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1
Department of Information EngineeringUniversity
of Padova, ITALY
Throughput and Energy Ef?ciency of Bluetooth v2
EDR in Fading Channels
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Department of Information EngineeringUniversity
of Padova, ITALY
Special Interest Group on NEtworking
Telecommunications
Throughput and Energy Ef?ciency of Bluetooth v2
EDR in Fading Channels
Andrea Zanella, Michele Zorzi
andrea.zanella, michele.zorzi_at_dei.unipd.it
Speaker Marco Miozzo
WCNC 2008
3
Motivations

• Bluetooth was designed to be integrated in
  portable battery driven electronic devices ?
• Energy Saving is a key issue!
• Units periodically scan radio channel for valid
  packets
• Scanning takes just the time for a valid packet
  to be recognized
• Units that are not addressed by any valid packet
  are active for less than 10 of the time
• WPAN market is expanding and it aims at becoming
  the standard the facto for short range
  communications ?
• High Throughput is very welcome!
• Bluetooth v2.0 EDR (Enhanced Data Rate) promise
  bit rates up to 3 Mbps and faster node connections

4
Aims of the work

• Questions
• Are the Bluetooth promises maintained?
• Whats the energy efficiency throughput
  achieved by EDR frame formats in realistic
  channels?
• Which units shall be the Master in point-to-point
  connections?
• Answer
• Well, in most cases, we cannot provide univocal
  answers
• but we can offer a mathematical model to decide
  case by case!

5
Basic ingredients

• Define realistic radio channel model
• Flat Rice-modelled fading channel
• BER curves for different modulations taken from
  the literature
• Capture system dynamic by means of a Finite State
  Markov Chain (FSMC)
• State transitions driven by packet reception
  events
• Define appropriate reward functions
• Data, Energy, Time
• Apply renewal reward theorem to get system
  performance
• Throughput, energy efficiency, energy balancing,
  

6
What standard says
Bluetooth reception mechanism
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Physical layer

• Basic Rate 1Mbps
• GFSK 13
• EDR2 2Mbps
• ?/4-DQPSK 14
• EDR3
• 8DPSK 15

13 J. S. Roh, Performance analysis and
evaluation of Bluetooth networks in wireless
channel environment, ICSNC06 14 L. E.
MillerandJ. S. Lee, BER Expressions for
Differentially Detected p/4 DQPSK Modulation,
IEEE TRANSACTIONS ON COMMUNICATIONS, vol. 46, no.
1, pp. 7181, January1998. 15 N. Benvenuto and
C. Giovanni, Algorithms for Communications
Systems and their Applications. Wiley, 2002.
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Baseband frame formats
GFSK
AC
HEAD
PAYL
BR
0.22 ms
Tslot0.625 ms
TDxnnTslot
DPSK
GFSK
EDR Trailer
AC
HEAD
PAYL
GUARD
SYNC
EDR
0.22 ms
Tslot0.625 ms
TjDxn nTslot
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Retransmissions
NAK
MASTER
ACK
SLAVE
X
A
B
X
DPCK
DPCK

• Automatic Retransmission Query (ARQ)
• Each data packet is transmitted and retransmitted
  until positive acknowledge is returned by the
  destination
• Negative acknowledgement is implicitly assumed!
• Errors on return packet determine transmission of
  duplicate packets (DUPCK)
• Slave filters out DUPCKs by checking their
  sequence number
• Slave does never transmit DUPCKs!
• Slave can transmit when it receives a Master
  packet
• Master packet piggy-backs the ACK/NACK for
  previous Slave transmission
• Slave retransmits only when needed!

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Mathematical Analysis
System Model
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Mathematical Model

• Normal State (N)
• Master transmits packets that have never been
  correctly received by the slave
• Duplicate State (D)
• Master transmits duplicate packets (DUPCKs)

• The steady-state probabilities are, then,

• State transition probabilities depend on the
  reception events

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Reception events
Reception Event Index
Slaves tx

• Reception events
• Ds Data successful
• AC ok, HEAD ok, CRC ok
• Df Data failure
• AC ok, HEAD ok, CRC error
• Hf HEAD failure
• AC ok, HEAD error
• Af AC failure
• AC error
• MC state transitions
• N enter Normal State
• Master tx non-duplicate packets
• D enter Duplicate State
• Master tx DUPCKs
• X loop step
• Return in the same state

Master tx
13
Reward Functions

• For each state j we define the following reward
  functions
• Tj Average amount of time spent in state j
• Dj(x) Average amount of data delivered by unit
  x?M,S
• Wj(x) Average amount of energy consumed by unit
  x?M,S
• The average amount of reward earned in state j is
  given by

• Performance indexes
• Energy Efficiency ?
• Goodput G

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Time reward ( T )
Slave Frame
Empty slot
nm
n1
15
Data reward ( D )
Masters Data
Slaves Data
No Useful Data
Dym
---
---
---
---
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Master energy reward ( W(M))
Tx power
Rx Power
Sx power
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Slave energy reward ( W )

• Slave energy reward resembles mater one except
  that, in D state, Slave does not listen for the
  PAYL field of recognized downlink packet since it
  has been already correctly received!

18
Performance Analysis
Results
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AWGN
20
Rayleigh
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Conclusions

• Main Contribution
• mathematical framework for performance evaluation
  of Bluetooth EDR links
• Results
• 3DHn yield better performance for SNRgt20 dB
• 2DHn perform better in the low SNR region
• 1DHn always show poor performance
• Results refer to a specific case study, but the
  analytical model is general

22
Department of Information EngineeringUniversity
of Padova, ITALY
Mathematical Analysis of Bluetooth Energy
Efficiency
Andrea Zanella, Daniele Miorandi, Silvano Pupolin
Questions?
WPMC 2003, 21-22 October 2003
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Extra Slides
Spare slides
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Conditioned probabilities
DHn Unprotected DMn (15,10) Hamming FEC
2-time bit rep. (1/3 FEC)
Receiver- Correlator Margin (S)
AC
HEAD
PAYLOAD
CRC
54 bits
72 bits
h220?2745 bits
?0 BER
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Hypothesis

• Single slave piconet
• Saturated links
• Master and slave have always packets waiting for
  transmission
• Unlimited retransmission attempts
• Packets are transmitted over and over again until
  positive acknowledgement
• Static Segmentation Reassembly policy
• Unique packet type per connection
• Sensing capability
• Nodes can to sense the channel to identify the
  end of ongoing transmissions
• Nodes always wait for idle channel before
  attempting new transmissions

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Packet error probabilities

• Let us define the following basic packet
  reception events
• Afr AC does not check
• Packet is not recognized
• Hf AC does check HEAD does not
• Packet is not recognized
• Df AC HEAD do check, PAYL does not
• Packet is recognized but PAYL contains
  unrecoverable errors
• Ds AC HEAD PAYL do check
• Packet is successfully received
• Packets experiment independent error events
  because of the frequency hopping mechanism

27
Swapping Master and Slave
Results not reported in the WCNC paper