soft handover performance study in the direct sequence ... · pdf filesoft handover...

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Soft Handover Performance study in the Direct Sequence WCDMA Radio network Simulator

Author: Yang Fang / Communication Laboratory

Supervisor: Professor Sven-Gustav Häggman Instructor: PH.D Michael Hall

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Table of Content

• Handover Introduction

• NETSIM Introduction– “NETSIM” Structure and modules Introduction

– Channel Simulator

– Network Simulator

• Soft Handover algorithms Introduction– “Window-average” algorithm

– “Real-time” algorithm

• Simulation result and Performance study

• Drop call trace tool

• Future work

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Handover Introduction

4

Handover Introduction

5

Handover Introduction --- Interfrequency Handover

6

Handover Introduction --- Intrafrequency Handover

7

Handover Introduction --- Intersystem Handover

8

Handover Introduction --- Soft Handover

9

Handover Introduction --- Softer Handover

10

NETSIM Introduction

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NETSIM Introduction

• NETSIM - simulation tool for study of planning methods and control algorithm for WCDMA cellular Radio Network

• Platform: Unix

• Language: C

• NETSIM can simulate: Voice and data service, packet switched traffic, circuit switched traffic, different user behavior,Radio network control functions (HO, Admission, Power Control)

• Simulation result: System capacity as a function of traffic, performance of network control algorithm, etc.

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NETSIM Structure and Modules --- Structure

Traffic Model

Network Performance Analysis

Network Model

WCDMA Simulation

1. Uplink algorithm;2. Downlink algorithm;3. Access Control4. Admission control;5. Soft handover 6. Power control

Channel Simulator

Net

wor

k S i

mul

ator

NETSIM

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Channel Simulator of NETSIM

∑−

=

−=1

0)exp()()(

K

kkkk jttath θδ

• Advantage: Model considered as accurate• Disadvantages: Computing intensive (large Memory and long simulation time required)

• Current version using Raytracingmodel

• Impulse response is

Map of simulation environment

14

Network Simulator of NETSIM

Traffic Model Network Model

WCDMA Simulation

1. Uplink algorithm;2. Downlink algorithm;3. Access Control4. Admission control;5. Soft handover 6. Power controlN

etw

ork

S im

ulat

or

Network Performance Analysis

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NETSIM Structure and Modules --- Modules

Initialization Module

Generation Module

Traffic Module

Mobility Module

Propagation Module

Interference Module

Average Module

Access Module

Admission Module

Active set Module

Quality Module

Power Module

Mobile Station

Radio Channel

Base

Station

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Soft Handover algorithms Introduction

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Handover Introduction --- Soft Handover

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Soft Handover algorithm Introduction--- “Window-average” algorithm

AS_Th – AS_Th_HystAs_Rep_Hyst

As_Th + As_Th_Hyst

Cell 1 ConnectedEvent 1A

⇒ Add Cell 2Event 1C ⇒

Replace Cell 1 with Cell 3Event 1B ⇒

Remove Cell 3

CPICH 1

CPICH 2

CPICH 3

Time

MeasurementQuantity

∆T ∆T ∆T

Figure of window-average algorithm from 3GPP 25.922_3/02

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M e a s_ S ig n > B e st_ S s– A s_ T h –

a s_ T h _ H y st for a p er iod o f ∆ T

Y e s

N o(E ve n t 1B )

R e m o ve W or st_ B s inth e A ctive S e t

M e a s_ S ig n > B e st_ S s – A s_ T h+ a s_ T h _H y st

for a p er iod o f ∆ T

N o

Y e s(E ve n t 1 A )

A d d B e st_B s in th e A ctiveS e t

B e st_ C a n d _ S s > W or st_ O ld _ S s +A s_ R e p _ H y st

for a p er iod o f ∆ T

Y e s(E ve n t 1 C )

N o

A c tive Se t F u ll

N oY e s

A d d B e st B S in A c tiveS e t a n d R e m ove W or stB s fr om th A c tive S et

B e g in

Soft Handover algorithm Introduction--- “Window-average” algorithm flow chart

Flow chart of window-average algorithm from 3GPP 25.922_3/02

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Parameters for “Window-average” algorithm

Parameters:

• AS_Th Threshold of Marco-diversity gain in “Window-average” algorithm• AS_Th_hyst Hysteresis of AS_Th• AS_Rep_hyst Replacing Hysteresis in “Window-average” algorithm• HO_Add_time Evaluating window size to add candidate to active set list• HO_Drop_time Evaluating window size to drop one from active set list

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Soft Handover algorithm Introduction--- “Real-time” algorithm

• Always connect to the cells with better or best signal quality

• Swap the cells in the active set frequently

• Response quickly to the change of the communication channel

• No window to evaluate the receiving signal

• Soft handover gain is fixed (equal to the Marco-diversity gain)

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Parameters for “Real-time” algorithm

Parameters:

• AS_3_ratio Marco-diversity gain when using 3 active set in the Soft handover procedure in “Real-time” algorithm

• AS_2_ratio Marco-diversity gain when using 2 active set in the Soft handover procedure in “Real-time” algorithm

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Simulation result and Performance study

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Performance study for different algorithms--- “Window-average” algorithm (1-1)

AS active Threshold 3.98(equal to 6 dB)

AS active Threshold Hysteresis 1.58(equal to 2 dB)

AS active Replacement Threshold Hysteresis 3.98(equal to 6 dB)

AS active Handover add window size 0.5(second)

AS active Handover drop window size 0.5(second)

Group 1 Parameters set

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Successful call vs. drop call(Window size = 0.5 s, AS_Th = 6 dB, AS_Rep_Th = 6dB)

79.50% 79.19%

20.50% 20.81%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

100.00%

AS=3 AS=2

Maximum active set size

Perc

enta

ge (%

)

Calls ended normallyNr. of quality fail calls

Percentage of acting different radio links in the SHO procedure(Window size = 0.5 s, AS_TH = 6 dB, As_Rep_Th = 6 dB)

0.03%1.75% 0.83%

98.23% 99.17%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

100.00%

AS=3 AS=2


Perc

enta

ge(%

) Acting 3 radio link case in thissimulation loopActing 2 radio link case in thissimulation loopActing 1 radio link case in thissimulation loop

Simulation result of parameter set group1

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Successful call vs. Drop call(Window size = 0.5 s, AS_Th = 4 dB, AS_Rep_Th = 4 dB )

79.22% 81.65%

20.78% 18.35%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

100.00%

AS=3 AS=2

Maximum Active set size

Perc

enta

ge (%

)

Calls ended normallyNr. quality failures ul

Percentage of acting different radio links case in SHO procedure(Window size = 0.5 s, AS_Th = 4 dB,AS_Rep_Th = 4 dB)

0.01%0.69% 1.03%

99.31% 98.97%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

100.00%

AS=3 AS=2

Maximum Active Set size

Perc

enta

ge (%



28








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Successful calls vs. Drop calls(Window size = 0.1 s AS_Th = 4dB, AS_Rep_Th= 4 dB)

72.83%80.95%

27.17%19.05%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

AS=3 AS=2


Perc

enta

ge (%

)

Calls ended normallyNr. quality failures ul

Percentage of acting different radio links case(Window size = 0.1 s AS_Th = 4dB, AS_Rep_Th= 4 dB)

0.07%1.96% 3.18%

97.97% 96.82%

0.00%

20.00%

40.00%

60.00%

80.00%

100.00%

120.00%

AS=3 AS=2


Perc

enta

ge (%



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Performance study for different algorithms--- “Window-average” algorithm summary(1)

Comparison table of successful calls and drop calls(Maximum Active set size is 3)

79.50% 79.22%72.83%

20.50% 20.78%27.17%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

WS = 0.5; As_Th= 6db



Different Parameters sets

Perc

enta

ge

Calls ended normallyNr. of quality failures

Percentage of acting different radio links case with different parameters sets (Maximum active set size is 3)

0.03% 0.01% 0.07%1.75% 0.69% 1.96%

98.23% 99.31% 97.97%

0.00%

20.00%

40.00%

60.00%

80.00%

100.00%

120.00%




Different parameters sets

Perc

enta

ge

Acting 3 radio link case in thissimulation loopActing 2 radio link case in thissimulation loopActing 1 radio link case in thissimulation loop

Simulation result of different parameter sets of “Window-average algorithm” (AS=3)

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Percentage of acting different radio links case with different parameters sets (Maximum active set size is 2)

0.83% 1.03% 3.18%

99.17% 98.97% 96.82%

0.00%

20.00%

40.00%

60.00%

80.00%

100.00%

120.00%




Differnt parameters sets

Perc

enta

ge (%

)

Acting 2 radio link case in thissimulation loopActing 1 radio link case in thissimulation loop

Comparison Table of successful call and drop call (Maximum active set size is 2)

79.19% 81.65% 80.95%

20.81% 18.35% 19.05%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%




Different parameters sets

Perc

ennt

age

(%)

Calls ended normallyNr. of quality failures

Simulation result of different parameter sets of “Window-average algorithm” (AS=2)

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Conclusion:

• The performance is a little better when the active set size is 2

• In most time of the call procedure, the communication between the MS and BS only using one radio link

• It’s difficult for find the optimal parameters set for the “Window-average” algorithm, we have to try a lot of parameters sets to get one better solution for the “Window-average” algorithm

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Performance study for different algorithms--- “Real-time” algorithm simulation result

Successful call rate vs. drop call rate (Real-time algorithm)

99.11% 100.00%

0.89% 0.00%0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

100.00%

AS=3 AS=2

Maximum Active set size

perc

enta

ge(%

)

Calls ended normallyNr. of quality fail calls

Percentage of acting radio links in the simulation loop(Real-time algorithm)

4.09%8.62% 11.76%

87.29% 88.24%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

100.00%

AS=3 AS=2


Perc

enta

ge(%


Simulation result of “Real-time” algorithm

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Performance study for different algorithms--- “comparison between two algorithms

Conclusion:

• The “Real-time” algorithm is better than “Window-average” algorithm

• The “Real-time” algorithm always adopt the better channel for the conversation. But the “window-average” algorithm need some average window to adopt the optimal link

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Drop call trace tool

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Drop call Trace tool--- Network drop call situation in Time 510

Relatioinship between Base Station SIR and Drop call

0 0 0 0 0 0 00 0 0 0 0 0 001

2

01

0 0

-10.0525

-8.06245

-11.0327

-3.01484

-8.51664-7.44165

-10.1732-12

-10

-8

-6

-4

-2

0

2

4

The 0Base

station

The 1Base

station

The 2Base

station

The 3Base

station

The 4Base

station

The 5Base

station

The 6Base

station

Base station

Rx

valu

e (d

B)

Val

ue

Dro

p ca

ll N

r.

The drop call in SHO with 3AS The drop call in SHO with 2ASThe drop call in SHO with 1AS The Base station's average SIR

Time:510

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Relationship between Base Station and Drop call

0 0 0 0 0 0 00 0 0 0 0 0 00 1 20

20 0

-6.78302 -6.90614

-11.7081

-5.74579

-14.02674

-9.8939

-29.3006-35

-30

-25

-20

-15

-10

-5

0

5

The 0Base

station

The 1Base

station

The 2Base

station

The 3Base

station

The 4Base

station

The 5Base

station

The 6Base

station

Base station

Rx

valu

e (d

B)

Val

ue

Drop

cal

l Nr.

The drop call in SHO with 3AS The drop call in SHO with 2ASThe drop call in SHO with 1AS The Base station's average SIR

Time:520

Drop call Trace tool--- Network drop call situation in Time 520

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Future Work

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Future work

• More simulations with different parameters set are needed

• The Packet data service performance with different SHO algorithms is need to be investigated

• More drop call trace analysis tool need to be integrated in NETSIM

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Thank you!

Questions?

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