Maximum-length sequences (m-sequences) — LFSR properties and autocorrelation
m-sequences from linear feedback shift registers: period 2ⁿ−1, two-level autocorrelation, and their role as parents of Gold codes.
Spread Spectrum
Gold code generator — preferred pairs, correlation, and CDMA use
How Gold codes are built from preferred m-sequence pairs, their three-valued cross-correlation, and why they are used in CDMA/GNSS spreading.
Walsh–Hadamard codes — generate the matrix and simulate in Matlab
Walsh–Hadamard spreading codes: how to build the Hadamard matrix, orthogonality properties, and a Matlab simulation for CDMA-style use.
Codes used in CDMA
IS-95 uses three families of sequences at once: a long code for scrambling, a short code for cell identity and quadrature spreading, and a set of Walsh–Hadamard codes for the forward channels under one base station. Long code The long code is an m-sequence from a 42-stage LFSR, clocked at the chip rate 1.2288 Mc/s. … Read more
Spread Spectrum Communications – Introduction
Spread spectrum system, originally developed for military applications, is extremely resistant to unauthorized detection, jamming, interference and noise. It converts a narrowband signal to wideband signal by the means of spreading. The original 802.11 and 802.11b used direct-sequence spreading. From 802.11a onward, Wi-Fi is OFDM. Bluetooth Classic hops; Bluetooth Low Energy hops as well, on … Read more