Science topic

# Wireless Communications - Science topic

This group has been created to bring together those interested in wireless communication research.
Questions related to Wireless Communications
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We know that in the Han-Kobayashi region, the to be transmitted data is divided into two parts, private and common. So, what type of information does these parts contain ?
Thank you Prof. Emil Björnson for the clarification.
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Hello everyone, I want the solution manual for this book if there anyone have the solutions kindly refer it to me , Best regards.
i am
professor
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In the textbook of Tse "Fundamental of wireless communications", the LOS MIMO channel model is characterized by $H = \alpha \times a(\theta) *a(\gamma)^H$ where a(\cdot)\$ is the steering vector. The model uses conjugate transpose while there are other papers use transpose. This has puzzled me a lot. I understand if the transmitt antennas and receive antennas are different, both of them seem to be right. But how about the full-duplex antennas, which one should be right?
There should be a transpose, not a conjugate transpose.
The same applies when considering uplink/downlink reciprocity: The uplink channel matrix is the transpose of the downlink channel matrix, not the conjugate transpose. The phase represents a propagation delay, and it is the same in both directions, not inverted.
Authors like to ignore this to obtain a more convenient presentation in textbooks and papers where the uplink and downlink are more mathematically symmetric (I've done that myself). But I think this isn't the right way to go if we want people to learn how to implement things in practice.
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Since the importance of Machine Learning (ML) is significantly increasing, let's share our opinions, publications, or future applications on Optical Wireless Communication.
Thank you!
Our paper is related to Localization in underwater Visible light communications using neural networks, I believe Localization using neural networks or deep learning is a hot topic in UVLC, There are many papers on the indoor environment, but more researchers are attracted to underwater communications as the optical domain is far better than RF inside the water for different types of water (Sea or Water or Turbid water). Introducing the blockage and dynamic motion is challenge in localization and transmission in UVLC.
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I'm looking for an advises regarding Machine Learning methods applied in Wireless books to solve some optimization problems.
You welcome
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According to my knowledge, the channel estimation is to analyze the channel realization based on the pilot signal, and the channel prediction is to obtain it based on past channel realizations.
Therefore, the channel prediction can be utilized when the pilot signal is contaminated. In other words, the channel prediction is only deserved in the situation when the pilot signals are crashed so that the channel estimation doesn’t work.
Did I understand right? Thank you for your valuable responses in advance.
I would describe it somewhat differently. In my vocabulary, channel estimation refers to the general concept of utilizing received signals to estimate the channel response. The estimation could be based on pilots, pilots+data or only data (the latter two are known as semi-blind and blind estimation).
Since the channel is changing over time, we need to estimate the channel repeatedly in a wireless system. Normally, we are only trying to estimate the current channel response, but one could also try to estimate future channel responses. This is what we call channel prediction. To succeed, you need an accurate model of the time variations. A Kalman filter is one method that can be used to predict future channels.
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In the context of wireless communication, I have heard people asking will the AI/ML model be trained online/offline? I would like to know what is the difference between these two terms and how they can impact the system performance?
Interaction with a tutor is a must within a full automated process handled by the digital revolution, the following research is an answer to your question where online interaction reinforces and accelerates learning:
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How to filter input signal through lognormal shadowing model or kappa mu shadowing model by using a code which generates PDF in Matlab?
you can use following code to pass through the log-normal shadowing model:
s= randn(1,20); %Randomly generated signal to pass through the channel.
M=4; order of modulation (I am considering that you are using 4-QAM modulation)
s_mod= qammod(s, M); % Modulate the signal
mean= 0; %Consider mean of Log-Normal model as 0
var=1; % Consider variance of Log-Normal model as 1
h_t= lognrnd(mean, var); % Generate Log-normal model
%Befor passing through channel, add cyclic-Prefix to the modulated signal
Ncp= 5; %cyclic prefix length
s_cp= [s_mod(end-Ncp+1:end) s_mod];
% Now pass throgh Log-Normal model
r1= conv(h_t,s_cp);
r= awgn(r1,10,'measured'); % Noise at SNR=5
%Now remove cyclic prefix,
y=r(Ncp+1:N+Ncp);
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Hey guys,
Please suggest the list of scopus list of journals for VLSI, Wireless networks and Wireless communications (Unpaid and paid)
Hello venkataraman,
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Hello everyone, I need some channel models MATLAB code to simulate my Underwater Visible Light Communication algorithm. If anybody has some models then please provide. thank you.
Hello sir,
please check our paper Statistical Studies Using Goodness-of-Fit
Techniques With Dynamic Underwater Visible
Light Communication Channel Modeling,
Hopefully, it will cover your needs.
Also, If you need anything related to codes, send me an email at afikky@ucsc.edu
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Most of the authors presented their work on Mach-Zehnder modulator in fiber optic communication. When I saw Mach-Zehnder Modulator on internet for buying it is showing it with fiber optic cable both sides of Mach-Zehnder Modulator(input and oupt side). My question is that can we use Mach-zehnder modulator for intensity modulation in wireless optical communication? Please help.
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What are the areas in fading channels like TWDP,Rayleigh fading Channel,Nakagami fading Channels?? ....Is pursuing research in this area are limited?Is there is a chance of publishing many papers in this area?
Wireless channels contain many propagation paths, with different amplitudes and phases. When a device moves around over distances proportional to the wavelength, the phases are changes rapidly and the paths might add constructively or destructively. If one models this statistically, you get a fading distribution.
Depending on the amplitude mix of the paths, different kinds of fading distribution appears. If all paths are equally strong, you will get Rayleigh fading. If one path is much stronger than the others, while the remaining ones are equally strong, you will get Rician fading.
If the fading doesn't match any of those categories, then the Nakagami distribution is a popular one that allows for fine-tuning a distribution to fit with measurements.
It can be of interest to evaluate the performance of communication systems in different fading scenarios, but one should avoid designing algorithms that are too reliant on a particular fading scenario because the distribution can change rapidly in practice. We talked about this in my podcast: https://ma-mimo.ellintech.se/2022/01/19/episode-25-what-models-are-useful/
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I am keen to do research in wireless communication. I would like to know research idea in this field.
You may develop a novel security protocol or privacy preserving protocol and demonstrate that it is efficient as well
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Both deep learning (DL) and quantum computing (QC) are emerging technologies in the realm of research. Please share your valuable opinion on the following concerns.
• How DL can be merged with QC?
• What are the current challenges in the DL-based QC?
• What are the tentative application areas for DL-based QC?
Dear Anik Islam Abhi.
Regards,
Shafagat
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hello, I'm looking for a simple model for a Reconfigurable Intelligent Surfaces-assisted wireless network that provides a vision for channel modeling for these systems.
no matter whether deep learning, machine learning, or convex optimization approach is applied to solving the problem and no matter that it is python or Matlab code
very thanks
DearAlireza Qazavi,
In order to get expertise in writing MATLAB codes for your Optimization problems, you first need to follow this manual:https://www.matlabexpo.com/content/dam/mathworks/mathworks-dot-com/images/events/matlabexpo/us/2018/master-class-solving-optimization-problems-with-matlab.pdf
Moreover, by googeling your queries you may find bundle of techniques and examples. Practice it, and get its expert.
Good Luck
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For Intensity modulation, I am using external modulation. I want to simulate mach-zehnder modulator based intensity modulation. Please suggest simulation in MATLAB
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I have an antenna module which is a planar phased array for 5G NR FR2 base station (i.e., BS type 2-O). I need to perform over-the-air (OTA) radiated conformance testing to verify the performance of antenna module to obey specification of 3GPP. Hence, I study the attached file 3GPP TS 38.141-2 V16.10.0.
For transmitter test (chapter 6), the module is connected with a signal generator (SG), which make NR signals generated by SG are emitted through antenna module. And then, a feed antenna is regarded as receiving end and connected with a signal analyzer (SA) and spectrum for analysing received signal. On the other hand, for receiver test (chapter 7), exchange the placements by module and probe antenna to perform conformance testing. The complete transmission and received process run in a CATR or anechoic chamber.
• How to set parameters (ex. total output power, modulation, operation band, bandwidth, frame structure, single or multi-carrier, subcarrier spacing, TDD or FDD, and so on) of measuring equipment (SG and SA) for radiated conformance testing according to TS 38.141-2? Would you mind take an simple demonstration for test items in section 6.2 and 7.3?
In my opinion, the section 4.7.2, 4.9.2 and Annex A is strongly relate to the setup. (I am confused about difference between intention of test configurations and test model respectively in section 4.7.2 and 4.9.2. I googled other materials (others attached file) about this issue, there is only description about Test Model NR-FR2-TM in test procedure rather than Test Configurations NRTC )
I have some base of communication system but I am short of practical experience of RF measurement, so this problem maybe is not an easy question to answer. If you cannot answer by a few words, please provide clues or direction of search.
Ryan Kao Based on your attachments I assume you are procuring R&S instruments. If you look at section 2.4 in both the attachments, it lists the devices and options required to conduct the tests. [This is just one example from the documents.] Typically, such capablities are licensed software options that must be purchased with the instrument (or even a later purchase of license can enable the feature!).
It will be best to go through the instrument documents, which are quite tedious to navigate through; you may save some time by reaching out to the vendor application engineer (AE) who might be interacting with your department/ institute. Understanding the test environment system is key to correct test execution and measurement.
If you need some insight into RF measurements in general, you may want to check out my book "RF & μWave Measurements: For Design, Verification and Quality Control", which is available at select amazon marketplaces. However, it does not address your 3GPP specific question.
/rgds
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In your opinion, what are the interesting and worthy topics for research in wireless communication systems?
Thesis topics Wireless Systems 2019-2020
5G telecommunications: on-body massive MIMO virtual array design.
A visible light positioning network planner.
Accurate indoor human positioning system by combining Visible Light and Radio Frequency signals.
Agricultural IoT data collection for wide crop fields.
Regards,
Shafagat
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Could any one please help me in suggesting some resources where I could find a comparison curve between signal strength after Multi Path propagation effect with respect to obstacle positions between transmitter and receiver.
After conduction some experiment I found that the effect was greater near Rx or Near Tx but lesser when the obstacle is in same distance from Rx and Tx. Why such phenomena happens?
I suppose this depends on what kind of obstacles you are considering and how they are affecting the signals. If you consider an object that is scattering the signal, then the pathloss will be proportional to (d_1*d_2)^2 where d_1 is the distance from the transmitter to the obstacle and d_2 is the distance from the obstacle to receiver. For a given total propagation distance d_1+d_2, it follows that the pathloss is at its smallest when the scattering object is close to the transmitter or the receiver.
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Hello
I am going through some digital communication literature, where some research papers have used the following formula to calculate the sum rate
Sum_rate=Summation (log2(1+SINR(i)) eq.1
My confusion is as follows:
1. Why is bandwidth(B) not included i.e. B.log2(1+SINR)
2. What will be the units (e.g. bps/Kbps/Mbps etc) if eq.1 is used.
Thanks
That sum rate expression is measured in bit/s/Hz. If you multiply with the bandwidth, you get it in bit/s.
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Hello, i am searching for some new innovation points in 6G about networking slice recently.
I want to know what updates will be made to network slicing in 6G, which cannot do well in 5G.
(Maybe about architectures, methodologies, algorithms, and combination with other 6G new technologies.)
Can you recommend me some good ideas, innovation points or papers( and white papers), thank you.
Dear Zhenkang Zheng,
the future virtual 6G networks in the form of 6G slices will definitely be set up as "Software-Defined and Open Programmable 6G Slices". The idea of SRv6 Network Programming as the basic principles for the programmability of 6G slices is specified in the Internet Standard RFC 8986.
I have attached a short list of sources of information.
Best regards and good luck
European Vision for the 6G Network Ecosystem; DOI: 10.5281/zenodo.5007671
Petar D. Bojović, Teodor Malbasic, Goran Martić, Zivko Bojovic: „Toward 6G networks: Dynamic management for multi-slice QoS“
Wen Wu, Conghao Zhou, Mushu Li, Huaqing Wu, Haibo Zhou, Ning Zhang, Xuemin (Sherman) Shen, Weihua Zhuang: AI-Native Network Slicing for 6G Networks
Amin Shahraki, Mahmoud Abbasi, Md. Jalil Piran, Amir Taherkordi: „A Comprehensive Survey on 6G Networks: Applications, Core Services, Enabling Technologies, and Future Challenges“
European Vision for the 6G Network Ecosystem
Jie Dong: SRv6 based Network Slicing
Gaps, features and enablers for 5G/6G service management and orchestration
RFC 8986: Segment Routing over IPv6 (SRv6) Network Programming
SRv6 – IPv6 Segment Routing Figure 009239: Basic idea of SRv6 Network Programming
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Recently, I focus on UAV-enabled air-to-air wireless communications, in which the UAVs are flying at an altitude of 60~150 m. In this case, which channel model is more applicable? Intuitively, I think the LoS channel is suitable since there should be no obstacles at this high altitude. Is my idea correct? Could you provide me with some references, thank you very much for your help!
Dear Jiahui Li ,
If there is no obstacles in the path between the transmitter and the receiver and the medium is air then then the channel is for sure a line of sight.
If there is reflection from the ground to the receiver then there will be multi path effect. In this case one would model the channel by Rician model.
Both model are treated intensively in the literature. I think by skilled antenna directing to the UAV one can reduce the reception of the reflected radiation from the ground.
Best wishes
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Please guide me about the difference between SINR threshold and Minimum discernable signal.
From my search I have come across the following.
1) A signal can be decoded if the SINR of the received signal is higher than the SINR threshold. Does it mean that we should not be concerned about the minimum required power, and that if the received signal satisfies the SINR threshold, it will be successfully decoded?
2) I also have come across the idea of minimum discernable level. For instance -70 db is considered acceptable for some types of communication.
Which of the two I should follow. As in the first case, I get very low transmit powers and still satisfy the SINR threshold, while the transmit powers in the 2nd case are way too high compared to the first case.
Dear Gul Lakhta ,
There is something basic which you you would like to consider. From the point view of the signals, the interference signal acts in a similar way to noise. When it is added to the symbol signal it will cause that it may be falsely detected if its value is increases such that the combined signal will be located in the neighboring decision regions of the adjacent symbols in the constellation diagram. So the interference and noise have the same effect in the symbol error.
Therefore one speaks not only from S/N ratio but also from the S/(N+I).
The noise has Gaussian amplitude distribution while the interference may not have such distribution because of the nature of the interference.
The interference signal sources are normally known and then they can be subtracted from the composite signal. If after interference cancellation there will be residual interference it will be treated as a noise concerning its effect on the symbol error. In the sense that it will set the S/I +N minimum level to achieve specific bit error rate. You see if N=0 then S/I will set this minimum.
Hope I could answer satisfactorily you question.
Best wishes
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Recently, I have seen in many papers reviewers are asking to provide computation complexities for the proposed algorithms. I was wondering what would be the formal way to do that, especially for the short papers where pages are limited. Please share your expertise regarding the computational complexities of algorithms in short papers.
You have to explain time and space complexity of your algorithm
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I need to write code in MATLAB to find the impulse response of infrared optical wireless communication (IROWC) in the diffuse distribution (wide beam transmitter and wide FOV receiver) ...
Aparna Sathya Murthy , thank you very much for your help ....
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Game theory is a very promising technique to achieve optimal outcomes and can be applied to almost all concepts. I am trying to explore game theory for future purposes. However, as a beginner, I couldn't get very good resources regarding game theory.
Please share your resources (i.e., video or blog tutorial, research paper) regarding game theory, which covers the following things.
1. How to apply game theory?
2. How to prove optimal gain after applying game theory, (e.g., proving Nash equilibrium).
3. What are the state-of-the-art game theory techniques?
Anik Islam Abhi For example forecasting and game theory are both effective tools to support finance-related decision-making and reduce the impact of risk factors.
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While reading the literature regarding performance analysis of RIS-Assisted Wireless communication Systems I went through the following terms: Achievable Rate, Sum Rate, Ergodic capacity. How do understand them?
The ergodic capacity is the theoretically maximum data rate (bit/s) that one communicate at over a fading channel, where the fading processing is an ergodic process. More precisely, this is the largest rate for which the probability of decoding errors goes to zero as the length of the transmission goes to infinity.
An achievable rate is any data rate below the capacity. It is normally associated with a particular (suboptimal but practical) way of transmitting.
The sum rate is the summation of the achievable rates of multiple concurrent transmissions, for example, different users that are multiplexed.
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I want to calculate transmit power that can satisfy a given SINR threshold on the receiver side.
My formulation is as follows:
If SINR Threshold (SINR_th) is known, we can get the Required_Received_Power and thus the "Required_Transmit_Power" power as follows:
We know that
OR
Substituing "Required_Received_Power" in Eq.2 with the right hand side of Eq.4, we get
SINR_th=(Required_Transmit_Power/Pathloss)/(Interference+Noise) Eq. 5
OR
Required_Transmit_Power=SINR_th x (Interference+Noise) x Pathloss Eq. 6
Please advise whether this formulation is correct or not as I am getting wrong results.
Thank you!!!
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In OFDM, First we modulate our message signal and then we take the IFFT of that signal to load the message on subcarrirers. And after that the cyclic prefix is added to combat the frequency selective nature of channel. What should be the length of the cyclic prefix?
The length of the cyclic prefix should be at least equal to the number of channel taps minus one, so that the linear channel filtering appears as if it is a cyclic convolution.
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you can use ns3, have look at the documentation.
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I am curious about what happened to the atomizer software by Buckheit J. (http://statweb.stanford.edu/~wavelab/personnel/) and if it is available somewhere.
Sadly I found only 2 dodgy sites that require a login to download the MATLAB code. Does someone have any information on where to get it from?
Alternatively, if there are other toolkits that have implemented this code please let me know, it does not have to be MATLAB, any language is fine for me :).
Thank you.
Old news but I found it here (http://sparselab.stanford.edu/atomizer/) if anyone finds this post while searching for it.
I've also downloaded the ZIP for posterity. Anyone feel free to get in touch if you need it. I plan on keeping it forever.
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Hi everyone, hope you are perfect!
today I am going to have a plea of you to lend me a hand if is possible.
as an wireless communication researcher, I come across many phrases that I have no idea about them. one of them is "optical front-hauls" and another one is "grant-free Transmission"!!!
If you can give me an imagination or illustration, what would it be?
Thanks for making time in advance.
#communication #5gtechnology #6G #wirelesscommunications
Adding to the colleague U. Dreher , you can see the definition of the optical front-hauls in the paper at the link: https://www.3coptics.com/News/9.html
The optical from haul is the optical fiber link between the base band unit and the remote radio unit. It transmits the base band signal to the the radio unit.
grant-free Transmission" is the transmission in which the quality of service is not granted. This is the bit rate and the bit error rate.
Best wishes
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How can I calculate the bit error rate of orbital angular momentum for wireless communication? I found this paper 'Error probability on the detection of orbital angular momentum detection' but in this paper, they are calculating the probability of the detection of the OAM mode like if the information were carried by the mode. While I am interested in the case where OAM modes are used to create orthogonal channels.
Perhaps you can use generic tables to calculate that.
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How do we represent zero interference on db scale?
I am using the following formula for calculating the Received_Power_TH (TH stands for threshold). Received_Power_TH is the power of the received signal required for successful decoding. I am using the following formulation.
SINR=Received_Power - Interference - Noise Or
The Recieved_Power that satisfies the SINR_TH (or in other words the minimum Received_Power required for successful decoding) is given as follows
SINR_TH=Received_Power_TH - Interference - Noise Or
Received_Power_TH =SINR_TH + Interference + Noise
However, i get the following results which seem counter intuitive.
Assuming SINR=25, Interference=-50, Noise= -95
Now if we do not have any interference e.g. in a case when there is only one node transmitting, we get the following
This result seems counter intuitive as Received_Power_TH for successful reception in case of no interference should drop below the value we get when we have interference whereas in this case the Received_Power_TH is equal to -120 in case of interference and it increases to -70 when there is no interference.
Many thanks
Zero is equal to -infinity in dB scale, since log10(0) = -infinity.
An issue with your computations is that the interference and noise power should be added together in linear scale when computing the SINR, not dB scale. So if the interference is -50 dBm and the noise is -95 dBm, the interference+noise is 10^(-5)+10^(-9.5) mW, which you can then convert to dBm as 10*log10( 10^(-5)+10^(-9.5) ).
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While going through the Literature I found that the performance analysis of wireless communication System was done by us one of the following three methods:
1. Moment Generating Function-Based performance Analysis
2. PDF Based performance Analysis
3. Characteristic Function-Based performance Analysis
Agree with Dr. Omid M Kandelusy
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I want to know about ML algorithms that are used to train the data set: e.g. in routing protocols in WSN.
Thanks for the question. The answers also interest me
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What can be tentative research areas in which deep learning can be merged with blockchain?
Blockchain technology can be used to safely distribute the structure and weights of trained neural networks based on tensor matrix theory in the process of mass replication in the production of Edge AI computing units. Blockchain technology can be used to coherently update multiple identical Neural Networks for adaptation to new situations or increase accuracy etc.
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Apart from experiments available for WiFi, IoT, LTE etc., we also want our students to work on experiments on 5G. Does someone have a set of pre-built NetSim experiments which we can quickly adopt for our course? If not, any suggestions on what kind of experiments can be done would be valuable? Thank you.
NetSim support a range of technologies, including the capability to interface Matlab and C++ programs. So if you want to integrate 5G in a Netsim experiment, you will need to deploy the 5G experiment in Matlab then interface it with NetSim for full deployment. I hope this answers your question.
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Is it possible to employ Beamforming for interference mitigation when two smart phones are communicating directly without any relay (such as Access Point, Base Station or some other kind of relay nodes) in between. We assume that many pairs of smart phone pairs are communicating directly and may interfere with each other. Therefore beamforming (if possible) will help reduce interference.
Yes, some smart phones have MIMO capability and so they can be used to realize your proposal.
Best wishes
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I need to know about the appropriate tools for modeling, simulation, and analysis of wireless communication systems other than MATLab.
Castallia, Contiki OS, OMNET ++, TinyOs are few are the options to simulate WSN. NS3 can be used but it is not designed for WSN as such.
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IRS can create higher beamforming gain with the help of an “intelligent” reflector. But, this brings other practical issues.
How does BS/AP synchronize with the reflector about the amplitude and phase?
where IRS is the intelligent reflective surfaces, BS is the base station and AP is the access point.
The basic algorithms for phase configuration and channel estimation are described in our tutorial article: https://arxiv.org/pdf/2102.00742.pdf
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In wireless communication channel modeling, capacity is calculated based on computed H matrix and SNR value.
H matrix is calculated through a different models - COST..WINNER..etc.
I am wondering how to calculate SNR at different locations of UE In a cell?
many papers assume a certain SNR before capacity calculation.
How one can calculate SNR in an urban macro environment in presence of scatterers with different BS-UE positions in distance and angle?
I am looking for SNR calculation throughout a cell for MIMO wireless channel using directive antennas.
The colleagues above gave satisfactory answer. The ultimate answer of your question is to make survey test at all intended points where one one can measure directly the recieved signal strength. This means one has to determine the spatial distribution of the received signal at the coverage area.
May be the best way is to determine such distribution empirically.
But this may be very tedious.
The other solution is to use use models of large scale fading and small scale fading to obtain statistical channel models.
The last possible solution is to make an electromagnetic solution for the signals emitted from the antennas in the real propagation space with districted scatters.
Best wishes
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In 5G, the mixed-numerology is introduced to support diverse QoS requirements. It is also mentioned in the spec that simultaneous transmission and reception with different numerologies in CA is possible.
However, there is few materials mentions how this is achieved. Does a UE requires multiple antennas to transmit with resources of different numerology at the same time? Or it can be done by a single antenna? If the latter is the truth, how does a UE deal with different SINR values generated by resources with different numerologies? (different SINR values lead to different modulation scheme, how can this be done with single antenna?)
p.s.
I have found one paper that is related to my question:
It seems that a UE can deal with resources with different numerology simultaneously, with different modulation scheme. Yet, this paper does not show how this is achieved by the smartphone.
It would be nice from you that you define the relation between the communication symbols and numerology??
This is the first time that I hear from such vocabulary in electrical communication systems.
What I know is the different symbols resulting after modulating the binary data.
There are binary symbol where every symbol contains either binary 0 or 1.
There is the the 2-bit symbol representing values from 00,10,01 and 11.
There is 3-bit symbol which has 8 states.
and so on.
This method of M-ary symbols help control the number of bit hertz.
And one can send more data in the same bandwidth by using higher order modulation.
It is known that every channel condition or S/N ratio can allow specific symbols.
If it mean symbols then yes one can control the order of modulation of the symbol.
Best wishes
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I'm looking for the best tool for UAVs' path planning; also the tool should support wireless communication.
Matlab UAV toolbox should be a very powerful tool.
Guidance models and navigation, trajectory and waypoint following:
UAV flight path using translations and rotations
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How fast does the traffic load of WiFi network change? What is the average time that the WiFi traffic load remains constant for different traffic types e.g. internet browsing, video streaming, voice call, e.t.c ?
Your question is not highly dependent and specific on wifi. It seems more important to think in terms of network traffic.
If the WiFi hub considered serves a home, you need to build scenarios:
-family members: children, parents, flat sharing people
-working hours: if working from home, how many videoconferencing sessions ,average duration, data upload and download between home location and organisation VPN
-outside of working hours: sessions of gaming, movies ("Netflix" or equivalent, movie of 120 minutes or more etc), music streaming. Browsing, YouTube, etc...
You may run a number of differently populated scenarios to explore and understand...
This may show you the limit of WiFi and take you into fine access...
As to how to picture for yourself what happens in homes during the current era of Covid19, you may benefit from browsing this study/model:
How does it work for you?
Let me know
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I am trying to obtain closed-form expressions of outage probability for a user in a given cell. Here I am including inter-cell interference (from other adjacent cells) in the expression of SINR. Now I need to obtain the closed-form expressions of outage probability over a fading channel like Nakagami or Rayleigh. Please suggest any information regarding this. thanking you
It is generally hard find closed-form expressions. It always the same math involved:
Say that the SINR is S/(I+sigma^2), where S and I are random due to fading. Then the outage probability when communicating at the rate x is:
Pr{ log2(1+S/(I+sigma^2)) < x } = Pr{ S/(I+sigma^2) < 2^x - 1 }.
If you know the distribution of S/(I+sigma^2), then you can compute this directly.
If you only know the PDFs of S and I individually, then you need to rewrite it as
Pr{ S/(I+sigma^2) < 2^x - 1 } = Pr{ S - I (2^x - 1) < sigma^2 (2^x - 1) }.
Now "sigma^2 (2^x - 1)" is a constant, but you need to compute the PDF of "S - I (2^x - 1)", which can be done via integration. The joint PDF of the sum of random variables is obtained by convolution.
At the end of the day, the chance that you get a nice PDF of "S - I (2^x - 1)" so that you then compute the probability is closed form by integration over the PDF from 0 to sigma^2 (2^x - 1) is not so big.
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I want to know how can we implement nakagami fading in MATLAB and get the small scale fading coefficients for this nakagami distribution in MIMO-OFDM channel. Any MATLAB code would be helpful. Are these coefficients time varying and how to get these coefficients for a certain time interval?
try this code:
"function H=nak_m(m,Nr,Nt)
n=zeros(Nr,Nt);
for i=1:2*m
n=n+randn(Nr,Nt).^2;
end
n=n/(2*m);
phi=2*pi*rand(Nr,Nt);
H=(n^0.5).*cos(phi)+j*(n^0.5).*sin(phi);"
I hope it helps
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I am try to build a system model where intelligent reflecting surface is used to enhance the receiver's SNR depending on the position of the receiver.
Based on what I read, a signal is scattered at the atom level and constructive/ destructive superposition is used to direct the signal to a certain user. My question is: Can the signal be directed to a user behind the IRS?
Sure, if two users are located in the same angular direction but at different distances, the reflected beam can be partially directed to both of them. You can find an example of this on Figure 10 of https://arxiv.org/pdf/2002.04960.pdf
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Dear all,
We all know about the fast and rapid developments in machine learning algorithms. But the question is that if we want to implement them for low latency (less than 1 ms) applications using wireless communications, is it possible?
I think it will depend on the complexity of the algorithm and the performance of the hardware in terms of CPU.
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I am able to generate Rayleigh coefficients as per the following code (function) in python using H=(1/sqrt(2))*(randn(N)+randn(N)*1i)
def RAYLEIGH(d, etaa, num_symbols):
// Input arguments (Distance, pathloss exponent and samples required (depends on data if fast fading)//
c=1/(d**etaa);
h1 = np.sqrt(c); //(Pathloss is multiplied with Rayleigh coefficient)
h = h1*((np.random.randn(num_symbols)+1j*np.random.randn(num_symbols))/np.sqrt(2));
g = (np.absolute(h))**2; // Magnitude
return h.tolist(), g.tolist(); // Return as a list
How to generate the Rician Coefficients given d (distance), etaa (path loss exponent) on the same lines.
You can create the channel directly with Matlab using the "comm.RicianChannel" then apply this filter to your signal
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In addition to the path made by 5G (small cell coverage, massive mimo, mm-waves, etc ), 6G is going to merge other areas such as bio-medical, artificial intelligence, robotics, etc.
What are the key enabling technologies of the 6G networks?
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How can I estimate the propagation loss between an unmanned aerial vehicle (UAV) or drone, and user equipment (UE) on the ground? is it safe to assume a line-of-sight scenario? how about the drone's altitude? is there a specific air-to-ground formula I can use?
There exist several pathless model, depending on the propagation environment. But you can use conventional model such as free space or Rice.
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what is the mean doppler shift for fixed wireless transmitter and receiver?
is it 0 or not?
V = 0m/s
Therefore, Doppler shift = 0
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What are the limitations of non-orthogonal multiple access?
Which difficulties may occur during its practical implementation?
What is the possibility of its consideration beyond 5G?
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In the attached figure A and B are transmitting to some destination X and Y (not shown in the figure) using transmit power TxA and TxB respectively. Where node C wants to transmit to node D.
Assuming that the distance between all the nodes is known, I want to find the following.
1. The total received power at node D due to the transmissions from node A and node B
combined i.e. total interference.
2. We assume that SINR threshold for successful decoding is Th. What should be the transmit
power of C i.e. TxC , so that its signal can be successfully decoded at node D in the presence
of interference from node A and B
3. How to calculate SINR and BER at node D for the signal transmitted by node C.
Thanks
Assuming that the transmission coefficients of the channels from the A and B to node C are ha and hb and assume that the transmit signal of A is Sa and that of B is Sb then the received signal at node C rC= ha Sa + hb SB
This power can be considered an interference which is added to the white noise to determine the threshold of the useful received signal.
So the total noise at the node C= rC^2 +N
The required signal to noise ratio is then given by
C= B log2 (1 + S/( rC^2 +N))
where S is the useful recieved signal power at node C received from the intended node. Bis the bandwidth and C is the maximum bit rate.
Best wishes
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Two very recent papers that illustrate the potential of OWC to support Tb/s communications:
1) A Tb/s Indoor Optical Wireless Access System Using VCSEL Arrays
2) A Tb/s Indoor Optical Wireless Backhaul System Using VCSEL Arrays
similar to Laser Power Converters (LPCs) for Solar cells, are there any LED Power Converters available ?
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Hi,
I have been through some discussion regarding survey paper writing tips and tricks. However, these are very generic. I want to know how to write a survey paper related to computer science topics (e.g., blockchain,.internet of things, so on). I have some following queries regarding the aforementioned concerns.
• How to design the flow of the survey paper?
• What will be the minimum length of the survey paper?
• How to pick up a reference paper and which criteria should be the first concern while selecting it? What is the minimum number of references that should I pick?
• Is it necessary to propose an idea in the paper? If yes then is it necessary to show a performance evaluation of the proposed scheme?
• While writing a survey paper which things should I focus on or care about?
Thanks for your time and input.
Importance and significance of the topic.
Discuss the background and target audience.
Summarize the surveyed research area and explain why the surveyed area has been studied.
Summarize the classification scheme you used to do the survey.
Summarize the surveyed techniques with the above classification scheme.
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Normally for fair comparison we assume equal transmission power and equal rate. If rate can not be made equal how can be compare two different rate channel codes?
Satheesh Monikandan Balakrishnan , For two different systems I think it is when log2(M_a)*R_a = log2(M_b)*R_b, where M is the modulation order and R is the code rate. Than you will have for both curves an equal horizontal shift between SNR and Eb/N0 of 10log10(log2(M)*R).
In case your question is about when the SNR and Eb/N0 curves will be equal then it is when log2(M)*R = 1.
I hope it help.
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what is SNR and how is rain drop size model value related to AWGN channel in wireless communication
Dear@ Oludele,
welcome,
The colleagues gave satisfactory answer to your question but I want to explain some fundamental points:
- The noise is generated in the receiver and it is modeled by an input noise power at the input of the receiver.
- There is the free path attenuation which depends on the frequency of the signal and the path length.
- There is extra path attenuation due to rain and fog.
- This attenuation is measured and given in characteristic curves that can be be found in the link budget calculations in the books of microwave and satellite communications.
Best wishes
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Millimetere wave (mmWave) channel model is widely known in the literature [1, eq. (7)], [2, eq. (1)]. [3, (55)].
What is the difference between mmWave vs. Terahertz Channel Models? In other words, is there any paper providing the channel model for Terahertz bands (including path loss, path gains, AoD/AoA, etc.)?
[1] A. Koc and T. Le-Ngoc, "Hybrid Millimeter-Wave Massive MIMO Systems with Low CSI Overhead and Few-Bit DACs/ADCs", Accepted in IEEE 92nd Vehicular Technology Conference: VTC2020-Fall , Victoria, BC, Canada, October 2020.
[2] L. Yan, C. Han and J. Yuan, "A Dynamic Array-of-Subarrays Architecture and Hybrid Precoding Algorithms for Terahertz Wireless Communications," in IEEE Journal on Selected Areas in Communications, vol. 38, no. 9, pp. 2041-2056, Sept. 2020
[3] A. Morsali, A. Haghighat and B. Champagne, "Generalized Framework for Hybrid Analog/Digital Signal Processing in Massive and Ultra-Massive-MIMO Systems," in IEEE Access, vol. 8, pp. 100262-100279, 2020
Good question
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what is the scope of applying ML and DL in wireless communication? How it is efficient in terms of performance, the complexity of computation, the power efficiency of the networks than the existing techniques?
Machine learning and deep learning will be used in wireless communication to enhance the state of the art classification, prediction and detection techniques.
I saw some applications on the channel estimation and equalization in OFDM wireless communication systems.
It was found that they have detection accuracy comparable to maximum mean square errors MMSE. This work is sent to publications when it is published i will report on its publication citation!
May be the main problem is the computational loads.
Best wishes
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Considering the multiple unique properties of the non-orthogonal multiple access (NOMA) scheme such as high spectral efﬁciency, low latency, improved coverage, massive connectivity, fairness, etc. What do you think will be the impact of NOMA on Future Communication Technologies? Will it be accepted in the next upcoming release of 3GPP?
Also read our latest work on the design of a novel NOMA scheme which can provide enhanced security in Future Communication Systems : https://assets.pubpub.org/o4wsnl6c/61606955002758.pdf
3GPP is already supporting MU-MIMO, which is a more spectrally efficient non-orthogonal access scheme since it actually adds additional degrees-of-freedom to the transmission. Hence, I doubt that NOMA will be utilized by 3GPP to increase spectral efficiency. The 3GPP document "Study on Non-Orthogonal Multiple Access (NOMA) for NR" shows that the performance gains of NOMA are small or nonexisting under practical conditions.
I think that 3GPP is still considering to support NOMA for some short-block-length cases where one can benefit by not having to schedule users individually.
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Hi, How can we calculate the entropy of  chaotic signals? Is there a simple method or formula for doing this?
you can use :
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Hello everyone,
I want to make a Microstrip Patch Antenna for Multiband operation of the shape that can be seen in the image attached. Can anyone suggest the perimeters/specifications and material that can be for Ground, Substrate, Patch, and Feeding so that the antenna can be used for multiband operation.
I am using CST Microwave Studio for simulating the design.
Other suggestions are also happily welcomed.
For the implementing the patches you can use the standard materials thought for them. If you work at relatively low frequencies, then you can use the FR4 PCB material. If you work at higher frequencies you can use Roger substrates. At much higher frequencies you can use Teflon substrates.
To design multi band frequencies please refer to the paper in the link:
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Intelligent Refelecting Surface (or Intelligent Reconfigurable Surface), IRS, consists of a large number of passive elements that are able to reflect the incident signal passively. The size of each element may depend on the wavelength of the signal to be reflected. My question here is how much should be the size of the IRS element in order to successufly reflect a signal with a wavelength \lambda.
The typical size of the elements being used in experiments is lambda/10 to lambda/5. The reason is that you want each element to scatter the signals without a directivity, so that the combined effect of having many elements will determine the directivity of the "reflected" signal.
I also explain this at 26:00 in the following video:
You can also listen to the Episode 3 in my podcast "Wireless Future", we we discuss this. It is available on YouTube and in podcast apps.
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how can I calculate latency in 5G network and what is the MatLab code to do that.
thank you
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I am trying to begin a new field of research with experimental works in the areas of wireless communications. What are the recent hot and interesting topics in this area?
May be the most interesting topic is the investigation and implementation of massive MIMO mobile communication systems. As the number of beam formed increases with controlled interference the spectral density increases leading to much higher bandwidth and number of users.
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I am currently working on a project that is based on optimizing cluster head (CH) selection for energy-efficient wireless sensor networks (WSNs) using evolutionary search techniques. For the purpose of comparison with classical baseline algorithms in this subject, I also want to compare my results with LEACH and LEACH-C. I have successfully implemented LEACH algorithm. However, I am not sure how to implement the LEACH-C algorithm.
This is the original paper that LEACH-C is proposed: Heinzelman, W. B., Chandrakasan, A. P., & Balakrishnan, H. (2002). An application-specific protocol architecture for wireless microsensor networks. IEEE Transactions on wireless communications, 1(4), 660-670.
In this paper, it was mentioned that the Simulated Annealing (SA) algorithm was used to determine clusters. It was also stated that SA selects among nodes having energy above the average energy. However, I cannot see any detail about how the neighborhood structures and the algorithm parameters were determined. Besides, I saw many other papers using LEACH-C in their experimental work, however, I could not find any guidelines for how they were implemented as well.
My question is that is there a standard to implement a LEACH-C algorithm? Thank you for any help you can provide.
Goran Popovic thanks again. So, we cannot speak of a single standard LEACH-C algorithm. Rather, it is constructed by an algorithm designer. For the sake of fair comparisons, it would be better if the papers mentioned details of how they used LEACH-C.
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If so, we're hiring! - come and join our team to help develop the next generation of intelligent, wearable drug delivery devices. Research opportunities now available in microsensor integration, transdermal delivery and microfludics, and system electronics/communications. Further details available from Dr Conor O'Mahony - feel free to discuss with us!
nice project
good luck
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I am looking for any source of information that describes how often an underwater wireless communication network is utilised on a certain day. For example, if you consider an underwater wireless sensor network to monitor water temperature, pH, salinity etc., how frequently do the sensors upload the data to the sink and the surface base station? I am trying to create a data communication traffic distribution pattern for underwater networks over a period of 24 hours.
Dear Kazi,
You ask about the physical model for distributing underwater sensors to monitor the properties of the water.
There is the see water. There is also the river water and there are lakes and pools.
Also there is also the distance of the sensor from the surface.
So, there is no specific answer for your question. I think it is very application oriented.
On the other side as the water is fluid, any concentration gradients of salt or temperature tend to decay with time because of the water molecular motion.
The best method to solve this problem is to make preliminary site surveying.
Or design your network to be able to increase the sampling time and adjust the distance between the elements of the wireless sensor arrays to achieve full observation of the intended water volume. As the wireless sensor nodes are based on microcontrollers they cab be reconfigured to Mach your needs.
These are different approaches to solve you problem.
Best wishes
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I have this topic :
• A review of techniques for improving the quality of the transmission channel in wireless communications at visible light frequencies, VLC.
• And wanted to make a chapter comparing VLC communication channel vs RF (Wi-Fi )channel but i couldnt find any helpful info could anyone help
Besmir
As for the spectral density of the VLC channels you can see our papers in different modulation techniques in VLC.
As the comparison
As for the comparison between the VLC and WiFi stems from the information carrier. VLC is in visible light and WiFi in UHF in radio frequencies.
The main difference is that the radio waves are able to penetrate the walls of the building. So VLC are confined in rooms.
The second main difference is the simplicity of the transmitter and the receiver.
VLC are much simpler.
As fore the specification of each system you can get them from their standards.
Best wishes
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Dear researchers,
Let's share our opinion about recent attractive topics on communication systems and the potential future directions.
Thanks.
FANET
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Dear community, Has anyone ever use the estimator for the parameters for a Two wave diffuse power (TWDP) distribution of the paper Joint Parameter Estimation for the Two-Wave with Diffuse Power Fading Model?
I'm currently creating a synthetic data from a TWDP estimation in order to test the estimator, however, the results from this procedure show a great dispersion from the real value. I'm wondering if the estimator from the paper has an additional constraint to be used.
I added some slides with the results I have so far and the codes used for the simulation.
Any help will be appreciated
Cheers
Jorge Gomez
Dear Mr. Gomez,
It is the first time I have ever heard about TWDP, but it seems to me that you can use a joint unscented Kalman filtering for parameter estimation in this case. You can find the details and a novel method proposed by me in the following article:
In standard joint unscented Kalman filtering, the parameter should not necessarily be linear with respect to states. However, in modified one, it must. Furthermore, you can find the Matlab scripts considered for this article in:
I think that you can easily try it. If you have any questions, please do not hesitate to ask.
With my kind regards,
Altan
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