Related to all communication systems that use a given digital sequence as an interface between the source and the channel input.

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2
votes
3answers
90 views

What happens if SINR is < 1?

What happens if the SINR of a signal is less than 1 in a (wireless) network? Is that practical at all to have a SINR < 1? Using the Shannon capacity formula, it seems that we must be able to have ...
0
votes
1answer
26 views

Is it possible to put one E0 voice signal directly into a STM1 frame

I've been going through STM1 frame structure recently. Is it possible to put a single E0(64kbps) voice channel directly into a stm1 frame or should it be put sequentially into a E1 and then to an E2 ...
1
vote
1answer
71 views

Could anyone explain the two-ray ground-reflection model in plain English

I am studying about wireless communications and I need to understand the two-ray ground-reflection model for one of my assignments. However, I fail to understand it. Could anyone provide a ...
4
votes
3answers
68 views

Laser emitter for serial communications?

I want to build a 2-way serial communications rig using low cost LED lasers. 9600 baud would be ok, but faster speeds would be more useful. (This is purely a hobby project. The further I can establish ...
1
vote
2answers
66 views

Fan in Fan out problem

Fan out is the maximum number of inputs that can be connected to a specific output. Why can’t we connect more number of inputs to this output?
1
vote
1answer
71 views

Signal drawing based on a constellation diagram

Constellation diagram of a communication system is given. S1(t) -> 0, S2(t) -> 1 Φ1 and Φ2 are basis functions and Tb is the bit period. How can I draw S1(t),S2(t) and decision boundaries?
-1
votes
0answers
33 views

If a jitter comes, how symbols of QAM is impacted

Thank you. skillful everyone. Owing to you, I have been able to studied little by little. Let me say thank you very much. Well, if a jitter or a wander comes, how are the each symbol of I-Q coordinate ...
1
vote
1answer
56 views

Quantization levels and SNR

Im' trying to build a big picture of telecommunication and i'm stuck in a topic, related to digital communication. But the problem is that i can't go too deep into the topic because it is imensely ...
0
votes
1answer
68 views

BFSK Modulation Output

I'm having trouble understanding outputs of a BFSK modulator. $$S_1(t) = cos(πt/T)$$ $$S_2(t) = cos(2πt/T)$$ If the input 0 or 1, how can I calculate the output? Edit: There is a formula to ...
2
votes
2answers
75 views

QAM's Demodulation

Let me confirm how the demodulation process of QAM is. $$s(t)=I(t)sin(2πft)+Q(t)cos(2πft)$$ Then we have to guess \$I(t)\$ and \$Q(t)\$ in order to know what the said bit formation of the ...
0
votes
1answer
57 views

SNR vs Signal Strength for digital throughput

I'm trying to compare two antennas, A and B for WiFi. A is showing: Signal Strength of -77dBm, but SNR of 9dB. B is showing: ...
2
votes
1answer
42 views

Wireless telecom system (cellular with Erlang and spectral efficiency)

We have a spectrum of 20MHz that we will use on a wireless cellular system, which requires 50kHz per channel. The system is using cluster size K = 4 and the radius of every cell is R = 1 km. a) ...
2
votes
2answers
91 views

Can I use this IR Transceiver for communication and obstacle avoidance?

I am building two robots. For communication and obstacle avoidance I am using Infrared. I bought this IR transceiver TFDU4101-TR3 (http://www.farnell.com/datasheets/1675739.pdf)which I thought I could ...
3
votes
1answer
74 views

What does “50 ohm system” mean?

I'm looking to use the following switch to switch an SPI bus ( CLK <= 2Mhz) between two different devices. I'm reading the datasheet to see if the the frequency of the signals are going to be ok, ...
0
votes
3answers
86 views

Long distance communication

I am looking for a cheap single wired solution to transfer data of some sensors connected to a uC over a distance of 1 KM from a control room on UART. The data is of 16 bytes, no high speed ...
0
votes
1answer
42 views

Definition of link gain for an optical system

Is the link gain the gain of the whole system or just over the diode? And why does the threshold current of a diode laser have no impact on link gain whereas increases in slope efficiency have a major ...
0
votes
1answer
71 views

Designing a simple energy-efficient communication protocol?

What is the required background knowledge in order to be able to understand and work on the design of a communication protocol which has to be robust, simple and capable of coping with short contact ...
1
vote
0answers
81 views

Why are there so many signal grounds for PCI Express?

PCIe connections have one to two ground contacts per differential signal pair. Why is this the case? On the boards that I have been studying, all of these pins are tied together onto the same ground ...
1
vote
0answers
35 views

Calculating the frequency of CPM signal in System Generator

I have a circuit which has been designed by System Generator to be implemented on FPGA. The circuit's output is a CPM (Continuous Phase Modulation) signal in which it is apparent that its ...
1
vote
1answer
113 views

why when calculating rise time we use 2.2 × tau? (RC Low Pass Circuit)

I am just trying to understand why we use 2.2×Tau when calculate the rise time. I can't find a derivation anywhere, I don't understand where this 2.2 came from.
1
vote
3answers
200 views

the causes of Fading of signals

I have read about fading of signals , and I have notice that the major cause of fading is multipath , but I have ask myself , what about attenuation , noise and free space loss , all of these make the ...
0
votes
4answers
97 views

Why don't you ever see a “anything” over (cable type)?

Possibly an obvious answer, and I'm new to electronics. You can easily find converters that convert a specific type of signal to another cable to be decompressed on the other end (example, a VGA over ...
1
vote
3answers
75 views

the implementaion of communication systems [closed]

I wonder , Why when we study communications systems , we just study the theoretical part(Math) , and we never touch the electrical circuits that used to implements this systems , I have asked my DR. ...
0
votes
1answer
65 views

Why Direct Broadcast satellite is interrupted by climatic conditions?

Television signals received through direct satellite service are mostly interrupted by the climatic conditions. But other communication systems that uses satellites are not that much affected. Why is ...
1
vote
1answer
113 views

What is wrong with this SPI implementation

I designed a system with RaspberryPi and STM32F407's, communicating with each other via SPI interfaces. For the last 3 months, tests were OK but yesterday a RaspberryPi and 2 of STM32F407's SPI ...
1
vote
1answer
56 views

What is digital Termination and when is it used?

I have heard transmission line termination but today I came across this "Digital termination" but couldn't find out why is it used and what effect does it have on digital signals?
0
votes
3answers
67 views

Bandwidth and wire parameters

Does the physical features of a wire like surface area, length or specific resistance form any sort of limit to the bandwidth of signals that can be passed through that wire?
0
votes
2answers
168 views

USB to USB data transfer using microcontroller [closed]

Is that possible that we can communicate two USBs,I mean data transfer between two USB without PC ? My friend told me that we can transfer data between two USBs using different controllers. How we ...
0
votes
0answers
51 views

16 QAM input data frequency?

I am simulating 16 QAM transmiter and reciver in MATLAB , using randint() function to generate input data stream. But I dont know what is the frequency of these input bits generated by randint() ...
2
votes
0answers
121 views

I need to calculate the average power spectral density after passing packets through a butterworth filter using MATLAB

I am trying to generate 100 packets(row vectors each of size 8192) of random bits(1,-1),filter them using butterworth filter and then plot their average power spectral density. I have to do this ...
2
votes
1answer
325 views

How to “Mirror” or “Split” bar code data scanned by one USB scanner to two computers using Y cable? [closed]

I have searched this site and many others looking for a way to "split" or mirror data from an USB device (bar code scanner) to two computers. We need to do a parallel cut-over from a legacy asset ...
0
votes
1answer
73 views

Digital vs Analog SNR

I am not sure why one of the advantages of Digital vs Analog communication is higher SNR? For example, when I want to transfer a 4.5v signal vs a 5v signal, how does converting these values to some ...
1
vote
2answers
86 views

Off-board SPI communication issue with ADC128S052

I seem to be having trouble with my board when it is not powered. I have a TI ADC128S02 (datasheet) acting as a slave and communicating with another master board via SPI. There are buffers on the ...
1
vote
2answers
93 views

RS485 + Power over twisted pairs, still need isolation?

I need to communicate with a piece of hardware on an elevator car. I have a few twisted copper pairs available, but it's not CAT5, so Ethernet is out. Instead I'd like to use RS485. I've been ...
1
vote
1answer
365 views

Keyes IR receiver with Arduino

I'm trying to learn how to connect an IR Receiver to an Arduino Uno. I got this IR receiver as a gift, and I'm having a hard time finding a spec. sheet anywhere online. The module looks like this: ...
6
votes
3answers
775 views

Difference between a bus and a wire

I have been studying buses used in communication systems. From what I read at Wikipedia, "In computer architecture, a bus (from the Latin omnibus, meaning "for all") is a communication system ...
1
vote
2answers
47 views

Receiving on an Induction loop

Earlier, I asked a question about an induction loop being used to transmit Wi-Fi, or internet to anybody who was in the loop. I then realized that the loop could not pick up the data for uploads, ...
0
votes
0answers
197 views

Using a TOSLINK/EIAJ optical module as both a transmitter and receiver for digital audio?

Size and aesthetics are design constraints for me, so I'm trying to think of ways to reduce visible IO on my device. But I don't want to sacrifice functionality for form. One of my ideas is the reuse ...
1
vote
1answer
124 views

RS-485 / CAN signal levels

From what I know, CAN at the physical layer in the "recessive" state just lets pull-up/pull-down do the work. Does that mean the rise time is theoretical slower than a RS-485 transceiver? And about ...
1
vote
2answers
33 views

Long Wires & Digital Chips

Is there a way to send digital signals over long wires(2-3 m)? Can I use buffers to do so? Is it efficient enough.
2
votes
2answers
140 views

Intercept SPI of RC helicopter controller

I've got this radio communication with an RC helicopter. I found that the RX on the heli is using an AVR MCU and a CYRF6989 2.4Ghz chip to communicate with the controller of the heli and translates it ...
0
votes
0answers
166 views

How to create a Modbus interface to Agilent DAQ?

I'm given the task to program a Modbus interface to Agilent 34972A DAQ. I'm completely new to Modbus and Agilent, but I've created a simple Delphi program that capture TTL digital outputs from ...
2
votes
2answers
102 views

Analog to digital converter

I have very little electrical knowledge. So here is my question. I need to test some wiring harnesses if they grouped like it should be. There is 70-80 points. differencing on the harness, these ...
2
votes
1answer
54 views

Multiplexing a phase shift keyed signal

There are a number of great tutorials online explaining phase shift keying as a means of digital wireless communication, but none of them seem to cover the topic of multiplexing. At first glance, it ...
3
votes
3answers
97 views

Are Wi-Fi 'transparent' buildings superior to antennas mounted on the exterior?

Looking in particular at wireless mesh networks in cities - is it advantageous to design a building that does not interfere with Wi-Fi (e.g. out of wood instead of steel and concrete), or would ...
1
vote
1answer
65 views

Voice and data through TDMA in VHF systems

In a VHF radio system using TDMA can a time slot be used to carry both voice and data bits together or is it necessary that both be transmitted in two different time slots. Also while reading an ...
2
votes
2answers
91 views

Need help with digital arithmetic

I am adding two hex numbers and determining what bits in the condition code register. The numbers I am adding are 4D (base 16) and ...
1
vote
0answers
97 views

PCIe card powered but not recognized on custom interface

I have a black magic declink mini recorder card that I am trying to recognize on a small form factor linux machine (debian 3.2.46-1 x86_64). I have made a custom interface board with what I think are ...
0
votes
4answers
105 views

One Channel Digital Communication

I want to setup two-way digital communication between 2 Arduinos, but I'm only allowed one wire between them. One may be "master". Are there any well known methods for synchronizing communications, ...
0
votes
3answers
179 views

Interleaving bytes

Can someone explain how exactly interleaving is done? Is there a way to do it? From what I understood, interleaving is transmitting only some bits of a byte for transmission, but did not exactly ...