KR20170108202A

KR20170108202A - Apparatus and method of resource allocation based on short TTI frame structure

Info

Publication number: KR20170108202A
Application number: KR1020160031507A
Authority: KR
Inventors: 김기태; 최우진
Original assignee: 주식회사 케이티
Priority date: 2016-03-16
Filing date: 2016-03-16
Publication date: 2017-09-27

Abstract

The present invention relates to a method of constructing short TTI frame-based resource allocation information and a corresponding control information transmission method, and more particularly, to a method and apparatus for allocating sPDSCH / sPUSCH in a short TTI frame structure having a number smaller than the number of symbols constituting a conventional LTE / LTE- And more particularly, to a method of allocating resources in consideration of sPDCCH.

Description

TECHNICAL FIELD [0001] The present invention relates to a Short TTI frame structure resource allocation method and apparatus,

The present invention relates to a short TTI frame-based resource allocation method in a 3GPP LTE / LTE-A system.

According to an embodiment of the present invention, there is provided a method for receiving resource allocation information in a frame basis, the base station including a predetermined number of symbols, the method comprising: receiving information on a starting location of a resource allocation through a downlink control channel And checking the information on the remaining resource allocation using information on the starting location of the received resource allocation and predefined information on the resource allocation.

1 is a diagram illustrating eNB and UE processing delays and HARQ RTT.
2 shows a resource mapping per PRB in one subframe.
FIG. 3 is a diagram showing an example of resource allocation by RA type 0 (10 MHz case).
4 is a diagram showing an example of resource allocation by RA type 1 (15 RB case).
5 is a diagram illustrating an example of resource allocation by RA type 2 (50 RB case).
6 is a diagram showing an example of sTTI setting.
7 is a conceptual diagram of frequency-time domain resource allocation based on sTTI.
FIG. 8 is a diagram illustrating an example of application of the sTTI-based frequency-domain resource allocation length.
9 is a conceptual diagram of independent RBG pattern setting for each sTTI.
10 is a diagram illustrating an example of Cyclic manner-based RBG allocation.
11 is a diagram showing an example of the sTTI region setting.
FIG. 12 is a diagram illustrating a configuration of a base station according to another embodiment.
13 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 numerals whenever 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. 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 a transmission / reception point of a signal transmitted from a transmission / reception point, and the 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].

Figure 1: Assuming the 3GPP TR 36.912, the LTE U-plane one-way latency for a scheduled UE consists of fixed node processing delays and 1 TTI duration for transmission. 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 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., 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, steps 1 and 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:

[Resource allocation in LTE / LTE -A]

Note: TS 36.213 7.1.6 Resource allocation

The 3GPP standard defines a resource allocation type in which the scheduler allocates RBs. For flexibility of resource allocation, a way to maximize the flexibility of RB allocation is to use bit map. At this time, each bit indicates whether each RB is allocated or not. However, while this method can maximize the flexibility of resource allocation, it can cause considerable complexity of the resource allocation process or require a lot of data control information in resource allocation.

Therefore, LTE systems can define several resource allocation types and use them according to predefined processes. There are three different types of resource allocation types 0, 1, and 2, and resource allocation types for each DCI format are shown in Table 3 below.

Resource allocation type 0

RA type 0 is the simplest RB allocation scheme. First, the RBs are divided into several groups. Here, the divided group is referred to as RBG, and this value is determined according to the size of the system band. Table 4 shows the RBG sizes according to the system bandwidth.

First, RB is defined as RBG according to the size of the system band. Each bit of the bit string according to the bit map allocation means allocation of the RBG. RA type 0 requires the entire N _RB ^DL-- / P bit.

For example, in the case of 10 MHz (= 50 RBs), for example, the total required number of bits is N _RB ^DL ^- / P = 50/3 = 17. An example of the actual RB allocation according to this is shown in FIG.

Resource allocation type 1

RA type 1 uses RBG similar to RA type 0, but the specific method is different.

Once the entire allocation field is defined as three areas.

The first field is log ₂ (P) bits are used to determine the subset group.

The second field is used to indicate whether to shift the RB in the subset using 1 bit.

The third field uses the bitmap to refer to the individual RBs of the selected RBG subset. The total ratio is as follows.

N _RB ^TYPE1 = N _RB ^DL ^- / P - log ₂ (P) - One

For example, the total system BW is 15 RB and the RBG subset (P) is 2.

Thus the first field is used to refer to the RBG subset with 1 bit (= log2 (2)).

Next, the shift value is 1 bit.

Finally, the allocation bits used for individual RB designations are N _RB ^DL ^- / P - log ₂ (P) - 1 = 8-1-1 = 6 bits.

For example, assuming that the total resource allocation bit is '00110011', the MSB refers to the RBG subset number.

The second bit indicates on / off for the shift.

The last 6 bits indicate the allocation of the actual PRB.

Referring to FIG. 4, since the RBG subset '0' and the shift value '0' are not used and the remaining 6 bits are '110011', '00110011' → 'RB number 0, 1, 8, 9' do.

Resource Allocation Type 2

Here, both continuous PRB allocation and non-consecutive PRB allocation are supported, and a 1-bit flag distinguishes the operation. Type 2 Resource Indication Value (RIV) is basically divided into Starting RB area (RBSTART) and Contiguously allocated RB (LCRBs). The concrete value is defined by the following formula.

For example, FIG. 5 illustrates an example of resource allocation for 50RB, which is an example of the following Localized allocation.

As described above, research on the physical layer for short TTI is underway, and there is no frame structure based resource allocation method and control information configuration method for specific short TTI.

In the present invention, a short TTI frame-based resource allocation information configuration method and a corresponding control information transmission method are transmitted.

Unlike the existing LTE / LTE-A frame structure (TTI = 1ms = 14 OFDM symbols), short TTI can be composed of 1, 2, 3, 4, and 7 symbols. At this time, a method of constructing data transmission control information for sPDSCH / sPUSCH allocation based on a short TTI frame structure is required, and specifically, a resource allocation method considering sPDCCH is proposed.

Solution 1. sPDCCH The resource allocation information includes only the start point.

Basically, the PDCCH for Short TTI (sPDCCH) can assume the action of reducing the information itself as much as possible. This is because the sTTI itself is defined as a frequency-time resource smaller than the existing TTI as shown in FIG. 6, so that the sPDCCH control information for dynamic scheduling should also be small. Therefore, this proposal suggests a method to define a method to allocate only the starting position of resource allocation. That is, since the terminal obtains information on the starting point in assuming the sTTI-based resource allocation field, information on the remaining allocation should be interpreted according to predefined information.

Specifically, the following allocation scheme is proposed in allocating resources in the frequency domain of the sTTI.

However, PRB By grouping And assigns them to a predefined number. At this time, sPDCCH Starting with point information Of RBG It means start index.

In this proposal, it is assumed that a frequency domain resource for short TTI can be defined, for example, as follows. That is, it is assumed that RBs, which are the minimum scheduling units in the frequency domain, are grouped into several RBGs and that the frequency resources for the latency reduction service are allocated in advance. At this time, 3 bits of information to be transmitted to the UE through the sPDCCH is sufficient. That is, only the starting point of the resource allocation among the six RBGs in FIG. 7 is recognized by the UE. For example, if the information acquired from the sPDCCH by the UE is 001, RBG # 1 is the starting point of the frequency domain resource allocation.

However, PRB Grouping The information corresponding to the pattern and Length is RRC Signaling through To the terminals Lt; / RTI >

This proposal includes the concept of allocating RBG specifically in the sTTI-based resource allocation. In order to minimize the RA information of the sPDCCH, only the start position of the resource is transmitted in the corresponding area. Therefore, the information corresponding to the length that determines the allocation amount of the actual resource must be determined with the terminals in advance. In this method, even if the data to be transmitted is small, the predefined resources are unconditionally occupied and the other terminals can not use it, and the flexibility of resource allocation is reduced. At this time, the sTTI frequency length information indicating the frequency resource length can be transmitted to the UEs through the RRC signaling. Therefore, the signaling can be regarded as semi-static information.

Fig. 8 shows an embodiment of the proposed method. That is, the process of the terminal interprets the resource allocation corresponding to the predefined length information at the starting point.

The terminal analyzes the RA field of '001' through the sPDCCH and determines RBG # 1 as the start position. In this case, the 'Length = 3' information known in advance through the RRC signaling can be completely known to the UE's own resource allocation information in the sTTI as shown in FIG.

Next, the RBG pattern can be defined and used in advance as shown in FIG. At this time, the sTTI-based pattern may have an independent pattern for each sTTI. FIG. 9 conceptually represents different RBG definitions in all the sTTI regions. Basically, the RBG pattern can be defined in the following categories.

- All sTTIs in Legacy TTI (1ms) use the same RBG pattern

- All sTTIs in the legacy system frame (10ms) use the same RBG pattern

- All sTTIs in the Legacy slot (0.5ms) use the same RBG pattern

- Use different RBG patterns per sTTI

The RBG pattern information may also be directly transmitted to the UEs through the RRC signaling, so that the corresponding signaling can be regarded as semi-static information.

However, PRB Grouping Pattern and Length information are broadcast or general control information. To the terminals Transmission can be transmitted.

This proposal is the same as 'Method 1-2)', except that the PRB grouping pattern and the length information are different from each other by using a common information transfer process instead of RRC signaling. That is, it is possible to transmit through the broadcasting channel to the terminal, and if the existing broadcasting channel can not be used, it is necessary to redefine the broadcasting channel for the sTTI.

Methods 1-4) Predefined PRB If the length of the groups exceeds the system bandwidth, a cyclic manner (modulo N type ) Scheme.

In this proposal, when the length of the RBG exceeds the last RBG index at the start position of the RBG, it means that the order is continuous to the first RBG index in a cyclic shift form. FIG. 10 shows an example of RBG length information analysis based on a cyclic manner. If the starting position is RBG # 4 and Length = 3, it can be seen that the last allocation is RBG # 0.

Solution 2. sPDCCH Specific frequency domain sTTI And allocates them to areas.

In order to minimize collision with existing systems and to guarantee backward compatibility, a specific frequency domain can be defined as a sTTI region. When the corresponding area is set, it is possible to reapply the proposed scheme in 'Plan 1' as it is. At this time, the sTTI region setting information can also transmit predefined information to the UEs using RRC signaling or broadcasting information. FIG. 11 shows an embodiment of Method 2, which shows that specific RBs are defined as two area sTTI regions.

The following additional considerations can be taken into account when defining the sTTI region.

Solution 2-1) For backward compatibility of legacy terminals, At 6RB Excludes assignments.

Solution 2-2) The edge region of the whole frequency band sTTI Sector area.

Solution 2-3) Apply the same settings for DL / UL commonality.

In case of 'Method 2-3', it is possible in the area except 6RB of DL and PUCCH area of UL, and simple resource allocation procedure can be applied through this method.

In the present invention, a sTTI-based resource allocation scheme and a concrete delivery method for transferring configuration information are described. The method can be applied to similar signals and channels as they are, and the application is not limited to the new frame structure.

FIG. 12 is a diagram illustrating a configuration of a base station according to another embodiment.

Referring to FIG. 12, 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 configures the data transmission control information for the sPDSCH / sPUSCH allocation in a short TTI frame structure composed of a number smaller than the number of symbols constituting the existing LTE / LTE-A frame structure necessary for carrying out the present invention described above And controls the overall operation of the base station according to the manner in which the base station operates.

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.

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

13, 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.

Also, the controller 1120 transmits data transmission control information for sPDSCH / sPUSCH allocation in a short TTI frame structure configured with a number smaller than the number of symbols constituting the existing LTE / LTE-A frame structure required for performing the present invention And controls the overall operation of the terminal according to the method of configuring the terminal.

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.

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

A method for receiving resource allocation information in a frame based on a preset number of symbols,
Receiving information on a starting position of resource allocation from a base station through a downlink control channel; And
And checking information about remaining resource allocations using information about a starting location of the received resource allocations and predefined information about resource allocations.