High Utilization Resource Allocation and Performance Evaluation for GPRS Networks

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

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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 the available 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

radio blocks. Two types (rates) of GPRS user. Analyzes and evaluates performance

for different 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

Time division 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

packet logical channels is called a packet data channel (PDCH).

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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.

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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.

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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 Sharing

A 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 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.

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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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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

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State Transition Diagrams

The most straightforward

No need to consider i

_ 2R MAX PDCH

An exampleMAX_PDCH = 3

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State Transition Diagrams

Generalized state transition diagram for case 1

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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


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


j k

j k

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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

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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 h

1 1 s dv

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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 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

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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 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

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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

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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

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

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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

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

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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 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

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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 12Offered Load (Erlangs)

Utiliza

tion

k=1k=5

CP case 1 2 1 20.2, 0.4, k

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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 5GSM Load (Erlangs)

Utiliza

tion

4 erlangs8 erlangs18 erlangs28.8 erlangs

1 20.2, 0.4, 0.0083v

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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

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High Utilization Resource Allocation and Performance Evaluation for GPRS Networks