Abstract
In recent years, there has been great interest in using hybrid spread-spectrum (HSS) techniques for commercial
applications, particularly in the Smart Grid, in addition to their inherent uses in military communications. This is
because HSS can accommodate high data rates with high link integrity, even in the presence of significant multipath
effects and interfering signals. A highly useful form of this transmission technique for many types of command, control,
and sensing applications is the specific code-related combination of standard direct sequence modulation with ‘fast’
frequency hopping, denoted hybrid DS/FFH, wherein multiple frequency hops occur within a single data-bit time. In
this paper, error-probability analyses are performed for a hybrid DS/FFH system over standard Gaussian and fading-type
channels, progressively including the effects from wide- and partial-band jamming, multi-user interference, and varying
degrees of Rayleigh and Rician fading. In addition, an optimization approach is formulated that minimizes the bit-error
performance of a hybrid DS/FFH communication system and solves for the resulting system design parameters. The
optimization objective function is non-convex and can be solved by applying the Karush-Kuhn-Tucker conditions.
We also present our efforts toward exploring the design, implementation, and evaluation of a hybrid DS/FFH radio
transceiver using a single field-programmable gate array (FPGA). Numerical and experimental results are presented
under widely varying design parameters to demonstrate the adaptability of the waveform for varied harsh smart grid
RF signal environments.