# Tag Info

Accepted

### What wavelength do we use when calculating the array manifold vector when transmitting LFM waveforms?

As with many questions like these...it depends. We won't concentrate on LFM waveforms, the following is true for any waveform transmitted. Virtually all of the introductory material to steering a ...
• 2,601

### What is the physical meaning of coherence bandwidth in mmWave massive MIMO channel?

You are right, coherence bandwidth is the frequency domain counterpart of delay spread. However, to achieve diversity across antennas the spacing between the antennas is important "relative to the ...
• 2,620
Accepted

### Dimension of Matrix in MIMO with multi-path

The short answer is: if you transmit one block of $N$ symbols (no data before it for at least $L$ symbol times) over a frequency-selective channel of length $L$, then the channel matrix will be of ...
• 675

### DOA - 1D Music Algorithm

If you have three or more antennas, simply don't put them in a linear array. Any other array setup doesn't suffer from the ambiguity. Linear array is the worst choice here. Of course, that breaks the ...
• 31.3k

### FMCW Radar - Range-Doppler Plot

So the problem is that when simulating FMCW signals, there is some ambiguity in the convention on the mixing order. MATLAB's documentation makes reference to it here: "The mix operation reverses ...
• 2,601
Accepted

### Square Root MMSE

This is just a nice way to rewrite Equation (2). Using Block matrix interpretation: \begin{align} \underline{H}^H\underline{H}=\begin{bmatrix}H_{R\times T}^H&\sigma I_T\end{bmatrix}\begin{bmatrix}...
• 6,605
Accepted

However, from sources online, I've found that if $\vec a, \vec b$ are unit complex vectors then $\cos (\theta) = Re(\vec a \cdot \vec b)$, which is clearly not the same as (7.33). Is this a mistake in ...
• 6,605

### How to solve equations for the MMSE receiver?

I doubt there is general closed-form solution. For the first equation, you essentially want to solve $$\mu=\sum_k \frac{1}{a_k+b_k \mu}$$ for $\mu$ which equals to search for the zeros of a $k+1$th ...
• 6,228
Accepted

### What is the index modulation in OFDM and Subcarrier Index modulation?

Yes OFDM-IM is somehow new and it's very hot topic of searching. That article you have shares is the basic of OFDM-IM. So if you are at the beginning to understand it, that's the right paper to to ...
• 1,056

• 3,042
1 vote

### MU-MIMO Sensitivity to Line of Sight (LOS)

There is no mention of light-of-sight (LOS) on the time you mentioned. There is a mention of point-to-point, however. Point-to-point channels could be LOS or multipath. MU-MIMO is better than point-...
• 675
1 vote

### Channel direction

You should double check the formula. The classic single input multiple output (SIMO) equation with $N_T$ receive antennas is: $\mathbf{y}=\mathbf{h}x+\mathbf{w}$. Where $x$ is the transmitted symbol ...
• 3,042
1 vote
Accepted

First you have to know that the vector in $U$ and the vector in $V$ are orthonomal,that is ,$\vec u \vec u^H=I$,and $\vec v \vec v^H=I$. So now $H=U\Sigma V^H$,and $y=Hs+n=(U\Sigma V^H)s+n$ and $U^... 1 vote Accepted ### pairwise error probability and union bound of space time code The union bound can indeed result in a BER higher than 1. As you say, it is just an upper bound, and it becomes tighter as the SNR increases. For low SNR, the union bound can be quite loose. • 15.3k 1 vote Accepted ### Employing MIMO under the two-ray propagation model The Channel Impulse Response (CIR) for a beamforming vector$\mathbf{w} \in \mathbb{C}^{N_T \times 1}\$ (which corresponds to your spatial streams) is the following $$\mathbf{c}(n) = \sum\limits_{k=1}^... • 740 1 vote ### Understanding the concept of semi-blind receivers Let us consider a very simple example of a frequency-flat quasi-static MIMO communication system. In such a setup, we can write the received signal from, say, M_{\rm R} receive antennas as$$\mathbf ...
• 2,463

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