Department of Information Engineering University of Padova ITALY

Department of Information Engineering University of Padova, ITALY Throughput and Energy Efficiency of Bluetooth v 2 + 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 Power. Point 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 WCNC 2008 Thanks and enjoy! March 31 - April 3 Las Vegas

Department of Information Engineering University of Padova, ITALY Special Interest Group on NEtworking & Telecommunications Throughput and Energy Efficiency of Bluetooth v 2 + 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

Motivations q Bluetooth was designed to be integrated in portable battery driven electronic devices Energy Saving is a key issue! Ø Ø Ø q 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! Ø WCNC 2008 Bluetooth v 2. 0 + EDR (Enhanced Data Rate) promise bit rates up to 3 Mbps and faster node connections March 31 - April 3 Las Vegas

Aims of the work q Questions: Ø Are the Bluetooth promises maintained? Ø What’s the energy efficiency & throughput achieved by EDR frame formats in realistic channels? Ø q Which units shall be the Master in point-to-point connections? Answer Ø Well, in most cases, we cannot provide univocal answers… …but we can offer a mathematical model to decide case by case! WCNC 2008 March 31 - April 3 Las Vegas

Basic ingredients q q Define realistic radio channel model Ø Flat Rice-modelled fading channel Ø BER curves for different modulations taken from the literature Capture system dynamic by means of a Finite State Markov Chain (FSMC) Ø q Define appropriate reward functions Ø q State transitions driven by packet reception events Data, Energy, Time Apply renewal reward theorem to get system performance Ø Throughput, energy efficiency, energy balancing, … WCNC 2008 March 31 - April 3 Las Vegas

What standard says… Bluetooth reception mechanism WCNC 2008 March 31 - April 3 Las Vegas

Physical layer q Basic Rate: 1 Mbps Ø q EDR 2: 2 Mbps Ø q GFSK [13] /4 -DQPSK [14] EDR 3 Ø 8 DPSK [15] [13] J. S. Roh, “Performance analysis and evaluation of Bluetooth networks in wireless channel environment, ” ICSNC’ 06 [14] L. E. Millerand. J. S. Lee, “BER Expressions for Differentially Detected π/4 DQPSK Modulation, ” IEEE TRANSACTIONS ON COMMUNICATIONS, vol. 46, no. 1, pp. 71– 81, January 1998. [15] N. Benvenuto and C. Giovanni, Algorithms for Communications Systems and their Applications. Wiley, 2002. March 31 - April 3 Las Vegas WCNC 2008

Baseband frame formats GFSK BR AC HEAD PAYL 0. 22 ms Tslot=0. 625 ms TDxn=n. Tslot DPSK GFSK EDR AC HEAD GUARD SYNC PAYL EDR Trailer 0. 22 ms Tslot=0. 625 ms Tj. Dxn= n. Tslot WCNC 2008 March 31 - April 3 Las Vegas

Retransmissions A B B B NAK MASTER ACK G SLAVE A q Automatic F X H H B X DPCK Retransmission Query (ARQ): Ø Each data packet is transmitted and retransmitted until positive acknowledge is returned by the destination Ø Negative acknowledgement is implicitly assumed! ü Errors on return packet determine transmission of duplicate packets (DUPCK) ü Slave filters out DUPCKs by checking their sequence number Ø Slave does never transmit DUPCKs! ü Slave can transmit when it receives a Master packet ü Master packet piggy-backs the ACK/NACK for previous Slave transmission ü Slave retransmits only when needed! WCNC 2008 March 31 - April 3 Las Vegas

Mathematical Analysis System Model WCNC 2008 March 31 - April 3 Las Vegas

Mathematical Model q Normal State (N) Ø q Duplicate State (D) Ø q q Master transmits packets that have never been correctly received by the slave Master transmits duplicate packets (DUPCKs) The steady-state probabilities are, then, State transition probabilities depend on the reception events… WCNC 2008 March 31 - April 3 Las Vegas

Reception events Reception Event Index Slaves tx q Reception events Ø Master tx Ds = Data successful ü Ø Df = Data failure ü Ø AC error MC state transitions Ø N = enter Normal State ü Ø Ø Master tx non-duplicate packets D = enter Duplicate State ü Master tx DUPCKs X = loop step ü WCNC 2008 AC ok, HEAD error Af = AC failure ü q AC ok, HEAD ok, CRC error Hf = HEAD failure ü Ø AC ok, HEAD ok, CRC ok Return in the same state March 31 - April 3 Las Vegas

Reward Functions q q For each state j we define the following reward functions Ø Tj= Average amount of time spent in state j Ø Dj(x)= Average amount of data delivered by unit x {M, S} Ø Wj(x)= Average amount of energy consumed by unit x {M, S} Ø The average amount of reward earned in state j is given by Performance indexes Ø Energy Efficiency: Ø Goodput: G WCNC 2008 March 31 - April 3 Las Vegas

Time reward ( T ) Master Frame Slave Frame Empty slot n+m n+1 WCNC 2008 March 31 - April 3 Las Vegas

Data reward ( D ) Master’s Data Slave’s Data Dxn Dym Dxn --- No Useful Data Dym ----- WCNC 2008 ----- March 31 - April 3 Las Vegas

Master energy reward ( W(M)) Tx power WCNC 2008 Rx Power Sx power March 31 - April 3 Las Vegas

Slave energy reward ( W ) q 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! WCNC 2008 March 31 - April 3 Las Vegas

Performance Analysis Results WCNC 2008 March 31 - April 3 Las Vegas

AWGN WCNC 2008 March 31 - April 3 Las Vegas

Rayleigh WCNC 2008 March 31 - April 3 Las Vegas

Conclusions q Main Contribution Ø q Results Ø Ø Ø q mathematical framework for performance evaluation of Bluetooth EDR links 3 DHn yield better performance for SNR>20 d. B 2 DHn perform better in the low SNR region 1 DHn always show poor performance Results refer to a specific case study, but the analytical model is general WCNC 2008 March 31 - April 3 Las Vegas

Department of Information Engineering University of Padova, ITALY Mathematical Analysis of Bluetooth Energy Efficiency Andrea Zanella, Daniele Miorandi, Silvano Pupolin Questions? WPMC 2003, 21 -22 October 2003 WCNC 2008 March 31 - April 3 Las Vegas

Extra Slides… Spare slides… WCNC 2008 March 31 - April 3 Las Vegas

Conditioned probabilities Receiver. Correlator Margin (S) AC 72 bits HEAD 54 bits 2 -time bit rep. (1/3 FEC) DHn: Unprotected DMn: (15, 10) Hamming FEC PAYLOAD CRC h=220 2745 bits 0: BER WCNC 2008 March 31 - April 3 Las Vegas

Hypothesis q Single slave piconet q Saturated links Ø q Unlimited retransmission attempts Ø q Packets are transmitted over and over again until positive acknowledgement Static Segmentation & Reassembly policy Ø q Master and slave have always packets waiting for transmission Unique packet type per connection Sensing capability Ø Nodes can to sense the channel to identify the end of ongoing transmissions Ø Nodes always wait for idle channel before attempting new transmissions WCNC 2008 March 31 - April 3 Las Vegas

Packet error probabilities q Let us define the following basic packet reception events Ø Afr: AC does not check ü Ø Hf: AC does check & HEAD does not ü Ø Packet is recognized but PAYL contains unrecoverable errors Ds: AC & HEAD & PAYL do check ü q Packet is not recognized Df: AC & HEAD do check, PAYL does not ü Ø Packet is not recognized Packet is successfully received Packets experiment independent error events because of the frequency hopping mechanism WCNC 2008 March 31 - April 3 Las Vegas

Swapping Master and Slave* *Results not reported in the WCNC paper WCNC 2008 March 31 - April 3 Las Vegas