BLUETOOTH THROUGHPUT IMPROVEMENT USING A SLAVE TO SLAVE PICONET FORMATION

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BLUETOOTH THROUGHPUT IMPROVEMENT USING A SLAVE TO
SLAVE PICONET FORMATION
By Christophe Lafon and Tariq S Durrani
Institute for Communications Signal
Processing Dept. of Electronic Electrical
Engineering University of Strathclyde Glasgow - UK
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OVERVIEW

• Project Aim Current Work Objective.
• Background
• Slave to Slave Piconet Formation Overview.
• Switching Piconet
• Clock Synchronization.
• Frequency Hopping Sequence.
• Simulation results.
• Conclusion and Further Work.

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MOTIVATION OF WORK

• AIM New approach to inter-Piconet communication
• New policy SSPF (Slave to Slave Piconet
  Formation).
• OBJECTIVES To achieve faster jumps between
  different Piconets.

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BLUETOOTH BACKGROUND

• Operates in the 2.4 GHz unlicensed ISM band.
• 79 hop frequencies f 2402k MHz, k 0,..78.
• Bandwidth 1Mb/sec with Fast hopping 1600 hops/s
• Access Code AM_ADDR 3 bits to units to
  distinguish between Slave unit participating in
  the Piconet (7 max).
• Channel divided into time slot 625?s length
• The Package is transmitted in 1, 3 or 5 Slots

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TIME DIVISION DUPLEX (TDD) TRAFFIC BETWEEN TWO
SLAVES
S1
S3
S4
MASTER
S2
Slots Traffic between Master and Slaves
Master
Slave 1
Slave 2
Slave 3
Slave 4
time
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ALTERNATIVE APPROACH BOTH SLAVES ENTER NEW
PICONET

• Slave will indicate to Master of an important
  data transfer to another Slave.
• Payload header
• 1 for high traffic
• 0 for low traffic
• Both Slaves will then enter in new mode Slave to
  Slave Piconet Formation (SSPF).

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SWITCHING PICONETS

• GOAL To eliminate requirement of guard time
  within traffic between two Piconets.
• Clock Synchronization (Slot misalignment).
• Hopping Sequence (Channel Synchronisation).
• Meeting time (Synchronize both piconet).

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CLOCK SYNCHRONISATION

• Each Device has a Native Clock (CLKN).
• A Piconet is characterized by Master
• Frequency Hopping Scheme
• Access code (AM_ADDR)
• Timing synchronization (CLK)
• Master determines the bit rate allocated to each
  slave
• Slaves do not synchronize to the master
• Calculate offsets to masters Bluetooth Clock
  CLK.
• Monitor timing drift

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SSPF CLOCK SYNCHRONISATION

• The new Piconet Clock will not be synchronized
  with Master(2) Native Clock, but with Master(2)
  Estimate Clock of Master(1).
• Both Piconets will be synchronized according to
  the initial Master(1).
• Master(2) will synchronize to Master(1) with a
  rendezvous time.

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MEETING TIME TO AVOID CLOCK DRIFT

• A Meeting time is required to readjust the
  estimated clock CLKE of the New Master(2) to
  Master(1).
• The time delay is about 0.25sec (every 400 slots).

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HOPPING SEQUENCE

• The hopping sequence is transferred from the
  Master to the Slave during connection Set-up.
• The same generated sequence is presented to all
  devices in Piconet.
• New Piconets new FHS (Frequency Hopping
  Sequence) created by its Master.

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SSPF HOPPING SEQUENCE

• New Master (slave creating the new Piconet) will
  decrease each hop frequency by 10 times its
  address (AM_ADDR) to control the hopping channel
  (known by all slaves)
• Example
• Master(1) FHS 32, 41, 30, 26, 36, 39
• Leading to new FHS 22, 31, 20, 16, 26, 29
  Generated by new Master(2) Ex-Slave (1)

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SSPF SCHEDULE
Hopping Sequence
32 41 30 26 36
31 50
MASTER
Slave 1
MASTER
MASTER S6
Slave 2
Slave 3
Slave 1
Slave 4
Slave 2
Slave 5
Slave 3
New Master S1
Slave 4
Time
New Hopping sequence
22 31 20 16 26 21
50
Slave 5
Master 1 Packet Transmission
Master S6 Packet Transmission
Packet Reception
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ADVANTAGE OF SSPF

• Slaves have two bandwidths to transfer heavy
  traffic data.
• They could easily switch from one Piconet to
  another at every slot due to synchronisation
  between the two Piconets.
• In case of transmission failure, the Master to
  Master communication will allow any Master to
  forward data and continue data transmission.

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TOTAL THROUGHPUT OF GENERATING PACKETS
700
700
641
641
635.2
635.2
660
660
621.56
621.56
650
650
592.35
592.35
(641)
620
620
(641)
/s
/s
600
600
580
580
/s
Kbits
Kbits
Kbit
550
508.6
508.6
550
540
540
Total Throughput using SSPF
Total Throughput using SSPF
500
500
500
500
Throughput
460
460
450
450
420
420
Total Throughput using SPF
400
Total Throughput
Total Throughput
400
Total Throughput using SPF
380
380
330
330
350
350
340
340
94
92.5
88
79
54
0
94
92.5
88
79
54
0
300
300
300
300
1
2
3
4
5
6
1
2
3
4
5
6
1
1.5
2
2.5
4
1
2
2.5
4
3
3.5
3
3.5
Number of Slaves Sharing both
Piconets
with
Number of Slaves Sharing both
Piconets
with
1.5
Simulation Time (sec)
throughput Percentage Improvement
throughput Percentage Improvement
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CONCLUSIONS FURTHERS WORK

• SSPF is designed to facilitate inter-Piconet
  scheduling.
• Our simulation shows that inter-Piconet
  communication could improve the data traffic
  transfer by gt 90.
• Increases fluidity (packet delays) and on less
  transfer failure.
• The Work presented is the 1st approach of
  scatternet algorithm and in future will be
  developed for more than 8 devices.

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Thank you for your attention
Christophe_at_spd.eee.strath.ac.uk