understanding multefire’s radio link · pdf filemeets psd1 limits for 5ghz unlicensed...
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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
Thank youThank YouFor more information, visit us at www.multefire.org
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