5G RAN
Standards Compliance Feature Parameter Description
Summary
• Introduction
• 5G vs. 4G
• LDPC
• Polar Codes
• Basic Numerology
• Self-contained Frame Structure
• Slot Configuration
• F-OFDM
Introduction – 5G Wireless Inventions
Introduction (1)
• Scalable OFDM numerology
• 2n scaling of subcarrier spacing
• Support diverse spectrum
bands/types and deployment
models
• I.E.: able to operate in mmWave bands
that have wider channel widths
• Flexible self-contained slot
structure
• Ability to independently decode
slots and avoid static timing
relationships across slots
Introduction (2)
• Advanced ME-LDPC and CA-Polar channel
coding
• Low-density parity check (LDPC) codes, and
advanced Multi-Edge LDPC (ME-LDPC) codes
have advantages from both complexity and
implementation standpoints when scaling to
very high throughputs and larger block lengths
• Polar channel coding as the coding scheme for
the eMBB control channel
• Massive MIMO use of 2D antenna arrays at
the base station capable of 3D beamforming
• Mobile mmWave bring new opportunities at
spectrum bands above 24 GHz for mobile
broadband
5G vs. 4G (1)
5G vs. 4G (2)
5G vs. 4G (3)
5G vs. 4G (4)
LDPC + Polar Codes
• The Low-Density Parity Check (LDPC) code and polar code are new
channel coding schemes used over the air interface. They have been
introduced in 3GPP Release 15 TS 38.212.
LDPC
• An LDPC code is a linear block code
• It is applied to data channels carrying 5G eMBB
• Uses a parity check matrix for encoding with the formula HcT=0 where:
• C includes information bits and parity bits
•
•
C1 to C5 are information bits
P1 to P5 are parity bits, obtained by encoding based on the parity check matrix H and information bits C1 to C5
• LDPC vs. LTE Turbo Code:
• Low bit rate: similar decoding speed
• High bit rate: LDPC decoding speed >> LTE Turbo Code
• Faster decoding speed:
• Increase the peak rate
• Reduce power consumption
• The LDPC code can better meet data decoding requirements for 5G
services, which feature a high rate, a large bandwidth, and low power
consumption
Polar Codes
• A polar code is a linear block code
• It is applied to control channels used for 5G eMBB services
• Polar code uses a coding matrix
• A Kronecker product operation is performed for a number of times n
• Polar code matrix with a length of N=2n is generated
• Polar code has lower requirements for SNR than LTE coding scheme
for given BLER
Example of Kronecker product operation for n=3 with sample coding matrix
Basic Numerology (1)
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•
•
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Numerology: Cyclic prefix (CP) lengths of different subcarrier spacing
Introduced on 3GPP Release 15 TS 38.211
Two types of CPs: normal and extended
An extended CP is supported only when the subcarrier spacing is 60 kHz
• 0.5ms period
• CP length of the first symbol is
greater than that of other
symbols
• All other CPs have the same
length
Basic Numerology (2)
• Basic numerology supports subcarrier spacing configurations: 15 kHz, 30 kHz, 60
kHz, 120 kHz, and 240 kHz
• 240 kHz subcarrier spacing is used only for DL synchronization
• Different subcarrier spacing can be used to satisfy different delay requirements
for different services
• Larger subcarrier spacing results in a shorter timeslot and a less system delay
• Fast moving UEs experience Doppler shifts
• The faster the UE is moving, the larger the shift is
• Increasing subcarrier spacing reduces the effect of shift and results in more
robust system
Frequency Band
Sub-1 GHz
1 GHz to 6 GHz
Supported Subcarrier
Spacing
15 kHz and 30 kHz
15 kHz, 30 kHz, and 60
kHz
24 GHz to 52.6 GHz 60 kHz and 120 kHz
Current version supports the following subcarrier
spacing configurations: 15 kHz and 30 kHz.
Self-contained Frame Structure (1)
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•
•
•
New timeslot format defined by 3GPP R15 TS 38.211 for TDD mode
Generally, in TDD mode, UL and DL are segregated into different timeslots
Self-contained slot supports both uplink and downlink transmission
Time division multiplexing enables UL and DL information to be transmitted during the same timeslot but
using different orthogonal frequency division multiplexing (OFDM)
• There are two types of self-contained slots: DL-dominant and UL-dominant.
• DL-dominant slot: UL control or SRS can still be transmitted, which shortens the DL feedback delay
• UL-dominant slot: DL control signals can still be transmitted, which shortens the UL scheduling delay
• The switch between UL and DL transmissions must be
performed both on the base station and UE
• A buffer period reserved between UL and DL to ensure
proper signal transmission after the switch
• No signal is transmitted or received within buffer period
• Reserved time is an integer multiple of the time length of an
OFDM symbol
Currently, DL-dominant slots are supported
Self-contained Frame Structure (2)
Slot Configuration (1)
• UL to DL TS allocation ratio is specified by parameter NRDUCell.SlotAssignment
• Format of each timeslot is specified by parameter NRDUCell.SlotStructure parameter. Table 7-1
describes the configurations for the ratio of uplink to downlink timeslots as well as the timeslot
format.
Frequency Band
Uplink to Downlink Timeslot
Timeslot Format
Subcarrier
Allocation Ratio (Specified by
(Specified by
Spacing (SCS)
NRDUCell.SlotAssignment) NRDUCell.SlotStructure)
4:1 (DDDSU)
n77/n78/n79
30 kHz
8:2 (DDDDDDDSUU)
SS1
SS2
SS3
SS4
SS5
SS6
SS51
SS52
SS53
SS54
SS55
SS56
Guard
Period
(GP)
x (ms)
x1
x2
y2
y1
1
2
3
4
5
6
1
2
3
4
5
6
2.5
2.5
2.5
2.5
2.5
2.5
5
5
5
5
5
5
3
3
3
3
3
3
7
7
7
7
7
7
11
10
9
8
7
6
9
8
7
6
5
4
2
2
2
2
2
2
4
4
4
4
4
4
1
1
1
1
1
1
2
2
2
2
2
2
Slot Configuration (2)
• 4:1 (DDDSU) - indicates 3 DL TS, 1 self-contained slot, and 1 UL TS
• 8:2 (DDDDDDDSUU) - indicates 7 DL TS, 1 self-contained slot, and 2 UL TS
• x (indicating the configuration period)
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•
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Range: {0.5, 0.625, 1, 1.25, 2, 2.5, 5, 10} ms
0.625 ms is only used when the subcarrier spacing is 120 kHz
1.25 for subcarrier spacing higher than 60kHz
2.5 for subcarrier spacing higher than 30kHz
Configuration of a single period or two periods is supported
• x1 (number of DL TS) - range: {0, 1, ..., number of TS within a configuration period}
• y1 (number of UL TS) - range: {0, 1, ..., number of TS within a configuration period}
• x2 (number of DL symbols following DL TS) - range: {0, 1, ..., 13}
• y2 (number of UL symbols before UL TS) - range: {0, 1, ..., 13}
• Example:
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•
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NRDUCell.SlotAssignment=4_1_DDDSU
NRDUCell.SlotStructure=SS2
Then: x=2.5; x1=3; x2=10; y1=2; y2=1
Slot Configuration (3)
• Low frequency bands support slot configurations of 4:1 (DDDSU) and 8:2
(DDDDDDDSUU)
• 8:2 configuration is aligned with LTE TDD (with a timeslot structure of DSUDD) to
avoid adjacent-frequency interference or interference caused by coexistence.
• When 8:2 configuration, 5 ms period includes 10 timeslots (the corresponding
subcarrier spacing is 30 kHz): 7 DL TS, 1 self-contained slot, and 2 UL TS
• White area indicates the GP
between UL and DL transmission
• Four UL symbols are used for SRS
• Number of GP symbols can be
configured from 1 to 6
• Number of DL symbols from 9 to 4
accordingly
F-OFDM
• F-OFDM improves spectrum utilization
• More spectrum resources to be used and better system performance than OFDM (1, 2)
• On gNodeB transmitter side, F-OFDM:
• Controls the out-of-band leakage of transmit signals
• Reduces the guard band within the NR channel bandwidth
• Enables more spectrum to be used for DL transmission
• On the gNodeB receiver side, F-OFDM:
• Controls the impact of out-of-band interference on NR
• Reduces the guard band within the NR channel bandwidth
• Enables more spectrum to be used for UL transmission
• F-OFDM enables higher spectrum utilization for NR than LTE
• LTE: 90% spectrum utilization
• For 20 MHz bandwidth and 15kHz subcarrier spacing, NR spectrum resources is 1.08MHz higher than LTE
• For 100 MHz bandwidth and 30kHz subcarrier spacing, NR spectrum resources is 8.28MHz higher than LTE
• 3GPP Rel. 15 supports higher spectrum utilization, which is indicated by the rate of available transmission
bandwidth to channel bandwidth
• F-OFDM feature is used to achieve the maximum spectrum utilization defined in 3GPP specifications