1. 3GPP RAN1 status on LAA and NR-Unlicensed
Month Year
doc.: IEEE yy/xxxxr0
March 2018
3GPP RAN1 status on LAA and NR-Unlicensed
Date:
Authors:
Name
Affiliations
Address
Phone
Sindhu Verma
Broadcom
Shubhodeep Adhikari
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
March 2018
Abstract
This presentation provides the current status of LAA and NR-Unlicensed in 3GPP with a focus on fair coexistence with
John Doe, Some Company

3. Month Year
doc.: IEEE yy/xxxxr0
March 2018
Outline
The presentation discusses the following topics with respect to fair coexistence .
Further enhancements to LAA (feLAA)
Background
Additional partial ending positions in a UL subframe
Autonomous UL (AUL)
eNB to UE COT sharing
UE to eNB COT sharing
Multiple autonomous CAT4 LBT transmissions without waiting for feedback
Discussion
NR-Unlicensed (NRU)
Study Item objectives
Spectrum
Simulation methodology
Deployment scenarios
Next Steps
John Doe, Some Company

4. March 2018
FeLAA: Background
The FeLAA work item commenced in 3GPP RAN1 in April, The objective was to enhance LAA DL and UL performance with respect to the following aspects:
Increasing Starting and Ending positions for DL and UL transmissions
Legacy LAA supports 2 DL starting positions (symbols #0,#7) and 6 DL ending positions (symbols #3,#6,#9,#10,#12,#13)
Legacy eLAA supports 1 UL starting position (symbol #0) and 2 UL ending positions (symbols #12,#13)
Supporting Autonomous transmission on the UL
Legacy eLAA supports only grant-based scheduled UL transmissions where a UL transmission must be preceded by a grant from the eNB
The Work item concluded in the RAN1 #92 (Feb-Mar 2018) meeting last week

5. FeLAA: Multiple ending positions in a UL subframe
March 2018
FeLAA: Multiple ending positions in a UL subframe
This was the only sub-topic remaining regarding multiple starting and ending positions in a DL/UL subframe
Previous conclusions were as follows:
No additional starting positions in a DL subframe
No additional ending positions in a DL subframe
1 additional starting position (symbol #7) in a UL subframe
1 additional ending position (symbol #6) in a UL subframe while ending positions at symbols #3,#10 are FFS
Following was the conclusion regarding multiple ending positions in a UL subframe in RAN1 92:
Additional ending position at symbol #3 in a UL subframe is also supported
The number of bits (Transport Block Size) that can be carried in the partial subframe ending at symbol #3 is set to ⅛ of what can be carried in the full subframe. This is still sufficient to transmit small chunks of data which would have otherwise resulted in occupation of the entire slot.
Ending position at symbol #10 was not agreed to as it would have increased the number of signalling bits; there was scope for indicating one additional UL ending position by reusing the existing signalling procedure; #3 was chosen over #10 as it adds more value relative to the existing ending positions (#6, #12, #13).

6. FeLAA: AUL: eNB to UE COT sharing (1)
March 2018
FeLAA: AUL: eNB to UE COT sharing (1)
COT sharing is a mechanism (enabled by ETSI-BRAN) wherein one device acquires a COT using usual CAT4 LBT and another device shares it using a 25us LBT with a gap provided the amount of transmission does not exceed the MCOT limit for the given priority class
The purpose of this mechanism was to allow a concession for LAA UL in which an eNB must send a grant to the UE before it can transmit on the UL and the delay between the grant and the corresponding UL transmission is at least 4ms.
This pause of 4 ms is not accounted in the COT duration
However, many companies also wanted to use this feature for AUL which suffers from none of the limitations that originally existed for LAA UL. So, if eNB acquired a COT and transmitted on the DL without exhausting the full COT, it can indicate to all UEs via PDCCH. The UEs can then transmit AUL transmissions with just 25 us LBT in the configured period
Nothing in new ETSI regulations prevents this kind of an operation

7. FeLAA: AUL: eNB to UE COT sharing (2)
March 2018
FeLAA: AUL: eNB to UE COT sharing (2)
Our position was that if COT sharing is allowed for AUL, the following should be ensured:
The data transmitted on the UL using AUL by a UE should follow the traffic multiplexing rules as defined in legace (e)LAA and the ETSI regulations which is that it should be of equal or higher priority than what was used to acquire the COT
If the eNB did not transmit any packets on the DL in a COT before sharing the COT with the UEs for AUL, failure to decode AUL transmissions in the shared period should still lead to CWS update at the eNB. This is important because the eNB cannot be certain of whether the UE transmits data using AUL or not and failure to decode it may result from both, lack of transmission or collision.
There was a lot of opposition to our proposals with arguments that the UE MAC will need to change in order to handle traffic multiplexing rules.
However, the final agreements that happened make LAA even more conservative than what we proposed due to the reluctance of companies to make minor changes in the MAC specification:
The eNB can share its COT with a UE for AUL only if it acquired the COT with the lowest priority (AC_BK priority class) and so, the UE does not have to ensure anything regarding traffic multiplexing
The eNB cannot share its COT with a UE for AUL if it does not transmit any packets on the DL in the same COT

8. FeLAA: AUL: UE to eNB COT sharing (1)
March 2018
As mentioned before, COT sharing was introduced to help LAA UL because it always required a grant and followed the grant with a delay
However, the changes in ETSI regulations that permitted this did not prevent any reverse COT sharing i.e. from the UE to the eNB
Motivated by this, many companies in 3GPP proposed that the any COT acquired by a UE for AUL transmission, if not fully exhausted, should be allowed to be shared with the eNB who in turn can use it for transmission of control or data UE to any UE with a pause and just 25 us LBT as long as it transmits for the minimum duration required to transmit data of equal or higher priority. The example of RDP in was also cited by them.
We strongly argued against it with the following reasons:
COT sharing principle was introduced only to help LAA UL
LAA eNB is in full control of which UEs are allowed to perform AUL and is also aware of the interference situation at each UE due to licensed channel reports. Hence, it is possible for it to allow UEs with less interference to perform AUL only to share the COT with it so that it can transmit with only 25 us LBT
This will lead to transmission of many messages in LAA DL with only 25 us LBT in contrast with what happens in where only channel switch and TIM can be transmitted with fixed LBT.
The clause on minimum duration of transmission above is also a bit ineffectual because of the granularity of transmissions that exists in LAA
eNB transmit power is typically higher than the UE transmit power

9. FeLAA: AUL: UE to eNB COT sharing (2)
March 2018
FeLAA: AUL: UE to eNB COT sharing (2)
However, we also thought that UE to eNB COT sharing could be permitted for only the limited case of the eNB transmitting feedback for the AUL transmission from the UE with just 25 us LBT and with a gap of exactly equal to 25 us.
Many companies wanted to multiplex this transmision with control/data transmission to the UE which acquired the COT as well as to other UEs. They also wanted to allow 16 us gap without LBT.
However, we argued against no-LBT since LAA has not hidden node protection mechanisms.
The final agreement is as follows:
The UE may share its COT with the eNB who may only transmit with a 25 us gap and a 25 us LBT in that gap
The eNB transmission is limited to 2 OFDM symbols
The eNB transmission must contain feedback for AUL transmission to the UE which acquired the COT and transmitted AUL

10. March 2018
FeLAA: AUL: Multiple CAT4 LBT transmissions without waiting for feedback (1)
In LTE without shortened processing time enhancements and in LAA, HARQ feedback for any transmission in subframe n is expected to be received not earlier than subframe n+4
In case of scheduled UL, a CAT4 LBT transmission can occur only on receiving a grant which is also a mode of feedback. However, in AUL there can be a CAT4 LBT transmission without a grant which means there is a possibility of having multiple consecutive CAT4 LBT transmissions without any intervening grant or feedback.
This therefore requires the CWS for each of these transmission to be determined since there is no feedback received.
Many companies in 3GPP proposed that for these cases, the same CWS as the previous CAT4 LBT transmissions should be used continuously upto a very large time delay (For example, Qualcomm proposed 40 ms). Their point was about not to constrain the UL performance and not to constrain the eNB to send feedback soon.
We pointed out that the choice of CWS is not a technology performance metric but a metric that ensures fair coexistence and is also mandate by ETSI regulations to evolve in a certain way. For example, regulations state that if it cannot be “confirmed that at least one transmission that started at the beginning of the Channel Occupancy Time was successful”, the CWS must double. This is also what is followed in

11. March 2018
FeLAA: AUL: Multiple CAT4 LBT transmissions without waiting for feedback (2)
However, LAA does have the limitation that if the 2 CAT4 LBT transmissions start within 4 subframes of each other, there is no way for any eNB to send feedback.
Hence, our proposal was that if a CAT4 LBT transmission starts without receiving feedback for one or more previous CAT4 LBT transmissions, for each previous CAT4 LBT transmission that started more than 6 subframes ago, the CWS should be doubled in order of the transmissions. We also pointed out that in EU, irrespective of this feedback delay, the CWS must be doubled for any CAT4 LBT transmission without feedback
The final agreement is as follows:
For each previous CAT4 LBT transmission more than N subframes ago and that did not have feedback, the CWS will be doubled in order of the transmissions. N is 0 in EU. N is max(5, corresponding UL burst length +1) if absence of Wi-Fi cannot be guaranteed. N is 10 otherwise.
If feedback is received for any of these bursts later, the CWS is again computed by reverting to the value for the earliest such burst and then resetting/doubling in order of the bursts

12. The FeLAA WI concluded last week in 3GPP RAN1 #92
March 2018
FeLAA: Discussion
The FeLAA WI concluded last week in 3GPP RAN1 #92
It led to the definition of
1 additional starting position (symbol #7) in UL and 2 additional ending positions (symbols #3,#6) in UL
Autonomous UL which is a very useful feature for LAA in the following ways
UEs need not wait for the eNB grant to transmit
Multiple UEs can be allocated the same opportunities and they contend with one another to transmit it
Each UE start position is preconfigure with an offset of a certain sub-symbol duration so that the probability of collision is minimized and there is automatic prioritization
From the perspective of fair coexistence
The additional starting and ending positions in UL help
AUL makes LAA UL more aggressive than Release 14 LAA UL. However, it has been ensured that it does not violate any principles of fair coexistence.

13. NR-Unlicensed: Background
March 2018
NR-Unlicensed: Background
The NR-Unlicensed Study Item started in 3GPP RAN1 #92 (Feb, 2018)
It was preceded by an NRU Workshop and also discussions among interested companies to collate views on the following topics:
Spectrum
Simulation Methodology
Deployment Scenarios
The NRU sessions in RAN1 were attended by a large number of companies including prominent cellular and cable operators.
Note: In the subsequent slides, text copied from RAN1 agreements are marked in blue.

14. NRU: Study Item Objectives
March 2018
NRU: Study Item Objectives
The following text was agreed regarding the SI objective after a lot of debate:
The study targets identification of additional functionality needed for a PHY layer design (except channel access procedures) for operation in unlicensed spectrum that may be applicable over a particular frequency range (e.g., sub-7 GHz, GHz, > 52.6 GHz).
FFS: The definition of the frequency ranges
Note: Optimizations for a particular frequency band may be necessary.
Note: Channel bandwidths below 5 MHz are not targeted
The study targets the design of channel access procedures for frequency bands based on coexistence and regulatory considerations applicable to the band.
Note: The study includes identification of procedures for technology neutral channel access for frequency bands that may become available subject to regulations.
The study assumes regulation will provide the framework concerning the protection for the technologies not using unlicensed access in those bands.

15. March 2018
NRU: Spectrum
In the discussion that preceded the RAN1 meeting, a clear support for prioritizing 5 GHz and 60 GHz for NRU was evident. Many companies also want to include 6 GHz.
However, in the meeting, the following was agreed:
From RAN1 design perspective, the study is not limited to a particular unlicensed band
Note: This does not have any implications on prioritizations between unlicensed bands
Note: The study does not target sub-1GHz unlicensed bands
Note: This is a Study Item and the final bands for NRU will eventually get decided in RAN4 subject to operator requests, regulations, etc.

16. NRU: Simulation Methodology (1)
March 2018
NRU: Simulation Methodology (1)
3GPP 5G Channel model (in ) to be used
Scenarios
Indoor sub-7GHz, 2 operators
Outdoor Sub-7 GHz, 2 operators
Indoor mmW, 2 Operators
Outdoor mmW, 2 operators
Stadium scenario for sub-7GHz, 2 operators, can be optionally considered by interested companies.
RAN1 prioritizes the simulation for sub-7 GHz band. It does not preclude evaluation for above 7 GHz.
Deployment scenarios to simulate
CA between NR licensed cell and NR unlicensed cell
DC (with LTE and with NR) SA
An NR cell with DL in unlicensed band and UL in licensed band

17. NRU: Simulation Methodology (2)
March 2018
NRU: Simulation Methodology (2)
Coexistence with other networks (e.g. WiFi, LAA LTE, NR-U)
When coexistence with WiFi is evaluated, only consider deployed WiFi systems (e.g. 11ac for 5 GHz)
Fairness criterion for coexistence with 11ax can be further discussed at plenary level
The coexistence evaluation applies to 5GHz band (11ac) and 60GHz (11ad)
From SID: NR-based operation in unlicensed spectrum should not impact deployed Wi-Fi services (data, video and voice services) more than an additional Wi-Fi network on the same carrier
For sub-7 GHz bands, coexistence simulations will be performed using technology neutral assumptions (eg. channel access mechanism) at an arbitrary carrier frequency in 5GHz band for application to bands other than 5GHz which may become available subject to regulations
Note: The study assumes regulation will provide the framework concerning the protection for the technologies not using unlicensed access in those bands

18. NRU: Simulation Methodology (3)
March 2018
NRU: Simulation Methodology (3)
Network Topology :
Indoor sub7GHz, choose one of the following options
Option 1: Reuse indoor hotspot topology and allocating half of the gNBs to each operator (6+6)
Option 2: Reuse indoor hotspot topology but further reduce gNB density (3+3)
Option 3: Based on IEEE indoor enterprise model with modifications
Outdoor sub7GHz
NR dense urban scenario with two layers, but only consider the micro layer
Randomly drop one micro layer per operator
Indoor mmW
Reuse indoor sub7GHz topology
Parameter changes may be needed and submitted together with simulation results
Outdoor mmW
Reuse outdoor sub7GHz topology

19. NRU: Simulation Methodology (4)
March 2018
NRU: Simulation Methodology (4)
Notes:
Some companies did not want to evaluate coexistence afresh. However, we proposed that coexistence evaluations for NR-U be included for 11ac and 11ad. Coexistence with 11ac in 5 GHz and 11ad in 60 GHz will be evaluated using the criteria “NR-based operation in unlicensed spectrum should not impact deployed Wi-Fi services (data, video and voice services) more than an additional Wi-Fi network on the same carrier”.
This also means that we need to devise appropriate topologies for coexistence evaluations with 11ac and 11ad:
The network topology for coexistence evaluations in the LAA simulation methodology had 1% of links in the Indoor model and 7% of links in the Outdoor model with RSSI < -72dBm respectively.
This was pointed out by us in 3GPP, in LSs from IEEE and in WFA workshops.
So, for evaluations with NR-U, it has to be ensured that the network topology has a significant number of links below -72 dBm.
We have sent an to the RAN1 reflector providing the RSSI CDFs of some deployed Wi-Fi networks and from the 3GPP Indoor and Outdoor network model used in LAA evaluations.

20. NRU: Simulation Methodology (5)
March 2018
NRU: Simulation Methodology (5)
Notes:
HPE: Data presented from highly optimized enterprise-grade networks planned, deployed, and administered by a single entity and relatively isolated from external interference. These are highly favorable conditions for Wi-Fi and may not be representative of far more challenging public or residential deployments.
San Francisco Bay Area enterprise covering an area of 430,000 ft2 (37,680 m2) with 2,800 employees and 203 APs. 20% of own BSS links are below -72dBm while 60% of other BSS links are below -72dBm.
Levi’s Stadium in Santa Clara, CA. The stadium has a seating capacity of 68,500 and was 98.5% full with attendance of 67, % of own BSS links are below -72dBm and 95% of other BSS links are below -72dBm.
CableLabs: DL and UL signal strength measurements from Wi-Fi networks used by multiple cable operators. It is a collection of over 1 million measurement samples from 13,000 distinct outdoor APs for the duration of multiple days. DL: 80% of links are below -72dBm. UL: 85% of links are below -72dBm
Boingo: Field measurements collected from Wi-Fi networks operated by Boingo from major North American airports serving 600 million customers annually. Data collected over 6 months. 32.8% of links are below -72dBm.
Ericsson: Enterprise office deployment serving ~1000 people measured over 7 days. 4-5% of links are below -72dBm

21. NRU: Deployment Scenarios
March 2018
NRU: Deployment Scenarios
The following was agreed regarding the Deployment scenarios to be studied:
Study the additional functionality needed beyond the specifications for operation in licensed spectrum in the following deployment scenarios.
Carrier aggregation between licensed band NR (PCell) and NR-U (SCell)
NR-U SCell may have both DL and UL, or DL-only.
Dual connectivity between licensed band LTE (PCell) and NR-U (PSCell)
Stand-alone NR-U
An NR cell with DL in unlicensed band and UL in licensed band
Dual connectivity between licensed band NR (PCell) and NR-U (PSCell)
Note (for the minutes): Some companies believe that a prioritization among the agreed deployment scenarios may be necessary.
Note:
Stand-alone NRU and NRU as a part of Dual Connectivity make it a direct competition for Wi-Fi since with these, NRU cells can be deployed without any licensed carrier fallback or without any ideal backhaul with the licensed carrier.
Legacy cellular operators are opposed to NRU stand-alone and do not want this design to proceed in 3GPP. This is because they are apprehensive of competition from newer operators who can use NR-U standalone for limited cellular operations.

22. March 2018
NRU: Discussion
NR-U is potentially a much more potent competitor to than LAA.
The “licensed assisted” nature of LAA limits its deployment to cases where LAA is either colocated with a licensed eNB or has an ideal backhaul with a licensed eNB. This rules out the majority of scenarios where is currently deployed.
LAA PHY/MAC has features derived from legacy LTE (long 71us symbol duration, limited number of starting and ending positions in a subframe, long 4ms HARQ RTT) that make is less flexible for Indoor Hotspot deployments.
In contrast:
NR-U will have a more flexible and efficient PHY/MAC (shorter symbol durations, start and end positions in every symbol position, shorter HARQ RTT)
If SA and DC are approved it will also be possible to deploy NR-U in every configuration where is currently deployed.
NR-U will have an additional advantage that the same PHY/MAC with flexible configurations can be deployed across all current and future unlicensed bands unlike

23. March 2018
NRU: Next Steps
The effort required to ensure fair coexistence between NR-U and is much more than what was required for LAA
The number of evaluation scenarios are much higher:
Licensed assisted, Dual connectivity, Standalone
5 GHz, 6 GHz, 60 GHz, other bands
LAA channel access (as baseline) and additionally technology neutral channel access
For LAA, since 2014 it has been mostly Broadcom that has been participating in 3GPP to ensure fair coexistence between LAA and
The much larger scope of NR-U and also the fact that it is potentially a more potent competitor to makes it necessary for more companies with interests to participate in 3GPP and also contribute to technical evaluations in order to achieve fair coexistence between NR-U and
Please also note that unlike LAA and ac, coexistence between NR-U and ax are likely to be bidirectional and hence technically more challenging.

24. References March 2018 [1] Chairman’s notes RAN1 92 final
Month Year
doc.: IEEE yy/xxxxr0
March 2018
[1] Chairman’s notes RAN1 92 final
[2] R Companies’ views on candidate spectrum for NR unlicensed operation Intel Corporation, Sony, AT&T, Nokia, Nokia Shanghai Bell, Ericsson, Charter Communications, Qualcomm Incorporated, ZTE, Sanechips, LG Electronics, Motorola Mobility, Lenovo, InterDigital, Huawei, HiSilicon, Samsung, Verizon, MediaTek Inc., Comcast, CableLabs, CATT, Deutsche Telekom, T-Mobile USA, Oppo, NTT DOCOMO
[3] R Summary of unofficial discussion on NR-U simulation methodology Qualcomm Incorporated
[4] R Companies’ views on deployment scenarios for NR unlicensed operation Nokia, AT&T, CableLabs, Charter Communications, Comcast, Deutsche Telecom, Ericsson, HiSilicon, Huawei, Intel, InterDigital, Lenovo, LG Electronics, MediaTek, Motorola Mobility, Nokia Shanghai Bell, NTT DOCOMO, Qualcomm, Samsung, Sanechips, Sony, T-Mobile US, Verizon, vivo, ZTE
John Doe, Some Company