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

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 Boˇ zidar Radunovi´ c EPFL School of Computer and Communication Sciences UWB4SN / November 4th, 2005 ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE DCC-MAC R. Merz, et al. 1 / 12

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 DCC-MAC R. Merz, et al. 2 / 12

Introduction and Motivation Motivation and Some Assumptions DCC-MAC The Optimal Design for UWB Summary Some system assumptions Impulse Radio UWB Uncoordinated networks, fully decentralized DCC-MAC R. Merz, et al. 3 / 12

Introduction and Motivation Motivation and Some Assumptions DCC-MAC The Optimal Design for UWB Summary What is the optimal design for UWB? Results from [RLB, 04] γ 2 D 2 γ 1 S 2 D 1 S 3 S 1 D 3 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 DCC-MAC R. Merz, et al. 4 / 12

Introduction and Motivation Motivation and Some Assumptions DCC-MAC The Optimal Design for UWB Summary What is the optimal design for UWB? Results from [RLB, 04] γ 2 D 2 γ 1 S 2 D 1 S 3 S 1 D 3 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 DCC-MAC R. Merz, et al. 4 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary With interference mitigation the MAC becomes uncoordinated g ′ � Interference is impulsive Cancel large samples: erasures Nonlinearity g’ Loss: recovered by channel code 2 Trade off: small rate reduction 1 0 There is no exclusion region with −1 interference mitigation −2 −10 −5 0 5 10 No coordination necessary. What is remaining? 1. Rate adaptation 2. Contention at a destination DCC-MAC R. Merz, et al. 5 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary With interference mitigation the MAC becomes uncoordinated g ′ � Interference is impulsive Cancel large samples: erasures Nonlinearity g’ Loss: recovered by channel code 2 Trade off: small rate reduction 1 0 There is no exclusion region with −1 interference mitigation −2 −10 −5 0 5 10 No coordination necessary. What is remaining? 1. Rate adaptation 2. Contention at a destination DCC-MAC R. Merz, et al. 5 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary With interference mitigation the MAC becomes uncoordinated g ′ � Interference is impulsive Cancel large samples: erasures Nonlinearity g’ Loss: recovered by channel code 2 Trade off: small rate reduction 1 0 There is no exclusion region with −1 interference mitigation −2 −10 −5 0 5 10 No coordination necessary. What is remaining? 1. Rate adaptation 2. Contention at a destination DCC-MAC R. Merz, et al. 5 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary We do rate adaptation without SINR measurement R ( t ) = { R 0 = 1 , R 1 , R 2 , . . . , R N } , R i > R i +1 S : initially, codeIndex = N . D : finds best i ≤ N , returns i +2 Rate S : timeout or NACK, 0.8 0.7 codeIndex = min (2 ∗ codeIndex, N ) 0.6 S : if i ′ < i 0.5 codeIndex = i − 1 0.4 0.3 10 20 30 40 50 60 70 80 90 100 else codeIndex = i ′ Control packets: codeIndex = N DCC-MAC R. Merz, et al. 6 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary 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 DCC-MAC R. Merz, et al. 7 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary 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 DCC-MAC R. Merz, et al. 7 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary DCC-MAC: a simple example S2 S1 D Data 1 to D Data 2 to D via S1 Data 2, THS(S1) Data 1, THS(D) Interference but no "collision" Send Send ACK, THS(D) Timer Timer idle Idle, THS(S1) Wait for Idle Max. Backoff Backoff Timer Timer DCC-MAC R. Merz, et al. 8 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary DCC-MAC: a multihop example S2 S1 D Backoff Timer Data 2, THS(S1) Send ACK, THS(S1) Timer busy Idle, THS(S2) Data 2, THS(D) Interference but no "collision" Data 3 to S2 via S1 Max. Backoff Send ACK, THS(D) Timer Timer busy Data 4 to S1 Wait for Idle, THS(S1) Idle Wait for Idle DCC-MAC R. Merz, et al. 9 / 12

Introduction and Motivation The 3 Ingredients of DCC-MAC DCC-MAC Performance evaluation Summary Some simulation results: near-far topology Near-far scenario Random scenario DCC−MAC 3500 3000 Power Control Exclusion TDMA 3000 2500 Throughput (Kbits) Throughput (Kbits) 2500 2000 2000 1500 1500 1000 1000 DCC−MAC 500 Power Control 500 Exclusion TDMA 0 0 1 2 4 8 16 32 1 2 4 8 16 32 Number of Senders Number of Senders DCC-MAC R. Merz, et al. 10 / 12

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 DCC-MAC R. Merz, et al. 11 / 12

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. DCC-MAC R. Merz, et al. 12 / 12