UMTS simulator
Alberto Bona, Maurizio Conti
Politecnico di Torino
Scenario(1)



General Assumption:
– Simulator time step is equal to 1 frame (10 ms)
Advantages:
– Bit rate can be varied every TTI
– Transport channel accuracy
– Simpler and faster
Limitations:
– Power control is slot based  neglected
– RACH and CPCH collisions are modelled on a
frame basis
Alberto Bona, Maurizio Conti
2
Scenario(2)

1 RNC  SRNC  CRNC
– Simulation of intra-RNC
handover is possible
– Simulation of inter-RNC
handover is not precluded


Node-B number is an input
parameter
Node-B inherits generic-BTS
behaviour adding UMTS
features
RNS
NODE
B
NODE
B
NODE
B
NODE
B
RNC
NODE
B
NODE
B

Structure is adherent to UMTS
standards
Alberto Bona, Maurizio Conti
3
Scenario(3)




RNC maintains (UTRANside) peer-UE protocol
instantiation
RNC creates RRC layer
which is responsible for
channel allocation
RNC maintains UE
schedulation references
Each Node-B has a
MAC_CSH entity
responsible for common
transport channel
transmission and reception
Alberto Bona, Maurizio Conti
NODE_B
(UMTS_BTS)
UE
(UMTS_MS_NODE)
RNC
U-plane
C-plane
U-plane
RRC
UL
SOURCES
DL
SOURCES
RLC
RLC
C-plane
RRC
MAC D
MAC
MS
MAC
CSH
MAC
UTRAN
UL/DL
Uu
4
Protocol implementation(1): RACH

It’s an uplink transport channel

Slotted-aloha based, allows transmission of 1
frame

UE has to restart access procedure for each
transmission

RACH will be used for low bit-rate data
transmissions which don’t need high
throughput
Alberto Bona, Maurizio Conti
5
Protocol implementation(2): CPCH

It’s an uplink transport channel

Slotted-aloha based with fast acquisition
indication and collision detection

UE, once access has been completed, is the
owner of the code for NMAX consecutive
frames

CPCH will be used for data transmissions
which require higher throughput
Alberto Bona, Maurizio Conti
6
Protocol implementation(3): DSCH

It’s a downlink transport channel

UE share the same code, multiplexed on a
frame by frame basis

UE multiplexing is granted through polling on
a signalling channel (at present Round Robin)

DSCH will be used for non real time traffic:
WWW, FTP...
Alberto Bona, Maurizio Conti
7
UE-structure (MAC_D)





RB_mapping_info: data
(priority, log-CH_ID) for logCH to tr-CH mapping
C/T switch: routes PDU
towards TX buffers
TX buffers: on DCH or on
common tr-CH
DCH TF: Transport Format
for DCH; variable every TTI
C/T demux: allows
demultiplexing of blocks
from tr-CH to log-CH
MAC-REQ.
MAC-IND.
MAC MS
MAC MAC_D
CSH
TX
RB_
mapping
INFO
C/T
Switch
MAC-REQ.
Flow
-control
buffer
TFCS
DCH TF
C/TDemux
DCH
buffer
PHY-REQ
Alberto Bona, Maurizio Conti
RX
PHY-IND.
8
UE-structure (MAC_CSH)

TCTF-Insert: data and
signalling multiplexing
on transport channels
CMAC REQ
MAC MS
MAC-c/sh



TX Buffers: on RACH
and CPCH
RACH and CPCH TF: TF
for transport channels
TCTF-Read: data
(towards MAC_D) and
signalling blocks
demultiplexing
Alberto Bona, Maurizio Conti
MAC REQ
TCTF - Insert
TCTF -Read
RACH buffer
CPCH buffer
TF
RACH
PHY IND
TF
CPCH
MAC D
PHY REQ
PHY REQ
PHY IND PHY IND
DSCH (FACH)
9
UTRAN-structure (MAC_CSH)


Sheduling-Priority
Handling: selects UE for TX
on common transport CH.
CMAC IND
MAC UTRAN
Controllers:
– RACH: manages collisions
with a frame based model
MAC D 1
Scheduling
Priority Handling
TCTF - Insert
– CPCH: manages collisions
(as RACH) and provides
codes for UE transmissions

MAC_D list: maintains info
about UE under Node B
control
Alberto Bona, Maurizio Conti
PHY IND
TCTF - Read
RACH
Controller
CPCH
Controller
MAC D 2
MAC D n
MAC-c/sh
RACH PHY
TRANSFER
CPCH PHY
TRANSFER
DSCH
PHY REQ
(FACH)
PHY REQ
10
UMTS validation tests and
simulations
Alberto Bona, Maurizio Conti
Politecnico di Torino
Validation tests: RACH


Transfer delay has
constant
characteristics
Increasing UE
number, arrived
packets decrease
because of collision
Mean transfer delay is
independent by UE
number
Alberto Bona, Maurizio Conti
MAC block Transfer Delay on RACH
1
0,9
Number of blocks

0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0
0
20
40
60
80
100
120
140
160
180
200
220
Frame
12
240
Validation tests: CPCH
MAC block transfer delay on CPCH

Alberto Bona, Maurizio Conti
1,2
1
Number of blocks
1 IP packet is
transferred releasing
signature  more than 1
max in picture
 1 IP packet needs 3
signature allocation to
be transferred
 time between max is
due to signature
contention or lack of
codes
0,8
0,6
0,4
0,2
0
0
10
20
30
40
50
60
70
80
90
Frame
13
UMTS traffic sources

Based on UMTS 30.03
– 25 packet per ON session; OFF session: 3 s
– 480 byte per packet

UDD64
– constant interarrival time between packets 62.5 ms
– 2 blocks per frame
– 320 bit per block

UDD144
– constant interarrival time between packets 27 ms
– 4 blocks per frame
– 360 bit per block
Alberto Bona, Maurizio Conti
14
RACH Results: collision probability
Collision probability on RACH
1
Probability
3 codici - UDD144
4 Codici - UDD144
4 Codici - UDD64
0,1
3 Codici - UDD64
0,01
1
2
3
4
5
6
7
8
9
10
Users
Alberto Bona, Maurizio Conti
15
RACH Results: throughput
Throughput on RACH
35
30
Kbit/s
25
3 codici - UDD144
4 Codici - UDD144
4 Codici - UDD64
3 Codici - UDD64
20
15
10
5
0
1
2
3
4
5
6
7
8
9
10
Users
Alberto Bona, Maurizio Conti
16
CPCH Results: blocking probability
Collision probability on CPCH
1
3 Codici - UDD144
Probability
3 Codici - UDD64
4 Codici - UDD144
0,1
4 Codici - UDD64
0,01
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
Users
Alberto Bona, Maurizio Conti
17
CPCH Results: throughput
Throughput on CPCH
85
80
75
Kbit/s
70
65
3 Codici - UDD144
60
3 Codici - UDD64
55
4 Codici - UDD144
50
4 Codici - UDD64
45
40
35
30
25
20
15
1 2
3 4
5
6 7
8 9 10 11 12 13 14 15 16 17 18 19 20
Users
Alberto Bona, Maurizio Conti
18
CPCH Results: MAC transfer delay
MAC block transfer delay on CPCH
5
4
3 Codici - UDD144
3 Codici - UDD64
3
s
4 Codici - UDD144
4 Codici - UDD64
2
1
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
Users
Alberto Bona, Maurizio Conti
19
DSCH Results: throughput-UDD144
Throughput on DSCH- UDD 144
110
100
90
kbit/s
80
70
DCH DL
60
1 codice
50
2 codici
40
3 codici
30
20
10
1
2
3
4
5
6
7
8
9
10
Users
Alberto Bona, Maurizio Conti
20
DSCH Results: MAC transfer delay
MAC block transfer delay on DSCH - UDD 144
3000
2000
ms
1 codice
2 codici
3 codici
1000
0
1
2
3
4
5
6
7
8
9
10
Users
Alberto Bona, Maurizio Conti
21
GPRS-UMTS Comparison(1)

GPRS model: 1 PDCH signalling, 7 PDCH
data, dynamic allocation, Round Robin
scheduling
 UMTS model: 3 codes per transport
channel
 Traffic source: UDD64
Alberto Bona, Maurizio Conti
26
GPRS-UMTS Comparison(2)
(GPRS-UMTS) uplink throughput comparison - UDD64
1,2
1
0,8
RACH
0,6
CPCH
GPRS
0,4
0,2
0
1
2
3
4
5
6
7
8
9
10
Users
Alberto Bona, Maurizio Conti
27
GPRS-UMTS Comparison(3)
(GPRS-UMTS) downlink throughput comparison - UDD64
1,2
1
0,8
DSCH
0,6
DCH
GPRS
0,4
0,2
0
1
2
3
4
5
6
7
8
9
10
Users
Alberto Bona, Maurizio Conti
28