Department of Information Engineering University of Padova, ITALY

1. Department of Information EngineeringUniversity of Padova, ITALY Throughput and Energy Efficiency of Bluetooth v2 + EDR in Fading Channels A note on the use of these ppt slides:We’re making these slides freely available to all, hoping they might be of use for researchers and/or students. They’re in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. In return for use, we only ask the following:If you use these slides (e.g., in a class, presentations, talks and so on) in substantially unaltered form, that you mention their source.If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and put a link to the authors webpage: www.dei.unipd.it/~zanella Thanks and enjoy! March 31 - April 3 Las Vegas

2. Department of Information EngineeringUniversity of Padova, ITALY Special Interest Group on NEtworking & Telecommunications Throughput and Energy Efficiency of Bluetooth v2 + EDR in Fading Channels Andrea Zanella, Michele Zorzi {andrea.zanella, michele.zorzi}@dei.unipd.it Speaker: Marco Miozzo WCNC 2008 March 31 - April 3 Las Vegas

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 March 31 - April 3 Las Vegas

4. Aims of the work • Questions: • Are the Bluetooth promises maintained? • What’s the energy efficiency & throughput achieved by EDRframe 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! March 31 - April 3 Las Vegas

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, … March 31 - April 3 Las Vegas

6. What standard says… Bluetooth reception mechanism March 31 - April 3 Las Vegas

7. 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 networksin wireless channel environment,” ICSNC’06 [14]L. E. MillerandJ. S. Lee, “BER Expressions for Differentially Detectedπ/4 DQPSK Modulation,” IEEE TRANSACTIONS ON COMMUNICATIONS, vol. 46, no. 1, pp. 71–81, January1998. [15]N. Benvenuto and C. Giovanni,Algorithms for Communications Systemsand their Applications. Wiley, 2002. March 31 - April 3 Las Vegas

8. Baseband frame formats GFSK AC HEAD PAYL BR 0.22 ms Tslot=0.625 ms TDxn=nTslot DPSK GFSK EDR Trailer PAYL AC HEAD GUARD SYNC EDR 0.22 ms Tslot=0.625 ms TjDxn= nTslot March 31 - April 3 Las Vegas

9. A B B B B B H G F H Retransmissions NAK MASTER • 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 nevertransmit 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! ACK SLAVE X A DPCK B X DPCK March 31 - April 3 Las Vegas

10. Mathematical Analysis System Model March 31 - April 3 Las Vegas

11. 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… March 31 - April 3 Las Vegas

12. 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 March 31 - April 3 Las Vegas

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 March 31 - April 3 Las Vegas

14. Master Frame Time reward ( T ) Slave Frame Empty slot n+m n+1 March 31 - April 3 Las Vegas

15. Dxn Dym Dxn --- Data reward ( D ) Master’s Data Slave’s Data No Useful Data Dym --- --- --- --- March 31 - April 3 Las Vegas

16. Master energy reward ( W(M)) Tx power Rx Power Sx power March 31 - April 3 Las Vegas

17. 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! March 31 - April 3 Las Vegas

18. Performance Analysis Results March 31 - April 3 Las Vegas

19. AWGN March 31 - April 3 Las Vegas

20. Rayleigh March 31 - April 3 Las Vegas

21. Conclusions • Main Contribution • mathematical framework for performance evaluation of Bluetooth EDR links • Results • 3DHn yield better performance for SNR>20 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 March 31 - April 3 Las Vegas

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 March 31 - April 3 Las Vegas

23. Extra Slides… Spare slides… March 31 - April 3 Las Vegas

24. 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 h=2202745 bits 0: BER March 31 - April 3 Las Vegas

25. 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 March 31 - April 3 Las Vegas

26. 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 March 31 - April 3 Las Vegas

27. Swapping Master and Slave* *Results not reported in the WCNC paper March 31 - April 3 Las Vegas