KR20180016688A - Apparatus and method of short PUCCH design based on the partially overlapped DMRS in a short TTI frame structure - Google Patents

Abstract

Embodiments of the present invention suggest a novel short transmit time interval (sTTI) based physical uplink control channel (sPUCCH) design method having a structure that the existing physical channel defined in a TTI is partially overlapped between reference signals among adjacent sTTIs. The method of the present invention can be directly applied to an sPUCCH design based on an sTTI structure having the number of symbols of three or four, and provides a benefit that an sPUCCH is unnecessary to define a new reference signal and a data channel region by intactly reusing the existing legacy PUCCH structure in an sTTI structure with four symbols.

Description

TECHNICAL FIELD [0001] The present invention relates to a short PUCCH design method based on a partial overlapping reference signal in a short TTI frame, and to a short TUC frame structure based on the PUCCH design based on a short PUCCH design.

The embodiments relate to a specific method for transmitting a short TTI-based short PUCCH in a 3GPP LTE / LTE-A system.

In one embodiment, a short PUCCH design method based on a partial overlapping reference signal in a Short TTI frame comprises the steps of: allocating a first sPUCCH (N + 1) OFDM symbol from a first OFDM symbol to a (N + And constructing a second sPUCCH from the (N + 1) th OFDM symbol to the (2N + 1) th OFDM symbol with the structure that the (N + 1) th OFDM symbol is superimposed, to provide.

1 is a diagram illustrating eNB and UE processing delays and HARQ RTT.
2 shows a resource mapping per PRB in one subframe.
3 shows a legacy PUCCH uplink structure.
FIG. 4 is a diagram illustrating an example of sPUCCH setting based on Overlapping RS.
5 is a view showing the sPUCCH design concept of the embodiment 1-1.
FIG. 6 is a diagram illustrating an example of the sPUCCH setting (3 DMRS symbols) based on Overlapping RS.
7 is a view showing the sPUCCH design concept of the embodiment 1-2.
8 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.
9 is a diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[Latency reduction in RAN1]

The Latency reduction Study Item was approved at RAN plenary # 69 meeting [1]. The main purpose of latency reduction is to standardize shorter TTI operations to foster TCP throughput [2]. For this, performance verification for short TTI has already been performed in RAN2 [2].

Potential impacts and studies related to RAN1 are performed in the following ranges [1]:

o Assessment of impact and performance of TTI lengths between 0.5ms and one OFDM symbols, taking into account the impact of 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 an SDSCH 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, the 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: 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 The sTTI operation for Pcell and / or SCells by (e) CA in addition to non- (e) CA case

Basically, in the average down-link latency calculation, the latency is calculated according to the following procedure [3].

The following is 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 consisting of 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 + 1 TTI + 1.5 TTI UE + 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., send to TCP ACK. Following table 1 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 of the step 5 are assumed to be due to SR, and the rest is assumed to be 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 are short TTI duration are assumed.

TBS Calculation of short TTI

According to the present invention, the PDSCH is calculated as follows:

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

As described above, studies on the physical layer for the short TTI are underway, and there is no specific setting and transmission method for the sPUCCH for transmitting the Ack / Nack feedback for the sPDSCH reception.

The present invention proposes a 4-symbol-based short TTI based PUCCH (pUCCH) setting and a concrete transmission method for a short TTI frame.

Unlike the existing LTE / LTE-A frame structure (TTI = 1ms = 14 OFDM symbols), short TTI can be composed of 1, 4, and 7 symbols. At this time, the setting for the sPUCCH that carries the A / N feedback of the sPDSCH based on the short TTI frame structure must be different from the legacy PUCCH. This is because the existing PUCCH is determined based on 14 OFDM symbols, whereas the existing A / N multiplexing scheme can not be applied to the sTTI based sPUCCH defined with fewer number of symbols.

In the specific work item scope, unlike the existing LTE / LTE-A frame structure (TTI = 1ms = 14 OFDM symbols), short TTI consists of 2-symbol, 4-symbol or 1 slot (= 7-symbol) . In the legacy TTI, slot-based PUCCH hopping is performed as shown in FIG. This PUSCH hopping increases the frequency diversity of the PUCCH and consequently increases the coverage of the PUCCH. This is because basically the same signal or one information sequence is transmitted through different frequency bands, so that there is a gain to obtain diversity.

However, in the sTTI-based sPUCCH, the number of repeated transmissions of the sPUCCH is limited due to the limitation of the number of symbols. As a result, the coverage constraint and transmission / reception performance (eg, BER, BLER) may be lowered.

In this proposal, we propose a method to define a partially overlapping based sPUCCH based on a 4-symbol based sTTI even in a short TTI structure.

Method 1. Adjacent sTTI  The reference signal is partially overlapped sPUCCH  Define resources.

In this proposal, we propose a new sPUCCH design method with a structure in which the physical channels defined in the existing TTI (Transmit Time Interval) are partially overlapped among the reference signals between adjacent sTTIs.

In this proposal, it is possible to apply directly to the sPTCH structure based on the sTTI structure, in which the number of symbols is 3 or 4. In particular, since the existing legacy PUCCH structure can be reused as it is in the 4-symbol sTTI structure, a new reference signal and a data channel region definition for the sPUCCH are not required.

For example, as shown in FIG. 4, a total of seven OFDM symbols exist in the unit slot structure based on the Normal CP standard. Therefore, if a structure for overlapping one reference signal is selected, the sPUCCH can be configured with a structure in which four OFDM symbols exist as shown in FIG. Through this, a total of two sTTI regions are divided in units of slots, and sPUCCHs can be defined, respectively. In this proposal, flexible sPUCCH configuration is possible by adjusting the overlapping reference signal region. That is, by defining the reference signal region of the partially overlapped sPUCCH, multiple sPUCCH can be set for each slot unit.

Example  1-1. 3- symbol  Data (A / N transmission) + 1 symbol  The reference signal ( sPUCCH  Channel estimation)

SPUCCH is defined as shown in FIG. Since the A / N capability of the sPUCCH is related to the total number of reference signals, the orthogonal resource of the entire reference signal based on a single RB (12 subcarriers) is a cyclic shift number 'n _CS = 12 _{', and the} orthogonal code number' n _OC = 1 '(see FIG. 5).

Therefore, since an orthogonal cover code sequence (= spreading code) can not be defined in a single reference signal symbol resource, an A / N transmission interval and a single symbol reference signal using an existing OCC code of Length = 3 exist Structure. As a result, since two sPUCCHs share a single reference signal, the sPUCCH-specific capability is n _CS / 2 = 6. The orthogonal sequence used in the A / N data symbol interval can be reused as the sequence set defined in the existing 3GPP TS 36.211 as shown in Table 3, and one of the defined sequences can be used. Or the cyclic shift (CS) of the ZC sequence according to a predefined pattern as shown in Tables 4 and 5.

Example  1-2. 2- symbol  Data (A / N transmission) + 3 symbol  The reference signal ( sPUCCH channel  calculation)

SPUCCH is defined as shown in FIG. Since the A / N capability of the sPUCCH is related to the total number of reference signals, the orthogonal resource of the entire reference signal based on a single RB (12 subcarriers) is a cyclic shift number 'n _CS = 12 _{', and the} orthogonal code number' n _OC X n _CS = 36 '(see FIG. 7).

This is because the Length = 3 OCC code is applied to the overlapping DMRS consisting of 3 symbols. On the other hand, since the number of symbols for transmitting A / N data per single s pUCCH is 2, an OCC code of length = 2 can be used. As a result, since the two sPUCCHs share a reference signal, the sPUCCH-specific capability is n _OC X n _CS / 2 = 18. As shown in Table 6, the Orthogonal sequence used in the A / N data symbol interval can be reused as part of the sequence set defined in the existing 3GPP TS 36.211 as shown in Table 7. [

Or, to divide the data orthogonal resource with the DMRS, an equal A / N capability may be set between sPUCCHs partially overlapped by the DMRS, or a certain sPUCCH may be set with a weighted A / N capability.

The orthogonal sequence and the cyclic shift pairing relationship between the data channel and the DMRS can be classified as follows.

Example 1-2-1) Adjacent between sPUCCH  If the capability is unevenly divided

In this case, the A / N multiplexing capability is weighted to a specific sPUCCH. In this case, it is possible to implement a specific cyclic shift or OCC by assigning a lot to a specific sPUCCH. This is possible, for example, by allocating more OCC sets to specific sPUCCHs (Table 9).

Example 1-2-2) Adjacent between sPUCCH  In case of capability equalization

In this case, the A / N multiplexing capability is uniformly given between adjacent sPUCCHs. In this case, it is necessary to allocate the same orthogonal resource through a specific cyclic shift or OCC combination. This is possible, for example, by assigning a linkage between OCC set and cyclic shift according to a predefined method (Table 10).

The present invention describes a concrete transmission method for setting and transmitting a sTTI-based overlapping s pUCCH. The method can be applied to similar signals and channels as it is, and its application is not limited to the new frame structure.

FIG. 9 is a diagram illustrating a configuration of a base station according to another embodiment.

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

The controller 1010 controls the overall operation of the base station according to the above-described present invention, in which the reference signal between the adjacent sTTIs in the short TTI frame constitutes the sPUCCH resource partially overlapped.

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

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

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

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

In addition, the controller 1120 controls the overall operation of the SS according to the present invention, which constitutes the sPUCCH resource in which the neighboring sTTI reference signals are partially overlapped in the short TTI frame.

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

The standard content or standard documents referred to in the above-mentioned embodiments constitute a part of this specification, for the sake of simplicity of description of the specification. Therefore, it is to be understood that the content of the above standard content and some of the standard documents is added to or contained in the scope of the present invention, 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 Latency reduction techniques for LTE", Ericsson (Rapporteur)

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

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

Claims (1)

In a short overlapping reference signal based short PUCCH design method in a short TTI frame,
Constructing a first sPUCCH from a first OFDM symbol to an (N + 1) -th OFDM symbol in a slot composed of (2N + 1) OFDM symbols; And
And configuring a second sPUCCH from the (N + 1) th OFDM symbol to the (2N + 1) th OFDM symbol with the structure that the (N + 1) th OFDM symbol is superposed.

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