Improved Channel Sounding Using Zero Correlation Zone Sequences

Direct sequence spread spectrum (DSSS) techniques are commonly used for characterizing RF communications channels. These techniques have relative immunity to interference and do not require a direct reference connection between the transmitter and receiver. Current DSSS propagation measurement systems use a pseudo noise (PN) sequence to probe the impulse response of the channel. However, the use of PN sequences can introduce noise into the measurements. This noise is caused by a bias term that is inversely proportional to the length of the PN-Sequence, and limits the dynamic range of the measurement system. In this paper it is shown that this bias term will not be present when zero correlation zone (ZCZ) sequences are used. Consequently the dynamic range of the measurement system is limited by the SNR instead of the sequence itself. This paper also provides test data to show the effects of the bias term and to compare and contrast the use of PN and ZCZ sequences.