Correlator Implementation for Orthogonal CSS Used in an Ultrasonic LPS

Abstract

This paper presents a new architecture for the correlation of orthogonal complementary sets of sequences (OCSS) and their performance in an ultrasonic local positioning system (U-LPS). OCSS are sets of sequences whose addition of correlation functions has ideal properties, that makes interference-free code-division multiple access (CDMA) possible. They can be used to encode the signals emitted by a CDMAbased U-LPS, enhancing the performance of such systems in terms of immunity against noise, multipath propagation, and near-far effect. Also, the orthogonality of the codes offers an operation resistance to multiaccess interference, which endows the U-LPS with the capability of simultaneous emission from different beacons. On the other hand, the detection of OCSS codes can be performed by means of efficient algorithms. This paper presents an optimization of previous proposals allowing the simultaneous correlation of OCSS by using fewer operations and memory elements. Furthermore, the hardware implementation of the proposed optimization is also addressed, and an U-LPS based on this proposal is presented.

Improved Ultrasonic Phased Array Based on Encoded Transmissions for Obstacle Detection

“…5 represents the pattern when the beam is steered at θ k = 0°, −16°and 20°, respectively; for this purpose the received signal a[n] has been correlated with the corresponding LS sequences S k , assigned to the angular sectors θ k = 20°, θ k = 0°and θ k = −16°. It can be noticed how the dynamic range remains the same as when a single LS sequence is emitted (8), since the CC between the K = 32 orthogonal codes is close to zero as long as it is within the IFW.…”

“…Consequently, Inter Symbol Interference (ISI) and Multiple Access Interference (MAI) are completely reduced if the maximum transmission delay is less than the length of the IFW. A set of K sequences S k with length L c are called LS sequences if the aperiodic correlation function of each pair belonging to the set S k 1 and S k 2 is [8]:…”

“…Regarding the dynamic range, it is around −9dB for both algorithms, corresponding to the dynamic range (DR) for an array with M = 8 elements according to (8) [24].…”

Simultaneous generation and correlation of complete sets of generalized pairwise complementary sequences

“…The applications involving the use of these sequences range from communications [1] to ultrasound image processing [2], including sensors [3] and local positioning systems [4]. A growing number of publications have addressed this topic and dealt with theoretical and practical aspects.…”

“…A growing number of publications have addressed this topic and dealt with theoretical and practical aspects. The applications involving the use of these sequences range from communications [1] to ultrasound image processing [2], including sensors [3] and local positioning systems [4]. The possibility of detecting signals immersed in noise, their multiuser properties and/or the possibility of performing channel identification are some of the key aspects of these sequences.…”