Outline Paper presentation – Ultra-Portable Devices • Introduction Paper: • Related work • Wake-Up-Frame Xiaolei Shi, Thomas Sturm, et al. Wake-Up-Frame Scheme for Ultra Low Power Transceivers. • Comparison Globecom (vol. 6), pp. 3619-3623, Nov 2004. • Discussion • Simulation • Summary Presented by: Carl Bryant 09-08-21 Paper Presentation - Ultra Portable Devices 1 09-08-21 Paper Presentation - Ultra Portable Devices 2 Introduction Introduction • Wireless sensor networks (WSN) etc. • Transceiver power hungry – keep on as little as possible • Networking with small cheap devices • Sparse communication (mostly) • Receiver off – node deaf • Battery time important • Strategy required to make/receive connection with minimum waste of power • WUP = Wake-Up-Preamble • Passive receiver would allow immediate wake up, but • WUF = Wake-Up-Frame implementation and use problematic Wake up! Zzzz... 09-08-21 Paper Presentation - Ultra Portable Devices 3 09-08-21 Paper Presentation - Ultra Portable Devices 4
Related work Related work • WiseMAC* • Limitations: • Transmission is preceeded by a long preamble (Wake-Up-Preamble, WUP) • Broadcasts must still use full length WUP • Receiver periodically wakes up to check for transmission • Clock instability will degrade sync. over time • Transmission detected from signal strength • Listening nodes must stay awake the full duration of the • Sampling schedule piggybacked on last received packet to WUP, even those not addressed allow shorter WUP in subsequent communication *El-Hoiydi, A.; Decotignie, J.-D., "WiseMAC: an ultra low power MAC protocol for the downlink of infrastructure wireless sensor networks," Computers and Communications, 2004. Proceedings. ISCC 2004. Ninth International Symposium on , vol.1, no., pp. 244-251 Vol.1, 28 June-1 July 2004 (among Nafiseh’s presentation papers) 09-08-21 Paper Presentation - Ultra Portable Devices 5 09-08-21 Paper Presentation - Ultra Portable Devices 6 Wake-Up-Frame Comparison, WUP/WUF • Idea : Replace preamble with smarter transmission containing • Hardware example for comparison more information • Pretransmission is divided into many short frames each containing a MAC frame and remaining duration of WUF • Allows listening nodes to make early wake/sleep desicion • Allows recipient to sleep until data is transmitted • Additional idea : Use different data rate for pretransmission • Data rate detection supposedly fast and easy • Complements signal strength detection to minimize unneccesary wakeups 09-08-21 Paper Presentation - Ultra Portable Devices 7 09-08-21 Paper Presentation - Ultra Portable Devices 8
Comparison, WUP Comparison, WUP ’Worst’ case – receiver sleeps just before start of WUP Receiver wakes up early – long wait Determines shortest WUP required for certain detection Receiver fully on while waiting – wasted power 09-08-21 Paper Presentation - Ultra Portable Devices 9 09-08-21 Paper Presentation - Ultra Portable Devices 10 Comparison, WUF Discussion • Succeeds in making listening nodes work less, but transmitting node still needs to work the full WUF duration (long pretransmission also limits channel capacity). • Introducing duplex would allow receiver to send ACK as suggested in XMAC* • Does WUF still have any use? • Broadcasting • For a node with good power supply a long transmission matters less • Different pretransmission data rate useful? *Michael Buettner, Gary V. Yee et. al. “X-MAC: a short preamble MAC protocol for duty-cycled wireless sensor networks”, Receiver waking up early can go back to sleep SenSys '06: Proceedings of the 4th international conference on Embedded networked sensor systems (2006), pp. 307-320 Receiving node saves power (among Nafiseh’s papers) 09-08-21 Paper Presentation - Ultra Portable Devices 11 09-08-21 Paper Presentation - Ultra Portable Devices 12
Discussion Simulation • Paper argues that power savings increase with increased • Simulations of different scenarios to judge if WUF has traffic. noticable advantage over WUP • For frequent traffic a WiseMAC based WUP scheme would • Data packets generated by a Poisson process with arrival have up to date sampling schemes, reducing wasted power rate λ (packets/s) • Data frames @ 100kbit/s, WUF @ 70kbit/s • Incidentally the authors later got another paper adding this feature to the WUF scheme* • Caution: Unknow if WUP scheme includes sampling schedule information *Xiaolei Shi; Stromberg, G., "SyncWUF: An Ultra Low-Power MAC Protocol for Wireless Sensor Networks," Mobile Computing, IEEE Transactions on , vol.6, no.1, pp.115-125, Jan. 2007 09-08-21 Paper Presentation - Ultra Portable Devices 13 09-08-21 Paper Presentation - Ultra Portable Devices 14 Simulation Simulation • 3V, 1000mAh battery assumed Power consumption without traffic 09-08-21 Paper Presentation - Ultra Portable Devices 15 09-08-21 Paper Presentation - Ultra Portable Devices 16
Simulation Simulation Master-Slave, unicast Master-Slave, broadcast 09-08-21 Paper Presentation - Ultra Portable Devices 17 09-08-21 Paper Presentation - Ultra Portable Devices 18 Simulation Simulation Peer-To-Peer communication in a flat topology Peer-To-Peer, unicast 09-08-21 Paper Presentation - Ultra Portable Devices 19 09-08-21 Paper Presentation - Ultra Portable Devices 20
Simulation Summary • Paper builds on Wake-Up-Signal type network with duty- cycled reception, like WiseMAC • Unnecessary listening is avoided by including additional information and by making the pretransmission distinct • Simulations seem to indicate significant potential savings • There may be solutions that improve on this, but this scheme may still have merit for broadcasting and transmission from ’high power’ nodes • Using different data rate for pretransmission might have general use Peer-To-Peer, broadcast 09-08-21 Paper Presentation - Ultra Portable Devices 21 09-08-21 Paper Presentation - Ultra Portable Devices 22 09-08-21 Paper Presentation - Ultra Portable Devices 23
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