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Low-Power Wireless Bus Federico Ferrari 1, Marco Zimmerling 1, Luca Mottola 2, Lothar Thiele 1 1 Computer Engineering and Networks Laboratory, ETH Zurich,

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Presentation on theme: "Low-Power Wireless Bus Federico Ferrari 1, Marco Zimmerling 1, Luca Mottola 2, Lothar Thiele 1 1 Computer Engineering and Networks Laboratory, ETH Zurich,"— Presentation transcript:

1 Low-Power Wireless Bus Federico Ferrari 1, Marco Zimmerling 1, Luca Mottola 2, Lothar Thiele 1 1 Computer Engineering and Networks Laboratory, ETH Zurich, Switzerland 2 Politecnico di Milano, Italy and Swedish Institute of Computer Science (SICS) SenSys '12, November 7, 2012 Toronto, ON, Canada

2 Low-Power Wireless Bus2 Low-Power Wireless Applications November 7, 2012 Have diverse communication requirements… Environmental monitoring: Long-term data collection at a single sink PermaSense [Beutel et al., IPSN 2009]

3 Clinical monitoring: Mobile nodes immersed in static infrastructure [Chipara et al., SenSys 2010] Have diverse communication requirements… Low-Power Wireless Bus3 Low-Power Wireless Applications November 7, 2012

4 Have diverse communication requirements… Low-Power Wireless Bus4 Low-Power Wireless Applications November 7, 2012 Closed-loop control: Collection at multiple sinks and dissemination TRITon [Ceriotti et al., IPSN 2011]

5 Low-Power Wireless Bus5 Have diverse communication requirements… Low-Power Wireless Applications November 7, 2012 Employ increasingly complex protocol ensembles Which protocol(s) for future applications? – Distributed control loops – Highly mobile scenarios DRAP + CTP + custom MAC Custom collection/ dissemination + LPL Dozer

6 Low-Power Wireless Bus (LWB) Shared bus for low-power wireless networks, where all nodes receive all packets – Multiple communication patterns – Node mobility without performance loss – Resilience to topology changes – High reliability and efficiency November 7, 2012Low-Power Wireless Bus6

7 LWB Design Principles Use only network floods – Multi-hop wireless network Shared bus Synchronized, time-triggered operation – Collision-free and efficient bus accesses Centralized scheduling – A controller node orchestrates all communication November 7, 2012Low-Power Wireless Bus7 controller Low-Power Wireless Bus

8 Network Flooding: Glossy Fast and reliable – A few ms to flood > 100 nodes – Reliability > % in most scenarios Accurate global time synchronization (< 1 s) – Enables time-triggered operation No topology-dependent state – Enables support for mobility November 7, 2012Low-Power Wireless Bus8 [Ferrari et al., IPSN 2011]

9 Time-Triggered Operation LWB operation is confined to rounds A round consists of non-overlapping slots Each slot corresponds to a distinct flood November 7, 2012Low-Power Wireless Bus9 Round period Tt n1n2n3 n1 n1 n2 n3

10 Time-Triggered Operation LWB operation is confined to rounds A round consists of non-overlapping slots Each slot corresponds to a distinct flood November 7, 2012Low-Power Wireless Bus10 Round period Tt n1n2n3 n2 n1 n2 n3

11 Time-Triggered Operation LWB operation is confined to rounds A round consists of non-overlapping slots Each slot corresponds to a distinct flood November 7, 2012Low-Power Wireless Bus11 Round period Tt n1n2n3 n1 n2 n3

12 Add and remove periodic streams of data stream_id add_stream(period, start_time) void remove_stream(stream_id) Send and receive application data void send_data(&data) void data_received(&data) Low-Power Wireless Bus Application Interface November 7, 2012Low-Power Wireless Bus12 controller Application add_stream() remove_stream() send_data() data_received() LWB

13 Centralized Scheduling Scheduler: active at the controller – Receives stream requests – Computes communication schedule Round period T Allocation of slots to streams Example scheduling policy – Minimize energy while providing enough bandwidth – Ensure fair allocation of slots to streams November 7, 2012Low-Power Wireless Bus13 T t n1n2n3

14 LWB Activity during a Round Schedule: sent by the controller, also for time-sync Data: transmitted by allocated sources Contention: competed by sources for stream requests November 7, 2012Low-Power Wireless Bus14 Tt controller Schedule (not allocated) Contention n1 Data n2 Data n3 Data … controller computes new schedule

15 0 Example LWB Execution November 7, 2012 n2 n1 c t = 0 ScheduleContention n1 generates packets at t = 0, 3, 6, …, 60, … add stream Receive from n1 Compute new schedule T = 1 {Ø} add stream n2 generates packets at t = 0, 5, 10, …, 60, … Low-Power Wireless Bus15 add stream Receive from n1 Compute new schedule T = 1 {Ø} add stream t c n1 n2 c is aware of n1s data stream

16 1 Example LWB Execution November 7, 2012Low-Power Wireless Bus16 n2 n1 c t = 1 Compute new schedule T = 1 {n1} data 0 add stream ScheduleContentionData Compute new schedule T = 1 {n1} data 0 add stream 0 t c n1 n2 c is aware of n1s and n2s data streams n1 generates packets at t = 0, 3, 6, …, 60, … n2 generates packets at t = 0, 5, 10, …, 60, …

17 20 Example LWB Execution November 7, 2012Low-Power Wireless Bus17 n2 n1 c t = 2 ScheduleContentionData Compute new schedule T = 1 {n2} data 0 Compute new schedule T = 1 {n2} data 0 1 t c n1 n2 Allocate slots for packets ready to be transmitted n1 generates packets at t = 0, 3, 6, …, 60, … n2 generates packets at t = 0, 5, 10, …, 60, …

18 … Example LWB Execution November 7, 2012Low-Power Wireless Bus18 n2 n1 c t = 60 t c n1 n2 Compute new schedule T = 30 {n1,n2} data 60 ScheduleContentionData Traffic is stable: Increase T n1 generates packets at t = 0, 3, 6, …, 60, … n2 generates packets at t = 0, 5, 10, …, 60, …

19 120 … … Example LWB Execution November 7, 2012Low-Power Wireless Bus19 n2 n1 c t = 90 t c n1 n2 Compute new schedule T = 30 {n1,n2} SC Compute new schedule Data … n1 generates packets at t = 0, 3, 6, …, 60, … n2 generates packets at t = 0, 5, 10, …, 60, …

20 LWB Run-Time Challenges Node failures – Remain operational after controller failures – Stop allocating slots to failed sources Communication failures – Nodes communicate only if synchronized Promptly adapt to traffic changes – Decrease T after a received stream request November 7, 2012Low-Power Wireless Bus20

21 Evaluation Methodology LWB prototype – On top of Contiki, targeting Tmote Sky nodes Metrics – Data yield: fraction of packets received at sink(s) – Radio duty cycle: fraction of time with radio on November 7, 2012Low-Power Wireless Bus21

22 Evaluation Methodology Four testbeds Seven combinations of routing+MAC protocols November 7, 2012Low-Power Wireless Bus22 TestbedT WIST K ANSEI C ONET ITL OCAL LocationTU BerlinOhio State Univ.Univ. of SevilleETH Zurich Nodes (5 mobile)55 Diameter3 hops4 hops3 hops5 hops ScenarioProtocols Many-to-oneCTP+{CSMA, LPL, A-MAC}, Dozer Many-to-manyMuster+{CSMA, LPL} Mobile sink/sourcesBCP+CSMA, CTP+CSMA

23 Key Evaluation Findings (256 runs, 838 hours) The same LWB prototype: Is efficient under a wide range of traffic loads Supports mobile nodes with no performance loss Outperforms many-to-many state of the art Is minimally affected by interference or failures November 7, 2012Low-Power Wireless Bus23 The same LWB prototype: Is efficient under a wide range of traffic loads Supports mobile nodes with no performance loss Outperforms many-to-many state of the art Is minimally affected by interference or failures

24 sink L OCAL (5 hops): 1 sink, 54 sources generation period: 2 min High data yield (99.98 %) Low, even radio duty cycle (0.43 %) Average performance comparable to Dozer Outperforms contention- based protocols November 7, 2012Low-Power Wireless Bus24 Many-to-One: Light Traffic

25 sink L OCAL (5 hops): 1 sink, 54 sources 14 with varying generation period LWB promptly adapts to varying traffic load – Round period T – Slot allocation Additional complexity to make Dozer and LPL adaptable Low-Power Wireless Bus25November 7, 2012 Many-to-One: Fluctuating Traffic

26 (1 m/s) sink C ONET IT (3 hops): 1 sink, 25 sources generation period: {4, 2, 1} s LWB performs as in static scenarios (no topology-dependent state to update) Performance loss with BCP Static vs. Mobile Sink November 7, 2012Low-Power Wireless Bus26

27 Limitations Scalability – Linear with total amount of traffic – Outperforms state of the art at 52 pkt/s Impact of network diameter – Efficiency decreases in long networks – 14 hops: up to 300 streams with a period of 5 s November 7, 2012Low-Power Wireless Bus27

28 Conclusion: Simplicity = Efficiency LWB: Unified solution for diverse applications – Flooding for all communication – Time-triggered and centralized operation – Highly reliable and energy-efficient – Same performance with mobility November 7, 2012Low-Power Wireless Bus28 Self Managing Situated Computing ERC advanced grant

29 Questions? November 7, 2012Low-Power Wireless Bus29


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