Transcript GPRS simulator - Politecnico di Torino

Simulazione di protocolli a
pacchetto per reti radiomobili:
GPRS ed UMTS
Alberto Bona, Maurizio Conti
Politecnico di Torino
Simulator purposes

Analyzing GPRS and UMTS performances
on radio interface in presence of different
traffic sources
 Implementing MAC layer source code for
both GPRS and UMTS systems
 Comparing simulation and theoretical
model results
 Creating a software instrument open to
future developements and extensions
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Alberto Bona, Maurizio Conti
Simulator description

General features
 Simulation environment
 BTS features
 GPRS simulator structure
– BTS structure
– MS structure

GPRS simulations
– traffic sources
– results
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Alberto Bona, Maurizio Conti
General features

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Programming language: C++
Simulator type: synchronous + events
Main interest for “higher” layer protocol
performances
Simplified physical layer model
Closed topology
Simultaneous presence of UL and DL MS
REFERENCE DOCUMENTS
ETSI and 3GPP standards + technical papers
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Alberto Bona, Maurizio Conti
Simulation environment

Based on suburban model defined in UMTS
30.03:
– Base station distance: 6 or 1.5 km
– Cell radius: 2 km or 500 m

Simulations of other environments are not
precluded:
– changing base station distance and cell radius
– changing propagation model

Users mobility:
– Every position update, users step from current
pixel to an adjacent one
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Alberto Bona, Maurizio Conti
BTS features
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Each BTS can be
equipped with both
omnidirectional and
sectorial antennas
Irradiation diagram is
specified by an input file
Propagation model:
Pr  Pt
G ms G bts
Atot
Atot
dB
 A pr
dB
 A sh
dB
 Af
dB
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Alberto Bona, Maurizio Conti
GPRS-BTS Model
MS’stack
list in BTS
PRACH-contr olle r
Target MS
TX
IDLE
waiting
MAC
MAC
MAC
Buffer
TX
Buffer
TX
Buffer
TX
Waiting
MS-list
MAC
To MS
Buffer
RX
PRACH
management
Peer
pointer
to RXBuffer
RSC-allocator
TX-allocat or
DYN.
alloc
E-DYN.
alloc
FIXED
alloc
DYN.
sched
To Buffer
TX
E-DYN.
sched
FIXED
sched
52 frame with 12 b locks
PDCH0
B0 B1
1
B2
PDCH0
1
fi
fi
1
PDCH7
USF
0
0
USF
7
Dyn
mat rix
PDCH
status
PDCH7
Block
0
Fixed
mat rix
Block
11
Schedulation
points
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GPRS-BTS structure
GPRS-BTS Model
MS’stack
li st in BTS
IDLE
waiting
MAC
MAC
MAC
Buffer
TX

PRACH-controller:
– responsible for MS UL access
Buffer
TX
RSC-allocator:
Buffer
TX
Waiting
MS-list
MAC
To MS
Buffer
RX
PRACH
management
Peer
pointer
to RXBuffer
RSC-allocator
TX-allocat or
DYN.
alloc
E-DYN.
alloc
FIXED
alloc
DYN.
sched
To Buffer
TX
E-DYN.
sched
FIXED
sched
52 frame with 12 b locks
PDCH0
B0 B1
1
B2
PDCH0
1
fi
fi
1
PDCH7
USF
0

PRACH-contr olle r
Target MS
TX
0
USF
7
Dyn
mat rix
PDCH
status
PDCH7
Block
0
Fixed
mat rix
Block
11
Schedulation
points
– responsible for resource allocation
•
Dyn_matrix: maintains information about Dynamic and
Extended dynamic allocation (USF)
• Fixed_matrix: stores channel occurrences (PRACH,
PAGCH) and MS fixed-allocation
• PDCH status: carries information about PDCH status
(GSM or GPRS)
• Dyn, E-Dyn, Fixed_alloc: implement allocation
algorithms
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Alberto Bona, Maurizio Conti
GPRS-BTS Model
GPRS-BTS structure
MS’stack
li st in BTS
IDLE
waiting
MAC
MAC
MAC
Buffer
TX
Buffer
TX
Buffer
TX
Waiting
MS-list
MAC
PRACH
management
TX-allocat or
E-DYN.
alloc
DYN.
alloc
TX-allocator:
– responsible for frame scheduling
– schedulation is performed at the
beginning of each block
– transmission is performed frame
by frame
To MS
Buffer
RX
Peer
pointer
to RXBuffer
RSC-allocator

PRACH-contr olle r
Target MS
TX
To Buffer
TX
FIXED
sched
52 frame with 12 b locks
B0 B1
1
PDCH0
B2
PDCH0
1
fi
fi
1
PDCH7
USF
0
0
USF
7
Dyn
mat rix
PDCH
status
PDCH7
Block
0
Fixed
mat rix
Block
11
Schedulation
points
• TX_matrix: stores information about the block
owner, either a controller or a MS
• Dyn, E-dyn, fixed_sched: perform algorithms for
PDCH condivision through RSC information
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Alberto Bona, Maurizio Conti
E-DYN.
sched
DYN.
sched
FIXED
alloc
GPRS MAC MS structure

MAC-buffer: stores
MAC-blocks ready for
transmission and
controls access to
uplink PDCH
 Header: inserts header
to RLC-PDU, updating
fields for statistics
 PRACH-controller:
responsible for access
procedures
GPRS-MAC-MS-TX model
RLC
PRACH
controller
Standard
algorithms
Header
MAC
buffer
TX
controller
PEER
MAC
PHY
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Alberto Bona, Maurizio Conti
Simulations

Validation test
 Resource sharing between GPRS and GSM
(1 carrier)
 GPRS traffic multiplexing on 1 PDCH
 GPRS traffic multiplexing on 7 PDCH
COMMON FEATURES
• Dynamic allocation
• Round-Robin schedulation
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Alberto Bona, Maurizio Conti
GPRS traffic sources

ON-OFF status length is negative
exponentially distributed
 Mean time ON/OFF: 20/40 s
 Mean time between packet: 500 ms
 Packet length depends on offered bit rate:
– 1.9, 6.4, 11.2, 19.2, 64 kbit/s (peak)

CS3 coding scheme
 Packets are segmented by RLC and
passed to MAC layer
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Alberto Bona, Maurizio Conti
Performance parameters
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GPRS blocking probability
GSM blocking probability
Access delay (UL)
MAC block transfer delay
Session throughput
IP packet throughput
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Alberto Bona, Maurizio Conti
Validation test
PRACH access delay
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
50
100
150
200
250
Frames
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Alberto Bona, Maurizio Conti
Resource sharing between GSM
and GPRS (1 carrier)

GSM sources
–
–
–
–

Mean call length 1/m. = 120 s
Mean call interarrival time 1/l
Offered load l/m = M = 2, …, 8
100 users per cell
GPRS sources
– Offered load per user: 6.4, 11.2, 19.2 kbit/s (peak)
– 4 users per cell
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Alberto Bona, Maurizio Conti
Resource sharing
GPRS blocking probability - UPLINK
1
0.1
GSM
6.4 kbit/s
11.2 kbit/s
19.2 kbit/s
0.01
0.001
2
3
4
5
6
7
8
M
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Alberto Bona, Maurizio Conti
Resource sharing
GPRS blocking probability - DOWNLINK
1
0.1
GSM
6.4 kbit/s
11.2 kbit/s
19.2 kbit/s
0.01
0.001
2
3
4
5
6
7
8
M
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Alberto Bona, Maurizio Conti
Resource sharing
MAC transfer delay - UPLINK
4000
3500
3000
ms
2500
6.4 kbit/s
2000
11.2 kbit/s
19.2 kbit/s
1500
1000
500
0
2
3
4
5
6
7
8
M
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Alberto Bona, Maurizio Conti
Resource sharing
Session throughput - UPLINK
16
14
12
kbit/s
10
6.4 kbit/s
8
11.2 kbit/s
19.2 kbit/s
6
4
2
0
2
3
4
5
6
7
8
M
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Alberto Bona, Maurizio Conti
Only GPRS traffic multiplexing
No GSM sources
 Multiplexing on 1 PDCH:

– Offered load per user: 1.9, 6.4, 11.2, 19.2
kbit/s (peak)
– 1, 2, …, 10 users per cell

Multiplexing on 7 PDCH:
– Offered load per user: 11.2, 19.2 kbit/s
(peak)
– 1, 5, 10, …, 25 users per cell
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Alberto Bona, Maurizio Conti
Multiplexing on 1 PDCH
MAC transfer delay - DOWNLINK
20000
ms
15000
1.9 kbit/s
6.4 Kbit/s
10000
11.2 kbit/s
19.2 Kbit/s
5000
0
1
2
3
4
5
6
7
8
9
10
Users
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Alberto Bona, Maurizio Conti
Multiplexing on 1 PDCH
Session throughput - DOWNLINK
16
kbit/s
14
12
1.9 kbit/s
10
6.4 kbit/s
8
6
11.2 kbit/s
19.2 Kbit/s
4
2
0
1
2
3
4
5
6
7
8
9
10
Users
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Alberto Bona, Maurizio Conti
Multiplexing on 1 PDCH
kbit/s
Packet throughput - DOWNLINK
18
16
14
12
10
8
6
4
2
0
1.9 kbit/s
6.4 kbit/s
11.2 kbit/s
19.2 kbit/s
1
2
3
4
5
6
7
8
9
10
Users
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Alberto Bona, Maurizio Conti
Multiplexing on 7 PDCH
ms
Access delay
180
160
140
120
100
80
60
40
11.2 kbit/s
19.2 kbit/s
20
0
1
5
10
15
20
25
Users
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Alberto Bona, Maurizio Conti
Multiplexing on 7 PDCH
MAC transfer delay - DOWNLINK
1200
1000
ms
800
11.2 kbit/s
600
19.2 kbit/s
400
200
0
1
5
10
15
20
25
Users
25
Alberto Bona, Maurizio Conti
Multiplexing on 7 PDCH
kbit/s
Session throughput - DOWNLINK
20
18
16
14
12
10
8
6
4
2
0
11.2 kbit/s
19.2 kbit/s
1
5
10
15
20
25
Users
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Alberto Bona, Maurizio Conti
Multiplexing on 7 PDCH
kbit/s
Packet throughput - DOWNLINK
100
90
80
70
60
50
40
30
20
10
0
11.2 kbit/s
19.2 kbit/s
1
5
10
15
20
25
Users
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Alberto Bona, Maurizio Conti