Questions tagged [communication-standard]

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2answers
54 views

OFDM Query : Why In Phase and Quadrature Phase RF Conversion is needed? [duplicate]

OFDM Basic Query- x[n] produced at output of IFFT is in discrete time, so we can use DAC and then RF Upconversion (multiply it with LO Frequency say f) and send it, why are we doing RF up conversion ...
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1answer
39 views

Did Dialup Modem use closed or open loop power/volume control? How did they determine Tx level?

I have been reading about dialup modems, but one thing I cannot seem to find out about is how implementers determined optimal transmit power/volume. Is this part of the echo cancelation framework? The ...
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0answers
27 views

NR PUSCH non-codebook based precoding

While reading 3gpp 38.211, Chapter 6.3.1.5 I noticed For non-codebook-based transmission, the precoding matrix equals the identity matrix. So, I guess, non-codebook-based precoding shall be ...
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1answer
67 views

5G uplink switching from CP OFDM to DFT-s-OFDM

5g NR standards can allow for both CP-OFDM and DFT-s-OFDM in the uplink. Suppose a UE is allocated resources. Can the UE switch from CP-OFDM to DFT-s-OFDM from one slot to the next ? Are these ...
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1answer
106 views

In wireless communications, is it true to say: The more the range, the more the delay spread?

The general idea which can be drawn by reviewing wireless channel models says that the longer the range/distance, the more the delay spread, even in LOS microwave links. But I really wonder why it is ...
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1answer
53 views

How to find the bandwidth of the transmitted M-FSK signal?

I'm tried to find the solution, but I failed. my question in the figure below, and the correct answer it's shown at the end of Figure. I'm using this formula but the answer is not correct! Is there ...
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1answer
23 views

Analysis Received Signal at receiver side

I'm trying to understand something which is really confusing me and I made my best to understand it but still confused. If I have transmitted and receiver. Assume I want to transmit S(t) data and ...
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0answers
12 views

How is CFi related to Code Rate and link Quality of the lte network?

Im trying to understand the relation between CFi and Code Rate and Quality of the network? like if I have bad quality then we need to decrease CFi? what about Code Rate we need to increase? About ...
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1answer
79 views

Viterbi decoder K=3 using ADD-COMPARE-SELECT Operation

I am in trouble with Viterbi decoder for a while. I have some questions. I need to decode messages from a continuous stream which is encoded. I'm reading from book : digital communications bernard ...
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1answer
105 views

Transition table / matrix for convolutional encoder K=3 understandings

Im trying to understand convolutional encoder $K=3$ , and I almost understand it but still confused about what's called transition matrix which in other words it means what input value ($0$ or $1$) ...
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1answer
31 views

Cross corelation understanding -Digital Signal Communications (searching for specific vector inside the other vector)

I have two vectors , one called v1 and the other v2 , the size of v1 is 10k , and the other v2's size is 32 , I want to search inside the vector v1 if there's v2 , this means when I find that the ...
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1answer
725 views

Combiner vs mixer vs coupler?

All these three terms are often used in communication texts and apparently they are some how similar But what is exact difference between each of them?
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1answer
253 views

Serial to Parallel Converter

in many texts about modulators I have seen there is a component called "Serial to Parallel Converter". For instance, let's consider this scheme and let's focus on the second block (reference): The ...
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1answer
73 views

WiFi Channelization for 40, 80 and 160 MHz

I have some questions on WiFi channelization in 802.11n and 802.11ac. Here is the snip of List of WiFi channels (source: WiKi): I am working on the L1 layer for 802.11n and 802.11ac model where I am ...
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1answer
123 views

Hilbert transform Use as a Single Sideband Frequency Translator in Analog communication

How Hilbert transform helps us in communication? What is the practical significance of it? Specifically how is the Hilbert Transform used to create single side-band frequency translators?
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1answer
157 views

What is the forward error correction in 802.11a?

I am trying to put together a baseband-equivalent simulation of 802.11a signals, which according to Wikipedia has a variable encoding (PSK, QAM, etc.) that have differing coding rates (1/2, 2/3, 3/4) ...
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1answer
124 views

Is the path loss exponent $\alpha$ is always 2 in friis equation model?

In the friis equation, the reference distance is 1m at the log distance path loss. Then the formula would be: $$P_r = P_tA_rA_t(\lambda/(4\pi))^2 /d^\alpha$$ where $d$ is distance between terminals,...
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0answers
20 views

Convolutional coding that payload length does not change

This is the question about Sigfox radio specification. The stack: Specifically, in Section 3.10 of the specification, we have a convolutional coding (after CRC) with three possible polynominals. I ...
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0answers
60 views

How can 802.11p ensure 1 Mbps in 1 km range?

Using the 802.11p standard, mobile vehicles can communicate each other. IEEE 802.11p standard typically uses channels of 10 MHz bandwidth in the 5.9 GHz band (5.850-5.925 GHz). And the transmission ...
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1answer
36 views

Radio Signal Stationarity

A radio signal recording of a wireless communication system (e.g: Wi-Fi traffic) is beaconized, channelized and subject to noise. When working with such an RF signal, numerically transformed to a ...
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2answers
76 views

What is Received power value when distance value is 0 in Friis equation [closed]

The Friis equation is as follow. $$P_r = P_tA_rA_t(\lambda/(4\pi d))^\alpha$$ where $d$ is distance between terminals, $P_r$ is received power, $P_t$ is transmission power, $A_r, A_t$ are the rx, tx ...
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0answers
183 views

No. of Cyclic prefix for 5G NR signal with 100Mhz bandwidth different subcarrier spacing?

I want to generate a 100Mhz bandwidth 5G NR signal with different subcarrier spacing(15,30,60,120Khz) in matlab. What is the no. of CP to be added for 1st OFDM symbol and the other symbols and also ...
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3answers
133 views

Quality of experience engineer

I have noticed certain overlap between digital signal processing and quality assurance for jobs that require expertise in evaluating the quality of the transmitted signals on telecommunication systems ...
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2answers
6k 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 (...
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1answer
560 views

File size adjustment using FFT

I have been given the task of doing audio compression using FFT. The assignment is below. Below is my MATLAB code: ...
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3answers
6k views

Capacity of cascade binary symmetric channels

Let's imagine that we have interconnected in cascade $L$ binary symmetric channels each with the same transition probability $p(y|x) \in \{p, q=1-p\}$, where the output of each BSC is connected to the ...
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2answers
83 views

Actual measurements of the influence of fading and multipath on HF radio communication

I'm looking for papers or books that contain actual measurements of the influence one has to expect in HF radio communication. I'm interested in this, because i've simulated the influence of a ...
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2answers
6k views

System Frame Number in LTE Specifications

What exactly is System Frame Number in LTE specifications? What is the use of it? I have read that it is a 10 bit number and used for synchronization purposes. But it's not clear how it helps for ...
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2answers
1k views

Difference between diversity gain and coding gain

I am reading about space-time codes. They break down further into 2 sub categories called space-time trellis codes and space-time block codes. It says that trellis codes offer both diversity and ...
2
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1answer
234 views

P2 symbol constellation in DVB-T2

DVB-T2, 32K SISO, not extended. I've acquired P2 symbol, PRBS bits have matched with bits recovered from pilots. Then equalization was applied to all subcarriers. The constellation I've got looks ...
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0answers
189 views

How often do a LTE eNodeB scheduler schedule?

Scheduler schedules the resource for each UE. How often do a LTE eNodeB scheduler schedule? Is the time between each scheduling fixed? any idea/reference will be great help on this regard. Thanks.
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1answer
730 views

Transport Block calculation in LTE Downlink

I would like to understand the relation between the TB size calculation in the TS36.213 document and in the simulator (https://www.nt.tuwien.ac.at/research/mobile-communications/vienna-lte-a-...
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3answers
2k views

How to determine the FFT size of LTE downlink receiver?

I'm puzzled about the LTE FFT size. Assuming an LTE base station works at 20M mode, the FFT size is 2048. Then, many users can be served by this base station. Do all these users work at 20M mode (...
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1answer
2k views

Why 1536 FFT size for 15 MHz in LTE

Why we use 1536 point FFT for 15 MHz bandwidth, when we can use 1024 point FFT, as in bandwidth of 15 MHz we have only 900 subcarriers.