PicoRadio Networks Opportunities and Challenges

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PicoRadio NetworksOpportunities and Challenges
Focus2000, June 26-27, Berkeley

• Jan M. Rabaey
• http//www.eecs.berkeley.edu/jan

In cooperation with the BWRC PicoRadio group.
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Envisioned PicoNode Platform

• Small footprint direct-downconversion R/F
  frontend
• Digital baseband processing implemented on
  combination of fixed and configurable datapath
  structures
• Protocol stack implemented on combination
  FPGA/reconfigurable state machines
• Embedded microprocessor running at absolute
  minimal rates

Embedded uP
Reconfigurable State Machines
FPGA
Dedicated DSP
Reconfigurable DataPath
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PicoRadio Challenge

• Develop meso-scale low-cost radios for
  ubiquitous wireless data acquisition that
  minimize power/energy dissipation
• Minimize energy (lt5 nJ/(correct) bit) for
  energy-limited source
• Minimize power (lt 100 mW) for power-limited
  source (enablingenergy scavenging)
• Target date 2004
• By using the following strategies
• self-configuring networks
• fluid trade-off between communication and
  computation
• aggressive low-energy architectures and circuits

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System Requirements and Constraints

• (from Exploratorium scenario)
• Large numbers of nodes between 0.05 and 1
  nodes/m2
• Cheap (lt0.5) and small ( lt 1 cm3)
• Limited operation range of network maximum
  50-100 m
• Low data rates per node 1-10 bits/sec average
• up to 10 kbit/sec in rare local connections to
  potentially support non-latency critical voice
  channel
• Crucial Design Parameter Spatial capacity (or
  density) 100-200 bits/sec/m2

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Some interesting numbers

• Energy cost of digital computation
• 1999 (0.25mm) 1pJ/op (custom) 1nJ/op (mproc)
• 2004 (0.1mm) 0.1pJ/op (custom) 100pJ/op
  (mproc)
• Factor 1.6 per year Factor 10 over 5 years
• Assuming reconfigurable implementation 1 pJ/op
• Energy cost of communication
• 1999 Bluetooth (2.4 GHz band, 10m distance)
• 1 nJ/bit transmission energy (thermal limit 30
  pJ/bit)
• Overall energy 170 nJ/bit reception / 150 nJ/bit
  transmission (!)
• Standby power 300 mW
• 2004 Radio (10 m)
• Only minor reduction in transmission energy
• Reduce transceiver energy with at least a factor
  10-50
• Trade-off
• _at_10m 5000 operations / transmitted bit
• _at_ 1m 0.5 operations / transmitted bit

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PicoJoule DSP for Sensor Applications

• Low Power Techniques
• Low voltage logic and memory
• Conditional clocks
• Variable precision processing
• Chip Details ISSCC 00
• 190K Transistors, 0.6mm CMOS
• VDD 1V
• Energy/Sample
• StrongARM-1100 11mJ
• Custom DSP 26pJ

Rajeevan Amirtharajah
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Advantages of CMOS

• Small size weight
• Estimated single chip transceiver die size using
  0.35 ? process is 10 mm2
• Includes processor, RAM, and ROM
• Low cost
• Current estimated die cost is 50 cents
• Low power stand-alone battery use
• Extremely low static power
• No off-chip high current filters or SAWs
• Estimated networked idling power is 30 ?w

• Rides the digital CMOS cost curve (Moores law ½
  every 1½ yrs)
• Large complexity from high levels of integration
• Software radio high functionality from
  processor/software control

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ENHANCED RANGE PICO-RADIO
Patch Antenna
RF Diode
BASE BAND IC
Up Link Modulation
RF Amps
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PICO-RADIO NETWORK
E2sin w2t
E3sin w3t
E1sin w1t
V(t) E12 E22 E32 Power addition of all
signals with synchronized modulation