Questions tagged [spectral-efficiency]
The spectral-efficiency tag has no usage guidance.
16
questions
4
votes
2answers
110 views
How is it that a dial-up modem can achieve 33.6Kbit/s with only 3100Hz of bandwidth?
My understanding is that plain old telephone service passes frequencies between 300Hz and 3400Hz. How is it that a V.34 modem in the late 90s would be able to achieve data rates of 33,600bits/s with ...
0
votes
1answer
30 views
Spectral efficiency of with OFDM vs without OFDM?
OFDM has advantage over frequency selective channel with addition of cyclic prefix after IFFT of MPSK or MQAM symbol. but I wonder that the spectral efficiency of with OFDM vs without OFDM.
0
votes
0answers
78 views
Is FFT sub matrix degeneracy a problem in OFDMA for some type of noise?
Say that the discrete Fourier transform (DFT) is used in OFDMA. There are a number of degenerate (singular, non invertible) sub matrices of some DFT matrices. Does this result in any problems?
One ...
2
votes
4answers
380 views
Are capacity and spectral efficiency identical for a dicrete-time digital signal?
I saw this answer and saw on the wikipedia page that both spectral efficiency and capacity can be measured in bpcu i.e. 'bits/symbol'. I just want to confirm then that they are identical for a ...
1
vote
1answer
77 views
Capacity and channel estimation algorithms: explanation of results
I study a spectral efficiency of a system with a precoding scheme with different channel schemes.
Algorithm A for channel estimation gives a smaller estimation error instead of Algorithm B.
I have ...
1
vote
0answers
76 views
Space-Time coding uses large amount of block codes to acheive maximum spectral efficiency
Assume I have a MIMO system with $M=8$ transmit antennas, and an arbitrary number of receive antennas.
This MIMO systems uses space-time coding. the block codes (matrices) transmitted are part of a ...
2
votes
1answer
175 views
Find Bandwith from Spectral Efficiency and Eb/N0
to give you a short intro of why I am asking here. My Uni is offering a TeleCom Lecture, I love the topic but all they teach is electronics, the exercise sheets are still TeleCom, we get no supporting ...
0
votes
1answer
69 views
Relationship between spectral efficiency and PAR
Low PAR means less fluctiations in the magnitude of a signal and hence analog signal processing (e.g., power amplifier) is tremendously reduced. For example, constant envelope modulation schemes like ...
1
vote
1answer
152 views
About combination between QAM and PAM
I have confused question regarding the possibility of combination between QAM modulation and PAM in order to improve the spectral efficiency. Is that possible?
As you see in the below Figure, it's ...
0
votes
1answer
83 views
A priori spectral efficiency of OFDM scheme
Of course I can compute the spectral efficiency as the ratio of the measured bit-rate (of data bits, no header, no preable, nor redundancy bits included) and the measured spectral bandwidth. This ...
0
votes
1answer
72 views
Why do we say that spectral efficiency is measured in [bit/s/Hz], not just [bit]?
The link spectral efficiency of a digital communication system is measured in bit/s/Hz.
We have that 1 Hz = 1 s$^{-1}$.
So, $\left((1 \,\text{bit}) /1 \text{s} \right)\, / \left({\frac{1}{1 \text{...
0
votes
1answer
2k views
Spectral Effeciency of BPSK
The null-to-null bandwidth of the main lobe of a BPSK signal is twice the symbol rate.
BPSK transmits one bit per symbol, so the signal bandwidth is twice the bit rate.
That has been shown on a few ...
2
votes
1answer
305 views
FFT subset output yields computational efficiency
The traditional FFT gives $N=2^k$ outputs for $N=2^k$ inputs (generally complex.) The time effort is $O(N \cdot \log(N))$. If all I want is a compact subset of $M \ll N$ output frequency points, is ...
4
votes
2answers
1k views
Does "keying on" a sine wave at a zero-crossing reduce its bandwidth?
I understand that a pure sine wave of infinite duration occupies no bandwidth, i.e. it is only the modulation of a carrier that gives it sidebands. Does the exact timing of a sudden modulation make ...
0
votes
0answers
45 views
ًWhy we use fourier transform in most of spectrum estimation approaches?
I wonder why in all spectrum estimation techniques, the analysis depend on the Fourier transform? Why not deal with the signals in time domain?
0
votes
2answers
593 views
ISI Nyquist criterion and spectral efficiency
While reading Bernard Sklar's Digital Communications book I've got confused with ISI Nyquist criterion (not Nyquist rate criterion). There is stated (Sklar, 3.3 section) for symbol rate $R_s$ minimum ...
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