Questions tagged [qpsk]

Quadrature Phase Shift Keying

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19 views

Modulation upsampling method

I try to implement a qpsk modulator in Octave. The chain is the state of the art I guess: Mapper -> Upsampling x4 -> Root raised cosine filter. My main question is about the upsampling. I try to ...
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1answer
2k views

DFE for QPSK in MATLAB

I need to do a DFE for QPSK simulation in MATLAB. The system consists of a QPSK signal transmitted with power = 1 which is then pulse shaped with a square raised-cosine filter. Add AWGN and a filter ...
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2k views

GNU Radio QPSK 4 Symbols

I'd like to generate a simple QPSK signal in GNU radio, but so far I haven't been able to get it to perform the way I'd like and I'm not sure if this has to do with some misunderstanding I have about ...
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1answer
62 views

Differential Encoding for M-PSK

Confused about a few topics w.r.t. differential encoding/decoding. First, consider the below BER curve taken from wikipedia ( https://en.wikipedia.org/wiki/Phase-shift_keying ) comparing BPSK/QPSK and ...
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30 views

How to deal with modulator jitter?

I have a question regarding an implementation of a modulator. I guess some people here have an FPGA background. I would like to implement a QPSK modulator of  31 Mbit bitrate using a 125 MHz clock. I ...
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116 views

What causes this type of distortion in a constellation I/Q plot?

I'm transmitting QPSK through a digital pulse shaping filter (RRC, 35% excess BW, 2 samples per symbol, 64 taps) at a rate of 56Msym/sec. Receiving it on standard lab equipment (Vector signal ...
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1answer
79 views

Sample rates, Samples per Symbol, and Digital Pulse Shaping

Having some confusion about digital pulse shaping for complex baseband (passband) signals. The complex baseband linear modulation equation is $$s(t)=\sum_{m=-\infty}^{\infty}\text{Re}\{a_m\}h(t-mT)+j\...
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32 views

How to Tx CDMA signal physically using an existing point-to-point modem? [closed]

I am working in acoustic communication, I want to test CDMA network capabilities in acoustic environment. I had an acoustic modem that has serial interface, a WHOI micromodem. How can i serialized ...
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1answer
63 views

Python code for QPSK modulator [closed]

Have any of you done anything like QPSK Modulation in python? I am in the middle of it and having problems in setting up bits? like odd and even bits. Have you got any idea? Regards, Sam
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1answer
243 views

QPSK Phase Recovery : Maximum-likelihood Vs Costa's Loop

I have implemented a QPSK Costa's loop in GNU Radio and run some BER benchmarking. All is going well. Out of curiosity, I'm trying to implement the Maximum Likelihood phase recovery shown below. For ...
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40 views

How are pulse trains generated in a radio transmitter?

When simulating a PSK signal in MATLAB or Python, I often create an impulse train where each impulse is modulated with a symbol. This modulated impulse train then passes through a pulse shape filter ...
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1answer
23 views

How to plot BER Vs SNR of a received signal

I am using USRP to transmit and received MIMO frames similar to Wi-Fi standard that I created on my own. After receiving the signal, it is processed as described in the standard. While I plot the ...
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2answers
80 views

MATLAB: Issue with passing data through AWGN Channel [closed]

I am trying to send QAM data through AWGN channel and I have 256 samples/symbol, I have the following code: ...
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1answer
34 views

Phase Noise in Constellation Plot

I have the following phase noise plot (-100dBc/Hz @ 1MHz offset and -130dBc/Hz noise floor): The integrated phase jitter for this phase noise is around $4.6^\circ$. According to my understanding the ...
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66 views

IQ Mismatch and Image

I was reading the following paper about direct conversion receivers from TI: link. In this paper they compare the performance of direct conversion and heterodyne receiver with IQ mismatch. The ...
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1answer
84 views

Carrier Tracking Loop: Tracking noise vs Phase Noise Trade-off

I would like to compare two different implementations of carrier tracking loop which differ in the way phase detection happens in the PLL. I am using PSK modulation for the data. In the first ...
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1answer
56 views

Signal Timing Recovery, Loop Bandwidth and SNR

As explained in the answer here, for the symbol timing recovery loop we need to keep loop bandwidth sufficiently below the modulation bandwidth of the signal so as to avoid the filtering of the signal ...
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1answer
36 views

MATLAB: Generating a random bit stream in a frequency Band for PSK Modulation

I want to generate a pseudo-random bit stream in MATLAB in a given frequency band for PSK Modulation. I am using the idinput function to generate the bit stream: <...
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1answer
52 views

Loop Bandwidth for Carrier Demodulation loop

I am trying to implement a simple MATLAB model for the demodulators for phase modulated signals (PSK) used in communication systems. For the detection of the phase modulated output (PM out in the ...
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0answers
13 views

What is the QPSK Constellation Diagram used in LTE

I think the question is pretty straightforward. I have to do a class project that requires me to modulate a signal, and one of the steps is Quadrature Phase Shift Keying (QPSK). It is to be done in ...
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28 views

QPSK matlab/simulink Quantisation effects

I am trying to simulate the effects of quantization of an ADC on different waveforms (e.g. QPSK,8PSK) in Simulink. For the case of QPSK the default BER curve would be generated with 2 bits per symbol ...
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1answer
77 views

QPSK demodulation problem due to apparent transmitter clock frequency drift

I am using FPGA to generate 10Mbaud QPSK signal in two channels corresponding to two quadratures. Upsampling to 1GSample/s (using raised cos filter for interpolation) and complex upconversion (f_up=...
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1answer
27 views

Modulation classification via demodulation confidence?

I'm not sure if this is the right place to post this question, but will try anyway :-) I recently started reading up on the field of automated modulation classification (AMC) where an algorithm ...
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1answer
65 views

ADC sampling rate implications Matlab/Simulink M-PSK modulation

I am trying to find a way to evaluate what would be the minimum sampling rate used in a modulated waveform using matlab / Simulink. The real scenario would be let say a M-PSK waveform of Y bandwidth ...
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1answer
56 views

Digital Tanlock carrier recovery loop

I’m currently trying to understand a digital tanlock carrier recovery loop for QPSK (for example) I cannot understand how it works. For example we an ideal QPSK constellation. phi = atan2(Q/I) = pi/...
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49 views

Nyquist sampling theorem / Nyquist - Shannon theorem evaluation over M-PSK

I am trying to simulate an M-PSK Tx-Rx System on Simulink and analyse what the effect of sampling rate reduction would have on it. More, particular I am trying to prove what Nyquist sampling theorem ...
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1answer
68 views

Understanding Matlab's Automatic Gain Control function

I am trying to understand the automatic gain control block provided by the communications toolbox. The documentation is here: Documentation My questions are in regards to two of the configurable ...
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Learning PSK Modulation and Demodulation - Good Text to Read?

Title sums it up. I am curious to see what you all suggest. I'm a newbie and just need some beginner/intermediate material. Thanks!
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GNU Radio - Bandwidth and Band Reject Filter

I am currently trying to generate a psk modulated carrier with gnu radio. Attach is an image of my flow graph. As can be seen I am generating a bit stream using the Random Source module and ...
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1answer
49 views

Mapping soft symbols in DQPSK

I'm trying to soft decode DQPSK. According to this paper the bits are: $b_1 = \mathrm{Re}\{s_n s^*_{n-1}\}, b_2 = \mathrm{Im}\{s_n s^*_{n-1}\}$ If I put 0.707 as a 100% probability of 0: $\begin{...
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26 views

lte matlab baseband IQ recovery

I am a beginner again to signal processing, I did my degree over ten years ago, and I am relearning all my signal processing stuff. I am a software developer by trade but now I am looking at some LTE ...
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1answer
105 views

Phase shifts of QPSK

I'm honestly lost on creating timing diagrams for bit sequences. I understand for QPSK there are symbols 00, 01, 10, 11 with phase shifts of 45,135,225 and 315. I'm just not understanding how you ...
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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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1answer
991 views

O-QPSK constellation interpretation - GNU Radio

I am currently trying to recover the I&Q of a O-QPSK signal generate from the standard XBEE arduino module using a B200. I can get somehow get a "look-like" of a constellation. Here an screenshoot:...
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247 views

What is the minimum sampling rate for QPSK or what is the bandwidth of QPSK signal?

Consider we have created a QPSK signal with a carrier frequency 100kHz. Before applying matched filter or demodulation we need to take samples from the received signal. So what is the minimum ...
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257 views

Relation between constellation SNR and baseband SNR

Let's say I have an I/Q modulation, ie. QPSK. I can simulate an the effects of an AWGN channel by adding to my QPSK symbols the realizations of a complex normal. $\mathcal{CN}(0,\frac{1}{\mathrm{SNR}...
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1answer
29 views

BER performance of a space-time code over Rayleigh channel model

For a given space-time code, and in general terms, how would one proceed in the evaluation of the BER performance of this code ? In order to be more clear, say i have 16 code matrices(who's elements ...
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384 views

BER of QPSK modulation in Rayleigh fading channel model

i am having trouble deriving a BER analytical expression for QPSK modulation system operating in a Rayleigh Fading channel model. Could anyone direct me to a reference that would help in this matter. ...
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How to compare two 802.15.4 O-QPSK modulated digitals signals?

I am working on wireless sensors project and I am trying to simulate a transmission between two nodes. So let's say I have two nodes which transmit the message to each other, i.e. node 1 transmits ...
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1answer
578 views

Offset QPSK detection in GNU Radio - Sample delay

An OQPSK detector is being tested in GNU Radio. The architecture was obtained from Michael Rice's Digital Communications - A discrete-time approach. The flowgraph is shown below. The modulator ...
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2answers
2k views

Why is bit error rate = symbol error rate / number of bits per symbol in QPSK

I saw a code computing the error probability of QPSK, and I found that in this code the bit error rate is computed as symbol error rate divided by $2$. I think that $2$ is because the QPSK symbol ...
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1answer
209 views

“Revolving” QPSK Constellation

I am trying to code a QPSK transmitter in VHDL but first I want to create one out of Simulink blocks and translate it into VHDL code. I am using an example project for the PlutoSDR as a guide. This ...
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1answer
198 views

OQPSK vs QPSK envelope query

We use OQPSK because of envelope of signal but my question is "In Phase Shift Keying(or QPSK) the amplitude of the transmitted signal is constant then how the envelope will change in OQPSK"??
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1answer
847 views

QPSK Data Rate vs Bandwidth at Passband: Why can it only transmit 1 bit per Hz and not 2 bits per Hz?

1) This is a follow up question to the most up-voted answer to this question. 2) The accepted answer is that "QPSK transmits 1 bit per Hz at passband". 3) The theory found in books seems to agree ...
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3answers
904 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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2answers
3k 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 ...
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what waveform using to send qpsk signal with IQ tranceiver

I have an SDR tranceiver (AD9361 on fmcomms3) working with IQ channels, i wanted to make a c++ software that modulate and send a digital QPSK signal but i'm a beginner in digital signal processing and ...
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225 views

SOQPSK-TG pulse shaping

I'm trying to build an SOQPSK-TG signal in MATLAB/Octave. I am following this paper for formulas. I'm trying to generate a waveform for the phase, equation 2.4: Where q(t) is the phase pulse, ...
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1answer
264 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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2answers
163 views

mpsk demodulation using digital sample

I am trying to receive and demodulate a 8PSK modulated sinusoidal waveform (real not complex) which is constant envelop and changing only in phase of the continuous sinusoid carrier every Symbol ...