Wideband channel sounding and measurement

Abstract

Singapore has many high rise commercial buildings and shopping centers. The building structure and objects like lift can act as obstructions for Line-of-sight (LOS) propagation in a transmission channel. The transmission in these channels thus requires Non-line-of-sight (NLOS) propagation. However NLOS propagation poses many unpredictable effects on the channel thus there is a need to understand them through channel characterization using channel sounding technique. For military applications in particular, it is crucial for this study to ensure the wireless links use are reliable.

Wideband channel characterization will be tested and analyzed in this paper. Intra-level results and discussions will be presented together with outdoor to indoor results. The experiment uses frequencies from the range of 250MHz to 470MHz. Signal-to-Noise Ratio (SNR), delay spread and coherence bandwidth will be studied. A Pseudo-random Noise (PN) sequences, modulated by Binary Phase Shift Keying (BPSK), are transmitted to ensure signals reaching the receivers have uncorrelated fading. By setting a threshold of noise + 7dB to find the significant peaks from the power delay profile (PDP) of individual sample, the delay spread and coherence bandwidth can be calculated to allow better characterization of the channel. Delay spread and coherence bandwidth is important characteristics of a channel as they can affect the fading of the channel

The results show the signal strength for NLOS propagation depends largely on the obstructions between the transmitter and the receiver. It shows that as the obstructions increases and the position of the receiver is in a more enclosed are, delay spread will also increase while the coherence bandwidth decreases creating an inverse relationship between them.

By comparing the deterministic and stochastic power delay profile, it can be shown that both methods can be used to determine the channel characterization. Both methods are complementary and can be used together to predict the characteristics of the transmission channel.