OFDM BER simulation in AWGN — cyclic-prefixed MPSK and MQAM

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OFDM study path — 5 lessons (same on every page in this series) 1. Introduction → 2. Orthogonality → 3. IFFT modem → 4. Cyclic prefix → 5. BER in AWGN (you are here) Tools: OFDM CP overhead calculator · Eb/N0 ↔ SNR converter  In one sentence: Wire a discrete-time CP-OFDM chain (mapper → … Read more

Introduction to OFDM — multicarrier idea, FDM vs OFDM, and the five-lesson path

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OFDM study path — 5 lessons (same on every page in this series) 1. Introduction (you are here) → 2. Orthogonality → 3. IFFT modem → 4. Cyclic prefix → 5. BER in AWGN Tools: OFDM CP overhead calculator · Eb/N0 ↔ SNR converter In one sentence: OFDM shares bandwidth among many tightly spaced carriers … Read more

BPSK BER on Rayleigh fading vs AWGN — why flat fading costs SNR

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

Clarke’s Rayleigh fading model — sum-of-sinusoids simulation

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

Correlative Coding – Modified Duobinary Signaling

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Modified duobinary is the partial-response cousin of duobinary that puts a spectral null at DC. It correlates symbols two baud intervals apart, so the controlled ISI sits on the alternate sample rather than the neighbour. The Nyquist zero-ISI condition is relaxed to The minus sign at lag \(2T\) is what opens the null at DC. … Read more

Correlative coding – Duobinary Signaling

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The condition for zero ISI (Inter Symbol Interference) is which states that when sampling a particular symbol (at time instant nT=0), the effect of all other symbols on the current sampled symbol is zero. As discussed in the previous article, one of the practical ways to mitigate ISI is to use partial response signaling technique … Read more

Walsh Hadamard Code – Matlab Simulation

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Walsh–Hadamard codes of length \(N = 2^k\) are the rows of the Sylvester Hadamard matrix. Mapped to \(\pm 1\) they are mutually orthogonal. The listing builds that matrix, checks the Gram matrix, and plots the periodic cross-correlation of the first row against the others. Python Matlab The original Matlab helper is unchanged in spirit. bitand(codeSize,codeSize-1)==0 … Read more

Codes used in CDMA

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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