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qualtaghblurtingMobile - Wireless

Dec 12, 2013 (3 years and 11 months ago)

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Aida Botonjić

Tieto

1

WCDMA/HSPA

Aida Botonji
ć

Aida Botonjić

Tieto

2

1990

2000

1
st

generation

Analogue speech


NMT, AMPS, TACS

2
nd

generation

Digital speech +

low
-
rate data (<64 kbps)


GSM, PDC, IS
-
95,

IS
-
136 (D
-
AMPS
)


Multimedia services

(<2 Mbps)

+ 2nd gen. services

3
rd

generation


UMTS/IMT
-
2000

1980

Background

LTE

2010

Faster

Multimedia services

(30
-
100Mpbs)

+ 3rd gen. services

4
th

generation

LTE

Aida Botonjić

Tieto

3

3GPP releases


R99: WCDMA Evolved


R5: HSDPA


High Speed Downlink Packet Access


R6: HSUPA


Enhanced Uplink



LTE


Long
-
Term Evolution

Enhanced Uplink

(HSUPA)

MIMO

CPC

Enhanced Downlink

(HSDPA)

Rel 4

Rel 5

Rel 6

HSPA

WCDMA

R99

Rel 7

Rel 8

HSPA Evolution

LTE

= Third Generation Partnership Project

Aida Botonjić

Tieto

4

Why WCDMA/HSPA?


Applications:


E
-
mail


Video telephony


Web browsing


Content sharing, e.g. Picture/video upload.




Devices (UE):


Broadband modem


Mobile phones with


Large color screen


Gbyte memories


HSPA Targets:


Adapt to fast variations in radio conditions


Reduced delays


Improved High
-
Bitrate Availability


Improved Capacity


Aida Botonjić

Tieto

5


WCDMA network architecture

Node B

Node B

RNC

RNC

dedicated

channels

Iur

Iub

Iu

Core network

(Internet, PSTN)

UE

Aida Botonjić

Tieto

6

Frame structure


#0

#1

#2

#3

#14

One slot, 2/3ms

One radio frame,

10 ms

#13

One subframe, 2ms

Time slot is the shortest repetitive period


Radio frame is the shortest transmission duration

Aida Botonjić

Tieto

7

HSDPA Basic Principles

Shared Channel Transmission

Dynamically shared in time & code
domain

Higher
-
order Modulation

16QAM in complement to QPSK for
higher peak bit rates

2 ms

Short TTI (2 ms)

Reduced latency

Fast Hybrid ARQ with
Soft Combining

Reduced round trip delay

Fast Radio Channel
Dependent Scheduling

Scheduling of users on 2 ms time
basis

Fast Link Adaptation

Data rate adapted to radio
conditions on 2 ms time basis

t

P

Dynamic Power Allocation

Efficient power &

spectrum utilisation

= HS
-
DSCH

Aida Botonjić

Tieto

8

HSUPA Basic Principles


Fast Retransmissions


Roundtrip time ~2 ms possible


Soft combination of multiple attempts


Fast Radio
-
Dependent Scheduling


2 ms time basis

2 ms


Short TTI (2 ms)


Reduced latency

= E
-
DCH

Aida Botonjić

Tieto

9


Shared Channel
Transmission


A set of radio resources dynamically shared among multiple
users, in time and code domain


Efficient code utilization


Efficient power utilization


Channelization codes allocated

for HS
-
DSCH transmission

8 codes
(example)

SF=16

SF=8

SF=4

SF=2

SF=1

TTI

User #1

User #2

User #3

User #4

Shared
channelization
codes

time

Aida Botonjić

Tieto

10

Fast Channel
-
dependent
Scheduling


Scheduling = which UE to transmit to at a given time instant and at
what rate



Basic idea: transmit at fading peaks


May lead to large variations in data rate between users


Tradeoff: fairness vs cell throughput

high data rate

low data rate

Time

#2

#1

#2

#2

#1

#1

#1

Scheduled
user

User 1

User 2

TTI

Aida Botonjić

Tieto

11

Fast Link

Adaptation


Adjust transmission parameters to match
instantaneous channel conditions




HS
-
DSCH: Rate control (constant power)


Adaptive coding


Adaptive modulation (QPSK or 16QAM)


Adapt on 2 ms TTI basis


fast



Release 99: Power control (constant rate)

C h a n n e l
4
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
C h a n n e l
4
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
Good channel

conditions



less power

Bad channel

conditions



more power

power control

(HSUPA E
-
DCH)

C h a n n e l
4
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
C h a n n e l
4
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
s a k d j f l ö l a d k s f j
a s l d f ö a d ö l k d
q w e r r t i u o d k l c .
Good channel

conditions



h楧i⁤慴愠a慴a

䉡搠捨慮a敬

捯cd楴楯is



汯l d慴愠a慴a

rate adaptation
(HSDPA HS
-
DSCH)

Aida Botonjić

Tieto

12

Higher Order

Modulation


16QAM may be used as a complement to QPSK


16QAM allows for twice the peak data rate compared to QPSK

16QAM

2 bits/symbol

4 bits/symbol

QPSK

Release 99: only QPSK

Aida Botonjić

Tieto

13

Short 2 ms TTI


Reduced air
-
interface delay


Improved end
-
user performance



Necessary to benefit from other HS
-
DSCH features


Fast Link Adaptation


Fast hybrid ARQ with soft combining


Fast Channel
-
dependent Scheduling

10 ms

20 ms

40 ms

80 ms

Earlier releases

2 ms

Rel 5

2 ms

Aida Botonjić

Tieto

14

ACK

TO RNC

Transmitter

Receiver

Rapid retransmissions of erroneous data



Hybrid ARQ protocol terminated in Node B




short RTT (typical example: 2 ms)



Soft combining in UE of multiple transmission
attempts




reduced error rates for retransmissions

Fast Hybrid ARQ with Soft
Combining

Aida Botonjić

Tieto

15

NACK

TO RNC

ACK

Transmitter

Receiver

Fast Hybrid ARQ with Soft
Combining

Rapid retransmissions of erroneous data



Hybrid ARQ protocol terminated in Node B




short RTT (typical example: 2 ms)



Soft combining in UE of multiple transmission
attempts




reduced error rates for retransmissions

Aida Botonjić

Tieto

16

Dynamic Power

allocation

Dedicated channels (power controlled)

Common channels

Power usage with dedicated channels
channels

t

Unused power

Power

Total cell power

3GPP Release 99



3GPP Release 5

t

P

Downlink channel with dynamic power allocation

t

Total cell power

Power

Dedicated channels (power controlled)

Common channels

HS
-
DSCH (rate controlled)

Aida Botonjić

Tieto

17

Conclusion

Rel 99

HSPA (Rel 5 & 6)

Channel transmission
in time
domain

Channel transmission
in time and
space domain

Scheduling

Channel dependent scheduling

QPSK modulation

QPSK and 16 QAM modulation

TTI
min
= 10ms

TTI
min
= 2ms

ARQ

HARQ

Static power allocation

Dynamic power allocation


-

Link adaptation