Questions tagged [telecommunications]
The telecommunications tag has no usage guidance.
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Noise in mm-wave initial access frameworks
I have a doubt about Initial Access (IA) procedures in mm-wave system.
In most papers I have read (see e.g. Initial Access in 5G mm-Wave Cellular Networks), most of the alignment procedures assume ...
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2
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Why do shift registers (LFSR) use the initial state "all 1"?
In all books about information coding theory, scientists describe shift registers of various configurations, but they always use the initial state "all 1" in any configuration and any bit ...
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113
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How to manage multiple devices connected to the same antenna?
I'm planning to connect an SDR in 'parallel' to a modem used to transmit and receive a radio signal on 2.4/5.8 GHz.
The SDR that I want to use is the HackRF one, which can receive up to -5 dBm in ...
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Intersymbol interference on PAM Trasmitter
I would like to simulate on Matlab a PAM signal which, travelling on a time-dispersive communication channel, contains intersymbol interference (ISI).
I have 'built' the transmitter by generating:
8-...
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Devices to measure RSSI and/or AGC
I need a way to measure the strength/power of a signal coming from an antenna, 2.4 or 5.8 GHz frequency. Is there any off-the-shelf device that can measure such property? Ideally I would want the ...
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Is it possible to to use same frequency band and same frequency blocks for two adjacent/near telecom circles
As shown in the Screen-Shot, TRAI (Telecom Regulatory authority of India) in the pre-auction recommendation manual to DoT(Department of telecommunication) mentions 770 MHz of the spectrum ( 35 MHz for ...
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Why do we modulate a signal before the transmission? [duplicate]
I have a fundamental question. Why do we modulate a signal before the transmission? What is the obstacle for transmitting a signal in its typical form?
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Is it possible for satellite communication to have less latency than cable and optic fiber?
I would expect satellite internet to have large latency. Apart from Starlink this holds for most of the rest. It seems you could argue that information travels a larger distance with respect to fiber ...
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Calculate the mean of signal \$ e^{-j2\pi t^2} \$
I'm a trying to calculate the mean value of the signal \$ e^{-j2\pi t^2} \$
Here is my attempt:
$$ <x\left(t\right)>\triangleq\lim_{T \to \infty}{\frac{1}{2T}\int_{-T}^{T}x\left(t\right)dt}=\...
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How do modulations depend on transmission media? [closed]
or how is transmission media affected by modulation? Is there any relationship?
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127
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How does multiplying the modulated signal "AGAIN" by the carrier frequency transfer the spectrum back to its original position?
I have some trouble understanding the demodulation of a signal. SI understand how we multiply the message signal by the carrier signal then chuck it through a channel, but on the receiver side I don't ...
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How is fiber coupling achieved in communication?
Optical communication with (single-mode) fibers is widespread. Pretty much the complete internet backbone is based on it.
However, I am wondering a bit how the light is coupled into the fibers. ...
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Difference of Milenage Version 1 and Version 2
I've heard in the telecom industry about Milenage Version 1 algorithm and Milenage Version 2 algorithm.
I want to know what are their differences?
The version 1 and version 2 have the same length for ...
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2
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137
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Transmission Line model [closed]
Can some one explain me why exactly classical circuit theory fails to account for the wave nature of EM fields and how the transmission line model accounts for it better
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391
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Why are microwaves unidirectional and radio waves omnidirectional?
I understand that any wave can be given direction using a setup like a phased array.
As I read about the properties of EM waves, I find that microwaves are unidirectional in nature.
What is it about ...
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174
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How can the Earth be used as a return path? Wouldn't the signal just dissipate after reaching the destination?
I was reading an academic document and I came across this statement:
Telegraphy, 1747 (a singe-wire line with the Earth as a return conductor – the first transmission line)
I can't imagine how that ...
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Hamming code error correction multiple bits
If we send a message from a sender and the noisy channel produces 2 bits with error can we detect both bits using hamming code or is it just for 1 bit?
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Why is the telecom input power supply range 36 to 72 V (polarity ignored)?
Why is the telecom power supply voltage level specifieded with a wide range: 36 to 72 V?
Is it because the rectified AC voltage would have variations as per AC line variations? We could easily get a ...
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Questions about understanding networks (Telecommunications eng)
So I read about Network topology, about typs of communications like ptp, ptmp, mptmp and about Addressing methods (multicasting, broadcasting), etc...
I'm very confused. What is the difference between ...
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How to convert data signal line coding from RZ to NRZ?
I have a user data stream at 10 kbps and line coded as uni-polar, 0-5 Volts, RZ (return to zero). What methods are there to convert this signal to an NRZ (non return to zero) format?
The only way I ...
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How should I understand this interpretation?
Studying spatial diversity in telecommunication engineering (Fundamentals of Wireless Communication, D. Tse and P. Viswannath), I read this paragraph.
$${\text {In}}\,{\|}{\textbf h}{\|}^{2}{\text {...
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Can I reconstruct the channel impulse response from OFDM least square channel estimation?
I'm working on a successive interference cancellation (SIC) project for an OFDM system.
I used pilots and least square channel estimation to estimate the channel frequency response (CFR.) It works ...
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How to do a comparative analysis of electrical characteristics of two 134kHz RFID circuits?
In the figure below there are two antenna circuits, both are circuits used in RFID at 134kHz, which are external to the TMS3705 IC. Circuit number 1 is an old circuit, circuit number 2 is the circuit ...
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Find Bps given a star graph
Today I wrote finals for the semester in the subject "Introduction to Telecommunications".1 question was like this:
Suppose we have a star graph with 64 dots in it.That would mean we are ...
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How to switch off the CATV signal on a splitter port
I'm trying to create some automation of switching off the CATV signal on a splitter port.
Using a regular 5V Arduino relay module I've tried to interrupt the wire from the center of the coaxial cable ...
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217
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5G and aircraft? [closed]
I just read the statement of a company,
"We are frustrated by the FAA’s inability to do what nearly 40
countries have done, which is to safely deploy 5G technology without
disrupting aviation ...
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149
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Optical Receivers and Amplifiers
I have been doing some past papers for a university module I am studying. I am not from an electrical engineering background so don’t really know how to attempt the question attached. I would really ...
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What is the purpose of a carrier signal in communication technology?
What is the carrier signal for when we actually do not care about this but only about the other signal (the useful signal?)
Why isn't only the useful signal used instead of mixing it with the carrier?...
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114
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Identify this telephony or data connector?
Recently I had the opportunity to visit a telecom/data room that was being decommissioned. A lot of the remaining equipment seemed to be from around year 2000 or so, as best as I could tell.
While ...
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LTE Bandwidth at band edge
If my LTE uplink channel is right on the band 20 edge for example 861.9MHz or 24449 EARFCN and my LTE BW is 10MHz does that mean the final signal would be outside of B20 or 856.9-866.9 ?
Or is the ...
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How are simultaneous transmissions decoded at the receiver?
I am finding it hard to understand how does a receiver differentiate between the interference and the signal intended for the corresponding receiver. For example in a case where two user pairs are ...
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Manchester and NRZ coding schemes
How does NRZ recover the clock? For example, Manchester coding is a self-time scheme, but we still need to have DLL or PLL for the recovery, it can be done without those CDR circuits? and back to NRZ, ...
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What is this circuit diagram found on an FM transmitter?
This is the circuit diagram on the transmitter at a local FM radio station I clean at (I'm a janitor,) but I'm also studying electrical engineering. I'm puzzled by the circuit diagram on the ...
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How to find priori information in Cramer Rao Lower Bound when the pdf of the parameter is unkown
In order to compute a Bayesian Cramer Rao Lower bound, we need to find
the prior information of a random parameter "theta" which is a complex
scalar parameter. The pdf of "theta" ...
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What is 'mis-registration' and 'mis-collimation' of television signals?
I was reading about early televisions and television cameras, and I came across these terms with no explanation....
They appear on Google on a few pages, but again I cannot find a definition....
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NOAA satellite RF superhet receiver - local oscillator frequency precision
I am currently designing a RF receiver for the APT protocol in order to collect NOAA weather images. This has been widely done on the internet, but I'd like to do it from scratch and not use any SDR.
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Dwell time in wireless communication
In wireless communication dwell time is defined as the amount of time a device uses a particular channel. If we take the case of a ...
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What does GSM 900/1800 mean?
I was looking at old Nokia 3310 phones, which have GSM 900/1800.
I did some research online from a government website, along with some Google searches, to understand what GSM 900/1800 means. I got a ...
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Was the last mile copper wire not the limitation in dial-up internet service?
My local internet service providers can provide ADSL (asymmetric digital subscriber line) service at various speeds, for example, 50 M bits per second. This service is in Canada.
Is this typically ...
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Modeling bidirectional communication across a coax?
I was reading about the history of cable internet and I'm interested in a simple model of full-duplex communications across a single coaxial cable. My first attempt is simply a transmission line with ...
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Amplitude Modulation Equation (sine or cosine)
I got an exam tomorrow and I'm still confused with something. I'm sure most people are familiar with the general equation of Amplitude Modulation.
AM(t) = (Ac+m(t))cos ωc t
I found that there is ...
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What do you call the yellow and black conductors in domestic telephone wire?
Any wannabe telco guy can tell you that the green and red pair are called "tip" and "ring" respectively, most can tell you the historical reason why. That's not what I'm looking ...
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Why are power losses in fiber-optical cables so high?
Suppose we have two arbitrary points A and B. Transmission between these points is over optical-fiber. We don´t care the wavelength, distance and other stuff.
Now suppose we have total attenuation of ...
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Transmission Lines:Standaing Wave Voltage Characteristic at Half Wavelength
The voltage equation for lossless transmission line that my professor has given me is :
$$V(l)=V^+ e^{j\beta l} +V^- e^{-j\beta l}$$
and he says that when singals transits by half the wavelength the ...
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Amplifier gain in budget links
How does an engineer calculate the required power/low-noise amplifier gain after she/he is provided with the link budget of the system?
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Why are two capacitors used in capacitive wireless power transfer instead of one?
I am an engineering student. I am studying wireless power transfer (WPT) theory.
I understand that from a theoretical point of view it is possible to do capacitive wireless power transfer using a ...
user274494
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Is it safe to wire a telephone to a breadboard?
I am trying to connect a hardwired 2554 telephone set. There's only a few inches of slack wire coming out of the phone since it appears it was just cut there. I managed to get about half an inch of ...
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Difference between Li2YCY and LiYCY
I would like to ask about the difference between Li2YCY and LiYCY TP cables.
As far as I know, the main difference is that the Li2YCY has core insulation based on PE and wrapped screening made from ...
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Why does a phase shift happen in the demodulated AM signal using envelope detection?
I was studying AM signal demodulation using envelope detection with the circuit shown below.
In the book it says the low pass filter part is called a post-detection filter and that this filter causes ...
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What makes RF transmission so efficient?
I'm a layman in this field. I have a question about RF transmission.
How does the data transferred by RF waves (for example in mobiles, wifi) reach the users accurately in spite of losses during ...
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