Search Results

For many years the state of the art was to use a convolutional "inner code" and a block "outer code". The "inner" and "outer" terminology come from the following block diagram: $$\boxed{\scriptstyle …

suppose, Carrier signal frequency = 2800KHz message signal frequency = 3KHz Then you will get a signal that looks like this in the frequency plane. Obviously this is not to scale, but you get the …

Ideal symbol pulses are sequences of rectangular pulses. Rectangular pulses, unfortunately, have horrible frequency profiles, as shown below. The main lobe is where most of the pulse power is, and …

There is no inherent symbol rate for any modulation type. 64 QAM symbols transmit 6 bits per symbol, and 256 QAM symbols transmit 8 bits per symbol. … The general equation for a given modulation type and its symbol rate is: $symbols/s = \frac{bits/s}{bits/symbol}$ Determining the bits per symbol is usually pretty easy. …

Yes and no. The mapping is arbitrary as long as the receiver correctly determines which constellation point a symbol is. If the receiver makes a mistake, though, it is most likely going to pick a "n …

1) Is there a connection between the modulation kind and the channel capacity? … Why and when do we do $\log_2(M)$ where $M$ is the number of modulation symbols? For example, if the modulation is 16 QAM, then what does $\log_2(16)$ tell us? …

The most computationally efficient approach is to set up the data you want in the frequency domain by putting in the tones as "spikes" in the appropriate frequency bins, and then inverse FFT'ing it to …

4-PAM transfers 2 bits ($log_2(4) = 2$) per symbol, while 2-PAM transfers 1 bit per symbol ($log_2(2) = 1$), so 4-PAM definitely transfers data faster. The catch is that you need higher SNR to get th …

If you do have feedback I would do the same but also dynamically change the modulation type from QPSK up to 16-QAM or something, depending on how well the signal is coming through. …

While I do not have proof, it seems pretty clear, given the "Characteristics of Compass signals reported as of May 2008 compared to GPS-L1CA" table at the Wikipedia page that you offered as an example …

Longer preambles make it easier for the demodulator to lock onto the signal well. This is due to getting more preamble signal energy and because longer preambles make it easier to detect stuff like c …

What you are seeing is the transitions from one constellation point to another. In order to reduce the signal bandwidth, the baseband signal is low-pass filtered. This causes the transitions to not …

1) A typical approach would be to have a frame alignment word (and by "word" I mean bit sequence) at the beginning of every frame. You could time synchronize by looking for that FAW through cross-cor …

I would use a frame alignment word to synchronize your data. The basic idea is to insert your FAW at the beginning of every $N$ bytes. After you demodulate the data you look for the FAW to synchroni …

You can use rectangular pulses, but it is not necessary to do so. Rectangular pulses have advantages and disadvantages. The advantage is that they are very simple and easy to use, both for the modul …