Questions tagged [qpsk]

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Spectral properties of QPSK modulation

From what I've read, the spectral properties of the modulation largely depend on the rate of change of the signal phase - "a signal in which the phase changes stepwise has a broad spectrum, well ...
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185 views

Gray code usage in modulation constellations

When mapping symbols of various modulation constellations, Gray code is used such that - each adjacent symbol only differs by one bit. Why do we want small physical changes in the signal to correspond ...
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1answer
61 views

QPSK/QAM, digital quadrature modulation: square wave as local oscillator possible?

Goal is to build a lab exercise for students to illustrate digital IQ-modulation (QPSK, M-QAM). The bit stream for I and Q are generated by e.g. an Arduino. Is it possible to use a square wave as ...
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53 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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55 views

What does division order mean in Rayleigh Fading?

So I'm just beginning to understand how Rayleigh Fading works and I'm trying to model some different modulation schemes with Rayleigh fading channels. I'm doing this on MATLAB where one of the ...
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2answers
86 views

Is there a method to get the carrier from the recieved QPSK signal?

If we have given a signal and we know that is a modulated QPSK signal, can we recover the carrier if we know the carrier frequency fc. Edit: A clarification, I do not have to do it in hardware, a ...
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90 views

Can we band pass filter QPSK signal?

Consider we have QPSK signal with carrier frequency 10kHz. Generally, we demodulate or use matched filter on the the QPSK signal and recover the transmitted bit or the symbols. If the QPSk signal is ...
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1answer
77 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 sampls from the received signal. So what is the minimum sampling ...
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1answer
23 views

Need some help in bit error rate calculation for QPSK when using Gray coding

Why is Probability of Bit Error = 2 times the Probability of Symbol Error in QPSK with Gray Coding. Is it because one bit error has the potential to cause two symbol errors (2 symbols where they ...
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1answer
129 views

Peak-to-Average Power Ratio in OFDMA Communication

I am looking for a formula to calculate the Average Power of a square wave used in APSK Modulation. In my textbook, the example above is given with no formula so I am a loss how the value for ...
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116 views

Offset QPSK Frame sync markers

What actual protocols exist out there that employ Offset Quadrature Phase-Shift Keying (OQPSK)? What do they use for the frame synchronization marker (or "preamble" or "sync word" or "flag")? Do ...
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1answer
344 views

How to interpret transitions in a QPSK constellation diagram?

I have one doubt regarding how to analyze a constellation diagram. It is from a QPSK transmitter. The constellation diagram looks typically as books (as a square as you can see in Figure 1), but for ...
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83 views

Differential QPSK receiver

The communications channel between a QPSK transmitter and receiver can introduce an arbitrary phase change. For this reason, differential QPSK is used. Differential QPSK seeks to solve the phase ...
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2answers
515 views

what relationships exists between the BER vs SNR graphs of QPSK and QAM modulation schemes on data throughput. which scheme does better?

Using QAM and QPSK modulation schemes, RF field measurements like received signal power and pathloss were obtained from where the SNR values were estimated. Their BER values were also calculated and ...
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2answers
246 views

Phase rotation for QPSK

I have two SDRs and I want to do a simple test: I want to send data values using QPSK modulation with coordinates: (1,1), (-1, 1), (1, -1), (-1, -1), but on Rx site I got all possible values on the ...
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1k views

Differentiating between 32-QAM and 32-PSK

A communication channel with 4 kHz bandwidth requires 40 kbps data rate. What is the most suitable modulation technique to use in this particular scenario? for this I used the Nyquist theorem. C=2B ...
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1answer
190 views

Newbie: From bitstream to QPSK

I'm a complete newbie. I don't want to bother this fantastic resource with my ignorance, but I'm starting to have strange thoughts. How do I go from a bitstream (say, the output of an USB port) to a ...
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1k views

Designing an optimal BPSK and/or QPSK transciever in SDR

I'm currently working on writing firmware for the modem on a cube satellite for my university's satellite team. My primary goal is to implement the data uplink & downlink. The RF system, ...