This paper reviews the characteristics of a power line network as data communication medium and studies the challenges encountered when communicating over power wiring. This technology review has been done as part of feasibility study for using aircraft power-lines for data communication.
Power-Line Communication is a term which describes the use of existing electrical lines to provide the medium for a high speed communications network. Power Line Communications is achieved by superimposing the voice or data signals onto the line carrier signal using an appropriate communication technology. Power Line Communications represent a potential simplicity for communications among different devices, because it does not need additional wires for connecting devices network together.
Power line cables have been used as a communication medium for many years. However, because power line cables are not designed for communication, they pose major challenges for a modem designer. Frequency selectivity and time variation of the channel frequency response, high level of noise, and regulatory issues are some of the main considerations. The impedance, transmission line loss and noise level of power line fluctuate greatly according to how the devices are connected and their operating conditions. The paper reviews these sources of attenuation, noise and distortion encountered when communicating over power wiring. The power-line communication channel, in general, is modeled as having a time varying frequency-dependent signal-to-noise ratio over the communication bandwidth.
The paper further discusses the required features for aircraft data networks and presents aircraft power lines channel characteristics. The aircraft power-line was initially designed to distribute power in an efficient way, hence it is not adapted for communication and advanced communication methods are needed. Baseband techniques are not acceptable for Power Line Communications over aircraft power networks because of high powers transferred in baseband. This means some kind of passband technique has to be used. There exist a few types of digital modulations acceptable for this type of application. These can be split into narrowband and broadband. Narrowband mostly uses single carrier modulations like Frequency Shift Keying or Phase Shift Keying. Broadband modulations can be selected from Direct Sequence Spread Spectrum or Orthogonal Frequency Division Multiplex. The paper assesses these technologies in light of the known channel conditions and discusses realization of reliable high-speed communication over aircraft power-lines.