efficient peer-to-peer communications in bluetooth younsuk kim, kyunghun jang, kyunhyon tchah ieice...

Efficient Peer-to-Peer Communications in Bluetooth

YounSuk KIM , KyungHun JANG , KyunHyon TCHAH

IEICE TRANS. COMMUN.

speaker ： jenchi

Outline

Introduction Master-Slave Switching Mechanism Dynamic Master Selection and Fast Master-Slave Switching Policies Simulation Conclusion

Introduction

Piconet Communication

master ： send packets in even slots slave ： send packets in odd slots point-to-point or point-to-multipoint

slaves can’t communicate directly with each other

Introduction (cont.)

Peer-to-peer communication A slave can communicate with other

slaves as well as a master But there is NO destination address

field in the packet header sent by a slave

Master-Slave Switching Mechanism

Take place when a slave wants to become a master Tx and Rx timing is reversed Redefinition of the piconet ： piconet

switch

Master-Slave Switching Mechanism (cont.)

Unit 1(Old Master)

Unit 2(New Master)

Unit 3(Slave)

Unit 4(Slave)

Master-Slave Switch request

Master-Slave Switch response

Time alignment LMP message

FHS packet

FHS acknowledgement


FHS packet

FHS acknowledgement


FHS packet

FHS acknowledgement

POLL

POLL

Old

hoppin

g

sequen

ce

New hopping sequence

Dynamic Master Selection and Fast Master-Slave Switching Policies

Why Dynamic Master Selection ？

Therefore, Dynamic master selection policy is needed in order to minimize the average slot occupancy per packet

The switching is accomplished as fast as possible

Master

Piconet

S1S2

θθ

θ

S1→M→S2 ： 2θS1→S2 ： θ

Dynamic Master Selection and Fast Master-Slave Switching Policies (cont.)

Three policies Addressing policy Dynamic Master Selection Policy Fast Master-Slave Switching Mechanism

The Motivation of Addressing Policy Each slave is assigned a 3 bits AM_ADDR

(Active Member Address) by a master

The AM_ADDR of the slave is used both in the master-to-slave and in the slave-to-master packets

There is no destination address field in the packet header sent by a slave


-- Addressing Policy

Header format

AM_ADDR TYPE FLOW ARQN SEQN HEC3 4 1 1 1 8


-- Addressing Policy

Addressing rules AM_ADDR

master ：“ 111” slaves ：“ 001”~“110” Broadcasing packet ：” 000”

The AM_ADDR field is used only for destination address

A 3-bits SRC-ADDR (source address) field Carries the AM_ADDR of the source unit

Bluetooth packet format with an added field in payload

Access Code Header72 54 3 0-2745 bits

SRC-ADDR Payload


-- Dynamic Master Selection Policy

Θi occupancy parameter related with slaves’ or

master’s address by the number of the occupied slots ,where i=1,2,…7

When a master receivers a packet It increases θi=SRC

If received packet should be forward ， it increases θi=DTS

If not ， it increases θi=Master

When the master transmits a packet of which source address is its own It increases θi=Master and θi=DTS


-- Dynamic Master Selection Policy

Rx Tx

i=src_addr of received packet

=occupied slots of received packet

Forwarding packet ？

j=dst_addr of received packet

θi← θi ＋△θj← θj ＋△

Tx

θi← θi ＋△θmaster← θmaster ＋△

Tx

Yes

No

i=dst_addr of transmitting packet

Forwarding packet ？

masterNEW ＝ argk maxθkθi← θi ＋△

θmaster← θmaster ＋△

No

Yes

masterNew== mastercurrent

Change master

Rx

Yes No


-- Fast Master-Slave Switching Mechanism

Define an anchored master as a unit which creates a piconet a slave which takes over the master

role from the anchored master by master-slave switching

The temporary master still uses the channel parameters of the anchored master

Only TDD switching of the anchored and temporary masters


-- Fast Master-Slave Switching MechanismUnit 1

(Anchored Master)Unit 2(Slave)

Unit 3(Slave)



Updated Piconet Information


Piconet Information


Master-Slave switch response

Dynamic master selection policy

Dynamic master selection policy

Unit 2(Temporary master)


Piconet Information

Dynamic master selection policyH

oppin

g s

equ

ence

of

the a

nch

ore

d

mast

er

Simulation

A single piconet with up to six slaves The TDD slot length in Bluetooth is

equal to 625 μsec Transmits single-slot DH1 packets

every slot

Simulation (cont.)

Carrier frequency ＝ 2.4GHz Symbol rate ＝ 1M symbol per sec Modulation format ＝ non-coherent

FSK γT(SNR threshold) ＝ 15dB

Mobile speed ＝ 2km/h

Simulation (cont.)

Conclusion

Addressing policy for L2 forwarding efficient peer-to-peer communications in Bluetooth Performs better than the conventional addressing

policy Dynamic master selection policy

in order to minimize the average channel occupancy

Fast master-slave switching mechanism Minimize the switching delay

efficient peer-to-peer communications in bluetooth younsuk kim, kyunghun jang, kyunhyon tchah ieice...

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