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Radio systems, LTH2007-03-01 1
3G and Beyond: HSPA Evolution and LTE
Fredrik Florén
(?)
2007-03-01 Radio systems, LTH 2
Overview
• What is the 3GPP?
• 3GPP Timeline
• HSPA Evolution
– Receive Diversity and Equalizers
– HSDPA/HSUPA
– MIMO for HSDPA
– Higher-Order Modulation
– Continuous Packet Connectivity
• LTE
– Targets
– Technology
– Deployment?
• Summary
2007-03-01 Radio systems, LTH 3
What is the 3GPP?
• The 3rd Generation Partnership Program is a collaboration of a number of national/regional standardization bodies
– ARIB (Japan)
– CCSA (China)
– ETSI (Europe)
– ATIS (USA)
– TTA (Korea)
– TTC (Japan)
• The 3GPP maintains and evolves
– GSM (GPRS, EDGE, GERAN Evolution)
– WCDMA
– LTE
– and their corresponding core networks
2007-03-01 Radio systems, LTH 4
3GPP Timeline
• New versions of 3GPP standards are called releases
• Below only the main physical layer features are shown
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Release ’99
3G
Release 4
Release 5
HSDPA
Release 6
HSUPA
Rx Div., Equaliz.
Release 7
MIMO
CPC
HoM
Rx Div. + Equaliz.
Release 8
LTE
MIMO+64QAM?
2007-03-01 Radio systems, LTH 5
High Speed Packet Access Evolution
2007-03-01 Radio systems, LTH 6
HSDPA
• High Speed Downlink Packet Access
– Adaptive modulation and coding
– Node-B scheduling
– Short transmission time interval
– Fast Hybrid ARQ
– No power control
– 16-QAM
– Peak rate: 14.4 Mbps
L1 retrans-
missions
Higher-
layer
trans-
mission
Rel ‘99 HSDPAt
SNR
R3
R2
R1
2007-03-01 Radio systems, LTH 7
HSUPA
• High Speed Uplink Packet Access
– Fast Node-B uplink scheduling
– Fast Hybrid ARQ
– Optional short transmission time interval
– Long TTI needed for coverage
– Adaptive spreading factor
– Power control and soft handover retained
– Peak rate: 5.76 Mbps
Scheduling
HARQ
Power control
Reordering
2007-03-01 Radio systems, LTH 8
Receive Diversity and Equalizers
• Performance requirements defined for
– Two-antenna receive diversity (Type 1)
– Equalizer (Type 2)
– LMMSE chip-level
– GRake
– Receive diversity + equalizer (Type 3)
Receive diversity works
well in whole cellEqualizer only works well close to Node-B
t
h(t)
h(t)
h(t) g(t)
h(t)*g(t)
Tx Rx
Tx Rx
ISI
Intra-cell int.
2007-03-01 Radio systems, LTH 9
MIMO for HSDPA
• Extension of the existing beamforming mode
• Dual-Stream Transmit Antenna Array (D-TxAA)
• Doubles peak rate to 28 Mbps
• For micro cell, 3 km/h, and 50% power to HSDPA (ref: 1x2 LMMSE)
– 20% gain in cell capacity
– 35%-50% gain in peak user throughput
– Non-linear receivers shown to give additional gain
De-
mux
EncodeChannel
Interlv
Modulator:
QPSK
16-QAM
…
EncodeChannel
Interlv
Modulator:
QPSK
16-QAM
…
v11
v21
v12
v22
To spreading
and first
antenna
To spreading
and second
antenna
High-rate
data stream
• Complexity
– Approximately 100% - 170% for 2x2 LMMSE compared to 1x2 LMMSE
– Non-linear receivers (SIC) require re-encoding
• Sectorization?
• Is it worth it?
2007-03-01 Radio systems, LTH 10
Higher-Order Modulation
• HSDPA
– 16 QAM => 64 QAM
– Peak rate: 14.4 Mbps => 21.6 Mbps
– Simulations show ~15% peak user throughput gain
– In Release 8: MIMO + 64 QAM
– Peak rate: 43.2 Mbps
• HSUPA
– QPSK => 16 QAM
– Peak rate: 11.52 Mbps
• 64-QAM requires good accuracy when modulating
• Similarly to MIMO, good channels needed
• Marketing figures?
2007-03-01 Radio systems, LTH 11
Continuous Packet Connectivity
• Bursty traffic is common
• Large delays occur when switching between active and idle mode
• In active mode, control channels required
• High control channel overhead for small packets, e.g., VoIP
• Goal
– Increase number of users in active mode
– Increase time spent in active mode
– Increase battery time
• Solution
– New control channel formats requiring less transmit power
– Discontinuous transmission and reception of control channels at UE
HS-SCCH,
F-DPCH
DPCCH,
CQI
2007-03-01 Radio systems, LTH 12
Long Term Evolution
2007-03-01 Radio systems, LTH 13
LTE High-Level Requirements [1]
• Ensure competitiveness in long-term, 10 years and beyond
• Low-latency
• High data rate
• Packet optimized
• Flexibe bandwidth support
• Possibility to use both existing and new frequency bands
• Reduced production cost
• Simplified architecture
• Reasonable system and terminal complexity, cost, and power consumption
• Optimized for low mobile speed but also support high mobile speed
– Optimized: 0-15 km/h
– High performance: 15-120 km/h
• Focus on cell radii up to 5 km[1] 3GPP TR 25.913, “Requirements for Evolved UTRA (E-UTRA)
and Evolved UTRAN (E-UTRAN)”
2007-03-01 Radio systems, LTH 14
LTE Detailed Requirements
• Peak data rates (UE has 2 RX and 1 TX
antenna(s) )
– downlink: 100 Mbps
– uplink: 50 Mbps
• Spectrum allocations: 1.25 MHz, 1.6
MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz
and 20 MHz
• FDD (also half duplex) and TDD
t
f
t
f
t
f
f
2007-03-01 Radio systems, LTH 15
Downlink
• Orthogonal Frequency Division Multiplexing (OFDM)
– Parallel Low-Rate Carriers (Sub-Carriers)
– Cyclic prefix
– Ensures orthogonality
– Avoids ISI
– OFDM efficiently realized with FFT
OFDM symbol
CP
IDF
T
P/S CP Channel CPD/AA/D
S/P
DF
T
Inpu
t D
ata
Sym
bols
Outp
ut D
ata
Sym
bols
2007-03-01 Radio systems, LTH 16
Downlink, cont’d
• Three modes
– Short CP (4.7 us), 15 kHz subcarrier spacing
– Long CP (16.7 us), 15 kHz subcarrier spacing
– Very long CP (33 us), 7.5 kHz subcarrier spacing
• Small subcarrier spacing
– Long symbol => Channel changes
• Large subcarrier spacing
– Short symbol => Large overhead
2007-03-01 Radio systems, LTH 17
• Time-frequency interpretation
• Subframe is delay-overhead trade-
off
• Reference signals
– MIMO
• Control channels
– Resource indication
– Transport format
– HARQ info
– Uplink grant
– Uplink ACK/NACK
• Synchronization & Broadcastsubframe = 1 ms
t
f
Downlink, cont’d
Control
Pilot
Data for
user #1
Data for
user #2
2007-03-01 Radio systems, LTH 18
Downlink, cont’d
• Turbo decoding
– Contention-free quadratic polynomial
permutation (QPP) turbo code
internal interleaver
• HARQ
• Adaptive modulation
– QPSK, 16-QAM, 64-QAM
• Scheduler
Transport block (L2 PDU)
CRC attachment
Channel coding
HARQ functionality
including adaptive coding rate
Physical channel segmentation
(resource block mapping)
Adaptive modulation(common modulation is selected)
To assigned resource blocks
Number of assigned resource blocks
Resource
Block
Subframe
1 ms
180 kHz
2007-03-01 Radio systems, LTH 19
MBMS
• Multimedia Broadcast Multicast Service
– Provides multimedia content to a number of subscribers
– Audio
– Video
– Stock quotes
– Etc…
• Same content in many cells
tt
t
• OFDM offers soft combining
– Transparent to UE
– Synchronization
• Greatly improves MBMS cell-edge
performance
• Multiplexing of unicast/MBMS
2007-03-01 Radio systems, LTH 20
Uplink
• Single-Carrier Frequency Division Multiplexing (SC-FDMA)
– Low Peak to Average Power Ratio (PAPR)
– “Easy” to equalize channel due to CP
– Time-domain generation:
– Frequency-domain generation (DFT-Spread OFDM):
CPInput Data
SymbolsPulse
Shaping f
Input Data
Symbols
DFT
Mapping IFFT CP
DFT
User 1
User 2
Pulse
Shaping f
2007-03-01 Radio systems, LTH 21
Uplink, cont’d
• CP: 4.7 us and 16.7 us
• Orthogonal multiple access
• Shared channel
• Time and frequency alignment
• Random access
t
f
subframe = 1 ms
• Data/Control multiplexing
• Slow power control
• Sounding pilot will also be needed
• QPSK, 16-QAM, 64-QAM (optional)
Data & control
User #1
Data & control
User #2
Control for users
not transmitting
data (CDM)
Pilots
2007-03-01 Radio systems, LTH 22
MIMO
• Downlink
– Two or four transmit antennas and two or four receive antennas
– Spatial Multiplexing (SM)
– Up to four streams
– Codebook-based pre-coding
– Transmit Diversity (CDD/SFBC)
– Multiuser MIMO also supported
• Uplink
– Only multiuser MIMO supported
– Closed-loop transmit antenna selection (optional)
• Scheduler will be busy…
TX RX
TX/RX
TX/RX
TX/RX
Single-user MIMO
Multi-user MIMO
2007-03-01 Radio systems, LTH 23
Interference Coordination
• Reuse one will work, but…
• Some claim interference coordination will be needed
– Fractional reuse
– Partial reuse
– Inverted reuse
– “Conventional” reuse
• Adaptive?
• Cancellation?
• Scheduler will be busy…
PSD
fF1 F2 F3
PSD
f
F1 F2 F3Fr
2007-03-01 Radio systems, LTH 24
Persistent Scheduling
• LTE is packet switched
• How support VoIP?
• “Persistent scheduling”
– Statically allocate resources in pre-determined pattern
– Fixed delay
– No control overhead
– Fixed modulation and coding
Transmission instants according to persistent scheduling pattern
Transmission according to SCCH schedulingData
SCCH overhead
Data
SCCH overhead
time
fre
qu
ency
Transmission instants according to persistent scheduling pattern
Transmission according to SCCH schedulingData
SCCH overhead
Data
SCCH overhead
time
fre
qu
ency
• Circuit switched to packet switched to cirucuit switched?
• Circuit switched has its merits
• Scheduler will be busy…
2007-03-01 Radio systems, LTH 25
LTE Detailed Requirements, cont’d
• Delay: <5 ms
• Throughputs (ref: Rel-6, Type 1)
– Downlink
– Mean user throughput: 3-4x
– Cell-edge througput: 2-3x
– Cell capacity: 3-4x
– Uplink
– User throughput: 2-3x
– Cell-edge throughput 2-3x
– Cell capacity: 2-3x
• Targets fulfilled?
– Fair comparison?
TX RX
Base Mobile
Rake
TXRX
3G/HSPA
RX
TXRX
LTE
TX
2007-03-01 Radio systems, LTH 26
LTE Deployment
• Is a do-it-all, low-complexity system realistic?
• Applications
– Sit & work
– Stroll & surf
– Ride & surf
– Walk & talk
• Other radio accesses
– WLAN
– GSM/EDGE/GERAN Evolution
– 3G/HSPA
– DVB-h
– WiMAX
• Services requiring high bitrates in mobile systems?
– Terminals!
• How much are customers willing to pay?
– Flat rate
2007-03-01 Radio systems, LTH 27
LTE Deployment, cont’d
• Few 3G/HSPA vendors
• Large interest in LTE among vendors
• Not all operators have investmented in 3G/HSPA
• LTE possibly suitable replacement/complement for
– 3G/HSPA
– GSM
• Simpler and cheaper
– Multi-mode terminals easier?
• Flexible spectrum allocation
• Migration paths
• Timing
– Typically 5 years stable core spec to prototype, another 2 years to certified mass market
– Terminal availability?
• Prioritization needed
• Core (SAE) and radio access network architecture must not be forgotten
2007-03-01 Radio systems, LTH 28
Summary
• HSPA Evolution
– Enhancement of packet-data services
– MIMO
– Higher-order modulation
• LTE
– High peak data rates
– Low latency
– Flexible bandwidth operation
– OFDM-based
– MIMO
Radio systems, LTH2007-03-01 29