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QPSK and OQPSK Modulation

In QPSK, after splitting the odd and even bits into the I and Q channels, and then multiplying them with the sine and cosine function, what next am I suppose to do? Do I rearrange them back into ...
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QPSK Modulation/Demodulation in C++

I'm trying to implement a QPSK Mod/DeMod system in C++. So far i have a bit generator that generates N bits and stores it into an array: ...
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CONCAT block in QPSK modulator

Can somebody explain the use of this CONCAT block (top right) Why we need to combine these signals together? Thanks!
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QPSK, from Square Root Raised Cosine to Rectangular Impulse Shaping

I have implemented a QPSK modulator and demodulator using classic text-book examples: Square Root Raised Cosine Impulse shaping and Matched Filtering. The problem is that I've been told that I could ...
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499 views

QPSK soft decoding

I'm trying to decode a Hamming Block Code transmitted using a QPSK modulation. For the moment I can sucessfully decode it using hard decision but in order to improve performance I'd like to use soft ...
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155 views

Barker Sequence for QPSK

I'm trying to implement a QPSK burst modulation and demodulation through a channel and I'm now considering the synchronization part. I've read that Barker sequence were excellent option for this as ...
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271 views

Practical Gardner timing error implementation

I'm trying to demodulate a QPSK communication. For the moment I do: Signal detection by computing the ratio between the power of the carrier wave compared to the signal power. Initial clock ...
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380 views

Frequency detection

What I have: A digital signal sampled at Fs composed of a QPSK modulation at Fmod plus some additive white gaussian noise. ...
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Apply AWGN noise to QPSK-OFDM symbol

I'm working on an OFDM-QPSK based system and I'm having some trouble to match the BER of my system with the theoretical curve. My OFDM implementation fills all the subcarriers and have t_symbol s ...
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How to perform carrier phase recovery in software?

What are the options for recovering the phase of a BPSK signal in software? The only resources I can find online contain circuit diagrams – there seems to be no one willing to explain this to people ...
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241 views

Why is a precoder necessary for DQPSK and what does it accomplish?

I've implemented a soft-decoder for DQPSK using the wonderful answers I received here: How to soft decode DQPSK? To get the soft-decoder working properly I needed to precode the data I was sending ...
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725 views

How to soft decode DQPSK?

I'm successfully soft-decoding D-BPSK by taking the dot-product of the constellation-position of the symbol and of the previous symbol. If the result is >= 1, then the symbol phase hasn't changed and ...
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Why does OFDM use cyclic-prefix while QPSK uses root-raised cosine filters?

My understanding is that BPSK/QPSK/... are often implemented with root-raised cosine (RRC) filters to reduce ISI and bandwidth. OFDM can be understood to be BPSK/QPSK/... implemented on multiple ...
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Meaning of Q and I in all-software QPSK communication systems?

Q and I seem to come up a lot in discussions of digital communications, such as the comprehensive answer provided to this question: FFT window phase syncronising It seems like the Q and I channels ...
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Why do you get instantaneous phase by calculating correlation with a carrier signal?

I am somewhat new to DSP. I'm trying to implement BPSK by following this Python QAM tutorial. My code seems to work, but I really just ported the tutorial's Python code to C++, and do not understand ...
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7k views

the relationship between bandwidth and the datarate

One Question of my note is like this. ...
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Recovering signal for psk

I am currently working on a product(cant disclose too much details of the actual project) in which some data is being sent via audible(but on the higher freq) sound that is encoded with dqpsk. ...
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Matlab plot of QPSK system doesn't agree perfectly with theoretical BER curves

Does anyone know if there is a simple explanation on the fact that the theoretical bit-error rate (BER) curves of a Quadrature phase-shift keying (QPSK) system are approximately 1 dB shifted from the ...