Broadband Wireless Communication and Multimedia Laboratory, Tongji University Lianhai Shan

第（ 1）页 http://WM.tongji.edu.cn

Predictive Group Handover Scheme with Sub-Channel Borrowing for IEEE 802.16j-

enabled Vehicular Networks

Broadband Wireless Communication and Multimedia Laboratory,

Tongji UniversityLianhai Shan

[email protected]


Outline

• Features of Group Handover and Problems Statement

• Proposed Scheme: PGHO-CB

• Performance Analysis

• Simulation Scenario and Result Analysis

• Conclusion and Future Work


Mobile RS Application Scenario

Relay Station:

Enhance the signal strength

Extend the coverage


Group Handover Scenario

Backbone networks

Mobile RS

Mobile direction

Internet

…

MS1

MS3MS2

MS

MSMS

Serving BS Target BS

Broadband Wireless Access using IEEE802.16j for Mobile Multi-hop WiMAX

SINR of a neighbor BS is larger than the current serving BS, (the hysteresis margin, threshold), then the handover of group users will happen.


Problems for Group Users

• Heavy burden for BS

• Long system delay in the GHO process

• Handover dropping probability


Outline

• Features of Group Handover Problems Statement

• Proposed Scheme: PGHO-CB





GHO Flow Chart

Scanning neighboring BSs, get the optimal BS(＃B) as the target BS according to the acquired location and mobile information, target BS get the detailed information of MSs and prepare the resources

Mobile RS MR-BS #A(serving)

MR-BS #C(candidate)

MR-BS #B(candidate/target)

MOB_SCN-REQ

MOB_SCN-RSP

MR_NBR-INFO

Association

BS_ID= BS#B)

(Recommended BS= BS #B)

MOB_RSHO-REQ

MOB_RSHO-RSP

MOB_RSHO-IND(Time= L frames)

RNG_RS-REQ

RNG_RS-RSP (New CID for MS#1…MS#n)

Normal Operation and Data Transfer

Serving BS realease

Resource R

etain Tim

er

Network reentry after HOHandover Delay time

RS calculates the position information, compares it with the position report database and get the exact position and mobile direction in certain time

MS#1… #n

in Mobile RS

MOB_NBR-ADV

MOB_SCN-REQ

MS_SCN-INF

MS_SCN-ACK

MOB_SCN-RSP

Handover Calls Admission Control(HO Pre-notification Process for MS#1…MS#n through Backbone )

MOB_MSHO-REQ

MOB_BSHO-RSP

MOB_HO-IND(Time= L frames)

RNG-REQ

RNG-RSP

Serving BS realease

MOB_MSHO-REQ

MOB_BSHO-RSP

…

Can be Omitted by GHO

T1

T2

T3


Proposed Scheme

Predictive Group Handover (PGHO)• Location and moving direction information

Channel Borrowing (CB)• Borrowing Channels from the existing service in the target BS

by decreasing the QoS level.

PGHO-CB: Predictive Group Handover with sub-channel borrowing


Proposed Scheme

Mobile directionserving BS ID, average dwelling time,

next target BS ID Count

On route (ID_1, T100, ID_3) 22

On route (ID_1, T60, ID_4) 5

On route …… …

Return route (ID_8, T80, ID_6) 20

Return route (ID_8, T120, ID_7) 4

Return route … …

Movement History Database

Large vehicles moving routes is fixed such as light rails, subways.


Proposed Scheme• Erlang-B formula reversely to estimate the number of sub-

channel required

),(

!)(

!)(

0

MTf

iT

MT

PM

i

i

M

),( _Re RRqR MBfP

),( _Re NNqN MBfP

avbreqbor BBB Result:

NP: CBP of nrtPS in a BS;

: CBP of rtPS in a BS;RP

reqB is the number of sub-channels needed for the coming GHO

avbB is available sub-channels in the target BS


Proposed Scheme• Sub-Channel Borrowing (CB) for PGHO

Detailed CB is within my published papers, will appear in LNCS of Apweb’09.


Outline


• Proposed Scheme





Single Handover Model0,0

X,Y

1,1

0,N

0,T

0,1

M,0S,01,0hoRnR __

hoN

nN

__

hoRnR __ hoRnR __ hoR _hoR _

RR )(2 RR )( RRS ))(1( RRS )( RRM

NN

hoN

nN

__

)(2

NN

hoN

nN

__

)(2

NN

hoN

_

))(1

(N

NT

hoN

_

)(

NN

N

hoRnR __

RR

hoN

nN

__

NN

hoRnR __

)( RRX

hoRnR __

)( RR

hoRnR __

)(2 RR

hoN

nN

__

)(2

NN

hoN

nN

__

)(

NN

Y

NR

RN

R

R

N

R

bbXBY

bbYBX

bBN

bBM

bBT

bBS

/*

/*

/

/

/

/

min_

min_

2-D Markov state transition diagram


Single Handover • New calls blocking probability (CBP) of rtPS and nrtPS

• handover blocking probability (HBP) of rtPS and nrtPS

rtPS

nrtPS

rtPS

nrtPS


Proposed Group Handover

Markov transition diagram for a Single MS using PGHO scheme

0,0,0

X,Y,0

1,1,0

0,N,0

0,T,0

0,1,0

M,0,0S,0,01,0,0shoRsnR __

sho

Nsn

N_

_

shoR _

RR )(2 RR )( RRS ))(1( RRS )( RRM

NN

)

(2N

N

)(2

NN

sho

N_

))(1

(N

NT

sho

N_

)(

NN

N

shoRsnR __

RR

NN

shoRsnR __

)( RRX

shoRsnR __

)( RR

shoRsnR __

)(2 RR

)(2

NN

sho

Nsn

N_

_

)

(N

NY

min_min_

min_min_

min_

min_

min_

min_

/)*(

/)*(

/)(

/)(

/)(

/)(

NRg

RNg

Ng

Rg

Nrevg

Rrevg

bbXBBY

bbYBBX

bBBN

bBBM

bBBBT

bBBBS

shoRsnR __ shoRsnR __ shoR _

sho

Nsn

N_

_

sho

Nsn

N_

_

sho

Nsn

N_

_

sho

Nsn

N_

_

0,0,1

Xk,Yk,1

k,k,1

0,Nk,1

0,Tk,1

0,k,1

Mk,0,1Sk,0,1k,0,1ghoRgnR __

gho

Ngn

N_

_

ghoR _

)( RRk )(2 RRk )( RRSk )()1( RRkS )( RRMk

)(

NN

h

)(

2N

Nk

)

(N

NTk

gho

N_

)(

)1(

NN

kT

gho

N_

)(

NN

Nk

)( RRk

)(

NN

h

shoRsnR __

)( RRXk

shoRsnR __

)( RRk

)(2 RRk

)(

2N

Nk

sho

Nsn

N_

_

)(

NN

Yk

min_min_

min_min_

min_

min_

min_

min_

/)*(

/)*(

/)(

/)(

/)(

/)(

NRs

RNs

Ns

Rs

Nrevs

Rrevs

bbXkBBYk

bbYkBBXk

bBBNk

bBBMk

bBBBTk

bBBBSk

gho

Ngn

N_

_

gho

Ngn

N_

_

sho

Nsn

N_

_

gho

Ngn

N_

_

ghoRgnR __ ghoRgnR __ ghoR _

ghoRgnR __ ghoRgnR __

Markov transition diagram for a Group MSs using PGHO scheme



''_

'_ ),(),(

_ )1,,()0,,(nRRSRSnRBSBS Cji

RSRSRSCji

BSBSBSnR jipjipP

}|),{('_ RrevNRSRRSNBSRBSnR bBBbjbibjbijiC

}|),{(''_ RrevNRSRRSNBSRBSnR kbBBbjbibjbijiC

''

_'

_ ),(),(_ )1,,()0,,(

nNRSRSnNBSBS CjiRSRSRS

CjiBSBSBSnN jipjipP

}|),{('_ NrevNRSRRSNBSRBSnN bBBbjbibjbijiC

}|),{(''_ NrevNRSRRSNBSRBSnN kbBBbjbibjbijiC

• New calls blocking probability (CBP) of rtPS and nrtPS



''_

'_ ),(),(

_ )1,,()0,,(hoRRSRShoRBSBS Cji

RSRSRSCji

BSBSBShoR jipjipP

}|),{( min_min_min_min_min_'

_ RNRSRRSNBSRBShoR bBbjbibjbijiC

}|),{( min_min_min_min_min_''_ RNRSRRSNBSRBShoR kbBbjbibjbijiC

''

_'

_ ),(),(_ )1,,()0,,(

hoNRSRShoNBSBS CjiRSRSRS

CjiBSBSBShoN jipjipP

}|),{( min_min_min_min_min_'

_ NNRSRRSNBSRBShoN bBbjbibjbijiC

}|),{( min_min_min_min_min_''

_ NNRSRRSNBSRBShoN kbBbjbibjbijiC

• handover blocking probability (HBP) of rtPS and nrtPS


Adaptive HO CAC Delay

• : represents the handover CAC adaptive factor

• : represents exponential factor, decided by the different service types

• : the highest speed

• : the largest handover CAC delay time

• : the least handover CAC delay time as

nvvdelayCAC etttT ))(( 1/

minmaxmax_max

max/ vvr

n

maxv

maxt

mint


HO Dropping under Different Velocity

: HBP in the handover CAC process

: the time of handover CAC process of each time

: practical delay of handover CAC process

)1/( _'

_ failnegocacdelayCAC RTT

failnegoR _

cacT

'_ delayCACT

delayCACdelayCAC TT _'

_ If , handover QoS will reduce

max'

_ tT delayCAC If , handover dropping will happen

the longest handover CAC delay that can ensure the connection maxt


Outline


• Proposed Scheme





Simulation Parameterparameters value

Number of Cells 19

Operating Frequency 2500MHz

Duplex TDD

System Channel Bandwidth 10MHz

BS Height 32 meters

Mobile Terminal Height 1.5 meters

BS Antenna Gain 15 dBi

MS Antenna Gain -1 dBi

BS Maximum Power Amplifier Power 43 dBm

Thermal Noise -174 dBm/Hz

Sampling Frequency 11.2MHz

FFT Size (NFFT) 1024

Sub-Carrier Frequency spacing 10.94kHz

Frame Duration(TTI) 5 milliseconds

Number of OFDMA Symbols 48

Propagation Model COST231-Hata


Simulation Parameter

parameters valueNumber of Channels 30

Dwelling time 0.5

Call completion rate = 0.5

new call arrival rates of rtPS

new call arrival rates of nrtPS

System traffic load

channel number of one rtPS (min-max) 2-4

channel number of one nrtPS (min-max) 1-3

radius of BS coverage 1.28 km


New calls and HO blocking probability

0 2 4 6 8 10 12 140

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Traffic load (new calls/min)

Ne

w c

all

blo

ckin

g p

rob

ab

ility

of s

yste

m

Average user number in a MRS equels 3

nrtPS with SHO scheme

rtPS with SHO scheme

nrtPS with GHO scheme

rtPS with GHO scheme

0 2 4 6 8 10 12 140

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Traffic load (new calls/min)

Ha

nd

ove

r b

lock

ing

pro

ba

bili

ty o

f sys

tem

Average user number in a MRS equels 3

nrtPS with SHO scheme

rtPS with SHO scheme

nrtPS with GHO scheme

rtPS with GHO scheme


Handover dropping probability

20 40 60 80 100 1200

5

10

15

20

25

Mobile RS velocity(km/h)

Ave

rag

e h

an

do

ver

dro

pp

ing

pro

ba

bili

ty(%

) Traffic load equals 6 and average user number in a MRS equels 5

rtPS(SHO scheme)

nrtPS(SHO scheme)

rtPS(GHO scheme)

nrtPS(GHO scheme)


Average handover delay

20 40 60 80 100 120

45

50

55

60

65

70

75

Mobile RS velocity(km/h)

Ave

rag

e h

an

do

ver

de

lay

in M

RS

(ms) Traffic load equals 6 and average user number in a MRS equels 5

rtPS(SHO scheme)

nrtPS(SHO scheme)rtPS(GHO scheme)

nrtPS(GHOscheme)


Outline


• Proposed Scheme





Conclusion

• PGHO-CB predict the target BS for mobile RS

• Target BS prepare the needed resource for HO using the Sub-Channel Borrowing

• Decrease the HDP significantly of group handover


Future Work

• Two-level Channel Reallocation for Group Handover after Sub-channel Borrowing

• System Performance of GHO


ThanksQ&A

Broadband Wireless Communication and Multimedia Laboratory, Tongji University Lianhai Shan

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