authors: md. mohsin ali* md. amjad hossain md. kowsar...

Khulna University of Engineering & Khulna University of Engineering & Technology (KUET)Technology (KUET)

Authors:Authors:Md. Mohsin Ali*Md. Mohsin Ali*Md. Amjad HossainMd. Amjad HossainMd. Kowsar HossainMd. Kowsar HossainG. M. Mashrur-E-Elahi G. M. Mashrur-E-Elahi Md. Asadul IslamMd. Asadul Islam

www.kuet.ac.bdwww.kuet.ac.bd

IntroductionIntroduction Components of Wireless Mobile

Networks: Mobile Host (MH)

End-user device Base Station (BS)

Transmits signals to Cell Cell

Contains one BS Registration Area (RA)

Contains several Cells Mobile Switching Center (MSC)

Used for call switching Visitor Location Resister (VLR)

Distributed database Contains MH’s current Cell information

Home Location Register (HLR) Centralized database Contains MH’s current VLR information

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12th International Conference on Computer and Information Technology (ICCIT), 2009 2

Introduction (Contd.)Introduction (Contd.) Basic operations of location

management: Location update

On VLR MH move from one Cell to another one Intra-subnet handoff

On HLR MH move from one RA to another one Inter-subnet handoff

Call delivery To find out called MH

Finding out serving VLR Finding out serving Cell

Call establishment between calling and called MHs Location server’s load

On VLR Depends on frequency of call forwarded to its RA Relatively low load

On HLR Depends on total call generation in the whole network Relatively high load

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312th International Conference on Computer and Information Technology (ICCIT), 2009

Related WorkRelated Work Basic IS-41 scheme Centralized database scheme Hashing and caching scheme

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Related Work (Contd.)Related Work (Contd.) Basic IS-41 scheme

Centralized HLR Distributed VLR No VLR cache Query on HLR for every call

Centralized database scheme Centralized HLR Distributed VLR But, VLR cache Cache is replicated where more call is generated For each call delivery

Query on cache at first for called MH: if cache hit, then call is established

Otherwise query on HLR for that No cache update

For each call receiving No cache update

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Related Work (Contd.)Related Work (Contd.) Hashing and caching scheme

Distributed HLR With identical replicated database

Distributed VLR VLR cache All VLR own caches For each call delivery


Otherwise query on HLR (selected by hashing function) for that

Cache update Calling MH’s cache is updated with called MH’s ID

For each call receiving No cache update

One call, one location update in cache22/12/2009

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Proposed MethodProposed Method New hashing and caching approach

Distributed HLR With identical replicated database

Distributed VLR VLR cache All VLR own caches For each call delivery


Otherwise query on HLR (selected by hashing function) for that

Cache update Calling MH’s cache is updated with called MH’s ID

For each call receiving Cache update

Called MH’s cache is updated with calling MH’s ID One call, two location updates in cache

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Proposed Method (Contd.)Proposed Method (Contd.) Hashing Function

SERVERID = f (MHID, VLRID, m) = (MHID + VLRID) mod m

Used to select one of m HLRs Distributes HLR’s load to m HLRs

Handoff Select new SERVERID for new location MH’s new location is updated to that server Multicasts this to remaining (m - 1) HLRs

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Proposed Method (Contd.)Proposed Method (Contd.)

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9

Yes

Yes

No

YesCache hit?

No

MH’s location

information in cache?

Call receiving

Update or save MH’s location information in

cache

Call established

Come back to that location server

Handoff

Call arrival

No

Start

No

MH’s location

information in

cache?

Select new location server for MHs new

location using hashing function

MHs new location information is updated

in that new server

This server multicasts this information to

remaining m-1 location servers

Call arrival, or receiving or handoff?

Yes

Cache hit?

Find MHs location from server selected by

hashing function

Go to VLR containing the address of called MH

Fig. 4. Flow chart of the proposed method.


Analytical ModelAnalytical Model Call delivery cost

Basic IS-41 schemeDatabase access cost

Calling VLR (Dv), HLR (Dh), called VLR (Dv) Total access cost = 2Dv + Dh

Signaling cost Two signaling between calling VLR and HLR (2Ch) Two signaling between HLR and called VLR (2Ch), One signaling between calling VLR and called

VLR (Cv). Total signaling cost = 4Ch + Cv

Total call delivery cost, Cb = 4Ch+ Cv+2Dv + Dh

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Ch Ch

Ch Ch

Cv

HLR

Calling VLR Called VLR

Fig. 5. Access and signaling costs

Analytical Model (Contd.)Analytical Model (Contd.) Call delivery cost (Contd.)

Hashing and caching scheme Let

q = Probability that the location information is in the cache p = Cache hit ratio Cch = Average call delivery cost if the location information is in the

cache λ = Mean call arrival rate λmax= Maximum call arrival rate

µm = Mean mobility rate Cache access and update cost is negligible

Average call delivery cost, Where

p =

q =

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Cc =q∗Cch+(1−q )∗Cb

Cch=p∗Cv +(1− p)∗(C v +Cb )

λ( λ+μm)

λλmax

Analytical Model (Contd.)Analytical Model (Contd.) Call delivery cost (Contd.)

New hashing and caching scheme (Proposed) Also let

λr = Mean call receiving rate

= Maximum call receiving rate

Average call delivery cost, , but it is different from hashing and caching scheme with respect to q and p

Where

Cch = same as that of hashing and caching scheme

p = if λr = λ, then p =

q = if λr = λ and , then

q =

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Ccr =Cc =q∗C ch+(1−q)∗Cb

λ∗( λr+1)

{λ∗( λr+1 )+μm }

λλmax

+(1−λ

λmax

)∗λr

λrmax

λrmax

λ2+λ

( λ2+λ+μm)

λrmax=λmax

2λλmax

−λ2

λmax2

Analytical Model (Contd.)Analytical Model (Contd.) Location server’s load

Basic IS-41 schemeOne location server (HLR) Call arrival time are independent and

exponentially distributed with parameter λ Service time are also exponentially distributed Modeled as M/M/1 queuing system So, system throughput is equal to λ

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Analytical Model (Contd.)Analytical Model (Contd.) Location server’s load (Contd.)

Hashing and caching scheme m location servers (HLR) Also let

xc = Throughput of anyone of the m location servers

λs = Call arrival rate at serveri, i = 1, 2, … , m

= Probability of querying to serveri

.

Each server is selected uniformly, so

Modeled as m number of M/M/1 queuing system

• Throughput of location server, serveri,

, where

q = 22/12/2009

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pr i

pr i=

1m

λs =λ∗pr i∗(1−q)

xc =λs =λ∗1−q

mλ

λmax

Analytical Model (Contd.)Analytical Model (Contd.) Location server’s load (Contd.)

New hashing and caching scheme (Proposed)Throughput of location server, serveri,

, where

q = if λr = λ and , then

q =

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xc =λs =λ∗1−q

mλ

λmax

+(1−λ

λmax

)∗λr

λrmax

λrmax=λmax

2λλmax

−λ2

λmax2

Experimental ResultsExperimental Results Average call delivery cost

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Fig. 6. Performance comparison of basic IS-41, hashing and caching and proposed schemes based on average call delivery cost.

Experimental Results (Contd.)Experimental Results (Contd.) Location server’s load

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Fig. 7. Performance comparison of basic IS-41, hashing and caching and proposed schemes based on location server’s load.

ConclusionConclusion One call, two location updates in cache

in new proposed method During call delivery and receiving

But, one call one location update in cache in most recent previous method During call delivery time only

So, The more call, the more cache update The more cache update, the higher

values of p and q The higher values of p and q, the lower

values of call delivery cost and location server’s load

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Future WorkFuture Work More appropriate hashing function

Location server’s load and congestion minimization

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ReferencesReferences EIA/TIA. “Cellular radio-telecommunications intersystem operations,” Tech. Rep. IS-

41 Revision B, EIA/TIA, December 1991. M. Mouly and M.B. Pautet, “The GSM system for mobile communications,” 49 rue

Louise Bruneau, Palaiseau, France, Telecom Publishing, January 1992. Chang Woo Pyo, Jie Li, Hisao Kameda, and Xiaohua Jia, “Dynamic Location

Management with Caching in Hierarchical Databases for Mobile Networks,” DNIS 2002, LNCS 2544, Springer-Verlag, vol. 2544, pp. 253–267, Berlin/Heidelberg, December 2002.

Weiping He and Athman Bouguettaya, “Using Hashing and Caching for Location Management in Wireless Mobile Systems,” MDM 2003, LNCS 2574, Springer-Verlag, vol. 2574, pp. 335–339, Berlin/Heidelberg, January 2003.

I. Akyildiz, J. McNair, J. Ho, H. Uzunalioglu, and W. Wang, “Mobility management in next-generation wireless systems,” In Proceedings of the IEEE, vol. 87, no. 8, pp. 1347–1384, August 1999.

Y. Bejerano and I. Cidon, “An efficient mobility management strategy for personal communication systems,” In The Fourth Annual ACM/IEEE International Conference on Mobile Computing and Networking, ACM Publishers, pp. 215-222, Dallas, Texas, United States, October 1998.

A. Bouguettaya, “On the construction of mobile database management systems,” In The Australian Workshop on Mobile Computing & Databases & Applications, Melbourne, Australia, February 1996.

E. Pitoura and G. Samaras, “Data Management for Mobile Computing,” vol. 10, Kluwer Academic Publishers, 1998.

R. Prakash and M. Singhal, “Dynamic hashing + quorum = efficient location management for mobile computing systems,” In Proceedings of the Sixteenth Annual ACM Symposium on Principles of Distributed Computing, ACM Press Publisher, pp. 291, August 1997.

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Thank you very muchThank you very much

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authors: md. mohsin ali* md. amjad hossain md. kowsar...

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