futureworks looking ahead to 5g - ieee...
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27/05/2014 1 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks
looking ahead to 5G Building a virtual zero latency
gigabit experience
Preben Mogensen, Kari Pajukoski*, Esa Tiirola*, Jaakko Vihriälä*, Eeva Lähetkangas*, Frank
Frederiksen*, Gilberto Berardinelli, Fernando M. L. Tavares, Nurul H. Mahmood, Mads Lauridsen, Davide
Catania, Martha Sarret, Andrea F. Cattoni, Petar Popovski, Dereje Wassie, Oscar Tonelli, Farhood
Hakhamaneshi
27/05/2014 2 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks
Capacity
Latency
Energy consumption
Cost
User data rates
Coverage
Stretching performance targets for 5G
x more traffic
By 2030
Low energy
M2M ultra low cost
millisecond
latency
Mbit/s wherever needed
years M2M
battery life Gbit/s peak data rates
x more devices
Ultra reliabilit
y
2020+
27/05/2014 3 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks How to increase Network Capacity towards 5G?
5G will be a HetNet configuration, where each layer will see different factors
Spectral Efficiency
Amount of Spectrum
Number of
Base Stations Capacity
HSPA+
LTE
WiFi
TD-LTE
LTEFemto
HSPA+Femto
Macro
Small Small
UDS
UDS
UDS
Spectral
efficiency Spectrum
Base
Stations Capacity
x x
Ultra dense small
cells
Small cells
Macro cells
+
+
TOTAL Size of boxes only indicative
27/05/2014 4 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks New Spectrum - for 5G ultra dense small cells
Carrier Frequency
Single Antennas
(or low efficiency)
Multi Antenna
Technology
(High Rank)
Multi (massive)
Antenna Technology
(Low Rank)
LOS/NLOS LOS (single reflection)
5G must be flexible in supporting new spectrum:
(cell range, carrier frequency, system bandwidth and antenna technologies)
?
dm-waves cm-waves mm-waves
3GHz 30GHz
mm-wave
5G RAT cm-wave
5G RAT Current IMT
RAT’s
Basic Link budget / Cell size
Spectrum
Availability
300GHz
27/05/2014 5 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks How to Increase Spectral Efficiency for Ultra Dense Small cells?
Multi Antenna Systems and advanced receivers: • Commercial evolution of multi antenna technology has gone slow in past but ease with higher carrier frequency
• Receivers with interference rejection/cancelation capability has great potential but increase base band processing complexity
Interference coordination
• Minor or no gain in average
• Large Improvement in outage
Single link optimization
• Single link capacity is already close to Shannon:
• Fast adaptive modulation and coding
• Hybrid ARQ
Claude Elwood Shannon (1916–2001)
Small potential Medium potential Large potential
27/05/2014 6 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks
• 5G will only become a success, if we choose the right technology for the right
time and purpose.
From H2020 vision to 5G realistic targets
Performance Optimized Cost and Energy Optimized
?
27/05/2014 7 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks 5G cm-wave RAT optimized for ultra dense small cells
cmWave design targets
Less than 1ms latency
Flexible operation in unpaired bands
Self-optimized APs
”Always on” w/o battery draining
Multi-hop, D2D & self-backhaul
10 Gpbs peak data rate
Simplicity & cost-effectiveness
Native location services support
High rank MIMO
Interference suppression
OFDM modulation
Optimized frame structure
Interference coordination
Dynamic TDD
Distributed synchronization
Scalable carrier bandwidth
Design solutions
“Always ON”, low overhead
Flexible support of
UL/DL traffic patterns D2D
Multi-hop
Self- backhauling
Low cost
Low power consumption
Location information
Internet cloud
27/05/2014 8 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks Duplexing - for 5G ultra dense small cells
• Flexible spectrum assignment
• Ease of spectrum sharing
• Flexible UL/DL duplexing
• Simple RF ->Low cost
• Low power consumption
• Channel reciprocity
• Ease of support: normal access, self-backhauling and D2D
• TDD is an attractive duplexing scheme for 5G
ultra dense small cells
Internet Clod
27/05/2014 9 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks
• Higher data rates requirements shorter
latency to reduce cost of baseband (especially
buffering)
5G: Higher Carrier bandwidth and shorter TTI
Fractional cost breakdown relative to baseband for
reference FDD/LTE modem [R1-120925]
Receiver data processing
HARQ buffer
Post FFT buffering
ADC/DAC (DFE)
Sync. Cell search
Turbo Decoding
MIMO specific processing
UL Tx Processing
FFT/IFFT
Receiver control processing
TTI length
3G
4G
LTE
5G
Carrier
Bandwidth
• Multi-Gbps data rates and milliseconds latency
27/05/2014 10 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks Are there quantum leaps in Waveforms?
OFDM, FBMC, FTN
Heisenberg tells us:
Whatever we gain in one domain, we are doomed to lose in the other:
• OFDM is localized well in time but not well localized in frequency
• And vice versa with FBMC or other frequency optimized modulations
There are various options to trade
time vs. frequency confinement, but
there is no free lunch
Low latency requirements & low complexity high rank MIMO
seems to favor OFDM also for 5G
27/05/2014 11 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks
.
0 10 20 30 40 50-80
-70
-60
-50
-40
-30
-20
-10
0
10
Bandwidth [MHz]
Po
we
r [d
B]
DFT-s-OFDM
zero-tail DFT-s-OFDM
Zero Tail: Create an OFDM symbol having a number
of zeros at its termination.
Zero-tail DFT-S-OFDM as flexible waveform for 5G
Advantages:
• Allows to use link specific “Zero” length
• Better spectral containment compared to DFT-S-OFDMA or OFDMA
• Lower PAR compared to OFDMA
• Can be applied to take care of Guard Period
• Can be applied for D2D communication in order to mitigate asynchronous inband interference between D2D and cellular communications
• Can fully coexist with CP-OFDMA
One merit of OFDM is flexibility for diversity use cases: SC-FDM, as well as zero-tail DFT-S-OFDM can
be obtained as straightforward add-on over basic OFDM.
dataDFT
zeros
0
IFFTSub-
carrier
mapping
0 0
CP
27/05/2014 12 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks
Support for advanced receivers
Flexible UL/DL, D2D and self- backhauling
Energy-effective pipeline processing
Frequency coordination and reuse
Control channel located before data
5G Optimized frame structure for Ultra Dense Small Cells Flexibility, lower latency and higher throughput
DMRS = Demodulation Reference Signal; GP = DMRS = Demodulation Reference Signal; GP = Guard Period
Stabilized covariance matrix of interferers
Control plane localized in time & frequency
DL and UL have same PHY (control, data, RS)
Fre
quency
Time
Control Data (entirely DL or entirely UL)
GP OFDM symbol GP
DL UL DMRS
0,25ms
GP
27/05/2014 13 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks Advanced Receivers for MIMO
to overcome the interference problem
MRC Maximum Ratio Combining
Inter-cell interference unaware MIMO linear receiver
IRC+SIC
Interference Rejection Combining
Interference aware MIMO linear receiver
IRC + Successive Interference Cancellation
Non-linear MIMO receiver that cancels inter-stream interference
IRC
27/05/2014 14 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks MIMO and Advanced Receivers
Further performance improvement using IRC+SIC C
DF
(%
)
0 1000 2000 3000 4000 5000 60000
10
20
30
40
50
60
70
80
90
100
Average Cell Throughput [Mbps]
CD
F [
%]
MRC
IRC
IRC+SIC
0 1000 2000 3000 4000 5000 60000
10
20
30
40
50
60
70
80
90
100
Average Cell Throughput [Mbps]
CD
F [
%]
IRC - Reuse 1
IRC+SIC - Reuse 1
IRC - Reuse 2
IRC+SIC - Reuse 2
4x4, reuse 1 4x4, reuse 1 & 2
27/05/2014 15 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks 5G: MIMO and Advanced Receivers
System design requirements
OFDM symbol-level network synchronization
IRC
Identical uplink and downlink frame formats
Orthogonal reference symbols for interference estimation
Interference stabilization during the frame
Interference-aware rank adaptation
Independent MCS block coding per layer
SIC-aware link adaptation
IRC+SIC
Interference-aware rank adaptation
SIC-aware link adaptation
27/05/2014 16 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks Rank adaptation – dynamic selection of the number of MIMO streams
Challenges Solutions
Estimating expected
throughput in fast changing
interference conditions
Efficient and novel post-IRC
SINR estimation method that
does not require instant CSI
Maximizing own throughput is
selfish:
→ Increases interference
→ Reduces DoF for IRC
Victim-awareness (VA) through
cooperation:
→ Altruistic rank selection
→ Improved network SE
Instant
CSI Victim-Aware Non VA
Yes → Optimum performance
→ Practically impossible
→ Difficult in practice with
flexible UL/DL
→ Poor performance
No
→ Proposed algorithm
→ Close to optimum perf.
at lower complexity
→ Uses post-IRC SINR
estimation method
→ Similar performance to
instant CSI
Rank adaptation trade-off
More streams:
↑ Own throughput
↑ Interference
↓ IRC DoF
Less streams:
↓ Own throughput
↓ Interference
↑ IRC DoF
0 5 10 15 200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Spectral Efficiency (bps/Hz)C
DF
Four cells, 100% deployment ratio
Optimum
Proposed VA
Proposed non-VA
Instant CSI, non-VA
Fixed Rank (1)
Fixed Rank (2)
Fixed Rank (3)
25%
27/05/2014 17 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks Concept emulation: 5G performance with ultra dense small cells
Fixed TDD pattern -50%
Fixed TDD pattern
Latency
+30%
Throughput
UL/DL switching
Interference suppression
Interference coordination
Fast dynamic UL/DL switching for optimal
resource utilization
Multi-antenna technology, advanced receivers, and rank
adaptation
Self-organized fractional reuse for
interference avoidance
Dynamic UL/DL switching
Dynamic UL/DL
switching
27/05/2014 18 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks Dynamic UL/DL switching cause Interference variability Time trace for a single UE, full buffer
Assuming perfect reporting
Evaluating the difference between SINR at time of reporting and
SINR at time of scheduling
Fixed 1:1
UL/DL
Random
50 100 150 200 250 300 350 400 450 5008
10
12
14
16
18
20
22Random pattern
SIN
R
time
50 100 150 200 250 300 350 400 450 5008
10
12
14
16
18
20
22Fixed pattern
SIN
R
time
27/05/2014 19 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks Can we overcome the interference variability from dynamic UL/DL? H-ARQ, OLA, Low Rank….
Lost
capacity HA
RQ
Lost packet We monitor the SINR (CQI) at
time of reporting and the SINR
when scheduled and compute the
difference.
Negative values means lost
capacity potential
Positive values means packet
error.
27/05/2014 20 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks The ”beast” of RRM for 5G is becoming complicated
RRM
buffer size
delay
QoS
data
ACK-NACK
CQI
CSI
radio
Users
direction
H-ARQ
MCS
RANK
PMI
Frequency
allocation
out
User selection
Link adaptation+
OLA
H-ARQ
Link direction
Interference Coordination
Rank adaptation
27/05/2014 21 © Nokia 2014 - Looking ahead to 5G
For internal use
FutureWorks 4 Cell Testbed Demo @ Aalborg University
Based on USRP N200 hardware
by Ettus Research and ASGARD
software platform
1 2
3 4
2x2 MIMO, RANK 1