Link Budget

A link budget is an accounting of every gain and loss that a communication signal experiences as it travels from a transmitter to a receiver through a telecommunication system, whether that path runs through open air, cable, waveguide, or optical fiber. Its core calculation is simple in form: received power in decibel-milliwatts equals transmitted power plus all gains minus all losses, all expressed in decibels, a logarithmic scale on which adding decibel values corresponds to multiplying the underlying power ratios. Engineers use link budgets while designing a system to confirm that a signal will still arrive strong enough, relative to noise, to be read correctly, and because real losses vary and carry uncertainty, they build in a link margin, a safety buffer above the minimum detectable power that can be improved with techniques such as antenna diversity or multiple-antenna systems. Link budgets are calculated for systems ranging from ordinary radio links to Earth-Moon-Earth communication and the Voyager deep-space missions.