2.1 My 5G Presentation

5G NR Eng. Adel Mounir Mohamed WhatsApp:+201068537809 FB page: Telecom-Adel Mounir

5G Timeline

Source: KEYSIGHT

Source: 3GPP

Source: 3GPP

Source: 3GPP

Source: 3GPP

Source: 3GPP

Source: 3GPP

Source: 3GPP

5G Use Cases

Source: Cafetele

Source: 3GPP

Which is more important? • Evolved Mobile Broadband is important • • •

The main priority for some early operators Business models and revenue streams are well understood 5G Phase1 addresses very well this use case family

• ...but so are Ultra-Reliable Low-Latency Communications and Massive Machine Type Communications • •

URLLC features are contained in 5G Phase 1 URLLC and mMTC to be fully covered in 5G Phase 2

Source: 3GPP

Source: Qualcomm

Source: ITU

Source: Coursera

Source: Coursera

5G Use Cases & Related Examples

Source: NGMN

1. Broadband Access in Dense Areas - Pervasive Video - Smart Office - Operator Cloud Services - HD Video/Photo Sharing in Stadium/Open-Air Gathering

2. Broadband Access Everywhere - 50+ Mbps Everywhere - Ultra-low Cost Networks

3. Higher User Mobility - High Speed Train - Moving Hot Spots - 3D Connectivity

4. Massive Internet of Things (mIoT) - Smart Wearables - Sensor Networks - Mobile Video Surveillance

5. Extreme Real-Time Communications - Tactile Internet

6. Lifeline Communication - Natural Disaster

7. Ultra-Reliable Communications - Automated Traffic Control & Driving - Collaborative Robots - eHealth - Drones - Public Safety

8. Broadcast-Like Services - News and Information - Local Broadcast-like Services - Regional Broadcast-like Services - National Broadcast-like Services

5G Deployment Options

Source: Rohde & Shwarz

EN-DC Concept & Radio Bearers

Source: Ericsson

Source: MPIRICAL

EN-DC Bearers

Source: Rohde & Shwarz

Source: MPRICAL

Source: Ericsson

Source: Ericsson

Source: KEYSIGHT

Source: MediaTek

Source: KEYSIGHT

Source: KEYSIGHT

Source: KEYSIGHT

Source: KEYSIGHT

Option 2 and Option 5 for SA deployment

Source: Rohde & Shwarz

Source: ETSI

5G Network Architecture

Source: Apis

Source: Apis

Source: KEYSIGHT

Source: KEYSIGHT

Source: KEYSIGHT

Source: KEYSIGHT

Source: KEYSIGHT

NSSF Functions:

Source: Apis

Source: Huawei

Source: Apis

NEF Functions:

NRF Functions:

5G Spectrum

FR1 in 5G

FR2 in 5G

Main 5G spectrum options in different markets globally

Source: Huawei

SUL and SDL Supplementary downlink or Uplink allow the bonding of unpaired spectrum with FDD or TDD bands, to significantly enhance NR network capacity and users experience. This provides an efficient way of using spectrum because consumption rich content and other data heavy applications is asymmetric. Additionally, to improve UL coverage for high frequency scenarios, Supplementary Uplink (SUL) can be configured as shown the slide. With SUL, the UE is configured with 2 uplinks for one Downlink of the same cell. In conjunction with a UL/DL carrier pair (FDD band) or a bidirectional carrier (TDD band), a UE may be configured with additional, supplemental uplink. Supplemental uplink differs from the aggregated uplink in that the UE may be scheduled to transmit either on the supplemental uplink or on the uplink of the carrier being supplemented, but not on both at the same time.

LTE + NR

NOMA

Numerologies (adjustable SCS) supported by 3GPP Release 15 (TS 38.211) with SCS identified by the parameter µ.

•

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

SCS: Application Scenarios and Suggestions •

Impact of SCS on coverage, latency, mobility, and phase noise

SCS application suggestions for different frequency bands (eMBB

–

service data channel):

Coverage: The smaller the SCS, the longer the symbol length/CP, and the

better the coverage. –

SCS (kHz)

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.

Coverage

3.5 GHz

Mobility

Latency –

Phase noise: The larger the SCS, the smaller the impact of phase noise, Coverage

and the better the performance.

28 GHz

Mobility Phase Noise Latency

15

30

60

120

good

240

bad

bad good

bad

good

good

bad

bad

good

bad

good

bad

good

Source: Huawei

Mapping Between SCS and Symbol Length

Parameter/Numerology (µ)

0

1

2

3

4

SCS (kHz): SCS = 15 x 2^(µ)

15

30

60

120

240

OFDM Symbol Duration (us): T_data = 1/SCS

66.67

33.33

16.67

8.33

4.17

CP Duration (µs): T_cp = 144/2048*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

SCS = 30 kHz

SCS = 15 kHz

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

T_slot = 1 ms (14 symbols) CP

…

data

T_symbol T_slot = 0.5 ms (14 symbols)

… T_symbol T_slot = 0.125 ms (14 symbols)

SCS = 60 kHz



…

T_symbol

NR Cyclic Prefix (CP) 

CP function: – To eliminate inter-channel interference (ICI) caused by multipath propagation. Symbol Period T(s)

Attitude

Symbol N

Symbol N+1 Cyclic Prefix

Bit Period T(b)

One OFDM symbol

T(g)

Symbol Period T(s)

time



NR CP design principle: – Same overhead as that in LTE, ensuring aligned symbols btw different SCS values and the reference numerology (15 kHz).

NR Concepts of Frequency-Domain Resources  Resource Grid (RG) – –

Resource group at the physical layer, defined for the uplink and downlink (for a given numerology) Time domain: 1 subframe, frequency domain: available RB resources within the transmission bandwidth

Resource Grid One subframe

subfram , Nsymb OFDM symbols

 Resource Element (RE) – –

Smallest unit of physical-layer resources Time domain: 1 OFDM symbol, frequency domain: 1 subcarrier

max, RB k  NRB, x Nsc 1

 Resource Block Group (RBG) – –

Basic scheduling unit for data channel resource allocation (type 0 resource allocation) and reduced control channel overheads Frequency domain: {2, 4, 8, 16} RBs

 Resource Element Group (REG) – –

Basic unit involved in control channel resource allocation Time domain: 1 OFDM symbol, frequency domain: 12 subcarriers (1 PRB)

 Control Channel Element (CCE) – – –

N scRB subcarriers

–

Basic frequency-domain scheduling unit involved in data channel resource allocation (type 1 resource allocation) Frequency domain: 12 contiguous subcarriers

Resource element

(k , l )

Resource block

–

 N RB N scRB subcarriers

 Resource Block (RB)

Basic scheduling unit involved in control channel resource allocation Frequency domain: 1 CCE = 6 REGs = 6 PRBs CCE aggregation level: 1, 2, 4, 8, 16

k 0

l 0

l  14  2   1

Transmission Bandwidth and Spectrum Utilization Transmission bandwidth: depends on the channel bandwidth and data channel SCS. 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. SCS (kHz) 15

30 60

5 MHz

10 MHz

15 MHz

30 MHz

25 90% 11 79.2% N/A

52 93.6% 24 86.4% 11 79.2%

79 94.8% 38 91.2% 18 86.4%

[160] [78]

[38]

20 MHz

25 MHz

40 MHz

50 MHz

60 MHz

NRB and Spectrum Utilization (FR1: 400 MHz to 6000 MHz) 106 133 216 270 N/A 95.4% 95.8% 97.2% 97.2% \ 51 65 106 133 162 91.8% 93.6% 95.4% 95.8% 97.2% 24 31 51 65 79 86.4% 893% 91.8% 93.6% 94.8%

70 MHz N/A \ [189] [93]

80 MHz N/A \ 217 97.7% 107 93.6%

90 MHz N/A \ [245] [121]

100 MHz N/A \ 273 98.3% 135 97.2%

Channel Bandwidth [MHz] Transmission Bandwidth Configuration NRB [RB]

120

100 MHz

200 MHz

400 MHz

NRB and Spectrum Utilization (FR2: 24 GHz to 52 GHz) 66 95% 32 92.2%

132 95% 66 95%

264 95% 132 95%

N/A \ 264 95%

Transmission Bandwidth [RB] Resource Block

60

50 MHz

Channel Edge

SCS (kHz)

Channel Edge



f Active Resource Blocks Guardband, can be asymmetric

– Maximum transmission bandwidth on the UE side: See 3GPP TS 38.101-1 and TS 38.101-2. – The number of RBs in the 30 MHz bandwidth is to be determined. The 70 MHz and 90 MHz bandwidths are not supported. Other values are the same as those on the gNodeB side.

Slot and Mini-Slot

Each subframe consists of an OFDM sub-carrier spacing dependent number of slots. Each slot consists of 14 OFDM symbols. The Slot is transmitted within a transmission time interval (TTI). Different numerologies lead to different slot lengths, ranging from 1 ms at 15 kHz sub-carrier spacing to 0.125 ms at 120 kHz sub-carrier spacing, enabling shorter TTIs. The slot is the basic transmission unit at which most physical channels and signals repeat; however, slots can be complemented by mini-slot-based transmissions (referred to as Type B scheduling in NR) to provide shorter and more agile transmission units than slots.

Slot and Mini-Slot

A mini-slot can start at any OFDM symbol and can have a variable length; mini-slot lengths of 2, 4, or 7 symbols have been defined in the standard so far. This provides fast transmission opportunities, for example, URLLC traffic that is not restricted by slot boundaries. Thus, mini-slots provide a viable solution to low-latency transmissions irrespective of sub-carrier spacing. In the example of resource allocation shown on the slide, you can see a Mini-slot of 4 OFDM symbols allocated to URLLC User Equipment : one symbol in red to carry the PDCCH and 3 symbols (orange) for data traffic transmission.

1. URLLC for low latency

Mini-Slot application scenarios 2. eMBB in unlicensed band

–

– 3. mmWave

–

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.

Source: Huawei

Source: Qualcomm

Source: Qualcomm

Source: Qualcomm

Source: Qualcomm

Source: Keysight

LTE TDD frame

5G Static TDD

Source: Rodhe & Shwarz

5G Static TDD

Source: Rodhe & Shwarz

5G Static TDD

Source: Rodhe & Shwarz

5G Semi-Static TDD

Source: Rodhe & Shwarz

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

D

D

D

U D

D

D

D

D

U D

y1: full UL slots

x1: full DL slots

y2: UL symbols x2: DL symbols

 Dual-period configuration: DDDSU DDSUU X: DL/UL assignment periodicity

Y: DL/UL assignment periodicity

D

D

D

D

U D

D

D

D

U D

U D

{0,1,…,13}

– y2/y4: number of uplink symbols followed by uplink-only slots –

D

{0,1,…, number of slots in the assignment period}

– x2/x4: number of downlink symbols following downlink-only slots –

X: DL/UL assignment periodicity

{0,1,…, number of slots in the assignment period}

– y1/y3: number of uplink-only slots –

 Single-period configuration: DDDSU

y1

x1

{0,1,…,13}

y3

x3

y2 x2

y4 x4

Source: Huawei

5G Dynamic TDD

Source: Rodhe & Shwarz

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.

Source: Nokia

Example

Source: Rodhe & Shwarz

Source: Rodhe & Shwarz

Source: Rodhe & Shwarz

Bandwidth Part (BWP)



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 1

#2

#1 BWP

BWP 2 BWP Bandwidth Carrier Bandwidth

Carrier Bandwidth

#3 Numerology 1

Numerology 2

BWP1

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.

BWP Use Cases

Source: Rodhe & Shwarz

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. A fter the BWP inactivity timer expires, the UE

in RRC_CONNECTED mode switches to the default BWP. Random Access Procedure

RRC Connected Procedure Default

Default

UE1

UE2

PDCCH indicating downlink assignment UE2 BWP inactivity timer

UE1

UE2

Dedicated BWPs

Dedicated BWPs

UE2 switches to the default BWP.

Active

Active

Switch

Initial BWP default

Carrier Bandwidth UE1 Active BWP

UE2 Active BWP

Carrier Bandwidth

UE1 Active BWP

UE2 Active BWP

Carrier Bandwidth

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 PDCCH indicating downlink assignment UE BWP inactivity timer

The UE switches to the default BWP.

 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) Intra-Band

Relationship Between BWP1 and BWP2

Same Center Frequency

Different Center Frequency

Inter-Band

Time

≤ 20µs

50–200 µs

≤ 900 µs

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

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.

 Initial UL BWP definition and configuration –

– – –

CORESET PDSCH

SSB

Frequency – Initial DL BWP

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.

Frequency offset

Time 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.

 Procedure for UEs to determine the initial BWP UEs search for the SSB to obtain the frequencydomain 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.

Dedicated BWP Configuration  Dedicated BWP configuration

 UE Dedicated PRB Location

– Sent to UEs through RRC signaling

– 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.

– 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:

UE2 Offset

UE1 Offset

– 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.

UE1 Active BWP Point A

•

UE2 Active BWP

Cell Carrier Bandwidth

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.

SSS PSS = 0,1,2 SSS = 0 – 335 (Total 336) PCI = 3*SSS + PSS Start PCI = 3*0+0 = 0 Last PCI = 3*335+2 = 1007 PCI range = 0 – 1007 (Total 1008 PCI)

PSS

PSS/SSS: Time-domain and Frequency-domain Resources  One or more beams are used to repeatedly receive synchronization signals and signals on the broadcast channel. This contributes a lot in making NR different from LTE.  To support beam scanning, the PSS/SSS and the PBCH in NR together form an SS/PBCH block which occupies 4 consecutive symbols in the time domain and 20 RBs in the frequency domain. Within an SS/PBCH block, the PBCH is mapped to symbols 1 and 3 and occupies some REs in symbol 2, and the PSS and SSS are mapped to symbols 0 and 2, respectively.

SSS

PSS

 Within an SS/PBCH block, the PSS/SSS and the PBCH use the same beam transmission mode. PBC H

Note: v = Cell ID%4. This aims to stagger DMRS pilot positions to avoid interference.

SSB Starting symbol detection

Example

SS/PBCH: Transmission Mechanism

n = 0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18

SS/PBCH Block: Maximum (Beam) Quantity L and Time Domain Pattern 

Maximum (beam) quantity L –

At most, 4 SS/PBCH blocks, 8 SS/PBCH blocks, and 64 SS/PBCH blocks can be defined for sub-3 GHz, sub-3 GHz to sub-6 GHz, and above-6 GHz, respectively.

–

Each SS/PBCH block has a unique number (SSB index). For low frequencies, this number is directly obtained from the PBCH pilot. For high frequencies, the 3 least significant bits and the 3 most significant bits of this number are obtained from the PBCH

pilot and the MIB, respectively. –

When the actual number of beams transmitted in a cell is less than the maximum number of SS/PBCH blocks specified by 3GPP, SIB1 or RRC signaling can be used to indicate which positions in the radio frame are not occupied by SS/PBCH blocks and can be used for PDSCH data transmission.

–



SS/PBCH block broadcast period is sent to UEs through SIB1 and can be 5 ms, 10 ms, 20 ms, 40 ms, 80 ms, or 160 ms.

SS/PBCH pattern and position within the slot

Subcarrier Spacing 15 kHz

First Slot

Second Slot

Third Slot

Fourth Slot

30 kHz 120 kHz 240 kHz

When a 30 kHz subcarrier spacing is used, CASE C is primary.

3GPP has defined the SS/PBCH block position in the time domain. The maximum number of SS/PBCH blocks and the time-domain pattern varies with the subcarrier spacing.

SS/PBCH Subcarrier Spacing 

The PBCH and the PSS/SSS use the same subcarrier spacing. Each frequency band has a defined subcarrier spacing by default. NR Operating Band n1 n2 n3 800 MHz

n5

2.6 GHz

n7 n8 n20 n28 n38 n41 n50 n51 n66

3.5 GHz

n70 n71 n74 n75 n76 n77 n78 n79

SS Block SCS 15 kHz 15 kHz 15 kHz 15 kHz 30 kHz 15 kHz 15 kHz 15 kHz 15 kHz 15 kHz 15 kHz 30 kHz 15 kHz 15 kHz 15 kHz 30 kHz 15 kHz 15 kHz 15 kHz 15 kHz 15 kHz 30 kHz 30 kHz 30 kHz

SS Block Pattern Case A Case A Case A Case A Case B Case A Case A Case A Case A Case A Case A Case C Case A Case A Case A Case B Case A Case A Case A Case A Case A Case C Case C Case C

NR Operating Band n257 n258

n260

SS Block SCS

SS Block Pattern1

120 kHz 240 kHz 120 kHz 240 kHz 120 kHz 240 kHz

Case D Case E Case D Case E Case D Case E

Note: If a frequency band supports two subcarrier spacings, the UE needs to alternate blind detection between the two subcarrier spacings.

 The 30 KHz subcarrier spacing is used for the C-band.

The PBCH and the PSS/SSS use the same subcarrier spacing, with a default one specified by RAN4 for each frequency band. 30 kHz is used by default for the C-band.

DMRS for PBCH Each RB contains 3 REs for DMRS pilot transmission on the PBCH. To avoid inter-cell PBCH DMRS interference, PBCH DMRSs are staggered in the frequency domain on a Physical cell ID basis. PCImod4 = 0

PCImod4 = 1

PCImod4= 2

PCImod4= 3

PBCH DMRS

PDCCH 

Main functions Transmits the downlink control information from Layer 1/Layer 2, including:



–

Downlink scheduling information (DL assignments) for the UE to receive PDSCH data

–

Uplink scheduling information (UL grants) for the UE to send PUSCH data

–

Slot Format Indicator (SFI), Pre-emption Indicator (PI), and power control commands to assist the UE in receiving and sending data

Features –

Downlink Control Information (DCI) is transmitted on the PDCCH. Different RNTIs are used by DCIs with different contents for CRC scrambling.

–

UEs perform PDCCH demodulation through blind detection.

–

A cell can simultaneously schedule multiple UEs in the uplink and downlink. To be specific, it can send multiple scheduling information pieces in each timeslot. Each scheduling information piece is transmitted on an independent PDCCH. This means that a cell can simultaneously set up multiple PDCCHs in one timeslot.

The PDCCH is used to transmit the downlink control information from Layer 1/Layer 2. DCIs with different contents are scrambled by using different RNTIs.

PDCCH: Differences Between NR and LTE  Major differences –

NR has only one downlink control channel (PDCCH) while LTE has the PCFICH and the PHICH.

–

The PCFICH (indicates the number of PDCCH symbols in LTE) is no longer used. In NR, the number of PDCCH symbols in the time domain is notified to the UE through higher layer signaling and DCI.

–

The PHICH (transmits the ACK/NACK messages on the PUSCH in LTE) is no longer used. In NR, the ACK/NACK

messages on the PUSCH are directly carried on the PDCCH and notified to the UE. –

NR supports resource sharing between the PDCCH and the PDSCH through FDM. –

–

Available PDCCH symbol resources can be used by the PDSCH, improving resource usage.

On the PDCCH, BF transmission is supported to enhance control channel coverage.

Compared with LTE, NR simplifies the control channel and allows the PDCCH and the PDSCH to share resources through FDM.

PDCCH: Time-Frequency Resource Configuration 

Control Channel Element (CCE) – –



Aggregation Level

Number of CCEs

The CCE is the minimum resource unit for PDCCH transmission. One CCE contains six

1

1

REGs, with each REG corresponding an RB.

2

2

The aggregation level indicates the number of consecutive CCEs occupied by a PDCCH.

4

4

3GPP Release 15 supports CCE aggregation level {1, 2, 4, 8, 16}. The gNodeB determines

8

8

the aggregation level used by a PDCCH based on factors such as the channel quality.

16

16

Control-resource set (CORESET) –

The CORESET indicates the number of symbols and RBs occupied by a PDCCH. A CORESET RBs in the CORESET consists of {1, 2, 3} symbols in the time domain and 𝑁RB

RE

frequency domain. The specific number of symbols and RBs are configured by higher layer parameters. –

The REG in the CORESET is numbered from 0 according to the time domain priority. The REG in the first OFDM symbol with the smallest RB number is numbered 0.



CORESET 2 Search space 2

REG

Search space –

The UE listens to the PDCCH candidates set in the non-DRX timeslot, and the set is referred to as the search space of the UE. The PDCCH search space on which the UE performs blind detection is associated with a specific CORESET to indicate the period and resource information of the CORESET.

CCE

CORESET 1 Search space 1

DMRS

PDCCH Type 

PDCCHs fall into 3 types according to the application scenarios and functions. – Common PDCCH: Used for transmitting common messages (such as system and paging messages) and scheduling data (Msg2/Msg4) before RRC connection to the UE is established. – Group Common PDCCH: Used for scheduling the SFI (slot format) and the PI (resource pre-emption) for a UE group. – UE-specific PDCCH: Used for scheduling the UE-level data and power control information.

PDCCHs fall into: Common PDCCH, Group Common PDCCH, and UE-specific PDCCH.

PDCCH: DCI Format 

Contents transmitted on the PDCCH: DCI



DCI format: 8 formats of 3 types according to the carried contents and functions (See section 7.3.1 in 3GPP TS 38.212 for detailed DCI format descriptions. The number of bits has not been determined yet and is subject to protocol updates .)

Category

DCI Format

Description

Content

Format 0_0

Fallback DCI. Indicates PUSCH scheduling and is used upon waveform change or status change.

Resource assignment, frequency hopping flag, MCS, HARQ process number, TPC command

Format 0_1

Indicates PUSCH scheduling.

Carrier/BWP indicator, resource assignment, frequency hopping flag, MCS, HARQ process number, SRS resource indicator, precoding information, antenna port, SRI/CSI request, CBG transmission information, TPC command, waveform indicator

Format 1_0

Fallback DCI. Indicates PDSCH scheduling and is used upon public message scheduling (such as paging and RMSI scheduling) and status change (such as BWP switch).

Resource assignment, MCS, HARQ process number, TPC command, PUCCH resource indicator

Format 1_1

Indicates PDSCH scheduling.

Carrier/BWP indicator, resource assignment, MCS, HARQ process number, TPC command, CSI-RS trigger, PUCCH resource indicator, precoding information, antenna port, CBG transmission information

Format 2_0

Indicates the SFI (slot format).

SFI

Format 2_1

Notifies the PRBs and the OFDM symbols where a UE may assume no transmission is intended for the UE. Indicates which PRBs and OFDM symbols to which UE data is not mapped.

PI

Format 2_2

Indicates power control commands for PUSCH and PUCCH.

PUCCH and PUSCH TPC command

Format 2_3

Indicates power control commands for SRS transmission.

SRS TPC command

DCI formats for scheduling of PUSCH

DCI formats for scheduling of PDSCH

DCI formats for other purposes

DCI: 3 types and 8 formats based on the contents carried

PDCCH: DCI Format Identification  RNTIs used by DCIs and corresponding DCI contents Category DCI formats for scheduling of PUSCH

DCI formats for scheduling of PDSCH

DCI formats for other purposes

DCI Format

RNTI and DCI Content

Format 0_0

C-RNTI: PUSCH scheduling TC-RNTI: Msg3 scheduling during random access

Format 0_1

C-RNTI: PUSCH scheduling

Format 1_0

C-RNTI: PDSCH scheduling P-RNTI: Page message scheduling SI-RNTI: SI scheduling RA-RNTI: RAR scheduling during random access TC-RNTI: Msg4 scheduling during random access

Format 1_1

C-RNTI: PDSCH scheduling

Format 2_0

SFI-RNTI: Slot format

Format 2_1

INT-RNTI: Pre-emption resource

Format 2_2

TPC-PUSCH-RNTI: PUSCH TPC command TPC-PUCCH-RNTI: PUCCH TPC command

Format 2_3

TPC-SRS-RNTI: SRS TPC command

PDCCHs containing different contents are scrambled by using different RNTIs.

DMRS for PDCCH 

Main functions –

The PDCCH and its DMRSs support only single-port transmission.

–

The DMRS scrambling code ID can be configured at the UE level (by using higher layer signaling) or configured at the cell level (default).

–

Each REG has three DMRS REs whose frequency-domain positions are fixed.

REG



RE resource mapping –

Each REG has three DMRS REs, which are located on subcarriers #1,

DMRS

CCE DMRS

PRB

#5, and #9. DMRS

The DMRS for PDCCH supports single-port transmission. The scrambling code ID can be configured at the UE or cell level.

PT-RS for PDSCH: Background Phase rotation of demodulation constellation diagram

 PT-RS: Phase-tracking reference signal This is a reference signal newly introduced in NR, which is used to trace the changes of phase noise and is mainly used in high frequency bands.

 Phase noise – Generation: A random change of the phase of the system output signal caused by the noise (random white noise, flicker noise) of the radio-frequency components.

– Frequency band difference: There is little impact on the sub-6 GHz band. In the above-6 GHz frequency band, the phase noise response greatly increases due to the increase of frequency multiplication times of the reference clock and the technical manufacturing and power consumption of the component.

 Solutions – The PT-RS and the phase estimation compensation algorithm are introduced.

PSD: dBC/Hz

– Impact: The SNR or EVM in the receive segment deteriorates, causing a large number of bit errors. As a result, the use of high-order constellation modulation is restricted and the system capacity is severely affected.

20 dB deterioration

– Increase the subcarrier spacing to reduce the ICI and ISI caused by phase noise. – Improve the quality of the local oscillator to reduce the phase noise.

Frequency (Unit: MHz)

The phase noise causes the demodulation constellation diagram to rotate, limits the use of high-order constellation modulation, and has even greater impacts in high-frequency band scenarios.

CSI-RS: Main Functions 

The main functions and types of the CSI-RS are as follows: Function

Description

CSI obtaining

Used for channel state information (CSI) measurement. The UE reports the following contents: CQI, PMI, rank indicator (RI), and layer indicator (LI).

Beam management

Used for beam measurement. The UE reports the following contents: L1-RSRP and CSI-RS resource indicator (CRI).

Time-frequency offset tracing

Used for precise time-frequency offset tracing.

RRM/RLM

Used for RRM/RLM. The UE reports the following contents: CSI-RSRP, CSIRSRQ, and CSI-SINR.

CSI-RS functions in NR: channel quality measurement, beam management, time-frequency offset tracing, and RRM/RLM

PUCCH: Overview  Main functions – Transmits L1/L2 uplink control information (UCI) for downlink and uplink data. – The L1/L2 UCI includes: – – –

Scheduling request (SR): Used for UL-SCH resource requests. HARQ ACK/NACK: Used for HARQ feedback of data transmitted on the PDSCH. CSI: Including CQI, PMI, RI, LI, and CRI.

– Compared with downlink control information (DCI), UCI has the following features: – –

UCI carries a small amount of information (only these unknown to the gNodeB). The DCI can be transmitted only in the PDCCH, and the UCI can be transmitted in the PUCCH or the PUSCH.

 Features – Compared with LTE, the short PUCCH (1 to 2 symbols) is added in NR, which can be used for quick feedback in the short delay scenario (self-contained transmission). – The number of long PUCCH symbols is enhanced (4 to 14 symbols) to support PUCCH transmission in different slot formats. – In 3GPP Release 15, the concurrency of the PUCCH and PUSCH of the same user is not supported. For example, if the UCI and the UL data coexist, UCI is transmitted on the PUSCH (the UCI is associated with the channel). – The uplink HARQ supports asynchronous adaptation, and the ACK/NACK transmission time can be flexibly determined by the scheduler.

Compared with LTE, NR adds the short PUCCH for fast feedback in short delay scenario.

PUCCH: Basic Format Long duration PUCCH, 4–14 symbols

Short PUCCH duration, 1/2 symbols

1 symbol

1 slot

2 symbols

PDSCH

PDSCH

PUCCH

RS

PUCCH PUSCH

RS

SRS SRS refers to uplink sounding signal. In this version, a UE sends an SRS within the activated bandwidth part (BWP). The gNodeB receives and processes the SRS, and measures the signal to interference plus noise ratio (SINR), reference signal received power (RSRP), and PMI of the SRS.

5G Air Interface Protocol Stack

5G Air Interface Protocol Stack

Physical Layer

Massive MIMO and Beamforming

Evolution from MIMO to Massive MIMO 4 Layers

2 Layers

16+ Layers

Massive MIMO

Downlink Beamforming - Beamforming Implementation 



Beamforming relies on the interference principles. The arcs indicate carrier signal peaks. When two wave peaks intersect, the signal strength increases. When a wave peak intersects with a wave bottom, the signal strength decreases.  When beamforming is not used, the beam shape and lobe positions are fixed. When a UE resides between two beams at the cell edge, the signals are weak.  When beamforming is enabled, gNodeBs impose weighting on and adjust the transmit power and phase of signals to be transmitted through each antenna element. This way, the beam shape changes and the main lobe is directed at target UEs, improving the signal strength. A beam generated using SRS- or PMI-based weighting is referred to as a dynamic beam. Control channels and broadcast channels use predefined weighting values to generate discrete static beams.

Downlink Beamforming - Weight Calculation 

Weight calculation: The gNodeBs calculate a weight vector based on downlink channel characteristics to adjust the shape and

directionality of beams. 

Classification: Weight calculation is classified into control channel (SSB/PDCCH/CSIRS) DFT static weight calculation and PDSCH

dynamic weight calculation. 

Calculation of the static weight of the control channel DFT: Predefined and static invariant weights are obtained from the weight file.



There are two methods for calculating the PDSCH dynamic weight: 

SRS: Based on channel reciprocity, gNodeBs estimate

the downlink channel characteristics using SRSs received from the UEs to obtain weighting values. This method is suitable for UEs in or near the cell center. 

PMI: gNodeBs select an optimal weighting value based

on PMIs received from the UEs. This method is suitable for UEs at the cell edge.

Data Flow Processing Codewords

Layers Modulation mapper

Scrambling

Modulation mapper

Scrambling

Codeword: Corresponds to transport block, that is, the original data block to be transmitted at the physical layer. 5G can transmit two independent codewords at the same time.

Layer mapper

Antenna ports Precoding & Antenna Port mapper

Layer mapping: A mapping relationship that is established between the encoded data stream and the spatial multiplexing data stream layer through a layer mapping process. Maximum number of spatial multiplexing layers ≤ Min (Number of TX antennas, Number of RX antennas)

Resource Element mapper

OFDM signal generation

Resource Element mapper

OFDM signal generation

The function of precoding is to convert an antenna domain into a beam domain for processing (by using known spatial channel information, that is, weighting).

Number of Codewords

Number of Layers

Mapping

1

1~4

Codeword 1: layer 1-4

2

5

Codeword 1: layer 1-2 Codeword 2: layer 3-5

2

6

Codeword 1: layer 1-3 Codeword 2: layer 4-6

2

7

Codeword 1: layer 1-3 Codeword 2: layer 4-7

2

8

Codeword 1: layer 1-4 Codeword 2: layer 5-8

Uplink Receive Diversity 

Concept: Uplink receive diversity enables gNodeBs to enhance reception by taking advantage of space diversity (diversity gains) and coherent reception (array gains) to receive UE signals over multiple antennas.



Procedure: 

A gNodeB receives SRSs from a UE over multiple antennas, estimates the uplink channel characteristics, and then sends

downlink control information (DCI) to the UE, notifying the UE of the optimal PMI/rank value. 

The UE uses that PMI value to precode physical uplink shared channel (PUSCH) data and transmits it to the gNodeB.



The gNodeB uses multiple antennas to receive the PUSCH data, improving the signal-to-noise ratio (SNR) and stability of received signals, and increasing uplink user throughput.

Diversity gains: SNR becomes more stable after combination.

Array gains: Coherent reception improves the SNR.

Network Impact of Massive MIMO •

Benefits: – Improved cell coverage. • Downlink Adaptive Selection Between PMI and SRS increases coverage performance by 1 dB and the downlink throughput of cell edge UEs by 5%. – Improved customer experience. • Downlink: When the signal-to-noise ratio (SNR) is satisfactory (MCS index of 27 with 256QAM), the spatial channels are independent of each other, and the number of receive antennas is greater than or equal to 8, the UE supports simultaneous data transmission of 8 layers in the downlink. In this case, the single UE downlink peak rate is theoretically 8 times that of the single-layer downlink peak rate. • Uplink: When the SNR is satisfactory (MCS index of 28 with 64QAM), the spatial channels are independent of each other, and the number of receive antennas is greater than or equal to 4, the UE supports simultaneous data transmission of 4 layers in the uplink. In this case, the single UE uplink peak rate is theoretically 4 times that of the single-layer uplink peak rate. – The system capacity is increased. • Improved system capacity: The more number of layers, the higher the gains. Assume that N layers are used for spatial multiplexing of full-buffer services. In this case, the cell throughput increases to N x 100% theoretically.

Source: Comba

5G Massive MIMO

3D Beamforming / FD-MIMO