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

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

Understand Moving Average Filter with Python & Matlab

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This post contains interactive python code which you can execute in the browser itself. The moving average filter is a simple Low Pass FIR (Finite Impulse Response) filter commonly used for smoothing an array of sampled data/signal. It takes \(L\) samples of input at a time and takes the average of those \(L\)-samples and produces … Read more

Random Interleaver

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Random Interleaver: The Random Interleaver rearranges the elements of its input vector using a random permutation. The incoming data is rearranged using a series of generated permuter indices. A permuter is essentially a device that generates pseudo-random permutation of given memory addresses. The data is arranged according to the pseudo-random order of memory addresses. The … Read more

Block Interleaver Design for RS codes

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Reed-Solomon (RS) codes are powerhouse error-correcting tools, but they have a specific Achilles’ heel: if a burst inside one codeword exceeds the correction radius \(t = \lfloor (n-k)/2 \rfloor\), a bounded-distance decoder fails on that codeword. Block Interleaving is the mathematical bridge that allows RS codes to survive massive, contiguous bursts by spreading the damage … Read more