Tesis Doctorado
Adquisición en redes inalámbricas de sensores con múltiples antenas
Acquisition in wireless sensor networks equiped with multiple antennas
Autor
Aldunate-Varela, Joaquin
Institución
Resumen
In packet-based wireless communications, the first task of a receiver is to detect the presence of a signal in the air and to determine a timing reference about it. This task is often assisted by transmitting a known preamble sequence. The task has to be performed under several impairments such as thermal noise, carrier frequency offset and unknown fading coefficients of the wireless channel. Diversity techniques with multiple receive antennas can be used to improve the acquisition quality under these impairments, specially for low signal-to-noise ratio (SNR) situations. Traditional diversity techniques with multiple antennas have been used before to this end. However, they require channel state information, which is specially hard to obtain in low SNR situations. To this end, this paper presents an acquisition scheme that exploits a differentially encoded preamble and multiple receive antennas in order to detect signals at very low SNR without requiring channel state information. The acquisition scheme does not suffer the limitations of traditional techniques. We found that: i) the probability of false alarm is strongly reduced with a larger number of receive branches, ii) the probability of failed acquisition has a minimum value and the entire curve decreases as the number of receive branches Nr grows, and iii) a better trade-off between the probability of false alarm and failure can be achieved with more receive branches. The scheme’s performance is analyzed theoretically and verified by simulations and through experiments. PFCHA-Becas PFCHA-Becas