Email: [email protected], [email protected], [email protected]

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Email: [email protected], [email protected], [email protected] Overlapped NACKs: Improving Multicast Performance in Multi-access Wireless Networks IEEE Globecom 2010 Workshop on Pervasive Group Communications (PerGroup 2010) Authors : Luca Canzian, Andrea Zanella, Michele Zorzi

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IEEE Globecom 2010 Workshop on Pervasive Group Communications ( PerGroup 2010). Overlapped NACKs: Improving Multicast Performance in Multi-access Wireless Networks. Authors : Luca   Canzian , Andrea   Zanella , Michele   Zorzi. - PowerPoint PPT Presentation

Transcript of Email: [email protected], [email protected], [email protected]

Page 1: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

Email: [email protected], [email protected], [email protected]

Overlapped NACKs: Improving Multicast Performance in Multi-access

Wireless Networks

IEEE Globecom 2010 Workshop on Pervasive Group Communications (PerGroup 2010)

Authors : Luca  Canzian, Andrea  Zanella, Michele  Zorzi

Page 2: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

• Basic problem• Our approach• Case study: Bluetooth• Performance comparison• Conclusion

2

Outline

Page 3: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

• Basic problem• Our approach• Case study: Bluetooth• Performance comparison• Conclusion

3

Outline

Page 4: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

Multicast: only 1 transmission!!!-> resource saving (time/frequency, power) Increasing rate More bandwidth for other devices/applications

4

Multicast communicationWireless network

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ACK based reliability

ACK

ACK

ACKACK

Devices send ACKs if the packet is correctly received Reliability Scalability Coordination mechanism

Page 6: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

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NACK based reliability

NACK

Devices send NACKs if the packet is NOT correctly received Scalability Reliability Coordination mechanism

NACK

Page 7: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

• Basic problem• Our approach• Case study: Bluetooth• Performance comparison• Conclusion

7

Outline

Page 8: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

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Overlapping NACKs

NACK

NACKs sent in the same resource!! (-> collisions) Scalability No coordination mechanism? Reliability

NACK

1 1 1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1

Nack slave 1 Nack slave 2

Resulting Nack

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DPSK exampleQ

I

Q

I

After 1 symbol period

Q

I

-120°

120°120°

240°

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0

10

Double-NACK structure

1 1 1 1 1 1 1 0 0 0 1 1 1 1 1 1 1

Q

I

Q

I

11 1 1 1 1 1 1 0 1 0 1 1 1 1 1 1 1

I

Q

I

Q

00

10

01

11

DQPSK phase-shifts

First NACK Second NACKPhase displacement

SLA

VE 1

SLA

VE 2

Page 11: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

• Basic problem• Our approach• Case study: Bluetooth• Performance comparison• Conclusion

11

Outline

Page 12: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

Bluetooth technology

• Ad-hoc Personal Area Network (PAN)

• Direct communication only between master and slaves

• Time-Division Duplexing (TDD) communication

• Packets last 1, 3 or 5 slots

• GFSK (1 Mbps), π/4-DPSK (2 Mbps), 8DPSK (3 Mbps)

• No multicast (multi-unicast) !!!-> SIG proposal

12

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ACK and NACK based protocols

SIG (Special Interest Group) proposal

Our proposalOverlapped NACKs

Page 14: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

• Basic problem• Our approach• Case study: Bluetooth• Performance comparison• Conclusion

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Outline

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Throughput vs slaves

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Throughput vs BER& 3-DH5

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Reliability

BER=1E-5 BER=1E-4

DH1 6.9E-11 / 2.1E-10 6.3E-09 / 1.9E-08

DH3 3.0E-09 / 9.0E-09 1.7E-07 / 4.9E-07

DH5 9.7E-09 / 2.9E-08 3.5E-07 / 1.0E-06

2-DH1 2.7E-10 / 8.2E-10 2.3E-08 / 6.8E-08

2-DH3 1.1E-08 / 3.4E-08 3.8E-07 / 1.1E-06

2-DH5 3.4E-08 / 1.0E-07 6.6E-07 / 1.9E-06

3-DH1 6.4E-10 / 1.9E-09 4.9E-08 / 1.4E-07

3-DH3 2.4E-08 / 7.1E-08 5.5E-07 / 1.6E-06

3-DH5 6.9E-08 / 2.0E-07 9.9E-07 / 2.8E-06

On average 1 packet every 625000 is lost !!!

Average PER / Worst case PER

Page 18: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

• Basic problem• Our approach• Case study: Bluetooth• Performance comparison• Conclusion

18

Outline

Page 19: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

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Conclusion

1. New simple NACK based protocol for reliable multicast communications

2. NACK structure to be robust to collisions

3. Comparison with an ACK based protocol for Bluetooth

4. Results show:

• Little reliability loss

• High throughput gain

Page 20: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

Email: [email protected], [email protected], [email protected]

Overlapped NACKs: Improving Multicast Performance in Multi-access

Wireless Networks

IEEE Globecom 2010 Workshop on Pervasive Group Communications (PerGroup 2010)

Authors : Luca  Canzian, Andrea  Zanella, Michele  Zorzi

Page 21: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

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Time synchronization

1 1 1 1 1 1 1 11 1

Q

I

Q

II

Q

11 1 1

1 1 1 11 1 1 1 1 111 1 1

OVERLAPPING INTERVAL

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Time synchronization

1 1 1 1 1 1 1 11 1

Q

I

Q

II

Q

11 1 1

1 1 1 11 1 1 1 1 111 1 1

OVERLAPPING INTERVAL

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0

0

1

0

23

Time synchronization

1 1 1 1 1 1 10 10 1

OVERLAPPING INTERVAL 1

1 1 1 1

1 1 1 1 1 1 10 11 1 1 1 1 1

1

Q

I

Q

I

Q

I

1

OVERLAPPING INTERVAL 2I

Q

00

10

01

11

DQPSK phase-shifts

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Frequency offsetEqual amplitude case

Red turns of 0°Blue turns of 60°

Green turns of 30°

Green turns of 210°!!!-> discontinuity of 180°

Conclusion:• Most time high SNR and constant phase drift

-> it can be compensated • Some time SNR drastically decreases and phase discontinuity

-> this must be taken into account to set correlator threshold

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Frequency offset1 signal much stronger than the other

Red turns of 0°Blue turns of 60°

Conclusion:SNR of the received signal decreases a little

Green ~ Red + noise Max phase error

Max amplitudeerror

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b: average number of bits transmitted in a cycle d: average duration of a cycle

N N-1 1 0. . .

Pe N

N (1-P )e

N-1 (1-P )e

1-P e

PePe N-1

1

(N-1) (1-P ) P

N (1-P ) P

e e

N-1

N-2

ee

N (1-P ) P N-1ee

Markov model Nbite BERP 11

Renewal Process:db

ttuntildtransmittebitsTh

t

lim

Nji

otherwise

ijPPji

Pji

eje

ji ,...,1,0,0

1,

Page 27: Email:  canzian@dei.unipd.it, zanella@dei.unipd.it, zorzi@dei.unipd.it

Markov model

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Probability that the master does not recognize the overlapping of i double NACKs (missed detection probabilities)

N N-1 1

0

. . .

PeN

PePe N-1

1

(N-1) (1-P ) P

N (1-P ) P

e e

N-1

N-2

ee

N (1-P ) PN-1

ee

L L L

[1-P (N-1)]

[1-P (1)]

[1-P (1)]

(N-1) (1-P ) Pe e

N-2P (1)

[1-P (1)][1-P (N-1)]

N N-1 1

(1-P )eN

(1-P )eN-1

1-P e

[1-P (N)]

PeN

P (N)

N (1-P ) PN-1

ee P (N-1)

Pe N-1

P (N-1)

N (1-P ) PN-1

ee P (1)

nr

nr

nr

nr

nr

nr

nrnr

nr

nr

nr

Pe P (1)nr

1 1 1

. . .

)(iPnr

N

iLiP

NiPER

1

N

iLiPB

1

Probability to be absorbed in Li

iLP