Questions tagged [telecommunications]

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26 views

CDMA in FHSS system

I am having difficulty finding information about how is CDMA used in a FHSS system. In wikipedia, it mentions: FHSS is used to avoid interference, to prevent eavesdropping, and to enable code-...
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1answer
59 views

How to pick an amplifier for very fast transient signals?

I'm coming to this with a Physics background. I work in solar cells. I would like to flash the solar cell with a laser and measure the voltage response. The University has a spare 10 GSPS (gigasamples ...
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0answers
29 views

Decode a WCDMA signal

I am trying to decode a WCDMA signal on MATLAB and I am having some trouble trying to grasp the concept of it and was hoping for some feedback. I have a row vector, 'scrambleCode,' containing 38400 ...
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1answer
61 views

Nearby jail's signal jammer affecting cellphone and devices using 2.4GHz band

I just rented an apartment that seemed perfect at the first sight. However, once I moved in, I noticed a lot of instability on my cellphone signal. I found that odd, so I did some research and ...
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1answer
85 views

What is the benefit of dual polarization in radio communication?

Why are some PtP antennas and radio units connected by two feed lines -- one for horizontal polarization and one for vertical polarization? I know the difference is in the orientation of the electric ...
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0answers
76 views

Help identifying mysterious communications tower

There's a tower near my house that I thought was a cell tower, but I noticed it's not registered on the FCC map. Can anyone help me ID what type of tower this might be? I was thinking it was a ...
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1answer
57 views

Finding upper cutoff and lower cutoff frequencies on notch circuit

I need to find upper cutoff (UCF) and lower cutoff (LCF) frequencies based on formulas of a notch circuit, but I'm getting a quadratic equation (as expected) with an imaginary number (IN; not expected....
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0answers
43 views

Leaky Bucket Example

I have an image below of a leaky bucket image that I am trying to understand for my telecommunications class, and I was hoping for some guidance/verification if my train of thought is on the right ...
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0answers
30 views

How can one compare resonant and non resonant antenna based on parameters like Directivity, Radiation resistance, Cross polarisation, Efficiency?

Basically I want to make a choice between two antennas when ample space is given objectively based on parameters 1.Directivity 2.Radiation Resistance 3.Cross Polarization ratio 4.Loss resistance I'll ...
2
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1answer
393 views

What is difference between resonant and non resonant antennas?

I don't know if it's right place to ask it, but I searched google and books the answer I get seems to be like resonant antenna have small bandwidth and have standing wave instead non resonant antennas ...
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4answers
528 views

How was the first overseas phone call possible back in 1927?

I was watching the Peaky Blinders TV Series when something triggered my curiosity: If there were no satellites, nor underseas cables, how come the characters were making overseas phone calls? After ...
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2answers
76 views

Can optical fiber communication be used to transmit analog signals?

I am confused because I read the LEDs/LASERS used in optical fiber have finite levels. If for instance ASK is used to transmit digital baseband data then will the LED or LASER be able follow the ASK ...
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2answers
123 views

How does ISP cut the customer's internet access technically?

We know that if we fail to pay our internet bill then our internet access will be cut. But how does the ISP technically cut the access? For wired internet, do they just shut down the port where the ...
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1answer
36 views

About best way to perfom checksum

From my knowledge,checksum can be done using Xor or adding the bytes of the frame...i have to create a communication between ATmega32 microcontroller and matlab to perform some functions...which is ...
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1answer
25 views

Calculating link budget

I was reading and found that there are different ways to calculate "link budget" and I want to know which one is correct because they are confusing to me. For example, some sources state ...
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1answer
54 views

How are LAN routers, WAN routers and eNodeBs connected to each other (TCP/IP)? [closed]

I'm new to telecommunication, and from what I understand, an user equipement is either connected to a LAN router or an eNodeB, and a LAN router is connected to a WAN router, and routers send the ...
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2answers
133 views

What are the units used in Shannon formula calculation?

I'm a CompSci student with absolutely no background in wireless communication who recently needs to do something with the Shannon formula: $$ R = W log_2\bigg(1+\frac{P_t H^2}{N_0 W}\bigg) $$ I need ...
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1answer
33 views

Equivalent baseband communication channel

I was reading on my lecture slides (I do not put them here since they are not in English) this statement about equivalent baseband channel models: In typical wireless applications, communication ...
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0answers
26 views

Which RF technology can be used between GNSS-based base and rover module?

I am looking for an RF technology/module/modem that is used to send RTK RTCM data from GNSS-based base module, to GNSS-based rover module (one way communication). I have few criteria to be considered ...
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1answer
37 views

why base stations have 2 receiving antenna and only one transmitter?

I read that a base station is divided up into sectors to accommodate multiple service providers on a single tower. why each sector has two receiving antennas and only one transmitting antenna, As we ...
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1answer
36 views

Understanding OSI Communication Model in Hardware

I have gone through the OSI communication model and the associated levels. But I do not understand on how is this implemented in the Hardware level. Or let me put it like this. Suppose we have a ...
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1answer
38 views

What is the relation between bandwidth and data rate?

If I have a 20Mhz bandwidth provided by my 2.4ghz router then will my internet speed will be 20M symbols per sec which is equal to 20×4= 80Mbps (considering 16 qam modulator with 4 bits per symbol) Is ...
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2answers
70 views

How do we separate source signals in spread spectrum?

In a point-to-point mode, that is, one transmitter and one receiver, I understand how a spread spectrum receiver can read the transmitted signal from a spread spectrum transmitter by knowing the code. ...
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0answers
21 views

Is \$ H\left\{x_h(t)\right\} = H\left\{x\left(t-\frac{\pi}{2w_c}\right)\right\} \$ where \$H\$ is Hilbert transform

Accordind to my understanding of the following: $$H\left\{X(f)\right\} = -j\;sgn(f)\; X(f) \qquad(1)$$ my work so far: since \$ x_h(t) = x\left(t-\frac{\pi}{2w_c}\right)\$, Their Hilbert ...
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0answers
17 views

Do all random access procedures and packet transmission in NB-IoT happen during one Nprach-periodicity?

I have two questions about random access procedures of NB-IoT In NB-IoT, Nprach-Periodicity is the amount of time between two consecutive random access transmission attempts. Random Access procedures ...
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1answer
57 views

Calculate power of an LTE Signal

I am looking for the formula to convert the power level of an OFDM RF signal to an absolute power level. For example if I have my typical rectangular RF spectrum and the bandwidth of the signal is ...
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1answer
36 views

Do pieces of wire or metal in general affect the inside of a Faraday cage

Building a Faraday cage and wanted to know do the dozens of metal staples and several small pieces of wire have any effect in terms of acting as an antenna?
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1answer
142 views

Why use both high side and low Side diode-ORs for redundant power?

This question is in regards to an example application circuit that appears in the Linear Technology / Analog datasheet for the LTC4355, and is discussed in this article. The circuit uses ideal diode ...
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1answer
68 views

How could a digital multiplexer transmit at a rate higher than its input?

From Wikipedia, "a multiplexer, also known as data selector, is a device that selects between several analog or digital inputs and forwards it to a single output line." https://en.wikipedia.org/wiki/...
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0answers
188 views

What’s this slim rectangular box on my utility pole?

It’s the silver box on the utility pole here:
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0answers
121 views

Why are tv aerial cables so mysteriously sensitive to their positioning and the proximity of people?

Digital TV Reception is not great in our area and sometimes we lose reception when conditions aren't favourable. Being UK Freeview, I'm pretty sure it uses the DVB-T2 standard. Anyway, when ...
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2answers
62 views

What is the price of increasing the QAM number?

In a QAM modulation scheme, you have a certain number of possible states which have different amplitudes/phases (like 4-QAM, 16-QAM). If you increase the number, for example switch from 16-QAM to 64-...
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2answers
31 views

Compatibilty between GPRS and LTE modules and networks [closed]

I summerized the question for ease as follows: Lets say we have an LTE module under the coverage of an old base station like 2G with GPRS. Will the LTE module work? Lets say we have a GPRS module ...
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0answers
36 views

Why does multipath impulse response contains a complex phase shift?

The multipath impulse response is defined as $$h(t) = \sum_{n=0}^{N-1} A_n e^{j\phi_n}\delta(t-\tau_n)$$ My qustion is, from intuitive point of view, why is there a complex phase change of the ...
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1answer
202 views

Guard Band Reduction in 5G compared to 4G

Why is there less guard band required for 5G as compared to 4G .For 4G guard band are defined to be 10% of bandwidth on each side while guard band for 5G are defined in 3GPP 38.101-2. For ex If we ...
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1answer
61 views

Gaussian Channel: Capacity and Explanation

Let's consider a gaussian communication channel, which is represented through this scheme: Starting by this assumption it is possible to prove that the channel capacity is equal to The computation ...
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1answer
128 views

First bit of NRZI

I was searching for Non-Return-to-Zero Inverted, but no references I couldn't find any reference about the first bit in NRZI. I know that, in NRZI, 1 refers to <...
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1answer
59 views

CDMA basic working principle

I find it hard to find on the internet a simplified explanation of the principle of operation of the CDMA system. Could you give me an example of how it works and how a receiver can correctly identify ...
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1answer
62 views

Shannon - Hartley Theorem

Let's consider the Shannon - Hartley formula for the channel capacity \$C\$: $$C = B \log_2 (1 + S/N)$$ I have two doubts about it: 1) is it correct for TDMA, FDMA, or CDMA? And why? 2) Can a ...
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5answers
3k views

How are unbalanced coaxial cables used for broadcasting TV signals without any problems?

As far as I know, in telephony STP or twisted pair cables are used. This creates balanced line impedances which is useful to mitigate for common mode related interference. So using balanced cables in ...
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2answers
295 views

Is there any relation between LJU (Line Jack Unit) and broadband speed? [closed]

My question is about LJU (Line Jack Unit) aka Rosette. I am having BSNL (service provider company) copper line broadband in India. In spite of having wired broadband, I get speeds of 6Mbps(download)...
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1answer
83 views

Grounding for surge protection for telephone/internet/data lines

After my router broke in a thunderstrorm, I am trying to establish surge protection for power lines as well as (this question) for telephone/internet lines. I found devices such as Tupavco TP302, ...
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1answer
52 views

Telephone Call and Electromagnetic Waves [closed]

Can you give me a simple explanation of how do telephone calls work? I know that when I receive a telephone call, it means that my mobile has just received a certain Electromagnetic field. But in air ...
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1answer
57 views

Radiofrequency exposure from portable (vehicle-mounted) satellite uplink antennas

I came across these broadcasting vans recently in London. The antenna that's deployed I think is a Vislink Advent uplink antenna, similar to this model, designed to transmit to satellites for ...
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2answers
99 views

What misconception about telephone circuits are they trying to address?

I'm reading a book called "Telephony" published in 1905 (Miller,Mcmeen). The book starts with this quote: To properly understand the manner in which sound is transmitted from one end of an ...
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1answer
103 views

Is an FPGA the best tool to generate a continuous flow of square pulses with arbitrary amplitude?

I need to generate a train of rectangular pulses, with positive and negative arbitrary amplitude. Ideally, I would like to have the generation electronics connected with a computer, and I would like ...
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2answers
81 views

How does line encoding relate to bus protocols like SPI, serial, i2C, ethernet etc [closed]

I'm referring to line codes like bipolar, machester, miller etc... https://en.m.wikipedia.org/wiki/Line_code How do these line codes relate to bus protocols? Is it another level down? Is it ...
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0answers
55 views

How to choose an antenna for an FM transmitter? [duplicate]

Ok guys I can't understand something. Say that I have this circuit: Assuming that I apply at the antenna 5V, how can I calculate how much power I will trasmit? I found on internet that the current ...
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1answer
91 views

Can I use a Ku band satellite dish for Wi-Fi?

Satellite TV works at 18-24Ghz and WiFi at 2.4Ghz, will a T.V dish antenna work for WiFi? Diameter of the dish is about 60-90cm
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1answer
551 views

Why did CATV standarize in 75 ohms and everyone else in 50?

All of the CATV industry runs on 75 ohm systems, while most of the rest of the radio world uses 50 ohms. Why was this standard chosen? I was wondering this because good quality RG6 cable can be ...