3GPP TSG-RAN WG1 Meeting #121	R1- 2503221
Malta, MT, May 19th – May 23rd, 2025

Agenda Item:	9.4.2
Source:	Ericsson
Title:	Coding aspects for Ambient IoT
Document for:	Discussion, Decision
1	

Conclusion
In the previous sections we made the following observations:
Observation 1	OOK modulation without Manchester encoding has several drawbacks, such as synchronization issues, threshold sensitivity, and susceptibility to noise.

Based on the discussion in the previous sections we propose the following:
Proposal 1	Support Manchester line code as specified in TR 38.769 for both R2D and D2R with OOK modulation.
Proposal 2	When FEC is applied to a D2R transmission, the coding rate can be set to either 1/2 or 1/3.
Proposal 3	Support FEC with a coding rate of 1/2, which can be achieved through puncturing, instead of using simple repetition.
Proposal 4	The reader can indicate the D2R chip duration and repetition during device-specific scheduling restriction; hence, no additional down-selection among the R values is required in RAN1.

3GPP TSG RAN WG1 Meeting #121	R1-2503225
St. Julian’s, Malta, May 19 – 23, 2025
Agenda Item:	9.4.2
Source:	Futurewei
Title:	Coding aspects for A-IoT physical channel
Document for:	Discussion and Decision 

Conclusion
The following observations and proposals were discussed in this contribution.
Block repetition
Observation 1. It is preferable to use convolutional codes alone or combine convolutional codes with at most 2 repetitions (Rblock=2) over repetitions alone.
Proposal 1: For the number of block-level repetitions Rblock, Rblock=1 and Rblock=2 are supported.
Note: When Rblock=1, it indicates no repetition
Note: Rblock=2 is only used when channel coding is applied 
FEC
Proposal 2. For Ambient IoT devices, the output of the rate R=1/3 convolutional encoder is ordered , where
 is the output corresponding to the polynomial 133 (octal)
 is the output corresponding to the polynomial 173 (octal)
 is the output corresponding to the polynomial 165 (octal).
Proposal 3. For Ambient IoT devices, support a rate Rcode=1/2 convolutional encoder with the output ordering , where
 is the output corresponding to the polynomial 133 (octal)
 is the output corresponding to the polynomial 173 (octal)

SFS
Proposal 4: For D2R transmission, down select bit duration  with the chip duration corresponding to ; the rest of the bit duration and chip duration along with the SFS factor  are given in the following table:

Proposal 5: For D2R transmission, a set of feasible SFS factors is , which can be signaled with 3 bits.
Proposal 6: For D2R transmission, the set of feasible chip intervals is , which can be signaled with 3 bits.
Observation 2: Since the combination of chip intervals, bit durations, SFS factors is less than 32, joint coding with 5 bits is also possible.

3GPP TSG-RAN WG1 Meeting #121	R1-2503295
St Julian’s, Malta, May 19-23, 2025

Agenda Item:	9.4.2
Source:	Huawei, HiSilicon
Title:	Physical channel design on channel coding
Document for:	Discussion and Decision

Conclusions
In this contribution, the physical channel design on channel coding for Ambient IoT is discussed and following observations and proposals are made accordingly.
Observation 1: The minimum bit length Tb,min can be selected as 1.39  for achieving comparable peak rate with RFID and saving power consumption compared with Tb,min = 1.04 . The corresponding minimum chip length Tchip,min is 0.69 .
Observation 2: There is no need to further optimize the candidate set of R value since the difference of indication overhead is marginal and RAN1 does not need to specify the reader’s implementation.
Proposal 1: For D2R:
The D2R chip durations are {133.33, 66.67, 33.33, 16.67, 11.11, 8.33, 5.56, 4.17, 2.78, 2.08, 1.39, 1.04, 0.69}μs.
The minimum bit duration is 1.39 μs.
Proposal 2: The following R set is supported as long as the reader by implementation ensures that overlapping R values are not selected for devices to use at the same time .
 The D2R R values are {1, 2, 4, 6, 8, 12, 16, 24, 32, 48, 64, 96, 128}.
Proposal 3: The supported Y values are {1, 2, 4, 8}.
Proposal 4: The detailed signalling of indicating R, chip length and Y will be handled by RAN2.
Proposal 5: Values of D2R chip duration Tchip, bit duration Tb, and SFS factor R in the following table are supported:
Proposal 6: For the D2R transmission of Ambient IoT, the maximum repetition number for block repetition is 2 or 4, with the supported repetition numbers being {1, 2} or {1, 2, 3, 4} respectively. 
Proposal 7: For bit collection after FEC, the output bits for each input bit are arranged sequentially in accordance with the input bits, i.e., for input bits , the output of the FEC is 
Proposal 8: For attaching the CRC, the parity bits are appended to the end of the input bits, similar to what is done in TS 38.212.

3GPP TSG RAN WG1 #121	R1-2503300
St Julian's, Malta, May 19th - 23rd, 2025

Source:	Nokia
Title:	AIoT Physical channels design - line coding, FEC, CRC, repetition aspects
Agenda item:	9.4.2
Document for:	Discussion and Decision

Conclusion

In this contribution we have made the following observations and proposals:
Proposal 1: For D2R channel coding, support code rate ½ in addition to code rate 1/3 and code rate 1 (no channel coding).
Proposal 2: For D2R block-level repetition, support number of repetitions (Rblock) in { 1, 2, 4 }.
Proposal 3: In D2R control signaling, whether FEC is applied, which FEC code rate (if multiple code rates are supported) and the number of block level repetitions can be jointly encoded.
 

3GPP TSG RAN WG1 meeting #121                                R1- 2503312
St Julian’s, Malta, May 19th – 23rd, 2025
Source: 	ZTE Corporation, Sanechips
Title:	Discussion on Ambient IoT coding and SFS
Agenda Item:	9.4.2
Document for:	Discussion and decision

Conclusion
In this contribution, we discuss the Ambient IoT coding design and have the following observations and proposals.
In the agreed table, the R value of 12, 24, 48, 96 is three times of 4, 8, 16, 32, respectively. Thus the performance would be affected by the corresponding 3rd harmonic.
The interference due to partial main-lobe overlap has impact on the multi-access performance, including:
The interference of partial main-lobe overlap between R={1, 2} results in about 2dB loss @10%BLER for R=1 and about 1dB loss @1%BLER for R=2;
The interference of partial main-lobe overlap between R={6, 8} results in about 0.7dB loss @1%BLER for R=6 and about 1dB loss @1%BLER for R=8;
The interference of partial main-lobe overlap between R={12, 16} results in about 0.6dB loss @1%BLER for R=12 and about 0.6dB loss @1%BLER for R=16;
The interference of partial main-lobe overlap between R={24, 32} results in about 1dB loss @10%BLER and more than 6dB @1%BLER for R=24, and about 1dB @10%BLER and more than 6dB @1%BLER for R=32.
The interference due to 3rd harmonic has non-negligible impact on the multi-access performance, including:
The performance of R=6 is degraded about 0.4dB at 10%BLER and more than 3dB at 1%BLER, resulting from the interference of 3rd harmonic of R=2;
The performance of R=12 is degraded about 1dB at 10%BLER and more than 3dB at 1%BLER, resulting from the interference of 3rd harmonic of R=4;
The performance of R=24 is degraded more than 4dB at 1%BLER, resulting from the interference of 3rd harmonic of R=8;
The performance of R=48 is degraded about 1.5dB at 10%BLER and more than 3dB at 1%BLER, resulting from the interference of 3rd harmonic of R=16;
The performance of R=96 is degraded about 3dB at 10%BLER, resulting from the interference of 3rd harmonic of R=32.
If the D2R bit durations sorted in descending order progressively decreases by 1/2, the number of D2R chip durations can be reduced.
The indication overhead of Alt.1 for Msg1 transmission is 5 bits.
The indication overhead of Alt.2 for Msg1 transmission is 6 bits.
The indication overhead of Alt.3 for Msg1 transmission is 6 bits.
The indication overhead of Alt.1 is 5*N bits for N Msg3 transmissions, and it increases with the increase of the number of Msg3 transmission.
Alt.2 requires less indication overhead which is fixed for different number of Msg3 transmission.
In LTE convolutional coding, for the code rate of 1/2, all bits of 1st and the 2nd parity bit streams are output. 
The SNR performance gap between code rate of 1/3 and no FEC is about 10dB.  
Compared to repeating twice without FEC, using a FEC of 1/2 coding rate can provide 5dB performance gain and reduce power consumption by about 70%.
Considering the performance loss caused by the main-lobes overlap in the presence of SFO, it’s recommended not to use the following R values simultaneously:
R=1 and R=2;
R=6 and R=8;
R=12 and R=16;
R=24 and R=32.
Considering the performance loss caused by the 3rd harmonic interference, it’s recommended not to use R values of 6, 12, 24, 48 and 96. 
Further considering the harmonics interference resulting from R=1, R={2,4,8,16,32,64,128} is proposed for the FDM-ed D2R transmission, while R=1 is proposed to be used for the single-device transmission.
Considering the indication overhead and the implementation complexity, the down-selected potential values of D2R chip duration Tchip, bit duration Tb, and SFS factor R, are shown in the following table:
For the indication of SFS resources for Msg1 transmission, Alt.1 (i.e., indicate a common Tchip combined with a R set) is preferred to reduce the indication overhead.
For the indication of SFS resources for Msg3 transmission, Alt.2 (i.e., indicate a SFS resources set shared for all devices’ Msg3 transmission) is preferred to reduce the indication overhead.
Support code rates of Option 2: {1/2, 1/3} for convolutional coding. 
R=1 and Rep=2 should not be supported. 
Clarify that output bit sequence of convolutional coding is for code rate 1/3 and for code rate 1/2 , wherein bit  corresponds to the 1st parity bit stream with polynomial(133), bit  corresponds to the 2nd parity bit stream with polynomial(171), and bit  corresponds to the 3rd parity bit stream with polynomial(165). 
It is proposed that the bit collections in the TS_38.291 as in [3] can be described as below:
If R=1/2 is supported, at least support following code rates and repetitions combinations: {1, 1}, {1/2, 1}, {1/3, 1}, {1/3, 2}. 
If R=1/2 is not supported, at least support following code rates and repetitions combinations: {1, 1}, {1/3, 1}, {1/3, 2}, {1/3, 4}. 

3GPP TSG RAN WG1 #121	R1-2503359
St Julian’s, Malta, May 19th - 23rd, 2025

Source:	vivo
Title:	Remaining issues on line coding, FEC, CRC and repetition for A-IoT  
Agenda Item:	9.4.2
Document for:	Discussion and Decision

Conclusion
In this contribution, we provide our views on remaining issues of FEC, Small frequency shift and block level repetition. 
Observation 1: Up to 2 repetitions can be sufficient.  
Proposal 1: For FEC, the sequence of bits after channel coding and bit collection is , , where  is j-th encoded bits corresponding to i-th branch. 
Proposal 2: Support table 2 as candidate set for D2R chip duration Tchip and R, supporting up to Y=7 FDMed D2R transmission.  
Proposal 3: For indicating chip duration and R for FDMA of Y D2R resource at least for Msg1 and Msg3 transmission, support following indications 
Single reference chip duration for Y D2R resources
A bitmap with bit length Ymax for the set of candidate R values, e.g., {Ri}, where each Ri value is associated with one bit location, the bit set to 1 indicates that the Ri is used for a D2R resource; the bit set to 0 indicates that the Ri is NOT used 
Ymax is determined by the maximum number of FDMed devices associated with the indicated reference chip duration, or determined by the maximum number of FDMed devices associated with any one of the candidate reference chip durations. 
Proposal 4: For indicating chip duration and R for D2R transmission other than Msg1 and Msg3 transmission, i.e., for non-FDMA D2R transmission, down-select from the following indication options
Option 1: Same indication method as used for Msg3 transmission  
Option 2: 3-bit indication for D2R chip duration and 3-bit indication for R value

3GPP TSG RAN WG1#121                                                                 R1-2503516
St Julian's, Malta, 19 - 23 May, 2025
Agenda Item:     9.4.2
Source:	Spreadtrum, UNISOC
Title:	Discussion on line coding, FEC, CRC, repetition aspects for Ambient IoT
Document for:	Discussion and decision

Conclusion
The following observations and proposals are achieved:
Observation:
Observation 1: The number of 8 values with {1, 4, 8, 16, 32, 64, 128, 256} for R is sufficient to meet the system capacity requirements.
Observation 2: Reader indicate Y, D2R bit length, and R to the device to obtain the frequency domain resource for the corresponding D2R transmission.
Observation 3: To achieve the goals with supporting a higher performance, or a higher code rate, or a flexible code rate, it may cause redundant to discuss other alternative schemes like puncturing.

Proposal:
Proposal 1: The potential values of D2R chip duration Tchip, bit duration Tb, and SFS factor R, are shown in the following table:

Proposal 2: For the same data rate for FDMed transmissions, e.g., FDMed Msg1 transmission, 12 bit is needed to indicate the frequency domain resource for the corresponding D2R transmission based on the potential value in the table.
3 bit is needed for 8 candidate values of Tb within the table, i.e., 266.67μs, 133.33μs, 66.67μs, 33.33μs, 16.67μs, 8.33μs, 4.17μs, 1.04μs
9 bit with a bitmap is needed for R and Y, each one bit corresponds to a Tchip
Proposal 3: Only support the code rate of FEC with 1/3 if FEC is applied for a D2R transmission.
Proposal 4: For the number of block-level repetitions, {1, 2} repetitions are supported.
Note: When the number of block-level repetition is 1, it indicates no repetition.

3GPP TSG RAN WG1 #121                                            R1-2503537                
St Julian's, Malta, May 19th-23rd, 2025

Source:	TCL
Title:	Discussion on line coding/FEC/CRC/repetition aspects for Ambient IoT
Agenda Item:	9.4.2
Document for:	Discussion and Decision

Conclusion
In this contribution, we provide our views on R2D and D2R coding/FEC/repetition related topics for AIoT. The observations and proposals are listed as below:
Observation 1: The user experienced data rate target is in the range of 0.1kbps~ 5kbps for R2D and D2R transmission.

Observation 2: It can be observation from RAN 1 #118b that there are different Btx,D2R and transmission power of the D2R transmissions due to XOR operation.

Observation 3: SFS factor setting is associated with SCS/harmonic components/guard band defined in RAN4. 

Observation 4: As the impact of SFO of device 1, each repetition block needs to consider the potential time offset (△t) to avoid the impact of SFO, which is up to the device’s capability and each block length. 

Observation 5: Limited by one bit length, the impact of SFO during one or multiple bit may be ignored, which is up to repetition number of bit-level repetition. 

Observation 6：For the number of bit-level repetition, it is up to coverage and access performance and it will impact on D2R frame structure selection.


Proposal 1: The maximum D2R chip duration is 133.33 μs (assuming 1.92MHz sampling clock).
Proposal 2: The minimum D2R chip duration is 1.39 μs.
Proposal 3: The set of D2R chip duration is {133.33, 66.67, 33.33, 16.67, 11.11, 8.33, 5.56, 4.17, 2.78, 2.08, 1.39}μs and further down-selection could be considered if possible.

Proposal 4: Support option 1 or no D2R line code (e.g., by using a square-wave corresponding to the small frequency-shift)

Proposal 5: Support R=2n as common SFS factor and no special R should be down-selected in Rel-19.

Proposal 6: Support option 2 as the number of block-level repetitions.
Option 2: {1, 2, 4}
Note: When the number of block-level repetition is 1, it indicates no repetition.

Proposal 7: Consider D2R block-level repetition based on following aspects,
Frequency resource for each repetition block, e.g., if hopping frequency could be considered for each block
How to indicate frequency resource and repetition number (R)

Proposal 8: Consider D2R bit-level repetition based on following aspects,
Repetition number (R)
How to indicate time/frequency resource and repetition number (R)

3GPP TSG RAN WG1 #121		R1-2503567
St Julian’s, Malta, May 19th – 23th, 2025
Agenda item:	9.4.2
Source:	Samsung
Title:	Views on Physical channels design – line coding, FEC, CRC, repetition aspects
Document for:	Discussion and decision

Conclusion
In this contribution, we made the following observations and proposals:
Observation 1: Given that no FEC is already supported in D2R, there is limited justification for introducing puncturing to achieve higher code rates.
Observation 2: Since block-level repetition has already been agreed upon, additionally repeating coded bits is unnecessary and redundant.
Proposal 1: There is no consensus to support FEC code rate 1/2 in Rel-19.
Observation 3: It can be difficult for the reader to determine whether each device is close enough to operate without FEC, based on proximity determination solution 1.
Proposal 2: The use of FEC is configured via A-IoT paging. It is assumed that all devices operate in the same manner with respect to FEC usage within the same inventory or command round. 
Note: This issue can be addressed under A.I. 9.4.4 or within this A.I.
Observation 4: If L1 R2D control information is defined, it must have a separate CRC so that a device can first read R2D control information to acquire information necessary to read the following R2D data.  
Proposal 3: If L1 R2D control information is supported, the L1 control information is attached with a separate CRC-6. If L1 R2D control information is not supported, no need for further discussion.  
Proposal 4: For the number of block-level repetitions, {1, 2} repetitions are supported.
Note: When the number of block-level repetition is 1, it indicates no repetition.
Signalling details can be discussed under A.I. 9.4.4 or within this A.I.
Proposal 5: For D2R small frequency shift, only cases where R=2n are to be supported. 
Proposal 6: Down-selection of Tb, Tchip and R according to the table below.
Proposal 7: The configuration of Tchip and R shall be provided via higher-layer signaling via the corresponding PRDCH.
Proposal 8: Different Tb values lead to different multiplexing capacities in the frequency domain. For each Tb, the set of available Tb values shall be predefined accordingly.
Proposal 9: The reader can transmit a Tb value via an R2D message that triggers random access. Based on the indicated Tb, the device can randomly select one Tchip value from the corresponding set.
References:


Sinha, Satyajit. "State of IoT 2024: Number of connected IoT devices growing 13% to 18.8 billion globally." IoT Analytics (2024).
RP-243326 “New Work Item: Solutions for Ambient IoT (Internet of Things) in NR”. 

3GPP TSG RAN WG1#121		R1-2503618
St. Julian's, Malta, May 19th – 23rd, 2025

Source:	Panasonic
Title: 	Discussion on Physical Channel Designs for A-IoT
Agenda Item:		9.4.2
Document for:	Discussion

Conclusions
In this contribution, we provided our views on physical channel designs for A-IoT. We made following proposals:
Proposal 1: The minimum D2R chip duration should be 1.04 μs. The maximum SFS factor of R=128 should be supported to accommodate up to 8 FDMed devices. Tb of 2.78 μs, 5.56 μs, 11.11 μs, 22.22 μs are not required to be supported.
Proposal 2: Explicit indication of transmission parameters should be used for scheduling Msg1 and Msg3 transmissions.
Proposal 3: The FEC code rate of 1/2 should be supported by using 2 out of 3 output bits of CC polynomial generator.
Proposal 4: A block repetition number of 4 should be supported to achieve a desired coverage.

3GPP TSG RAN WG1 #121                                                                                    		R1-2503794
St Julian's, Malta, May 19th – 23rd, 2025 
  
Source:             CATT
Title:                  Ambient IoT channel coding and small frequency shift 
Agenda Item:    9.4.2
Document for:  Discussion and Decision	

Conclusion
In this contribution, channel coding and small frequency shift technique for NR Ambient IoT communication system are discussed. We have the following observations and proposals:
Observation 1: With Manchester line coding, the R2D information data rate can be described as 1/(2*R2D chip length), and the R2D chip length is determined by the M value of OOK-4 and the OFDM symbol duration with 15k SCS .
Proposal 1: For CC in A-IoT device 1
Repetition operation should be integral multiples of CC codeword.
Bit collection should be performed based on natural order of three encoder output parity streams.
Note: 
No need to support the sub-block interleaver(s) and puncturing operation of rate matching in LTE-TBCC.
Proposal 2: From the perspective of robustness of TBCC to SFO, D2R preamble design should ensure that residual timing error does not exceed 1000ppm.
Observation 2: With same coding rate, TBCC code has about 6dB coding gain than that of Manchester code at BLER=10%.
Observation 3: Compared with CC code only, CC concatenated with Manchester code would introduce unnecessary redundancy, while its performance is poor than that of convolutional code with repetition operation in case of SFO=1000ppm.
Proposal 3: Manchester line code should not be supported together with CC coding.
Observation 4: The phase discontinuity issue of OOK demodulation by the reader using the BPSK demodulation method after DC removal would severely degrade the OOK demodulation performance if the reader does not know the D2R waveform is OOK or BPSK.  
Proposal 4: In order not to degrade the OOK demodulation performance, the reader should be aware of the modulation scheme of OOK or BPSK for the D2R transmission.  
Proposal 5: The D2R chip duration of {133.33, 66.67, 33.33, 16.67, 11.11, 8.33, 5.56, 4.17, 2.78, 2.08, 1.39, 1.04, 0.69, 0.52} μs should be supported for Rel-19 A-IoT.
Proposal 6: The D2R bit duration could support both of 1.39μs and 1.04μs for Rel-19 A-IoT. If one D2R bit duration needs to be down-selected between 1.39μs and 1.04μs, D2R bit duration of 1.39μs should be supported.
Observation 5: D2R transmissions with SFS factor R=2n have similar BLER performance without FDM performance degradation; however, the number of available D2R channels is reduced tremendously.  This will reduce the spectrum utilization.  
Observation 6: The BLER performance of D2R channels with SFS factor 3*R, 5*R and 7*R , due to odd harmonics interference, would be degraded by about 3dB, 1.5 dB and 0.8dB, respectively without interference cancellation at the reader. However, reader can perform interference mitigation with simple harmonics interference cancellation to ensure the BLER performance.
Observation 7: The BLER performance of D2R channels with 3rd harmonics interference cancellation is improved by 2dB compared with that of the D2R channel without harmonic interference cancellation.
Proposal 7: Considering very poor FDMA capacity performance of SFS factor Alt.2, R=2n only should not be supported for determination of the value of SFS factor in Rel-19 A-IoT.
Proposal 8: SFS factor Alt.1:  should be supported with following R values 

Observation 8：Transmission bandwidth of D2R channel without small frequency shift is 2/Tb , which is half of transmission bandwidth of D2R channel with SFS factor R=1.
Proposal 9: To improve frequency spectrum efficiency, D2R channel without small frequency shift should be supported for Msg1/Msg3 transmission with the D2R bit duration being equal to the chip duration.
Observation 9: For the D2R channel by a small frequency shift, the device needs to know any two of the bit duration Tb, D2R chip duration and SFS factor R.
Proposal 10: SFS factor R could be included for the indication of frequency channel in the R2D control information.
Proposal 11: To indicate D2R chip duration Tchip and SFS factor R, there are two schemes can be considered
Option a: The D2R chip duration is implicitly indicated by deriving from the control signaling of bit duration Tb and SFS factor R. 
Option b: The D2R chip duration and SFS factor R are explicitly indicated for the D2R transmission
Proposal 12: When the D2R chip duration is implicitly indicated by deriving from the control signaling of bit duration Tb and SFS factor R, three potential Options for D2R transmission indication should be considered, and the Option a-3 could be preferable for flexible indication.
Option a-1: The value/index of the bit duration Tb is explicitly indicated based on the pre-defined table, in which it also pre-defines the relationship of the bit duration Tb and corresponding chip duration Tchip and SFS factors R. 
Option a-2: The value/index of the bit duration Tb and the SFS factor R are jointly explicitly indicated for D2R transmission via the control information of PRDCH. The R could be expressed as Rmax for FDMed Msg1 transmission, while it could be the dedicated R value for Msg3 or CFRA.
Option a-3: The value/index of the bit duration Tb is explicitly indicated and the corresponding subset of the R values are also indicated via the control information of PRDCH or based on the pre-defined table.
Proposal 13: When the explicit indication of D2R chip duration is supported, the following two potential options should be considered and Option b-1 is preferable due to simple implementation.
Option b-1: The D2R chip duration index and the SFS factor R are carried in the control information in PRDCH. The D2R bit duration and corresponding R value(s) could be derived via the indicated chip duration and the R value (e.g. maximum/minimum R value) according to the predefined R value set or TBS related information.
Option b-2: The joint indication of the D2R chip duration and subset of R values for D2R transmission is carried in the control information in PRDCH. 
Observation 10: For D2R data rate of 240k, when the number of repetitions is less than 8, the target coverage distance of 15m cannot be reached.
Proposal 14: 2 bits should be included PRDCH to indicate D2R block repetition number {1, 2, 4, 8}.
Proposal 15: Although SFS is equivalent to Manchester code bit level repetition in bit mapping perspective, it cannot provide redundancy bits to obtain repetition coding gain. Manchester codeword repetition using for SFS purpose should not be supported as part of repetition coding scheme. 
Proposal 16: Bit level repetition should not be supported for Rel-19 A-IoT.
Proposal 17:  Joint CRC should be applied to both R2D control information and R2D data.

3GPP TSG RAN WG1 #121                               R1-2503832 
Malta, MT, May 19th - 23rd, 2025

Source: 	CMCC
Title:	Discussion on coding aspects of physical channel design
Agenda item:	9.4.2
Document for:	Discussion/Decision

Conclusions
In this contribution, we provide our views on coding aspects of physical channel design and the following observations and proposals are made:
Observation 1: A 2.88 MHz clock can provide a comparable and slightly higher sampling rate than UHF RFID, where the device can implement a 2.56 MHz sampling clock.
Observation 2: The values of D2R chip duration or bit duration should be related to (e.g., a multiple of or a factor of) the R2D chip duration, as the device performs the D2R clock calibration from R2D CAP.
Observation 3: RAN1 supports M = 2, 6, 12, 24 for R2D transmission, a 2.88 MHz sampling speed is a common multiple of both 2 and 3, which can avoid non-integer counting errors when device calibrates samples for D2R chip duration.
Observation 4: From reader reception perspective, as long as the main lobe of the frequency domain resources between different multiplexed devices are non-overlapped, the reception performance can be guaranteed.
Observation 5: Using R = 2n, the selection of R can be more flexible and provide more multiplexing capability in the frequency domain.
Observation 6: Smaller R values can be selected using R = 2n than using R = 2n, which are beneficial for D2R link performance, as smaller R values correspond to larger D2R chip durations.

Proposal 1: Support the following 8 values of D2R bit duration and corresponding D2R chip duration (when R = 1):
For the D2R bit duration: 266,67 μs, 133.33 μs, 66.67 μs, 33.33 μs, 16.67 μs, 8.33 μs, 4.17 μs, 1.39 μs.
Notes: the first three values have been agreed in RAN1#120bis.
For the D2R chip duration (R = 1): 133.33 μs, 66.67 μs, 33.33 μs, 16.67 μs, 8.33 μs, 4.17 μs, 2.08 μs, 0.69 μs.
Proposal 2: The following R values and the maximum number of multiplexed devices in the frequency domain are supported:
R = {1, 2, 4, 8, 16, 32}, if the maximum number of multiplexed devices Ymax = 4.
R = {1, 2, 4, 8, 16, 32, 64}, if the maximum number of multiplexed devices Ymax = 6.
Proposal 3: For a D2R transmission, the combination of Tchip and corresponding R value is indicated in a combination.
Proposal 4: To support FDMA with Y≥1 D2R transmissions,
If Ymax = 4, 6 bits is used to indicate a combination of Tchip and R for a D2R transmission, and 24 bits in total is needed to provide frequency domain resources to multiplex up to 4 devices.
If Ymax = 6, 6 bits is used to indicate a combination of Tchip and R for a D2R transmission, and 36 bits in total is needed to provide frequency domain resources to multiplex up to 6 devices.
Proposal 5: If FEC is applied for a D2R transmission, only the 1/3 code rate is supported.
Proposal 6: For the number of block-level repetitions in D2R transmission, Option 2: {1, 2, 4} is supported. If the option size must be expanded to four values, either {1, 2, 3, 4} or {1, 2, 4, 8} can be supported from our perspective.

3GPP TSG RAN WG1 #121			R1-2503883
St Julian’s, Malta, May 19th – 23rd, 2025

Agenda Item:	9.4.2
Title:	Discussion on line coding, FEC, CRC and repetition aspects for Ambient IoT
Source:	Xiaomi
Document for:	Decision

Conclusion
This contribution discusses about channel coding aspects for Ambient IoT including small frequency shift and FEC, and the following observation and proposals can be concluded:
Observation
Observation 1: For D2R FDMA, R=2 and R=4 (M=4 and M=8), the interference between main lobes and side lobes from different devices has negative impact on FDMA performance.
Observation 2: For D2R FDMA, R=2 and R=6 (M=4 and M=12), and R=4 and R=6 (M=8 and M=12), the interference between main lobes and side lobes from different devices can be negligible.

Proposals
Proposal 1: For D2R FDMA, the case of R=2 and R=4 (M=4 and M=8) is not selected.
Proposal 2: Besides D2R chip duration, SFS factor R is indicated in R2D control information predefined a set of D2R SFS factor R values.
Proposal 3: For D2R chip duration supports value set of {133.33, 66.67, 33.33, 16.67, 8.33, 4.17, 2.08, 1.04, 0.52} μs.
Proposal 4: Joint indication on D2R chip duration and SFS factor R is supported.
Proposal 5: For FDMed D2R transmission, predefine a set of combination of chip durations and SFS factor R, and indication is according to the predefined combination index.
Proposal 6: The predefined set of combination of chip durations and SFS factor R should support target of multiple devices and single devices.
Proposal 7: To indicate the maximum number of Msg 1 resources with X=2 and Y, the same SFS factor R values set is applied on both time domain occasions for X=1 and X=2.
Proposal 8: For D2R FEC, the target coding rate is the same as mother code with coding rate 1/3.

3GPP TSG RAN WG1 #121	R1-2503925
St Julian's, Malta, 19 - 23 May, 2025

Agenda Item:	9.4.2
Source:	NEC
Title:	Physical layer design – line coding, FEC, CRC, repetition aspects
Document for:	Discussion and Decision
1	

Conclusion
In this contribution, we give our views on the aspects of line coding, FEC, CRC and repetition of ambient IoT physical channel design. We propose that:
Proposal 1: For code rate of FEC, Option 2 with both {1/2, 1/3} is preferred.
Proposal 2: The value R=2 should be removed from the Tchip-Tb-R table.
Observation 1: The size of small frequency shift depends of Tchip only.
Observation 2: For 2SB D2R, the frequency position of each sideband could be {3.75, 7.5, 15, 30, 45, 60, 90, 120, 180, 240, 360, 480, 720, 960} in kHz.
Proposal 3: For D2R scheduling, Btx,D2R should be explicitly or implicitly indicated to device(s), and the adopted Tchip or R should be restricted by Btx,D2R.
Proposal 4: For Msg1 scheduling, the bit duration Tb could be obtained by indicated Tchip and R, and the potential value of R could be determined by at least one of the following alternatives.
Alt 1: potential value of R could be selected by the row of Tb, and restricted by the indicated R;
Alt 2: potential value of R could be selected by the row of Tb, and restricted by Btx,D2R;
Proposal 5: The FDRA field in Msg2 is a bitmap whose length is N which represents the number of candidate R values indicated by A-IoT paging message, the value set is same as Msg1.
When the nth bit in the bitmap is “1”, it means the nth SFS factor value Rn-1 in the SFS candidate value set {R0, R1…RN} is used for the corresponding ith device to determine the frequency domain resource:
Where i corresponds to the order in which the device ID appears in Msg2.
Proposal 6: For block-level repetition, Option 2 with both {1,2,4} is supported.
Proposal 7: Support joint indication of FEC code rate and repetition number with 3 bits using Table below:

3GPP TSG RAN WG1 #121			R1-2504047
St Julian’s, Malta, May 19th – 23th, 2025

Agenda item:		9.4.2
Source:	China Telecom
Title:	Discussion on physical channels design about line coding, FEC, CRC, repetition aspects for Ambient IoT
Document for:		Discussion

Conclusion
In this contribution, we have the following proposals:
Proposal 1: Support R values based on 2n.
Proposal 2: Delete the value of 1.04μs for D2R bit duration.
Proposal 3: Delete the value of 0.52μs for D2R chip duration.
Proposal 4: Support the following table for D2R chip duration, bit duration and SFS factor R.

Proposal 5: Support using 6 bits to jointly indicate the value of D2R chip duration, bit duration and SFS factor R.
Proposal 6: Support the maximum number of multiplexed devices Y as 8.
Proposal 7: Support 1/2 and 1/3 code rate of FEC.
For the code rate of 1/2, it is achieved by bypassing the third parity chain with polynomial (165).

Proposal 8: Sub-block interleaving is not considered for Ambient IoT Device 1.
Proposal 9: For the number of block-level repetition, support {1, 2,4}.
Proposal 10: Support jointly indicate FEC and repetition number.

3GPP TSG RAN WG1 #121		2504089
St Julian’s, Malta, May 19th – 23rd, 2025
Agenda Item:	9.4.2
Source:	Fujitsu
Title:	Discussion on coding aspects
Document for:	Discussion

Conclusion
In this contribution, we have the following proposal and observation:
Observation 1:
Supporting at least one intermediate code rate between no FEC and 1/3 code rate can provide more flexibility to readers and bigger probability to achieve better network spectrum efficiency.
The 1/2 code rate is not perfect. If the AIoT item had time, it would be a good direction to further study which code rate is better than 1/2 as the intermediate code rate in between no FEC and 1/3 code rate.
Proposal 1: Support {1, 2, 4} for D2R block-level repetitions.

3GPP TSG RAN WG1 #121		R1- 2504099 
St.Julians, Malta, May 19th – 23rd, 2025

Source:	HONOR
Title:	Discussion on Physical channels design for Ambient IoT– other aspects
Agenda Item:	9.4.2
Document for:	Discussion and Decision

Conclusions
In this contribution, we provide our views on Physical channels design for Ambient IoT system. The following observations and proposals are given:
Proposal 1: If FEC is applied for a D2R transmission, only support code rate 1/3.
Proposal 2: For the number of D2R block level repetition, support Option 1 {1, 2}.
Proposal 3: The maximum value of Y for FDMA should equal to or less than 8.
Proposal 4: Use two parts signaling to indicate the D2R chip duration Tchip and SFS factor R values based on the table in which the first part indicates the Tb index and the second part indicates the available R values.

Observation 1: For D2R code rate, {1, 1/2, 1/3, 1/6} is supported according to the repetition number and FEC code rate.

3GPP TSG RAN WG1 #121		R1-2504206
St Julian’s, Malta, May 19th – 23th, 2025

Source:	OPPO 
Title:                     Discussion on physical channels design for A-IoT
Agenda Item:       9.4.2
Document for:	Discussion and Decision

Conclusion
In this paper, we discussed physical channel design for A-IoT, the following observations and proposals are given.
Proposal 1: For the down-selection of Tchip, Tb, and R to be supported in Rel-19 A-IoT, we propose keep R values in black colour and remove all red ones in Table 1.
Table 1: Suggested down-selection of Tchip, Tb, and R to be supported in Rel-19 A-IoT.
Observation 1: In R2D control information, indication of allocated SFS factors R for FDMA of D2R transmissions is equivalent to the indication of D2R chip durations Tchip, since one can be derived from the other based on the supported data rate (Tb). Therefore, for a given bit duration / data rate (Tb), it is sufficient to indicate in the R2D control information either the SFS factors R or the D2R chip durations Tchip.
Proposal 2: 
Same Tb, repetition factor and FEC coding rate are applied to all FDMed Msg.3 transmission in response to a PRDCH for Msg.2 transmission. 
Same Tb, repetition factor and FEC coding rate are applied to all FDMed Msg.1 transmission (if supported) in response to R2D transmission triggering CFRA. 
Observation 2: For Msg.1 transmission, the payload for indicating FDMA frequency positions in R2D control information can be significantly different between different indication approaches. In case of Tb = 266.67µs, (Btx_D2R = 15kHz), the maximum R2D payload is
Option 1 (Y only approach): 3 bits
Option 2 (index-based approach): at most 21 bits
Option 3 (bitmap-based approach): 7 bits
Observation 3: For Msg.3 transmission, since the reader needs to flexibly schedule devices in different SFS frequency positions, the Y only approach (Option 1) cannot provide a full control to the reader for scheduling a specific frequency position (R) to a given device (RN16). For Option 2 and Option 3, the required payload for indicating FDMA frequency positions in Msg.2 control information in case of Tb = 266.67µs, (Btx_D2R = 15kHz),
Option 1 (Y only approach): not applicable
Option 2 (index-based approach): 3*number of scheduled Msg.3 in one PRDCH bits
Option 3 (bitmap-based approach): 7 bits
Proposal 3: For scheduling of FDMed Msg.1 transmissions, the signalling design in the paging R2D control information should be based on the following:
Indication of Tb, repetition factor, and FEC coding rate (1 or 1/3)  (all devices should have the same data rate)
Indication of Y value (total number of allocated SFS frequency positions)
Proposal 4: For scheduling of FDMed Msg.3 transmissions, the signalling design in the Msg.2 R2D control information should be based on the following:
Indication of Tb , repetition factor, and FEC coding rate (1 or 1/3)(all devices should have the same data rate)
Indication of one or multiple of {device ID (RN16), R} 

Proposal 5: only coding rate {1/3, 1} is supported for A-IoT in Rel-19.
Proposal 6: The repetition factor supported for A-IoT in Rel-19 is {1,2,4}. One codepoint is reserved for later release.
Proposal 7: If L1 R2D control information is supported & carried by PRDCH, separate CRC is attached to L1 R2D control information and R2D data respectively is preferred. 

3GPP TSG RAN WG1 #121				R1-2504244
St Julian’s, Malta, May 19th – 23th, 2025

Agenda Item:	9.4.2
Source: 	LG Electronics
Title: 	A-IoT PHY layer design - line coding, FEC, CRC and repetition aspects
Document for:	Discussion and decision

Conclusion
	In this contribution, we shared our views on the PHY layer design aspects of line coding, FEC, CRC and repetition for Ambient IoT.
Proposal 1: Based on the D2R chip duration provided by a reader, an A-IoT device determines the small FS value for D2R transmission.
The information on D2R chip duration can be carried by R2D control information.
Proposal 2: Based on the D2R chip duration and the small FS factor R provided by a reader, an A-IoT device determines the data rate (1/Tb) for D2R transmission.
The information on the small FS factor R can be carried by R2D control information.
Proposal 3: The D2R FDM with the small FS can be scheduled with one of the following:
D2R chip duration Tc and the small FS factor R are indicated by R2D control information
D2R bit duration Tb and the small FS factor R are indicated by R2D control information
Proposal 4: The set of D2R chip duration values supported for D2R transmissions are determined considering the following aspects:
The minimum D2R chip duration value should be comparable to or no larger than 1 / (640*2 kHz) = 0.78 us
The maximum D2R chip duration value should be comparable to or no smaller than 133.33 us.
The D2R chip duration values should be easily derived by R2D chip duration values
Proposal 5: The minimum D2R bit duration for D2R transmission is 1.39 us
Proposal 6: The minimum D2R chip duration for D2R transmission is 0.69 us
Proposal 7: The maximum D2R chip duration for D2R transmission is 133.33 us
Proposal 8: For D2R small FS, support small FS factor R = {1, 2, 4, 8, 16, 32, 64, 128}.
Proposal 9: Support Ymax = 8 for A-IoT D2T transmissions.
Ymax: maximum number of multiplexed devices in frequency domain
Proposal 10: For D2R small FS, the set of combinations of supported Tc, Tb and R values are predefined in the spec and a reader indicates one combination (e.g., for CFRA) or a subset of the combinations (e.g., for CBRA) of the supported Tc, Tb and R values.
Proposal 11: Applying or not applying the FEC for D2R is explicitly indicated by a reader by R2D control information.
Proposal 12: For D2R, the convolutional code rate other than 1/3 is NOT supported in Rel-19 Ambient IoT.
Other code rates can be supported in combination with block-level repetitions, e.g., with the support of repetition number 2 and 4, the combined code rates of {1/2, 1/3, 1/4, 1/6} can be supported. 
Proposal 13: Support L1 control information for PRDCH, i.e., Option 2.
Proposal 14: Support separate CRCs for PRDCH, i.e., the first CRC for L1 R2D control information and the second CRC for R2D data which may or may not contain L2 control information.
Proposal 15: Consider fixed size CRC for L1 R2D control (6 or 16 depending on the L1 R2D control information size) and variable size CRC for R2D data.
CRC size for R2D data to be determined based on the R2D data size, or to be signaled via L1 R2D control
Proposal 16: For the number of D2R block-level repetitions, {1, 2, 4} repetitions are supported.

3GPP TSG RAN WG1 #121		R1-2504261
St Julian’s, Malta, May 19th – 23rd, 2025
Agenda item:	9.4.2
Source: 	MediaTek Inc.
Title: 	Discussion on A-IoT physical line coding, FEC, CRC, repetition aspects
Document for:	Discussion/Decision

Conclusion
Observation 1: For a worse residual SFO assumption of 1000ppm, it is observed the performance is unacceptable for D2R packet sizes (including TB and CRC-16) of {416, 816, 1016} bits.
Observation 2: For a better residual SFO assumption of 100ppm, it is observed the performance is able to achieve 1% BLER for D2R packet sizes (including TB and CRC-16) up to 1016 bits.
Observation 3: Depending on the evaluation assumptions, e.g., message size and residual SFO value at the reader side, it is observed a bad D2R performance is possible thus resulting in a poor coverage, which calls for the necessity of a large repetition number in addition to 1 and 2.
Observation 4: It would be safe to have one additional bit to enable the scheduling flexibility of a larger repetition number in addition to 1 and 2 considering the necessity.
Observation 5: The sustainability duration of device 1 is assumed to be long enough to support a larger repetition number in addition to 1 and 2.
Proposal 1: For the number of block-level repetitions, {1, 2, 4} repetitions are supported.
Note: When the number of block-level repetition is 1, it indicates no repetition.

3GPP TSG RAN WG1 #121                                                                            R1-2504288
St Julian’s, Malta, May 19th – 23rd, 2025

Agenda Item:	9.4.2
Source: 	InterDigital, Inc.
Title:	Remaining issues on coding aspects for Ambient IoT
Document for:	Discussion and Decision
1. 

Summary
This contribution has discussed remaining issues on coding aspects and the following is proposed:
Proposal 1: The following D2R chip duration Tchip, bit duration Tb, and SFS factor R are supported:

3GPP TSG RAN WG1 #121		             R1-2504319
St Julian’s, Malta, May 19th – 23rd, 2025

Agenda Item:	9.4.2
Source:	Apple
Title:	On remaining coding aspects for Ambient IoT
Document for:	Discussion/Decision

Conclusion
In this contribution, following observations/proposals have been made related to coding aspects for ambient IoT:

Proposal 1: Adopt following values for D2R chip duration Tchip, bit duration Tb, and SFS factor R:



Proposal 2: Adopt a 2-bit long codepoint to indicate the D2R bit duration Tb


Proposal 3: For signaling the SFS R factor, adopt one of the following options for boths cases of Y =1 and Y> 1
Option 1: A fixed size bitmap independent of the D2R bit duration Tb, where each bit corresponds to R =1, 4, 8, 16, 32, 64, 128, 256
Option 2: A variable size bitmap depending on the D2R bit duration Tb
For both options, “1” is used to indicate the application of corresponding SFS R factor from the bitmap

3GPP TSG RAN WG1 #121								R1-2504395
St Julian’s, Malta, May 19th – 23th, 2025

Source: Qualcomm Incorporated
Title: Physical channels design – line coding, FEC, CRC, repetition aspects
Agenda Item: 9.4.2
Document for: Discussion and Decision

Conclusion
In this tdoc, we made the following conclusions.

Proposal 1: Define Frequency shift as FS = 1/2*chip rate (Hz).
Observation 1:
Fractional number of device clock cycles still could be used for D2R transmission with frequency uncertainty.
Readers should allow certain levels of uncertainty of frequency shift considering 1) limited resolution of device clock cycle and 2) device clock SFO.
RAN4 should specify frequency tolerance considering these two aspects.
To support chip durations 0.69*2^n, 0.52*2^n for n=0,1, 2,…, clock speed of 1.92MHz, 2.16MHz or 2.88MHz are feasible and good options.

Observation 2:
0.69us can support bit rate up to 720kbps.
0.52us chip duration can support a bit rate up to 960kbps.
Observation 3:
Considering some device can be implemented based on method 1, it would be good to have 2^n ratio between R2D chip duration and D2R chip duration.

Observation 4:
If M=2 is indicated in R2D, D2R can easily support D2R chip duration of {133.33, 66.67, 33.33, 16.67, 8.33, 4.17, 2.08, 1.04, 0.52}us, which are black colored numbers.
If M=6, 12, or 24 is indicated in R2D, D2R can easily support D2R chip duration of {11.1, 5.56, 2.78, 1.39, 0.69}us.

Observation 5:
For low R2D data rate, black numbers {133.33, 66.67, 33.33, 16.67, 8.33, 4.17, 2.08, 1.04, 0.52} could be easily used for D2R, 
For high R2D data rate, red numbers {11.1, 5.56, 2.78, 1.39, 0.69} could be easily used.

Observation 6: Given that max D2R rate is likely to be used with M=24, D2R max bit rate could be 720kbps (with R=1) (chip duration of 0.69us is 1/4 of the R2D chip duration with M=24).

Proposal 2: Support max bit rate of 720kbps.

Observation 7: In D2R, 8 devices with a bit rate of 3.75kbps can be supported.

Proposal 3: Support max number of FDMed devices up to 8.

Proposal 4:
RAN1 supports the following table for D2R transmission.
Shortest Tb is 1.39us (720kbps).
The shortest chip duration is 0.52us.
Allows up to 8 FDM positions
Tb = {266.67, 133.33, 66.67, 33.33, 22.22, 11.11, 5.56, 1.39}
8 different bit duration to assign 3 bits for Tb indication
Tchip = {66.67, 33.33, 16.67, 8.33, 5.56, 4.17, 2.78, 2.08, 1.39, 1.04, 0.69, 0.52}


Proposal 5: Following restriction is applied between R2D M and D2R Tb.
R2D with M=2 can indicate D2R Tb >= 33.33
R2D with M>2 can indicate D2R Tb <=22.22

Observation 8:
Tb bit duration (or bit rate) is essential information to be signaled.
Y is not necessary to be signaled if reader allows all possible positions. If readers want to avoid or limit FS positions for some reason (e.g., reduce interference), then, Y could be directly or indirectly indicated.

Proposal 6: Down-select from following options for FD resource allocation
Option 1: Bit map-based scheme
Tb: bit rate for D2R transmission
Bitmap for FS position 
Option 2: Codepoint based scheme
Tb
Row index from a table TTb to indicate a pattern R=[R1, R2, … RY] 
Option 3: Starting position and gap indication
Tb
Y: number of FS positions for D2R transmission
Rmin : starting FS position in R value
G: Gap between two FS
Option 4: Rule-based scheme
Tb
Y: number of FS positions for D2R transmission
Rmax (optional)
Spec defines a simple rule to determine FS positions or R values

Proposal 7: For non-FDM case (e.g., unicast D2R data or D2R feedback), FDRA indicates
Tb (3bits)
R: predefined as R=1 for Tb=1.39us (720kbps) and R=2 other Tb value

Observation 9: For FDM resource allocation for Msg3 and CFRA, fewer positions could be used resulting in fewer bits for signaling.

Proposal 8: Max repetition factor is 2.

Observation 10: Convolutional code can be punctured to generate various code rates including 4/5, 2/3, 1/2, etc.

Observation 11: BLER performance of CC rate 1/2 and 1/3 are within 0.5 ~ 1dB.

Proposal 9 Support multiple coding rates for D2R CC 2/3 and 1/3.

Observation 12: For random access, additional processing time due to CRC for msg1 and 3 are not needed.

Observation 13: For command, processing time needs to consider CRC computation time.

Observation 14: Adding additional zeros at the end of block could convert LTE TBCC to ZTCC and reduce processing time by initializing shift register with zero tail bits.

Observation 15: Adding CRC before the last K-1 information bits can reduce processing time by initializing SR with information bits (instead of CRC).

Proposal 10: Regarding CRC position and processing time, discuss whether/how to improve current TBCC.

Proposal 11: For FEC bit collection, the sequence of FEC output bits  is generated by:
	 for k=0, …, D-1 and for i=0,1,2

3GPP TSG RAN WG1 #121                                   R1-2504434
St Julian’s, Malta, May 19th - 23rd, 2025

Source:	Sharp
Title:	Discussion on coding aspects
Agenda Item:	9.4.2
Document for:	Discussion and Decision

Conclusion
In this contribution, we discuss a few coding aspects of the A-IoT physical layer channel design, and make the following proposals.
Regarding down-selection between 1.39 μs and 1.04 μs for D2R bit length, adopt 1.39 μs.
In the table providing the potential values of D2R chip duration Tchip, bit duration Tb, and SFS factor R, remove the column for Tchip = 0.52 μs.
The maximum number (Ymax) of FDM’ed devices is 8.
In the table providing the potential values of D2R chip duration Tchip, bit duration Tb, and SFS factor R, for each D2R bit length, down-select to no more than Ymax values of R (and corresponding Tchip).
At least for the case of same data rate (i.e. same D2R bit length of Tb) for Y FDM’ed D2R transmissions in response to a R2D transmission, Tb and Y are indicated in the D2R scheduling information carried in the R2D transmission,
The allocated values of R are determined such that the spacing between any two adjacent values of R is maximized in the pre-defined set of R values for Tb.
For each value of R, the corresponding D2R chip duration is Tb/(2R).
If FEC is applied for a D2R transmission, for the code rate of FEC, adopt Option 1 (i.e. 1/3).
For the number of D2R block-level repetitions, adopt Option 1 (i.e. {1, 2}).

3GPP TSG RAN WG1 #121	                      	 R1-2504474
St Julian’s, Malta, May 19th – 23th, 2025

Agenda Item:	9.4.2
Source: 	ASUSTeK
Title:  	Discussion on A-IoT Physical channels design
Document for:	Discussion and Decision

Conclusion
In this contribution, we have following proposals for A-IoT physical channel design:
Proposal 1:  For PRDCH generation, L1 R2D control information and R2D data with separate CRC attachment are carried together in single PRDCH.
Proposal 2:  For CRC attachment, the 24 bits thresholds of number of information bits are applied to L1 R2D control information (if any) and R2D block separately.

3GPP TSG RAN WG1 #120bis							         R1-2504502
St Julian’s, Malta, May 19th – 23th, 2025

Source:	NTT DOCOMO, INC.
Title:	Discussion on coding and CRC aspects of physical channel design for Ambient IoT
Agenda Item:	9.4.2
Document for: 	Discussion and Decision

Conclusion
In this contribution, we discussed modulation aspects on physical channel design for A-IoT device. Based on the discussion, we made following observations and proposals.
Proposal 1: For small frequency shift of D2R transmission, discuss whether FDMA is supported for other D2R transmissions than Msg1 and Msg3.
Proposal 2: For D2R, the minimum value on information bit duration Tb should be 1.39μs.
Proposal 3: For D2R, the minimum value on chip duration Tchip should be 0.69μs.
Proposal 4: For D2R, the minimum value on small frequency shift factor R should be 1.
Proposal 5: For D2R, supported values on small frequency shift factor R should be 2n, where n=0, 1, 2,…,7.
Proposal 6: For D2R, the maximum value on chip duration Tchip should be 133.33μs.
Proposal 7: For D2R, supported values on chip duration Tchip should be {133.33, 66.67, 33.33, 16.67, 8.33, 4.17, 2.08, 1.04, 0.69}μs.
Proposal 8: For D2R, chip duration Tchip and small frequency shift factor R can be indicated
Option 1: independently, e.g., by codepoint/bitmap.
Option 2: by joint indication, e.g., codepoint indicates a predefined combination of R and Tchip.
Proposal 9: For FEC on PDRCH, other code rate than 1/3, e.g., 1/2 by puncturing, is not necessary.
Proposal 10: For D2R, FEC should be applicable to any PDRCH transmission regardless of message type.
Whether to apply FEC can be indicated in any R2D which schedules D2R.
Proposal 11: For D2R, for repetition factor of block-level repetition, it is not necessary to support multiple repetition factors, i.e., specify single value of repetition factor for D2R block-level repetition.
Observation 1: For D2R, 15 m coverage can be achieved with 5-7 kbps data rate.
Proposal 12: For D2R, for repetition factor of block-level repetition, consider maximum chip length Tchip, information bit length Tb and corresponding data rate.
Proposal 13: For D2R, for repetition factor of block-level repetition, 2 times repetition should be supported.
Proposal 14: For D2R, whether to apply block-level repetition should be controlled by reader.
Proposal 15: For D2R, block-level repetition should be applicable to any PDRCH transmission regardless of message type.
Whether to apply block-level repetition can be indicated in any R2D which schedules D2R.

3GPP TSG RAN WG1 #121	 R1-2504634
St Julian’s, Malta, May 19th – May 23rd, 2025

Agenda item:     9.4.2
Source:               IIT Kanpur
Title:                    Discussion on other aspects of physical channel design for AIoT
Document for:    Discussion and Decision

Conclusion
This paper provides the following observations and proposals:
Proposal 1: In addition to the existing 1/3 code rate, a code rate of 1/2 should be supported for FEC in D2R transmissions.
Proposal 2: Block-level repetition factor 4 should not be supported for the D2R link in Rel-19.
Proposal 3: If L1 control information is supported, a separate CRC should be used for control information and R2D data.
4. 

3GPP TSG RAN WG1 #121			R1-2504749
St Julian’s, Malta, May 19th – 23th, 2025


Source: 	Moderator (CMCC)
Title:	Summary #1 for coding aspects of physical channel design
Agenda:	9.4.2
Document for:	Discussion & Decision

Conclusion
RAN1 will not address the FFS in the agreement from RAN1#120:

Agreement
When CRC is attached to a PRDCH or PDRCH transmission, 
When the number of information bits is ≤ X bits, CRC-6 is used. Otherwise, when the number of information bits is > X bits, CRC-16 is used. Down-selection by RAN1#120bis from the following for X considering the balance of overhead and probability of undetected error:
Alt. 1: 24
Alt. 2: 56
FFS impact of segmentation, if any
Note: impact may not be in RAN1

Agreement
The potential values of D2R chip duration Tchip, bit duration Tb, and SFS factor R, are shown in the following table:
FFS further down-selections of Tchip, Tb, and R to be supported
Note: Detailed indication signaling of D2R scheduling information is discussed in AI 9.4.4.

Agreement
For block-level repetition of a D2R transmission, the repeated blocks are transmitted in the single PDRCH of the D2R transmission.

RAN1#121
TBD

3GPP TSG RAN WG1 #121			R1-2504750
St Julian’s, Malta, May 19th – 23th, 2025


Source: 	Moderator (CMCC)
Title:	Summary #2 for coding aspects of physical channel design
Agenda:	9.4.2
Document for:	Discussion & Decision

Conclusion
RAN1 will not address the FFS in the agreement from RAN1#120:

Agreement
When CRC is attached to a PRDCH or PDRCH transmission, 
When the number of information bits is ≤ X bits, CRC-6 is used. Otherwise, when the number of information bits is > X bits, CRC-16 is used. Down-selection by RAN1#120bis from the following for X considering the balance of overhead and probability of undetected error:
Alt. 1: 24
Alt. 2: 56
FFS impact of segmentation, if any
Note: impact may not be in RAN1

Agreement
The potential values of D2R chip duration Tchip, bit duration Tb, and SFS factor R, are shown in the following table:
FFS further down-selections of Tchip, Tb, and R to be supported
Note: Detailed indication signaling of D2R scheduling information is discussed in AI 9.4.4.

Agreement
For block-level repetition of a D2R transmission, the repeated blocks are transmitted in the single PDRCH of the D2R transmission.

RAN1#121

Agreement
For D2R transmission,
The minimum Tb is 1.39μs.
Support at least the following values of Tb, Tchip, and R from the table agreed in RAN1#120bis.
Note: This does not imply the device to pre-store the table.


Agreement
For bit collection after FEC, the output bits for each input bit are arranged sequentially in accordance with the input bits, e.g., for input bits , the output of the FEC is , with the code rate of 1/3.

Agreement
For attaching the CRC, the parity bits are appended to the end of the input bits, according to the order in TS38.212.

3GPP TSG RAN WG1 #121			R1-2504751
St Julian’s, Malta, May 19th – 23th, 2025


Source: 	Moderator (CMCC)
Title:	Summary #3 for coding aspects of physical channel design
Agenda:	9.4.2
Document for:	Discussion & Decision

Conclusion
RAN1 will not address the FFS in the agreement from RAN1#120:

Agreement
When CRC is attached to a PRDCH or PDRCH transmission, 
When the number of information bits is ≤ X bits, CRC-6 is used. Otherwise, when the number of information bits is > X bits, CRC-16 is used. Down-selection by RAN1#120bis from the following for X considering the balance of overhead and probability of undetected error:
Alt. 1: 24
Alt. 2: 56
FFS impact of segmentation, if any
Note: impact may not be in RAN1

Agreement
The potential values of D2R chip duration Tchip, bit duration Tb, and SFS factor R, are shown in the following table:
FFS further down-selections of Tchip, Tb, and R to be supported
Note: Detailed indication signaling of D2R scheduling information is discussed in AI 9.4.4.

Agreement
For block-level repetition of a D2R transmission, the repeated blocks are transmitted in the single PDRCH of the D2R transmission.

RAN1#121

Agreement
For D2R transmission,
The minimum Tb is 1.39μs.
Support at least the following values of Tb, Tchip, and R from the table agreed in RAN1#120bis.
Note: This does not imply the device to pre-store the table.


Agreement
For bit collection after FEC, the output bits for each input bit are arranged sequentially in accordance with the input bits, e.g., for input bits , the output of the FEC is , with the code rate of 1/3.

Agreement
For attaching the CRC, the parity bits are appended to the end of the input bits, according to the order in TS38.212.

3GPP TSG RAN WG1 #121			R1-2504752
St Julian’s, Malta, May 19th – 23th, 2025


Source: 	Moderator (CMCC)
Title:	Summary #4 for coding aspects of physical channel design
Agenda:	9.4.2
Document for:	Discussion & Decision

Conclusion
RAN1 will not address the FFS in the agreement from RAN1#120:

Agreement
When CRC is attached to a PRDCH or PDRCH transmission, 
When the number of information bits is ≤ X bits, CRC-6 is used. Otherwise, when the number of information bits is > X bits, CRC-16 is used. Down-selection by RAN1#120bis from the following for X considering the balance of overhead and probability of undetected error:
Alt. 1: 24
Alt. 2: 56
FFS impact of segmentation, if any
Note: impact may not be in RAN1

Agreement
The potential values of D2R chip duration Tchip, bit duration Tb, and SFS factor R, are shown in the following table:
FFS further down-selections of Tchip, Tb, and R to be supported
Note: Detailed indication signaling of D2R scheduling information is discussed in AI 9.4.4.

Agreement
For block-level repetition of a D2R transmission, the repeated blocks are transmitted in the single PDRCH of the D2R transmission.

RAN1#121

Agreement
For D2R transmission,
The minimum Tb is 1.39μs.
Support at least the following values of Tb, Tchip, and R from the table agreed in RAN1#120bis.
Note: This does not imply the device to pre-store the table.


Agreement
For bit collection after FEC, the output bits for each input bit are arranged sequentially in accordance with the input bits, e.g., for input bits , the output of the FEC is , with the code rate of 1/3.

Agreement
For attaching the CRC, the parity bits are appended to the end of the input bits, according to the order in TS38.212.

Agreement
For the number of block-level repetitions, {1, 2} are supported.
Note: When the number of block-level repetition is 1, it indicates no repetition.

Agreement
For indication of frequency domain resources for Msg 1 transmissions when Y≥1, the reader indicates
a single bit duration Tb which is same for all frequency domain resources
a set of R values, where the possible R values correspond to the agreed table of values of Tb, Tchip, and R
note: the set of R values could be signalled using a bitmap
The detailed signalling design is left to RAN2.


Agreement
For frequency domain resource for Msg 3 transmission determined based on explicit indication in the PRDCH for Msg 2 transmission for one or multiple devices, the reader indicates:
a single bit duration, which is same for all frequency domain resources,
a set of R values, where the possible R values correspond to the agreed table of values of Tb, Tchip, and R
note: the set of R values could be signalled using a bitmap
The mapping relationship between device and its Msg 3 frequency domain resource is left to RAN2.
Note: Device could determine its R value for Msg 3 transmission based on its order of random ID in Msg 2
The detailed signalling design is left to RAN2.