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無線分封數據服務網路之高使用率 資源分配策略與效能評估. High Utilization Resource Allocation and Performance Evaluation for GPRS Networks. 研 究 生:蔡鎮年 指導教授:柯開維 博士. Outline. Introduction Background Resource Allocation Strategy for GPRS Analytical Model Numerical Result Conclusion. Introduction (1/2). - PowerPoint PPT Presentation
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High Utilization Resource Allocation and Performance Evaluation for GPRS Networks
研 究 生:蔡鎮年指導教授:柯開維 博士
無線分封數據服務網路之高使用率資源分配策略與效能評估
2004/7/14 2
Outline
Introduction Background Resource Allocation Strategy for GPRS Analytical Model Numerical Result Conclusion
2004/7/14 3
Introduction (1/2) Radio resource allocation for GPRS
Single rate vs. multirate Time slots vs. radio blocks
Different strategies to partition the available cell capacity Complete Sharing (CS) Complete Partitioning (CP) Partial Sharing (PS)
2004/7/14 4
Introduction (2/2)
This thesis Focuses on CP and PS strategy. Allocates downlink radio resource by
radio blocks. Two types (rates) of GPRS user. Analyzes and evaluates performance
for different strategy.
2004/7/14 5
Background
GPRS network architecture GPRS air interface TBF and TFI
2004/7/14 6
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.
2004/7/14 7
GPRS Network Architecture (2/2)
2004/7/14 8
GPRS Air Interface
Frequency-Division Duplex, FDD Combination of Frequency and
Time division multiple access, FDMA/TDMA
52-multiframe Physical channels and logical
channels
2004/7/14 9
GPRS Air Interface 52-multiframe
2004/7/14 10
GPRS Air Interface Physical Channels Eight physical channels (TS0 to TS7) per
carrier. The physical channel that is used for
packet logical channels is called a packet data channel (PDCH).
2004/7/14 11
TBF and TFI (1/3)
A temporary block flow (TBF) is a physical connection between the MS and the network side to support data transfer.
Once the data transfer is finished, the TBF is released.
2004/7/14 12
TBF and TFI (2/3)
Each TBF is identified by a temporary flow identity (TFI) assigned by the network.
PDCH multiplexing TBFs which belonging to different MS can
share the same PDCH.
2004/7/14 13
TBF and TFI (3/3)
2004/7/14 14
Resource Allocation Strategy for GPRS
Radio resource partition strategies Complete Partitioning (CP) Partial Sharing (PS)
2004/7/14 15
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
2004/7/14 16
Resource Allocation Strategy
Partial Sharing
A shared time slot This two partitions are dependent
2004/7/14 17
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
2004/7/14 18
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 λ1 and λ2, respective. The service time of each request is ex
ponential distribution Mean service time are 1/μ1 and 1/μ2, resp
ective.
2004/7/14 19
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
2004/7/14 20
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
_ 2R MAX PDCH
0 _R MAX PDCH
_R MAX PDCH
_ 1R MAX PDCH
2004/7/14 21
Analytical Model for CP
State Transition Diagrams
The most straightforward
No need to consider i
_ 2R MAX PDCH
An exampleMAX_PDCH = 3
2004/7/14 22
Analytical Model for CP
State Transition Diagrams
Generalized state transition diagram for case 1
2004/7/14 23
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
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
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
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
2004/7/14 24
Analytical Model for CP
Performance Metrics
According steady-state probabilities, we can fine the class 1 and class 2 blocking probability (Pb1 and Pb2), and radio resource utilization U.
1 , ,
, ,b i j k
i j k E
P
2 , , , ,
, , , ,b i j k i j k
i j k E i j k F
P
( , , )
, ,
1
_ i j ki j k S
U iMAX PDCH
2004/7/14 25
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 h
1 1 s dv
2004/7/14 26
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.
2004/7/14 27
Analytical Model for PS
Performance Metrics (1/2) According to these balance
equations, we can calculate steady-state probabilities, and compute performance metrics 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
2 ( , , , , )( , , , , )
b i j k l mi j k l m I H J K
P
2004/7/14 28
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 m
i j k l m L Mn h
P
( , , , , )( , , , , )
hvh i j k l m
i j k l m L Mn h
P
( , , , , )( , , , , )
1( )
_ _ 1 i j k l mi j k l m S
U i lGPRS TS GSM TS
2004/7/14 29
Numerical Result
Comparison between analytic and simulated result.
Comparison between CP and PS for GPRS traffic.
Utilization vs. load Define
GPRS load GSM load
1 1
1 2
2 ( )GPRSL erlang
( )vGSM
v
L erlang
2004/7/14 30
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
Offered Load
Blo
ckin
g P
robability
class 1-理論值
class 1-模擬值
class 2-理論值
class 2-模擬值
CP case 1 2 0.1
2004/7/14 31
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
GPRS Load
Blo
ckin
g Pro
babi
lity
class 1-理論值class 1-模擬值class 2-理論值class 2-模擬值GSM-理論值GSM-模擬值
1 2 3.2, 0.2, 0.4GPRS Load
2004/7/14 32
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 48GPRS Load
Blo
ckin
g Pro
babi
lity
class 1-CPclass 1-PSclass 2-CPclass 2-PS
1 2 3.2, 0.2, 0.4, 0.0083vGPRS Load
2004/7/14 33
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 12Offered Load (Erlangs)
Utiliza
tion
k=1k=5
CP case 1 2 1 20.2, 0.4, k
2004/7/14 34
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 5GSM Load (Erlangs)
Utiliza
tion
4 erlangs8 erlangs18 erlangs28.8 erlangs
1 20.2, 0.4, 0.0083v
2004/7/14 35
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.
2004/7/14 36
Future work
Impact of cell-reselection. Priority for GSM handover call. Preemptive mechanism. Adaptive resource allocation.
2004/7/14 37
The End