Understanding MulteFire’sRadio Link

Dr. Tamer Kadous, Radio Workgroup Chair

Agenda

• Coexisting in unlicensed spectrum

• MulteFire Technology—extensions added to 3GPP LAA and eLAA

• MulteFire performance advantages and results

• Summary

Multiple technologies will coexist in unlicensed spectrum

1) Licensed-Assisted Access (LAA), also includes enhanced LAA (eLAA); 2) LTE Wi-Fi Link Aggregation (LWA); 3) LTE Wi-Fi radio level integration with IPsec tunnel (LWIP); 4) 802.11ac / .11ad / .11ax/ .11ay

Wi-Fi4Evolving for enhanced performance and expanding to new usage models, used today as neutral host

Licensed SpectrumExclusive use

Unlicensed SpectrumShared use

Aggregation

MulteFireBroadens LTE ecosystem to enhanced and new deployment opportunities, suitable for neutral host

LWA2, LWIP3

Targeting mobile operators leveraging existing carrier Wi-Fi deployments

LTE-U / LAA1

Targeting mobile operators using LTE in unlicensed spectrum for new small cell deployments

anchor

MulteFire performance advantages

1) Signal-to-interference-plus-noise ratio (SINR); 2) Media Access Control (MAC) Layer; 3) Handover (HO); 4) Radio link failure (RLF)

Coverage• Retains LTE’s deep coverage

characteristics

• Targets control channels to cell edge SINR1 of -6dB

• 5-6dB link budget advantage over Wi-Fi

Capacity• Leverage LTE link efficiency

and MAC2

• Significant gains (2X) over 802.11ac baseline

• Comparison with .11ax under investigation

Mobility• Brings carrier-grade LTE

mobility to unlicensed

• Seamless & robust mobility

• Service continuity to WAN

• Significantly better than Wi-Fi, esp. outdoor, 50 km/h

Robustness• More predictable & robust

performance than Wi-Fi

• Forward HO3 enables recovery when RLF4

• Enhanced RLF4 triggers

• Mature SON techniques

MulteFire technology is based on 3GPP LAA and eLAAExtends eLAA—uplink & downlink—to operate without anchor in licensed spectrum

3GPP Rel. 13

3GPP Rel. 14

Uplink waveform & channelsFlexible frame structureUL

2HARQ

3, scheduling enhancements

Supplemental downlink + HARQ3

LBT4

coexistence in unlicensedMulti-carrier operation

Enhanced discovery signalsRobust procedures: mobility, paging, RA

1...

Robust & efficient UL2

control channels

Advanced LTE air-interfaceLTE TDD

MulteFire Alliance Operate without licensed anchor

eLAA:+Uplink

LAA:Downlink

LTE

New features

1) Random Access; 2) Uplink; 3) Hybrid automatic retransmission request; 4) Listen before talk

Flexible frame structures supporting any UL/DL traffic mix

D S U U U U U U U U

D D D D D D D D S U

D D D D D D S U U U

Allows any Uplink(U) or Downlink (D)sub frame mix

D S U U U D S U U U0

D S U U D D S U U D1

D S U U U D D D D D3

D S U U D D D D D D4

D S U D D D D D D D5

D S U U U D S U U D6

Maximizes efficiency for any traffic, from uplink-heavy to downlink-heavy

D S U D D D S U D D2

D D D D D D D D D D

D U U U U U U U U U

Rel.14: numerous TDD configurations,Dynamical switching

Rel.8: limited TDD configurations,Semi-static switching

Dynamic switching between configurations on a per TxOP basis

… … … … … … … … … …

D S U U U U D D D D

… … … … … … … … … …

… … … … … … … … … …

TxOP1 example with 10 ms

TxOP1 example with 10 ms

1) Transmit opportunity (TxOP)

Flexible frame structure for more efficient LBT1

Fixed frame structure — wait for next downlink sub-frame (D), fixed to system time

Flexible frame structure — any sub-frame can be downlink (D), no need to wait

Fixed structure2

Over-the-air

U U U D D D D S U U U U U D D D D S U U U U U D D D D S U U U U U D D D

DD D U U U U U D D D D D U U U U US S

eCCA1 cleared eCCA cleared CCA

May lose medium while waiting for D

Over-the-air UD D D S U U U U D D D D D D D D UD S

eCCA cleared eCCA cleared

1) Listen before talk (LBT) using enhanced Clear Channel Assessment (eCCA); 2) D = Downlink (DL), U = Uplink (UL), and S = Special sub-frame (mix of UL, DL and guard period)

Uplink scheduling enhancements improves performanceEfficiently support flexible frame structure

…D D D D D D D S U U D S U U U U U U

eCCA eCCA

TxOP1

Single-TTI UL grantFirst uplink UL sub-frame that can be

granted from same TxOP (n 4)

Multi-TTI UL grantsAllows multiple UL sub-frames to be granted by a single grant.

U

Cross TxOP UL grantsEnables UL heavy configurations

UL sub-frames that cannot be granted within same TxOP

1) Transmit opportunity (TxOP)

U

U D U S UU US

S

Asynchronous UL HARQ handles unknown timing of LBT

Synchronous UL HARQ—fixed timing for ACK/NACK and retransmissions

Asynchronous UL HARQ—ACK/NACK and retransmissions adapt to actual TxOP from LBT

…… D D D D D D D D

ACK / NACK RetransmitTransmit

… …

eCCA eCCATxOP

ACK / NACKRetransmitTransmit

S U

D D D D D D DS

SS

S

U U

U

UUUUU

U U

Flexible uplink waveform to meet spectrum requirementsMeets PSD1 limits for 5GHz unlicensed with better link budget (coverage)

LTE SC-FDM uplink—localized power

1) Power Spectrum Density (PSD) measured in power per spectrum, e.g., dBm/MHz; 2) Power concentrated in one part of the spectrum generally good for uplink coverage—but not if there is PSD limit.

RB interlaced—distributed power

………50 RBs in 10Mhz

Time

Spectrum

PSD

1

When there is PSD limit, concentrating the power in one part of spectrum may limit TX power.2

Spectrum

PSD1 limit

One UE

UE TX power

Time

Spectrum

……10

One interlace

10/20 MHz bandwidth is divided into 5/10 interlaces

……10 ……10 ……10

Spreading power over spectrum allows a higher TX power within same PSD limit.

Spectrum UE TX power

PSD

1

PSD1 limit

Enhanced discovery signals handles unlicensed operationIncreased robustness needed without a licensed anchor used by LAA/eLAA

1) Primary Synchronization Signals (PSS), Secondary Synchronization Signals (SSS), and Physical Broadcast CHannel (PBCH).

DD X X X X X … D D U U … DS

Backwards compatible — LAA / eLAA understands MulteFire signals

Slots

Sub-carriers

SSS

PSS

PB

CH

PB

CH

+

PB

CH

+

SSS+

PSS

+Repeats critical symbols1 for faster and more robust acquisition

Enables decoding with a single instance for cell edge users

Existing symbols

… DD D U US X X X X

Periodic TX opportunities

Repeated symbols

… …

Periodic TX opportunities defined to handle LBT

…………… DD X X U D S U DD DD U US X U

Periodic TX opportunities downlink

Periodic TX opportunities for pre-configured uplink

X X

DRS Window(up to 10ms)

1) Discovery Reference Signal (DRS), Random Access Channel (RACH), Radio Resource Management (RRM)

X X

DRS Window(up to 10ms)

Paging Window(up to 10ms)

UE monitors paging in a window

Defined TX windows for critical operations, e.g., DRS, RACH, RRM1

Introducing PUCCH1 for standalone operation in unlicensed spectrum

1) Discovery Reference Signal (DRS), Random Access Channel (RACH), Radio Resource Management (RRM)

Short PUCCH (sPUCCH) combined with extended PUCCH (ePUCCH

Periodic TX opportunities for pre-configured uplink

… D D D D D U US U U … D D D U US U U U U …

ACK/NACK over sPUCCH

Pending ACK/NACK, e.gdue to LBT loss

Any pending ACK/NACK over ePUCCH

TxOPeCCA eCCA

sPUCCH for small payloads in part of a

special sub-frames (S)

ePUCCH for larger payload and high user

mux capability

ACK/NACK, CSI & SR feedback for DL TX on

sPUCCH & ePUCCH

Robust mobility

• Seamless experience for various mobility modes

• Backward and forward handover supported (as Rel. 12)– Shorter interruption in case of radio link failure from forward handover

• Enhancement to radio link failure triggers to operate with contention– Detect missing DRS sub-frames as part of in-sync/out-of-sync measurements

• Enhancements for RRM measurements in async. deployments– New measurement gap configurations defined to enable measuring infrequently occurring DRS

Mobility Idle Connected

Between MulteFire nodes

Moving from MulteFire to Macro network

Moving from Macro to MulteFire

Indoor simulations resultsBaseline with 2 Wi-Fi operators in an office building, each with 4 access points

1

1) Indoor, single 20 MHz channel in 5 GHz, 80%-20% traffic split between down- and uplink, bursty traffic generated with 4 Mb files arriving with exponential inter arrival times, high traffic load with buffer occupancy at 50% in downlink and 20% in uplink for Wi-Fi only baseline, 4 APs per operator, 2 operators, office building size 120m x 50m, propagation model 3GPP indoor hotspot (InH), Wi-Fi is 802.11ac, MIMO 2x2, no MU-MIMO

Wi-Fi operator #1 Wi-Fi operator #2

120m

50m

0

1

2

3

4

Downlink

0

1

2

3

4

Uplink

Median throughput gain

Wi-Fi only baseline

0

1

2

3

4

Uplink

0

1

2

3

4

Downlink

Median throughput gain

2X gain

Wi-Fi only baseline

MulteFire offers 2X capacity gain over Wi-Fi baseline1

Wi-Fi performance preserved, sometimes better, when neighbor switch to MulteFire

1) Indoor, single 20 MHz channel in 5 GHz, 80%-20% traffic split between down- and uplink, bursty traffic generated with 4 Mb files arriving with exponential inter arrival times, high traffic load with buffer occupancy at 50% in downlink and 20% in uplink for Wi-Fi only baseline, 4 APs per operator, 2 operators, office building size 120m x 50m, propagation model 3GPP indoor hotspot (InH), Wi-Fi is 802.11ac, MIMO 2x2, no MU-MIMO

Wi-Fi operator #1 MulteFire operator

120m

50m

MulteFire by itself offers >2X capacity gain over Wi-Fi1

Higher gains in MulteFire only deployments, especially in dense scenarios

MulteFire operator #1 MulteFire operator #2

50m

120m

0

1

2

3

4

Downlink

0

1

2

3

4

Uplink

Median throughput gain

Wi-Fi only baseline

2X gain

1) Indoor, single 20 MHz channel in 5 GHz, 80%-20% traffic split between down- and uplink, bursty traffic generated with 4 Mb files arriving with exponential inter arrival times, high traffic load with buffer occupancy at 50% in downlink and 20% in uplink for Wi-Fi only baseline, 4 APs per operator, 2 operators, office building size 120m x 50m, propagation model 3GPP indoor hotspot (InH), Wi-Fi is 802.11ac, MIMO 2x2, no MU-MIMO

MulteFire offers significant capacity advantage outdoors1

Gain over Wi-Fi depends on load and traffic mix, 2X-6X in simulation scenarios

Wi-Fi

MulteFire

12

12

12

21

21

2

1

21

21

0

1

2

3

4

Uplink

0

1

2

3

4

Downlink

Median throughput gain

Wi-Fi only baseline

2X gain

1) Outdoor, single 20 MHz channel in 5 GHz, 50%-50% traffic split between down- and uplink, bursty traffic generated with 4 Mb files arriving with exponential inter arrival times, medium traffic load with buffer occupancy at 38% in downlink and 51% in uplink for Wi-Fi only baseline, dense cluster deployment, 2 operators, 4 APs each, propagation model 3GPP outdoor scenario with all APs in 50m radius, Wi-Fi is 802.11ac, MIMO 2x2, no MU-MIMO

MulteFire Summary

Based on 3GPP standards

MulteFire Technology is based on 3GPP LAA and eLAA

Similar performance & coexistence as LAA/eLAA in unlicensed

Extends eLAA—uplink & downlink—to operate without anchor in licensed spectrum

Performance advantages

Coverage: LTE like, +5-6dB link budget

Capacity: LTE link efficiency & MAC

Mobility: carrier grade, seamless

Robustness: predictable, RLF, SON

Capacity gains over Wi-Fi

2X capacity gain over Wi-Fi baseline

Higher gains when MulteFire only, especially in dense scenarios

Significant capacity advantage outdoors

MulteFire summary

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