1 / 56

Emerging Radio …and the World

Emerging Radio …and the World. Aggelos Bletsas Department of Electronic and Computer Engineering, Technical University of Crete (TUC), Greece. Collaborators: Prof. Sahalos, Prof. Win, Prof. Lippman & Dr. Dimitriou. TUC Telecom Seminars 2008-2009 June 1, 2009. Outline. RFIDs Emergency Radio

nitesh
Download Presentation

Emerging Radio …and the World

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Emerging Radio …and the World Aggelos BletsasDepartment of Electronic and Computer Engineering,Technical University of Crete (TUC), Greece Collaborators: Prof. Sahalos, Prof. Win, Prof. Lippman & Dr. Dimitriou TUC Telecom Seminars 2008-2009 June 1, 2009

  2. Outline RFIDs Emergency Radio Emerging Relaying in Wireless Access Networks Education and integration TUC Telecom Seminars 2008-2009

  3. Backscatter Radio/RFIDs are used everywhere! TUC Telecom Seminars 2008-2009

  4. Brief Intro: Basic Principle Tag Reader G. Vannucci, A. Bletsas and D. Leigh, "A Software-Defined Radio System for Backscatter Sensor Networks", IEEE Transactions on Wireless Communications (TWC), Vol. 7, No. 6, pp. 2170-2179, June 2008. • Communication from Tag to Reader = Backscatter Radio = = binary modulation on tag antenna-tag load reflection coefficient! TUC Telecom Seminars 2008-2009

  5. Problem Formulation • Focus on Tag-to-Reader Communication • For given tag antenna, what are the ``optimal’’ tag loads Z1(for bit ‘0’), Z2 (for bit ‘1’)? TUC Telecom Seminars 2008-2009

  6. Prior Art: focus on minimum scattering antennas only • [Nikitin et al Electronics Letters 2007]: “Since the scattered field is proportional to the complex current in the antenna…”, the system designer “should maximize |Γ1-Γ2|2…”(where Γi is the reflection coefficientfor load Zi) • As stated by Nikitin et al, this is only true for minimum scattering antennas. • We derive the solution for the general tag antenna case. TUC Telecom Seminars 2008-2009

  7.  Basic Quantities E0: Antenna specific… As: Tag Antenna Structural Mode Parameter σi: Radar Cross Section (RCS) at load ZL=Zi TUC Telecom Seminars 2008-2009

  8.  ``Optimality’’ Definition: Constraint 1 • Must maximize average backscattered (carrier) power per bit P0: • P0 σ1 + σ2 (scalar) • σi: Radar Cross Section (RCS)at load ZL=Zi TUC Telecom Seminars 2008-2009

  9.  ``Optimality’’ Definition: Constraint 2 • Must minimize variance of Backscattered (carrier) power Var(P0), due to different bits for M-bit message: • Var(P0)[(σ1- σ2)2]/M(scalar) • M≥96 for Gen2. We (can) drop this constraint! TUC Telecom Seminars 2008-2009

  10. ``Optimality’’ Definition: Constraint 3 • Must minimize Reader bit-error probability (BER): TUC Telecom Seminars 2008-2009

  11. Design Example for Given Tag Antenna: Passive Tag • Solutions I and II provide the same error detection probability (Constraint 3). • Solution II provides higher backscattered carrier power per bit (Constraint 1). TUC Telecom Seminars 2008-2009

  12. Tag Design • Experimentation with meander-type antennas, proposed in the literature for passive tags… • Battery-assisted tags: no need for power transfer => different problem… TUC Telecom Seminars 2008-2009

  13. Tag Design and Experimentation • Prototype… • Design… • Radar Cross Section can be increased compared to passive case (perfect matching). TUC Telecom Seminars 2008-2009

  14. Experimentation • Carrier transmitted… • Tag modulating waveform… • Received (backscattered) waveform… TUC Telecom Seminars 2008-2009

  15. Remarks BUSTED • Tag design should maximize |Γ1-Γ2|only… • Research is over in RFIDs… • Selection of best reflection coefficients was given for any As (and tag antenna, not necessarily minimum scattering). • As can be easily computed in closed-form, given measurements of scalar RCS! BUSTED Method for closed-form calculation of As was omitted due to time constraints TUC Telecom Seminars 2008-2009

  16. Current Focus • Read Range (frequency dependent) • Communication throughput (bps/sensor) • Scalability (number of RFID sensors) => anti-collision ability • Reading speed (number of sensors/sec): ~ 40 tags/sec current state of the art • Antenna size (as small as possible) • Packaging material & environment (affect reader/tag coupling) • Efficient tag manufacturing & programming • Tag/Reader Cost • Integration: addressing all (or most of) the above in an application! TUC Telecom Seminars 2008-2009

  17. Scalability of Backscatter Sensor Networks • For agricultural fields, sensor density is large (~1-1.5 sensor/m2)… • Large number N of sensors is needed… • Required bandwidth is proportional to Nδ… • Anti-collision performance depends on available bandwidth …tradeoff between anticollision performance and N (or bandwidth) TUC Telecom Seminars 2008-2009

  18. Why not Zigbee (with 802.15.4)? 5-10$ each in quantity of 1000) – [however, the target is 1$ per node] tx current ~30 mA @ 10 dBm, rx current ~40 mA. Speed 20kbps (868 Mhz), 40kbps (900+MHz), up to 240 kbps (2.4GHz) – routing overhead? “ZigBee Architecture Overview”, available from ZigBee.org cost of an MCU (1.5$(each) in quantity of 1![however, the target is 0.1$ per node with ASIC] tx current ~0.6 mA @ 1 MHz, no receiver Speed a few bps – no routing overhead TUC Telecom Seminars 2008-2009

  19. Reader Antenna Capacity Enhancement Beamforming antenna: Tag Collision occurs when tags close in modulating frequency AND close in geographical space… => Larger number of sensors for given bandwidth (compared to omni)! TUC Telecom Seminars 2008-2009

  20. fading uncertainty location uncertainty observation direction uncertainty antenna directivity pattern modulation BSN Capacity Enhancement with smart Reader Antenna… Edge Collision probability is analytically derived as a function of various uncertainties TUC Telecom Seminars 2008-2009

  21. Anti-Collision with Reader Antennas… • modulations utilized in Gen2: inappropriate for high-density, extended range semi-passive tags… • … that is due to round trip nature of backscatter com… • quantified collision for any modulation, number of tags and given spectrum… • (useful for epc class 3 standard) • A. Bletsas, S. Siachalou, J.N. Sahalos, "Anti-collision Tags for Backscatter Sensor Networks", 38th European Microwave Conference (EuMC), October 2008, Amsterdam, Netherlands. • Bletsas, J.N. Sahalos, "Antenna Enhancements for Backscatter Sensor Networks", COST Antenna Systems & Sensors for Information Technology Societies (ASSIST) Workshop, April 2008, Limassol, Cyprus. • A. Bletsas, S. Siachalou and J.N. Sahalos, "Anti-collision Backscatter Sensor Networks", submitted June 2008, IEEE Transactions on Wireless Communications (TWC). TUC Telecom Seminars 2008-2009

  22. Reader Antenna Design in Practice Butler Matrix Feeding Network (BFN) • E. Vaitsopoulos, A. Bletsas, J.N. Sahalos, "On the RFID Design with Passive Tags and a Butler Matrix Reader", 13th Biennial IEEE Conference on Electromagnetic Field Computation (CEFC), May 2008, Athens, Greece. TUC Telecom Seminars 2008-2009

  23. 6-month focus: RFID in HealthcareMotivation = Medical Errors + Electronic Inventory Control • Paper-based environments: medical errors approach 40% • In-hospital Medication errors: 44,000 deaths per year in the US, 700 deaths per year in Canada. (Institute of Medicine, National Academic Press, 1999) • Theft of equipment/supplies: $4,000 per hospital bed each year ($3.9 billion annually in the US) • Asset Tracking: One third of personnel time is wasted in searching. ~10% of inventory is lost annually. TUC Telecom Seminars 2008-2009

  24. RFID Reader Antenna Transmit Diversity z slice, z-field z slice, z-field x slice, z-field x slice, z-field 1 Reader Antenna 2 Reader Antennas with passive splitter (3-dB Tx power loss per antenna) TUC Telecom Seminars 2008-2009

  25. References G. Vannucci, A. Bletsas, D. Leigh, "Implementing Backscatter Radio for Wireless Sensor Networks", IEEE Personal Indoor Mobile Radio Communications Conference (PIMRC), September 2007, Athens, Greece, pp. 1-5. G. Vannucci, A. Bletsas and D. Leigh, "A Software-Defined Radio System for Backscatter Sensor Networks", IEEE Transactions on Wireless Communications (TWC), Vol. 7, No. 6, pp. 2170-2179, June 2008. E. Vaitsopoulos, A. Bletsas, J.N. Sahalos, "On the RFID Design with Passive Tags and a Butler Matrix Reader",13th Biennial IEEE Conference on Electromagnetic Field Computation (CEFC), May 2008, Athens, Greece. A. Bletsas, J.N. Sahalos, "Antenna Enhancements for Backscatter Sensor Networks", COST Antenna Systems & Sensors for Information Technology Societies (ASSIST) Workshop, April 2008, Limassol, Cyprus. A. Bletsas, S. Siachalou, J.N. Sahalos, "Anti-collision Tags for Backscatter Sensor Networks", 38th European Microwave Conference (EuMC), October 2008, Amsterdam, Netherlands. A. Bletsas, S. Siachalou and J.N. Sahalos, "Anti-collision Backscatter Sensor Networks", IEEE Transactions on Wireless Communications (TWC), submitted June 2008. A. Bletsas, A. G. Dimitriou, J. N. Sahalos, “Improving Backscatter Radio Tag Efficiency“, COST RF/Microwave Communication Subsystems for Emerging Wireless Technologies (RFCSET) Workshop, April 2009, Brno, Czech Republic. A. Polycarpou, A.G. Dimitriou, A. Bletsas and J.N. Sahalos, "RFID in Healthcare", COST Antenna Systems & Sensors for Information Technology Societies (ASSIST) Workshop, May 2009, Valencia, Spain. TUC Telecom Seminars 2008-2009

  26. Outline RFIDs Emergency Radio Emerging Relaying in Wireless Access Networks Education and integration TUC Telecom Seminars 2008-2009

  27. Motivation ~2001 @ MIT: Distributed phased arrays… Code name: “Marblehead Island problem” (note: Marblehead is north of Boston) TUC Telecom Seminars 2008-2009

  28. Problem Formulation (1) Very stringent requirements as in Emergency Radio • 2009: make it more interesting…. • No CSI at the transmitters… • No feedback from the destination… • No carrier sync availability… TUC Telecom Seminars 2008-2009

  29. Intuition TUC Telecom Seminars 2008-2009

  30. Problem Formulation (2) TUC Telecom Seminars 2008-2009

  31. Alignment Probability Calculation TUC Telecom Seminars 2008-2009

  32. Alignment Probability Results TUC Telecom Seminars 2008-2009

  33. Steady-State Alignment Probability Phase Offset Independence TUC Telecom Seminars 2008-2009

  34. Steady-State Alignment Probability Clock Frequency Skew Independence TUC Telecom Seminars 2008-2009

  35. Transient Alignment Probability Clock Frequency Skew Dependence TUC Telecom Seminars 2008-2009

  36. …and finally: beamforming gain and delay Example: fc=2.4 GHz R = 1 Mbps => Ts = 1 μsec Tc > 100 μsec => u < 1.25 km/sec @ φ0 = π/4 => Lbf = 8.6 dB => ~4 symbols out 100 Thus, effective rate: = 1 Mbps x 4/100 @ Lbf = 8.6 dB = 40 kbps @ Lbf = 8.6 dB! 8.6 dB in power is a factor of 7.24 (!!!) TUC Telecom Seminars 2008-2009

  37. Remark (1) • “Distributed Beam-forming REQUIRES Carrier Synchronization and/or feedback from the destination”. • We provided zero-feedback, zero-CSI distributed beam-forming, based on unsynchronized carriers! • The proposed scheme could complement rescue workers (emergency radio) or reachback communication in wireless networks (e.g. low-cost sensor networks). BUSTED TUC Telecom Seminars 2008-2009

  38. Remark (2) “Marblehead Island problem”  “Marathi Island Problem” TUC Telecom Seminars 2008-2009

  39. References A. Bletsas, A. Lippman and J.N. Sahalos, "Simple, Zero-Feedback, Distributed Beamforming with Unsynchronized Carriers", submitted April 2009, IEEE Journal on Selected Areas of Communication (JSAC), Special Issue on Simple Sensor Networking Solutions. A. Bletsas, A. Lippman and J.N. Sahalos, "Simple, Zero-Feedback, Distributed Beamforming for Emergency Radio", submitted April 2009, IEEE ISWCS 2009, Tuscany, Italy. TUC Telecom Seminars 2008-2009

  40. Outline RFIDs Emergency Radio Emerging Relaying in Wireless Access Networks Bibliometrics & the Hirsch Index Education trends and integration TUC Telecom Seminars 2008-2009

  41. The problem One source, K half-duplex relays, several destinations… Quasi-static SLOW fading (no temporal diversity)… Network (global) CSI at relays or destinations: NOT AVAILABLE… Low-complexity protocol: reduced coordination overhead… (it’s a network problem) Low-complexity receivers, cheap radios…(in-band multiple transmissions = noise) TUC Telecom Seminars 2008-2009

  42. t Approach • …always exactly two (2)in-band transmissions: • Source-to-destination • “best” relay-to-DIFFERENT destination! • “best” relay: selected opportunistically, reactively, in a distributed manner at MAC (no global CSI anywhere in the network) • “best” relay: best for epoch n-1, interfering for next epoch n TUC Telecom Seminars 2008-2009

  43. t Approach • “best” relay: best b for epoch n-1, interfering i for next epoch n. • b≠i due to half duplex radios… • Scheduling invariant… • “Reactive” opposed to “Proactive”: The latter is energy-efficient but needs additional CSI. Efficient MAC for opportunistic selection: “A Simple Cooperative Diversity Method based on Network Path Selection”, IEEE JSAC, March 2006. • Optimality proof for DF Relays: “Cooperative Communications with Outage-Optimal Opportunistic Relaying”, IEEE TWC, September 2007. Major difference with prior art: interference is allowed, NO network/superposition/dirty-paper coding (low complexity protocol/receivers)! TUC Telecom Seminars 2008-2009

  44. Outage probability given specific interfering relay Analysis discrete, narrow-band, constant total tx power,flat-fading model under Rayleigh Fading. 2. reactive, opportunistic selection: 3. performance dependent on previous Epochs! (non-memoryless) => fix this by using bounds! TUC Telecom Seminars 2008-2009

  45. Selection Receiver (SR): simplest receiver, other simple receivers are also possible! Signal of interest (SOI) and Interfering Signal (IS)are fully correlated!!! Analysis • Need to compute all relevant outage probs, conditioned to (any) interfering relay i. • Example 1: • Example 2 (…little more involved): TUC Telecom Seminars 2008-2009

  46. Results • …(more than) acceptable performance with weak or no SD link, weak inter-relay links! TUC Telecom Seminars 2008-2009

  47. Outage probability plateau! Results • Opportunistic Relaying provides cooperative diversity and engineers the required outage probability plateau! • …thus, more efficient use of spectrum, no need for scheduling (from source) delays! TUC Telecom Seminars 2008-2009

  48. Remarks • Notion of useful relays in IaOR is redefined: “relays with strong paths towards source and destinations but weak links with each other!” • Opportunistic, reactive relaying engineers the appropriate plateau to mitigate “interference” and reduce scheduling delays! • No need for fancy coding (superposition or dirty-paper)……but need for efficient opportunistic selection (examples exist, more research is required and welcomed! ) TUC Telecom Seminars 2008-2009

  49. Low complexity switched-beam antenna designs are possible [Vaitsopoulos, Bletsas and Sahalos, IEEE CEFC 2008] Discussion • “relays with strong paths towards source and destinations but weak links with each other!” • Approach 1: find such relays given existing relaying densities in urban environments! “Existing Urban Environments provide wifi terminal densities on the order of 1000 nodes/km2” [Jones and Liu 2007]. • Approach 2: use directive antennas AT THE RELAYS! TUC Telecom Seminars 2008-2009

  50. Classic relaying vs classic network coding vs 2-way physical network coding Classic network coding (classic) 2-way physical network coding (PNC) Classic relaying [figure from Katti, Gollakota and Katabi, ACM Sigcomm 2007] TUC Telecom Seminars 2008-2009

More Related