FREQUENCY-HOPPING SPREAD-SPECTRUM MODULATION FOR DIGITAL-COMMUNICATIONS OVER ELECTRICAL-POWER LINES

Low tension electrical power distribution networks represent a most attractive medium for digital communication purposes due to an ever increasing demand, e.g., for environment management of buildings, office automation and remote meter reading or security monitoring. On the other hand, such networks turn out to be rather hostile and unusual channels, due to the fact that their design never involved communications aspects. Access to these widespread and interesting networks calls for special transmission techniques to overcome high and varying levels of interference as well as varying values of impedance and attenuation. Furthermore, restrictions of transmission power and bandwidth have to be faced [1]. Spread-spectrum techniques are well known as effective instruments against a variety of interferers and hostile channel properties such as time-variant attenuation and selective fading 12]. Frequency-hopping spread-spectrum signaling offers interesting spectral efficiency and leads to cost-effective solutions when global synchronization is applicable. On the other hand, for frequency hopping the task of waveform generation and matched filter reception causes higher effort compared with pseudonoise phase shift keying (PN-PSK) [2]. A solution for precise and cost effective generation of frequency-hopping spread-spectrum waveforms is digital frequency synthesis based on read-only-memories (ROM, PROM, EPROM). For matched filter reception of frequency-hopping spread-spectrum waveforms a new approach based on lock-in amplifiers combined with synchronous voltage controlled oscillators (SVCO) brought remarkable results in practical field tests. Furthermore, an application specific digital signal processor for receiver operation in form of a CMOS gate array was designed. Prototypes according to two different system concepts were built, and measurements of bit error probability were carried out on indoor and outdoor power line networks. Computer simulations based on channel analysis to predict bit error probability are proposed and compared with measured results. Indoor prototypes are designed for a data rate of 300 bits/s, and a frequency hop rate of 900 s-1 with a transmission voltage V, ≈ 0.35 V rms in a spectral range from 30 to 146 kHz. Outdoor prototypes are intended for remote meter reading featuring a data rate of 60 bits/s and a frequency hop rate of 300 s-1. Transmission voltage V8 is variable from 0.35 to 1 Vrms in a spectral range from 30 to 146 kHz. © 1990 IEEE