frequency domain resource assignment dci

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NR Downlink Control Information Formats

This example introduces the NR downlink control information (DCI) formats and their definitions, and shows how to use MATLAB® classes to represent DCI formats and encode and decode DCI information bit payloads.

Introduction

NR and LTE use downlink control information (DCI) to send dynamic physical layer control messages from the network to each UE. This information can be system-wide or user-equipment-specific (UE-specific), and contains aspects of uplink and downlink data scheduling, HARQ management, power control, and other signalling. The sidelink uses sidelink control information (SCI) to carry PHY control messages between UEs via a similar mechanism.

NR defines a number of different DCI formats, each serving a different usage, for example, scheduling of PUSCH or PDSCH. Each format specifies an ordered set of bit fields, where each field conveys distinct transmission information, such the frequency resource assignment, time resource assignment, redundancy version, and modulation and coding. The number of bits associated with a field may be fixed, or be dependent on other protocol state, for example, the active BWP size. All the fields map, in order of the format definition, onto a set of information bits, which are then encoded and carried on the physical downlink control channel (PDCCH). The mapping is such that the most significant bit of each field is mapped to the lowest-order information bit for that field. For NR DCI, both padding of zero bits and truncation may be applied to align the payload sizes according to different DCI formats. This size alignment simplifies the blind decoding process and reduces the number of unique payload sizes that have to be searched for.

The fields defined in a format may also depend on the type of RNTI associated with the control information, for example, system information, paging, power control, and user scheduling. This RNTI value scrambles the CRC attached to the information bit payload sent on the PDCCH.

The DCI formats supported by NR Release 16 are:

DCI   Format Usage 0 _ 0 Scheduling   of   PUSCH   in   one   cell 0 _ 1 Scheduling   of   one   or   multiple   PUSCH   in   one   cell,   or   indicating   downlink   feedback   information   for   configured   grant   PUSCH   (CG - DFI) 0 _ 2 Scheduling   of   PUSCH   in   one   cell 1 _ 0 Scheduling   of   PDSCH   in   one   cell 1 _ 1 Scheduling   of   PDSCH   in   one   cell,   and/or   triggering   one   shot   HARQ - ACK   codebook   feedback 1 _ 2 Scheduling   of   PDSCH   in   one   cell 2 _ 0 Notifying   a   group   of   UEs   of   the   slot   format,   available   RB   sets,   COT   duration   and   search   space   set   group   switching 2 _ 1 Notifying   a   group   of   UEs   of   the   PRB(s)   and   OFDM   symbol(s)   where   UE   may   assume   no   transmission   is   intended   for   the   UE 2 _ 2 Transmission   of   TPC   commands   for   PUCCH   and   PUSCH 2 _ 3 Transmission   of   a   group   of   TPC   commands   for   SRS   transmissions   by   one   or   more   UEs 2 _ 4 Notifying   a   group   of   UEs   of   the   PRB(s)   and   OFDM   symbol(s)   where   UE   cancels   the   corresponding   UL   transmission   from   the   UE 2 _ 5 Notifying   the   availability   of   soft   resources   as   defined   in   Clause   9.3.1   of   TS   38.473 2 _ 6 Notifying   the   power   saving   information   outside   DRX   Active   Time   for   one   or   more   UEs 3 _ 0 Scheduling   of   NR   sidelink   in   one   cell 3 _ 1 Scheduling   of   LTE   sidelink   in   one   cell

Representing DCI Formats with MATLAB Classes

MATLAB classes can be used to model DCI formats and fields, where a separate class definition represents each format, and the fields of each format are ordered properties of the class.

In this example, the MATLAB class BitField represents a single DCI field. Each field object has properties to store the field value, current bit size, and a set of possible sizes, which may depend on the protocol state. This class also defines methods to map the field value to and from information bits.

The MATLAB class MessageFormat provides a base class from which to derive specific format classes. Each derived format class defines a set of properties of type BitField for all DCI fields, in the order that they appear for that format. The MessageFormat base class also defines methods to map all derived class DCI fields to and from information bits. Additionally, the MessageFormat class overloads the display, property assignment, and reference functionality to provide easy, direct access to the field values. This class supports optional zero-padding for width alignment, but does not support automatic alignment truncation.

DCI Format 1_0 with CRC Scrambled by SI-RNTI

NR DCI formats often have a large number of fields whose sizes depend on the semi-static UE RRC protocol state. This example uses DCI format 1_0 scrambled by SI-RNTI due to its simple field sequence.

This table describes the ordered fields and bitwidths associated with DCI format 1_0 when the CRC is scrambled by SI-RNTI.

DCI   Format   1 _ 0   field   (SI - RNTI) Size Frequency   domain   resource   assignment ⌈ l o g 2 ⁡ ( N R B D L , B W P ( N R B D L , B W P + 1 ) / 2 ) ⌉ bits,   where N R B D L , B W P is   the   size   of   CORESET   0 Time   domain   resource   assignment 4   bits   as   defined   in   Clause   5.1.2.1   of   TS   38.214 VRB - to - PRB   mapping 1   bit   according   to   TS   38.212   Table   7.3.1.2.2 - 5 Modulation   and   coding   scheme 5   bits   as   defined   in   Clause   5.1.3   of   TS   38.214   Table   5.1.3.1 - 1 Redundancy   version 2   bits   as   defined   in   TS   38.212   Table   7.3.1.1.1 - 2 System   information   indicator   1   bit   as   defined   in   TS   38.212   Table   7.3.1.2.1 - 2 Reserved   bits 17   bits   for   operation   in   a   cell   with   shared   spectrum   channel   access;   otherwise   15   bits

Define a DCIFormat1_0_SIRNTI class for the format by deriving from MessageFormat and specifying a B itField property for each format field. In this format, the first and last fields have bitwidths that depend on protocol state parameters (CORESET 0 size and whether the cell has shared spectrum access) and therefore the field widths are set in the class constructor. This ensures that the bitwidths are sized correctly before using DCIFormat1_0_SIRNTI .

Use DCIFormat1_0_SIRNTI objects to map field values to information bit payloads for this format, and to parse information bits back into field values.

For more information about the NR downlink control channel, see Modeling Downlink Control Information and Downlink Control Processing and Procedures . For more information about applying MATLAB classes, see Representing Structured Data with Classes .

3GPP TS 38.212. "NR; Multiplexing and channel coding (Release 16)." 3rd Generation Partnership Project; Technical Specification Group Radio Access Network .

Related Topics

• Downlink Control Processing and Procedures

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NR PUSCH Resource Allocation and DM-RS and PT-RS Reference Signals

This example shows the time-frequency aspects of the new radio (NR) physical uplink shared channel (PUSCH), the associated demodulation reference signal (DM-RS), and phase tracking reference signal (PT-RS). The example shows how PUSCH resource allocation affects the time-frequency structure of DM-RS and PT-RS.

Introduction

In 5G NR, PUSCH is the physical uplink channel that carries user data. DM-RS and PT-RS are the reference signals associated with PUSCH. DM-RS is used for channel estimation as part of coherent demodulation of PUSCH. To compensate for the common phase error (CPE), 3GPP 5G NR introduced PT-RS. Phase noise produced in local oscillators introduces a significant degradation at mmWave frequencies. It produces CPE and inter-carrier interference (ICI). CPE leads to an identical rotation of a received symbol in each subcarrier. ICI leads to a loss of orthogonality between the subcarriers. PT-RS is used mainly to estimate and minimize the effect of CPE on system performance.

The time-frequency structure of reference signals depends on the type of waveform configured for PUSCH, as defined in TS 38.211 Sections 6.4.1.1 and 6.4.1.2 [1] . When transform precoding is disabled, the waveform configured is cyclic-prefix-orthogonal frequency division multiplexing (CP-OFDM). When transform precoding is enabled, the waveform configured is discrete-fourier-transform-spread orthogonal frequency division multiplexing (DFT-s-OFDM).

The 5G Toolbox™ provides the functions for physical (PHY) layer modeling with varying levels of granularity. The levels of granularity range from PHY channel level functions that perform the transport and physical channel processing to individual channel processing stage functions performing cyclic redundancy check (CRC) coding, code block segmentation, low density parity check (LDPC) channel coding, and so on. The toolbox provides reference signals functionality associated with the PUSCH as functions nrPUSCHDMRS , nrPUSCHDMRSIndices , nrPUSCHPTRS , and nrPUSCHPTRSIndices .

PUSCH is the physical channel that carries the user data. The resources allocated for PUSCH are within the bandwidth part (BWP) of the carrier, as defined in TS 38.214 Section 6.1.2 [2] . The resources in time domain for PUSCH transmission are scheduled by downlink control information (DCI) in the field Time domain resource assignment. This field indicates the slot offset K 0 , starting symbol S , the allocation length L , and the mapping type of PUSCH. The valid combinations of S and L are shown in Table 1.

The resources in the frequency domain for PUSCH transmission are scheduled by a DCI in the field Frequency domain resource assignment . This field indicates whether the resource allocation of resource blocks (RBs) is contiguous or noncontiguous, based on the allocation type. The RBs allocated are within the BWP.

The 5G Toolbox™ provides the nrCarrierConfig and nrPUSCHConfig objects to set the parameters related to the PUSCH within the BWP.

DM-RS for CP-OFDM

DM-RS is used to estimate the radio channel. DM-RS is present only in the RBs scheduled for PUSCH. The DM-RS structure is designed to support different deployment scenarios and use cases.

Parameters That Control Time Resources

The parameters that control the time resources of DM-RS are:

PUSCH symbol allocation

Mapping type

Intra-slot frequency hopping

DM-RS type A position

DM-RS length

DM-RS additional position

Symbol allocation of PUSCH indicates the OFDM symbol locations allocated for the PUSCH transmission in a slot. The mapping type indicates the first DM-RS OFDM symbol location and the duration of OFDM symbols ( l d ). For mapping type A, l d is the duration between the first OFDM symbol of the slot and the last OFDM symbol of the allocated PUSCH resources. For mapping type B, l d is the duration of the allocated PUSCH resources. When intra-slot frequency hopping is enabled, l d is the duration per hop. The DM-RS symbols are present in each hop when intra-slot frequency hopping is enabled. When intra-slot frequency hopping is enabled, DM-RS is single-symbol with the maximum number of additional positions either 0 or 1. The DM-RS symbol locations is given by TS 38.211 Tables 6.4.1.1.3-3, 6.4.1.1.3-4, and 6.4.1.1.3-6. Figure 1 shows the DM-RS symbol locations for PUSCH occupying 14 symbols with PUSCH mapping type A, intra-slot frequency hopping enabled, and number of DM-RS additional positions as 1. The figure shows DM-RS is present in each hop. The locations of DM-RS symbols in each hop depends on the number of OFDM symbols allocated for PUSCH in each hop.

For details on other DM-RS parameters, see NR PDSCH Resource Allocation and DM-RS and PT-RS Reference Signals .

Parameters That Control Frequency Resources

The parameters that control the frequency resources of DM-RS are:

DM-RS configuration type

DM-RS antenna ports

The configuration type indicates the frequency density of DM-RS and is signaled by the RRC message dmrs-Type . Configuration type 1 defines six subcarriers per physical resource block (PRB) per antenna port, comprising alternate subcarriers. Configuration type 2 defines four subcarriers per PRB per antenna port, consisting of two groups of two consecutive subcarriers. Different delta shifts are applied to the sets of subcarriers used, depending on the associated antenna port or code division multiplexing (CDM) group. For configuration type 1, there are two possible CDM groups/shifts across eight possible antenna ports (p=0...7). For configuration type 2, there are three possible CDM groups/shifts across twelve antenna ports (p=0...11). For more details, see NR PDSCH Resource Allocation and DM-RS and PT-RS Reference Signals .

In the case of codebook-based PUSCH processing, the union of DM-RS subcarrier locations present in each layer are projected to all the antenna ports.

Sequence Generation

The pseudorandom sequence used for DM-RS is 2 31 - 1 length gold sequence. The sequence is generated across all the common resource blocks (CRBs) and is transmitted only in the RBs allocated for data because the sequence is not required to estimate the channel outside the frequency region in which data is not transmitted. Generating the reference signal sequence across all the CRBs ensures that the same underlying pseudorandom sequence is used for multiple UEs on overlapping time-frequency resources in the case of a multi-user MIMO. The parameters that control the sequence generation are:

DM-RS scrambling identity ( N ID n SCID )

DM-RS scrambling initialization ( n SCID )

Number of OFDM symbols in a slot

Slot number in a radio frame

DM-RS symbol locations

PRBs allocation

The CyclicPrefix property of the carrier object controls the number of OFDM symbols in a slot. The NSlot property of the carrier object controls the slot number.

In the case of codebook-based PUSCH processing, the sequence is multiplied with a precoder matrix, which depends on the number of layers, number of antenna ports, and the transmitted precoder matrix indicator (TPMI).

PT-RS for CP-OFDM

PT-RS is the phase tracking reference signal. PT-RS is used mainly to estimate and minimize the effect of CPE on system performance. Due to the phase noise properties, the PT-RS signal has low density in the frequency domain and high density in the time domain. PT-RS always occurs in combination with DM-RS and only when the network has configured PT-RS to be present.

PT-RS is configured through the higher layer parameter DMRS-UplinkConfig for uplink. The parameters that control the time resources of PT-RS are:

Time density of PT-RS ( L PT - RS )

L PT - RS depends on the scheduled modulation and coding scheme. The value must be one of {1, 2, 4}. For the parameters that control DM-RS symbol locations, refer to Parameters that Control DM-RS Time Resources (CP-OFDM) .

PT-RS occupies only one subcarrier in an RB for one OFDM symbol. The parameters that control the frequency resources of PT-RS are:

PRB allocation

Frequency density of PT-RS ( K PT - RS )

Radio network temporary identifier ( n RNTI )

Resource element offset

PT-RS antenna ports

K PT - RS depends on the scheduled bandwidth. The value is either 2 or 4. The value indicates whether PT-RS is present in every two RBs or every four RBs.

For more details, see NR PDSCH Resource Allocation and DM-RS and PT-RS Reference Signals .

The sequence used for generating PT-RS is the same pseudorandom sequence used for the DM-RS sequence generation. In the absence of intra-slot frequency hopping, the values of PT-RS sequence depend on the first DM-RS symbol position. In the presence of intra-slot frequency hopping, the values of PT-RS sequence depend on first DM-RS symbol positions in each hop. For more details, refer the section DM-RS Sequence Generation (CP-OFDM) .

Generate the resource element (RE) indices of PUSCH, DM-RS, and PT-RS. Also, generate DM-RS and PT-RS symbols.

Map PUSCH, DM-RS, and PT-RS RE indices to the grid with scaled values to visualize the respective locations on the grid.

In the preceding figure, PT-RS is located from the start of the OFDM symbol in the physical uplink shared channel allocation. The symbols are present at every L PT - RS hop interval from each other or from DM-RS symbols. The difference in consecutive subcarrier locations of PT-RS is 24, which is the number of subcarriers in an RB (12) times the frequency density of PT-RS (2).

DM-RS for DFT-s-OFDM

DFT-s-OFDM supports only single layer transmission and is primarily used for low coverage scenarios. The time-frequency resources of DM-RS in DFT-s-OFDM are structured in a way to achieve low cubic metric and high power amplifier efficiency. The transmission of a reference signal frequency multiplexed with other uplink data transmissions highly impacts the power amplifier efficiency due to the increased cubic metric. The reference signals are time-multiplexed with uplink transmissions, thereby blocking all the resource elements for data transmission in the OFDM symbols carrying DM-RS.

The parameters that control the time resources of DM-RS in DFT-s-OFDM are:

These parameters are the same parameters that control the time resources of DM-RS in CP-OFDM. For more details, refer to Parameters that Control DM-RS Time Resources (CP-OFDM) .

The parameters that control the frequency resources of DM-RS in DFT-s-OFDM are:

DM-RS antenna port

These two parameters are the same as the parameters of CP-OFDM. The DM-RS configuration type is always set to 1. The DM-RS antenna port is nominally a scalar with value 0.

There is no need to support multi-user MIMO situations because DFT-s-OFDM is for coverage-limited scenarios. With no MIMO situations, the reference signal is generated only for the transmitted PRBs rather than CRBs as in OFDM. Due to the single layer and single configuration type allowed in DFT-s-OFDM, the number of subcarrier locations used for DM-RS in an RB is constant. Figure 2 illustrates the DM-RS subcarrier locations in DFT-s-OFDM for mapping type A with OFDM symbols allocated for PUSCH spanning over the complete slot.

The DM-RS sequence is the ZadoffChu sequence in DFT-s-OFDM. The orthogonal sequences are generated with different cyclic shifts for a group number and sequence number. The parameters that control the sequence generation are:

Group hopping

Sequence hopping

DM-RS scrambling identity ( N ID RS )

The subcarrier locations in the OFDM symbols occupying DM-RS are not allocated for PUSCH.

PT-RS for DFT-s-OFDM

PT-RS in DFT-s-OFDM is inserted with data in the transform precoding stage.

The parameters that control the time resources of PT-RS in DFT-s-OFDM are same as the parameters that control the time resources of PT-RS in CP-OFDM. The value of L PT - RS is either 1 or 2 in DFT-s-OFDM. For more details, refer to Parameters that Control PT-RS Time Resources (CP-OFDM) .

The PT-RS pattern in the frequency domain is quite different from CP-OFDM. The PT-RS samples are inserted as chunks or groups ( N group PT - RS ). Each group consists of a finite number of samples ( N samp group ) in the scheduled bandwidth for each OFDM symbol where PT-RS is present.

The parameters that control the frequency resources of PT-RS in DFT-s-OFDM are:

Number of PT-RS samples in a group ( N samp group )

Number of PT-RS groups ( N group PT - RS )

The valid combinations of PT-RS sample density ([ N samp group N group PT - RS ]) are {[2 2], [2 4], [4 2], [4 4], [4 8]}. The number of PT-RS samples in an OFDM symbol is fixed in DFT-s-OFDM, based on the number of PT-RS samples in all the PT-RS groups. This number is different from CP-OFDM in which the number of PT-RS samples increase based on the number of RBs in PUSCH.

Figure 3 shows the subcarrier locations of PT-RS symbols for an RB with the number of PT-RS samples set to 2 and the number of PT-RS groups set to 2 for an OFDM symbol carrying PT-RS.

PT-RS sample density [2 2] implies that there are two PT-RS groups in a scheduled bandwidth with two symbols each.

PT-RS is inserted with layered symbols at the input of transform precoding. After transform precoding, both layered symbols and PT-RS are treated as data. Therefore, the PT-RS is not visible in the grid directly.

The PT-RS sequence in DFT-s-OFDM is a modified pi/2-BPSK sequence. The parameters that control the sequence generation are:

Starting OFDM symbol of PUSCH allocation

PT-RS scrambling identity ( N ID )

PT-RS subcarrier locations

Generate PUSCH and PT-RS RE indices.

Set PUSCH and PT-RS resource elements to constant values.

Plot PT-RS projections onto the grid.

Further Exploration

You can try changing the parameters that affect the time and frequency resources of reference signals and observe the variations in the RE positions for the respective signals.

Try changing the number of antenna ports configured for DM-RS and PT-RS, then observe the variations of reference signals and data across the ports. For example, try to configure DM-RS for two antenna ports 0 and 2, configuration type 1, and PT-RS for antenna port 0. Generate the PUSCH indices, DM-RS signal (indices and symbols), and PT-RS signal (indices and symbols). Map them to a grid and visualize the grid for both the ports.

Try performing channel estimation and phase tracking using the PT-RS symbols and indices. Compute the throughput by following the steps outlined in NR PUSCH Throughput .

This example shows how to generate the DM-RS and PT-RS sequences and how to map the sequences to the OFDM carrier resource grid. It highlights the properties that control the time-frequency structure of reference signals for different waveforms. For example, the time-frequency pattern for reference signals in CP-OFDM and DFT-s-OFDM and the variation in the sequences generated for reference signals in different waveforms.

3GPP TS 38.211. "NR; Physical channels and modulation" 3rd Generation Partnership Project; Technical Specification Group Radio Access Network .

3GPP TS 38.214. "NR; Physical layer procedures for data" 3rd Generation Partnership Project; Technical Specification Group Radio Access Network .

3GPP TS 38.212. "NR; Multiplexing and channel coding" 3rd Generation Partnership Project; Technical Specification Group Radio Access Network .

Local Functions

• nrPUSCHDMRS | nrPUSCHDMRSIndices | nrPUSCHPTRS | nrPUSCHPTRSIndices | nrPUSCHIndices
• nrPUSCHConfig | nrCarrierConfig

Related Topics

• NR PDSCH Resource Allocation and DM-RS and PT-RS Reference Signals

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PDCCH order in 5G NR

• 5G MAC Layer , 5G NR RACH , 5G Physical Layer , 5G-NR

PDCCH order in 5G NR is a way of network instructing the UE to trigger a Random access Procedure . Typically RACH is triggered by UE and there are a number of reasons why RACH can be triggered by UE. But the network can force the UE to trigger RACH when it detects that UE is out-of-sync in Downlink. So in that scenario, the network triggers a PDCCH order by sending a DCI Format 1_0 on the SSB beam index UE is camped along with a PRACH preamble and RACH occasion.

PDCCH order is one of the reasons for RACH trigger in both LTE and 5G-NR. If the network detects that there is DL Data to be sent to UE in its MAC Buffer and there is a UL synchronization issue due to the expiry of the Time Alignment timer at UE, then the network triggers a PDCCH order in order to re-synchronize with the UE.

If UE is configured with two or more Uplink secondary Carriers then 3GPP specifies that the Random Access procedure on an SCell shall only be initiated by a PDCCH order with ra-PreambleIndex different from 0b000000.

If there was an ongoing Random Access procedure that is triggered by a PDCCH order while the UE receives another PDCCH order indicating the same Random Access Preamble, PRACH mask index, and uplink carrier, the Random Access procedure is considered as the same Random Access procedure as the ongoing one and not initialized again.

• Network detects UE is Out of Sync
• Network sends PDCCH order to UE with dedicated RACH premable
• PDCCH order is sent via DCI Format 1_0 with C-RNTI CRC scrambled , containing SSB index, ra-PreambleIndex  and  PRACH Mask Index
• In the Case of 2-step RACH procedure PDCCH order contains, containing SSB index, ra-PreambleIndex  and msgA-SSB-SharedRO-MaskIndex.
• UE triggers RACH procedure with the information received
• If no dedicated RACH premamble was sent by network then UE will trigger CFRA procedure and send C-RNTI MAC CE in msg3 for contention resolution
• UE Completes RACH procedure
• Network Reconfigures all the IE’s to UE.

DCI Format 1_0 is typically used for scheduling PDSCH to a UE in a cell, DCI format 1_0  can be  CRC scrambled by C-RNTI or CSRNTI or MCS-C-RNTI or P-RNTI or SI-RNTI or RA-RNTI. For DCI Format 1_0 CRC Scrambled by C-RNTI this can be used for normal PDSCH Scheduling by the UE. When PDCCH order is triggered with C-RNTI the network sets the Field “ Frequency-domain resource assignment ” in DCI with all ones.

When UE decodes the DCI Format1_0 with CRC scrambled by C-RNTI and the “Frequency domain resource assignment” field are of all ones, the DCI format 1_0 is for random access procedure initiated by a PDCCH order

UE then decodes below DCI Format 1_0 Fields

Random Access Preamble index: This field contains 6 bits. It indicates which Random access preamble to use in case of Contention Free Random Access(CFRA)  or the value 000000 in the case of  Contention based Random Access(CBRA) procedure. If the Preamble index bit is set as ‘0’ then the UE will trigger a contention-based random access procedure or else if the Preamble index is >0 then UE will trigger a Contention-free Random access procedure. Non-zero values are used to allocate the dedicated Prach index (0 to 63) to the UE.

UL/SUL indicator: This field contains 1 bit. If the UE is configured with supplementaryUplink in ServingCellConfig in the cell, this field indicates which UL carrier in the cell to transmit the PRACH according. The Below table indicates the Value of UL/SUL indicator.

SS/PBCH index : This field contains 6 bits. This field indicates the SS/PBCH that shall be used to determine the RACH occasion for the PRACH transmission.

PRACH Mask index: This field contains 4 bits. If the value of the “Random Access Preamble index” is not all zeros, this field indicates the RACH occasion associated with the SS/PBCH indicated by “SS/PBCH index” for the PRACH transmission. PRACH Mask index is applicable if the preamble index bit is not ‘0’ i.e a dedicated Preamble index has been assigned by the network to the UE.

The Below table indicates the PRACH Mask index values.

• A value of 0 indicates all PRACH ocassions are available
• A value of 1 to 8 indeicates PRACH ocassions 1 to 8 are available
• A value of 9 indicates even PRACH ocassions are available
• A value of 10 indicates even PRACH ocassions are available

Reserved bits : 12 bits for operation in a cell with shared spectrum channel access; otherwise 10 bits.

References :

• 3GPP TS 38.321 NR; Medium Access Control (MAC) protocol specification
• 3GPP TS 38.214 NR; Physical layer procedures for data

Further reading

5g : handling of measurement gaps, 5g nr cell scan and rach procedure poster.

5G and Beyond pp 259–301 Cite as

NR Physical Layer Overview

• Daniel Chen Larsson 3  
• First Online: 26 March 2021

2592 Accesses

1 Citations

The physical layer of NR is designed to support a large set of use cases from day one and operate tightly with Long Term Evolution (LTE). In addition, NR is designed so that new use case and design can be added on in later releases. It is further designed to support performances in terms of throughputs, latency, energy efficiency, deployment flexibility and different spectrums. NR shares some basics with LTE. NR is, however, designed to support a larger spectrum range and wider carriers than LTE. NR supports spectrum ranges from around 500 MHz to up to 52.6 GHz in its first release, and work is being done to expand this beyond 52.6 GHz. When it comes to data rate and particularly latency, NR has taken a large step compared to LTE. All of this will enable and grow the current use cases used by cellular technology. By that, the design of NR will support the general technology development during the 2020 decade and 2030 decade, wherein connectivity is a key enabler for all sorts of applications and uses.

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TS 38.101, NR; User Equipment (UE) radio transmission and reception

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Daniel Chen Larsson

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Ericsson, Santa Clara, CA, USA

Xingqin Lin

Pohang University of Science and Technology (POSTECH), Pohang, Korea (Republic of)

Namyoon Lee

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Larsson, D.C. (2021). NR Physical Layer Overview. In: Lin, X., Lee, N. (eds) 5G and Beyond. Springer, Cham. https://doi.org/10.1007/978-3-030-58197-8_9

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Everything about Cloud, Core, Fiber and RAN

PDCCH Order – Network Initiated RACH in New 5G

Introduction.

In 5G NR, PDCCH order is a mechanism using which gNB can force the UE to trigger the RACH procedure. There are  number of reason why UE can triggered the RACH and PDCCH Order is one of them. gNB take PDCCH Order decision when it detect the UE is out-of-sync in Downlink and Downlink data is available for the UE.

In out-of-sync scenario, the gNB triggers a PDCCH order by sending a DCI Format 1_0 on the SSB beam index UE is camped along with a PRACH preamble and RACH occasion. If the gNB find that there is DL Data to be sent to UE in its MAC Buffer and there is a UL synchronization issue due to the expiry of the Time Alignment timer at UE, then the gNB triggers a PDCCH order in order to re-synchronize with the UE.

Telco sought  Key Pointers

• PDCCH order mechanism is available in both LTE and 5G-NR
• gNB triggers a PDCCH order by sending a DCI Format 1_0 on the SSB beam index UE is camped
• When UE is configured with two or more Uplink secondary Carriers then 3GPP specifies that the Random Access procedure on an SCell shall only be initiated by a PDCCH order with ra-PreambleIndex  different from 0b000000
• When there is an ongoing RACH procedure triggered by a PDCCH order while the UE receives another PDCCH order indicating the same RACH Preamble, PRACH mask index , and uplink carrier, the RACH procedure is considered as the same RACH procedure as the ongoing one and not initialized again

PDDCH Order Call Flow Sequence

• gNB detects UE is Out-of-Sync
• gNB sends PDCCH order to UE with dedicated RACH premable
• PDCCH order is sent via DCI Format 1_0 with C-RNTI CRC scrambled, containing SSB index , ra-PreambleIndex  and  PRACH Mask Index
• In the Case of  2-step RACH procedure  PDCCH order contains, containing SSB index,  ra-PreambleIndex  and msgA-SSB-SharedRO-MaskIndex
• UE triggers RACH procedure with the information received
• If no dedicated RACH preamble was sent by network then UE will trigger CFRA procedure and send C-RNTI MAC CE in msg3 for contention resolution
• UE Completes RACH procedure
• Now gNB Reconfigures all the IE’s to UE
• DCI Format 1_0: It is typically used to schedule PDSCH to the UE, DCI format 1_0   can be  CRC scrambled by C-RNTI or CSRNTI or MCS-C-RNTI or P-RNTI or SI-RNTI or RA-RNTI. For DCI Format 1_0 CRC Scrambled by C-RNTI this can be used for normal PDSCH Scheduling by the UE. When PDCCH order is triggered with C-RNTI the network sets the Field “ Frequency-domain resource assignment ” in DCI with all ones. When UE decodes the DCI Format 1_0 with CRC scrambled by C-RNTI and the “ Frequency domain resource assignment ” field are of all ones, the DCI format 1_0 is for random access procedure initiated by a PDCCH order UE then decodes below DCI Format 1_0 Fields
• Random Access Preamble index:  This field contains 6 bits . It indicates which RACH preamble to use in case of Contention Free Random Access (CFRA)   or the value 000000 in the case of  Contention based Random Access (CBRA) procedure. If the Preamble index bit is set as ‘0’ then the UE will trigger a contention-based random access procedure or else if the Preamble index is >0 then UE will trigger a Contention-free RACH procedure. Non-zero values are used to allocate the dedicated Prach index (0 to 63) to the UE.
• UL/SUL indicator: This field contains 1 bit . If the UE is configured with supplementaryUplink   in ServingCellConfig in the cell, this field indicates which UL carrier in the cell to transmit the PRACH according. The Below table indicates the Value of UL/SUL indicator.
• SS/PBCH index : This field contains 6 bits . This field indicates the SS/PBCH that shall be used to determine the RACH occasion for the PRACH transmission.
• PRACH Mask index: This field contains 4 bits . If the value of the “Random Access Preamble index” is not all zeros, this field indicates the RACH occasion associated with the SS/PBCH indicated by “ SS/PBCH index ” for the PRACH transmission. PRACH Mask index is applicable if the preamble index bit is not ‘0’ i.e. a dedicated Preamble index has been assigned by the network to the UE.
• Reserved bits : 12 bits for operation in a cell with shared spectrum channel access ; otherwise 10 bits.

References :

• 3GPP TS 38.321 NR; Medium Access Control (MAC) protocol specification
• 3GPP TS 38.214 NR; Physical layer procedures for data

Related Posts:

• 5G NR Beam Failure Recovery – BFR
• SSB Based and CSI-RS Based RLM in 5G
• 5G NR RRC State Transitions 
• 5G NR RRC Timers, Counter and Constants

Tags: 5G NR Layer 2 Layer 2 MAC PDCCH Order RACH Procedure

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NR channels 38.211

Physical channels, reference signals, physical uplink control channel, downlink control information (dci), dci format 0_0 for pusch, dci format 0_1 for pusch, dci format 1_0 for pdsch with crc scrambled by c-rnti, dci format 1_0 for pdsch with crc scrambled by p-rnti, dci format 1_0 for pdsch with crc scrambled by si-rnti, dci format 1_0 for pdsch with crc scrambled by ra-rnti, dci format 1_1 for pdsch, dci format 2_0 for notifying the slot format, dci format 2_1 for pre-emption prbs, dci format 2_2 for tpc commands for pucch and pusch, dci format 2_3 for tpc command for group of tpc commands for srs.

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NR PDSCH Resource Allocation and DM-RS and PT-RS Reference Signals

This example shows the time-frequency aspects of the new radio (NR) physical downlink shared channel (PDSCH), the associated demodulation reference signal (DM-RS), and phase tracking reference signal (PT-RS). The example shows how PDSCH resource allocation affects the time-frequency structure of DM-RS and PT-RS.

Introduction

In 5G NR, PDSCH is the physical downlink channel that carries user data. DM-RS and PT-RS are the reference signals associated with PDSCH. These signals are generated within the PDSCH allocation, as defined in TS 38.211 Sections 7.4.1.1 and 7.4.1.2 [1] . DM-RS is used for channel estimation as part of coherent demodulation of PDSCH. To compensate for the common phase error (CPE), 3GPP 5G NR introduced PT-RS. Phase noise produced in local oscillators introduces a significant degradation at mmWave frequencies. It produces CPE and inter-carrier interference (ICI). CPE leads to an identical rotation of a received symbol in each subcarrier. ICI leads to loss of orthogonality between the subcarriers. PT-RS is used mainly to estimate and minimize the effect of CPE on system performance.

The 5G Toolbox™ provides the functions for physical (PHY) layer modeling with varying levels of granularity. The levels of granularity range from PHY channel level functions that perform the transport and physical channel processing to individual channel processing stage functions performing cyclic redundancy check (CRC) coding, code block segmentation, low density parity check (LDPC) channel coding, and so on. The toolbox offers the reference signals functionality associated with the PDSCH as functions nrPDSCHDMRS , nrPDSCHDMRSIndices , nrPDSCHPTRS , and nrPDSCHPTRSIndices .

PDSCH is the physical channel that carries the user data. The resources allocated for PDSCH are within the bandwidth part (BWP) of the carrier, as defined in TS 38.214 Section 5.1.2 [2] . The resources in the time domain for PDSCH transmission are scheduled by downlink control information (DCI) in the field Time domain resource assignment. This field indicates the slot offset K 0 , starting symbol S , the allocation length L , and the mapping type of PDSCH. The valid combinations of S and L are shown in Table 1. For mapping type A, value of S is 3 only when the DM-RS type A position is set to 3.

The resources in the frequency domain for PDSCH transmission are scheduled by a DCI in the field Frequency domain resource assignment . This field indicates whether the resource allocation of resource blocks (RBs) is contiguous or noncontiguous, based on the allocation type. The RBs allocated are within the BWP.

The 5G Toolbox™ provides the nrCarrierConfig and nrPDSCHConfig objects to set the parameters related to the PDSCH within the BWP.

DM-RS is used to estimate the radio channel. The signal is present only in the RBs allocated for the PDSCH. The DM-RS structure is designed to support different deployment scenarios and use cases. A front-loaded design supports low-latency transmissions, twelve orthogonal antenna ports for MIMO transmissions, and up to four reference signal transmission instances in a slot to support high-speed scenarios. The front-loaded reference signals indicate that the signal occurs early in the transmission. The DM-RS is present in each RB allocated for PDSCH.

Parameters That Control Time Domain Resources

The parameters that control DM-RS OFDM symbol locations are:

PDSCH symbol allocation

Mapping type

DM-RS type A position

DM-RS length

DM-RS additional position

The symbol allocation of PDSCH indicates the OFDM symbol locations used by the PDSCH transmission in a slot. DM-RS symbol locations lie within the PDSCH symbol allocation. The positions of DM-RS OFDM symbols depend on the mapping type. The mapping type of PDSCH is either slot-wise (type A) or non-slot-wise (type B). The positions of any additional DM-RS symbols are defined by a set of tables, as specified in TS 38.211 Section 7.4.1.1.2 [1] . For the purpose of indexing the tables, the specification defines the term l d indicating the duration of OFDM symbols to be accounted for, depending on the mapping type.

For mapping type A, the DM-RS OFDM symbol locations are defined relative to the first OFDM symbol of the slot (symbol #0). The location of first DM-RS OFDM symbol ( l 0 ) is provided by the DM-RS type A position, which is either 2 or 3. For any additional DM-RS, the duration of OFDM symbols ( l d ) is the number of OFDM symbols between the first OFDM symbol of the slot (symbol #0) and the last OFDM symbol of the allocated PDSCH resources. Note that l d may differ from the number of OFDM symbols allocated for PDSCH, when the first OFDM symbol of PDSCH is other than symbol #0.

For mapping type B, the DM-RS OFDM symbol locations are defined relative to the first OFDM symbol of allocated PDSCH resources. The location of first DM-RS OFDM symbol ( l 0 ) is always 0, meaning that the first DM-RS OFDM symbol location is the first OFDM symbol location of the allocated PDSCH resources. For any additional DM-RS, the duration of OFDM symbols ( l d ) is the duration of the allocated PDSCH resources.

Figure 1 illustrates the DM-RS symbol locations depending on the mapping type for an RB within a slot, having single-symbol DM-RS. The figure shows a configuration with PDSCH occupying the OFDM symbols from 1 to 10 (0-based) with l d equal to 11 for mapping type A, and from 3 to 9 (0-based) with l d equal to 7 for mapping type B respectively.

The maximum number of DM-RS OFDM symbols used by a UE is configured by RRC signaling ( dmrs-AdditionalPosition and maxLength ). The maxLength RRC parameter configures the length of DM-RS symbol, single symbol DM-RS or double symbol DM-RS. For double-symbol DM-RS, the actual selection is signaled in the DCI format 1_1 message. Figure 2 illustrates the single-symbol and double-symbol DM-RS locations.

The higher-layer parameter dmrs-AdditionalPosition defines the maximum number of additional single- or double-symbol DM-RS transmitted. The number of additional positions is in the range of 0 to 3 and depends on the mapping type, DM-RS length, and PDSCH symbol allocation. The DM-RS symbol locations are given by TS 38.211 Tables 7.4.1.1.2-3, and 7.4.1.1.2-4. Figure 3 illustrates the DM-RS additional positions in combination with single-symbol and double-symbol DM-RS.

Parameters That Control Frequency Domain Resources

The parameters that control the subcarrier locations of DM-RS are:

DM-RS configuration type

DM-RS antenna ports

The configuration type indicates the frequency density of DM-RS and is signaled by RRC message dmrs-Type . Configuration type 1 defines six subcarriers per physical resource block (PRB) per antenna port, comprising alternate subcarriers. Configuration type 2 defines four subcarriers per PRB per antenna port, consisting of two groups of two consecutive subcarriers. Figure 4 indicates the DM-RS subcarrier locations based on configuration type.

Different delta shifts are applied to the sets of subcarriers used, depending on the associated antenna port or code division multiplexing (CDM) group. For configuration type 1, there are two possible CDM groups/shifts across eight possible antenna ports (p=0...7). Figure 5 illustrates the different shifts associated for DM-RS subcarrier locations with the DM-RS configuration type set to 1. Notice that the resource elements (REs) corresponding to the DM-RS subcarrier locations of lower CDM group (i.e. antenna port 0) are blocked for data transmission in the antenna ports of higher CDM group (i.e. antenna port 2).

For configuration type 2, there are three possible CDM groups/shifts across twelve antenna ports (p=0...11). Figure 6 illustrates the different shifts associated with DM-RS subcarrier locations in DM-RS configuration type 2. For full configuration details, see TS 38.211 Section 7.4.1.1. Notice that the REs corresponding to the DM-RS subcarrier locations of lower CDM groups are blocked for data transmission in the antenna ports of higher CDM groups.

Sequence Generation

The pseudorandom sequence used for DM-RS is 2 31 - 1 length gold sequence. The sequence is generated across all the common resource blocks (CRBs) and is transmitted only in the RBs allocated for data because it is not required to estimate the channel outside the frequency region in which data is not transmitted. Generating the reference signal sequence across all the CRBs ensures that the same underlying pseudorandom sequence is used for multiple UEs on overlapping time-frequency resources in the case of a multi-user MIMO. The parameters that control the sequence generation are:

DM-RS scrambling identity ( N ID n SCID )

DM-RS scrambling initialization ( n SCID )

Number of OFDM symbols in a slot

Slot number in a radio frame

DM-RS symbol locations

PRBs allocation

The CyclicPrefix property of the carrier object controls the number of OFDM symbols in a slot. The NSlot property of the carrier object controls the slot number.

PT-RS is the phase tracking reference signal. PT-RS is used mainly to estimate and minimize the effect of CPE on system performance. Due to the phase noise properties, PT-RS signal has a low density in the frequency domain and a high density in the time domain. PT-RS always occurs in combination with DM-RS and only when the network has configured PT-RS to be present.

PT-RS is configured through the higher layer parameter DMRS-DownlinkConfig for downlink. The parameters that control the time resources of PT-RS are:

Time density of PT-RS ( L PT - RS )

L PT - RS depends on the scheduled modulation and coding scheme. Value of L PT - RS must be from the set {1, 2, 4}. For the parameters that control DM-RS symbol locations, refer to Parameters that Control DM-RS Time Resources .

The PT-RS symbol locations in a slot start from the first OFDM symbol in the shared channel allocation and hop every L PT - RS symbols, if no DM-RS symbol is present in this interval. In the case where a DM-RS symbol or symbols are present in between or at the hop interval, the hop starts from the last DM-RS symbol location to provide the next PT-RS symbol. Figure 7 shows the PT-RS symbol locations in an RB for single slot with time-density set to 4 and DM-RS symbol locations set to 2 and 11 (0-based).

PT-RS occupies only one subcarrier in an RB for one OFDM symbol. The parameters that control the frequency resources of PT-RS are:

PRB allocation

Frequency density of PT-RS ( K PT - RS )

Radio network temporary identifier ( n RNTI )

Resource element offset

PT-RS antenna port

K PT - RS depends on the scheduled bandwidth. The value of K PT - RS is either 2 or 4, which indicates whether PT-RS is present in every two RBs or every four RBs.

The starting RB at which PT-RS is present ( k ref RB ), depends on K PT - RS , n RNTI , and the number of RBs ( N RB ) allocated for PDSCH. For the purpose of mapping PT-RS, all the RBs of PDSCH are numbered in increasing order from 0 to N RB - 1 . The subcarrier location of PT-RS ( k ref RE ) within a resource block depends on the DM-RS configuration type, resource element (RE) offset, and PT-RS antenna port. The PT-RS antenna port must be a subset of DM-RS antenna ports. The PT-RS subcarrier location always aligns with one of the DM-RS subcarrier locations in an RB.

PT-RS in an RB occupies the same subcarrier locations in all the OFDM symbols where PT-RS is present.

The sequence used to generate PT-RS is the same pseudorandom sequence used for DM-RS sequence generation. The values of the PT-RS sequence depend on the position of the first DM-RS symbol. For more details, refer to DM-RS sequence generation .

Get DM-RS symbols, RE indices of PDSCH, and DM-RS.

Map PDSCH, DM-RS, and PT-RS RE indices to the grid with scaled values to visualize the respective locations on the grid.

In the preceding figure, PT-RS is located at the start of the OFDM symbol in the PDSCH allocation. The symbols are present at every L PT - RS hop interval from each other or from DM-RS symbols. PT-RS symbols in the frequency domain are located at subcarrier 19 (first RB) and at subcarrier 43 (third RB) of each OFDM symbol where PT-RS is present. The difference in consecutive subcarrier locations of PT-RS is 24, which is the number of subcarriers in an RB (12) times the frequency density of PT-RS (2).

Further Exploration

You can try changing the parameters that affect the time and frequency resources of reference signals and observe the variations in the RE positions for the respective signals.

Try performing channel estimation and phase tracking by using the reference signals. Compute the throughput by following the steps outlined in NR PDSCH Throughput .

This example shows how to generate the DM-RS and PT-RS sequences, and how to map the sequences to the OFDM carrier resource grid. It highlights the properties that control the time-frequency structure of reference signals.

3GPP TS 38.211. "NR; Physical channels and modulation" 3rd Generation Partnership Project; Technical Specification Group Radio Access Network .

3GPP TS 38.214. "NR; Physical layer procedures for data" 3rd Generation Partnership Project; Technical Specification Group Radio Access Network .

3GPP TS 38.212. "NR; Multiplexing and channel coding" 3rd Generation Partnership Project; Technical Specification Group Radio Access Network .

• nrPDSCHIndices | nrPDSCHDMRSIndices | nrPDSCHDMRS | nrPDSCHPTRSIndices | nrPDSCHPTRS
• nrCarrierConfig | nrPDSCHConfig

Related Topics

• NR PUSCH Resource Allocation and DM-RS and PT-RS Reference Signals

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Resource Allocation in Time Domain and Ack/Nack Response Timing

As in LTE, in NR as well Resource Allocation should be defined both in Time domain and Frequency Domain. In LTE, we didn't care much about the time domain resource allocation since they are assigned by a fixed/predefined rule, but in NR the time domain resource allocation is determined by much more complicated rule than in LTE whereas freuqency domain resource allocation is almost same as in LTE.

Following is the list of topics related to the resource allocation in Time Domain.

PDSCH - Time Domain Allocation (DCI - PDSCH Timing) : K0

Pdsch - ack/nack timing : k1, pusch - time domain allocation : k2, ue pdsch processing procedure time : n1.

• UE PUSCH preparation procedure time : N2

As mentioned above, frequency domain resource allocation is very similar to LTE. Mainly determined by bitmap or RIV depending of Resource Allocation Type. This part will be described in a separate page titled Resource Allocation Type .

Following is the illustration showing the Time Domain resource allocation for PDSCH based on 38.214 - 5.1.2.1 Resource allocation in time domain. When the subcarrier spacing of PDSCH and PDCCH is different, the time delay between DCI slot and PDSCH slot is a little bit complicated as shown below, but when the subcarrier spacing of PDSCH and PDCCH is same the time delay between DCI slot and PDSCH slot becomes K0.

NOTE : In most case, we configure that PDSCH subcarrier spacing is same as PDCCH subcarrier spacing, so you can say K0 = Time Delay between DCI slot and PDSCH slot  

Following is the RRC parameters determining k0. SLIV determination is a pretty complicated process. so I created a separate page for this, refer to this page .  PDSCH-TimeDomainResourceAllocation is an IE(Information Element) of PDSCH-Config and PDSCH-ConfigCommon . It is defined as an element (a kind of array element) of an IE called pdsch-AllocationList.  Once this array(pdsch-AllocationList) is defined in RRC message, which elements of the array is used for each PDSCH scheduling is determined by the field called Time domain resource assignment in DCI 1_0 and DCI 1_1 .

PDSCH-TimeDomainResourceAllocation ::= SEQUENCE {

   k0                                  INTEGER(0..32)        OPTIONAL, -- Need S

   mappingType                         ENUMERATED {typeA, typeB},

   startSymbolAndLength                INTEGER (0..127)  // SLIV

PDSCH-TimeDomainResourceAllocation-r16 ::= SEQUENCE {

   k0-r16                                  INTEGER(0..32) OPTIONAL, -- Need S

   mappingType-r16                   ENUMERATED {typeA, typeB},

   startSymbolAndLength-r16       INTEGER (0..127),

   repetitionNumber-r16              ENUMERATED {n2, n3, n4, n5, n6, n7, n8, n16}

                                                                    OPTIONAL,--Cond Formats1-0and1-1

   ...,

   [[

   k0-v1710 INTEGER(33..128)     OPTIONAL -- Need S

   ]]

NOTE : k0-v1710 is only applicable for PDSCH SCS of 480 kHz and 960 kHz. When the field is absent the UE applies the value 0.

NOTE : repetitionNumber Indicates the number of PDSCH transmission occasions for slot-based repetition scheme in IE RepetitionSchemeConfig.

PDSCH-Config ::= SEQUENCE {

   ...

   repetitionSchemeConfig-r16                SetupRelease { RepetitionSchemeConfig-r16 } OPTIONAL -- Need M

   ]],

   repetitionSchemeConfig-v1630             SetupRelease { RepetitionSchemeConfig-v1630 } OPTIONAL -- Need M

RepetitionSchemeConfig-r16 ::= CHOICE {

   fdm-TDM-r16                                    SetupRelease { FDM-TDM-r16 },

   slotBased-r16                                   SetupRelease { SlotBased-r16 }

RepetitionSchemeConfig-v1630 ::= SEQUENCE {

   slotBased-v1630                               SetupRelease { SlotBased-v1630 }

FDM-TDM-r16 ::= SEQUENCE {

   repetitionScheme-r16                        ENUMERATED {fdmSchemeA, fdmSchemeB,tdmSchemeA },

   startingSymbolOffsetK-r16                 INTEGER (0..7) OPTIONAL -- Need R

SlotBased-r16 ::= SEQUENCE {

   tciMapping-r16                                ENUMERATED {cyclicMapping, sequentialMapping},

   sequenceOffsetForRV-r16                  INTEGER (1..3)

SlotBased-v1630 ::= SEQUENCE {

   tciMapping-r16                               ENUMERATED {cyclicMapping, sequentialMapping},

   sequenceOffsetForRV-r16                INTEGER (0)

Example 1 >

This example is based on 38.523-3 7.1.2.2.2.

Example 2 >

PDSCH-Ack/Nack Timing defines the time gap between PDSCH transmission and the reception of the PUCCH that carries ACK/NACK for the PDSCH.

Simply put, K1 indicates the time delay between PDSCH slot and UCI (Ack/Nack) slot

PUCCH-Config ::=        SEQUENCE {

    dl-DataToUL-ACK        SEQUENCE (SIZE (8)) OF INTEGER (0..15)   OPTIONAL,   -- Need M

    dl-DataToUL-ACK-r16    SetupRelease { DL-DataToUL-ACK-r16 }

   dl-DataToUL-ACK-DCI-1-2-r16      SetupRelease { DL-DataToUL-ACK-DCI-1-2-r16}

DL-DataToUL-ACK-r16 ::= SEQUENCE (SIZE (1..8)) OF INTEGER (-1..15)

DL-DataToUL-ACK-DCI-1-2-r16 ::= SEQUENCE (SIZE (1..8)) OF INTEGER (0..15)

NOTE : You may refer to this example in protocol log to see how this works.

Following is the illustration showing the Time Domain resource allocation for PUSCH based on 38.214 - 6.1.2.1 Resource allocation in time domain. When the subcarrier spacing of PUSCH and PDCCH is different, the time delay between DCI slot and PUSCH slot is a little bit complicated as shown below, but when the subcarrier spacing of PUSCH and PDCCH is same the time delay between DCI slot and PUSCH slot becomes K2.

NOTE : In most case, we configure that PDSCH subcarrier spacing is same as PDCCH subcarrier spacing, so you can say K2 = Time Delay between DCI slot and PUSCH slot

Following is the RRC parameters determining k2. SLIV determination is a pretty complicated process. so I created a separate page for this, refer to this page .

PUSCH-TimeDomainResourceAllocation ::=  SEQUENCE {

    k2                                  INTEGER (0..32)                          

    mappingType                         ENUMERATED {typeA, typeB},

    startSymbolAndLength                INTEGER (0..127) // SLIV

PUSCH-TimeDomainResourceAllocation-r16 ::= SEQUENCE {

   k2-r16                   INTEGER(0..32) OPTIONAL, -- Need S

   puschAllocationList-r16  SEQUENCE (SIZE(1..maxNrofMultiplePUSCHs-r16)) OF PUSCH-Allocation-r16 ,

PUSCH-Allocation-r16 ::= SEQUENCE {

   mappingType-r16            ENUMERATED {typeA, typeB} OPTIONAL, -- Cond NotFormat01-02-Or-TypeA

   startSymbolAndLength-r16   INTEGER (0..127) OPTIONAL, -- Cond NotFormat01-02-Or-TypeA

   startSymbol-r16            INTEGER (0..13) OPTIONAL, -- Cond RepTypeB

   length-r16                 INTEGER (1..14)  OPTIONAL, -- Cond RepTypeB

   numberOfRepetitions-r16    ENUMERATED {n1, n2, n3, n4, n7, n8, n12, n16}

                                                       OPTIONAL, -- Cond Format01-02

After UE completed the reception of PDSCH, it cannot send HARQ ACK/NACK right away because it needs some time to process the received data. The time span that UE requires to process the received PDSCH is called Tproc as shown in the following illustration and N1 is a major factor determining the Tproc. Roughly speaking, you can take N1 almost same as PDSCH processing time. Depending on the UE performance, this Tproc may vary (i.e, Tproc would be shorter with high performance UE comparing to poor performing UE). When network configures K1 and PUCCH location, it is important that the configuration gives enough time for UE to complete the process. That is, network should configure K1 and PUCCH in such that Tgap_symb is greater than Tproc.

NOTE : I mentioned that the processing time would vary depending on UE performance. Then, the question is how Network get to know the UE peformance. It is via UE capability information. UE is expected to notify its capability of how fast it can process PDSCH (N1) via UE Capability Information message. In this report, UE does not send any specific N1 value. As shown above, there are two tables of N1 value. Every UE should meet Capability 1 requirement by default and it is optional to meet the capability 2 table. Whether a UE support capability 2 table or not is informed to Network via UE capability Information message as shown below.

FeatureSetDownlink-v1540 ::= SEQUENCE {

    oneFL-DMRS-TwoAdditionalDMRS-DL          ENUMERATED {supported} OPTIONAL,

    additionalDMRS-DL-Alt                    ENUMERATED {supported} OPTIONAL,

    twoFL-DMRS-TwoAdditionalDMRS-DL          ENUMERATED {supported} OPTIONAL,

    oneFL-DMRS-ThreeAdditionalDMRS-DL        ENUMERATED {supported} OPTIONAL,

    pdcch-MonitoringAnyOccasionsWithSpanGap   SEQUENCE {

        scs-15kHz                            ENUMERATED {set1, set2, set3} OPTIONAL,

        scs-30kHz                            ENUMERATED {set1, set2, set3} OPTIONAL,

        scs-60kHz                            ENUMERATED {set1, set2, set3} OPTIONAL,

        scs-120kHz                           ENUMERATED {set1, set2, set3} OPTIONAL

    } OPTIONAL,

    pdsch-SeparationWithGap                  ENUMERATED {supported} OPTIONAL,

    pdsch-ProcessingType2 SEQUENCE {

        scs-15kHz                            ProcessingParameters OPTIONAL,

        scs-30kHz                            ProcessingParameters OPTIONAL,

        scs-60kHz                            ProcessingParameters OPTIONAL

    pdsch-ProcessingType2-Limited SEQUENCE {

        differentTB-PerSlot-SCS-30kHz        ENUMERATED {upto1, upto2, upto4, upto7}

    dl-MCS-TableAlt-DynamicIndication        ENUMERATED {supported} OPTIONAL

pdsch-ProcessingType2 : According 36.306, it is stated as follows.

Indicates whether the UE supports PDSCH processing capability 2. The UE supports it only if all serving cells are self-scheduled and if all serving cells in one band on which the network configured processingType2 use the same subcarrier spacing. This capability signalling comprises the following parameters for each subcarrier spacing supported by the UE.

• fallback indicates whether the UE supports PDSCH processing capability 2 when the number of configured carriers is larger than numberOfCarriers for a reported value of differentTB-PerSlot. If fallback = 'sc', UE supports capability 2 processing time on lowest cell index among the configured carriers in the band where the value is reported, if fallback = 'cap1-only', UE supports only capability 1, in the band where the value is reported;
• differentTB-PerSlot indicates whether the UE supports processing type 2 for 1, 2, 4 and/or 7 unicast PDSCHs for different transport blocks per slot per CC; and if so, it indicates up to which number of CA serving cells the UE supports that number of unicast PDSCHs for different TBs. The UE shall include at least one of numberOfCarriers for 1, 2, 4 or 7 transport blocks per slot in this field if pdsch-ProcessingType2 is indicated.

pdsch-ProcessingType2-Limited :

Indicates whether the UE supports PDSCH processing capability 2 with scheduling limitation for SCS 30kHz. This capability signalling comprises the following parameter.

• differentTB-PerSlot-SCS-30kHz indicates the number of different TBs per slot.

The UE supports this limited processing capability 2 only if:

1) One carrier is configured in the band, independent of the number of carriers configured in the other bands;

2) The maximum bandwidth of PDSCH is 136 PRBs;

3) N1 based on Table 5.3-2 (shown above) for SCS 30 kHz.

UE PUSCH preparation procedure time : N2

After UE recieved the UL Grant(DCI 0_x), it cannot send PUSCH right away because it needs some time to prrepare the PUSCH data. The time span that UE requires to prepare PUSCH is called Tproc as shown in the following illustration and N2 is a major factor determining the Tproc. Roughly speaking, you can take N2 almost same as PUSCH preparation time. Depending on the UE performance, this Tproc may vary (i.e, Tproc would be shorter with high performance UE comparing to poor performing UE). When network configures K2 and PUSCH location(i.e, PUSCH SLIV), it is important that the configuration gives enough time for UE to complete the preparation. That is, network should configure K2 and PUSCH in such that Tgap_symb is greater than Tproc.

NOTE : I mentioned that the processing time would vary depending on UE performance. Then, the question is how Network get to know the UE peformance. It is via UE capability information. UE is expected to notify its capability of how fast it can prepare PUSCH (N2) via UE Capability Information message. In this report, UE does not send any specific N2 value. As shown above, there are two tables of N2 value. UE notify the processing parameters for each capability table.

phy-Parameters {

   phy-ParametersCommon {

      ...

      bwp-SwitchingDelay type1,

featureSetsDownlink {

   {

    ...

    pdsch-ProcessingType1-DifferentTB-PerSlot {

       scs-15kHz upto2,

       scs-30kHz upto2,

       scs-60kHz upto2,

       scs-120kHz upto2

     },

FeatureSetUplink ::= SEQUENCE {

   featureSetListPerUplinkCC               SEQUENCE (SIZE (1.. maxNrofServingCells)) OF

                                                        FeatureSetUplinkPerCC-Id,

   scalingFactor                           ENUMERATED {f0p4, f0p75, f0p8} OPTIONAL,

   dummy3                                  ENUMERATED {supported} OPTIONAL,

   intraBandFreqSeparationUL               FreqSeparationClass OPTIONAL,

   searchSpaceSharingCA-UL                 ENUMERATED {supported} OPTIONAL,

   dummy1                                  DummyI OPTIONAL,

   supportedSRS-Resources                  SRS-Resources OPTIONAL,

   twoPUCCH-Group                          ENUMERATED {supported} OPTIONAL,

   dynamicSwitchSUL                        ENUMERATED {supported} OPTIONAL,

   simultaneousTxSUL-NonSUL                ENUMERATED {supported} OPTIONAL,

   pusch-ProcessingType1-DifferentTB-PerSlot SEQUENCE {

      scs-15kHz                            ENUMERATED {upto2, upto4, upto7} OPTIONAL,

      scs-30kHz                            ENUMERATED {upto2, upto4, upto7} OPTIONAL,

      scs-60kHz                            ENUMERATED {upto2, upto4, upto7} OPTIONAL,

      scs-120kHz                           ENUMERATED {upto2, upto4, upto7} OPTIONAL

   } OPTIONAL,

   dummy2 DummyF OPTIONAL

FeatureSetUplink-v1540 ::= SEQUENCE {

   zeroSlotOffsetAperiodicSRS            ENUMERATED {supported} OPTIONAL,

   pa-PhaseDiscontinuityImpacts          ENUMERATED {supported} OPTIONAL,

   pusch-SeparationWithGap               ENUMERATED {supported} OPTIONAL,

   pusch-ProcessingType2 SEQUENCE {

      scs-15kHz                          ProcessingParameters OPTIONAL,

      scs-30kHz                          ProcessingParameters OPTIONAL,

      scs-60kHz                          ProcessingParameters OPTIONAL

   ul-MCS-TableAlt-DynamicIndication     ENUMERATED {supported} OPTIONAL

FeatureSetUplink-v1610 ::= SEQUENCE {

   pusch-RepetitionTypeB-r16 SEQUENCE {

      maxNumberPUSCH-Tx-r16              ENUMERATED {n2, n3, n4, n7, n8, n12},

      hoppingScheme-r16                  ENUMERATED {interSlotHopping, interRepetitionHopping, both}

   ul-CancellationSelfCarrier-r16        ENUMERATED {supported} OPTIONAL,

   ul-CancellationCrossCarrier-r16       ENUMERATED {supported} OPTIONAL,

   ul-FullPwrMode2-MaxSRS-ResInSet-r16   ENUMERATED {n1, n2, n4} OPTIONAL,

   cbgPUSCH-ProcessingType1-DifferentTB-PerSlot-r16 SEQUENCE {

      scs-15kHz-r16                      ENUMERATED {one-pusch, upto2, upto4, upto7} OPTIONAL,

      scs-30kHz-r16                      ENUMERATED {one-pusch, upto2, upto4, upto7} OPTIONAL,

      scs-60kHz-r16                      ENUMERATED {one-pusch, upto2, upto4, upto7} OPTIONAL,

      scs-120kHz-r16                     ENUMERATED {one-pusch, upto2, upto4, upto7} OPTIONAL

   cbgPUSCH-ProcessingType2-DifferentTB-PerSlot-r16 SEQUENCE {

[1] 38.214 - 5G; NR; Physical layer procedures for data

[2] 38.331 - 5G; NR; Radio Resource Control (RRC); Protocol specification  

[4] R1-1721515 : 3GPP TSG-RAN WG1 Meeting #91 Summary of DL/UL scheduling and HARQ management  

[5] R1-1719401 : 3GPP TSG RAN WG1 Meeting 91 - Remaining issues on HARQ

[6] The impact of NR Scheduling Timings on End-to-End Delay for Uplink Traffic