Reconfigurable Communications Architecture for Adaptive …the reuse of the TV spectrum by unlicensed devices Spectrum Policy Reform. 3 ... Frequency (Ghz) Signal Power 3.1 10.6 Note:
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Reconfigurable Communications Architecture for Adaptive Radios
Reconfigurable Communications Architecture for Adaptive Radios
Ernest TsuiErnest TsuiPrincipal Engineer, Radio Communications Lab/Corporate TechnologPrincipal Engineer, Radio Communications Lab/Corporate Technology Groupy Group
Contributor: Ben Manny Contributor: Ben Manny Director, Radio Communications Lab, Director, Radio Communications Lab, Corporate Technology Group (CTG)Corporate Technology Group (CTG)
Reconfigurable Computing TutorialReconfigurable Computing TutorialInternational Symposium on SystemInternational Symposium on System--onon--Chip ConferenceChip Conference
The Ultimate Vision for Wireless AccessThe Ultimate Vision for Wireless Access??Ubiquitous Internet Connections for all Mobile Ubiquitous Internet Connections for all Mobile
Client DevicesClient Devices??Laptops, PDAs, Cell phones, and Tablet PCsLaptops, PDAs, Cell phones, and Tablet PCs
??AlwaysAlways--on connection on connection –– closed lid computingclosed lid computing
??New Paradigm for Wireless Basestations New Paradigm for Wireless Basestations ??Agility across Multiple Bands Agility across Multiple Bands ??MultiMulti--Network handNetwork hand--offs (WLAN, WWAN, WPAN)offs (WLAN, WWAN, WPAN)
??New business models, and access policiesNew business models, and access policies
How do we get there?How do we get there?How do we get there?
Spectrum UsageSpectrum Usage?Spectrum Policy Reforms?Spectrum Policy directional change?Transition from usage base to rule base?Sub-leasing of licensed spectrum ?Advances in radio technology e.g. UWB and Software
Defined Radios?Fair & equal access, Unlicensed bands
?Radio Certification Challenges?Partitioned Module Certification (certify once & radio adapts
operation for compliance anywhere)
?Regulation Changes?Working with the FCC on Spectrum reform for many years?International coordination of regulations for UWB solutions?Recent involvement in response to FCC Notice of Inquiry about
the reuse of the TV spectrum by unlicensed devices
?Dynamic partitioning of spectrum?Can cut across any spectrum?FCC sets policy or “rules” to govern usage and priority?Example – unlicensed use of vacant TV bands?Example – prioritized usage e.g. Search & Rescue
?Prioritize the usage of spectrum?Can cut across any spectrum?FCC sets policy or “rules” to govern usage and priority?Example – Search & Rescue has priority?Example – unlicensed TV band
440MHz
Available channels in the TV NOI
Frequency (Ghz)
EmittedSignalPower
… 23 28 33…..
~800MHz
…
San Jose
47
Safety Services
52+
….. 38 41..
Note: not to scale
Data is for illustrative purposes only.
Spectrum Policy Reform
Technology is allowing better and more efficient spectrum usage and influencing
spectrum policy.
Technology is allowing better and more efficient spectrum usage and influencing
?Define a UWB-based radio platform that becomes the PC/CE/mobile industry standard?Enable a single low cost radio?Drive UWB regulatory approvals?Facilitate compatibility and co-existence
??Must sense or be Must sense or be cognitivecognitive of the environmentof the environment??Other user interference, multipath, noise, etc.Other user interference, multipath, noise, etc.??TimeTime--variationsvariations
??Must be Must be Intelligent Intelligent to analyze the situation and find to analyze the situation and find the optimal communications protocol, frequency, the optimal communications protocol, frequency, channel, etc.channel, etc.
??Must Must reconfigure reconfigure for the channel and protocol for the channel and protocol requiredrequired
??And…constantly And…constantly adaptadapt to mobile changing to mobile changing environmentsenvironments
Present Status of Soft RadiosPresent Status of Soft Radios?? Prior Infrastructure ApproachesPrior Infrastructure Approaches??DSP + ASICDSP + ASIC??Inflexible ASIC and Costly DSPInflexible ASIC and Costly DSP
??DSP + Closely Coupled AcceleratorsDSP + Closely Coupled Accelerators??Increased Power and Costly DSPIncreased Power and Costly DSP
??ReconfigurableReconfigurable??Hard to ProgramHard to Program??CostlyCostly
??High PowerHigh Power??Granularity problem has not been completely solvedGranularity problem has not been completely solved
??Need Evolved Architecture Need Evolved Architecture
Wireless RequirementsWireless Requirements??Seamless Client RoamingSeamless Client Roaming??Two to three concurrent wireless protocols selected from Two to three concurrent wireless protocols selected from
a set of five to fifteen protocolsa set of five to fifteen protocols
??Selected 802.11a and WCDMA as the models of Selected 802.11a and WCDMA as the models of computationally intensive protocolscomputationally intensive protocols
??Size (< tens of mmSize (< tens of mm22))
??Very Low Power (several hundred mW)Very Low Power (several hundred mW)??Digital Baseband is < 10% of total PHY powerDigital Baseband is < 10% of total PHY power
??Reconfigurable to allow Si ReReconfigurable to allow Si Re--useuse
??ScaleableScaleable
??Converging protocols to OFDM or CDMA or hybridConverging protocols to OFDM or CDMA or hybrid
General Architectural Issues (I)General Architectural Issues (I)??Low power requires a Low power requires a highly distributedhighly distributed (e.g. (e.g.
spatially multiplexed) architecturespatially multiplexed) architecture??Low voltage helps quadratically lower powerLow voltage helps quadratically lower power??Low clock frequency linearly lowers powerLow clock frequency linearly lowers power??Large size penalties associated with spatially Large size penalties associated with spatially
distributed elements must be avoideddistributed elements must be avoided??What is the low power What is the low power interconnectinterconnect strategy?strategy?
??Small Size requires a highly Small Size requires a highly timetime--multiplexed multiplexed architecturearchitecture??Clock frequency is increased and possibly voltageClock frequency is increased and possibly voltage??Memory is also increasedMemory is also increased
??Conflicting requirements for low power Conflicting requirements for low power and small size (other than leakage)and small size (other than leakage)
General Architectural Issues (II)General Architectural Issues (II)
??FlexibilityFlexibility (less) is the other variable that can (less) is the other variable that can reduce both size and powerreduce both size and power??Determine the size of a Significant Computational Determine the size of a Significant Computational
Unit (Aop)Unit (Aop)
??This equals the Granularity for a true This equals the Granularity for a true reconfigurable architecturereconfigurable architecture??FPGA granularity is smaller (LUT) than the FPGA granularity is smaller (LUT) than the
significant computational unitsignificant computational unit??Pick the right “granularity”Pick the right “granularity”??Larger gives more power/area efficiencyLarger gives more power/area efficiency??Less gives more flexibilityLess gives more flexibility
How Do the Architectures Compare?Multi-User Detector (Adaptive Filter-like) BenchmarkHow Do the Architectures Compare?Multi-User Detector (Adaptive Filter-like) Benchmark
Contributors:Contributors:Inching Chen, Tony Chun, Ram Krishnamurthy, Rich Inching Chen, Tony Chun, Ram Krishnamurthy, Rich Nicholls, Steve Pawlowski, Lee Snyder, Bart Zeydel Nicholls, Steve Pawlowski, Lee Snyder, Bart Zeydel
??Exponentially increasing computational complexities Exponentially increasing computational complexities demand more MOPsdemand more MOPs
??Moore’s Law adding Transistors (MOPs) but Moore’s Law adding Transistors (MOPs) but Active Active powerpower per MIP is now also increasingper MIP is now also increasing
??More than Battery Capacity trendMore than Battery Capacity trend
??Most of the energy may be used in Wireless Standby Most of the energy may be used in Wireless Standby modes due to Submicron Leakagemodes due to Submicron Leakage
??Leakage PowerLeakage Power is proportional to Sizeis proportional to Size
??Size may also be a constraintSize may also be a constraint
??Need more MOPs/watts Need more MOPs/watts andand MOPs/mmMOPs/mm22
??Must Decrease Watts/MOPs as in the past Must Decrease Watts/MOPs as in the past –– but how?but how???Active Watts/MIPs ~ Active Watts/MIPs ~ Granularity Granularity x x Load CapacitanceLoad Capacitance x x VVdddd
?Vdd decrease is being limited by leakage considerations??Load Capacitance (formerly decreasing with feature size) may be Load Capacitance (formerly decreasing with feature size) may be
increasing in the futureincreasing in the future??Granularity defined as size of the fundamental arithmetic unit pGranularity defined as size of the fundamental arithmetic unit plus lus
overhead (memory, interconnect, etc.) overhead (memory, interconnect, etc.) This must DECREASE with This must DECREASE with future Architecturesfuture Architectures
??Granularity Reduction OptionsGranularity Reduction Options??Reduce memory Reduce memory –– via spatially distributed processing vs time via spatially distributed processing vs time
multiplexingmultiplexing??Reduce overhead (e.g., per cycle instruction decoding, etc.) witReduce overhead (e.g., per cycle instruction decoding, etc.) with h
“reconfigure and forget datapath” architectures“reconfigure and forget datapath” architectures??More efficient implementations of fundamental datapath unitsMore efficient implementations of fundamental datapath units??Efficient Interconnect ArchitectureEfficient Interconnect Architecture
??Future Requirements for MOPs and Battery Future Requirements for MOPs and Battery LifeLife??Require new Architectures that focus on low active power Require new Architectures that focus on low active power
and standby power (size reduction and leakage reduction)and standby power (size reduction and leakage reduction)
??Reduction of Granularity (or fundamental Reduction of Granularity (or fundamental arithmetic element size) is keyarithmetic element size) is key??Use ASIC Use ASIC –– type Spatial Multiplex Methods that can type Spatial Multiplex Methods that can
“reconfigure and forget”“reconfigure and forget”
??Efficient Connections of Granular computation modulesEfficient Connections of Granular computation modules
Architecture Selection CriteriaArchitecture Selection Criteria??Define type of protocols desired, power, size, Define type of protocols desired, power, size,
and performance requirementsand performance requirements??Evaluate the protocol algorithmsEvaluate the protocol algorithms??Allows proper flexibility limitation of the processing Allows proper flexibility limitation of the processing
elementselements??Only the flexibility required, e.g. filter length Only the flexibility required, e.g. filter length
variation, etc.variation, etc.
??Architect the processing elementsArchitect the processing elements??Few selected typesFew selected types??Clock frequency dependent on load and processClock frequency dependent on load and process
??Connect elementsConnect elements??Scalable manner, e.g., mesh or similar approach Scalable manner, e.g., mesh or similar approach
Architecture ApproachArchitecture Approach??Interconnect with Nearest Neighbor MeshInterconnect with Nearest Neighbor Mesh??Eliminates High Speed (and power) buses [J. Rabaey, Silicon Eliminates High Speed (and power) buses [J. Rabaey, Silicon
Architectures for Wireless, Hotchips 2001 Tutorial]Architectures for Wireless, Hotchips 2001 Tutorial]
??PHY connections are 95% nearest neighborPHY connections are 95% nearest neighbor
??Heterogeneous Processing Elements (PEs)Heterogeneous Processing Elements (PEs)??Domain specific processors are more efficient (less flexible)Domain specific processors are more efficient (less flexible)??With the right granularityWith the right granularity
??Number of Processing Elements Number of Processing Elements ??Driven by:Driven by:
– Computational Load– Activity Factors (Standby vs Active)– Size and Power Constraints– Feature parameters (e.g., Average Load Capacitance, Vdd, etc.)
??Clock Frequency Choice Clock Frequency Choice –– optimal one for each situationoptimal one for each situation
?? There is an optimum FThere is an optimum Fclkclk for a fixed Afor a fixed Aopop
??((AAopop is the fundamental processing size)is the fundamental processing size)??Optimum meets Size and Computational requirements and Optimum meets Size and Computational requirements and
minimizes power for the aboveminimizes power for the above??Higher FHigher Fclkclk increases power, lower Fincreases power, lower Fclkclk increases area and increases area and
interconnect powerinterconnect power?? There a similar optimum as AThere a similar optimum as Aopop is variedis varied??As AAs Aopop decreases decreases –– interconnect Power increases exponentially interconnect Power increases exponentially
??Simpler elements must be connected in a more complex manner to Simpler elements must be connected in a more complex manner to retain flexibilityretain flexibility
??As AAs Aopop increases increases -- the voltage requirement (and Power) increases the voltage requirement (and Power) increases ??More complex element requires timeMore complex element requires time--multiplexingmultiplexing
?? Thus, is there a globally “good” design?Thus, is there a globally “good” design???Conjecture:Conjecture:
??Determine the Minimum Aop (for the flexibility desired) and findDetermine the Minimum Aop (for the flexibility desired) and find the the optimum Foptimum Fclkclk
Reconfigurable Communication ArchitectureUbiquitous wireless communication across multiple protocols
A scalable mesh interconnect of heterogeneous processing elements (PEs):? Configurable basebands for multiple (concurrent) PHY/MAC operation? Power and Size conserving when compared to “multiple” dedicate d cores or
“traditional” SDR (S/W defined radio) approaches? Tools for simple programming and portability to different arrays of elements
Overall SummaryOverall Summary??Spectrum is available but we need to “find it”Spectrum is available but we need to “find it”??Technology is allowing better and more efficient spectrum Technology is allowing better and more efficient spectrum
usage and influencing spectrum policy.usage and influencing spectrum policy.
??Geographic, spatial, frequency, time are all examples of the Geographic, spatial, frequency, time are all examples of the dimensionsdimensions
??Cognitive or Adaptive Radios are desirableCognitive or Adaptive Radios are desirable??To find spectrum and understand the available capacity of each To find spectrum and understand the available capacity of each
slice of spectrumslice of spectrum??UWB multiUWB multi--band OFDM approach will facilitate compatibility and band OFDM approach will facilitate compatibility and
coco--existence.existence.
??Cognitive Radios allow for ubiquitous wireless communication Cognitive Radios allow for ubiquitous wireless communication across multiple protocols and spectrum.across multiple protocols and spectrum.
??Reconfigurable or Adaptive Radios enableReconfigurable or Adaptive Radios enable??Lower cost (reLower cost (re--use Si) and lower energy (leakage) for low use Si) and lower energy (leakage) for low
??Also enable adaptivity to optimum modulation, demodulation, Also enable adaptivity to optimum modulation, demodulation, and a smart antenna configurations for the given environment and a smart antenna configurations for the given environment