search space definition, and FIG. 5 is a conceptual diagram of UE-specific search space definition.

Search space definition and blind decoding procedure using the given hashing function are as follows.

1) Search space definition

◆ Search Space (Cont'd)

√ For the COMMON search space

√ For the UE-specific search space

◆ Size of search space

● CCE units

● size depends on the type and aggregation level of search space

● 4 kinds of size: 6, 8, 12, 16 [CCEs]

● set of PDCCH candidates to monitor are defined in terms of search spaces

Mainly connected to the aggregation level

Offset of starting-point of search space

■ Example: CommonSearchSpace

√ Size of Search space: 16 CCEs

Example: UE- specific Search Space

√ Size of Search space: 8 CCEs

As a result, the following maximum blind decoding number is determined in order for the UE to find its own PDCCH based on the defined search space.

That is, PESSCH candidates have UESS = 16 and CSS = 6 for all aggregation levels 1,2,4,8. Therefore, since there are two PDCCH formats to be found in each transmission mode, DCI format 1A + α ', the total number of blind decoding is 44 (based on legacy PDCCH).

In this proposal, a search space definition for the two-level DCI considered in the sTTI and a blind decoding operation of the UE are performed.

Two-level DCI currently considered in latency reduction can be divided into 'slow DCI' and 'fast DCI'.

An additional consideration here is blind decoding of the terminal.

In consideration of the complexity of blind decoding, an operation in which the complexity of blind decoding is divided between a legacy PDCCH and a short PDCCH (sPDCCH) is preferable. Therefore, the following method is proposed.

Option 1-1. Legacy On PDCCH  Define a search space with a relatively large aggregation level, In sPDCCH  Allocate a search space with a relatively small aggregation level. The blind decoding for the same aggregation level is not defined between the two search spaces.

In this proposal, the search space is separately defined in the legacy PDCCH region and the sPDCCH region in order to increase the maximum blind decoding to the minimum.

For example, as shown in FIG. 6, only the existing common search space and UE-specific search space with aggregation level = 4,8 are defined in the legacy PDCCH region, and the UE- with relatively low aggregation level-1,2 in the sPDCCH of each sTTI. Define only the specific search space.

This is because sTTI-based sPDCCH is expected to have relatively less available resources than legacy PDCCH, so that only aggregation level using relatively small resources is allowed for sPDCCH definition. Basically, since common search space uses aggregation level = 4,8, defining in legacy PDCCH seems to be beneficial to reduce overhead.

The separation of each search space can be applied flexibly through additional signaling during sTTI configuration. That is, if the set of aggregation level L of the UE-specific search space is lowered by signaling, the UE performs blind decoding on the aggregation level of the configured search space according to the configured method.

In detail, for example, as shown in FIG. 6, the following blind decoding is defined.

Legacy PDCCH

O Common search space: Aggregation level L = {4,8}

O UE specific search space: Aggregation level L = {4,8}

-sPDCCH: BD number = BD X No. of sTTI in a subframe

O UE specific search space: Aggregation level L = {1,2}

Option 1-2. Legacy PDCCH  Define only common search space, sPDCCH  Define only UE-specific search spaces.

In this proposal, unlike the aforementioned method 1-1, defining the common search space to the sPDCCH may be an overhead, so only the common search space is defined in the legacy PDCCH, and all other UE-specific search spaces are defined in the sPDCCH. It means to define.

That is, aggregation level L = 4,8 corresponding to common search space is defined in legacy PDCCH, and aggregation level L = 1,2,4,8 corresponding to UE-Specific search space is defined in sPDCCH.

In more detail, for example, a hashing function may be defined as in the following equation.

Legacy PDCCH

Common search space: Aggregation level L = {4,8}

-sPDCCH: BD number = BD X No. of sTTI in a subframe

o UE specific search space: Aggregation level L = {1,2,4,8}

Option 1-3. sPDCCH  Define only minimum aggregation level, remaining search space legacy On PDCCH  define.

In this proposal, only the minimum aggregation level is allocated to sPDCCH, and the remaining search space is allocated to legacy PDCCH.

For example, the lowest aggregation level among search spaces defined in the current 3GPP LTE / LTE-Advanced standard is L = 1. Therefore, in this case, since the lowest aggregation level is 1, search space allocation as shown in FIG. 7 is performed.

As a result, since this technique requires the lowest resources for the sPDCCH, the sTTI can operate in the lowest control overhead.

In detail, for example, as shown in FIG. 7, the following blind decoding is defined.

Legacy PDCCH

O Common search space: Aggregation level L = {4,8}

O UE specific search space: Aggregation level L = {2,4,8}

-sPDCCH: BD number = BD X No. of sTTI in a subframe

O UE specific search space: Aggregation level L = {1}

Option 1-4. sPDSCH  Lowest CCE index for A / N setting sTTI  Defined by applying subframe offset.

In this proposal, we propose a CCE indexing scheme based on search space separation. Although separate CCE indexes can be performed for each region, in some cases, alignment of search spaces defined in legacy PDCCH and sPDCCH may be necessary in a subframe.

Therefore, this proposal proposes CCE indexing method of three search spaces as below.

Scheme 1-4-1) legacy With PDCCH sPDCCH is  Configure a separate search space.

8 shows an example in which the legacy PDCCH and sPDCCH constitute separate search spaces.

Referring to FIG. 8, a search space of legacy PDCCH and sPDCCH is configured separately so that each CCE index is independently provided.

Scheme 1-4-2) legacy On PDCCH  next by sTTI sPDCCH  Connect to form a search space.

9 shows an example of configuring a search space by connecting sPDCCH for each sTTI to the legacy PDCCH.

Referring to FIG. 9, sPDCCH for each sTTI is connected to the legacy PDCCH to form a search space. Therefore, the CCE index of each sTTI sPDCCH is given following the CCE index of the legacy PDCCH.

Scheme 1-4-3) legacy On PDCCH by sTTI  The offsets form a contiguous search space.

10 shows an example of configuring a search space by connecting an sPDCCH with an offset for each sTTI in the legacy PDCCH.

Referring to FIG. 10, since sPDCCH is sequentially connected to legacy PDCCH to form a search space, the CCE index of sPDCCH is legacy PDCCH, sPDCCH of sTTI # 0, sPDCCH of sTTI # 1, ..., sPDCCH of sTTI # N. It is given in the order of.

In the present invention, a detailed method for configuring a search space for sTTI-based DCI transmission and reception has been described, and the method can be applied to a similar signal and channel as it is.

FIG. 11 is a flowchart illustrating a method of detecting a DCI in an sTTI frame structure according to the present embodiments, and illustrates a method of configuring a search space for a legacy PDCCH and an sPDCCH.

Referring to FIG. 11, the base station sets a search space of the legacy PDCCH (S1100) and sets a search space of the sPDCCH (S1110).

Here, the base station may be configured by separating the search space of the legacy PDCCH and sPDCCH.

For example, the base station consists of a relatively large aggregation level (eg, L = 4,8) of the search space of the legacy PDCCH, and a relatively small aggregation level (eg, L = 1,2) of the sPDCCH. The search space of legacy PDCCH and sPDCCH can be separated.

Here, the search space of the sPDCCH may be configured only with the smallest L = 1 Aggregation level, and the legacy PDCCH may be configured with the remaining Aggregation level L = 2,4,8.

Alternatively, the search space of the legacy PDCCH may be configured as a common search space, and the search space of the sPDCCH may be configured as a UE-specific search space.

The base station transmits the information on the aggregation level of the search space of the legacy PDCCH and the information on the aggregation level of the search space of the sPDCCH to the terminal (S1120), and may transmit information on the aggregation level through additional signaling at the time of sTTI configuration. .

12 illustrates a process of a method of detecting a DCI in an sTTI frame structure according to the present embodiments, and illustrates a method in which a terminal performs blind decoding.

Referring to Figure 12, the terminal receives the legacy PDCCH and sPDCCH from the base station (S1200).

In addition, the terminal receives information on the aggregation level constituting the search space of the legacy PDCCH and the sPDCCH through the sTTI configuration information (S1210).

For example, the search space of the legacy PDCCH may be configured with a relatively large aggregation level L = 4,8, and the search space of the sPDCCH may receive search space information having a relatively small aggregation level L = 1,2.

At this time, the search space of the sPDCCH may be configured only with a minimum aggregation level L = 1.

Alternatively, the search space of the legacy PDCCH may be configured at an aggregation level corresponding to the common search space, and the search space of the sPDCCH may receive search space information configured as a UE-specific search space.

The terminal checks the information on the search space received from the base station, that is, the information on the aggregation level defined in each PDCCH, and performs blind decoding on the basis of this (S1220).

By separating the search space of the legacy PDCCH and the search space of the sPDCCH and signaling information about the separated search space to the UE, the UE can perform blind decoding while reducing the complexity of blind decoding.

In addition, the present invention provides a terminal operation and a base station operation method for sPUCCH, sPUSCH (sPUSCH) and SRS transmission in a short TTI-based frame structure.

13 shows a signal transmission and reception method between a terminal and a base station in a short TTI based frame structure.

In a short TTI-based frame structure, the sTTI consists of two or three symbols. The terminal receives the sTTI-based sPDSCH through the downlink data channel from the base station.

Upon receiving the sPDSCH, the UE transmits the Ack / Nack for the received sPDSCH through the sTTI-based sPUCCH, and transmits uplink data and sounding reference signals through the sPUDSH.

Here, the terminal configures an sPUCCH for transmitting Ack / Nack through an sTTI composed of two or three symbols.

In order to transmit Ack / Nack in the existing PUCCH, resource allocation is applied by OCC (spreading) + CS (cyclic shift) based on formats 1a and 1b. However, since sPUCCH has a small number of symbols, we propose a CS-based Ack / Nack multiplexing resource allocation scheme of Zadoff-Chu (ZC) sequences excluding the existing OCC. That is, unlike the existing structure, sPUCCH is set for Ack / Nack transmission without using OCC spreading.

For example, unlike the conventional Ack / Nack method of the PUCCH, the sPUCCH may be configured such that all symbols in the sPUCCH become data symbols including the Ack / Nack message without including RS in the sPUCCH structure.

Therefore, in order to detect the sPUCCH in the eNB, unlike the conventional method of decoding the Ack / Nack message after channel estimation through RS, only On / off signaling needs to be detected.

In this case, since the on / off signaling cannot express Ack / Nack simultaneously in one symbol since there is no process of channel estimation, the terminal may express the Ack / Nack message using two or more multi-CS resources. In other words, two separate CS values are needed for the UE to express Ack or Nack, and two ACS values are allocated to each UE to configure the Ack / Nack message.

In sPUCCH, it is possible to assume that there are basically fewer terminals than the existing PUCCH, and not all terminals require latency reduction-based services, and thus sPUCCH may be configured by assigning two individual CS values to one terminal.

On the other hand, when transmitting a short TTI-based sPUSCH, the UE may generate a simultaneous transmission period with a corresponding Sounding Reference Signal (SRS). At this time, in the current low-latency related operation, the following operation is considered as an alternative in downlink.

Alt 1: A UE is not expected to receive legacy TTI unicast PDSCH and short TTI unicast PDSCH simultaneously on one carrier

-Alt 2: If the UE is scheduled with legacy TTI unicast PDSCH and short TTI unicast PDSCH simultaneously on one carrier, then it may skip the decoding of one of them (FFS rules for determining which one)

Alt 3: A UE is expected to receive legacy TTI unicast PDSCH and short TTI unicast PDSCH simultaneously on one carrier

It describes the operation of the terminal and the scheduling method of the base station for the simultaneous transmission of the SRS and sPUSCH, which is not currently covered here.

14 shows a conceptual diagram of transmission of sPUSCH and SRS, and FIG. 15 shows a conceptual diagram of SRS and legacy PUSCH allocation.

A transmission conceptual diagram illustrating the aforementioned sPUSCH and SRS transmission is illustrated in FIG. 14.

That is, the existing SRS may be allocated to the last symbol of the uplink subframe. The existing PUSCH and SRS applied the following method to solve this problem.

Basically, in a subframe in which SRS transmission is configured as shown in FIG. 15, when the legacy PUSCH is allocated, the PUSCH allocated to the region where the SRS overlaps should consider SRS and overlapping. In general, since the SRS is a signal to be protected more, the transmission priority is given, so that the PUSCH adjusts the information size through multiplexing. That is, in the PUSCH where the symbols overlap with the SRS, data transmission is performed only in the region excluding the resources of the corresponding symbol period.

However, it is difficult to apply such legacy PUSCH and SRS overlapping solution in sPUSCH.

For example, if the sTTI is defined as two symbol intervals, except for one symbol interval overlapping the SRS, only the DMRS transmission symbol interval remains, and data transmission through the sPUSCH is impossible in the corresponding sTTI.

As another example, when sTTI is defined with three OFDM symbol intervals, only two symbols except for DMRS 1 symbol may transmit sPUSCH. In this case, if the SRS symbol interval excludes one symbol interval, sPUSCH is consequently in one symbol interval. Can be transmitted.

Therefore, in some cases, the number of available data REs is insufficient, so data transmission is impossible, or only information bits having an extremely small size are transmitted, so the range is limited in taking advantage of latency reduction. Therefore, the present invention proposes the following method to solve the problem that may occur in the overlapping interval of the sPUSCH and SRS.

Option 2-1. Last in subframe sTTI  Defined sPUSCH SRS  Unconditionally overlaps with a resource sPUSCH  Transfer drop . or sPUSCH  Transfer skip .

16 shows a conceptual diagram of SRS protection through sPUSCH drop.

If the resources of the SRS transmission interval and the sPUSCH overlap, the transmission of the sPUSCH in the corresponding sTTI is omitted. In this case, it is assumed that the configuration for SRS transmission is predefined through RRC and SIB2, and the sTTI is configured in a semi-static manner. At this time, the UE does not perform the corresponding data transmission even if the sPUSCH transmission is allocated through the corresponding sTTI. In this case, the sPUSCH transmission in the sTTI may define the operation of the UE through the following method.

① Transmit again in the same sTTI of the next subframe in which SRS transmission is not performed.

■ Example: Resend on last sTTI # N (assuming SRS transmission on subframe # 0)

Subframe # 0 (sTTI # 0, sTTI # 1, ..., sTTI # N) subframe # 1 (sTTI # 0, sTTI # 1, ..., sTTI # N)

② Perform transmission again in the first sTTI of the next subframe in which SRS transmission is not performed.

■ Example: Resend on last sTTI # N (assuming SRS transmission on subframe # 0)

Subframe # 0 (sTTI # 0, sTTI # 1, ..., sTTI # N) subframe # 1 (sTTI # 0, sTTI # 1, ..., sTTI # N)

③ Delete the corresponding sPUSCH data from the buffer and wait for reassignment of sPUSCH.

Option 2-2. Last in subframe sTTI  Defined sPUSCH SRS  When overlapping with resources, sPUSCH transmission based on shortened data is performed.

When the SRS transmission interval and resources of the sPUSCH overlap, the same shortened sPUSCH in the sTTI performs transmission. This method is applied in the same way as the existing SRS and legacy PUSCH is used when overlapping. In addition, the UE also excludes the SRS overlap area when calculating the number of available REs. However, when there is too little available RE remaining in the sTTI region except for the SRS symbol period, sPUSCH transmission through the corresponding sTTI is omitted. Therefore, sPUSCH transmission is determined by considering the following criterion.

① No. of available REs> N _threshold

■ Perform sPUSCH transmission excluding SRS symbol period.

■ At this time, information size is recalculated considering available REs.

② No. of available REs ≤ N _threshold

■ Do not perform sPUSCH transmission.

Option 2-3. Last in subframe sTTI  Defined sPUSCH SRS  SPUSCH transmission is performed even if overlapped with resources.

When the SRS transmission interval and the resources of the sPUSCH overlap, the sPUSCH performs transmission regardless of the SRS configuration in the corresponding sTTI. In this case, since interference may be caused in the SRS symbol region, sPUSCH transmission is performed according to the following guide.

① When sPUSCH and SRS interval of the same UE overlap

■ The UE omits its SRS transmission and transmits by mapping the sPUSCH in the symbol interval in all sTTIs.

At this time, even though the SRS interval is set in the symbol interval, the base station can know in advance that the SRS resource and the sPUSCH interval in the frequency domain overlap, and thus does not perform the SRS detection of the corresponding region, but performs the sPUSCH detection.

② When sPUSCH and SRS intervals of different UEs overlap

SPUSCH transmission is not performed because other terminals may perform SRS transmission in the SRS configuration region.

■ If transmission is necessary due to the importance of information through the corresponding sPUSCH, transmission is performed at low power in order to minimize interference in the SRS interval.

Option 2-4. Last in subframe sTTI  Defined sPUSCH SRS  When overlapping with a resource, data transfer is performed by bundling adjacent sTTIs.

17 shows a conceptual diagram of sTTI bundling.

In the present proposal, if the sTTI overlaps the SRS symbol interval and the number of available REs of the corresponding sTTI is less than or equal to a certain number, it may not be used for data transmission. Therefore, in this case, sPUSCH transmission is basically performed by bundling with an adjacent sTTI.

At this time, since the base station knows whether the base station overlaps with the SRS symbol in advance, the terminal performs sTTI bundling according to a predetermined pattern in performing the corresponding sTTI transmission, and recalculates the available RE to perform data transmission.

For example, FIG. 17 shows an example of sTTI # 3 and # 4 bundling to transmit sPUSCH # 3. In this case, if the same UE receives consecutive sTTI assignments and each of the sTTIs includes a DMRS, the following operation may be further defined.

① The UE transmits the DMRS only in the preceding sTTI of the bundling target and performs data transmission through the sPUSCH to all the symbols except the SRS transmission symbol.

At this time, the base station knows the sTTI bundling-based transmission of the terminal in advance and performs sPUSCH detection using only the DMRS of the preceding sTTI.

② The UE transmits the DMRS in all sTTIs to be bundled and performs data transmission through the sPUSCH to all the symbols except the SRS transmission symbol.

At this time, the base station knows the bundled sTTI bundling-based transmission of the UE in advance and performs sPUSCH detection using all the DMRSs located in each of the sTTIs.

Option 2-5. sTTI  at configuration SRS  Transmission takes place subframe  Defines sTTIs except the last symbol.

In this proposal, when the sTTI is defined in a semi-static manner, if the SRS configuration is configured in the corresponding subframe, the sTTI is defined without any SRS symbol interval. In this case, since the SRS overlap issue is removed during sTTI configuration, this SRS overlap problem can be solved.

In the present invention, a specific method for solving the overlap problem between the sTTI-based sPUSCH and the SRS symbol interval has been described, and the method can be applied to a similar signal and channel as it is.

18 illustrates a configuration of a base station 1800 according to the present embodiments.

Referring to FIG. 18, the base station 1800 according to the present exemplary embodiments includes a controller 1810, a transmitter 1820, and a receiver 1830.

The controller 1810 controls the overall operation of the base station 1800 according to the above-described embodiments of the present invention by providing a search space configuration and a blind decoding scheme of the sPDCCH and the legacy PDCCH for the short TTI frame.

In addition, the controller 1810 controls the overall operation of the base station 1800 according to the sPUCCH setting and transmission, sPUSCH and SRS transmission according to the above-described embodiments.

The transmitter 1820 and the receiver 1830 are used to transmit and receive signals, messages, and data necessary for carrying out the present invention.

19 illustrates a configuration of a user terminal 1900 according to the present embodiments.

Referring to FIG. 19, the user terminal 1900 according to the present embodiment includes a receiver 1910, a controller 1920, and a transmitter 1930.

The receiver 1910 receives downlink control information, data, and a message from a base station through a corresponding channel.

The controller 1920 controls the overall operation of the user terminal 1900 according to the above-described embodiments of the present invention by providing a search space configuration and a blind decoding scheme of the sPDCCH and the legacy PDCCH for the short TTI frame.

In addition, the controller 1920 controls the overall operation of the user terminal 1900 according to the sPUSCH setting and transmission, sPUSCH and SRS transmission according to the above-described embodiments.

The transmitter 1930 transmits uplink control information, data, and a message to a base station through a corresponding channel.

The standard contents or standard documents mentioned in the above embodiments are omitted to simplify the description of the specification and form a part of the present specification. Therefore, the addition of the contents of the standard and part of the standard documents to the specification or the description in the claims should be construed as falling within the scope of the present invention.

Appendix

[1] Ericsson, Huawei, "New SI proposal Study on Latency reduction techniques for LTE", RP-150465, Shanghai, China, March 9-12, 2015.

[2] R2-155008, "TR 36.881 v0.4.0 on Study on Latency reduction techniques for LTE", Ericsson (Rapporteur)

[3] R1-160927, "TR 36.881-v0.5.0 on Study on Latency reduction techniques for LTE", Ericsson (Rapporteur)

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is filed with Korea Patent Application No. 10-2016-0055676 filed in Korea on May 04, 2016 and Patent Application No. 10-2016-0058317 filed in Korea on May 12, 2016 and May 2017. 119 (a) (35 USC §) of the United States Patent Act No. 10-2017-0056011 filed in Korea on February 02 and Patent Application No. 10-2017-0056206 filed in Korea on May 02, 2017 Priority is claimed under 119 (a)), the contents of which are hereby incorporated by reference in their entirety. In addition, if this patent application claims priority for the same reason for countries other than the United States, all its contents are incorporated into this patent application by reference.

Claims (17)

In the method for detecting downlink control information in a frame structure of a short transmission time interval, Receiving a downlink control channel of a first transmission time interval set to a first aggregation level; Receiving a downlink control channel of a second transmission time interval set to a second aggregation level; And Performing blind decoding based on the first aggregation level and the second aggregation level, And the first aggregation level and the second aggregation level are separated from each other. The method of claim 1, Wherein the first aggregation level is an aggregation level that is greater than or equal to a preset aggregation level, and wherein the second aggregation level is an aggregation level that is less than the preset aggregation level. The method of claim 1, Wherein the first aggregation level is an aggregation level corresponding to a common search space, and the second aggregation level is an aggregation level corresponding to a terminal specific search space. The method of claim 1, Wherein the first aggregation level is an aggregation level corresponding to a terminal specific search space and the second aggregation level is an aggregation level corresponding to a terminal specific search space. The method of claim 1, And the second aggregation level is the smallest aggregation level, and the first aggregation level is the remaining aggregation level except the second aggregation level. The method of claim 1, And receiving information on the search space of the downlink control channel of the first transmission time interval and the search space of the downlink control channel of the second transmission time interval through transmission time interval setting information. The method of claim 1, And separately configuring a search space of the downlink control channel of the first transmission time interval and a search space of the downlink control channel of the second transmission time interval. The method of claim 1, And configuring a search space by connecting one of a search space of a downlink control channel of the first transmission time interval and a search space of a downlink control channel of the second transmission time interval. The method of claim 1, And configuring a search space by sequentially connecting the search space of the downlink control channel of the second transmission time interval to the search space of the downlink control channel of the first transmission time interval. In the method for the terminal to transmit the uplink channel in a frame structure of a short transmission time interval, Receiving downlink data through a downlink data channel of a short transmission time interval from a base station; Transmitting an Ack / Nack for the downlink data to the base station through an uplink control channel having a short transmission time interval; And Transmitting uplink data and a sounding reference signal through the uplink data channel of a short transmission time interval to the base station; And transmitting at least one of the uplink data and the sounding reference signal through at least one of the uplink data channels of the short transmission time interval included in one subframe. The method of claim 10, And dropping any one of the uplink data and the sounding reference signal when the uplink data and the sounding reference signal overlap the same symbol of the uplink data channel of the short transmission time interval. The method of claim 10, When the uplink data and the sounding reference signal overlap the same symbol of the uplink data channel of the short transmission time interval, the uplink data is transmitted through a resource element in which the sounding reference signal is not transmitted in the same symbol. How to. The method of claim 10, If the uplink data and the sounding reference signal overlap the same symbol of the uplink data channel of the short transmission time interval, bundle the uplink data channel of the adjacent short transmission time interval to transmit the uplink data. The method of claim 10, A method of configuring an uplink data channel of the short transmission time interval using symbols other than a symbol for transmitting the sounding reference signal in one subframe. In the method for the terminal to transmit the uplink channel in a frame structure of a short transmission time interval, Receiving downlink data through a downlink data channel of a short transmission time interval from a base station; Configuring an uplink control channel of a short transmission time interval including Ack / Nack in a manner of assigning respective cyclic shift values to Ack / Nack; And And transmitting the Ack / Nack for the downlink data to the base station through the uplink control channel of the short transmission time interval. The method of claim 15, And the cyclic shift values respectively assigned to the Ack / Nack have different values from each other. The method of claim 15, And transmitting the Ack / Nack through all symbols included in the uplink control channel of the short transmission time interval.

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