Universal Powerline Bus - UPB Protocol

UPB Protocol

While transmitting, one UPB Pulse is generated each half-cycle of the 60 Hz AC electrical power cycle. The generation of each UPB Pulse is precisely timed to occur in one of four predefined positions in the half-cycle of the AC powerline. The position of each UPB Pulse determines its value as either 0, 1, 2, or 3. This method of encoding data as a relative position of a pulse is a well-known and used method in digital communications known as Pulse-position modulation (PPM). Since each UPB Pulse can encode two bits of digital information and there are 120 AC half-cycles per second (at 60 Hz), UPB communication has a raw speed of 240 bits per second. Although this speed isn’t fast enough for doing high bandwidth applications it is perfectly adequate for doing command and control communication.

UPB Pulses are transmitted in a special region toward the end of the AC half-cycle known as the UPB Frame. This region was selected due to its relatively low noise characteristics and for other attributes that make it an optimum position for powerline communications. UPB Frames are synchronized to the low-to-high transition of the AC waveform (known as the AC zero-crossing point) such that one Frame starts T/Frame milliseconds after the zero crossing and the other Frame starts 8.333 milliseconds (one half-cycle at 60 Hz) after the first one.