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26 views

Different Theoretical and simulated BER curves - 802.15.4 OQPSK [closed]

The plot of the theoretical and simulated BER do not match for the 802.15.4 standard and I need help regarding what parameters I could change in order to make them similar. Here is a simplified ...
2
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1answer
52 views

Gardner timing recovery and constellation diagram

I would like to ask for some guidance regarding 2 issues mainly QPSK and Gardner algorithm for timing recovery. I am having as input a set of IQ samples (10 samples per symbol) to which I need to ...
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1answer
144 views

Rectangular 8 QAM bit error rate calculation

I am simulating an 8-QAM communication system over an AWGN channel for various signal to noise ratios, in order to plot the average bit error. However I have not been able to derive an equation for ...
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1answer
100 views

I/Q Sampling and Demodulation

A bit stream is mapped to symbols during baseband modulation, each symbol (say for QPSK) represents two bits. Each symbol has a corresponding I & Q value, which in QPSK, are used as the amplitude ...
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1answer
46 views

Processing OBPSK as OQPSK

I'm trying to create and process an OBPSK signal, which, as I understand it, transmits even bits on one axis and the odd bits on the opposite axis, resulting in a constellation with 4 unique points. ...
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1answer
21 views

dvb-s to dvb-c direct transmodulation

Is this possible to direct trans modulate DVB-S/S2 -> QI into -> DVB-C/C2 signals without doing it the way DVB-S/S2->Demodulator.ic-Transport Stream -> Modulator.ic-Transport Stream -> DVB-C/C2 ? Qpsk ...
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1answer
124 views

Why oversample data before using raised cosine filter?

In the process of creating a baseband signal, the complex symbols are filtered using a raised cosine filter to perform pulse shaping (I'm following some literature as a guide). The pulse shaping is ...
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0answers
253 views

DFE for QPSK in matlab

I need to do a DFE for QPSK simulation in matlab. The system, consist in QPSK signal transmitted with power = 1. Then pulse shapping with a square raised-cosine filter. Add AWGN and a filter receptor ...
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2answers
432 views

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 ...
3
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1answer
4k views

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: ...
2
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1answer
405 views

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 ...
3
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1answer
855 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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1answer
216 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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1answer
472 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 ...
2
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1answer
485 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. ...
2
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1answer
1k views

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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1answer
3k views

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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1answer
309 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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2answers
980 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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3answers
3k views

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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2answers
341 views

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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2answers
2k views

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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2answers
11k views

the relationship between bandwidth and the datarate

One Question of my note is like this. ...
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0answers
91 views

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. ...
7
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1answer
7k views

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 ...