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Questions tagged [telecommunications]

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0
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2answers
122 views

Why aren't tethered balloons used instead of Cellphone towers? [closed]

If we use tethered balloons with wireless gateways fitted on them (let's say for Cellular or LPWAN communication), they can provide much more coverage. Why aren't they used then? While there are many ...
0
votes
1answer
28 views

How can Erlang C values be greater than one?

Here is an Erlang C plot I did myself. The x-axis represents the total traffic while the y-axis represents the probability. Each line represents a different total number of channels. As you can see, ...
1
vote
1answer
43 views

Why are Erlang B and Erlang C formulas different?

Erlang B determines the probability that a call is blocked and is defined as: $$Pr[blocking]= {{A^C \over C!} \over {\sum_{k = 0}^{C} {A^k \over k!}}}$$ while Erlang C determines the probability ...
0
votes
0answers
13 views

Find a particular TMSI during paging in GSM

I have read that Mobile Stations (phones) in a particular Location Area are paged using TMSI (mostly) during an incoming call. This paging signal is destined for all Mobile Stations. I would like to ...
0
votes
4answers
117 views

TDMA in telephone circuit switching - isn't there delay in transmitting a particular user's speech? [closed]

Let's do a simple case on the left with X and A user telephones. So the way an analog signal (user's speech X) is handled, is that it is sampled at 8000 bits / sec. The high-speed C-channel has 128 ...
1
vote
1answer
70 views

Some sort of Sim card in Fax machine

I took apart our old Fax machine. And I found some weird Sim Card (See size compared to a regular sim card). I wonder what such a card is doing in a fax machine. Also I'm wondering what else I could ...
-2
votes
1answer
99 views

What is needed link budget? [closed]

Assuming I want to send a signal 1 km away from a 2.4 GHz antenna with 5 DBI gain and recieving antenna of 2.15 DBI gain. What is the minimum needed power at the receiver (not the minimum transmitter ...
0
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5answers
288 views

Why are cell towers so high? [closed]

Why do cell towers need so much height? Does the height increase antenna gain because it may provide directionality?
-1
votes
1answer
195 views

Why microwave links on cell towers have high frequency?

Why microwave links are in the higher microwave spectrum (I don't know exactly but I guess it's around 20-40GHz). If by Friis Equation higher frequencies have lower range then why use higher frequency ...
1
vote
1answer
148 views

How can a phone transmit the signal back to tower? [closed]

If cellphones have such a low power transmitter (around 200mW for LTE) and also doesn't have directionality then how can they talk back to the tower even though they are so powerful and built ...
-5
votes
1answer
137 views

Do the FCC's regulations make any sense?

I have read on the following page that the maximum permissible exposure MPE standard FCC have is 1 mW/cm2 for RF wave above 1500 MHz for general population. http://www.rfcafe.com/references/electrical/...
-2
votes
2answers
100 views

Why FM has larger range than cellular network [closed]

I can receive FM signal about 50km away from the transmitting station but I lose signal from cell towers in about few km (1-3km)
-3
votes
1answer
56 views

How cell sites work? [closed]

In Mobile communication, how do cell sites communicate to each other to the point when they reach the cell site which is connected to the other mobile phone when I make a call . What is the medium of ...
15
votes
3answers
4k views

Why does WiFi have a shorter range than LTE? [closed]

It seems confusing that my phone receives -87 dbm LTE signal and shows a full 4 bars with the speeds of UPLOAD: 20Mbps DOWNLOAD:13.6Mbps But my WiFi is showing 1 bar at -89 dbm and I get ...
-1
votes
1answer
110 views

How can a pringles can act as WiFi booster? [closed]

How does a wifi transciever placed inside a Pringles can act as a wifi signal booster. I saw this trick on Mr robot TV series. Do WiFi routers emit less power than GSM or LTE. I know for : GSM - 2W (...
0
votes
0answers
43 views

What is the difference between Antenna port and Physical Antenna in LTE?

I have just started working on the 5G NR physical layer and I have difficulty understanding the concept of Antenna Port at the downlink. In release 10 there supposedly 15-22 antenna ports for CSIRS (...
0
votes
1answer
50 views

Meaning of Evolution in LTE (Long-Term Evolution)

The term Evolution/Evolved (E) is everywhere in communications, and simply put i don't understand why. The answer I am looking for is one that will help me know what meaning i should associate with ...
1
vote
1answer
42 views

Decide coherent time and fade duration through empirical studies on the channel and relate them to channel modeling

I. Scenario: TX floating in the lossy heterogeneous medium with undetermined positions within a limited region; RX fixed in the air and closed to the boundary of air-lossy medium; Frequency: 500 MHz ...
-2
votes
1answer
115 views

How does cellphone idle time work?

Imagine a basic cell phone which operates in only 2G network and able to provide voice call & SMS service. Does this cell phone transmit any data to BTS in idle time (that is when the cell phone ...
0
votes
1answer
32 views

Xbee pro s2c 2.4 ghz 10dbi Antenna and its effect

Just wondreing how to increase the range/distance of communication between two xbee modules operating in API mode, we are considering to replace the 2.4 ghz antenna of 5dbi gain with 10dbi high gain ...
1
vote
1answer
68 views

What is the difference between SNR of a wideband system and the SNR for a narrowband system

I was reading Wireless Communications by Andrea Goldsmith in the book the author has stated that the Noise power for a wideband system with Bandwidth B is (B*N/2). Could someone help me understand why ...
1
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0answers
59 views

20 mA current loop speed/distance trade offs?

By 20 mA current loop, I'm referring to digital current loop communications, e.g. the standard used by old Model 33 teletypes. (Image credit: By Rama & Musée Bolo - Own work, CC BY-SA 2.0 fr, ...
0
votes
1answer
30 views

Delta Modulation Frequency in the Integrator

Ok guys, I can't understand a thing, I have made this circuit, that is a delta modulator: As you can see with an input of 5Vpp, in the output of the integrator I found a square wave signal, that has ...
0
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0answers
29 views

Who assign MNC LTE values in the USA

I'm working on an up and coming project for a company involving private LTE networks. We're working on our long term strategy and it came up that the IMSI values that uniquely identify SIM cards on ...
0
votes
2answers
34 views

what is the performance of an OFDM system in one-path channel (Flat response channel),with no multi path propagation?

i work on modelling a OFDM system in a indoor optical wireless channel (LOS channel), since my channel is LOS there is no multi -path propagation , so the delay spread of my channel is much smaller ...
1
vote
1answer
233 views

Transform a sinusoidal wave into a square wave with op-amp

Ok guys, I can't understand a thing, how can I turn a sinusoidal wave into a square wave with an op-amp, for example watch this image: If you pay attention, you can see in the bottom of the image a ...
0
votes
1answer
130 views

What is mean by channel inversion in wireless communication

Regarding the title of the question, to my understanding, Channel Inversion means that "The transmitter adapts its power to maintain constant SIR at the receiver." It is a technique used for ...
0
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0answers
20 views

Practical assumptions for accomodating cellular, D2D and M2M devices

Question: Given Assumption 1 in a network model which accommodates device-to-device (D2D) communication within a cellular network in the underlay and overlay, make an assumption to accommodate machine-...
0
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0answers
25 views

Addition of Successive-interference cancellation in wireless transmission

I am looking to integrate the Successive-Interference Cancellation (SIC) technique into my system and would like to know if the following would work. Let me first explain the system as \$I_c\$ is ...
0
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0answers
47 views

What are the stationary & non-stationary characteristics of a channel?

I am not sure if this is the proper stackexchange site to ask this question but I couldn't find a dedicated telecommunications ask & answer site. dsp.stackexchange.com would be an alternative too ...
1
vote
1answer
53 views

Number of point to point link

I dont know if this is unrelevant here but i wish if someone could help me . The number of point to point links required in a fully connected network for 50 entities is (a) 1250 (b) 1225 (...
0
votes
5answers
749 views

What is the difference between narrowband and wideband?

Im a bit confused between the difference of Narrowband signals and Wideband signals. Is there a specific value of bandwidth which classifies a signal into Narrowband or Wideband? What values of ...
0
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0answers
39 views

RAKE reciever intuition

So I was reading answer by Jerry Coffin on question "how RAKE receiver works" but couldn't ask further questions since I don't have 50+ reps: How does a CDMA Rake Receiver work? Further questions: ...
1
vote
1answer
56 views

Problem understanding CDMA and W-CDMA

I found it relatively easy to understand TDMA and FDMA but I just can't figure out CDMA and W-CDMA. For CDMA I think it is something like TDMA without time slots. At transmission side you can use ...
0
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0answers
29 views

Channel Distribution for OFDM

If we know that a channel is going to perform in a way such that the sum of E[var(|h|^2)] is going to be 1.? Is there a way we can simulate this channel on Matlab ...
1
vote
2answers
225 views

A Funny-Looking Sign Off on Television (Test Pattern Generator Image) [closed]

I came across this display on television while I visited the island of Mindanao in the Philippines in November 3, 2017. I thought this might be a sign-off display from a TV network, but I noticed that ...
1
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3answers
89 views

Wireless channel interpretation [closed]

Is there a way to estimate how fast a channel changes with respect to time in practical applications? While evaluating doppler effect for a user we use the frequency at which the channel changes. How ...
0
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0answers
53 views

Autocorrelation function of a DSB modulated signal?

I'm trying to follow an example in a textbook that has a solution and I'm struggling to make a jump that they are making. Suppose there is a DSB modulated signal u(t) with an unknown message signal m(...
3
votes
1answer
522 views

SIMCOM vs UBLOX [closed]

I would like to know what are your thoughts on the following below. I am designing a GSM tracking device with a SIMCOM808 module and I am speaking to an antenna supplier that advises me to rather go ...
0
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0answers
183 views

Telephone line isolation

I have a small problem. I have a fiber connection at home, and I want to power both the router and the cordless phone attached to it from the same power supply. Now, if I attach either the router or ...
0
votes
1answer
509 views

Why the difference between the RSSI and Rx Level measurements is so big?

I'm new in Telecom. Today, I downloaded the Android APK called "Network Cell Info Lite". In my house, I got this measures: RSSI: -51 RXLEV: 60 I know this measurements represents the received ...
0
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0answers
46 views

Does radiation level of an antenna depend on the antenna's parameters?

I am a newbie when it comes to the theory of telecommunication. I wonder whether radiation exposure may exceed recommended safety levels after changing the antenna only? I'm asking since I've seen ...
2
votes
1answer
52 views

What is a Direct Radiating Collector Amplifier?

Reading the Space Systems/Loral press release SSL Achieves Milestone, 100 Satellites Delivered based on the 1300, a Platform for evolution, innovation I ran across the sentence(s): It was the ...
0
votes
1answer
55 views

Is there a network mapping tool for path-loss?

I am not sure if this is the proper forum. I am looking for a tool to evaluate the wireless network performance.For example, given a map where should I put a transmitter/or transmitter plus repeater ...
1
vote
2answers
660 views

Using Cat5 for DSL from NID - good idea to double up wires for signal integrity / strength?

I am doing some rewiring of our internal phone lines (almost entirely removal of unused lines). The issues we have run into is the router will every now and then simply not connect from the house to ...
20
votes
2answers
472 views

“56k modem” found in VHF band

While scanning the VHF spectrum with a SDR USB dongle, I found something that sounded like an old 56k modem (at around 160MHz, FM modulation, Europe region). After some research, I found out that is ...
0
votes
1answer
265 views

How to turn a PLC smart meter into 3G or Wifi [closed]

My utility has deployed bout 300,000 ZX E221 Three Phase Prepayment Smart Meters and they consist of a Meter control unit (MCU) which the consumer cannot access and a User Interface Unit (UIU), which ...
0
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0answers
41 views

What is the SAR(Specific Absorption Rate) value near a Telecom Tower?

We know the SAR values of every smartphone. However we've got so many cellular towers in our neighborhood. How much of risk is there, health-wise, in being exposed to them daily? I mean is there any ...
1
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1answer
81 views

Wireless Channel Modeling and Channel Estimation

If a channel model can describe the behavior of a wireless channel (in terms of frequency and distance), then what is the exact purpose of channel estimation? Why does one need to estimate the channel ...
0
votes
0answers
257 views

Negative Input DC-DC power supply

I have a requirement of DC DC power supply where the input voltage is -48VDC and output voltage : +5V and -5V with output current 4A and 3A. Is it correct to use a DC DC power supply of more than 35W ...