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5G NR Physical Resource Overview
- 2. Rel-14 Rel-15 Rel-16 Rel-13 5G Starts from 3GPP Release 15 Rel-15 Rel-16 5G New Radio Rel-12 5G includes: • New Radio • LTE Advanced Pro evolution • Next-generation core network • EPC evolution
- 3. Key Performance Comparison Between 4G and 5G Throughput 100 Mbit/s 100x Number of connections 100x 5G LTE 10 Gbit/s GAP 1 million connections/km2 10K Delay 30-50 ms 30x - 50x 1 ms
- 4. New Air Interface Technologies SCMA F-OFDM Polar code Full duplex Massive MIMO Mobile Internet IoT Air interface Adaptive (Full-duplex mode) Increases the throughput. (Spatial multiplexing) Increases the throughput. (Channel coding) Improves reliability and reduces power consumption. (Multiple access) Increases the number of connections. (Flexible waveform) Flexibly meets different service requirements.
- 5. F-OFDM: Adaptive Waveform for Air Interface 4G (OFDM): fixed subcarrier bandwidth of 15 kHz. 5G (F-OFDM): Subcarrier bandwidth can flexibly adapt to the packet sizes of different QoE applications. 4G 5G F-OFDM resource allocation OFDM resource allocation OFDM F-OFDM Service adaptation Fixed subcarrier spacing (SCS) Fixed cyclic prefix (CP) Flexible SCS Flexible CP High spectral efficiency 10% of guard bandwidth Minimum guard bandwidth of one subcarrier
- 6. Contents 5G NR Physical Resource 5G NR Channels and Signals on 18B Application 3GPP Protocol Architecture for 5G
- 7. 1 5G Numerology 2 Time-Domain Resources 3 Frequency-Domain Resources 4 Space-Domain Resources 5G NR Physical Resource
- 8. 5G Numerology: refers to SubCarrier Spacing (SCS) and related parameters such as the symbol length and CP length of the NR system NR Air Interface Resources Overview 5G Numerology Time- domain Frequency- domain Space-domain Symbol length SCS CP Slot 1 slot = 14 symbols Subframe Frame REG CCE RB RBG BWP Carrier 1 subframe = 1ms 1 frame = 10ms = 10 subframes 1 RB = 12 subcarriers Antenna port QCL Basic scheduling unit 1 RBG = 2 to 16 RBs 1 BWP = Multiple RB(G)s ≥ 1 BWPs 1 REG = 1 PRB 1 CCE = 6 REGs Data/control channel scheduling unit Unchanged Enhanced Newly added SCS determines the symbol length. Codeword Layer NR Vs. LTE
- 9. Basic Concepts of Frequency-Domain Resources Resource Grid (RG) – Resource group at the physical layer to define bandwidth – Frequency domain: available RB resources within the transmission bandwidth Resource Element (RE) – Smallest unit of physical-layer resources – Time domain: 1 symbol, frequency domain: 1 subcarrier Resource Block (RB) – Basic scheduling unit for data channel – Frequency domain: 12 contiguous subcarriers Resource Block Group (RBG) – Basic scheduling unit for data channel, to reduce 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 symbol, frequency domain: 12 subcarriers (1 PRB) Control Channel Element (CCE) – 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 OFDM symbols One subframe 0 l RB sc RB N N subcarriers RB sc N subcarriers Resource element ) , ( l k 0 k 1 RB sc , max RB, N N k x 1 2 14 l , subframe symb N Resource block
- 10. SCS(SubCarrier Spacing) Scalable Numerology Flexibility Example Case 1 Different spectrum Sub-6 GHz, mmWave Case 2 Multiple services eMBB, URLLC, mMTC Case 3 Multiple scenarios Low/high Speed • Numerologies supported by 3GPP Release 15 (TS 38.211) • Application scenarios: µ SCS CP 0 15 kHz Normal 1 30 kHz Normal 2 60 kHz Normal, extended 3 120 kHz Normal 4 240 kHz Normal 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 SCS (kHz) 15 30 60 120 240 • 3GPP TS 38.104 (RAN4) defines SCS for different frequency bands. SCS for bands below 1GHz: 15 kHz, 30 kHz SCS for bands btw 1GHz and 6GHz: 15 kHz, 30 kHz, 60 kHz SCS for band 24GHz to 52.6GHz: 60 kHz, 120 kHz In Release 15, 240 kHz for data is not considered. • Recommended SCS for different frequency bands (eMBB services):
- 11. 2 Time-Domain Resources: CP, Symbol, Slot, Frame Structure 1 Numerology 3 Frequency-Domain Resources 4 Space-Domain Resources 5G NR Physical Resource
- 12. Frame and subframe length: Tf and Tsf – Tf = 10 ms (frame length) – Tsf = 1 ms (subframe length) Time units for the NR system: Ts and Tc – Tc = 0.509 ns: sampling interval for the SCS of 480 kHz – Ts = 32.552 ns: sampling interval for the SCS of 15 kHz – K = 64: auxiliary parameter Time Units for the Physical Layer
- 13. CP length for different SCS values: CP function: – To eliminate inter-channel interference (ICI) caused by multipath propagation. Cyclic Prefix (CP) Parameter µ SCS (kHz) CP (µs) 0 15 TCP: 5.2 µs for l = 0 or 7; 4.69 µs for others 1 30 TCP: 2.86 µs for l = 0 or 14; 2.34 µs for others 2 60 TCP: 1.69 µs for l = 0 or 28; 1.17 µs for others Extended TCP: 4.17 µs 3 120 TCP: 1.11 µs for l = 0 or 56; 0.59 µs for others 4 240 TCP: 0.81 µs for l = 0 or 112; 0.29 µs for others 2 7 and 0 prefix, cyclic normal 2 144 2 7 or 0 prefix, cyclic normal 16 2 144 prefix cyclic extended 2 512 , CP l l l l N l c cp cp T N T One OFDM symbol time Attitude Symbol N Symbol N+1 S ymbol P eriod T(s) T(g) S ymbol P eriod T(s) Bit P eriod T(b) Cyclic P refix NR CP design principle: – Same overhead as that in LTE, ensuring aligned symbols btw different SCS values and the reference numerology (15 kHz).
- 14. Relationship btw SCS and Symbol Length SCS and Symbol length/ CP length /Slot length Parameter/Numerology (µ) 0 1 2 3 4 SCS (kHz): SCS = 15 x 2^(µ) 15 30 60 120 240 OFDM symbol for data 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 duration(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 = 1ms (14 symbols) SCS = 15 kHz T_symbol … T_slot = 0.5ms (14 symbols) SCS = 30 kHz T_symbol … T_slot = 0.125 ms (14 symbols) SCS = 60 kHz T_symbol
- 15. Frame Structure Architecture SCS (kHz) Slot Configuration (Normal CP) 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: 10ms – SFN range: 0 to 1023 Subframe length: 1ms – Subframe index per system frame: 0 to 9 Slot length: 14 symbols Slot Configuration (Extended CP) 60 12 4 40 Frame structure architecture: – Example: SCS = 30 kHz/120 kHz
- 16. Slot Format and Type Slot structure (section 4.3.2 in 3GPP TS 38.211) – Downlink, denoted as D, for downlink transmission – Flexible, denoted as X, for flexibly usage. – Uplink, denoted as U, for uplink transmission Compared with LTE slot format, NR features: – Flexibility: symbol-level uplink/downlink adaptation in NR while subframe-level in LTE – Diversity: More kinds of uplink/downlink configurations are supported in NR to cope with more scenarios and service types. X – Type 3: flexible-only slot D X X U D X U D X U D X U D X U Type4-1 Type4-2 Type4-3 Type4-4 Type4-5 – Type 4: mixed slot – Type 2: UL-only slot U D Main slot types – Type 1: DL-only slot
- 17. The self-contained type is not defined in 3GPP specifications. The “self-contained” discussed in the industry and literature are featured as: – One slot contains uplink part, downlink part, and GP. – Downlink self-contained slot includes downlink data and corresponding HARQ feedback. – Uplink self-contained slot includes uplink scheduling information and uplink data. Self-contained Slots D U UL control or SRS ACK/NACK D U DL control UL grant Self-contained 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. – High requirements on UE hardware processing – Frequent uplink/downlink switching increases the GP overhead. – In the downlink, only the retransmission delay is reduced. • E2E delay depends on many factors, including the core network and air interface. • The delay on the air interface side is also limited by the uplink/downlink frame configuration, and the processing delay on the gNodeB and UE. Downlink data processing time: Part of the GP needs to be reserved for demodulating downlink data and generating ACK/NACK feedback. D U Air interface round-trip delay
- 18. UL/DL Slot Configuration Configuration (section 11.1 in 3GPP TS 38.213) – Layer 1: semi-static configuration through cell-specific RRC signaling – Layer 2: semi-static configuration through UE-specific RRC signaling – Layer 3: dynamic configuration through UE-group SFI – Layer 4: dynamic configuration through UE-specific DCI Main characteristics: hierarchical configuration or separate configuration of each layer – Different from LTE, the NR system supports UE-specific configuration, which delivers high flexibility and high resource utilization – 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 Separate layer configuration D D D D D D D D U D D D U D Cell-specific RRC configuration/SFI D
- 19. Single-period configuration Dual-period configuration Cell-specific Semi-static Configuration 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 in X type following downlink-only slots – {0,1,…,13} – y2/y4: number of uplink symbols in X type in front of 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
- 21. 2 Time-Domain Resources 1 Numerology 3 Frequency-Domain Resources: RB, RBG, REG, CCE, BWP 4 Space-Domain Resources 5G NR Physical Resource
- 22. 3GPP-defined 5G Frequency Ranges and Bands Frequency range (MHz) 3GPP TS 38.101-2 defines 2 NR frequency ranges: FR1 and FR2. FR1 is often called sub-6 GHz while FR2 is often referred to as millimeter wave. 5G frequency band 3GPP TS 38.101 mainly defines NR frequency bands. NR and LTE have some frequency bands in same but the frequencies are represented in different ways. 450 MHz 6000 MHz 24.25 GHz 52.6 GHz Frequency Range 1 (FR1) Frequency Range 2 (FR2) Source: 3GPP TS 38.101 Frequency range
- 23. Basic Concepts of Frequency-Domain Resources Resource Grid (RG) – Resource group at the physical layer to define bandwidth – Frequency domain: available RB resources within the transmission bandwidth Resource Element (RE) – Smallest unit of physical-layer resources – Time domain: 1 symbol, frequency domain: 1 subcarrier Resource Block (RB) – Basic scheduling unit for data channel – Frequency domain: 12 contiguous subcarriers Resource Block Group (RBG) – Basic scheduling unit for data channel, to reduce 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 symbol, frequency domain: 12 subcarriers (1 PRB) Control Channel Element (CCE) – 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 OFDM symbols One subframe 0 l RB sc RB N N subcarriers RB sc N subcarriers Resource element ) , ( l k 0 k 1 RB sc , max RB, N N k x 1 2 14 l , subframe symb N Resource block
- 25. RB Location Index and Indication The BWP is introduced in 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. – BWP: new concept introduced. 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 start point is aligned with Point A. – Physical RB (PRB): index in the BWP – The start point is aligned with the BWP start point. – The relationship between PRB and CRB is as follows: Point A Reference Location Offset PCell DL (TDD/FDD) UEs perform blind detection to obtain this information from SSB. UEs are informed of this information through the RMSI. PCell UL (TDD) Same as Point A for the PCell downlink PCell UL (FDD) Frequency-domain location of the ARFCN UEs are informed of this information through the RMSI (SIB1). 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. SUL 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. start BWP, PRB CRB i N n n
- 26. Definition and characteristics – The BWP is a new concept introduced in the NR system. It is a set of contiguous bandwidth resources allocated by the gNodeB to UEs. Its configuration is mandatory for 5G service access. – It is a UE-level concept (BWP configurations vary with UEs). All channel resources allocated to UEs or to be scheduled are within the BWP range. 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 Definition and Application Scenarios Numerology 1 BWP1 Carrier Bandwidth #3 Numerology 2 BWP 2 BWP BWP Bandwidth Carrier Bandwidth #1 BWP 2 #2 BWP 1 Carrier Bandwidth
- 27. BWP Types • Initial BWP: used in the initial access phase • Dedicated BWP: configured for UEs in RRC_CONNECTED mode. -- According to 3GPP specifications, a maximum of 4 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 3GPP specifications, a UE in RRC_CONNECTED mode can activate only 1 dedicated BWP at a given time. • Default BWP: one of the dedicated BWPs used by the UE in RRC_CONNECTED mode after the BWP inactivity timer expires. 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
- 28. NR-ARFCN Calculation Frequency range ΔFGlobal FREF-Offs [MHz] NREF-Offs Range of NREF 0 – 3000 MHz 5 kHz 0 MHz 0 0 – 599999 3000 – 24250 MHz 15 kHz 3000 MHz 600000 600000 – 2016666 24250 – 100000 MHz 60 kHz 24250 MHz 2016667 2016667 – 3279167 • ΔFRaster is the channel raster granularity, which may be equal to or larger than ΔFGlobal. -- The channel raster for each operating band is recommended as below (Section 4.3.1.3 in TR38.817-01) Bands FR1 FR2 Sub2.4G 2.6G~6G 24.25G~52.6G Channel raster 100kHz 15kHz 60kHz • The relation between the NR-ARFCN NREF and the RF reference frequency FREF in MHz for the downlink and uplink is given by the following equation: FREF = FREF-Offs + ΔFraster (NREF – NREF-Offs) where FREF-Offs and NRef-Offs are given in below (Table 5.4.2.1-1 in 3GPP TS 38.104), and ΔFGlobal could be used as ΔFraster
- 29. 2 Time-Domain Resources 1 Numerology 3 Frequency-Domain Resources 4 Space-Domain Resources: Layer, Antenna Port, QCL 5G NR Physical Resource
- 30. Codeword 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 – Used to define mapping relationship btw codewords and transmit antenna. – Antenna port – 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 maximum number of layers – For DL/User: 8@SU; 4@MU – For UL/User: 4@SU or MU Protocol-defined number of antenna ports Channel/Signal Maximum Number of Ports UL PUSCH with DMRS 8 or 12 PUCCH 1 PRACH 1 SRS 4 DL PDSCH with DMRS 8 or 12 PDCCH 1 CSI-RS 32 SSB 1 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
- 31. Quasi-Colocation (QCL) Definition: – Two antenna ports are quasi co-located if the properties of the channel over which a symbol on one antenna port is conveyed can be inferred from the channel over which a symbol on the other antenna port is conveyed. – The channel properties include delay spread, Doppler spread, Doppler shift, average gain, average delay (existing in the LTE), and spatial Rx parameter (added in NR). Type – QCL-TypeA: {Doppler shift, Doppler spread, average delay, delay spread} – QCL-TypeB: {Doppler shift, Doppler spread} – QCL-TypeC: {average delay, Doppler shift} – QCL-TypeD: {Spatial Rx parameter} Application scenarios – RRM management: such as type C – Obtaining channel evaluation information: such as type A, and type B – Assisting UEs in beamforming (forming a spatial filter and beam indication): such as type D QCL configuration – The QCL linkage between RSs is configured through high-layer signaling. – QCL linkage before RRC: – QCL linkage after RRC: Source RS Target RS QCL type SSB PDSCH DMRS PDCCH DMRS SSB PDSCH DMRS PDCCH DMRS TRS CSI-RS for CSI Type C, Type C+Type D Type A Type A+Type D Type A/Type B Type D Type A+Type D CSI-RS for BM Type C+Type D Type D
- 32. Contents 5G NR Channels and Signals on 18B Application 5G NR Physical Resource 3GPP Protocol Architecture for 5G
- 33. 1 Overview 2 Application on 18B 5G NR Channels and Signals on 18B Application
- 34. NR Physical Channels and Signals Overview Downlink Physical Channel PBCH PDCCH PDSCH Physical Signal DMRS PTRS CSI-RS PSS/SSS Uplink Physical Channel PRACH PUCCH PUSCH Physical Signal DMRS SRS PTRS Downlink Physical Channel/Signal Functions SS Used for time-frequency synchronization and cell search. PBCH Carries system information to be broadcast. PDCCH Transmits control signaling, such as signaling for uplink and downlink scheduling and power control. PDSCH Carries downlink user data. DMRS Used for downlink data demodulation and time-frequency synchronization. PTRS Tracks and compensates downlink phase noise. CSI-RS Used for downlink channel measurement, beam management, RRM/RLM measurement, and refined time-frequency tracking. Uplink Physical Channel/Signal Function PRACH Carries random access request information. PUCCH Transmits L1/L2 control signaling, such as signaling for HARQ feedback, CQI feedback, and scheduling request indicator. PUSCH Carries uplink user data. DMRS Used for uplink data demodulation and time-frequency synchronization. PTRS Tracks and compensates uplink phase noise. SRS Used for uplink channel measurement, time-frequency synchronization, and beam management.
- 35. Application of NR Physical Channels Physical channels involved in cell search – PSS/SSS -> PBCH -> PDCCH -> PDSCH Physical channels involved in random access – PRACH -> PDCCH -> PDSCH -> PUSCH Physical channels involved in downlink data transmission – PDCCH -> PDSCH -> PUCCH/PUSCH Physical channels involved in uplink data transmission – PUCCH -> PDCCH -> PUSCH -> PDCCH gNodeB UE PSS/SSS MIB (PBCH) RMSI (PDCCH, PDSCH) ... Preamble (PRACH) RAR (PDCCH, PDSCH) Msg3 (PUSCH) Msg4 (PDCCH, PDSCH) HARQ excluded from RAR HARQ included in Msg4 Cell search Random access gNodeB UE CSI-RS ... Data (PDCCH, PDSCH) Data (PDCCH, PDSCH) Downlink data transmission CSI (PUCCH/ PUSCH) ACK/NACK (PUCCH/ PUSCH) ... Paging (PDCCH, PDSCH) gNodeB UE SRS ... UL Grant (PDCCH) ACK/NACK (PDCCH) Uplink data transmission SR (PUCCH) BSR/Data (PUSCH) BSR/Data (PUSCH)
- 36. Time-Frequency Domain Distribution Schedulable and configurable resources through flexible physical channel and signal design. GP BWP PDCCH DMRS for PDSCH PDSCH SSB CSI-RS UL (SRS) PUSCH PUCCH DMRS for PUSCH PRACH
- 37. 2 Application on 18B Application 1 Overview 5G NR Channels and Signals on 18B Application
- 38. The Basic Functions of NR Air Interface • Channel Mapping and Comparison with 4G Broadcast information Paging Information User control plane information User data plane information BCCH PCCH DCCH CCCH DTCH BCH PCH DL/UL SCH PBCH PDCCH&PDSCH/ PUCCH&PUSCH/PRACH Content is classified Transmission rule is defined Information Function SS SSB DM-RS DM-RS DM-RS Physical resource is specified Logical Channel Transport Channel Physical Channel
- 39. Physical Resource Definition Time Domain Frequency domain Concept Explanation SCS 15/30/60/120k RB 1RB = 12 SCs RBG 1 RBG = 2/4/8/16 RBs RG (Grid) Cell bandwidth, 273 RB@100M with 30kHz SCS Point A Basic reference point for positioning RB in RG CRB Index in RG (based on Point A） BWP The part of UE working bandwidth in RG offset Relation btw CRB and PRB PRB Index in BWP CORESET the physical resource for PDCCH Frame SubFrame SubFrame SubFrame …… Slot Slot Slot …… Sym bol Sym bol Sym bol …… Sym bol 1,2,4,8 14x UL/DL/Self-Contain: 1:3:1 D/X/U in self-contain: 10:2:2
- 40. Initial BWP and CORESET Initial DL BWP configuration – The initial BWP equals the frequency-domain location and bandwidth of RMSI CORESET. – The frequency-domain location of the initial BWP is determined by the SSB location and the bandwidth of RMSI CORESET, and is sent to UEs through the MIB and SIB1. UEs obtain the SSB frequency-domain location through SI (MIB). UEs read SI to obtain the frequency offset and CORESET bandwidth. The frequency-domain location and bandwidth of RMSI CORESET are determined. Frequency Time SSB CORESET PDSCH Frequency offset Initial DL BWP The frequency offset is defined as the frequency difference from the lowest PRB of RMSI to the lowest PRB of SS/PBCH block. UEs obtain information about the frequency-domain location and bandwidth of the initial BWP. Procedure for UEs to determine the downlink initial BWP
- 41. PSS/SSS: Introduction Main functions – Used by a UE for downlink synchronization, – Used for obtaining cell IDs. Resource allocation – A SS occupies 1 symbol in the time domain and 127 REs in the frequency domain. Differences with LTE – SS in NR can be flexibly configured in any position on the carrier and do not need to be positioned at the center frequency. – Subcarrier spacings for the PSS/SSS vary with operating frequency bands and are specified by 3GPP. PSS SSS Carrier center Flexible SS/PBCH position Initial BWP Different from LTE with 504 PCIs, NR physical cell IDs are numbered from 0 to 1007 and divided into 3 groups, with each group containing 336 cell IDs.
- 42. Transmission of SSB • The PSS/SSS and the PBCH are combined as an SSB block in 5G to allow for massive MIMO. SSB configuration varies with SCS -- SSB block position within the slot -- Slot numbers for SSB blocks with different subcarrier spacings and different beams Beam 7 Beam 0 Beam 1 … … SSB transmission in 18B -- Broadcast information is scheduled every 80ms -- PBCH is transmitted every 20ms with 8 beams each time To fasten UL sync. in larger bandwith in NR, sync. rasters with 900 kHz, 1.44 MHz, and 17.28 MHz are defined.
- 43. PDCCH&PDSCH Working Mechanism 1 slot PDSCH 1 CCE = 6 REG = 1 RB 1 RB CCE: User scheduling granularity 0 1 2 3 4 5 6 7 1 CCE 2 CCEs 4 CCEs 8 CCEs CCE CCE allocation (aggregation level) According to different encoding rates, a gNodeB can aggregate 1, 2, 4, 8, or 16 CCEs to constitute a PDCCH for UE blind detection RNTIs used by DCIs – P-RNTI (paging message) – SI-RNTI (system message) – RA-RNTI (RAR) – Temporary C-RNTI (Msg3/Msg4) – C-RNTI (UE uplink and downlink data) – SFI-RNTI (slot format) – INT-RNTI (resource pre-emption) – TPC-PUSCH-RNTI (PUSCH power control command) – TPC-PUCCH-RNTI (PUCCH power control command) – TPC-SRS-RNTI (SRS power control command) PDCCH 18B supports maximum 2 layers spatial multiplexing of PDCCH
- 44. DMRS for PDSCH Introduction DMRS category: Different in low-speed and high-speed scenarios – Front Loaded (FL) DMRS: Occupies 1 to 2 symbols – Additional (Add) DMRS: Occupies 1 to 3 symbols, used in high-speed scenarios for anti- Doppler spread. DMRS type: Different DMRS types allow different maximum numbers of ports. – Type1: Single-symbol: 4, dual-symbol: 8 – Type2: Single-symbol: 6, dual-symbol: 12 DMRS time-frequency mapping position – Mapping type A: Staring from the 3rd or 4th symbol in the slot. – Mapping type B: Staring from the 1st symbol on the scheduled PDSCH. FL DMRS Add DMRS Type2, dual-symbol Slot k l 0 1 2 3 4 5 6 7 8 9 10 11 12 13 SCn11 SCn10 SCn9 SCn8 SCn7 SCn6 SCn5 SCn4 SCn3 SCn2 SCn1 SCn0 1000/1001/1004/1005 1002/1003/1006/1007 1000/1001/1006/1007 1002/1003/1008/1009 1004/1005/1010/1011 Slot k l 0 1 2 3 4 5 6 7 8 9 10 11 12 13 SCn11 SCn10 SCn9 SCn8 SCn7 SCn6 SCn5 SCn4 SCn3 SCn2 SCn1 SCn0 Type1, dual-symbol Slot k l 0 1 2 3 4 5 6 7 8 9 10 11 12 13 SCn11 SCn10 SCn9 SCn8 SCn7 SCn6 SCn5 SCn4 SCn3 SCn2 SCn1 SCn0
- 45. CSI-RS: Main Functions The main functions and types of the CSI-RS are as follows: Design principles and features of the CSI-RS: – Sparsity: The density of the time and frequency domains is low and the domain resource consumption is low. The maximum number of ports is 32. – Sequence generation and cell ID decoupling: The scrambling code ID is configured by higher layer parameters. UCNC is supported. – Flexible resource configuration: UE-specific configurations for time-frequency resources are supported. Function Description Channel quality measurement CSI obtaining Used for channel state information (CSI) measurement. The UE reports the following content: CQI, PMI, rank indicator (RI), layer Indicator (LI) Beam management Used for beam measurement. The UE reports the following content: L1-RSRP and CSI-RS resource indicator (CRI) RLM/RRM measurement Used for radio link monitoring (RLM) and radio resource management (handover). The UE reports the following content: L1-RSRP Time-frequency offset tracing (TRS) Used for precise time-frequency offset tracing.
- 46. CSI-RS: Pattern – The row 1 pattern is used only for TRS. – The row 2–18 patterns can be used for CSI measurement. – The CSI-RS used for beam management can only use patterns of 1 port and 2 ports (row 2–3). 1 port 2 ports 4 ports 8 ports 12 ports 16 ports 24 ports 32 ports CSI-IM Pattern 0 CSI-IM Pattern 1 CDM type indicates the number of ports that can be multiplexed by each colored resource. 1 1 3 No CDM 2 1 1, 0.5 No CDM 3 2 1, 0.5 FD-CDM 2 4 4 1 FD-CDM 2 5 4 1 FD-CDM 2 6 8 1 FD-CDM 2 7 8 1 FD-CDM 2 8 8 1 CDM 4 (FD 2, TD 2) 9 12 1 FD-CDM 2 10 12 1 CDM 4 (FD 2, TD 2) 11 16 1, 0.5 FD-CDM 2 12 16 1, 0.5 CDM 4 (FD 2, TD 2) 13 24 1, 0.5 FD-CDM 2 14 24 1, 0.5 CDM 4 (FD 2, TD 2) 15 24 1, 0.5 CDM 8 (FD 2, TD 4) 16 32 1, 0.5 FD-CDM 2 17 32 1, 0.5 CDM 4 (FD 2, TD 2) 18 32 1, 0.5 CDM 8 (FD 2, TD 4) Row Ports Density CDM Type
- 47. Overhead Estimation (average to per DL slot) SS Block For sync and MIB and beam sweeping 20.4% CSI-RS (Channel State Information RS) For DL channel measurement PDCCH Control channel for DL grant and UL grant RMSI (remaining minimum system information) System information transmitted in PDSCH DMRS (Demodulation RS) For data coherent demodulation TRS (Tracking RS) For doppler shift tracking GP at Self-contained slot For TDD system DL/UL conversion 3.6% (2 symbols) UL at Self-contained slot For UL transmission 3.6% (2 symbols) DL effective RE ratio calculation Total RB number 273 OFDM symbol number per slot 14 SCS number per RB 12 Total REs Per slot (Includes overhead) 45864 Effective REs per DL slot 33200 DL Effective RE ratio 72.4% DL Effective RE ratio (excludes UL at Self-contained slot) 76% 18B DL User Peak Throughput@3.5GHz 100MHz TDD DL Peak throughput = 33200 * 8 (256QAM) * 0.92 * 8 / 0.0005 * 0.8 (DL/(UL+DL))* 90% ≈ 2.8G • DL Peak throughput = • Effective REs per DL slot × Bits for modulation order × Coding rate × Layers/ Slot length (s) × DL ratio × (1-BLER)
- 48. 2 Waveforms Supported in PUSCH Waveform Modulation mode Codeword Number of Layers RB Resource Allocation PAPR Application Scenario CP-OFDM QPSK, 16QAM, 64QAM, 256QAM 1 1–4 Contiguous/ non-contiguous High At/near the cell center DFT-S-OFDM π /2-BPSK, QPSK, 16QAM, 64QAM, 256QAM 1 1 Contiguous Low At the cell edge (achieving gain by using a low PAPR) Waveform: Unlike PDSCH, PUSCH supports 2 waveforms. – CP-OFDM: a multi-carrier waveform that supports MU-MIMO. – DFT-S-OFDM: a single-carrier waveform that supports only SU-MIMO and improves the coverage performance. Physical layer procedures Scrambling Modulation mapper Transform precoder Resource element mapper SC-FDMA signal gen. Scrambling Scrambling Modulation mapper Modulation mapper Layer mapper Precoding Resource Element mapper Resource Element mapper OFDM signal generation OFDM signal generation Codewords Layers Antenna ports CP-OFDM DFT-S-OFDM
- 49. Contents 5G NR Physical Resource 5G NR Channels and Signals on 18B Application 3GPP Protocol Architecture for 5G
- 50. 3 Main TSGs (Technical Specification Group) Project Co-ordination Group (PCG) TSG RAN Radio Access Network TSG SA Service & Systems Aspects TSG CT Core Network & Terminals RAN WG1 Radio Layer 1 spec SA WG1 Services CT WG1 MM/CC/SM (lu) RAN WG2 Radio Layer 2 spec Radio Layer 3 RR spec SA WG2 Architecture CT WG3 Interworking with external networks RAN WG3 lub spec, lur spec, lu spec UTRAN O&M requirements (transmission interfaces) SA WG3 Security CT WG4 MAP/GTP/BCH/SS RAN WG4 Radio Performance Protocol aspects SA WG4 Codec CT WG6 Smart Card Application Aspects RAN WG5 Mobile Terminal Conformance Testing SA WG5 Telecom Management RAN WG6 Legacy RAN radio and protocol SA WG6 Mission-critical applications TSGs are responsible for 3GPP standard finalization.
- 51. TSG SA Protocol Architecture • TR：Technical Report • TS：Technical Specification SA WG1 TR 22.891：Study on New Services and Markets Technology Enablers （New service study） TR 22.861：FS_SMARTER - massive Internet of Things （Massive IoT） TR 22.862：Feasibility study on new services and markets technology enablers for critical communications; Stage 1 （Critical Communication） TR 22.863：Feasibility study on new services and markets technology enablers for enhanced mobile broadband; Stage 1（eMBB） TR 22.864：Feasibility study on new services and markets technology enablers for network operation; Stage 1（Network operation） TS 22.261：Service requirements for next generation new services and markets SA WG2 TR 23.799：Study on Architecture for Next Generation System SA WG3 TR 33.899： Study on the security aspects of the next generation system TS 23.501：System architecture for the 5G system TS 23.502：Procedure for the 5G system
- 52. Protocol Study Suggestion TR22.861 TR22.862 SA1 TR22.891 TS38.401 RAN3 TR38.801 RAN1 TR38.802 TS38.2XX (7TSs) RP TR38.912 5G Requirement 5G Network 5G NR RP TR38.913 TR22.863 TR22.864 TS23.501 TS23.502 SA2 TR23.799 TS38.41X (5TSs) TS38.42X (6TSs) TS38.47X (6TSs) New service and market technology Scenario and requirement Network architecture RAN interface Air interface technology (L1) RAN2 TR38.804 TS38.3XX (7TSs) TS37.324 TS37.340 Air interface technology (L2/L3)
Notas do Editor
- The time and frequency resources of the system are understood as a carriage. When orthogonal frequency division multiplexing (OFDM) is used for decoration, the train can provide only a fixed size of hard seat (subcarrier bandwidth). Everyone, regardless of fat, thin, rich, or poor, can only sit on a hard seat of the same size. This is not scientific or humanized. For 5G, we hope that seats and space can be customized based on passengers' requirements: hard seat, soft seat, sleeper, and private compartment. This can be achieved through filtered orthogonal frequency division multiplexing (F-OFDM) proposed by Huawei. F-OFDM provides different subcarrier bandwidths and CP configurations for different services to meet the time-frequency resource requirements of different services. Subcarriers of different bandwidths are not orthogonal. This is flexible. However, how to reduce the system overhead? F-OFDM uses optimized filters (baseband implementation) to minimize the guard band between subcarriers of different bandwidths to at least one subcarrier bandwidth.
- QCL: (Quasi-Co-Location) Definition of QCL is that 2 antenna ports are said to be quasi co-located if properties of the channel over which a symbol on one antenna port is conveyed can be inferred from the channel over which a symbol on the other antenna port is conveyed
- RB is used for resource scheduling type1, and RBG is used for resource scheduling type0. The CCE is the control channel scheduling unit. For the control channel DCI, the scheduling is from 1CCE, 2CCE, 4CCE, 8CCE, 16CCE.
- The CP of the first symbol every 0.5ms is longer than the others, and the long point is 16*k, where k is the auxiliary factor defined earlier. The right table gives the CP length under different SCS, which is consistent with LTE at 15k, and is scaled down later. NR also defines extended CP, but only under 60kHz SCS, extended CP is 512k, which is 4.17 microseconds.
- The symbol of OFDM is the sum of data and CP length. The relationship between Slot and SCS is inversely proportional, and scales down as the subcarrier spacing increases. Countdown: reciprocal
- Slot is very flexible defined in NR. It consists of 3 parts, downlink, denoted by D, for downlink transmission; flexible, denoted by X, can be downlink, uplink, or as reserved resource, used for forward direction. Compatibility; uplink, denoted by U, for uplink transmission. It is mainly divided into 4 categories, of which type 4-5 is special, and there are 2 uplink and downlink handovers in one slot, which are generally considered to be used in uRLLC services. For example, a 7-symbol mini-slot, also known as a non-slot based transmission, considers a scheduling period of less than 1 slot, which is 2/4/7, and is called a mini slot scheduling cycle scenario
- The downlink self-contained, that is, the downlink ACK/NACK in one slot is directly fed back in the uplink part of the same slot; the uplink self-contained, that is, the scheduling of the uplink PUSCH in the slot, the DL grant can be directly downlinked in the same slot. Part to indicate. That is, the feedback or scheduling of data is completed in the same slot, called self-contained. The goal of the design is to provide faster feedback and reduce latency; in addition, Sounding's transmission cycle can be shorter, which is convenient for tracking fast changes of the channel and improving BF new energy. In practical applications, there are still many challenges in self-contained. The first is to ensure that the uplink is fed back in the same slot. Part of the GP is used. The GP is compressed and the coverage is limited. If you increase the number of GP symbols, it will bring extra overhead.
- If the entire network is configured uniformly, only the first layer configuration can be used. The subsequent layer-by-layer configuration can only further clarify the flexible subframes that are not configured in the previous layer. Configuration (section 11.1 in 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
- How is the configuration of the first floor cell level? The protocol gives five parameters in one cycle. First, there is a matching period. LTE also has 5 and 10ms, but the NR period is more flexible. The small period is used for SCS over 30. For example, 0.625 is only used for 120SCS, 1.25. For 60 or more, 2.5 is used for 30 or more. For a single period of 5 parameters (X, x1, x2, y2, y1), for a double period 10 parameters (X, x1, x2, y2, y1, Y, x3, x4, y4, y3), where x2 and y2 What is not matched between x4 and y4 is the flexible reservation or GP length.
- The third layer, through the dynamic configuration of SFI, SFI is a DCI format in the PDCCH, which is mainly used to tell the format information of a slot. SFI defines the uplink and downlink ratio information in a slot. The protocol defines a total of 256 types. As long as the index is clear, you will know the matching information inside.
- Supplementary Uplink (SUL) for uplink and downlink decoupling
- RB is used for resource scheduling type1, and RBG is used for resource scheduling type0. The CCE is the control channel scheduling unit. For the control channel DCI, the scheduling is from 1CCE, 2CCE, 4CCE, 8CCE, 16CCE.
- PRB in NR refers to a position index within a BWP pointA: the reference point available for transmission bandwidth If the Reference location does not consider CA, it is obtained through SSB blind check. In the RMSI message, the offset between the pointA and the reference location will be told to the UE. Where are the starting positions of the pointA through these two?
- Scenario2: When the UE does not perform services for a long time, the measured bandwidth does not need to measure the entire bandwidth, so a small bandwidth, that is, a small BWP, can be configured to save power. Scenario3: The same BWP can only support one kind of numerology. Therefore, to achieve different numerology support for the same cell, multiple BWPs must be implemented.
- The layer is directly mapped to the antenna port. Because there is transmit diversity, the number of layers is smaller than the number of antenna ports. If the channel conditions are good enough, no transmit diversity is required, and the number of layers is equal to the number of antenna ports. The antenna port is a logical concept defined by a reference signal on the physical antenna transmit channel
- Easy to multiplex channel estimation information for 2 antenna ports Since NR introduces the beam concept, new spatial parameters are added. The quasi-co-location is used to assist the receiver in demodulating the channel, or the UE side performs beamforming, beam reception and transmission. There are 4 types in the type, and the channel characteristics are different, so the effect is different. The source and destination RSs can be configured with QCL relationships. Through four types and types, such as typeA, if QCL is met, the target can use the information obtained by source. For example, if the antenna port of an SSB and the antenna port of the PDSCH DMRS satisfy the QCL relationship, there are timing information estimated by the SSB, and channel estimation parameters such as delay extension, which can be used for PDSCH demodulation. Before the RRC connection, both the SSB and the PDSCH/PDCCH have a default QCL relationship, which can be matched or not. After the RRC connection, the relationship will be more complicated, and the high and low frequencies will be different. It is generally considered that the high frequency needs to be matched with the typeD parameter, the low frequency beam mainly passes the sounding, and the UE side does not use the beam scanning process, so the low frequency is used less. The QCL relationship is that there is a mapping relationship between SSB and TRS. TRS is used for time-frequency tracking, and its channel estimation information can be used for demodulation of PDSCH/PDCCH DMRS.
- PT-RS: phase noise compensation, phase noise tracking signal CSI-RS has more effects Uplink and LTE are similar, adding PT-RS
- Schematic diagram of physical channel and signal time-frequency domain distribution: flexible physical channel and signal design, everything is scheduled/configurable; Down PDCCH: the time domain occupies 1~3 symbols before the Slot, and the frequency domain uses resources configurable; supports FDM resource sharing on the same symbol of PDCCH and PDSCH; DMRS for PDSCH: time domain location configurable; frequency domain density and resource configurability; support for DMRS and PDSCH FDM resource sharing on the same symbol; SSB: The time domain is fixed; the frequency domain occupies 20 RBs, and the frequency domain location is configurable; and FDM resource sharing on the same symbol of SSB and PDSCH is supported; CSI-RS: time domain location configurable, frequency domain location and bandwidth configurable; support for FDM resource sharing on the same symbol of CSI-RS and PDSCH; Upstream Long PUCCH: The time domain occupies 4~14 symbols, and the time-frequency domain location and usage resources are configurable; Short PUCCH: The time domain occupies 1~2 symbols, and the time-frequency domain location and usage resources are configurable; DMRS for PUSCH: time domain location configurable; frequency domain density and resource usage configurable; support for DMRS and PUSCH FDM resource sharing on the same symbol; PRACH: Time-frequency domain location and usage resources are configurable; SRS: time domain location configurable, frequency domain location and bandwidth configurable; Synchronization Raster definition The UE needs to search for the SS/PBCH block when it is powered on; if the UE does not know the frequency, it needs to blindly check all the frequency points in the UE support band according to a certain step size; since the cell bandwidth in the NR is very wide, according to the channel raster Blind detection, the UE access speed is very slow, for this purpose, the UE specifically defines the Synchronization Raster: 900KHz, 1.44MHz and 17.28MHz;
- The type of message transmitted: 1. broadcast message, 2. paging message, NSA does not, but it is definitely needed in the future SA networking, 3. user control message and user side media data As far as the control plane is concerned, in the current 5G NSA networking, the control messages of all users are not directly communicated with the UE through the 5G air interface, so it can be considered that the current 5G does not have the user's control message. Therefore, only the MIB message of the broadcast message is currently sent, even SIB1 (called RMSI in 5G). Therefore, under the current NSA network, the 5G air interface only sends broadcast MIB messages and user media data. So channel mapping becomes very simple. Channel mapping: logic-transport-physical. The so-called logical channel is to distinguish between what is sent by the content. If it is a different thing of the same user, or something different from the user, because the content is different, different logical channels are needed. For example, broadcast messages, or user plane data, such as VoLTE voice data, or Internet traffic data, these data are all different logical channels. It can be understood as the concept of the other party. The base station sends a lot of things to the mobile phone through the air interface. Before the official delivery, all the devices are separately stacked at the base station, and the RNTI+ channel identifier is used to distinguish different types of messages. The RNTI is the wireless air interface of each user. A unique identifier in the network. In the upper layer, different users are distinguished by RNTI, and different information of each user is distinguished by a channel identifier. The RNTI is an identifier assigned by the base station after the user accesses the network, and is unchanged during the access period. Therefore, the difference between CCCH and DCCH is that before the user accesses the network and after accessing the network, it is not important. The unified is the user control message. The transmission channel emphasizes the transmission rules. For example, the current 18B version of the control plane only broadcast messages, so the logical channel heap is just MIB messages. Every 80ms of the broadcast channel, L2 is responsible for scheduling the message once. This rule is defined by the transport channel. Different content, the sending rules are not necessarily different, such as user plane scheduling, scheduling rules do not vary with the user information content, from 3G to 4G to 5G, this user plane scheduling is more flexible, user messages, whether it is control The message, or the user plane data, all go to the shared channel. The rules are the same. The 18B C-band is scheduled for 0.5ms. The physical channel defines the resources. For example, the BCCH defines the content. The BCH defines the scheduling every 80ms. Under which the content is sent on which resources, that is, the content defined by the PBCH. That is to define the location of the specific resources from the time and frequency. At present, 5G, in addition to the physical resources occupied by the PBCH defining the broadcast signal, the downlink also has a PDCCH, a PDSCH, and an uplink PUCCH, a PRACH, and a PUSCH to define resources used for transmitting the shared channel. Since the data plane resources are shared, PDCCH/PUCCH is needed to control the scheduling.
- RG: Resource Grid, the number of RBs included in the entire spectrum bandwidth. BWP: BandWidth Part, directly related to the user PointA: the starting position of the entire RG CRB: common RB, which defines the location of the RB relative to pointA. PRB: Define the location of the RB in the BWP The part of the control area that is blindly checked in the BWP is called CORESET (COntrol Resource SET), that is, in the BWP, the user needs to blindly check the control part of the monitor.
- The RMSI message tells the start position of the initial BWP and the offset of the SSB start position. Upstream BWP agreement has not been fully determined After the user boots, press raster to scan the entire bandwidth, obtain the SS, get the cell PCI, and determine the 5G cell. (Under the current NSA network, the frequency is obtained through the configuration of 4G, without the terminal to scan), SS and PBCH are together, called SSB, so the MIB message sent in the PBCH is obtained, and the MIB will pass the indication offset. (in units of carriers) notifying the location of pointA, configuring CORESET, defining the frequency domain location of the PDCCH, scheduling the SI, and telling the UE to read the system message in the CORESET (Common CORESET) range. According to the message indicated by CORESET, the scheduling is received, that is, SIB1 is read. These messages are called RMSI (ie, 4G SIB1), and RMSI is in PDSCH. The SIB1 will notify the mobile phone of the initial BWP, which is part of the PDSCH. So the initial BWP should include CORESET RMSI is called SIB1 First, after obtaining the PCI, the SSB reads the MIB and obtains the pointA, thereby configuring the Coreset to obtain the SI. Then, through the coreset, the SIB1 can be received, thereby reading the initial BWP, that is, the part of the PDSCH. That is, the bandwidth of the initial BWP includes coreset.
- Open another layer and watch the SSB. SSB accounts for 20 RB resources. The broadcast message is sent once in 80ms, which is the definition of L2. It can be considered that the broadcast message is updated every 80ms. However, in the physical layer, the period of transmission alone is not the same 20ms transmission period, and is sent 4 times in 80ms to ensure reliability. At the same time, in order to allow more resources to be used for data services, the protocol definition must be completed in the first 5 ms of 20ms. At present, the realization of our products is to send SSB in the first 2 ms of 5ms, that is, 4 slots. Each slot sends 2 SSBs, and each SSB is sent on different narrow beams, for a total of 8 narrow beams. Therefore, the SSB's resource ratio in the entire time-frequency resource is very small. Under the current implementation, (20*3+12)*8/273*20*2*14≈0.4%, in some special beam scenarios. For example, if there is only one SSB in the peak scenario, then the remaining 7 SSB resource locations can be saved for data services to ensure peak rate. The following is an index with the first symbol of the SSB: - Case A - 15 kHz subcarrier spacing: The first symbol index of the candidate SS / PBCH block is an index of {2,8} + 14 * n. For carrier frequencies less than or equal to 3 GHz, n = 0,1. For carrier frequencies greater than 3 GHz and less than or equal to 6 GHz, n = 0, 1, 2, 3. - Case B - 30 kHz subcarrier spacing: The first symbol index of the candidate SS / PBCH block is {4, 8, 16, 20} + 28 * n. For carrier frequencies less than or equal to 3 GHz, n = 0. For carrier frequencies greater than 3 GHz and less than or equal to 6 GHz, n = 0,1. - Case C - 30 kHz subcarrier spacing: The first symbol index of the candidate SS / PBCH block is {2,8} + 14 * n. For carrier frequencies less than or equal to 3 GHz, n = 0,1. For carrier frequencies greater than 3 GHz and less than or equal to 6 GHz, n = 0, 1, 2, 3.
- How to put 14 symbols in each slot, how to divide the PDCCH resources, is the first 1 to 3 symbols of a slot, and is the same as LTE. The PDCCH is responsible for paging, power control, and scheduling information. The REG is a combination of 12 SCs in the frequency domain and 1 symbol in the time domain. The figure is 2 REGs. The current 5G supports spatial division multiplexing of the PDCCH, that is, it can be spatially complex. Use, to reuse the same time-frequency REG to 2 users. The six REGs are put together as a CCE. The CCE is the smallest unit for scheduling users. Several CCEs are used for user scheduling. Depending on the channel conditions, the current definition is 1, 2, 4, 8, and 16, the so-called scheduling level. Up to 16 levels. Improve the transmission reliability of CCE by adding redundant bits. 273 RBs, each RB has 1 REG, then from the time domain, 1 symbol is 273 REGs, 6 REGs form a CCE, so 273 REGs are 45 CCEs, then 1 scheduling period If it is a symbol user PDCCH, it can schedule up to 45 users. If it is 2 symbols, it can schedule up to 91, and so on. If you can do 2 layers of spatial multiplexing, then double. This resource is defined by CORESET. The user does not know how many CCEs he needs to schedule, so it is done by blind inspection. That is, the RNTI, the UE first sends a random number through the temporary ID assigned by the access side. After accessing the network, the network gives it a temporary identifier RNTI (Radio Network Temporary ID), which is unique to the user in the same cell. Use RNTI to go to the blind detection area, only in the BRESET's CORESET to blind detection based on different levels, first scan by level, not scan, step by step, level 1, level 2, level 4, level 8, level 16. According to the read scheduling information of the RNTI that is read, the scheduling resource is obtained. According to the need to read the content of the information, with the RNTI ID indicating the different channels, such as the system message, the uplink and downlink data transmission scheduling, power control, to match the potential DCI in the CORESET, for example, there is no system message, Is there any data for me, is there any chance of my uplink sending, and there is no immediate access response. All are controlled by various DCI (downstream control indication) in CORESET. The PUCCH is used to transmit uplink L1/L2 control information to support uplink and downlink data transmission. Compared with the PDCCH, the PUCCH carries less information content (only need to tell the gNB not to know the information) Obtaining the downlink scheduling resource is a basic function of the downlink scheduling, and is mainly to obtain resources on the downlink PDSCH. Features of PDSCH resources: In the frequency domain, the bandwidth of the PDSCH is the total bandwidth of the downlink system, and the available bandwidth is determined by the system configuration. In the time domain, the time domain resources in each TTI are time-divisionally shared by the PDSCH and the PDCCH, and the first symbol in each slot is used as the PDCCH resource. S frame, there are 2 symbols GP, and the last 1-2 symbols are used as SRS or PUCCH resources.
- DMRS is used for channel estimation during demodulation Each channel requires a reference signal as a fixed reference. The reference signal can be considered as an accessory to the channel. Any channel has such a reference point, which is distributed among the channels. In 5G, the reference signal distribution of PBCH and PDCCH is exactly the same, and every 4 RE1 reference signals. The difference is that the RS position of the PBCH will change with the modulo 4 of the PCI, so there is a less rigid principle when planning, that is, the modulo 4 problem. The reference signal of the PDSCH needs to be slightly concerned. This channel has two types of RSs, the side peak selects type2, and the frequency domain is full. The two symbols in the time domain are consecutive, in order to be able to send 8 layers. If it is a single symbol, type 2 can send 6 layers, and double type 2 can send 12 layers. Because we want to send 8 layers, we use the double symbol of type2. Type1 and type2 may not be the same in the multiplexed code points. Different layers need different reference signals to distinguish them. ? ? The difference between a single symbol and a double symbol is that RS occupies a few symbols, and it takes two symbols to generate multiple layers. In order to combat the high-speed delay spread, it is necessary to add more reference signals, that is, additional RS, as shown in the figure, generally not. The time-frequency resources occupied by the PDCCH and the DM-RS can no longer be used for data transmission.
- If the cell has no users, the whole cell is very quiet compared to LTE, and it is very quiet, only SSB. For the channel evaluation reference signal, the SSB can also measure the RSRP to do channel estimation, but because the resources are small and the frequency domain is concentrated, the measurement is not accurate. The CSI-RS time domain period can be configured. For the user, it is a dedicated resource. The base station can let the mobile phone continuously evaluate the downlink channel, and send its own CQI, RI, PMI, or CSI (Channel Status Indicator) continuously. Go up and adjust for the base station. CSI is also sent through multiple layers. It is perceived that there are 8 channels in transmission, and 8 are clearly heard. It can be at least 8 layers for multi-stream. If the RS does not have 8 ports, the RI will not recognize 8 layers.
- For NSA, no RMSI is needed. So RMSI overhead is 0 Total REs per slot: 273*12*14