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IEEE ICASSP is probably still the largest international conference on communications and signal processing. IEEE Transactions on Signal Processing and Communications are well-regarded journals.


3

What you have studied doesn't seem to include a definition of Average Power. For deterministic signal $x(t)$, the instantaneous power delivered at time $t$ is $x^2(t)$ ${\big (}$yeh, yeh, nitpickers should choose $R=1$ in their beloved formula $\dfrac{V^2}R\big )$ which varies from instant to instant. Thus, the average power delivered by $x(t)$ can be ...


3

Since $$g_I(t)=\frac12\big[g(t)+g^*(t)\big]$$ and $$g_Q(t)=\frac{1}{2j}\big[g(t)-g^*(t)\big]$$ the corresponding Fourier transforms are $$G_I(f)=\frac12\big[G(f)+G^*(-f)\big]$$ which is the even part of $G(f)$, and $$G_Q(f)=\frac{1}{2j}\big[G(f)-G^*(-f)\big]$$ which is the odd part of $G(f)$ (times $1/j$). It is easier to visualize what's happening if you ...


3

The canonical baseband version of BPSK is that we wish to transmit a sequence $\{a_k\}$ of bits ($0$ or $1$) at a rate of $1$ bit every $T$ seconds using a pulse $g(t)$ of duration $T$ and so the transmitted baseband signal is $$s_{\text{baseband}}(t) = \sum_{k=-\infty}^\infty (-1)^{a_k}g(t-kT).$$ This is a sequence of nonoverlapping pulses of the form $\pm ...


2

A DC offset in the frequency domain will be an impulse at $f=0$. The interpretation of this is a single tone interference: "DC" is no different spectrally than any other frequency when viewed as the Fourier Transform of a complex signal with positive and negative frequencies as the baseband spectrum centered about $f=0$ is identical to that ...


2

I think you misunderstand what the book is saying. There is nothing like a "unit-energy" that you can compute. There is, however, a "unit-energy [...] pulse", which is a pulse with energy equal to $1$. So if you have some pulse $p(t)$ with energy $$E_p=\int_{-\infty}^{\infty}|p(t)|^2dt\tag{1}$$ and you want to normalize it such that its ...


2

In the context of wireless communications, the channel impulse response (CIR) is often estimated indirectly via the time-varying transfer function (TVTF) $H(t, f)$, defined by: $$ H(t, f) = \mathcal F_\tau [ h(t, \tau)] $$ where $\mathcal F_\tau [ \cdot ]$ denotes the Fourier transform with respect to the $\tau$ (lag) variable. For example, the air interface ...


2

is there any difference between DC power and average power Yes. DC power is the square the of the mean of the signal . Average power is the mean of the square of the signal. It looks your teacher is using poor terminology. In this case "average power" and "total power" are the same. Neither one is a great term.


2

I mean it's just acoustic waves through air No it's not. Not unless you are operating in an anechoic chamber (which is unlikely). The total transfer function of your channel can be quite complicated. You have Driver and codecs (if any) D/A & Amplifier. You have to make sure that you get decent signal to noise ratio and not overdriving or clipping ...


1

First of all: I'm 100% with Hilmar. I'm really not an acoustic expert, but I remember helping students build a minimal audio data transmission system, and the take aways are really these; you can, if you limit volume to "nice and far below max volume of the system" practically ignore 1., 2., and 6., and if you filter harmonics well enough at the ...


1

Your questions are quite broad and hence difficult to answer. If the communication system can afford the bandwidth for a pilot signal, then a pilot can be used. Yes, channel estimation would be needed. Typically, SNRs would be calculated in the digital domain. However, these answers won't help you and you'll need to delve into the theory more deeply. If you ...


1

Each IFFT complex result bin represents an amplitude and a phase for some frequency. You can use the sum of the a sine and a cosine in the appropriate ratios to produce a sinusoid of any phase (see trig identity). The IQ inphase and quadrature modulators produce the sine and cosine in the appropriate ratios to produce the transmit phase as needed. This ...


1

Because the output of the IFFT operation is a vector of complex numbers. An RF signal is a real thing, so you can't just multiply a sine wave by a complex number and get something sensible. However, you can map a complex number onto an RF carrier by multiplying the real part by $\cos \omega t$, and the imaginary part by $\sin \omega t$. This is I/Q ...


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