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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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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

_ 2 R MAX PDCH u

0 _ R MAX PDCH _ R MAX PDCH !

_ 1 R MAX PDCH !

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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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State Transition DiagramsGeneralized state transitiondiagram 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

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


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


j k

j k

H H

H H

!

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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

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CNT Thesis