Universal powerline bus

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Universal powerline bus (UPB) is a protocol for communication between devices used for home automation. It uses power line wiring for signaling and control.

UPB was developed by PCS Powerline Systems of Northridge, California, and released in 1999. Based on the concept of the ubiquitous X10 standard, UPB has an improved transmission rate and higher reliability. While X10 without specialty firewalls has a reported reliability of 70-80%, UPB reportedly has a reliability of more than 99%.

Power-line carrier control overview[edit]

Household electrical wiring, such as Romex or BX cable, is used to send digital data between UPB devices.

While in the X10 protocol the digital information is encoded onto a 120 kHz carrier, transmitted as bursts during the relatively quiet zero crossings of the 50 or 60 Hz AC sine wave, the UPB protocol works differently.

The UPB communication method consists of a series of precisely timed electrical pulses — called UPB Pulses — that are superimposed on the normal AC power sine wave. Receiving UPB devices can easily detect and analyze the UPB Pulses and extract the encoded digital information from them.

UPB Pulses are generated by charging a capacitor to a high voltage and then discharging that capacitor into the power line at a precise time. This quick discharging of the capacitor creates a large “spike” (or pulse) on the power line that is easily detectable by receiving UPB devices wired large distances away on the same line.

UPB protocol[edit]

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 high bandwidth applications, it is perfectly adequate for 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[specify] attributes that make it an optimum position for power line communication. 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.


UPB controllers range from extremely simple plug-in modules to very sophisticated whole-house home automation controllers.

The simplest controllers are plug-in controllers that are recommended for a moderate amount of switches and devices, as it becomes cumbersome to control a wide range of devices.

More sophisticated controllers can control more units and/or incorporate timers that perform pre-programmed functions at specific times each day. Units are also available that use passive infrared motion detectors or photocells to turn lights on and off based on external conditions.

Finally, whole house home automation controllers can be fully programmed. These systems can execute many different timed events, respond to external sensors, and execute, with the press of a single button, an entire scene, turning lights on, establishing brightness levels, and so on.

Things to consider[edit]

UPB is a power line carrier technology that may be affected by devices on the line. However, with the advance of the technology to Generation II there are only a few items that can affect the UPB signal. The engineering team created specific devices to isolate these items.

From the description above, it is plainly evident that UPB employs a non-secure method of signaling. The signals can readily be detected outside the premises as long as one has access to the AC mains and UPB commands can be injected on the mains outside the premises that can be used to take control of devices without the system owner's knowledge or permission.

See also[edit]

  • Insteon — dual-band (radio-frequency and power line) mesh home automation protocol
  • X10 — older power line home automation protocol
  • ZigBee — radio-frequency mesh home automation protocol
  • Z-Wave — radio-frequency mesh home automation protocol
  • IEC 61334 — standard for wide-area power line communication

External links[edit]