# Tag Info

Accepted

### Why can so little digital information be stored on a cassette tape?

I had heard that tape is still the best medium for storing large amounts of data. well, "best" is always a reduction to a single set of optimization parameters (e.g. cost per bit, ...
• 25.7k
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### Can we break the Shannon capacity?

Most certainly not. While there has been some claims to break Shannon here and there, it usually turned out that the Shannon theorem was just applied in the wrong way. I've yet to see any such claim ...
• 1,634

### Can we break the Shannon capacity?

The capacity of a channel should be viewed as analogous to the speed limit on a highway. It is possible to travel at a speed greater than the posted limit on a highway but it is not possible to ...
• 18.7k

### Deriving SER & BER for 4QAM, 16QAM and 32QAM

I will try to give a relatively simple answer to a complex question. I will not give any exact expressions for the error rates for two reasons. The first I stated in my initial sentence, the second is ...
• 79.2k
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• 79.2k
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### Why upsample before modulation?

The reason is aliasing. Because the modulation is digital, on the discrete signal, the sampling frequency should be high enough that the channel's frequency band does not extend beyond the Nyquist ...
• 12.3k

### Audio frequency modulation algorithm

You need to build a time varying delay, where you can modulate the delay amount over time. The peak delay modulation is a function of your maximum desired frequency shift and the modulation ...
• 30.6k
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### Gardner Timing Recovery for Repeated Symbols

Your Gardner Loop would properly "Flywheel" in the absence of symbol transitions. So it would slowly drift off of synchronization, but would not spiral out of control as you describe. This is ideal ...
• 36.1k

### How is multiplexing achieved in spread-spectrum modulations like CSS?

disclaimer Because of the lack of document about LoRa CSS in Internet, the analysis below may be wrong with respect to LoRa system, not to the (linear) CSS principle. Any comment or update are ...
• 5,720

### Why do SDR receivers emit I/Q samples?

The SDR (or any general digital signal processing system) takes the received RF signal, and downconverts it from the carrier frequency to the baseband. Now, the real bandpass signal from the antenna ...
• 6,038

### Average bit error and symbol energy

The optimal decision regions are the Voronoi Regions. I dont know, if this is what you are looking after. ...
• 6,038

### Average bit error and symbol energy

As explained in Maximilian Matthé's answer, the exact computation of the symbol error probability of this constellation (ITU-T V.29 modem standard) is quite complex. However, you can quite easily ...
• 79.2k
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### What is the meaning of channel capacity?

1) Is there a connection between the modulation kind and the channel capacity? The capacity of a channel indicates the upper limit of how many bits can be transmitted per second over the channel with ...
• 11.8k

### What is the meaning of channel capacity?

1) Is there a connection between the modulation kind and the channel capacity? Channel capacity is usually defined as the number of information (usually measured by the number of bits) can be sent ...
• 5,720
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### Conversion between Eb/N0 and SNR in spread-spectrum modulation like LoRa CSS?

Let's start by fixing a symbol rate $R_s$ symbols per second. To modulate $R_s$ symbols per second without ISI, Nyquist says that we need a bandwidth at least $BW_0=1/R_s$ Hz. With spread spectrum, ...
• 5,720
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### Difference between Line Code and Keying

I think the Wikipedia definition is limited, and anybody using the terms keying and line coding interchangably is wrong. A line code is an encoding (or mapping) from bits to pulse amplitudes (...
• 13.5k
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### Difference between FFSK and FSK modulation schemes

Fast FSK is just another term for minimum-shift keying (MSK). In the modern literature, the term fast FSK has been almost completely replaced by MSK. There is a very good tutorial paper on MSK by S. ...
• 79.2k