Questions tagged [telecommunication]

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

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12
votes
4answers
782 views

Is interference between aircraft an issue for fly-by-wireless technology?

I was reading up on fly-by-wire development, and I saw a short section about fly-by-wireless technology. It seems like a great idea, with the potential to lower costs, weight and complexity. I can see ...
9
votes
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 ...
8
votes
3answers
539 views

Protecting device from microwaves in microwave oven.. but allowing Bluetooth?

I am building a device that needs to be inside of a microwave oven but somehow needs to communicate with another device outside of the microwave. How can I reflect microwaves so they don't come into ...
8
votes
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?
7
votes
0answers
518 views

BER peroformance of MPSK and MQAM in Rayleigh fading channel

I have a question regarding bit error rate (BER) performance over the Rayleigh channel. I observed BER performance over the AWGN channel using Simulink in MATLAB. I used to change the "SNR" parameter ...
6
votes
0answers
538 views

How does LTE eNodeB set the Base Station output power?

I'm interested into the power radiated out of an eNodeB (LTE/4G) radio base station: which parameters does this power depend on, if they are constant or relying on the environment... All of this in ...
5
votes
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 ...
5
votes
1answer
2k views

Why do bluetooth headsets get interference (choppy sound quality) outdoors?

This is more of a general physics question to help me understand how to choose sports headsets in the future, however it is too specific to a certain use case (bluetooth headset) to belong in the ...
4
votes
0answers
181 views

LTE channel characterization from Time Domain waveform

I am currently interested into the diverse Downlink LTE channels broadcasted over air after some (QPSK, 16QAM...) modulation. More precisely their waveform. I would like to know if, with a good ...
3
votes
1answer
2k views

What are the pros and cons of between Zigbee and Z-Wave communication protocols used in IoT device space?

Recently, both Zigbee and Z-wave tend to be the most commonly used protocol to communicate between Internet of Things (IoT) devices. Most of these IoT devices tend to have a combination of mechanical ...
3
votes
1answer
914 views

signal-to-interference-plus-noise ratio (SINR) and others calculation

I am considering some empirical signal propagation models (like Hata, Ericsson models) to calculate 4 parameters: Path loss Received Signal Strength (RSS) signal-to-interference-plus-noise ratio ...
3
votes
2answers
5k 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. ...
3
votes
0answers
132 views

How is modulated the Primary Synchronization Signal in LTE?

PSS is based on 62 values from a Zadoff-Chu sequence. Three different sequences can be used by an LTE Cell, to represent the Physical Cell ID within the Cell ID group. The formula is the following, $...
3
votes
0answers
45 views

What is PSS waveform formula?

I want to know how is exactly modulated a LTE subcarrier. Since I'm working on Synchronization Signals (P-SS, S-SS) the subcarriers I'm talking about are centered around DC. I have coded the ...
3
votes
0answers
107 views

FM transmission exercise

I'm encountering some troubles while trying to solve this exercise. Let us consider a radio link between a geostationary satellite and a ground station. We send a binary signal (represented by two ...
3
votes
0answers
53 views

Viability of creating a wireless LAN bridge between mobiles and PCs using a portable router? [closed]

I am creating a network to share files between a mobile device and multiple PCs directly through a LAN. The purpose of which is to use smart phones to capture files from remote devices which are ...
3
votes
0answers
49 views

Wifi modulation and standard interoperability

I've been reading this summary(info.tek.com) of Wifi standards from Tektronix, which seems to do a pretty decent job of explaining things, but has left me with a couple of questions: For access ...
2
votes
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 "...
2
votes
1answer
121 views

Why is WiFi increasing frequency?

WiFi at 60 GHz provides a theoretical data-rate of 7 Gbit/s. The trade-off is limited range and penetration. The main reason for this awesome data-rate is a 9 GHz bandwidth, from 66 GHz to 57 GHz. I ...
2
votes
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 ...
2
votes
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 ...
2
votes
1answer
347 views

A 40MHz oscillator in usb wifi adapter

I disassembled a usb wifi adapter. I was surprised to see a 40MHz oscillator, when wifi works at 2.4GHz. How the output of the oscillator is scaled to the required frequency?
2
votes
3answers
203 views

Why not only GSM (3G/4G/..)? Why do we need Bluetooth, Wifi,etc…?

It is quite frustrating to have multiple adapter for connecting to desktop. For example, if I want to connect my phone to desktop I need Bluetooth/wifi; why can't I just just use the Mobile's main ...
2
votes
1answer
116 views

Why is Li-Fi faster than regular wifi?

I was wondering, basicly every radio-transsmission works with electromagnetic waves which travels at the same speed whether I modulate the information with a low frequency or high frequency such as ...
2
votes
1answer
42 views

What is the thinnest possible depth of any given material required to display an image? [closed]

I am interested in creating a screen to display moving images (similar to moving desktop background), however I am looking for the thinnest possible material available i can use as the screen to ...
2
votes
1answer
2k views

What kind of signal is the signum function? A power signal or an energy signal?

I'm studying "signals and systems". We can indentify two kinds of signals: power signal and energy signal. The definitions are: Energy of a time-continous signal $$ E_x = \int_{-\infty}^{+\infty}{|x(...
2
votes
2answers
249 views

Control RF wave direction or path

I have a rf module transmitting from an antenna. As you see in Figure 1, I have a radio mast that sends waves in all directions. I don't want this. My plan for controlling wave direction is Figure 2. ...
2
votes
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 ...
2
votes
1answer
196 views

Hilbert transform LTI

I'm studying the Hilbert transform and its properties. I found out that Hilbert transform can be considered as a linear time-invariant system. How can I show this? I guess this should be trivial as ...
2
votes
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 ...
2
votes
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 ...
2
votes
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 $...
2
votes
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 ...
2
votes
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 ...
2
votes
0answers
54 views

Effect of bad weather on P2P Communication or Broadcasting?

I stop receiving TV signals whenever their is cloud cover outside. On the other hand I have never had any such problems with my internet connection or GPS system. I cannot understand why and how often ...
2
votes
1answer
87 views

How does a carrier signal work from a receiver's perspective?

for example : Sender: A cellular signal tower(Base Station(BS)) sends data(voice, GPRS, VOIP) to the cellphone. The sender will obviously have the carrier frequency and more power(voltage+current) to ...
1
vote
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 ...
1
vote
1answer
67 views

Will the water in a gold fish bowl signficantly abosorb Bluetooth or WiFi if transciever is at bottom of bowl?

Using WiFi or bluetooth frequencies 5.8GHz and 2.4-2.485GHz respectively, I want to place a hermetically sealed circuit at the bottom of a gold fish bowl, and want to know if the water will ...
1
vote
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 ...
1
vote
1answer
60 views

Electronic symboles in datasheets

I found these symbols in a electronic datasheet.. Are these all logic gates? or another?
1
vote
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'...
1
vote
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 ...
1
vote
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 ...
1
vote
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, ...
1
vote
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 ...
1
vote
1answer
132 views

How to join between two PBX telephones wirelessly?

I have two PBX telephones. Each one has a line cables to the houses, but there is no connection between these two pbx telephones, neither wire nor wireless. How can I join between them wirelessly? ...
1
vote
0answers
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 ...
1
vote
0answers
42 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 ...
1
vote
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 ...
1
vote
0answers
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.