POWER LINES AS LOCAL AREA NETWORKS FOR MEASURING AND CONTROL SIGNAL TRANSMISSION

Abstract

Electrical power distribution networks represent the most attractive medium for digital communication purposes due to an ever increasing demand for environmental management of buildings, security monitoring, office automation or remote control of customer appliances and remote meter reading. Power lines are, however, heavily stressed with interference from various sources. Both interference and attenuation are time-variant and frequency-selective in an arbitrary way. The prospective user has to overcome the impairments with a severely restricted level of transmission power, e.g. 5 mW in Germany; the transmission bandwidth, however, exceeds 100 kHz. Obviously simple and inexpensive modulation schemes for digital data transmission such as amplitude shift keying (ASK) or frequency shift keying (FSK) are ruled out. A significant success of band-spreading techniques has been demonstrated by several field trials and extended measurements at different power line networks. Application of spread spectrum techniques generally involves high effort; this is especially true for frequency hopping, which proved advantageous in practical applications. Exploiting the possibilities of modern microelectronics, including design and production of ASICs, recently led to a break-through. A five-year research project based on frequency hopping spread spectrum signaling opened up power lines as local area networks e.g. for office automation or remote meter reading. Transmitter and receiver prototypes were constructed for evaluation of the proposed ideas at various power line networks. Transmitters are based on standard microcontrollers, whereas an application specific integrated circuit (ASIC) with a complexity of about ·5000 gates is the heart of the receiver. Due to completely digital signal processing. the prototypes are useful as a base for series production.