Energy And Bandwidth Efficiency In Wireless Networks
Energy and BandwidthEfficiency in WirelessNetworksChanghun BaeWayne StarkUniversity of Michigan
Outline Introduction/Background Device/Physical Layer/Network LayerModels Performance Measure Numerical Results
Communication ProblemData Rate RSourceEncoderModPANoiseSinkDecoderDemodPower P,Bandwidth W
Energy-Bandwidth Efficiency Shannon showed there is a fundamentaltradeoff between energy efficiency andbandwidth efficiency for reliable communications R: Data rate (bits/second) P: Power (Joules/sec) N0: Noise power spectral density (Watts/Hz) W: Bandwidth (Hz)
Shannon’s ResultR/W: Bandwidth efficiency (bits/second/Hz)Eb/N0: Received energy per informationbit-to-noise power spectral density ratio(dB)
Shannon’s Result for Binary Input (BPSK) When the signal alphabet is restricted to binarythe capacity changes.
Energy-Bandwidth efficiency tradeoff
Energy-Bandwidth Efficiency Tradeoff
Shannon’s Assumption Linear amplifier (Ideal, 100% efficient)Point-to-point linkNo receiver processing energyInfinite delay
Relaxed Assumptions Nonlinear amplifier (energy efficiencydependent of drive level) Multihop network (take into accountpropagation) Receiver processing energy
Power Amplifier
Power Amplifier Power amplifier is most energy efficientwhen driven into saturation (largeoutput power). Power amplifier is least energy efficientat low input drive levels (low outputpower)
Propagation Characteristicsht180 phase changedehr
Propagation Characteristics Amount of energy necessary to go adistance de increases as de4.
Simplified Network ModelSR1R1R1 R1R2R3R3R4 R5R3R2R3 R2R1R6R1R2R2 R1R4 R4R3R5R2R6 R4R5R7deD
Performance Measure Without Spatial Reuse– Energy Efficiency– Bandwidth Efficiency– Transport Efficiency
Goal We want to find the relation betweenenergy consumption and bandwidthefficiency for a network taking intoaccount amplifier characteristics,propagation characteristics, receiverprocessing energy.
Goal We want to optimize over amplifierdrive level and the distance betweennodes in routing packets from thesource to the destination.
An Illustrative Example:Relay nodeRRSource node Longer link distance lower received SNR Lower data rate for each hop Less processing energy usage More efficient amplifier operation Shorter link distance higher received SNR Higher data rate for each hop More processing energy usage Less efficient amplifier operationSDDestination nodeRChoose route to Minimize energy usage Maximize bandwidth efficiency
RX Processing Energy Assume a fixed power consumption ofreceiver (Prp). Lower rate codes receiver is on fora longer period of time for a givennumber of information bits. Large number of hops large amountof receiver energy consumption."!
System Model Assumptions Power Amplifier Model Signal Attenuation Model
Power Amplifier Model Linear at low input powerlevels. Saturation at high powerlevels Constant amount ofpower turned into heat Ph 35mW, Psat 75mW, ρ 50 (17 dB), P1 1.5mWPcPo
Power Amplifier Model Radiated Power Consumed Power
Propagation ModelInverse power lawFor numerical results β 1, η 4.
Energy Consumption Encoder K information bits mapped intoN coded bits, rate R K/N. k hops between transmitter and receiver Ep energy per coded bit
Bandwidth Efficiency Beff expected number of correctlydecoded (end-to-end) bits per channeluse. Ps(R,Eb/N0) probability of packetsuccess per hop which depends on thecode rate R and the received SNR.
Physical Layer Models Threshold Model Coded Model Uncoded Model Pe 1-Ps
Physical Layer Model (AWGN)
Transport Efficiency Often it is desirable to have a single measure of anetwork performance. A measure of performance capturing energy use andbandwidth efficiency is the transport efficiency. Transport efficiency is the bits/second/Hz possibleper unit energy. The transport efficiency depends on the number ofhops, the code rate and the operation of the amplifier.
Energy-Bandwidth Efficiency(Single Hop)Ep .25µJ/symbol@50Ksymbolsper secondcorresponds to125 mWattsreceiverprocessingpower
Energy-Bandwidth Efficiency (multi-hop)
Transport Efficiency vs. Distance
Conclusion Without Spatial Reuse Transport efficiency decreases only inverse linear with distancefor any power propagation law, amplifier characteristic,coding/modulation technique. The constant depends on the coding, the propagation model,the amplifier model.Same results holds for any functional dependence of errorprobability on SNR, any amplifier model, propagationcharacteristics.
Spatial Reuse (Linear Case)Packet 3SN1Packet 2N2N3Packet 1N4N5ddeN6N7D
Spatial ReusePacket 3SN1Packet 2N2N3Packet 1N4N5ddeN6N7D
Spatial Reuse L minimum hop separation for concurrenttransmissions. Ω number of simultaneous transmissions. Accounting for interference from two othertransmissions with L 3 yields
Energy-Bandwidth Efficiency
Numerical Result
Transport Efficiency vs. Distance
Optimization Parameters withSpatial Reuse
Comparison of OptimumNumber of Hops
Conclusions The tradeoff between energy and bandwidthefficiency for wireless networks has been quantifiedincorporating amplifier model inefficiency,propagation and network routing. Results indicate relatively short distances, high ratecoding are desirable. Analysis technique easily applicable to fading andother modulation techniques as well as to specificcodes. Results might change (lower code rates) iftime/frequency selective fading is included but thefundamental relationship with distance does notchange.
Conclusions There are many extensions necessary– Include MAC layer– Include spatial distribution of nodes asopposed to infinite density of node– Include mobility (energy to update routingpath)– Find practical ways to achieveperformance limits.
Packet 3 Packet 2 Packet 1 d. Spatial Reuse S N1 N2 N3 N4 N5 N6 N7 D d e Packet 3 Packet 2 Packet 1 d. Spatial Reuse L minimum hop separation for concurrent transmissions. Ω number of simultaneous transmissions. Accounting for interference from two other transmissions with L 3 yields.
159 BA td 2 tni Chapter 4: Operational Ampliers 2. Bandwidth Learning Objectives: At the end of this topic you should be able to: recall that the bandwidth is the frequency range over which the voltage gain is greater than 1 2 (70%) of its maximum value; estimate this bandwidth from a frequency response curve; use the gain-bandwidth product (unity-gain bandwidth) to estimate bandwidth.
1. Log into the router interface and navigate to the Bandwidth Control menu: Advanced Bandwidth Control. 2. Insert the maximum bandwidth values into the appropriate Interface Bandwidth Setting fields (second menu on the page). In this example, only the WAN1 interface is being used. 3. Click the Add button under the Bandwidth Control Settings .
bandwidth (interface) IF-2 Cisco Nexus 7000 Series NX-OS Interfaces Command Reference, Release 4.2 OL-19821-01 bandwidth (interface) . Usage Guidelines The bandwidth command sets an informational parameter to communicate only the current bandwidth to the higher-level protocols; you cannot adjust the actual bandwidth of an interface using this .
erates as bandwidth calculator for such network [19]. First, we calculate proper number of circuits. After that, based on this calculation, the proper bandwidth is calculated for several VoIP codecs. The bandwidth calculation takes into con-sideration impact of many factors on the bandwidth such as: voice codecs, VAD, RTP compression.
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4.2.5 Energy efficiency can increase the energy access. 4.2.6 Energy efficiency can help increase energy security by reducing energy import and energy deficiency. 4.2.7 Energy efficiency can help in achieving the goals of sustainable development, in reducing carbon emission and environmental imbalance and in minimizing the negative effects of
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to apply in coming decades. The history of energy efficiency in the U.S. provides a vital reference and guide to any future national energy-efficiency strategy. The Alliance to Save Energy’s Commission on National Energy Efficiency Policy (ACNEEP) established a goal of doubling U.S. energy productivity by 2030 relative to 2011.
