DCC-MAC: a Rate Adaptive MAC Protocol for Uncoordinated UWB Networks - - PowerPoint PPT Presentation

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DCC-MAC: a Rate Adaptive MAC Protocol for Uncoordinated UWB Networks - - PowerPoint PPT Presentation

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Introduction and Motivation DCC-MAC Summary DCC-MAC: a Rate Adaptive MAC Protocol for Uncoordinated UWB Networks Ruben Merz J org Widmer Jean-Yves Le Boudec Bo zidar Radunovi c EPFL School of Computer and Communication Sciences

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SLIDE 1

ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE

Introduction and Motivation DCC-MAC Summary

DCC-MAC: a Rate Adaptive MAC Protocol for Uncoordinated UWB Networks

Ruben Merz J¨

  • rg Widmer

Jean-Yves Le Boudec Boˇ zidar Radunovi´ c

EPFL School of Computer and Communication Sciences

UWB4SN / November 4th, 2005

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Introduction and Motivation DCC-MAC Summary

Outline

1 Introduction and Motivation

Motivation and Some Assumptions The Optimal Design for UWB

2 DCC-MAC

The 3 Ingredients of DCC-MAC Performance evaluation

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Introduction and Motivation DCC-MAC Summary Motivation and Some Assumptions The Optimal Design for UWB

Some system assumptions

Impulse Radio UWB Uncoordinated networks, fully decentralized

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Introduction and Motivation DCC-MAC Summary Motivation and Some Assumptions The Optimal Design for UWB

What is the optimal design for UWB?

Results from [RLB, 04] S1 S2 S3 D1 D2 D3 γ2 γ1

1 No power control 2 Inside the exclusion region, source cannot send 3 Rate adapted to the level of interference at destinations

The organization of the MAC depends on the size of the exclusion region

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SLIDE 5

Introduction and Motivation DCC-MAC Summary Motivation and Some Assumptions The Optimal Design for UWB

What is the optimal design for UWB?

Results from [RLB, 04] S1 S2 S3 D1 D2 D3 γ2 γ1

1 No power control 2 Inside the exclusion region, source cannot send 3 Rate adapted to the level of interference at destinations

The organization of the MAC depends on the size of the exclusion region

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Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

With interference mitigation the MAC becomes uncoordinated

Interference is impulsive Cancel large samples: erasures

Loss: recovered by channel code Trade off: small rate reduction

There is no exclusion region with interference mitigation

  • g′

−10 −5 5 10 −2 −1 1 2 Nonlinearity g’

No coordination necessary. What is remaining?

  • 1. Rate adaptation
  • 2. Contention at a destination

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SLIDE 7

Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

With interference mitigation the MAC becomes uncoordinated

Interference is impulsive Cancel large samples: erasures

Loss: recovered by channel code Trade off: small rate reduction

There is no exclusion region with interference mitigation

  • g′

−10 −5 5 10 −2 −1 1 2 Nonlinearity g’

No coordination necessary. What is remaining?

  • 1. Rate adaptation
  • 2. Contention at a destination

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SLIDE 8

Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

With interference mitigation the MAC becomes uncoordinated

Interference is impulsive Cancel large samples: erasures

Loss: recovered by channel code Trade off: small rate reduction

There is no exclusion region with interference mitigation

  • g′

−10 −5 5 10 −2 −1 1 2 Nonlinearity g’

No coordination necessary. What is remaining?

  • 1. Rate adaptation
  • 2. Contention at a destination

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Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

We do rate adaptation without SINR measurement

R(t) = {R0 = 1, R1, R2, . . . , RN} , Ri > Ri+1 S: initially, codeIndex = N. D: finds best i ≤ N, returns i+2 S: timeout or NACK, codeIndex = min(2∗codeIndex, N) S: if i′ < i codeIndex = i − 1 else codeIndex = i′ Control packets: codeIndex = N

10 20 30 40 50 60 70 80 90 100 0.3 0.4 0.5 0.6 0.7 0.8 Rate

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Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

It remains to solve contention for a common destination

We still need a MAC

  • 1. Contention for a destination
  • 2. Multihop

Immediate transmission & Invitation based (Idle signal) Assume no carrier sensing Careful selection of timers Receiver THS based No THS distribution protocol No control channel

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Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

It remains to solve contention for a common destination

We still need a MAC

  • 1. Contention for a destination
  • 2. Multihop

Immediate transmission & Invitation based (Idle signal) Assume no carrier sensing Careful selection of timers Receiver THS based No THS distribution protocol No control channel

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Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

DCC-MAC: a simple example

S1 D S2

Data 1, THS(D) ACK, THS(D) Idle, THS(S1)

idle

Data 2, THS(S1)

Send Timer Wait for Idle Backoff Timer Send Timer

Data 1 to D Data 2 to D via S1

Max. Backoff Timer Interference but no "collision" DCC-MAC

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Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

DCC-MAC: a multihop example

S1 D S2

Data 2, THS(S1) ACK, THS(S1) Idle, THS(S2) Data 2, THS(D)

busy

ACK, THS(D)

busy

Idle, THS(S1)

Backoff Timer Send Timer Max. Backoff Timer Wait for Idle Send Timer Wait for Idle

Data 3 to S2 via S1 Data 4 to S1

Interference but no "collision"

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Introduction and Motivation DCC-MAC Summary The 3 Ingredients of DCC-MAC Performance evaluation

Some simulation results: near-far topology

Near-far scenario

1 2 4 8 16 32 500 1000 1500 2000 2500 3000 Number of Senders Throughput (Kbits) DCC−MAC Power Control Exclusion TDMA

Random scenario

1 2 4 8 16 32 500 1000 1500 2000 2500 3000 3500 Number of Senders Throughput (Kbits) DCC−MAC Power Control Exclusion TDMA

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Introduction and Motivation DCC-MAC Summary

Summary

Key idea: allow interference but adapt the rate Use rate adaptation for multiple-access instead of exclusion or power control Rate adaptation: no coordination among peers 3 ingredients:

Interference mitigation Dynamic channel coding Private MAC

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Introduction and Motivation DCC-MAC Summary

For Further Reading

http://lcawww.epfl.ch/uwb

  • B. Radunovic and J.-Y. Le Boudec

Optimal Power Control, Scheduling and Routing in UWB Networks IEEE Journal on Selected Areas in Communications, 2004

  • R. Merz, J. Widmer, J.-Y. Le Boudec and B. Radunovic

A Joint PHY/MAC Architecture for Low-Radiated Power TH-UWB Wireless Ad-Hoc Networks Wireless Communications and Mobile Computing Journal, 2005.

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