A bottom-hole
assembly (202), BHA, for drilling a borehole (204, 301) in an earth formation (208, 300), comprising a percussion
drill bit (208), a percussion mechanism adapted to strike the
drill bit (208), at least one sensor (226, 228, 230, 232, 234) for measuring a
physical quantity and converting it into an electrical
signal, and converting means (237) for converting the electrical
signal into a
digital signal, and a method for transmitting data from such a bottom-hole
assembly (202) positioned in a borehole (204, 301), the bottom-hole
assembly (202) and the method being characterized by encoding the
digital signal by controlling the percussion mechanism and time periods between two impacts delivered by the percussion mechanism on the
drill bit (208) during drilling, and transmitting the encoded
digital signal by
waves generated by the impacts delivered by the percussion mechanism on the
drill bit (208). A
system which comprises said bottom-hole assembly (202).