Post on 24-Jun-2018
© Ericsson AB 2008 1
Broadband Wireless Access –HSPA and LTE
Dr Stefan ParkvallSenior Specialist, Adaptive Radio AccessEricsson Research
© Ericsson AB 2008 4
HSPA – The Global Broadband Standard
278 Operators in 93 Countries
Source: GSMA, November 2008
© Ericsson AB 2008 6
Trend – Data is overtaking Voice
4 million new HSPA subscribers per month, 56 million in total
>240 million WCDMA/HSPA subscribers world wide
High speed packet data Packet data Speech
Source: GSMA and NetQB, September 2008
Data is overtaking voice......but previs cellular systems designed primarily for voice
© Ericsson AB 2008 7
HSPA and LTE = Mobile Broadband
HSPA – High-Speed Packet Access– Evolution of 3G/WCDMA to enhance packet-data support – Gradually improved performance at a low additional cost– Data rates up to ~40 Mbit/s in 5 MHz
LTE – Long-Term Evolution– Significantly improved performance in a wide range of spectrum allocations– Data rates up to ~300 Mbit/s in 20 MHz– Takes Mobile Broadband into IMT-Advanced (”4G”)
Different systems – but many basic principles are similar!
HSPAHSPA HSPA evolutionHSPA evolutionHSDPAHSDPA
2004 2006 20082002
Studies Spec’s
LTELTE LTELTE--AdvancedAdvanced
Requirements
WCDMAWCDMA
2005 2007
© Ericsson AB 2008 8
Wireless vs Wireline
Wireless seems simple…
∇×H
∇⋅D = ρ
∇⋅B = 0
∇×E = - ∂B∂t
= J + ∂D∂t
…so what’s the problem?
© Ericsson AB 2008 9
Radio Channels and Packet Data
Radio channel quality varies...– ...distance to base station– ... random variations in the
environment
Traffic pattern varies...– ...user behavior– ...server load
Adapt to and exploit channel and traffic variations!
© Ericsson AB 2008 10
Rate Control
Reliable reception requires a certain Eb/N0
How to control Eb?– Eb = P•T
Cha
nnel
Q
ualit
y
TxP
ower
Dat
a R
ate
Power Control
Dat
a R
ate
Cha
nnel
Q
ualit
y
TxP
ower
Rate Control
Rate control more efficient than power control!
Varying instantaneous data rate acceptable for packet-data services– Rapid – tracks fast fading
© Ericsson AB 2008 11
Rate Control
Data rate controlled through...
...different channel coding rates– Advantageous channel conditions high code rate– Code rates from 1/3 to ~1
...different modulation schemes– Advantageous channel conditions higher-order modulation
...different multi-antenna schemes
QPSK 16QAM 64QAM
© Ericsson AB 2008 12
Shared-Channel Transmission
Dedicated channel– User resources assigned at ”call
setup”– Independent of instantaneous traffic
situation
Shared channel– Dynamic sharing of common
resource– Adapts to instantaneous traffic
situation
© Ericsson AB 2008 13
Channel-dependent Scheduling
Scheduling determines at each time instant…– …to whom to assign the shared channel– …which data rate to use
Basic idea: transmit at fading peaks– May lead to large variations in data rate between users– Tradeoff: fairness vs cell throughput
Cha
nnel
Qua
lity User #1
User #2
User #3
Time#1 #3 #2 #3 #1
Effective channel variations seen by the base station
© Ericsson AB 2008 14
Channel-dependent Scheduling
Round Robin (RR)– Cyclically assign the channel to users without taking channel
conditions into account– Simple but poor performance
Max C/I– Assign the channel to the user with the best channel quality– High system throughput but not fair
Proportional Fair (PF)– Assign the channel to the user with the best relative channel
quality– High throughput, fair
Rad
io L
ink
Qua
lity
Time
Rad
io L
ink
Qua
lity
Time
Rad
io L
ink
Qua
lity
Time
© Ericsson AB 2008 15
data1data2data3data4
TimeFrequency
User #1 scheduled
User #2 scheduled
1 ms
180 kHz
Time-frequency fading, user #1
Time-frequency fading, user #2
Channel-dependent Scheduling
HSPA – channel-dependent scheduling in time-domain only
LTE – channel-dependent scheduling in time and frequency domains
© Ericsson AB 2008 16
Channel Quality Indication
Scheduling and rate control adapts to channel variations
Problem: need channel knowledge at the base station
Solution: terminals transmit channel-quality reports to base station
Reporting rate configurable– HSPA – reports as often as every 2 ms– LTE – reports as often as every 1 ms
© Ericsson AB 2008 17
Hybrid ARQ with Soft Combining
Retransmsision of erroneously received packets– Fast no disturbance of TCP behavior
Soft combining of multiple transmission attempts– Soft combining improved performance
NAK
ACK
NACK
ACK
ACK
+ +
Transmitter
Receiver
P1,1 P1,2 P2,1 P2,2 P3,1
P1,1 P1,1 P2,1 P2,2 P3,1
P1,2 P2,2
© Ericsson AB 2008 18
R=3/4
redundancy version 1
Initial transmission
Transmitted bits
Bits input to decoder
Resulting code rate
Accumulated energy
Eb
CRC insertion,Turbo coding
Data
Puncturing to• generate different redundancy versions
• match the number of coded bits to the channel
redundancy version 2
R=3/8
First retransmission
2Eb
redundancy version 3
R=1/4
Second retransmission
3Eb
Hybrid ARQ with Soft Combining
Incremental redundancy
R=1/4
Third retransmission
redundancy version 1
4Eb
© Ericsson AB 2008 19
Basic Principles – Summary
Shared channel transmission
Channel-dependent scheduling
Rate control
Hybrid-ARQ with soft combining
© Ericsson AB 2008 20
Summary
Adapt to and exploit– variations in radio channel quality– variations in the traffic pattern
…instead of combating them!
Traffic pattern is time varying
Radio channel quality is time varying
© Ericsson AB 2008 22
History
NMT, ...NMT, ...Analog, speechAnalog, speech
1980 1990 2000 2010
GSM, ...GSM, ...Digital, speech and lowDigital, speech and low--rate datarate data
HighHigh--speed data speed data (up to ~20 Mbps)(up to ~20 Mbps)
WCDMA/HSPAWCDMA/HSPA
20 MHz
5 MHz
200 kHz
HighHigh--speed data speed data (up to 300 Mbps)(up to 300 Mbps)
LTELTE
30 kHz
Research and standardization
Research and standardization
Research and standardization
© Ericsson AB 2008 23
””4G4G””
3G Evolution
R99 Rel4 Rel5 Rel6 Rel7 Rel8
LTELTE
HSPAHSPAWCDMAWCDMA HSPA evolutionHSPA evolutionHSDPAHSDPA
HSPA evolution– gradually improved performance at a low additional cost
in 5MHz spectrum allocation
LTE– significantly improved performance in a wide range of spectrum allocations– further evolved into IMT-Advanced
LTE AdvancedLTE Advanced
Rel10
1999 2002 2005 2007 2008
© Ericsson AB 2008 24
PCG(Project coordination
group)
TSG GERAN(GSM EDGE
Radio Access Network)
TSG RAN(Radio Access Network)
WG2Radio Layer 2 &
Layer 3 RR
WG1Radio Layer 1
WG3Iub, Iuc, Iur &
UTRAN GSM Req.
WG4Radio Performance& Protocol Aspects.
WG2Protocol aspects
WG1Radio Aspects
WG3Terminal testing
TSG SA(Services &
System Aspects)
WG2Architecture
WG1Services
WG3Security
WG4Codec
TSG CT(Core Network &
Terminals)
WG3Interworking withExternal Networks
WG1MM/CC/SM (Iu)
WG4MAP/GTP/BCH/SS
WG5OSA
Open Services Access
WG5Mobile Terminal
Conformance Test
WG5Telecom
Management
WG6Smart Card
Application Aspects
3GPP
International organization– Vendors and operators co-operate– Develop specifications for GSM, WCDMA/HSPA, LTE
© Ericsson AB 2008 25
Standardization – a Flying Circus?
RAN1 meetings held ~8 times a year– Meetings run from Monday to Friday– Held in various countries in Europe, North America, and Asia
Meeting schedule 2007– January 15-19, Sorrento, Italy– February 12-16, St Louis, USA– March 26-30, St Juliens, Malta– April 17-20, Beijing, China– May 7-11, Kobe, Japan– June 25-29, Orlando, USA– August 20-24, Athens, Greece– October 8-12, Shanghai China– November 5-9, Seoul Korea
© Ericsson AB 2008 26
Typical RAN1 Meeting
Approx 200 delegates attending and ~550 documents submitted...Number of Contributions per Agenda Item
0
20
40
60
80
100
120
Appr
oval
of t
he a
gend
a
Appr
oval
of t
he m
inut
es fr
om p
revi
ous
mee
tings
Liai
son
stat
emen
t han
dlin
g
Mai
nten
ance
of R
elea
se 9
9 –
Rel
ease
7
Evol
ved
UTR
A an
d U
TRAN
TDD
Fra
me
Stru
ctur
e
Fina
lizat
ion
of T
S 36
.211
Dow
nlin
k re
fere
nce
sign
als
Upl
ink
refe
renc
e si
gnal
s
Dow
nlin
k C
ontro
l Sig
nallin
g
Upl
ink
Con
trol S
igna
lling
Map
ping
of v
irtua
l res
ourc
e bl
ocks
to p
hysi
cal r
esou
rce
bloc
ks
Bit s
cram
blin
g se
quen
ces
for U
L/D
L tra
nsm
issi
ons
RAC
H
Fina
lizat
ion
of T
S 36
.212
Fina
lizat
ion
of T
S 36
.213
Tim
ing
sync
hron
izat
ion
UL/
DL
Pow
er C
ontro
l
Inte
r-ce
ll Int
erfe
renc
e C
oord
inat
ion
RAC
H ti
min
g an
d pr
eam
ble
sequ
ence
sel
ectio
n
UE
Proc
edur
es fo
r dow
nlin
k sh
ared
cha
nnel
UE
Proc
edur
es fo
r upl
ink
shar
ed c
hann
el
Fina
lizat
ion
of T
S 36
.214
Fina
lizat
ion
of T
S 36
.201
UE
Cat
egor
ies
Com
bina
tion
of H
ighe
r Ord
er M
odul
atio
n an
d M
IMO
in H
SDPA
(FD
D)
Enha
nced
Upl
ink
for C
ell_
FAC
H S
tate
in F
DD
Stud
y Ite
m o
n Sy
nchr
oniz
ed E
-DC
H