B. Tavli and W. B. Heinzelman Julián Urbano jurbano@vt

1. Energy and Spatial Reuse Efficient Network-Wide Real-TimeData Broadcastingin Mobile Ad Hoc Networks B. Tavli and W. B. Heinzelman Julián Urbano jurbano@vt.edu

2. Overview • Introduction • Background • MH-TRACE • NB-TRACE • Simulation • Conclusions

3. Introduction

4. Network-Wide Real-TimeData Broadcasting • Military networks • Broadcast • QoS • Can not restrict to single-hop • Energy efficiency, efficient spatial reuse and QoS are mandatory • No architecture proposed so far addressing all them • Network-wide Broadcasting through Time Reservation using Adaptive Control for Energy efficiency (NB-TRACE) • Based on MH-TRACE

5. Background

6. Energy Dissipation • Different Categories • Transmit mode • Receive mode • Idle mode • Carrier sense mode • Sleep mode

7. Energy Dissipation (II) • How to Achieve it? • Unnecessary carrier sensing • Idle energy dissipation • Overhear irrelevant packets • Transmit energy dissipation • Reduce overhead

8. Energy Dissipation (III) • Before • IEEE 802.11 supports ATIM • Ad Hoc Traffic Indication Message • Reduces idle time but doesn’t address overhear • Focused on unicast traffic • SMAC • Periodically shuts off radios to reduce idle time • With low traffic outperforms IEEE 802.11 • TSMAC and RSMAC

9. Energy Dissipation (and IV) • About overhearing • Information Summarization (IS) packet • RTS/CTS packets on top of IEEE 802.11 • Power Aware Multiaccess protocol with Signaling for Ad Hoc Networks (PAMAS) • Redundant IS packet? Go sleep! • Delay, throughput and transmit dissipation • There is an optimum transmit radio DOP • Beyond DOP multi-hop outperforms single-hop • Great for constant transmit range radios

10. Efficient Spatial Reuse • # retransmissions required for a packet to be received by every node • Algorithms • Non-coordinated • Fully coordinated • Create a Minimum Connected Dominating Set • Partially coordinated • Create a MCDS, almost

11. Efficient Spatial Reuse (II) • Non-coordinated • Flooding • With Random Access Delay (RAD) from 0 to TRAD • Gossiping • With RAD and probability pGSP

12. Efficient Spatial Reuse (III) • Fully coordinated algorithms • Based on global info • NP-problem

13. Efficient Spatial Reuse (and IV) • Partially coordinated algorithms • Based on local info • Counter-Based Broadcasting (CBB) • Count packets until broadcast timer expires • If received less than NCBB retransmit • Distance-Based Broadcasting (DBB) • Based on received power strength • If closest received is beyond DDBB retransmit

14. Quality of Service • Necessitates • Low delay • # hops traversed and contention level • Low jitter • Deviation from periodicity of packet receptions • High Packet Delivery Ratio (PDR) • Drops and collisions • Parameters • TDROP = 150ms • Packet Generation period (TPG) • PDR = 95%

15. Quality of Service (and II) • Highly related to energy efficiency • Centralized Control? • Not practical in Mobile Ad Hoc • High overhead • Clustering with Cluster Heads (CH) • Schedule the channel access • Some nodes can sleep

16. MH-TRACE

17. MH-TRACE • Multi-Hop Time Reservation using Adaptive Control for Energy efficiency

18. MH-TRACE (and II) • Gain access through the contention slots • If gets access fill out the corresponding IS slot • Transmit in the corresponding data slot… • …until it finishes? Starvation? • Network synchronization through GPS

19. NB-TRACE

20. Design Principles • Integrate energy-efficiency in MH-TRACE • Flooding • IS = (IDnode, IDpacket) • Go sleep! • Problems with other algorithms • MH-TRACE is application-based • NB-TRACE floods the network and prunes • Maintain a Control Dominating Set (CDS)

21. Overview • Time Division Multiple Access (TDMA) • Initially flood to the whole network • ACK the upstream nodes • If no ACK in TACK cease rebroadcast • Algorithm • Initial Flooding (IFL) • Pruning (PRN) • Repair Branch (RPB) • Create Branch (CRB) • Activate Branch (ACB)

22. Initial Flooding • Broadcast packets to one-hop neighbors • Contend channel access and rebroadcast • Eventually every node has received • IFL IDD=1 for TIFL so every node wakes up

23. Pruning • 3 states for nodes • Passive • Active • Activate Branch (ACB) • Problem: stop ACKing from outermost leaf • Eventually, only the source node broadcasts • Solution: CHs always rebroadcast • Maintain the Non-Connected Dominating Set

24. Pruning (and II) • Eventually 1, 3, 5 and 7 go to passive mode • 0, 2, 4 and 6 make up the broadcast tree • 5 stops rebroadcast after TACK, 3 stops after 2TACK, 1 stops after 3TACK • Problem: the nodes are mobile • Re-flood again? Not efficient

25. Repair Branch • Mobility causes CHs to go out and come in • New CH stays in startup mode • Mark the beacon packet • Every node rebroadcasts it • Problem: broken trees

26. Create Branch • If a node detects an inactive CH in TCRB • Switch to active and rebroadcast

27. Activate Branch • If a node does not receive for TACB • Go to ACB mode • Send ACB packet with pACB • Into the IS slots in order not to modify MH-TRACE • If a node receives an ACB packet • Switch to active and begin relying • If there is nothing to send, they go to ACB mode • If an ACB node receives data • Switch to active and begin relying

28. Packet Drop Threshold • TDROP used throughout the network • TDROP-SOURCE used at the source node • TDROP-SOURCE=TPG

29. Simulations

30. Overview • QoS and energy dissipation on • NB-TRACE • MH-TRACE with • Flooding • IEEE 802.11 and SMAC with • Flooding • Gossiping • CBB • DBB

31. Environment • Data packets of 110bytes • Node mobility speed from 0.0 to 5.0m/s • 2.5±0.2m/s • 2.2 ±0.4m/s • 1km wide network • 80 nodes • Data rate of 32Kbps

32. Performance Analysis • 3B = IFL, PRN and RPB • 4B = IFL, PRN, RPB and CPB

33. Performance Analysis (II) • Time • 81.4% in sleep • 16.7% in idle • 2.8% in transmit, receive and carrier sense • 19.4% of the total energy dissipation • Energy • 82.4% packet transmissions • 7.5% IS transmissions • 10.1% other control packet transmissions

34. Performance Analysis (III)

35. Performance Analysis (and IV)

36. Varying the Data Rate • Adjust the superframe size • Adjust # of data slots per frame • Superframe time≈TPG=25ms.

37. Varying the Data Rate (and II)

38. Varying the Node Density • 1 by 1km network with 48Kbps

39. Conclusions

40. Overview • Most of the work to date targeted at deducing transmit energy dissipation only • NB-TRACE also targets receiving, idle, sleep and carrier sense dissipation • According to the 2 (experimental) energy models, transmit energy is not as dominant as thought

41. Quality of Service • Satisfies QoS requirements under several different scenarios • Robustness of the broadcast tree • Maintenance of the NCDS • Cross-layer design • Automatic renewal of channel access

42. Energy Dissipation • It is way lower • Coordinated channel access • Packet discrimination • Lower Average Retransmitting Nodes (ARN)

43. Delay • It is larger with small networks • Restricted channel access • Maintains a regular delay with bigger networks • It is much lower with larger networks • High node density • High data rates

44. Jitter • Lower to all but MH-TRACE • Channel access granted by CHs after contend

45. Spatial Reuse • Better than the others • Robustness of channel access • Full integration with MAC layer • IEEE‘s MAC doesn’t prevent excessive collisions • No data!

46. Energy Model • Energy savings are related to the model • Some radios do not support sleep mode or the dissipation difference is small • However, NB-TRACE performs well

47. Future Work • Extend TRACE to multicast and unicast • The blocks are reusable • CHs can become multicasting group members as they always broadcast • Realistic environments with channel errors • MH-TRACE is shown to outperform IEEE