Performance Analysis of
Transport Format Combination
Selection in WCDMA Enhanced
Uplink
Author: Teemu Björninen
Supervisor: Professor Sven-Gustav Häggman
Instructor: D.Sc. (Tech.) Shyam Chakraborty
Contents
 Basics of WCDMA Enhanced Uplink
 What is E-TFC
 Research question and methods
 Results and conclusions
© Ericsson AB 2006
Teemu Björninen
2006-01-31
Basics of WCDMA Enhanced Uplink
 Enhanced Uplink aka HSUPA
 Enhanced Uplink is standardized in 3GPP Release 6
 Enhancement to packet access domain
– Reduces round trip time
– Provides higher data rates, up to 5.76 Mbps
 Enhanced Uplink is invisible for Rel 99 network
components, separate channelisation code sets
 Enabler for new services and success of 3G, together
with HSDPA?
© Ericsson AB 2006
Teemu Björninen
2006-01-31
Basics of WCDMA Enhanced Uplink

Changes to Rel 99 uplink
© Ericsson AB 2006
–
Shorter transmission time interval, 2 or 10 ms
–
Packet scheduling is moved from RNC to Node B enabling faster
response to varying radio conditions and user bit rate requests.
–
Hybrid Automatic Repeat Request (HARQ) retransmission is used
before RLC retransmissions. Up to eight parallel processes with
soft combining.
–
New dedicated transport channel called Enhanced Dedicated
Channel (E-DCH), TX power is an offset to DPCCH
–
New control channel, TX power is an offset to DPCCH
Teemu Björninen
2006-01-31
Basics of WCDMA Enhanced Uplink

New protocols to MAC-layer
1. MAC-es
 Terminated in RNC
 For insequency delivery and duplicate detection
2. MAC-e
 Terminated in Node B
 Controls HARQ and scheduling
© Ericsson AB 2006
Teemu Björninen
2006-01-31
What is E-TFC

E-TFC, Enhanced Uplink Transport Format Combination

E-TFC determines how much data can be send during one transmission
time interval

TFC selection for Rel 99 dedicated channels is done prior to E-TFC
selection

UE builds up an E-TFC restriction list
–
–
–
© Ericsson AB 2006
Based on bit rate limitation, which comes from Node B scheduler in the
form of absolute or relative grant
Based on transmission power resources.
Selects ”the best” E-TFC from the restriction list, which maximises data
throughput
Teemu Björninen
2006-01-31
What is E-TFC
 E-TFC contains
only one transport
block
 Mac-level headers
are 6 bits long
Tsn = Transmission sequence number
DDI = Data discription indicator
© Ericsson AB 2006
Teemu Björninen
2006-01-31
Research Question
 Study the performance of Enhanced Uplink E-TFC
selection in a single cell network, without mobility
 Study the impact of power reduction algortihm in ETFC selection on selected performance indicators
when Ue exceeds maximum transmission power
© Ericsson AB 2006
Teemu Björninen
2006-01-31
Research Methods

Computer simulations with Ericsson’s Rasmus WCDMA simulator

Simulation results of the implemented power reduction algorithm in
E-TFC selection is compared to a simpler non standardized
algorithm and to the theoretical calculations

New implementation: calculates the needed reduction, reduces TX
power back to allowed level (Algorithm 2)

Simple implementation: when max TX power is exceeded, TX
power is multiplied by 0,5 (Algorithm 1)

Three measured indicators: system throughput, user throughput
and maximum allowed E-TFC per transmission time interval
© Ericsson AB 2006
Teemu Björninen
2006-01-31
Results, Theoretic Approach
 What is possible to achieve?
 Parameter values and used scheduler determines the
limits, max rate is set to 1800 kbps
1600
User throughput [kbps]
System throughput [kbps]
1800
1400
1200
1000
800
600
400
200
0
0
1
2
3
4
5
6
7
8
Users in the cell
© Ericsson AB 2006
Teemu Björninen
9
10 11 12
2000
1800
1600
1400
1200
1000
800
600
400
200
0
Provided by
scheduler
Theoretical maximum
0
1
2
3
4
5
6
7
Users in the cell
2006-01-31
8
9
10 11
Results, System Throughput
 New implementation (Algorithm 2) has better
performance than the simpler one (Algorithm 1)
Average system throughput [kbps]
1800
1600
1400
1200
1000
800
600
400
Algorithm 1
Algorithm 2
200
Theoretical max throughput
0
0
© Ericsson AB 2006
1
2
Teemu Björninen
3
4
5
6
7
Users in the cell
8
9
10
11
12
2006-01-31
Results, User Throughput
User throughput [kbps]
 Individual user throughputs are close to theoretical
calculation
 With small grant Ue is able to fully exploit the grant
 With four and six users the scheduling functionality
allows ”too good” throughputs
1800
1600
1400
1200
Algorithm 1
Algorithm 2
Theoretical
1000
800
600
400
200
0
0
1
2
3
4
5
6
7
8
9
10
11
12
Users in the cell
© Ericsson AB 2006
Teemu Björninen
2006-01-31
Results, Allowed E-TFC
 In a single user case the distribution of the biggest
allowed E-TFCs of algorithm one is more spread than
algortihm two
12000
Allowed times
10000
8000
Algorithm 1
Algorithm 2
6000
4000
2000
0
25 30 35 40
45 50 55
60 65 70
75 80 85
90 95 100
E-TFC
© Ericsson AB 2006
Teemu Björninen
2006-01-31
Results, Allowed E-TFC
 When the user amount in the cell increases, the
distribution figure of allowed E-TFCs has only one or
two spikes. Placement of spikes moves to left on X-axis
when user amount increases
120000
Algorithm 1
Allowed times
100000
Algorithm 2
80000
60000
40000
20000
0
25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59
E-TFC
© Ericsson AB 2006
Teemu Björninen
2006-01-31
Conclusions
 All three measured indicators show that implemented
Algorithm 2 performs better in power and interference
limited situations
 Enhanced Uplink requires quite high transmission
power. Ue has to operate close to max tx power
 Parameter selection is very important!
– Pdu size
– Max bit rate
– Used scheduler type
© Ericsson AB 2006
Teemu Björninen
2006-01-31
© Ericsson AB 2006
Teemu Björninen
2006-01-31