Link Margin

In a

wireless communication Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...

system, the link margin (LKM), measured in dB, is the difference between the minimum expected power received at the receiver's end, and the receiver's sensitivity (i.e., the received power at which the receiver will stop working). A 15 dB link margin means that the system could tolerate an additional 15 dB of attenuation between the transmitter and the receiver, and it would still just barely work. It is typical to design a system with at least a few dB of link margin, to allow for attenuation that is not modeled elsewhere. For example, a

satellite communication A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

s system operating in the tens of gigahertz might require additional link margin (vs. the

link budget A link budget is an accounting of all of the power gains and losses that a communication signal experiences in a telecommunication system; from a transmitter, through a communication medium such as radio waves, cable, waveguide, or optical fiber ...

assuming lossless propagation), in order to ensure that it still works with the extra losses due to

rain fade Rain fade refers primarily to the absorption (optics), absorption of a microwave radio frequency (RF) signal by atmospheric rain, snow, or ice, and losses which are especially prevalent at frequencies above 11 GHz. It also refers to the degradation ...

or other external factors. A system with a negative link margin would mean the system is insufficient to transfer data, usually this means a better receiver is needed, with improved sensitivity. Wireless networking Telecommunications engineering {{telecom-stub