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1

Since spreading and symbol modulation are memoryless linear operations, the order makes absolutely no difference. Both methods of writing the same thing down are equally valid, and the one you choose mainly depends on what is convenient for the rest of your text.


3

Don't worry too much about defining these terms too precisely, because they are used in many contexts with slightly different meanings. In very general terms, "estimation" is the calculation of a signal parameter, for example the phase, the mean, the PSD, etc. In other words, you have a signal, possibly noisy or distorted, and you want to find ...


0

A linear system cannot add anything new to its input signal, so additive noise is modeled separately from any linear distortion of the signal. In your case with just scaling and delay, the channel impulse response is $h(t)=k\delta(t-\Delta t)$, and the complete channel is modeled by first filtering the input signal with an LTI system with impulse response $h(...


1

An easy way to think about the power of a signal is to realize that it is the mean of the square of the signal. Now note that the cross-term $\cos(\omega_1t+\phi)\sin(\omega_2t+\phi)$ ($\omega_1\neq\omega_2$) doesn't have a (non-zero) mean, it's just equivalent to two sinusoids at the sum and difference frequencies. So you only get contributions from the ...


1

HINT: For real-valued periodic signal $x$ with period $T_0$ Parseval gives you $$ P=\frac 1T_0\int_{-T_0/2}^{T_0/2} x^2(t)\mathrm{d}t = \sum_{n=-\infty}^{\infty}\lvert c_n\rvert^2 $$ Where $c_n$'s are Fourier coefficients. You can then use the properties in Equations $(1)$ and $(2)$. $$ \mathcal F \big\{A\cos\left(2\pi f_0 t + \phi\right)\big\} = \frac A2\...


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Found out where the issue was. The above code gives a matrix of 0s, 2s, and 4s, but I forgot to take the matrix multiplication $GH^T$ modulo 2, which would give the expected matrix of all zeros.


1

In signal processing, "baseband" has two related meanings. The original notion of baseband (which is still used) is a real signal originating from some real process -- i.e., a voice recording, a video stream, a sensor's output over time. These processes are all characterized by having significant content down to zero Hz (or really close, in the ...


1

Co-channel interference occurs when multiple users are sharing the same resource (e.g., time-slot and frequency) and is also known as multi-user interference. In your original question, you were describing the MIMO channel - although not clear if that was for a single-user (SU) or multi-user (MU) system. If you meant a SU system, that wouldn't be considered ...


3

You're right, but you've misread the sentence: Baseband Data Communication means that there's no $f_c$. For example, your USB cable to your keyboard, that's baseband communication. It can only carrier real-valued signals, so you only get to choose one dimension, not two, of signal freedom. This is opposed to passband systems, where you can modulate the ...


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To my understanding, CFO is SFO is So they are different. Could you explain that SFO is a mixture of STO and CFO?


1

In short, increasing the distance results in a decrease in $E_b$. Consider two antennas in an otherwise empty universe (this is known as "free space"). The transmitter antenna radiates $P_t$ watts, and has gain $G_t$ in the direction of the receiver. The transmitted signal has wavelength $\lambda_0$. Then, the receiver antenna, with gain $G_r$ and ...


0

It depends on your actual decoder architecture, but if memory serves me right, uniform quantization is optimal for Min-Sum or Sum-Product decoders. (Intuitively, kind of makes sense – any other quantization could be modelled as "let's first apply a function to the LLRs and then quantize the result of that uniformly", and LLRs are what ...


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