# Tag Info

### OFDM intra-block multipath interference

By using cyclic prefix and its associated demodulation techniques, LTE OFDM (nearly) eliminates the inter-symbol inteference (ISI). The intra-block inteference, if I understand well your question, ...
• 6,595
Accepted

### How to accurately model wideband RF reflections?

So, to give you something to read up on first, the channel you describe is a Rician or Rayleigh channel, depending on whether you have a dominant line-of-sight path or not. So, as a first approach, ...
• 30.7k

### Multipath resistance of spread spectrum systems

The key idea in spread-spectrum communications is to use much more bandwidth than the minimum required for the signal being sent. Multipath effects occur when the sent signal $s(t)$ and a delayed, ...
• 25.7k

### MUltiple SIgnal Classification (MUSIC) Implementation

I'm going to group number 1 and 3 as related. For a high level description of MUSIC, you can take a look at MATLAB's overview here. One of the main steps in the algorithm is to find the eigenvectors ...
• 2,471
Accepted

### Wireless Channel Multiplicative Model

What's labeled $(1)$ in your question is a special case, the flat channel. It can be represented as a single coefficient. In general, channels aren't flat, and we then need to apply $(2)$ instead. ...
• 30.7k
Accepted

### Sound reflections plot

This is an idealized case of the echogram that simply depicts the times of arrival and energy of reflections. You can see this type of plot in literature and as an output in modelling software such as ...
• 11.1k

### Intersymbol Interference -- Root raised cosine filter redundant if doing impulse response equalization?

I think it can be misleading to think RRC are used to eliminate ISI. The only purpose of Raised Cosine (RC) and Root-Raised Cosine (RRC) filtering in the transmitter specifically is to constrain the ...
• 51.3k
Accepted

### Is Phase Locked Loop is essential for BPSK signal reception?

There are three different kinds of synchronization in a passband digital communications system: Carrier synchronization: the receiver needs to know the exact frequency and phase of the carrier used ...
• 15.3k
Accepted

### what does mean quasi-static channel

Quasi-static is almost-static. In other words, for a block (or window) period of time, you could assume that your channel is static. Below, i attach a figure that depicts this scenario. As you can see ...
• 730

### what does mean quasi-static channel

Quasi-static channels are a "block-wise" time (in)variant. For example, your channel has no variations over time (not in the delay domain) for some time period(e.g., 1 ms), but the channel ...
Accepted

### Where in the signal chain is Channel Equalization applied?

Generally, any matched filtering would be done before equalization, since there is no practical advantage that I am aware of to applying a matched filter afterwards. Most textbooks that I've read ...