Reducing the Data Rate X Increase the duty cycle Collect only above-threshold data Amplitude changes only Data compression
Reducing the Data Rate • Increase the Duty Cycle • Collect only above-threshold data • Amplitude changes only • Data compression
Link design process 1. Define Requirements for each link 2. Design each Link Select frequency Select modulation coding apply antenna size beam width constraints Estimate atmospheric rain attenuation Estimate received noise, interference power Calculate required antenna gain transmitter power 3. Size the payload Payload antenna configuration, size mass Estimate transmitter mass power Estimate payload mass power
Link Design Process 1. Define Requirements for each link 2. Design Each Link – Select frequency – Select modulation & coding – Apply antenna size & beam width constraints – Estimate atmospheric, rain attenuation – Estimate received noise, interference power – Calculate required antenna gain & transmitter power 3. Size the Payload – Payload antenna configuration, size & mass – Estimate transmitter mass & power – Estimate payload mass & power
Link equation Eh PL GlsLag kTR Energy/bit to noise-density ratio
Link Equation Eb No P Ll Gt L s La Gr k Ts R Energy/bit to noise-density ratio
Variable definitions Chart 12 Variable Definition Units Units dB Energy per bit Watt-seconds dB Noise spectral Watts/hertz dB density Transmitter Watts dBW lower Line loss dB Transmitter db antenna gain pace loss DB
Variable Definitions Chart 12 Variable Definition Units Units dB E b Energy per bit Watt-seconds dB N o Noise spectral density Watts/hertz dB P Transmitter power Watts dBW Ll Line loss dB Gt Transmitter antenna gain db L s Space loss DB
Variable definitions Chart 12 continued Variable Definition Units Units(d B) Transmission path loss Receiver gain dB Boltzmann J/K dBW/(Hz-K) constant System noise K temperature R Data rate Bits/ econd
Variable Definitions Chart 12 continued Variable Definition Units Units (dB) L a Transmission path loss dB G r Receiver gain dB k Boltzmann constant J/K dBW/(Hz-K) Ts System noise temperature K R Data rate Bits/ second