CNT Thesis
Transcript of CNT Thesis
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Outline Introduction
Background Resource Allocation Strategy for GPRS
Analytical Model
Numerical Result Conclusion
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Introduction (1/2) Radio resource allocation for GPRS
Single rate vs. multirate
Time slots vs. radio blocks
Different strategies to partition theavailable cell capacity
Complete Sharing (CS) Complete Partitioning (CP)
Partial Sharing (PS)
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Introduction (2/2) This thesis
Focuses on CP and PS strategy.
Allocates downlink radio resource by radioblocks.
Two types (rates) of GPRS user.
Analyzes and evaluates performance fordifferent strategy.
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Background GPRS network architecture
GPRS air interface TBF and TFI
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GPRS Network Architecture (1/2)
It fits in with the existing GSM PLMN
Two new network elements Serving GPRS Support Node (SGSN)
Gateway GPRS Support Node (GGSN)
Many new interfaces
Gb, Gi, Gn, etc.
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GPRS Network Architecture (2/2)
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GPRS Air Interface Frequency-Division Duplex, FDD
Combination of Frequency and Timedivision multiple access, FDMA/TDMA
52-multiframe
Physical channels and logical channels
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GPRS Air Interface
52-multiframe
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GPRS Air Interface
Physical Channels Eight physical channels (TS0 to TS7) per
carrier.
The physical channel that is used for packetlogical channels is called a packet datachannel (PDCH).
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TBF and TFI (1/3)A temporary block flow (TBF) is a
physical connection between the MSand the network side to support datatransfer.
Once the data transfer is finished, the
TBF is released.
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TBF and TFI (2/3) Each TBF is identified by a temporary
flow identity (TFI) assigned by thenetwork.
PDCH multiplexing
TBFs which belonging to different MS can
share the same PDCH.
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TBF and TFI (3/3)
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Resource Allocation Strategy
for GPRS Radio resource partition strategies
Complete Partitioning (CP)
Partial Sharing (PS)
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Resource Allocation Strategy Complete
Partitioning TS0 to TS4 are GSM user only, and TS5
to TS7 are GPRS user only
This two partitions are independent
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Resource Allocation Strategy
Partial SharingA shared time slot
This two partitions are dependent
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Analytical Model for CP In CP case, GSM and GPRS partitions
are independent, so we can analyze this
two partitions separately. System description
State definition
State transition diagrams
Balance equations
Performance metrics
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Analytical Model for CP
System Description Two types of user
Class 1 (1+1) and class 2 (2+1)
The request is Poisson.Arrival rate are 1 and 2, respective.
The service time of each request is
exponential distribution Mean service time are 1/1 and 1/2,
respective.
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Analytical Model for CP
State Definition State x=(i, j, k)
i = the number of PDCH is used
j = the number of class 1 user
k = the number of class 2 user
An example
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Analytical Model for CP
State Transition Diagrams Define R = j +2k, and MAX_PDCH is
the maximum number of GPRS time slot
that can be used. Four cases
_ 2 R MAX PDCH u
0 _ R MAX PDCH _ R MAX PDCH !
_ 1 R MAX PDCH !
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Analytical Model for CP
State Transition Diagrams
The most straightforward
No need to consider i
_ 2 R MAX PDCH u
An example
MAX_PDCH = 3
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Analytical Model for CP
State Transition DiagramsGeneralized state transitiondiagram for case 1
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Analytical Model for CP
Balance Equations
3 1 4 2 5 2 1 2 , ,1 1, 1, 3 1 1, 1, 2 2, , 1
2 1, , 1 4 2 2, , 1
( 1) ( 1)
( 1)
i j k
i j k i j k i j k
i j k i j k
j k
j k
k
H P H P H P Q Q T
Q T H P T Q T
Q T H P T
!
1 1 2 2 1 2 , ,1 , 1, 3 1 1, 1, 2 , , 1 4 2 2, , 1( 1) ( 1)
i j k
i j k i j k i j k i j k
j k
j k
H H
H H
!
1 1 2 2 1 2 , ,1 , 1, 1 1 , 1, 2 , , 1 5 2 1, , 1
( 1) ( 1)
i j k
i j k i j k i j k i j k
j k
j k
H P H P Q Q T
Q T H P T Q T H P T
!
1 1 2 2 1 2 , ,1 , 1, 1 1 , 1, 2 , , 1 2 2 , , 1
( 1) ( 1)
i j k
i j k i j k i j k i j k
j k
j k
H H
H H
!
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Analytical Model for CP
Performance MetricsAccording steady-state probabilities, we
can fine the class 1 and class 2 blockingprobability (Pb1 and Pb2), and radioresource utilization U.
1 , ,
, ,
b i j k
i j k E
P T
!
2 , , , ,
, , , ,
b i j k i j k
i j k E i j k F
P T T
!
( , , )
, ,
1
_i j k
i j k S
U iMAX PDCH
T
!
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PS case is more complex than CP case.
In addition to GPRS user, there is GSM
user in the system as well. GSM user
New call and handover call are Poisson
Arrival rate Service time is exponential distribution
Mean service time
Analytical Model for PS (1/2)
v n hP P P!
1 1 s dv Q Q Q!
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Analytical Model for PS (2/2) State x=(i, j, k, l, m)
i = the number of PDCH being used
j = the number of GPRS class 1 user k = the number of GPRS class 2 user
l = the number of GSM user
m = indicate who is using shared TS 12 different cases, 12 different balance
equations.
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Analytical Model for PS
Performance Metrics (1/2)According to these balance equations,
we can calculate steady-state
probabilities, and compute performancemetrics as well.
GPRS class 1 blocking probability
GPRS class 2 blocking probability
1 ( , , , , )( , , , , )
b i j k l mi j k l m H I
P T
!
2 ( , , , , )
( , , , , )
b i j k l m
i j k l m I H J K
P T
!
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Analytical Model for PS
Performance Metrics (2/2) GSM new call blocking probability
GSM handover call blocking probability
Radio resource utilization
( , , , , )
( , , , , )
nvn i j k l
i j k l
L Mn h
PP
T
P P
!
( , , , , )
( , , , , )
hvh i j k l
i j k l L Mn h
PP
TP P
!
( , , , , )
( , , , , )
1( )
_ _ 1i j k l
i j k l S
i lGPRS TS GSM TS
T
!
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Numerical Result Comparison between analytic and
simulated result.
Comparison between CP and PS forGPRS traffic.
Utilization vs. load
Define
GPRS load
GSM load
1 1
1 2
2 ( )GPRS L erlangP P
Q Q!
( )vGSMv
L erlangP
Q
!
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Comparison between analytic
and simulated result (1/2)
0
0.1
0.2
0.3
0.4
0.5
0.6
3.6 7.2 10.8 14.4 18 21.6 25.2 28.8 32.4 36 39.6 43.2 46.8 50.4 54 57.6
O ffered Load
B
locking
Prob
class 1-
class 1-
class 2-
class 2-
CP case 1 2 0.1Q Q! !
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Comparison between analytic
and simulated result (2/2) PS case
0
0.05
0.1
0.15
0.2
0.25
4 8 12 16 20 24 28 32 36 40 44 48
G PRS Load
B
loc
king
Pro
ba
bi
class 1-
class 1-
class 2-
class 2-
GSM -
GSM -
1 23.2, 0.2, 0.4GPRS Load Q Q! ! !
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Comparison between CP and
PS for GPRS request
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
4 8 12 16 20 24 28 32 36 40 44 48
G PRS Load
B
locking
Probabi
class 1-CP
class 1-PS
class 2-CP
class 2-PS
1 23.2, 0.2, 0.4, 0.0083vGPRS Load Q Q Q! ! ! !
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Utilization vs. offered load
(1/2)
0
0.2
0.4
0.6
0.8
1
1.2
1 2 3 4 5 6 7 8 9 10 11 12
Offered Load (Erlangs)
U
tilizati
k=1
k=5
CP case 1 2 1 20.2, 0.4, k Q Q P P! ! !
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Utilization vs. offered load
(2/2) PS case
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
G SM Load (Erlangs)
U
tilizati
4 erlangs
8 erlangs
18 erlangs
28.8 erlangs
1 20.2, 0.4, 0.0083v Q Q Q! ! !
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Conclusion Radio block based CP and PS strategies
was proposed.
Built analytic model for both strategies.Verified analytic model by simulation.
Showed that PS case scheme performed
better than CP one. GPRS radio resource can be fully
utilized easily.
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Future work Impact of cell-reselection.
Priority for GSM handover call.
Preemptive mechanism.
Adaptive resource allocation.
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The End