Dynamic Topology Construction in Bluetooth Scatternets

•Mukesh Kumar : Dept. of CSE, I.T.B.H.U, Varanasi

•Navin K Sharma : Computer Associates, Hyderabad

•Rajarshi Roy : Dept. of ECE, IIT Kharagpur

•Shamik Sural : School of IT, IIT Kharagpur

Introduction

• Bluetooth Technology

• Piconet and Scatternet

• Master, Slave and Bridge

• Frequency Hopping

• Synchronization with Master

• Power Constraint

• Scatternet Formation Algorithms: Bluetooth Topology Construction Protocol (BTCP), Distributed Tree Scatternet Formation Protocol (DTSFP), Bluetree and Bluenet Protocol, etc.

Continued…….

• Few Commonalities : -> Assumption of a leader election process -> Topology optimization starting with a fixed set of Bluetooth nodes -> Deferring the problem of topology reconstruction as a future extension -> Approach the topology construction problem as a stand-alone problem and not as an outcome of specified properties of Bluetooth nodes

• Dynamic Topology Construction : -> Bottom up Approach -> Dynamic approach instead of one-time stand alone approach -> Topology formation specific properties integrated with the normal operations of Bluetooth nodes -> A practical approach

Dynamic Topology Construction Algorithm

• Attempts to form fully connected and balanced network

• Fault Tolerant Network

• Four roles are defined:

-> Isolated (I)

-> Master (M)

-> Slave (S)

-> Bridge (B)

• The complete algorithm consists of five routines:

-> Start-Up Routine (SUR)

-> Next State Routine (NSR)

-> Piconet Formation and Modification Routine (PFMR)

-> Scatternet Formation and Modification Routine (SFMR)

-> Normal Communication Routine (NCR)

Continued….

• Each routine resides within every Bluetooth device and gets called depending on the current role of the device and discovery of other devices.

• Certain Terminologies used for smooth progression of algorithm:

-> PI : probability with which an isolated node goes to Inquiry state

-> PM : probability with which a master goes to Inquiry state

-> TI : time for which a node will stay in Inquiry state

-> TIS : time for which a node will stay in Inquiry Scan state

-> P(i) : Piconet containing node i

-> B(i,j) : Bridge node between two piconets having node i and j as their

master

-> NBS(i) : Total no. of non bridge slaves of the piconet whose master is i.

-> n(i) : Total no. of slaves of the piconet whose master is i.

-> F(mi,pi) : A function of the memory ‘m’ and power ‘p’ of a node i.

Start-up Routine(SUR)

Node (i) starts (isolated node)

Call Next-State Routine(Isolated)

State=I or I-S ?Stay in Inquiry for

TI to latch with another node

If State = I

Is j isolated

Call PFMR(I,I)

Node I receives message from

node j

yes

n(j) = no. of nodes in the piconet to which j belongs

Is j Master

Is n(j) = 7

yes

noIs n(j) = 7

Call SFMR(I,M)

Call PFMR(I,M)

Call SFMR(I,S)

Call PFMR(I,S) no

yes

no

yes

Stay in I-Scan for TIS to latch with

another node

Node I receives message from

node j

Call PFMR or SFMR based on

role of j (as discussed in other part of flow chart

If State=I-Scan

Piconet Formation and Modification Routine (PFMR)

Node_role_i = M && Node_role_j = M

Is F(mi,pi) >= F(mj,pj)

Merge P(i) and P(j)Node_role_i = MNode_role_j = S

Node_role_B(i,j) = S

Node i calls NCR(M)Node j calls NCR(S)

Node B(i,j) calls NCR(S)

Similar to other part with roles of i

and j reversed

yes

no

A Master detects Master of another Piconet with a total of less than 7 slaves

IsolatedNode

(Inquiry)

IsolatedNode

(I-Scan)

M 1

S 1

M 2

S 2

S 3

S 4

S 1

S 2

S 4

M 2

S 5

S 3

Scatternet Formation and Modification Routine (SFMR)

Node_role_i = M && Node_role_j = M

Is ((n(i)=7 && NBS(i) =0) OR (n(j)=7 && NBS(j)=0))

Node i calls NCR(M)Node j calls NCR(M)

yesnoIs B(i,j) exists

Is n(i)+n(j) = 7 Call PFMR(M,M)

Is n(i) >= n(j) && NBS(i) >=0)

n = (n(i)-n(j))/2

Is NBS(i) >= nn non-bridge

slaves from P(i) join P(j)

NBS(i) non-bridge slaves from P(i)

join P(j)

yes

yes

no

yes

yes

no

Transfer non-bridge slaves from P(j) to P(i) similar

to other part

no

Assign slave k with maximum F(mi,pi) from P(i) and P(j) as B(i,j)

no

Non-bridge slaves join P(j) from P(i) OR join P(i) from P(j) in

similar fashion

Both i and j broadcast new piconet structure to their slaves.

Node i calls NCR(M)Node j calls NCR(M)

A Master detects Master of another Piconet with a total of 7 to 13 slaves

M 1

S 1

S 2M 2

S 4

S 3

S 6

S 5

S 7

M 1S 5S 1

S 2

M 2

S 3

S 6

S 4

S 7

M 3S 8

S 9

S 10

M 1

S 5

S 1

S 2

M 2

S 3

S 6

S 4

S 7

M 1 S 5S 1

S 2M 2

S 3

S 6

S 4

S 7

M 3

S 8

S 9S 10

M 1 S 5S 1

S 2M 2

S 3

S 6

S 4

S 7

M 3

S 8

S 9S 10

M 4 S 11

M 1

S 5S 1

S 2M 2

S 3

S 6

S 4

S 7

M 3

S 8

S 9S 10

S 11

S 12

Simulation Results

0

2

4

6

8

1 6 11 16 21 26 31No. of Devices

Av

g n

o. o

f sl

ave

s p

er p

ico

net

Avg no of slaves per piconetIdeal Avg no of slaves

0

2

4

6

8

1 9 15 17 22 27 31No. of devices

No.

of

pic

onet

s

No of piconets Ideal no of piconets

0

2

4

5 15 25 31 33 35

No. of devices

Avg

inte

r pi

cone

t ro

utin

g de

lay

0

500

10001500

2000

2500

2 10 20 30No. of Devices

Iso

late

d n

od

e

co

nn

ecti

on

dela

y (

ms)

Conclusions and Future Scope

• This algorithm address a dynamic scenario

• Balanced and minimum hope connectivity

• Minimize inter piconet communication delay

• No need of leader election

• Distributed and fault tolerant

• Very low computational cost

• An efficient scheduling and routing algorithm can be incorporated

References

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• B. A. Miller, C. Bisdikian, Bluetooth Revealed: The Insider's Guide to an Open Specification for Global Wireless Communications, Prentice Hall, USA, 2000.

• J. Haartsen, Bluetooth - the universal radio interface for ad-hoc, wireless connectivity, Ericsson Review, 3 (1998) 110–117.

• T. Salonidis, P. Bhagwat, L. Tassiulas, R. LaMaire, Distributed topology construction of Bluetooth personal area networks, Proc. Infocom (2001).

• G. Miklos, A. Racz, Z. Turanyi, A. Valko, P. Johansson, Performance aspects of Bluetooth scatternet formation, Proc. The First Annual Workshop on Mobile Ad-hoc Networking and Computing, (2000) 147-148.

• G. Tan, Self-organizing Bluetooth scatternets, Master’s thesis, Massachusetts Institute of Technology, January 2002.

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• S. Basagni, C. Petrioli, Multihop Scatternet Formation for Bluetooth Networks, Proc. VTC (2002) 424-428.• J. Yun, J. Kim, Y-S Kim, J.S. Ma, A three-phase ad-hoc network formation protocol for Bluetooth Systems,

The 5th International Symposium on Wireless Personal Multimedia Communications, (2002) 213 –217.• S.Basagni, R.Bruno, A Petrioli, A Performance Comparison of Scatternet Formation Protocols for Networks of

Bluetooth Devices, IEEE International Conference on Pervasive Computing and Communications (PerCom’03) (2003) 341-350.

• R. Guerin, J. Rank, S. Sarkar, E. Vergetis, Forming Connected Topologies in Bluetooth Adhoc Networks, International Teletraffic Congress (ITC18), Berlin, Germany (2003).

• M. A. Marsan, C. F. Chiasserini, A. Nucci, G. Carello, L. De Giovanni, Optimizing the Topology of Bluetooth Wireless Personal Area Networks, Proc. Infocom (2002).

• R. Roy, M. Kumar, N.K. Sharma, S. Sural, P3-A Power-aware Polling Scheme with Priority for Bluetooth. Proc. International Conf. on Parallel Processing (ICPP) Workshops, 2004, Montreal, Canada (to appear).