Questions tagged [telecommunication]

Use this tag for questions about communications technology and its applications.

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14 views

Calculate the temperature stability of wavelength demultiplexer

Hi ive been given this question: A wavelength demultiplexer (DMUX) used in a DWDM communication system has a channel spacing of 100 GHz. The operating pass band of each channel is 50 GHz. The ...
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27 views

Choosing a Project

Sorry if there’s any spelling mistake... I don't know if this is the proper place to ask, but I guess if it isn't, I'll get notified. Anyway, if it isn't, I apologize. I’m a telecommunications ...
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1answer
19 views

How to make a wireless modem using a normal Wi-Fi router and a 4g usb modem

I have a normal TP link (Model: TL-WR841N) router and an USB 4g modem. But the WIFI router does not have any USB port. I want to connect the USB modem with the router, want to share internet ...
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8 views

Relation between channel and path loss exponent

I am referring a paper "Outage Analysis of Ambient Backscatter Communication Systems" wherein i came across the equation $y_r(n) = \frac{\tilde{h_{sr}}}{\sqrt{d_{sr}^{\alpha}}}+\frac{\tilde{...
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2answers
6k views

Why downlink frequency is greater than uplink frequency in mobile communications?

Generally, downlink freq. > uplink freq. in mobile communications. I was able to gather some answers as to why is so. But my seniors (in my company) seem not to be satisfied with the below answers. ...
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1answer
43 views

Ethernet extender kit claims to send data through power cables - Is this correct?

I own an ethernet extender kit which has two devices connected to mains. Its data sheet claims that the device "your homes electrical wiring to extend your broadband network anywhere in the house&...
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10 views

DSB-AM Spectral Efficiency

I'm studying communication systems and I have a question about Double Sideband Amplitude Modulation as to why the transmission bandwidth is twice the message bandwidth. Is it necessary the message ...
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1answer
29 views

When recording VHS tapes from analogue TV back in the day, was the “Teletext” data also recorded?

Ever since I was a kid in the 1990s, I've been wondering about this. I have never been able to verify/test it in a conclusive manner. It may be almost forgotten now, but in those days, each TV channel ...
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11 views

How to prove Bossert inequality for the symbol error probability?

In the book : Coding theory-Algorithms, Architectures and Applications p.20, the authors have introduced the following inequality ( and precised that it was taken from Bossert's Channel Coding for ...
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43 views

Mesh Wifi Router Network for a Small Village

I was wondering if its possible to create mesh network of WiFi for relatively large area? I am talking about the size of small village (~20km2). The idea is to use centralized connectivity with enough ...
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3answers
124 views

Tethered Balloons vs Towers for Wireless Communication

If we use tethered balloons (aerostats) with wireless gateways fitted on them (let's say for Cellular or LPWAN communication), they can provide much more coverage owing to the height they can reach (e....
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12 views

LTE coverage signal for different category

Been asking this earlier in Electronics, Cellular provider said they mostly have LTE CAT 6 signal on my area, will that means i am able to use them for other LTE's lower than that category? Or they ...
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36 views

Why radio communication was limited to military use and did not become popular with general public like cell phones have become today? [closed]

Why did no private company or government try to bring radio communications to general public like we have cell phone today? What were the hurdles and challenges?
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1answer
57 views

How were the tones for DTMF chosen?

In my limited engineering knowledge, and limited research skills, I couldn't find a complete answer for the reasoning behind the chosen tones for DTMF. I did find a hint that said something about ...
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0answers
9 views

Monitoring Connectivity on ZigBee

I am trying to figure out some ways in which a ZigBee network can be monitored. As is the case in any network, here we have a central coordinator and several slaves joined, however, there seems to be ...
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3answers
87 views

Bandwidth vs Capacity

Two questions on wireless transmission, packed into one. First: I am confused about the meaning of the term 'Bandwidth' in a wireless transmission environment. The two most common definitions I could ...
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1answer
37 views

How progressive scan televisions works in depth?

I'm trying to understand in depth the behavior of progressive scan TV monitors (LCD/LED - Digital Television). From what we already know, the tv's screen scans the image row by row (as rolling shutter ...
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2answers
50 views

With the “plain old telephone system”, would two neighbors be able to call each other privately?

Suppose that Joe and Sue are neighbors out on the country. The year is 1950. But it could also be 1975. Or even 1999. Even though they live next to each other, and can see each other through the ...
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3answers
110 views

Would not a telephone call (from the late 1950s) auto-disconnect if one of the parties “closes the handle”?

In the Alfred Hitchcock Presents episode "Togeather", S03E15, at 17:17, you see a drunk man leaving a telephone without putting it on its handle, with the person he was talking to begging him to "...
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1answer
45 views

How is it possible that an *undertaker* invented the automatic telephone exchange? And as early as in 1888?

Strowger, an undertaker, was motivated to invent an automatic telephone exchange after having difficulties with the local telephone operators, one of whom was the wife of a competitor. He was said ...
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9 views

how to implement an encoder in matlab

How can I encode a quantized vector in matlab ? This is a part of a problem where I am asked to implement a communication block using matlab.
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1answer
34 views

Fourier serie signal approximation

I have to approximate the red function with Fourier harmonics. I am calculating complex Ck the following way. I am not sure what to put for period - T (6 or 2pi or what?). What integral limits to ...
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0answers
50 views

LTE to 3G IRAT Handrover: What happens afterward

Let's say that there has been a handover from LTE to 3G of a particular UE. Once the handover is complete, the MME is no longer required to maintain the sessions/bearers that has been established for ...
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0answers
99 views

Negative transmit power in dBm

I am calculating the transmit power for $K$ single antenna IoT devices in an Indoor scenario. The receiver has 64 antennas. I am trying to minimize the transmit sum-power, i.e., $\sum_k p_k$, where $...
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1answer
60 views

Electronic symboles in datasheets

I found these symbols in a electronic datasheet.. Are these all logic gates? or another?
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1answer
208 views

Why is Morse code used in satellite communication compared to ASCII encoding

My knowledge about methods of transmission of data is limited, but I believe that communication between transmitters and receivers often uses Morse code to send information. If say, a satellite ...
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78 views

Is it better ASTRA 19.2°E or 28°, in central continental europe?

I'm trying to tune my satellite receiver, particularly to receive the signals of the Astra satellites, which are ASTRA 19.2E and ASTRA 2 at 28º East. Looking at the picture the signal from ASTRA 28 ...
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1answer
4k views

What is the difference between Bluetooth Low Energy and Bluetooth BR/EDR in Park mode?

It is known that Bluetooth Low Energy transmits data only during short time intervals called Connection Events. Connection events occur regullary with predefined period. The rest of the time Bluetooth ...
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0answers
97 views

Spectral Efficiency of FDD, TDD, and FD

I would like to show at high level that, in principle, the spectral efficiency (SE) of frequency division duplex (FDD) equals the SE of time division duplex (TDD) and both of them are half the SE of ...
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0answers
39 views

Non Orthogonal Multiple Acess and Channel Quality Indicator

As we know in a 4G network, the LTE give us a correlation about the SNR of user and the data rate of the user. This correlation is usually a table called Channel Quality Indicator (CQI) which is found ...
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1answer
144 views

Why does the LTE Specification define SC-FDMA as the modulation scheme for the reverse link?

The LTE specification specifies SC-FDMA as the encoding scheme for the reverse link (mobile to base station) when the forward link uses OFDMA. What is the reason for the difference?
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42 views

How EnB will inform to UE about incoming call in RRC connected state in LTE?

Generally if UE is in RRC Idle state, ENB will inform to ...
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0answers
29 views

Mobile Frequency and Carrier Frequency not Matching

I am using a Google Nexus 6 Mobile in India with Airtel as Network Provider. Recently Airtel has upgraded their Network to 2300 Mhz 4G. Whereas Google Nexus 6 Operates on Band 3 (1800Mhz) LTE. When ...
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1answer
60 views

Material to absorb very low frequency radio

Is there any material that will absorb very low frequency radio light? I know that stealth aircraft use radar absorbant materials in their design that absorb radio light best at certain frequencies, ...
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1answer
55 views

What is the purpose of colour code for telephone wires?

I'm trying to understand how telephone wires work. I've stumbled upon this kind of identification method with colours. I can't manage to understand the reasons why is used and if it's still common to ...
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1answer
29 views

why can't remove the Image frequency using a band-pass filter?

why can't remove the Image frequency using a band-pass filter? I've been asked to search for the reason why we can't use BPF (band-pass filter) in order to remove the effects of the Image frequency? I'...
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0answers
17 views

Modeling of a Wireless Channel with known BER

I have to model through software a wireless (my choice: 3g,4g, 802.11...) channel with given Bit Error Rate. I'm searching some distributions, I'm reading tons of papers but I can't find how to ...
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1answer
39 views

ADSL near end crosstalk (NEXT)

During a lecture my teacher told me that the UPSTREAM in ADSL is very much affected from near end crosstalk due to DOWNSTREAM, while DOWNSTREAM is not affected by this phenomena. This lead to the ...
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1answer
108 views

What is tonal masking?

I have checked the definition of tonal masking on Wikipedia and google but I saw the definition of sound masking and auditory masking. Auditory masking Sound masking But I want to know what ...
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1answer
38 views

Propagation loss in USRP antenna

Problem I have two USRP antennas close to each other. I know that signal strength on the receiving end has to be at least -80 dBm. Both antennas have 2 dBi of gain. I want to compute what ...
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49 views

What are the strengths and limitations of the antenna design of the Montjuïc Communications Tower?

The Montjuïc antenna is an interesting design for an antenna. I presume the design is principally an antenna, but perhaps it is not? If the ring + mast is an antenna, how does the ring work to ...
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1answer
45 views

A radar that is not an OTH detection distance

Let's say that we have a radar that is not an OTH on a boat, and it is placed 30 meters above the ground. Is there a way for it to detect an offshore platform 152 kilometers away from it, since the ...
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0answers
48 views

How can the Microsoft and the Facebook Fibers reach 160 Tbps between Virginia and Bilbao?

According to this article, Microsoft and Facebook have completed a 160 terabits cross-Atlantic cable. Based on my calculations, this doesn't seem probable, so what did I miss in my calculation? The ...
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2answers
86 views

How do I get data from my Hardware to server or so? [closed]

Brief I am actually of 17 not even in college but I have dream for making my project/dream/aspiration/or So to come true so I am thinking of making a device that performs a function say like ...
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0answers
59 views

Can a casio fx series do this operation?

"Calculators stackexchange" doesn't exist, so I guessed this would be the right place to ask. Can a calculator solve $-0.2 \cdot e^{-0.06-4.2i}$? Or any $e$ to a complex for that matter. I've been ...
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1answer
41 views

Why only the spectrum range of radio waves can be reflected from atmospheric layers while higher ranges (Infrared-Visible Light-Ultraviolet) can't?

From communication prospective why can't higher frequency ranges be reflected from atmospheric layers and what is the effect of parameters (like temperature, pressure, etc) of the atmospheric layer on ...
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2answers
450 views

Why does India have more than 1 MCC (Mobile Country Code)? [closed]

I was checking the list of MCC (Mobile Country Codes) on Wikipedia and found that India has two MCC: 404 and 405. 404 contains only GSM/UMTS/LTE operator bands and 405 contains both GSM/UMTS/LTE and ...
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1answer
117 views

How does 4G know the reception of a voice call?

I know that the 4G network is only for data and doesn't support voice calls. Most of phones switch to 2G/3G when receiving a voice call. But my problem is how does the phone gets to know about the ...
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30 views

How does the demapping/demultiplexing of transport channels to logical channels work?

I am trying to model WCDMA MAC, but I cannot figure out how to demultiplex HS-DSCH unto DCCH, DTCH. Also, since I am using E-DCH/HS-DSCH transport channel scheme, how does the data of DCCH and DTCH ...
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1answer
46 views

Sending SMS using car horn [closed]

If you've been watching Bones series, there is an episode in which Bones and Hodgins were trapped beneath the ground, and they managed to send an SMS by wiring the phone to the car honk. Is this ...