KR102093906B1 - Method and apparatus for detecting downlink control information in a short tti frame structure - Google Patents

Abstract

The present embodiments are directed to a method for a UE to detect DCI in a short TTI frame structure, and separate search spaces of legacy PDCCH and search space of sPDCCH from each other based on the type or aggregation level of search space and separate search spaces. Signaling the information to the terminal enables the terminal to detect DCI while reducing the complexity of blind decoding.

Description

Method and apparatus for detecting downlink control information in a frame structure with a short transmission time interval {METHOD AND APPARATUS FOR DETECTING DOWNLINK CONTROL INFORMATION IN A SHORT TTI FRAME STRUCTURE}

The present embodiments relate to operations of a terminal and a base station that detect downlink control information 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 the operation of shorter TTI (hereinafter referred to as 'short TTI' or 'sTTI') to improve TCP throughput.

To this end, RAN2 performs performance verification for 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.

A study on the physical layer for such a short TTI is ongoing, and discussions regarding DCI configuration and detection are in progress, but there are no methods for search space configuration and blind decoding of sPDCCH and legacy PDCCH.

The purpose of the present embodiments is to provide a concrete scheme for search space configuration and blind decoding of sPDCCH and legacy PDCCH in a short TTI frame structure.

In one aspect, the present embodiments, in a method for detecting downlink control information in a frame structure with a short transmission time interval, setting a search space of a downlink control channel in a first transmission time interval to a first aggregation level And setting a search space of a downlink control channel at a second transmission time interval to a second aggregation level, and the first aggregation level and the second aggregation level provide a method separated from each other.

In another aspect, the present embodiments provide a method for detecting downlink control information in a frame structure having a short transmission time interval, the method comprising: receiving a downlink control channel at a first transmission time interval set to a first aggregation level; And receiving a downlink control channel at 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 addition, the present embodiments, in the terminal for detecting the downlink control information in the frame structure of a short transmission time interval, receives the downlink control channel of the first transmission time interval set to the first aggregation level and the second aggregation level And a control unit for performing blind decoding based on the first set level and the second set level, and the first set level and the second set level are each other. Provide a separate terminal.

According to the present embodiments, a specific method for constructing a search space for transmitting and receiving downlink control information (DCI) in a short TTI frame structure is provided, and the principles of the present embodiments can be applied to similar signals and channels.

1 is a diagram showing eNB and UE processing delays and HARQ RTT.
2 is a view showing a resource mapping per PRB in one subframe.
3 is a diagram illustrating a conceptual diagram of search space definition.
4 is a diagram illustrating a conceptual diagram of defining a common search space.
5 is a diagram illustrating a conceptual diagram of UE-specific search space definition.
6 is a diagram illustrating a conceptual diagram (Scheme 1) of search space separation for sTTI according to the present embodiments.
7 is a diagram illustrating a conceptual diagram (Scheme 3) of search space separation for sTTI according to the present embodiments.
8 is a diagram illustrating a search space based CCE indexing method according to method 4-1 when separating a search space according to the present embodiments.
9 is a diagram illustrating a search space based CCE indexing method according to method 4-2 when separating a search space according to the present embodiments.
10 is a diagram illustrating a search space based CCE indexing method according to method 4-3 when separating a search space according to the present embodiments.
11 and 12 are diagrams illustrating a process of a method for detecting DCI in the sTTI frame structure according to the present embodiments.
13 is a diagram showing the configuration of a base station according to the present embodiments.
14 is a diagram showing the 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. It should be noted that in adding reference numerals to the components of each drawing, the same components have the same reference numerals as possible even though they are displayed on different drawings. In addition, in describing the present invention, when it is determined that detailed descriptions of related well-known configurations or functions may obscure the subject matter of the present invention, detailed descriptions thereof will be omitted.

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

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

The wireless communication system in the present invention is widely deployed to provide various communication services such as voice and packet data. The wireless communication system includes a user equipment (User Equipment, UE) and a base station (Base Station, BS, or eNB). The user terminal in the present specification is a comprehensive concept meaning a terminal in wireless communication, as well as UE (User Equipment) in WCDMA and LTE, HSPA, MS (Mobile Station) in GSM, UT (User Terminal), SS It should be interpreted as a concept including (Subscriber Station) and wireless devices.

Base station or cell (cell) generally refers to a station (station) to communicate with the user terminal, Node-B (Node-B), eNB (evolved Node-B), sector (Sector), site (Site), BTS ( Base Transceiver System), an access point (Access Point), a relay node (Relay Node), RRH (Remote Radio Head), RU (Radio Unit), can be called in other terms such as small cells.

That is, in this specification, a base station or cell is interpreted in a comprehensive sense indicating some areas or functions covered by a base station controller (BSC) in CDMA, a NodeB in WCDMA, an eNB or sector (site) in LTE, and the like. This means that it covers all of the 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 have a base station that controls each cell, the base station can be interpreted in two ways. It may be i) a device providing a megacell, a macrocell, a microcell, a picocell, a femtocell, or a small cell in relation to the radio area, or ii) may indicate the radio area itself. In i), all devices that provide a predetermined wireless area are controlled by the same entity or interact to configure the wireless area in a collaborative manner. ENB, RRH, antenna, RU, LPN, point, transmit / receive point, transmit point, receive point, etc., according to the configuration method of the radio area, are an embodiment of the base station. In ii), the radio area itself, which receives or transmits a signal from the viewpoint of the user terminal or the neighboring base station, may indicate to the base station itself.

Accordingly, megacell, macrocell, microcell, picocell, femtocell, small cell, RRH, antenna, RU, low power node (LPN), point, eNB, transmit / receive point, transmit point, receive point are collectively referred to as base stations. do.

In this specification, the user terminal and the base station are two transmitting and receiving subjects used to implement the technology or technical idea described herein, and are used in a comprehensive sense and are not limited by terms or words specifically referred to. The user terminal and the base station are two (Uplink or Downlink) transmission / reception subjects used to implement the technology or technical idea described in the present invention and are used in a comprehensive sense and are not limited by terms or words specifically referred to. Here, the uplink (Uplink, UL, or uplink) means a method of transmitting and receiving data to the base station by the user terminal, the downlink (Downlink, DL, or downlink) transmits and receives data to the user terminal by the base station Means the way.

There are no restrictions on the multiple access technique 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 such as 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 interpreted as being limited or limited to a specific wireless communication field, but should be interpreted as including all technical fields to which the spirit of the present invention can be applied.

For uplink transmission and downlink transmission, a time division duplex (TDD) scheme transmitted using different times may be used, or a frequency division duplex (FDD) scheme transmitted using different frequencies may be used.

In addition, in systems 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 downlink include PDCCH (Physical Downlink Control CHannel), PCFICH (Physical Control Format Indicator CHannel), PHICH (Physical Hybrid ARQ Indicator CHannel), PUCCH (Physical Uplink Control CHannel), EPDCCH (Enhanced Physical Downlink Control CHannel), etc. Control information is transmitted through the same control channel, and is composed of data channels such as a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH) to transmit data.

Meanwhile, control information may be transmitted using an enhanced PDCCH (EPDCCH) or an extended PDCCH.

In this specification, a cell is a component carrier having a coverage of a signal transmitted from a transmission / reception point or a signal transmitted from a transmission / reception point, or a transmission / reception point itself. You can.

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

The multiple transmission / reception points include at least one of a base station or a macro cell (hereinafter referred to as 'eNB') and a high transmission power, which is wired and controlled by an optical cable or optical fiber to the eNB, or a low transmission power in the macro cell area. It may be RRH.

Hereinafter, 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 a multiple transmission / reception point. In the downlink, the transmitter may be a part of multiple transmission / reception points, and the receiver may be a part of the terminal. In the uplink, a transmitter may be a part of a terminal, and a receiver may be a part of multiple transmission / reception points.

Hereinafter, a situation in which signals are transmitted / received through channels such as PUCCH, PUSCH, PDCCH, EPDCCH, and PDSCH is also described in the form of 'transmit and receive PUCCH, PUSCH, PDCCH, EPDCCH and PDSCH'.

In addition, hereinafter, description of transmitting or receiving a PDCCH or transmitting or receiving a signal through the PDCCH may be used in a sense 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 are also used to include both PDCCH and EPDCCH.

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

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

The eNB performs downlink transmission to terminals. The eNB is a downlink control information such as a physical downlink shared channel (PDSCH), which is a main physical channel for unicast transmission, and scheduling required for receiving the PDSCH and an uplink data channel (eg 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 as a form in which the corresponding channel is transmitted and received.

[Latency reduction in RAN1 ]

The Latency reduction Study Item was 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 for short TTI [2].

Conduct the study and potential impacts related to RAN1 in the following range [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 at the 3GPP RAN WG1 # 84 meeting 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 to 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 at the 3GPP RAN WG1 # 84bis meeting are as follows.

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, latency is calculated according to the following procedure [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).

In the table 1 above, steps 1-4 and half delay of step 5 is assumed to be due to SR, and rest is assumed for UL data transmission in values shown in Table 4

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, research on a physical layer for a short TTI is ongoing, and discussion on DCI configuration and detection is ongoing. Specifically, a method for constructing search space and blind decoding of sPDCCH and legacy PDCCH is absent.

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

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

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

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

1) Search space definition

◆ Search Space (Cont'd)

● The variable Y _k

√ For the COMMON search space

√ For the UE-specific search space

◆ Size of search space

● CCE units

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

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

◆ Number of PDCCH candidates M ^(L)

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

● Mainly connected to the aggregation level

2) Relationship between Y _k and search space

■ Offset of starting-point of search space

■ Offset ( Y _k ) has UE-specific value within UE-specific search space

■ Offset ( Y _k ) is fixed by zero in common search space

■ Example: CommonSearchSpace

√ Aggregation level ( L ): 4, N _CCE = 35

√ Size of Search space: 16 CCEs

√ Number of candidate ( M ^(L) ): 4

√ Y _k = 0 ( Y _k does not get affected by n _RNTI )

■ Example: UE -specific Search Space

√ Aggregation level ( L ): 4, N _CCE = 35

√ Size of Search space: 8 CCEs

√ Number of candidate ( M ^(L) ): 2

Eventually, based on the defined search space, the maximum Blind decoding number is determined by the terminal to find its PDCCH.

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

In this proposal, we propose a search space definition for two-level DCI considered in sTTI and a blind decoding operation of the terminal.

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

Here, an additional consideration is blind decoding of the terminal.

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

Option 1. Legacy On PDCCH  Define a search space of a relatively large aggregation level, In sPDCCH  Search space of a relatively small aggregation level is allocated. Blind decoding for the same aggregation level is not defined between two search spaces.

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

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

This is because the sTTI-based sPDCCH is expected to have relatively fewer available resources than the legacy PDCCH, so only aggregation level using a relatively small resource is allowed in the sPDCCH definition. Basically, because the common search space uses aggregation level = 4,8, it is expected that the definition in the legacy PDCCH will be beneficial to reduce overhead.

For each search space separation, flexible application is possible through additional signaling during sTTI configuration. That is, when the set for aggregation level L of the UE-specific search space is signaled, the UE performs blind decoding on the aggregation level of the set search space according to the set method.

Specifically, for example, in the case of 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 by sTTI in a subframe

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

Option 2. Legacy PDCCH  Define only common search space, sPDCCH  Only UE-specific search space is defined.

In this proposal, unlike the above-mentioned method 1, defining the common search space to the sPDCCH up to the common search space can be used as 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 Means

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

Specifically, for example, a hashing function can be defined as in the following equation.

-Legacy PDCCH

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

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

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

Method 3. sPDCCH  Define only the minimum aggregation level, and the remaining search space is 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 resource for sPDCCH, it can be operated in the manner with the lowest control overhead of sTTI.

Specifically, for example, in the case of 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 by sTTI in a subframe

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

Method 4. sPDSCH  Lowest CCE index for A / N setting is sTTI  It is defined by applying the offset in subframe units.

In this proposal, we propose a CCE indexing method according to search space separation. Separate CCE index can be performed for each area, but in some cases, alignment of search space defined in legacy PDCCH and sPDCCH in a subframe may be necessary.

Therefore, this proposal proposes a total of three CCE indexing methods for search space.

Option 4-1) legacy PDCCH and sPDCCH  Construct a separate search space.

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

Referring to FIG. 8, the search spaces of legacy PDCCH and sPDCCH are separately configured, and CCE indexes are independently assigned to each other.

Option 4-2) legacy On PDCCH  next by sTTI sPDCCH  Connect to compose a search space.

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

9, sPDCCH for each sTTI is connected to the legacy PDCCH to configure a search space. Therefore, the CCE index of each sPDCCH for each sTTI is subsequently assigned to the CCE index of the legacy PDCCH.

Option 4-3) legacy On PDCCH by sTTI  By setting an offset, a continuous search space is constructed.

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

Referring to Figure 10, since the sPDCCH is sequentially connected to the legacy PDCCH to form a search space, the CCE index of the sPDCCH is the 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 specific method for configuring a search space for sTTI-based DCI transmission and reception has been described, and the principle can be applied to similar signals and channels as it is.

11 shows a process of a method for detecting DCI in an sTTI frame structure according to the present embodiments, and shows how a base station constructs a search space for legacy PDCCH and sPDCCH.

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

Here, the base station can be configured to separate 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) in the search space of the legacy PDCCH, and a search space of sPDCCH is configured in a relatively small aggregation level (eg, L = 1,2). By doing so, 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 legacy PDCCH may be configured as a common search space, and the search space of sPDCCH may be configured as a UE-specific search space.

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

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

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

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

For example, the search space of the legacy PDCCH is composed of a relatively large aggregation level L = 4,8, and the search space of the sPDCCH can receive search space information composed of 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 is configured with an aggregation level corresponding to the common search space, and the search space of the sPDCCH may receive search space information composed of a UE-specific search space.

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

By separating the search space of Legacy PDCCH and the search space of sPDCCH and signaling information about the separated search space to the terminal, the terminal reduces the complexity of blind decoding and enables blind decoding.

13 shows a configuration of the base station 1300 according to the present embodiments.

Referring to FIG. 13, the base station 1300 according to the present exemplary embodiment includes a control unit 1310, a transmission unit 1320, and a reception unit 1330.

The controller 1310 controls the operation of the overall base station 1300 as the above-described embodiments provide a search space configuration and blind decoding scheme of sPDCCH and legacy PDCCH for short TTI frames.

The transmitting unit 1320 and the receiving unit 1330 are used to transmit and receive signals, messages, and data necessary to perform the present invention described above.

14 shows the configuration of the user terminal 1400 according to the present embodiments.

Referring to FIG. 14, the user terminal 1400 according to the present exemplary embodiment includes a receiver 1410, a control unit 1420, and a transmitter 1430.

The reception unit 1410 receives downlink control information, data, and messages from a base station through a corresponding channel.

In addition, the control unit 1420 controls the operation of the overall user terminal 1400 as the above-described embodiments provide a search space configuration and blind decoding scheme of sPDCCH and legacy PDCCH for short TTI frames.

The transmitter 1430 transmits uplink control information, data, and a message to the base station through a corresponding channel.

The standard contents or standard documents mentioned in the above-described embodiments are omitted to simplify the description of the specification and constitute a part of the specification. Therefore, it is to be construed that adding the contents of the above standard contents and parts of the standard documents to the specification or in the claims falls 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 variations 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 explain them, 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 interpreted by the claims below, and all technical spirits within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims (21)

delete delete delete delete delete delete delete delete delete A method for detecting downlink control information in a frame structure having 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
And performing blind decoding based on the first aggregation level and the second aggregation level,
The first aggregation level and the second aggregation level are set separately from each other,
When the second transmission time interval is a short transmission time interval (sTTI), the aggregation level is composed of 1, 2, 4, and 8 for a terminal-specific search space, and a value set from 1, 2, 4, and 8 Is received from this base station,
Further comprising the step of receiving the short transmission time interval (sTTI) configuration information from the base station,
The short transmission time interval configuration information,
It includes information for indicating the value of the one of the set level for the configured terminal-specific search space,
The first aggregation level is an aggregation level corresponding to a common search space, and the second aggregation level is an aggregation level for the terminal specific search space,
The step of performing the decoding,
A method of performing blind decoding on a downlink control channel of the second transmission time interval based on a set level corresponding to the one value indicated based on the short transmission time interval configuration information. delete delete delete delete delete In the terminal for detecting the downlink control information in a frame structure of a short transmission time interval,
A receiver configured to receive a downlink control channel at a first transmission time interval set at a first aggregation level and receive a downlink control channel at a second transmission time interval set at a second aggregation level; And
And a control unit performing blind decoding based on the first aggregation level and the second aggregation level,
The first aggregation level and the second aggregation level are set separately from each other,
When the second transmission time interval is a short transmission time interval (sTTI), the aggregation level is composed of 1, 2, 4, and 8 for a terminal-specific search space, and a value set from 1, 2, 4, and 8 Is received from this base station,
The receiving unit,
Receiving the short transmission time interval (sTTI) configuration information from the base station,
The short transmission time interval configuration information,
Contains information for indicating the value of one of the set level for the configured terminal-specific search space,
The first aggregation level is an aggregation level corresponding to a common search space, and the second aggregation level is an aggregation level for the terminal-specific search space,
The control unit,
A terminal that performs blind decoding on the downlink control channel of the second transmission time interval based on the aggregation level corresponding to the one value indicated based on the short transmission time interval configuration information. delete delete delete delete delete

Images