Telecommunications Engineering - Science topic

It is not always true please refer LTE TDD frame - CableFree https://www.cablefree.net/wirelesstechnology/4glte/lte-tdd-frame/

Miguel Ferrando-Rocher

Hello dear friend, thank you

According to the article:

Do you think it is easy to use the thesis of trapezoidal dielectric shape in reality?

Fundamentals of microwave and RF Design by Michael Steer, NC State.

Buy a sheet of microwave absorber, cut a long triangle with a sharp point and glue it to one large wall of the waveguide with the point pointing towards where the power comes from, or glue two to both large walls. The longer the triangle and the sharper the point the better the match, generally. You can do it with stepped absorbers, or a pyramidal absorber too. It is hard to design to a vswr of 1.1 unless you design a stepped absorber and are very sure of its complex dielectric and magnetic constants, but making a taper longer will usually improve the vswr. The sharpness of the point is important. If it needs to cope with high power the sharpness of the point can be a problem because it may melt if the absorber has high absorption.

You could glue it to the side walls but it may need to be longer, depending whether the loss is magnetic or resistive.

You can also use a vane of nichrome on kapton film between slits on the centre-lines of the wide faces of the waveguide. If you do this you can adjust the way it tapers in while looking at the S11. https://www.dupont.com/products/kapton-rs.html might also be suitable.

You can test it on a Vector Network Analyser (VNA) with a good coax to waveguide adaptor. 1.1 vswr is about -26 dB so if you want to be reasonably accurate the adaptor needs to have S11 less than -40, unless you can calibrate on the waveguide side, using waveguide open short and load, for instance.

Technology by E and I transaction

Totally agreed with Md. Khairul Islam

A(in dB)=10log₁₀(A) or A(in dB)=20log₁₀(A)

This is a personal rewording of ideas expressed by A. S. Tanenbaum at its book Distributed Operating Systems, but applied to communications:

It can be proven ( http://en.wikipedia.org/wiki/M/M/1_model Kleinrock, 1974) that the mean time between issuing a request to send a message and getting it completely transmitted, T (queueing time + service), is related to lambda (arrival rate in packets/s) and mu (mean service time) by the formula T = 1/(mu - lambda).

Consider a communication link at 64 kbit/s processing packets with exponentially distributed lengths with average packet size of 50 bytes, then the mean service time (1/mu) is 6.25 ms and this link should be able to handle up to 160 packet/s (maximum lambda). If it just gets 120 packets/s, then the mean Tx time will be 25 ms.

Suppose now that we have n communication lines at 64 kbit/s processing the same type of packets (average length 50 bytes exponentially distributed) at an arrival rate of 120 packets/s. The mean Tx time is the same, 25 ms. Now consider what happens if we use a single link able to send packets at n.64 kbit/s. Instead of having n communication lines at 64 kbit/s we got a single communication line n times faster, with an input rate n.lambda and a service rate n.mu, so the mean response time has got divided by n also.

This surprising result says that by replacing n small communications links by a big one that is n times faster, we can reduce the average response time n-fold ( http://en.wikipedia.org/wiki/Queueing_model#Multiple-servers_queue ).

This result is extremely general and applies to a large variety of systems. It is one of the main reasons that airlines prefer to fly a 300 seat 747 once every 5 hours to a 10 seat business jet every 10 minutes.

Dividing the communications capacity into small channels, each with few users statically assigned, is a poor match to a workload of randomly arriving requests. Much of the time, a few lines are busy, even overloaded, but most are idle. It is this wasted time that is eliminated in the high speed single link and the reason it gives better overall performance.

In fact, this queueing theory result is also one of the main arguments against having distributed systems at all and argues in favour of concentrating the computing power as much as possible.

However, mean response time is not everything. There are also arguments in favour of small channels and distributed systems, such as cost. In general, the cost of N single resources of cost C is N.C, but the cost of a single resource N times better is C^N, or it can be impossible to build it at any price. Reliability and fault tolerance are also factors to consider.

Moreover, it must be considered that for some users, a low variance in service time may be perceived as more important than the mean response time itself, specially for interactive applications. Consider for example web browsing through your own ADSL line, on which asking for the same page to be displayed always takes 500 ms (at least if served from the central office cache). Now consider web browsing on a shared high speed link on which asking for the next page takes 5 ms 95% of the time and 5 s one time in 20. Even though the mean here is twice as good as on the private ADSL line, the users may consider the performance intolerable. On the other hand, to the user running P2P file transfers, the high speed link may win hands down.

A possible compromise is to provide both options, providing each user with a small single amount of reserved capacity for interactive tasks such as web browsing and running all non-interactive transfers (e.g. P2P, mail, SFTP...) on the rest of shared bandwidth of a high speed link.

A related joke read on the Embedded Muse 223: Why does *my* queue at the supermarket usually move the slowest?

You compare yours to the ones on either side. The odds of yours being

the fastest are 1 in 3 if you compare yours to the immediately adjacent

queues, 1 in 5 if you look at two lines on either side, etc. If you

want to feel better about it, join the queue all the way on the end and

you'll have fewer others against which to measure.

I did confuse confuse bandwidth with delay a bit, but not in recent comments, I think, because I realised I was doing it.

Unless the entangled pairs are prepared on earth and then half are sent to Jupiter on the satellite, which would require coherence lifetimes of years (many orders of magnitude above present lifetimes), a signal has to be sent from Jupiter at lightspeed (for instance a photon entangled with the state on Jupiter) to convey the entanglement information between the two sites before the quantum measurement, so that the half of the entangled state can be set up on earth. This means that the actual data rate is still limited by the bandwidth of the lightspeed signals, even if data can be sent with no delay,

I guess if zero delay was possible, it would still be useful, for things like steering a remote vehicle, or conversation.

I expect that each entangled state will carry 1 bit, one Q-bit.

I am not sure instantaneous communication will ever happen. It may. I don't understand it enough to be sure it can't work. I hope it may be possible. It would also raise lots of interesting problems with relativity. I wouldn't invest my pension on it, but I might invest fun money.

Very interesting question, but also very difficult to know any research in this regard, Prof. Vadym Slyusar. It is a military secret.

The military revealed information regarding optical fiber communications entanglement * (ARL, 2019), but not entanglement in space.

* https://www.labnews.co.uk/article/2030084/us-army-project-sets-quantum-entanglement-record

Best Regards.

What i can’t understundom you Kenechukwu Emmanuel Umeh

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

FromTanner there is @ MIT or Cornel University a very old document from 2008 related probably to the old Tanner v13 (tdb-based layout: Tanner data base, since 10 years Tanner is using OA open access for storing layout views!) about the Dev-Gen 13 (Device Layout Generator).

This document is related to a very old Tanner L-edit release, therefor any statement about the existance of Dev-Gen in recent Tanner 2016/2020 releases is doubtfull.

You will need the scripts behind for the newer OA-based Tanner L-edit releases....

see page 11 related to inductor Dev-Gen

The reliability of data transmission characterizes the probability of getting a distortion for the transmitted data bit. This indicator is often referred to as the Bit Error Rate (BER). The BER value for communication channels without additional means of error protection is 10-4 — 10-6, in optical fiber — 10-9. A ber value of 10-4 indicates that on average, one bit is distorted out of 10,000 bits. The q-factor of the receiving system Q is determined from the expression:

Q = GA/TC,

or, in logarithmic form:

Q[dB] = GA[dB] - 10lgTC[x].

It is the q-factor of the receiving system that determines the signal-to-noise ratio (C/N) at the output of the low-noise Converter (LNC or LNB). It is important to note that the final C/N value does not depend on the LNC gain.

First basic step is to define "strong wind" speed, and then compare that with the quadcopter's maximum speed. No Return To Home (RTH) feature can be effective as long as wind speed > quadcopter maximum speed so "speed" has to be first defense. Once quadcopter max speed is exceeded, it is just be a matter of time before the quadcopter is out of ground control range; options then are to land, and wait for input, (maybe not a great option in heavily wooded areas, or over water), or switch to an autonomous mode which will attempt return to base GPS location as long as power allows.

Next consideration would be turbulent response; in strong winds, particularly in urban areas, where wind gusting around buildings will make control response times critical.

Note also that GPS-enabled RTH features will struggle with tall obstacles, be they trees or high rise buildings, that block the (most direct) return path.

Agree

I'm interested. My email ID-farhanatasnimanti99@gmail.com. Thanks in advance.

I have the same question Anudeep. Did you figure it out by any chance?

I use ns 2.35

what about that?

A good place to start would be understanding the behavioral model first by any scholar book such as :

https://www.cambridge.org/core/books/rf-power-amplifier-behavioral-modeling/53306384B5A017F4BE2B05E9D2C097EC

What is impact of your paper getting published in Springer Lecture notes?

Most of works are relating to downlink NOMA. For uplink NOMA, different system model and problem formulation should be considered.

You can have a look at the following article for a precise methodology!

http://www.eurecom.fr/resources/common/public/seminar/cm/2005/PresentationGeraldMatz.pdf

Hello!

In summary, when a UE try to access the BS by transmitting Random access Preamble (RACH), it must receive an acknowledgement from the BS and uplink synchronization must be done. But, for some reason (distance or collision between two UE's RACH) the UE doesn't receive the acknowledgement, it will transmit perform the RACH again after waiting for some specified time. Again, if it doesn't receive the acknowledgement then it will increase the power to compensate the power loss. This is just one example. There are many other parameters that can effect the battery of the UE. Like, handover, data rate, etc.

Have a look at these papers:

LTE UE Power Consumption Model: For System Level Energy and Performance Optimization

Analyzing mobile applications and power consumption on smartphone over LTE network

Battery life idle parameter optimization of UE in self organizing network

This is interesting query. I think there are two ways to think about it. Firstly, we have extended ourselves and our information about other groups and cultures on a scale that is expansive and incredibl. Secondly, people have distanced themselves from others sitting next to them and become lonely. Overall, I feel that we are gathering more psychological space in our devices but have no real time sense of people's lives and events happening right in front of us.

For antenna parameters HFSS is quite good choice.In case of it's physical and equivalent circuit simulation please try another software, ADS

Using directional antenna for one receiver would make it large antenna to concentrate the radiation in small angle making it very directive. If one could make a pencil like beam this would be a very suitable solution. It will also very power efficient. The ability of the designing antennas with high directivity increases with the increase of the frequency. If the use of optical communication system is allowed, then one can use laser beams. The use of MIMO system can be used to focus the radiation on an intended direction and null it in other specific radiation.

A second solution is to use a coded transmissions. such those used in the code division multiple accessing. The one which is very simple is to encrypt the data transmitted such that it can be only decrypted by the one who has the key.

Best wishes

you can search the Matlab Community (File Exchange) or request from 5gnow project

Dual band refers to a device which uses two different frequencies to communicate.

Dual radio refers to a device which uses two different protocols to communicate.

Maybe an illustration would help. A dual band device is like a person at a party who can move between two different rooms (different frequencies) to talk with other people, while a single band device would be limited to talking to people in only one room. On the other hand, a dual radio device can speak with people who speak in two different languages, while a single radio device can only speak one language.

A dual radio device is typically used as an intermediary between two different networks like 802.11 (like WiFi) and 802.15.4 (like many wireless sensors).

Thanks all

If power line carrier communication is used for signal transmission through the power conductor itself then only wave trap is required to filter out the noises.

Previously published papers are not considered. Only those papers are considered, which are submitted after the journal is indexed.

It all depends on the career aspirations you have. Ask yourself, where do you see or want to see yourself in the next 5 years and 10 years. Does this position provide the platform for you to reach there.

If you want to stay in academic sector, then this RA might provide you with opportunity to do some research, produce from journals, which will be useful to get a funded PhD position.

If you see yourself working in industry (not in R&D), then may be you want to reassess your strategy now and target industrial jobs from now itself.

Best of luck.

Is Brett's choice of system giving you trouble?

you can make some different choice, Wimax is not the best.

Dear Khan,

I suggest you to see links and attached files in subject.

-Device-to-Device Communication in LTE-Advanced Networks: A ...

- Futuristic device-to-device communication paradigm in vehicular ad ...

- A Scheme of Ad-hoc-Based D2D Communication in Cellular Networks

- Device-to-Device (D2D) Communication: Fundamentals with ... - WNCG

- A Software-Defined Device-to-Device Communication Architecture for ...

- Performance Analysis of mmWave Ad Hoc Networks

https://arxiv.org › cs

Best regards

Trust me,

You can not rely on the answers here.

Every one is talking about his/her favorite simulator based on his experience and background.

You can see always a conflicting answers in this regard.

You need to quickly test both first.

You can make a simple approximation; stop band 1 MHz, pass band 9 MHz.

The ratio of the bands is 9. Assuming Czebyshev type of the filter with n=3 you will have 49 dB of attenuation in the stop band. Thus you need a filter of the 4 order.

CoMP scheduling can be divided into two types - Centralized and Distributed based on the method of coordinating the eNBs. Usually the attached eNB acts as a master node in Centralized scheduling and other nodes in the eNB set serves as slave. Master ( or central) node performs the scheduling process. On the other hand, each eNB in the set performs the scheduling process in distributed scheduling approach according to the CSI feedback from their cooperating eNBs. Conventional schedulers do not coordinate with other eNBs.

Dear Mr. Muhammad Usama,

It would be great if he can integrate the pattern of the designed antenna for either RFID or WSN into the OPnet. This is because I think he wants to simulate a real scenario for the complete system including the communication layers and accordingly he can test and/or edit to have better performance.

Regards,

Ahmed Elawamry

As per my understanding of the relaying systems,

The SNR, represented by $\gamma$ of any link (SR (source to relay) or RD (relay to destination)) would be dependent on the channel gain h, corresponding transmitter power P and Noise power N_o or $\sigma^2$, according to the following formula $\gamma=P|h|^2/N_o$. First you need to find the $\gamma_{SR}$ and $\gamm_{RD}$

Then, for Decode and Forward case, end to end SNR calculated at the destination $\gamma_{D}$ is the minimum of both $gamma_{SR}$ and $\gamma_{RD}$.

For AF case you need to use this formula,

$\gamma_{D}=(\gamma_{SR}*\gamma_{RD})/(\gamma_{SR}+\gamma_{RD}+1)$

I hope this is answer to your question.

Correct me if anything is wrong.

Thanks

Yes Aparna Sathya Murthy .

I need useful tutorials and links,which might be useful in implementing it in Opnet simulator.

I think maybe we are just talking about different protocol layers? It's a bit like asking why IEEE 802.3, the Ethernet standard, doesn't address security. Security is built on top of Ethernet. At least, that's the typical way of implementing security.

The other point is that a telecom does need to implement security measures, but this is primarily to protect itself. For example, their system management messaging, routing tables and routing protocols, have to be secure, to prevent a hacker from disrupting the system. But it doesn't do much good for the telecom to secure user traffic, if ultimately, at the edges, the traffic has to be sent in the clear. If a user of the telecom wants security, that user must install a solution that protects traffic end to end, from inside his PC or smartphone, all the way to inside the PC or smartphone at the other end. Or in the case of an enterprise network, security could be implemented until the link is inside that enterprise's "secure enclave," perhaps not all the way to the end system. So for example, the enterprise may deploy secure tunnels, through a telecom network, where the end points of those secure tunnels are inside secure enclaves.

Otherwise, anyone along that path would be able to monitor the communications. And there is no reason for a user to trust the telecom itself, ultimately, if that user needs security.

Security can and is implemented at any protocol layer. From the standpoint of a user, though, any security measure that is not end to end would be of questionable value. That's why people use Transport Layer Security so often, when dealing with communications across telecom or other network services. It's security built over the telecom link, carried transparently by the telecom or by the digital network.

NS2 is no longer used and active development stopped 7 years ago. So its best you use NS3 or NetSim or OPNET. And like you say you need to have lots of time and be very good at programming (in multiple languages) for Ns3.

In your code,mention the units associated with each parameter.you have calculated TL in nepers but added like TL in Db and converted again to nepers which I feel the reason for infinite source level

Dear Khan M. Asghar

This can happen if:

- You have a battery that is charged by nuclear decay during a flight;

- You have a battery that is charged by a chemical reaction during a flight (burning hydrogen, fuel cells or some other);

and

- this battery can generate the output power you need to have a beneficial effect.

For all these suggestions there are solutions, the question is what finances can be allocated to your goal.

And another - You have a battery that is charged by electromagnetic energy (refer to N. Tesla's patents) that can be extracted from space. Which is also not to be ignored :-)

Thank you yousif , lateef and aparna. I have found these references very helpful.

I'd use commercial 3G-4G mobile phone networks in order to send and receive short communication lines that help upload discrete commands (eg. Speed, Altitude, Go to a preset waypoint, Cancel mission, Go back home....) and download basic status information. Wouldn't work for downloading real time imaging, but maybe acquiring some basic environmental information.

Dear Mohamed-Mourad Lafifi,

Thanks for your help. Although I have found the solutions, these articles will help someway. 

Thanks again. 

Hello George Slade,

1. Thank you for your caution about the pre-processing power. My mission is to design an algorithm which is able to detect and extract all radar pulses in the instantaneous bandwidth of 500 MHz in real-time.

2. I have no idea what I am looking for because there are so many types of radar signals out there. There algorithm should be universal enough to detect and extract most of radar signals at as low SNR as possible.

3. I have read some time-frequency analysis techniques. In the future, I will try with Short-time Fourier Transform and Wavelet transform techniques. Some other T-F techniques (e.g. Wigner-Ville distribution, Choi-Williams distribution, ...) may not be suitable in this scenario because of the cross-terms.

Do you have any additional suggestion for me?

Thanks and Best Regards,

Van Long

Salam alikom brother, 

For more acurate modelisation you must refere to this book :

I can share with you this book and matlab program... Just send me your e-mail. Good luck 

Main application of absorbers is isolation enhancement. They also can be used as filters and attenuators. 

Hellow, Of course FHSS is one, but is fundamental that in addition to secure on physical layer, the algoritms of channel codding, modulation ant others will be properly settings, but that leads to secure system of truth 

Thank you Ma'am for your guidance. I think, from dispersion curve, I will get resonant frequency of different mode. I want to know field patterns of different modes. How to identify TM_23 / TE_14 / HEM_10 etc modes...rectangular and cylindrical waveguide are available in Standard books on EM theory such as Harrington, Balanis, Schekunoff etc. I'm waiting for your kind guidance and reply.

I think it is true to say that a Wilkinson divider without a resistor is not a Wilkinson divider, but just a divider.  I think Wilkinson's aim was to reduce the cross-talk through dividers.

The frequency allocation is organized in world wide basis by international communication union. Every country has its own authority for regulating the use of the frequency spectrum. The bands are allocated fro specific wireless services. The ISM bands are allocated for industrial, scientific, and medical wireless services. The 2.4 band is allocated for microwave heating. 

In general there are factors governing the frequency allocation process where the frequency spectrum bands are divided among specific services some of them are licensed and the other is unlicensed.

For the factors governing the frequency allocation process please refer to the paper in the site:  https://www.itu.int/dms_pubrec/itu-r/.../R-REC-SM.1131-0-199510-I!!MSW-E.docx

best wishes

@Venu Dunde,

I have been working  on radar technique to improve range resolution, side lobe mitigation and target detection and  recently I have published a novel solutions with different technique (especially the antenna design part), Significant directivity and Side lobe reduction!

I wish this can help you:

Abstract:

With the advancement of radar technology, detecting objects, determining the structure of the target, and estimating the direction and the speed is prominently increasing. There is no doubt that small cross section targets are hardly identified and determined. This problem demands the need for ...

50 years ago long tapers were used, to get a broadband impedance change, for example.  Nowadays broadband components can be achieved with short stepped lines or short tapers - they become very similar as the steps get shorter.  You need prediction and optimisation code to design the shortest, low-loss components with short tapers or combinations of steps.

DMT is very sensitive to the symbol timing errors, so a standard synchronization is essential. The distortions from LED and PD limited the feasibility of identifying the symbol head or timing delay precisely through the method you mentioned above. 

Hope the reference will help you out.

Digital signal processing can be used many functional building blocks of the advanced communication systems. The soft ware defined radio technology is now a common practice for implementing advanced wireless transceivers standards in mobile communication networks, wi phi and wimax. The digital processing can be implemented either using field programmable arrays FPGAs of digital signal processors DSPs devices or a plat forms composed of the two chips in addition to general purpose processors. 

As for the functions that can be implemented are the source coding, channel codeine, encryption, multiplexing. filtering, modulation, mixing for frequency up conversion and the inverse processes. Normally the modulation is carried out at the base band model.

It can also realized in the pass band but one has to choose the carrier frequency as low as possible to save in the required computations as as the sampling frequency increases the computations required increases.

Logically the inverse processes in the receiver are also implemented using the same platforms.

So, the mixing can be realized using DSPs but you have to compromise the carrier frequency used  to save computations and power of the DSP.

It is advisable to carry out the mixing processes in the analog front end of the transceiver and use zero IF or low if mixing to lower the sampling frequency and save processing effort and power consumption. 

The system design helps choosing the most suitable system architecture of the wireless transceivers.

Best wishes 

Dear Mardi,

The different digital modulation techniques including the binary phase shift keying can be implemented using digital signal processors. The digital signal processor calcualtes the the required wave forms. In case of BPSK there are two possible implementations:

a base band implementation where logic one is represented by + V and the logic zero is represented by  -V , where V is any suitable scalar, and band pass representation where logic 1 is represented by V cos wct and the logic 0 is represented by - V cos wct.

Normally the base band implementation is the common method for DSP to save the computation and reduce the power consumption. If is necessary to implement BFSK in band pass form, it is advisable to select as low as possible carrier frequency wc.

For more information please refer to the link: https://cdn.intechopen.com/pdfs-wm/6846.pdf

Best wishes

Since protocols in CRN are generally cross-layered, I would suggest you go with NS2 ... However, if you are dealing with network modeling, MATLAB is a good choice ...  

This is the very purpose of "SDR": within the limits imposed by the hardware (bands, bandwidth, SNR etc.) virtually "everything" is possible.

I did not check the device you're targeting but - provided it's supporting the GSM bands - this should be possible.

I have not worked with the various 8-QAM formats at 43 Gbaud, but I can say that you need to supply more details for a useful answer.

What type of fibre is used, and in particular what is the effective area and chromatic dispersion coefficient?

Is this for an upgrade to an existing system, or for a new design?  Is there a single uniform fibre span, or multiple optically amplified sections in series?  Is there any in-line dispersion compensation or terminal dispersion compensation, or are chromatic dispersion and polarisation mode dispersion corrected by analogue or digital signal processing in the transmitter or receiver?

What is your tolerance to noise and distortion of the received constellation?  If chromatic dispersion in the link is low, then non-linear distortion accumulates coherently.  This means that distortion is large but deterministic, and amenable to compensation by digital processing of the received signal.  Conversely with high in-line dispersion compensation, mean square non-linear distortion is smaller (at an equivalent power level), but more noise-like and more difficult to compensate.

In a multi-span 43 GBaud system, non-linear noise, crosstalk and distortion is likely to accumulate with an increasing number of amplified sections as (N P² / Aeff²)  where N is the number of amplified spans, P is the per-channel launch power and Aeff is the fibre effective area.  The scaling is sensitive to chromatic dispersion and dispersion compensation strategy, and in very low dispersion systems, non-linear distortion can scale as N².

Are the sub-carriers co-polarised at  the transmitter?  Orthogonally polarised sub-carriers typically suffer less non-linear distortion due to cross-phase modulation.

Is this a single channel system or wavelength multiplexed?  In a WDM system, cross-phase modulation (XPM) and four wave mixing (FWM) can be significant, and may dominate over single channel distortion at narrow channel spacings, especially when fibre dispersion is low.  Stimulated Raman scattering (SRS) introduces amplitude crosstalk between more widely spaced channels, but is usually second order in typical submarine links.

Do you have access to simulation software such as VPI or Optisystem?  Alternatively, it is not difficult to build a split-step Fourier propagation simulation in Matlab or Octave.  This would allow you to investigate the sensitivity to launch power, fibre parameters and dispersion compensation strategy.

Hi,

Probably the equalizer should reset each SNR loop. I did it through a workaround but you can check the MLSE structure and do reset each snr loop.

check this code, it works!

clc;clear;

close all;

ii=1;

snr_vec=-10:1:30;

for snr_i=1:length(snr_vec)

 

snr=snr_vec(snr_i);

 

N = 100000;

%chCoeffs = [0.986+0.5i;0.845;0.337;0.32345+0.31i;0.2];

chCoeffs = [0.5;0.00000000001];

mlse = comm.MLSEEqualizer('TracebackDepth',10,'Channel',chCoeffs,'Constellation',(1/sqrt(2))*qammod(0:3,4));

errorate = comm.ErrorRate;

 

 

Tx_Data = randi([1 2],N,1)-1;

modData = (1/sqrt(2))*qammod(Tx_Data,4,'InputType','bit');

chanOutput = conv(chCoeffs,modData);%filter(chCoeffs,1,modData);

chanOutput = chanOutput(1:end-length(chCoeffs)+1);

noise = (randn(1,length(chanOutput))+1i*randn(1,length(chanOutput)))/sqrt(2)/sqrt(db2pow(snr));

Rx_data = chanOutput+noise.';%awgn(chanOutput,snr);

equalized_Data = mlse(Rx_data);

% clear mlse

% mlse = comm.MLSEEqualizer('TracebackDepth',10,'Channel',chCoeffs,'Constellation',(1/sqrt(2))*qammod(0:3,4));

% reset(mlse)

demodData = qamdemod(equalized_Data,4,'OutputType','bit');

errorStats = errorate(Tx_Data,demodData);

% errorStats(2)

ber(snr_i) = errorStats(1);

save ber ber snr_vec;

NumofErr(snr_i) = errorStats(2);

% ii=ii+1;

clear;

load ber;

end

semilogy(1:length(snr_vec),ber)

grid on;

 

I hear from several researchers that it is due to highly sensitive samples. For example there is a higher risk of contamination with the ones that are unattached. Is this not the case?

Hi,

A very interesting question, even it's a question for all who are working in metamaterials. Under CST microwave studio, in material assign section, we can define permeability and permittivity as well as loss tangent for new material.

Cookbook about metamaterials, I will have to look forward to.

Thanks,

Have wireless repeaters just like wired ones.

Thank you for your answers. 

@Dan Gani : "By writing "Base Transceiver Station", do you mean cellular base station?"

Yes. But without the mat and the antennas. I just focus on the shelter containing the electronic equipments

@Mohammed Al-shamarti : Unfortunately, I can't read Russian. Thank you anyways.

Concerning the heat produced by a typical cabinet, I only found this information on the net (all the articles say exactly, word for word, the same sentence) : "Typical cabinet heat emissions may be as large as 1600-2500 W".

And concerning the dimensions of a typical shelter, I only found the attached document.

Do you think these informations are reliable? Otherwise, do you have other sources?

Dear Mohamed ,

welcome,

Pulse shaping is useful as it reduces the inter symbol interference where preserving the required band width to transmit the digital pulses representing the logic values, the logic one and the logic zero. The minimum bandwidth required to transmit a sequence of digital pulses having rate fb is fb/2, where the symbols are put in form of sinc pulses.

So to reduce the the bandwidth required for digital transmission to a minimum one has to shape the pulses and put them in sinc x form. This is accomplished by using a Nyquist filter. Nyquist filters are not practicle, instead one uses raised cosine filter with an excess bandwidth compared to Nyquist filter,, so the required channel bandwidth will increase to fb(1+alpha)/2 where alpha is called the grading coefficient. Practically alpha is made 0.3. 

Such raised cosine filter suppress the side-lobes of the sinc function leading to more confinement of the pulses in the time domain and consequently less intersymbol interference.

The effect of the pulse shaping is useful for limited band width channels. In case of unlimited band width there will be little effect of pulse shaping. Since in real communication system the channel bandwidth is limited, one has to pulse shape the transmitted pulses.

Please for more information about the effect of pulse shaping in Blue tooth follow the link:https://www.researchgate.net/publication/261489967_Performance_evaluation_of_digital_modulation_techniques_used_in_Bluetooth_physicalradio_layer

best wishes

Dear Anshul Anand,

Group-Communication has two parts:

1) Collecting data from a group.

2) Sending commands to a group.

I suggest to you  attached files in topics.

Best wishes

Very different frequency bands involved here.

TV white spaces are in the UHF band mostly, so that's in the 470 MHz to 700 MHz range, more or less, depending on country.

WiFi operates in the 2.4 GHz band, for IEEE 802.11b, 802.11g, and 802.11n, and in the 5 GHz band for 802.11a, 802.11n, and 802.11ac.

So yes, the TV white spaces could be used for the long haul Internet broadband connection, and for that, take a look at the IEEE Standard 802.22. It should be quite feasible to go from an 802.22 transceiver/router to a WiFi access point, to serve a household with Internet broadband service.

These IEEE standards are all available online, at:

Hi, perhaps another solution is to solve two linear systems of the form A.x=b where b is set to (1,0,0...0) and (0,1,0,0....0) respectively, just to obtain the first two columns of the inverse of A.

The thermal noise power over a bandwidth W Hz can be computed as

−174 + 10*log10(W) dBm

in room temperature. To that you can add the noise figure (amplification in the receiver hardware). For a "nice receiver" it would be, say, 3-6 dB