FFH and MCFH Spread-Spectrum Wireless Sensor Network Systems Based on the Generalized Approach to Signal Processing

In this paper, the performance of frequency-hopping spread-spectrum wireless sensor network systems based on the generalized approach to signal processing in the presence of noise [1–5], which employ noncoherent reception and transmission diversity, is analyzed for frequency-selective Rayleigh fading channels. Two different types of transmission diversity systems, a fast frequency-hopping (FFH) [6,7] and a multicarrier frequency-hopping (MCFH)[8] wireless sensor network systems, are investigated. In order to combine received signals from transmit diversity channels, the diversity combining rule based on the generalized approach to signal processing is developed. Probability of error equations are derived and utilized to evaluate the performance of two kinds of wireless sensor network systems. The effect of frequency-selective fading is also investigated in determining optimum frequency deviations of binary frequency-shift keying (BFSK) signals. The systems considered in this paper are frequency-hopping spread-spectrum (FHSS) ones with BFSK modulation, noncoherent detection, and definite diversity order. Diversity order refers to the number of hops per symbol for FFH and the number of subbands for MCFH wireless sensor network systems. Each transmit diversity channel is modeled as a frequency-selective Rayleigh fading process and is assumed to be independently faded. The maximum delay spread of each diversity reception is assumed smaller than one hop duration for FFH wireless sensor network systems, which is smaller than the symbol duration. It is also assumed that one symbol is transmitted during one hop duration in MCFH wireless sensor network systems, and adjacent symbols in time are transmitted in far distant frequency slot such that multipath interference from the previous symbol is negligible. Key-Words: Wireless sensor network, frequency-hopping spread-spectrum, frequency-shift keying signals, generalized detector, probability distribution function, BER performance.