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NR Frame Structure and Air Interface Resources

2018-05-20

5G Training Course

Security Level:

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

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Contents

1 Numerology

2 Time-Domain Resources

3 Frequency-Domain Resources

4 Space-Domain Resources

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Overview of NR Air Interface Resources (Time-, Frequency-, and Space-domain Resources)

Numerology (system parameter): refers to subcarrier spacing (SCS) in New Radio (NR) and related parameters, such as the symbol length and cyclic prefix (CP) length.

Numerology

Time-domain

resources

Frequency-domain

resources

Space-domain resources

Symbol length

SCS

CP

Slot

1 slot = 14 symbols

Subframe

Frame

REG

CCE

RB

RBG

Bandwidth part

(BWP)

Carrier

1 subframe = 1 ms

1 frame = 10 ms

1 RB = 12 subcarriers

Antenna port

QCL

Basic scheduling unit

1 RBG = 2 to 16 RBs

1 BWP = Multiple RBs/RBGs

One or more BWPs can be configured in one carrier.

1 REG = 1 PRB

1 CCE = 6 REGs

Data channel/control channel scheduling unit

Existed in LTE

Unchanged in NR

Existed in LTE

Modified in NR

Added in NR

The SCS determines the symbol length and slot length.

Codeword

Layer

NR uses orthogonal frequency division multiple access (OFDMA), same as LTE does.

The main description dimensions of air interface resources are similar between LTE and NR except that BWP is added to NR in the frequency domain.

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SCS–Background and Protocol-provided Definition

    • Numerologies defined in 3GPP Release 15 (TS 38.211) with SCS identified by the parameter µ.

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    • Available SCS for data channels and synchronization channels in 3GPP Release 15

Parameter

µ

SCS

CP

0

15 kHz

Normal

1

30 kHz

Normal

2

60 kHz

Normal, extended

3

120 kHz

Normal

4

240 kHz

Normal

Based on LTE SCS of 15 kHz, a series of numerologies (mainly different SCS values) are supported to adapt to different requirements and channel characteristics.

Parameter

µ

SCS

Supported for Data

(PDSCH, PUSCH etc)

Supported for Sync

(PSS, SSS, PBCH)

0

15 kHz

Yes

Yes

1

30 kHz

Yes

Yes

2

60 kHz

Yes

No

3

120 kHz

Yes

Yes

4

240 kHz

No

Yes

*(LTE supports only 15 kHz SCS.)

    • Background
    • Service types supported by NR: eMBB, URLLC, mMTC, etc.
    • Frequency bands supported by NR: C-band, mmWave, etc.
    • Moving speed supported by NR: up to 500 km/h
    • Requirements for SCS vary with service types, frequency bands, and moving speeds.
    • URLLC service (short latency): large SCS
    • Low frequency band (wide coverage): small SCS
    • High frequency band (large bandwidth, phase noise): large SCS
    • Ultra high speed mobility: large SCS
    • NR SCS design principle
    • NR supports a series of SCS values.

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SCS: Application Scenarios and Suggestions

    • Coexistence of different SCS values and FDM
    • The eMBB and URLLC data channels use different SCS values and coexist through FDM.

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    • The PBCH and PDSCH/PUSCH use different SCS values and coexist through FDM.
    • Impact of SCS on coverage, latency, mobility, and phase noise
    • Coverage: The smaller the SCS, the longer the symbol length/CP, and the better the coverage.
    • Mobility: The larger the SCS, the smaller the impact of Doppler shift, and the better the performance.
    • Latency: The larger the SCS, the shorter the symbol length/latency.
    • Phase noise: The larger the SCS, the smaller the impact of phase noise, and the better the performance.
    • SCS application suggestions for different frequency bands (eMBB service data channel):

SCS (kHz)

15

30

60

120

240

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3.5 GHz

28 GHz

Coverage

Mobility

Latency

Coverage

Mobility

Latency

good

bad

good

bad

good

bad

good

bad

good

bad

good

bad

good

bad

Phase Noise

It is recommended that the SCS be 30 kHz for C-band and 120 kHz for 28 GHz. Different SCS values and coexistence through FDM are supported.

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SCS Configuration for Physical Channels and Signals

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Channel

SCS Defined in 3GPP Release 15

Configuration Scheme

Initial access

SS/PBCH

Sub-6 GHz: 15/30 kHz

Above-6 GHz: 120/240 kHz

RAN4 defines the default SCS for each frequency band (see Table 5.4.3.3-1 in 3GPP TS 38.104).

RMSI, Msg2/4 (PDSCH)

Sub-6 GHz: 15/30 kHz

Above-6 GHz: 60/120 kHz

MIB

Msg1 (PRACH), Msg3 (PUSCH)

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Long PRACH: SCS = {1.25 5} kHz

Short PRACH: SCS = {15, 30, 60, 120} kHz, where: sub-6 GHz: 15/30 kHz, above-6 GHz: 60/120 kHz

RMSI

RRC connected mode

PDSCH/PDCCH/CSI-RS

Sub-1 GHz: 15/30 kHz

1 GHz to 6 GHz: 15/30/60 kHz

Above-6 GHz: 60/120 kHz

RRC signaling

PUSCH/PUCCH/SRS

Sub-1 GHz: 15/30 kHz

1 GHz to 6 GHz: 15/30/60 kHz

Above-6 GHz: 60/120 kHz

RRC signaling

The protocol-defined SCS is used by the synchronization and broadcast channels involved in initial access. The SCS for other channels is configured in the MIB, RMSI, and RRC signaling.

gNodeB

UE

SS/PBCH

SCS: protocol-defined default value

PRACH

SCS: configured in RMSI

RMSI (SIB1)

SCS: configured in MIB

Msg2 (random access response)

SCS: same as RMSI

Msg3 (transmitted over PUSCH)

SCS: configured in RMSI

Msg4 (transmitted over PDSCH)

SCS: same as RMSI

DL: PDSCH/PDCCH/CSI-RS

SCS: configured in RRC signaling

UL: PUSCH/PUCCH/SRS

SCS: configured in RRC signaling

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Contents

2 Time-Domain Resources: CP, Symbol, Slot, Frame Structure

1 Numerology

3 Frequency-Domain Resources

4 Space-Domain Resources

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Time-domain Resources: Radio Frame, Subframe, Slot, Symbol

Radio frame

Subframe

Subframe

Subframe

...

Slot

Slot

Slot

...

Inherited from LTE and has a fixed value of 1 ms

Symbol

Symbol

Symbol

...

Symbol

Inherited from LTE and has a fixed value of 10 ms

Basic unit for modulation

Minimum unit for data scheduling

Sampling point

...

Sampling point

Sampling point

Basic time unit at the physical layer

In the time domain, slot is a basic scheduling unit for data channels. The concepts of radio frames and subframes are the same as those in LTE.

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Symbol Length–Determined by SCS

    • Symbol = CP + Data
    • SCS vs CP length/symbol length/slot length
    • Length of OFDM symbols in data: T_data = 1/SCS
    • CP length: T_cp = 144/2048 x T_data
    • Symbol length (data+CP): T_symbol = T_data +T_cp
    • Slot length: T_slot = 1 / 2^(µ)

Parameter/Numerology (µ)

0

1

2

3

4

SCS (kHz):

SCS = 15 x 2^(µ)

15

30

60

120

240

OFDM Symbol Duration (µs):

T_data = 1/SCS

66.67

33.33

16.67

8.33

4.17

CP Duration (µs):

T_cp = 144/2048 x T_data

4.69

2.34

1.17

0.59

0.29

OFDM Symbol Including CP (µs):

T_symbol = T_data + T_cp

71.35

35.68

17.84

8.92

4.46

Slot Length (ms):

T_slot = 1/2^(µ)

1

0.5

0.25

0.125

0.0625

CP

data

…

T_slot = 1 ms (14 symbols)

SCS = 15 kHz

…

T_slot = 0.5 ms (14 symbols)

SCS = 30 kHz

…

T_slot = 0.125 ms (14 symbols)

SCS = 120 kHz

T_symbol

T_symbol

T_symbol

A symbol consists of a CP and data. The length of the data is the reciprocal of SCS. The larger the SCS, the smaller the symbol length and the slot length.

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CP: Background and Principles

    • Multipath latency extension
    • The width extension of the received signal pulse caused by multipath is the difference between the maximum transmission latency and the minimum transmission latency. The latency extension varies with the environment, terrain, and clutter, and does not have an absolute mapping relationship with the cell radius.
    • Impact
    • Inter-Symbol Interference (ISI) is generated, which severely affects the transmission quality of digital signals.
    • Inter-Channel Interference (ICI) is generated. The orthogonality of the subcarriers in the OFDM system is damaged, which affects the demodulation on the receive side.
    • Solution: CP for reduced ISI and ICI
    • Guard intervals reduce ISI. A guard interval is inserted between OFDM symbols, where the length (Tg) of the guard interval is generally greater than the maximum latency extension over the radio channel.
    • CP is inserted in the guard interval to reduce ICI. Replicating a sampling point following each OFDM symbol to the front of the OFDM symbol. This ensures that the number of waveform periods included in a latency copy of the OFDM symbol is an integer in an FFT period, which guarantees subcarrier orthogonality.

CPs between OFDM symbols resolve ISI and ICI caused by multipath propagation.

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CP: Protocol-defined

    • CP length for different SCS values:
    • Key factors that determine the CP length
    • Multipath latency extension: The larger the multipath latency extension, the longer the CP.
    • OFDM symbol length: Given the same OFDM symbol length, a longer CP indicates a larger system overhead.
    • NR CP design principle
    • Same overhead as that in LTE
    • Aligned symbols between different SCS values and the reference numerology (15 kHz)

Parameter

µ

SCS

(kHz)

CP

(µs)

0

15

NCP: 5.2 µs for l = 0 or 7; 4.69 µs for others

1

30

NCP: 2.86 µs for l = 0 or 14; 2.34 µs for others

2

60

NCP: 1.69 µs for l = 0 or 28; 1.17 µs for others

Extended CP (ECP): 4.17 µs

3

120

NCP: 1.11 µs for l = 0 or 56; 0.59 µs for others

4

240

NCP: 0.81 µs for l = 0 or 112; 0.29 µs for others

0

1

2

3

1

1

1

    • If normal CP (NCP) is used, the CP of the first symbol present every 0.5 ms is longer than that of other symbols.

The CP length in NR is designed in line with the same principles as LTE. Overheads are the same between NR and LTE. Aligned symbols are ensured between different SCS values and the SCS of 15 kHz.

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Frame Structure: Architecture

    • Frame structure architecture:
      • Example: SCS = 30 kHz/120 kHz

SCS

(kHz)

Slot Configuration (NCP)

Number of Symbols/Slot 

Number of Slots/Subframe

Number of Slots

/Frame

15

14

1

10

30

14

2

20

60

14

4

40

120

14

8

80

240

14

16

160

480

14

32

320

    • Frame length: 10 ms
    • SFN range: 0 to 1023
    • Subframe length: 1 ms
    • Subframe index per system frame: 0 to 9
    • Slot length: 14 symbols

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Slot Configuration (ECP)

60

12

4

40

1 frame = 10 ms = 10 subframes = 20 slots

1 subframe = 1 ms = 2 slots

1 slot = 0.5 ms = 14 symbols

SCS = 30 kHz

SCS = 120 kHz

1 frame = 10 ms = 10 subframes = 80 slots

1 subframe = 1 ms = 8 slots

1 slot = 0.125 ms = 14 symbols

The lengths of a radio frame and a subframe in NR are consistent with those in LTE. The number of slots in each subframe is determined by the subcarrier width.

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Slot Format and Type

X

    • Slot structure (section 4.3.2 of 3GPP TS 38.211)
    • Downlink, denoted as D, for downlink transmission
    • Flexible, denoted as X, for uplink or downlink transmission, GP, or reserved.
    • Uplink, denoted as U, for uplink transmission
    • Main slot types
    • Case 1: DL-only slot
    • Case 2: UL-only slot
    • Case 3: flexible-only slot
    • Case 4: mixed slot (at least one downlink slot and/or one uplink slot)

D

U

D

X

X

U

D

X

U

D

X

U

D

X

U

D

X

U

Case 1: DL-only slot

Case 2: UL-only slot

Case 3: flexible-only slot

    • Compared with LTE, NR has the following slot format features:
    • Flexibility: symbol-level uplink/downlink adaptation in NR and subframe-level in LTE
    • Diversity: More slots are supported in the NR system to cope with more scenarios and service types.
    • Examples of application scenarios of different slots:

Case 4-1

Case 4-2

Case 4-3

Case 4-4

Case 4-5

Slot Type

Application Scenario Example

Case 1

DL-heavy transmission

Case 2

UL-heavy transmission

Case 3

1. Forward compatibility: Resources are reserved for future services.

2. Adaptive adjustment of uplink and downlink resources: such as dynamic TDD

Case 4-1

1. Forward compatibility: Resources are reserved for future services.

2. Flexible data transmission start and end locations: such as unlicensed frequency bands and dynamic TDD

Case 4-2

Case 4-3

Downlink self-contained transmission

Case 4-4

Uplink self-contained transmission

Case 4-5

Mini-slot (seven symbols) for URLLC services

The number of uplink and downlink symbols in a slot can be flexibly configured. In Release 15, a mini-slot contains 2, 4, or 7 symbols for data scheduling in a short latency or a high frequency band scenario.

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Self-contained Slots/Subframes

    • The self-contained slot or subframe type is not defined in 3GPP specifications.
    • The self-contained slots or subframes discussed in the industry and literature are featured as follows:
    • One slot or subframe contains uplink part, downlink part, and GP.
    • Downlink self-contained slot or subframe: includes downlink data and corresponding HARQ feedback.

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    • Uplink self-contained slot or subframe: includes uplink scheduling information and uplink data.

D

U

UL control or SRS

D

U

DL control

ACK/NACK

UL grant

    • Self-contained slot/subframe design objectives
    • Faster downlink HARQ feedback and uplink data scheduling: reduced RTT
    • Shorter SRS transmission period: to cope with fast channel changes for improved MIMO performance
    • Problems in application
    • The small GP limits cell coverage.

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    • High requirements on UE hardware processing:
      • Release 15 defines two types of UE processing capabilities. The baseline capability is 10 to 13 symbols if the SCS is 30 kHz and self-contained transmission is not supported.
    • Frequent uplink/downlink switching increases the GP overhead.
    • In the downlink, only the retransmission latency can be reduced.
      • E2E latency depends on many factors, including the core network and air interface.
      • The latency on the air interface side is also limited by the uplink/downlink frame configuration, and the processing latency on the gNodeB and UE.

D

U

Downlink data processing time:

Part of the GP needs to be reserved for demodulating downlink data and generating ACK/NACK feedback.

Air interface round-trip latency

Self-contained subframes reduce the RTT latency on the RAN side but limits cell coverage. Therefore, high requirements are posed on hardware processing capabilities of UEs.

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Mini-slot: Support for the Length of 2, 4, or 7 Symbols in Release 15

  • Mini-slot: fewer than 14 symbols in the time domain
  • Basic scheduling units are classified into the following types:
    • Slot-based: The basic scheduling unit is slot, and the time-domain length is 14 symbols.
    • Non-slot-based: The basic scheduling unit is mini-slot. In Release 15, the time-domain length is 2, 4, or 7 symbols.
    • Application scenario
    • Short-latency scenario: reduces the scheduling waiting latency and transmission latency.
    • Unlicensed frequency band: Data can be transmitted immediately after listen before talk (LBT).
    • mmWave scenario: TDM is applied for different UEs in a slot.

1. URLLC for low latency

2. eMBB in unlicensed band

3. mmWave

Release 15 supports mini-slots with the length of 2, 4, or 7 symbols, which can be applied in short latency and mmWave scenarios.

PDCCH

PDSCH (mini-slot)

PDSCH (mini-slot)

Slot-based

Non-slot-based

PDSCH

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UL/DL Slot/Frame Configuration

    • Configuration: in line with section 11.1 of 3GPP TS 38.213
    • Layer 1: semi-static configuration through cell-specific RRC signaling
      • SIB1: UL-DL-configuration-common and UL-DL-configuration-common-Set2
      • Period: {0.5,0.625,1,1.25,2,2.5,5,10} ms, SCS dependent
    • Layer 2: semi-static configuration through UE-specific RRC signaling
      • Higher layer signaling: UL-DL-configuration-dedicated
      • Period: {0.5,0.625,1,1.25,2,2.5,5,10} ms, SCS dependent
    • Layer 3: dynamic configuration through UE-group SFI
      • DCI format 2_0
      • Period: {1,2,4,5,8,10,20} slots, SCS dependent
    • Layer 4: dynamic configuration through UE-specific DCI
      • DCI format 0, 1
    • Main characteristics: hierarchical configuration or separate configuration of each layer
    • Different from LTE, the NR system supports UE-specific configuration, which delivers high flexibility.
    • Support for symbol-level dynamic TDD

D

D

D

X

D

X

D

X

D

U

D

X

X

D

X

D

X

D

X

X

D

X

D

X

D

D

D

U

D

D

D

U

D

D

D

D

D

D

X

D

D

D

U

D

D

D

U

D

D

D

D

D

D

D

D

U

D

D

D

U

D

1. Cell-specific RRC configuration

2. UE-specific RRC configuration

3. SFI

4. DCI

    • Hierarchical configuration

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    • Separate layer configuration

D

D

D

D

D

D

D

D

U

D

D

D

U

D

Cell-specific RRC configuration/SFI

D

Frame configuration supports hierarchical configuration through RRC signaling and DCI to deliver symbol-level dynamic TDD and high flexibility.

If X slots/symbols are configured at the upper layer, D or U slots/symbols are also configured at the lower layer.

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UL/DL Slot/Frame Configuration: Cell-specific Semi-static Configuration

    • Single-period configuration: DDDSU

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    • Dual-period configuration: DDDSU DDSUU

X: DL/UL assignment periodicity

x1: full DL slots

y1: full UL slots

x2: DL symbols

y2: UL symbols

    • Cell-specific RRC signaling parameters
    • Parameter: SIB1
      • UL-DL-configuration-common: {X, x1, x2, y1, y2}
      • UL-DL-configuration-common-Set2: {Y, x3, x4, y3, y4}
    • X/Y: assignment period
      • {0.5, 0.625, 1, 1.25, 2, 2.5, 5, 10} ms
      • 0.625 ms is used only when the SCS is 120 kHz. 1.25 ms is used when the SCS is 60 kHz or larger. 2.5 ms is used when the SCS is 30 kHz or larger.
      • A single period or two periods can be configured.
    • x1/x3: number of downlink-only slots
      • {0,1,…, number of slots in the assignment period}
    • y1/y3: number of uplink-only slots
      • {0,1,…, number of slots in the assignment period}
    • x2/x4: number of downlink symbols following downlink-only slots
      • {0,1,…,13}
    • y2/y4: number of uplink symbols followed by uplink-only slots
      • {0,1,…,13}

D

D

D

D

D

U

D

D

D

D

U

D

D

D

X: DL/UL assignment periodicity

x1

y1

x2

y2

D

D

D

D

D

U

D

D

D

D

U

D

D

U

Y: DL/UL assignment periodicity

x3

y3

x4

y4

Cell-specific semi-persistent configuration supports limited configuration period options, and flexible static configuration of DL/UL resources are realized through RRC signaling.

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UL/DL Slot Configuration: Dynamic Configuration Through SFI

    • Slot Format Indicator (SFI) is transmitted over the group-common PDCCH.
    • SFI is identified by indexes in the following tables (reference: Table 4.3.2-3 in 3GPP TS 38.211).

The slot type can be notified to the UE through SFI over the PDCCH to dynamically set the slot/frame configuration.

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Comparison Among and Application of Different Frame Configuration Schemes

    • Features of the four configuration schemes

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    • Typical configuration schemes for commercial use:
    • Unified static network-wide frame configuration with the configuration period within the protocol-specified range: configured in cell-specific RRC signaling.
    • Unified static network-wide frame configuration with the configuration period outside the protocol-specified range: configured in cell-specific and UE-specific RRC signaling. SFI- and DCI-indicated configurations can be added.
    • Dynamic TDD: Cell-specific RRC+SFI/DCI configurations or direct SFI/DCI configurations

Configuration Scheme

Feature and Resource Configuration Priority

Cell-specific RRC signaling

Features: Cell-specific+static, or semi-persistent resource configuration

Resource configuration priority: Highest. Cell-specific-signaling-indicated D or U cannot be modified through other configurations.

UE-specific RRC signaling

Features: UE-specific+static, or semi-persistent resource configuration

Resource configuration priority: High. The X configurations indicated in cell-specific signaling can be further configured. UE-specific-signaling-indicated D or U cannot be modified through SFI/DCI.

SFI

Features: UE- or UE group-specific+periodic (1–20 slots) dynamic configuration

Resource configuration priority: Low. The X configurations indicated in cell-specific or UE-specific signaling can be further configured.

DCI

Features: UE-specific+slot-specific dynamic configuration

Resource configuration priority: Very low. The X configurations indicated in the cell-specific signaling/UE-specific signaling/SFI can be further configured.

Different configuration schemes are used to adapt to scenarios and requirements. The cell-specific RRC signaling configuration scheme delivers unified static network-wide frame configuration.

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Contents

2 Time-Domain Resources

1 Numerology

3 Frequency-Domain Resources: RB, RBG, REG, CCE, BWP

4 Space-Domain Resources

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Basic Concepts of Frequency-Domain Resources

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Resource Grid

Resource Block

Resource Element

 

In NR, an RB corresponds to 12 subcarriers (same as LTE) in the frequency domain. The frequency-domain width is related to SCS and is calculated using 2µ x 180 kHz.

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PRB/RBG and CCE: Frequency-domain Basic Scheduling Units

    • Basic scheduling unit for control channels: CCE
    • RE Group (REG): basic unit for control channel resource allocation
      • Frequency domain: 1 REG = 1 PRB (12 subcarriers)
      • Time domain: 1 OFDM symbol
    • Control Channel Element (CCE): basic scheduling unit for control channel resource allocation
      • Frequency domain: 1 CCE = 6 REGs = 6 PRBs
      • CCE aggregation level: 1, 2, 4, 8, 16
    • Basic scheduling unit for data channels: PRB/RBG
    • Physical RB (PRB): Indicates the physical resource block in the BWP.
      • Frequency domain: 12 subcarriers
    • Resource Block Group (RBG): a set of physical resource blocks
      • Frequency domain: The size depends on the number of RBs in the BWP.

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BWP Size (RBs)

RBG Size

Config 1

Config 2

1–36

2

4

37–72

4

8

73–144

8

16

145–275

16

16

In the frequency domain, the PRB or an RBG is a basic scheduling unit for data channels, and the CCE is a basic scheduling unit for control channels.

RB0

RB1

RB2

RB3

RB4

RB5

RB6

RB7

RB8

RB9

RB10

RB11

RB12

…

RBG0

RBG1

RBG2

…

RB

RBG

4 RBs

REG

DMRS

DMRS

DMRS

CCE

PRB

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Channel Bandwidth and Transmission Bandwidth

    • Channel bandwidth
    • Channel bandwidth supported by the FR1 frequency band (450 MHz to 6000 MHz): 5 MHz (minimum), 100 MHz (maximum)
    • Channel bandwidth supported by the FR2 frequency band (24 GHz to 52 GHz): 50 MHz (minimum), 400 MHz (maximum).
    • Maximum transmission bandwidth (maximum number of available RBs)
    • Determined by the channel bandwidth and data channel SCS.
    • Defined on the gNodeB side and UE side separately. For details about the protocol-configuration of the UE side, see the figure on the right.
    • Guard bandwidth
    • With F-OFDM, the guard bandwidth decreases to about 2% in NR (corresponding to 30 kHz SCS, 100 MHz channel bandwidth).

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Compared with the guard bandwidth (10%) in LTE, NR uses F-OFDM to reduce the guard bandwidth to about 2%.

Active RBs

Guard band

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Maximum Number of Available RBs and Spectrum Utilization

    • Spectrum utilization = Maximum transmission bandwidth/Channel bandwidth
    • Maximum transmission bandwidth on the gNodeB side: See Table 5.3.2-1 and 5.3.2-2 in 3GPP TS 38.104.

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    • Maximum transmission bandwidth on the UE side: See 3GPP TS 38.101-1 and TS 38.101-2.

SCS [kHz]

5

MHz

10

MHz

15

MHz

30

MHz

20 MHz

25 MHz

40 MHz

50 MHz

60 MHz

70

MHz

80 MHz

90

MHz

100 MHz

NRB and Spectrum Utilization (FR1:400 MHz to 6000 MHz)

15

25

52

79

[160]

106

133

216

270

N/A

N/A

N/A

N/A

N/A

90%

93.6%

94.8%

[96%]

95.4%

95.8%

97.2%

97.2%

\

\

\

\

\

30

11

24

38

[78]

51

65

106

133

162

[189]

217

[245]

273

79.2%

86.4%

91.2%

​

91.8%

93.6%

95.4%

95.8%

97.2%

​

97.7%

​

98.3%

60

N/A

11

18

[38]

24

31

51

65

79

[93]

107

[121]

135

​

79.2%

86.4%

​

86.4%

893%

91.8%

93.6%

94.8%

​

93.6%

​

97.2%

SCS [kHz]

50 MHz

100 MHz

200 MHz

400 MHz

NRB and Spectrum Utilization (FR2: 24 GHz to 52 GHz)

60

66

132

264

N/A

95%

95%

95%

\

120

32

66

132

264

92.2%

95%

95%

95%

Spectrum utilization is related to the channel bandwidth. The higher the bandwidth, the higher the spectral efficiency.

​

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RB Location Index and Indication

    • BWP is introduced to the NR system, which causes differences in the RB location index and indication from LTE.
    • Related concepts (section 4.4 of 3GPP TS 38.211)
    • RG: In the frequency domain, an RG includes all available RBs within the transmission bandwidth.
    • BWP: new concept introduced in the NR system. It refers to some RBs in the transmission bandwidth and is configured by the gNodeB.
    • Point A: basic reference point of the RG
      • Defined for the uplink, downlink, PCell, SCell, and SUL separately
      • Point A = Reference Location + Offset
      • For details about the reference location and offset for different reference points, see the figure on the right.
    • Common RB (CRB): index in the RG
      • The center of 0# subcarrier of CRB#0 is aligned with that of Point A.
    • Physical RB (PRB): index in the BWP
      • Index: 0 to
      • Relationship between PRB and CRB:

is the number of CRBs between the BWP start position and CRB#0.

Point A

Reference Location

Offset

PCell DL

(TDD/FDD)

SSB start location

UEs perform blind detection to obtain this information.

UEs are informed of this information through the RMSI.

Parameter:

PRB-index-DL-common

PCell UL (TDD)

Same as Point A for the PCell downlink

UEs are informed of this information through the RMSI.

Parameter:

PRB-index-UL-common

PCell UL (FDD)

Frequency-domain location of the ARFCN

UEs are informed of this information through the RMSI (SIB1).

UEs are informed of this information through the RMSI.

Parameter:

PRB-index-UL-common

SCell DL/UL

Frequency-domain location of the ARFCN

UEs are informed of this information through the SCell configuration message.

UEs are informed of this information through RRC signaling.

Parameter:

PRB-index-DL-Dedicated

PRB-index-UL-Dedicated

SUL

Frequency-domain location of the ARFCN

UEs are informed of this information through the SCell configuration message.

UEs are informed of this information through RRC signaling.

Parameter:

PRB-index-SUL-common

0

1

2

3

…

0

1

2

3

…

BWP

Offset

Reference

Location

Point A

0

0

CRB Index in RG

PRB Index in BWP

RG

Freq.

Point A is the basic reference point in the RG. CRB is the RB index in the RG, and PRB is the RB index in the BWP.

​

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BWP Definition and Application Scenarios

    • Definition and characteristics
    • The Bandwidth Part (BWP) is introduced in NR. It is a set of contiguous bandwidth resources configured by the gNodeB for UEs to achieve flexible transmission bandwidth configuration on the gNodeB side and UE side. Each BWP corresponds to a specific numerology.
    • BWP is specific to UEs (BWP configurations vary with UEs). UEs do not need to know the transmission bandwidth on the gNodeB side but only needs to support the configured BWP bandwidth.
    • Application scenarios
    • Scenario#1: UEs with a small bandwidth access a large-bandwidth network.
    • Scenario#2: UEs switch between small and large BWPs to save battery power.
    • Scenario#3: The numerology is unique for each BWP and service-specific.

BWP

BWP Bandwidth

Carrier Bandwidth

#1

BWP 2

#

2

BWP 1

Numerology 1

BWP1

Carrier Bandwidth

#

3

Numerology 2

BWP 2

Carrier Bandwidth

BWP is a set of contiguous bandwidth resources configured by the gNodeB for UEs. The application scenario examples are as follows: UEs supporting small bandwidths, power saving, and support for FDM on services of different numerologies.

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BWP Types

    • BWP types
    • Initial BWP: configured in the initial access phase. Signals and channels are transmitted in the initial BWP during initial access.
    • Dedicated BWP: configured for UEs in RRC_CONNECTED mode. A maximum of four dedicated BWPs can be configured for a UE.
    • Active BWP: one of the dedicated BWPs activated by a UE in RRC_CONNECTED mode. According to Release 15, a UE in RRC_CONNECTED mode can have only one active BWP at a given time.
    • Default BWP: It is one of the dedicated BWPs and is indicated by RRC signaling. After the BWP inactivity timer expires, the UE in RRC_CONNECTED mode switches to the default BWP.

Carrier Bandwidth

Initial BWP

Carrier Bandwidth

UE1 Active BWP

Random Access Procedure

RRC Connected Procedure

Carrier Bandwidth

default

Default

UE1 Dedicated BWPs

UE1

UE2

Default

UE2 Dedicated BWPs

UE2 Active BWP

UE2 Active BWP

UE1 Active BWP

UE2 BWP inactivity timer

PDCCH indicating downlink assignment

UE2 switches to the default BWP.

Active

Active

Switch

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Initial BWP Configuration

    • Initial DL BWP definition and configuration
    • Function: The PDSCH used to transmit RMSI, Msg2, and Msg4 must be transmitted in the initial active DL BWP.
    • Definition of the initial DL BWP: frequency-domain location and bandwidth of RMSI CORESET (control channel resource set) and a numerology corresponding to the RMSI
    • The frequency-domain location and bandwidth of the RMSI CORESET are indicated in the PBCH (MIB). The default bandwidth is {24,48,96} RBs.

​

​

​

​

​

​

​

​

    • Procedure for UEs to determine the initial BWP

Frequency

Time

SSB

CORESET

PDSCH

Frequency offset

Initial DL BWP

The frequency offset in PRB level which is between RMSI CORESET and SS/PBCH block is defined as the frequency difference from the lowest PRB of RMSI to the lowest PRB of SS/PBCH block.

    • Initial UL BWP definition and configuration
    • Function: The PUSCH used to transmit Msg3, PUCCH used to transmit Msg4 HARQ feedback, and PRACH resources during initial access must be transmitted in the initial active UL BWP.
    • The initial DL BWP and initial UL BWP are separately configured.
    • Numerology: same as that of Msg3 (configured in RMSI).
    • Frequency-domain location:
      • FDD (paired spectrum), SUL: configured in RMSI
      • TDD (unpaired spectrum): same as the center frequency band of the initial DL BWP
    • Bandwidth
      • Configured in RMSI and no default bandwidth option is available.

UEs search for the SSB to obtain the frequency-domain location of the SSB.

UEs demodulate the PBCH to obtain the frequency offset and bandwidth information of the RMSI CORESET and determine the initial DL BWP.

UEs receive the RMSI to obtain the frequency-domain location, bandwidth, and numerology information of the initial UL BWP.

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Dedicated BWP Configuration

    • Dedicated BWP configuration
    • Sent to UEs through RRC signaling
      • FDD (paired spectrum): Up to four downlink dedicated BWPs and four uplink dedicated BWPs can be configured.
      • TDD (unpaired spectrum): A total of four uplink/downlink BWP pairs can be configured.
      • SUL: 4 uplink dedicated BWPs
    • The smallest unit is one PRB. The dedicated BWP is equal to or smaller than the maximum bandwidth supported by a UE.
    • Each dedicated BWP can be configured with the following attributes through RRC signaling:
      • Numerology (SCS, CP type)
      • Bandwidth (a group of contiguous PRBs)
      • Frequency location (start location)
    • UEs can activate only one dedicated BWP at a given time as the active BWP.
    • UE Dedicated PRB Location
    • Dedicated BWP locations of all UEs in a cell are based on the same common reference point (Point A).
    • UEs determine the start location of the dedicated BWP based on the offset relative to Point A.
    • Based on the dedicated BWP bandwidth, UEs obtain the end location of the dedicated BWP.
    • UEs obtain the frequency-domain location and size of the dedicated BWP.

Cell Carrier Bandwidth

UE1 Active BWP

UE2 Active BWP

Point A

UE1 Offset

UE2 Offset

  • Offset: UEs can obtain the offset for each dedicated BWP from RRC signaling.

After a UE accesses the network, the dedicated BWP is configured through RRC signaling. A maximum of four dedicated BWPs can be configured.

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BWP Adaptation

    • BWP Adaptation
    • UEs in RRC_CONNECTED mode switch between dedicated BWPs (only one dedicated BWP can be activated at a given time).
    • BWP Adaptation is completed through switchovers and involves the following:
    • DCI
        • FDD: downlink: downlink DCI, uplink: uplink DCI
        • TDD: If the uplink or downlink DCI includes a switchover indication, BWP switchovers are performed in the uplink and downlink.
    • Timer mechanism
        • If the BWP inactivity timer expires, UEs switch to the default BWP (one of the dedicated BWPs).
        • Timer granularity: 1 ms for sub-6 GHz, 0.5 ms for mmWave
    • BWP Adaptation application scenarios
      • The BWP bandwidth changes: e.g. switching to the power saving state.
      • BWP location movement in the frequency domain: e.g. to increase scheduling flexibility.
      • The BWP numerology changes: e.g. to allow different services.

​

      • RF conversion time (defined in RAN4, sub-6 GHz)

​

UE BWP inactivity timer

PDCCH indicating downlink assignment

The UE switches to the default BWP.

Relationship Between BWP1 and BWP2

Intra-Band

Inter-Band

Same Center Frequency

Different Center Frequency

Time

≤ 20µs

50–200 µs

≤ 900 µs

In RRC connected mode, switching between BWPs is realized through DCI or timer mechanisms.

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Contents

2 Time-Domain Resources

1 Numerology

3 Frequency-Domain Resources

4 Space-Domain Resources: Layer, Antenna Port, QCL

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Codewords and Antenna Ports

    • Basic concepts
    • Codeword
      • Upper-layer service data on which channel coding applies.
      • Codewords uniquely identify data flow. By transmitting different data, MIMO implements spatial multiplexing. The number of codewords depends on the rank of the channel matrix.
    • Layer
      • The number of codewords is different from the number of transmit antennas. Therefore, codewords need to be mapped to transmit antenna.
    • Antenna port
      • Logical ports used for transmission. Antenna ports do not have a one-to-one relationship with physical antennas. They can be mapped to one or more physical antennas.
      • Antennas ports are defined based on reference signals.

​

​

​

​

Number of codewords ≤ Number of layers ≤ Number of antenna ports

    • Protocol-defined number of codewords
    • 1 to 4 layers: 1 codeword
    • 5 to 8 layers: 2 codewords
    • Protocol-defined number of layers
    • DL: up to eight layers for a single user and four layers for multiple users
    • UL: up to four layers for a single user or multiple users
    • Protocol-defined number of antenna ports

Channel/Signal

Maximum Number of Ports

Antenna Port#

UL

PUSCH with DMRS

8 or 12

{0,1,2,…,7} DMRS type 1

{0,1,2,…,11} DMRS type 2

PUCCH

1

{2000}

PRACH

1

{4000}

SRS

4

{1000,1001,1002,1003}

DL

PDSCH with DMRS

8 or 12

{1000, 1001,…,1007} DMRS type 1

{1000, 1001,…,1011} DMRS type 2

PDCCH

1

{2000}

CSI-RS

32

{3000,3001,3002,…,3031}

SSB

1

{4000}

Scrambling

Scrambling

Modulation

mapper

Modulation

mapper

Layer

mapper

Antenna

Port

mapper

RE mapper

RE mapper

OFDM signal

generation

OFDM signal

generation

Codewords

Layers

Antenna ports

In NR, a maximum of two codewords are supported. The maximum number of DMRS antenna ports is increased to 12.

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Thank You

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Copyright © 2018 Huawei Technologies Co., Ltd. All Rights Reserved.

The information in this document may contain predictive statements including, without limitation, statements regarding the future financial and operating results, future product portfolio, new technology, etc. There are a number of factors that could cause actual results and developments to differ materially from those expressed or implied in the predictive statements. Therefore, such information is provided for reference purpose only and constitutes neither an offer nor an acceptance. Huawei may change the information at any time without notice.