bluetooth throughput improvement using a slave to slave piconet formation by christophe lafon and...
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BLUETOOTH THROUGHPUT BLUETOOTH THROUGHPUT IMPROVEMENT USING A IMPROVEMENT USING A
SLAVE TO SLAVE PICONET SLAVE TO SLAVE PICONET FORMATIONFORMATION
By Christophe Lafon and Tariq S Durrani
Institute for Communications & Signal Processing
Dept. of Electronic & Electrical Engineering
University of Strathclyde
Glasgow - UK
OVERVIEWOVERVIEW
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.
MOTIVATION OF WORKMOTIVATION OF WORK
AIM: New approach to inter-Piconet communicationNew policy: SSPF (Slave to Slave Piconet
Formation).
OBJECTIVES: To achieve faster jumps between different Piconets.
BLUETOOTH BLUETOOTH BACKGROUNDBACKGROUND
Operates in the 2.4 GHz unlicensed ISM band.79 hop frequencies: f = 2402+k MHz, k= 0,..78.Bandwidth 1Mb/sec with Fast hopping 1600 hops/sAccess Code: AM_ADDR: 3 bits to units to distinguish
between Slave unit participating in the Piconet (7 max).
Channel divided into time slot 625s length
The Package is transmitted in 1, 3 or 5 Slots
TIME DIVISION DUPLEX TIME DIVISION DUPLEX (TDD) TRAFFIC BETWEEN (TDD) TRAFFIC BETWEEN
TWO SLAVESTWO SLAVES
S2
S1
S3
MASTER S4
Master
Slave 1
Slave 2
Slave 3
Slave 4time
Slots Traffic between Master and Slaves
ALTERNATIVE APPROACH: ALTERNATIVE APPROACH: BOTH SLAVES ENTER NEW BOTH SLAVES ENTER NEW
PICONETPICONETSlave will indicate to Master of an
important data transfer to another Slave.Payload header:
1 for high traffic0 for low traffic
Both Slaves will then enter in new mode: Slave to Slave Piconet Formation (SSPF).
SWITCHING PICONETSSWITCHING 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).
CLOCK CLOCK SYNCHRONISATIONSYNCHRONISATION
Each Device has a Native Clock (CLKN).A Piconet is characterized by Master
Frequency Hopping SchemeAccess code (AM_ADDR)Timing synchronization (CLK)
Master determines the bit rate allocated to each slave
Slaves do not synchronize to the masterCalculate offsets to master’s Bluetooth Clock CLK.Monitor timing drift
SSPF CLOCK SSPF CLOCK SYNCHRONISATIONSYNCHRONISATION
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.
MEETING TIME TO MEETING TIME TO AVOID CLOCK DRIFTAVOID 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).
MASTER
MASTER S1
Slave
Clock Drift too important Transmission Cancel
CLOCK DRIFT > 10μsCLOCK DRIFT < 10μs
MASTER
MASTER S1
Slave
Clock Drift too important Transmission Cancel
CLOCK DRIFT > 10μs
MASTER
MASTER S1
Slave
Clock Drift too important Transmission Cancel
CLOCK DRIFT > 10μs
MASTER
MASTER S1
Slave
Clock Drift too important Transmission Cancel
CLOCK DRIFT > 10μsCLOCK DRIFT < 10μs
HOPPING SEQUENCEHOPPING 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.
SSPF HOPPING SSPF HOPPING SEQUENCESEQUENCE
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, 39Leading to new FHS: 22, 31, 20, 16, 26, 29
Generated by new Master(2) [Ex-Slave (1)]
SSPF SCHEDULESSPF SCHEDULE
MASTERMASTER
S6
Slave 2
Slave 3
Slave 4
Slave 1
Slave 5
Hopping SequenceHopping Sequence
Slave 4
Time
New Master S1
New Hopping New Hopping sequencesequence 22 31 20 16 26 21 50
MASTER
Slave 1
Slave 2
Slave 3
32 41 30 26 36 31 50
Slave 5
Master 1 Packet Transmission
Master S6 Packet Transmission
Packet Reception
ADVANTAGE OF SSPFADVANTAGE 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.
TOTAL THROUGHPUT OF TOTAL THROUGHPUT OF GENERATING PACKETSGENERATING PACKETS
Total Throughput using SSPF
Total Throughput using SPF
1 1.5 2 2.5 3 3.5 4
300
350
400
450
500
550
600
650
700
(641)
Total Throughput using SSPF
Total Throughput using SPF
1 1.5 2 2.5 3 3.5 4
300
350
400
450
500
550
600
650
700
Simulation Time (sec)
Thr
ough
put [
Kbi
t /s]
(641)
330
508.6
592.35621.56
635.2 641
300
340
380
420
460
500
540
580
620
660
1 2 3 4 5 6
Number of Slaves Sharing both Piconets with throughput Percentage Improvement
Tot
al T
hrou
ghpu
t [K
bits
/s]
94%92.5%88%79%54%0%
330
508.6
592.35621.56
635.2 641
300
340
380
420
460
500
540
580
620
660
1 2 3 4 5 6
Number of Slaves Sharing both Piconets with throughput Percentage Improvement
Tot
al T
hrou
ghpu
t [K
bits
/s]
94%92.5%88%79%54%0%
CONCLUSIONS & CONCLUSIONS & FURTHERS WORKFURTHERS WORK
SSPF is designed to facilitate inter-Piconet scheduling.
Our simulation shows that inter-Piconet communication could improve the data traffic transfer by > 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.
