Spread Spectrum Communications – Introduction

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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

Demystifying Error Correction: Convolutional Codes and the Viterbi Algorithm

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Convolutional Encoding Unlike block codes (like Reed-Solomon), Convolutional Codes do not have a fixed block size. Instead, they process a continuous stream of bits. The output at any given time depends not only on the current input bit but also on the previous $K-1$ bits, where $K$ is the Constraint Length.+1. Convolutional codes are a … Read more

Performance comparison of digital modulation techniques — BER trade-offs at a glance

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Digital Modulations 101 — 5 lessons (same on every page in this path) 1. BPSK → 2. QPSK → 3. M-PSK sim (you are here) → 4. QAM sim → 5. EVM Tools: BER vs Eb/N0 · EVM → SNR · Eb/N0 ↔ SNR Side reading for Digital Modulations 101. Use this comparison after QPSK … Read more

BPSK modulation and demodulation — constellation, decision rule, and BER intuition

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BPSK maps bits to opposite phases; coherent demodulation, decision rule, and links to the Q-function BER formula and interactive calculator.

Young’s model for Rayleigh fading — filtered Gaussian discrete-time simulation

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Fading & Diversity — 6 lessons (same on every page in this path) 1. Rayleigh BER → 2. Clarke’s model → 3. Young’s model (you are here) → 4. SIMO models → 5. Selection combining → 6. MRC Tools: BER vs Eb/N0 · 3GPP TDL · CDL / Doppler Lesson 3 of 6. Another standard … Read more

Fading channel – complex baseband equivalent models

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Fading Lab path: Fading models → Young → Clarke SOS → BPSK BER Rayleigh → MRC  Keyfocus: Fading channel models for simulation. Learn how fading channels can be modeled as FIR filters for simplified modulation & detection. Rayleigh/Rician fading. Introduction A fading channel is a wireless communication channel in which the quality of the … Read more

Central Limit Theorem – a demonstration

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 This post contains interactive python code which you can execute in the browser itself. Central Limit Theorem – What is it ? The central limit theorem (CLT) is a fundamental concept in statistics and probability theory that explains how the sum of independent and identically distributed random variables behaves. The theorem states that as … Read more