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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7 views

SIM900 GSM module power LED on but can't get signal

When I connect my module to power the power LED stays on but I can't get signal LED blinking. I am connecting it to my PC via serial port and using Putty software. I am using a SIM900 Flyscale module. ...
1
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1answer
30 views

A circuit to prevent parasitic powering of FT232RL by MCU, will it work?

In a previous question I asked how to prevent the MCU TX pin (3.3V when idle) from powering an FT232RL Usb to Serial chip via the TX line: Preventing parasitic powering of FT232RL by ATMega328P I ...
17
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10answers
4k views

Is there any way to use half-bits?

As most people here know, by using 4 bits, we are able to count from 0 to 15 (0123456789ABCDEF in hexadecimal). But if we were to only count up to 9, we would still be using 4 bits, and the digits ...
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0answers
21 views

choice of parity bits for linear block codes

We know that in linear block codes the codeword for a given a message is generated by multiplying the message with the generator matrix G . The generator matrix consists of a sub-matrix which is the ...
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0answers
18 views

A closed form for calculating shaping gain

As we know, in a communication system, we can divide the overall gain into coding gain and shaping gain, but I have not seen any closed form formula for calculating shaping gain, but the definition ...
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0answers
83 views

Transferring data from FPGA to PC (new to FPGAs)

FPGA beginner here. I have a Basys2 FPGA board(i code in verilog) and i wish to make it communicate with my PC. Currently it receives data from a slave device and stores it in an 64 bit register. ...
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0answers
19 views

Error Correcting Codes - Communications

I'm doing a research on the the physical effect of unbalancing the fraction of 1's and 0's in digital communications. Can anyone quote a specific FEC code that adds for example up to 20% overhead to ...
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2answers
82 views

TTL Long Distance Transmission Alternatives

I am working on a system that gets data from a sensor via a TTL connection. Currently, the data that is gathered from the sensor is sent to another part of the system via a set of modems. The ...
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17 views

Variance of background thermal noise wireless communications?

I am new to this forum and hope I can get some help. I have been reading a paper on wireless communications, in this paper a base station with power P=25 is serving a certain user. The user is ...
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3answers
128 views

How to increase range of zigbee?

I have a Zigbee Pro with Arduino whose range is 2 miles as per specifications. But practically its maximum range is only 200 meters. I am using XCTU software. Is there any setting/configuration in ...
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1answer
111 views

Noise level, SNR and BER relationship in BPSK modulation

I would like to know what is the relationship between SNR, noise level and BER in BPSK modulation scheme? Can you please tell me the formula?
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1answer
78 views

What is the difference between 1-bit SDIO vs SPI?

What exactly is the between 1-bit SDIO vs SPI? Does one have advantages/disadvantages over the other?
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2answers
94 views

What is the minimum bandwidth required for a digital communication system using 32-QAM modulation?

If the bit rate of the digital communication system is 'R' Kbps & the modulation used is 32-QAM, what is the minimum bandwidth required for ISI free transmission? My understanding & analysis ...
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0answers
35 views

what is superposition coding?

In the context of multiple access techniques, there is a coding scheme called "Superposition Coding" or particularly "Superposition Coding with Successive Decoding(SCSD)". I surfed the internet, and ...
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1answer
48 views

Difference between spectral efficiency and bit rate

I am reading articles about error correcting codes, facing to a term "spectral efficiency". Due to the context, I guessed that it means "bit rate", but I wonder are these two terms equivalent or not? ...
2
votes
1answer
143 views

Why it has used BPSK modulation after OFDM?

I am quite new to OFDM modulation. I am reading this from a tutorial. In one of its parts, for showing amplitude variation of the OFDM signals, there is a graph that has used 8 sub-carriers and BPSK ...
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0answers
27 views

What sampling rates will give uncorrelated samples of x(t).considering the mean of the Random Variable 'x' to be zero?

What sampling rates will give uncorrelated samples of x(t) ? Considering the mean of the Random Variable 'x' to be zero. My Thinking: Since the mean of the random variable 'x'is zero,then it will ...
2
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1answer
53 views

How is CPM Modulation Different from PSK?

Continuous phase modulation has been described to me very similar to wikipedia's definition, which basically indicated that the CPM is different from QPSK, for example, because QPSK abruptly shifts ...
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1answer
32 views

How does SMBus receive byte command protocol know what to send?

Im programming an I2C device to act as a PMBus slave. Looking at the SMBus protocols (which PMBus is built on) the Receive Byte command has a format described as follows: ...
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2answers
44 views

parameter that limits data rate in communication

In communication, the maximum data rate that can be achieved is given by Shannon as C=B*log2(1+SNR) bits/sec. Supposing that I've a very high SNR and an infinite bandwidth, then can data be ...
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2answers
39 views

sampling rate, data rate and bandwidth

I'm new to digital communication. How are the terms data rate and sampling rate related to the term "bandwidth" . Am I missing something here?.Can someone explain me in detail? thanks in advance, ...
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1answer
47 views

Group delay when using a matched filter

Supposing I have a discrete time signal x(n). when I pass this through an FIR filter h(n), and again pass this result through h(n) again (essentially this is a second order filtering), the group delay ...
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2answers
60 views

Usage of complex filters in communication

In the last stage of a communication transmitter, at the front end a filter is used to eliminate unwanted signals from other frequencies. As far as I read in literature, are these filters "real" ...
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3answers
81 views

using C libraries inside verilog

I'm implementing a radio in Verilog. the time taken for bit reversal while computing the FFT is more. it is almost equal to a symbol time (OFDM system). Can I use a FFT library in C, which can be ...
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1answer
64 views

How do data and address strobes cause input to be latched?

Often in digital systems when multiple components communicate with each other they use strobe signals. Among these are data and address strobes. The strobe signal being asserted means that the data or ...
2
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2answers
97 views

Circuit to throw out 1st bit of every 17-bit sequence?

I have a system that currently uses two Maxim DS1867 digital potentiometers in a daisy-chain configuration. In a new addition to the system I would like to use a new digital potentiometer part like ...
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1answer
46 views

Prove a theorem about an upper bound for entropy of a random vector

There is a theorem that: if Z is any zero-mean, complex random vector with covariance \$E[ZZ^H]=R_z\$, then \$H(Z)\leq \log|{\pi eR_z}|\$, with equality holding if and only if Z has a circularly ...
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0answers
43 views

Form of the received signal in a MIMO communication

I am reading an article which is related to MIMO communication networks. Consider that there are \$U\$ users, each of them have \$J_{u}, u=1,...U\$, different layers. We want to calculate the received ...
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0answers
54 views

Difference between “user” and “layer”

I am new to multiple access communication theory. I read some articles on LDS, and I thought that "layers" is a term used for "users" (In another language I thought that for example when we say "we ...
4
votes
3answers
169 views

Why interfaces and buses gets faster with every version if they are physically the same?

An interface or computer expansion bus gets faster with every version eg. PCI express 1.0 is 4GB/sm, PCI express 2.0 is 8GB/s, PCI express 3.0 is 16GB/s. I understand that things like microprocessors ...
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2answers
54 views

Spreading vector

I am reading an article that is about CDMA. In that article I encountered a term "spreading vetor". I searched some books such as Proakis and Gallager to see what it means. I even surfed internet for ...
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3answers
145 views

What exactly does a 10-transistor XOR gate look like?

I need a schematic for a 10-transistor xor gate, I have searched everywhere and I see 8, 12, 6, but I can't see 10. What does it look like in a transistor like picture?
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67 views

Would my project be affected by lack of a filter?

I have chosen to do a final project, I will be transmitting bits using a wien bridge oscilator, I want a 160 MHZ sine wave and I have chosen values for it. I have chosen the AD8041 op amp because it ...
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1answer
45 views

RF Solutions ZULU module

I am trying to set up a remote battery voltage checker that will radio the voltage read from the battery to a computer. I went for the ZULU module (by mistake as I should have brought the ZULU-M ...
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0answers
120 views

Why is “throughput” called “bandwidth”?

But back in school, I had learned that the "bandwidth" of a communication channel is the frequency of the highest-frequency signal minus that of the lowest-frequency signal that it can carry. Yet in ...
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0answers
42 views

How to generate random fading variables using Nakagami-M distributions

I am trying to write my own mat-lab code to generate Nakagami random variables, As we know due to multi-path propagation we have random attenuation and delay. I have a signal coming out and I want ...
14
votes
2answers
165 views

HDMI and I\$^2\$C

I was having a look at the HDMI pinout and I thought: why would they use I\$^2\$C for the display-host communication? My question here is about the design metrics that lead to this choice. HDMI is a ...
2
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3answers
134 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 ...
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2answers
52 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 ...
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1answer
312 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
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3answers
88 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 ...
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2answers
133 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?
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1answer
130 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?
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1answer
106 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
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1answer
139 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
115 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
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2answers
134 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
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1answer
110 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
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2answers
131 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
99 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, ...