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Telecommunications Engineering - Science topic

Telecommunications engineering, or telecom engineering, is a major field within electronic engineering. The work ranges from basic circuit design to strategic mass developments.
Questions related to Telecommunications Engineering
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Hello good time
What metals can be used in the design of high frequency devices such as Coaxial transmission lines , waveguides, coaxial to waveguide adapters? (Diamagnetic, paramagnetic or ferromagnetic)
For example, can I use tungsten rod , which has a magnetic permeability coefficient of 1, to build a coaxial transmission line? (What is the appropriate magnetic permeability number for the metal used to have low insertion loss(S21)?)
Thank You
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Hello .
I want to design and build a waveguide load in X Band.
1- How to design that the VSWR is maximum 1.1? (What should I use inside the waveguide, what material? With what dimensions?)
2-How to test it with Network Analyzer after making it?
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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.
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In the area of electronic banking, including mobile banking, commercial banks improve technological solutions for the use of smartphones for the purpose of conducting financial transactions by clients.
Commercial banks spend the most resources on developing security systems, reducing gaps in online banking systems used by cybercriminals and improving IT systems risk management procedures.
The changes taking place in online banking, including mobile banking, are currently determined primarily by the technological progress related to telecommunications and IT devices.
In view of the above, the current question is: Determinants of the development of mobile banking?
Please, answer, comments.
I invite you to the discussion.
Dear Friends and Colleagues of RG
I described the problem of cybercrime in publications:
I invite you to discussion and cooperation.
Thank you very much
Best wishes
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Technology by E and I transaction
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Please refer to this example. it is taken from wireless communications book by william stallings. 
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Totally agreed with Md. Khairul Islam
dB is just a unit which converts a numeric value into decibel scale and for conversion , we have to use log10
A(in dB)=10log10(A) or A(in dB)=20log10(A)
For power, you have to use 10 log(P) whereas for voltage or current, you have to use 20 log(Vor I).
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I need help with Queuing theory, easy explanation to M/M/C?
What are the parameters of the M/M/C queuing model?
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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.
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Russian project to explore the moons of Jupiter after 2030 will be based on the nuclear propulsion spacecraft "Nuklon" with an electrical energy power of 0.5 MW. Such energy power gives the opportunity to significantly increase a data transfer performance to Earth. In my opinion, the speed of data transfer can be increase to 100 Mbit/sec. This value will be enough to use 4K Video for the investigation of dynamic processes in the atmosphere of Jupiter and moons. What is your opinion about this?
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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.
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The problem of data transmission from Mars to Earth is a big latency time. Could quantum entanglement communication reduce this latency?
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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.
Best Regards.
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Can someone help me to solve this task below.
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What i can’t understundom you Kenechukwu Emmanuel Umeh
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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?
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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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I am working on the project of LC voltage controller oscillator. i have design a LC VCO for C band application. I am facing problem to design the layout of inductor on L-edit of Tanner EDA tool. can anybody help??
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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
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I am working on simulating two wave with diffuse power fading channel in MATLAB but not able to implement it. Can any one please provide the pseudo code or matlab file for the same
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BER analyzer parameters meaning.
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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.
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As we have seen that most powerful and expensive quadcopters being swept away by prevailing wind gusts and losing connection with the controller, and even that “fail-safe” GPS-enabled Return To Home feature will struggle and oftentimes fail when flying into a strong headwind.
How to make it reliable and robust for sever weather conditions?
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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.
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I am looking to design a S-Band  BPF in LTCC with wide stop-band.So to design this filter I need to design L and C with high SRF
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Agree
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Good morning
I'm interested for cooperation. My reseach is treatment of signal  (colon Cancer.... ) and radio mobile for telecommunications.
can you explain your points.
good day
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I'm interested. My email ID-farhanatasnimanti99@gmail.com. Thanks in advance.
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We know optical networks are undergoing significant changes. There continues to be increasing demand for bandwidth, just as 10 Gb/s technology has reached maturity, service providers are already installing higher bit rates, including 40 Gb/s and now 100 Gb/s per wavelength and nowadays 400 Gb/s is receiving a lot of attention. The 50 GHz ITU wavelength grid divides the optical spectrum range into fixed 50 GHz spectrum slots, but it is likely that bit rates greater than 100 Gb/s will not fit into this scheme. Even if sufficiently broad spectrum is available, high data rate signals become increasingly difficult to transmit over long distances. So to properly address this challenge, one needs flexible and adaptive networks equipped with flexible transceivers and network elements that can adapt to the actual traffic needs. The combination of adaptive transceivers, a flexible grid, and intelligent client nodes enables a new “elastic” networking paradigm.
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This software is freeware. Just send a email to luiz.bonani@ufabc.edu.br
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I designed MEMS bridges and am now observing the phase shift by checking S(2,1) parameter -angle degree. Is this correct and can I observe the change in phase in HFSS?
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I have the same question Anudeep. Did you figure it out by any chance?
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I need to add the field of annulus number (area in which sensor is located from sink)  which is depend up on the hop count present in HELLO list.  So in which file the modifications has to be done, to add the field.
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I use ns 2.35
what about that?
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I just came across a problem in power amplifier used in communication chain which exhibits nonlinearity due to memory effects.This can be nullified with a help of digital pre-distortion using signal processing algorithms.
Can anyone please tell how it is achieved and explain the math part behind the algorithm?
Suggestion of book or a research article is preferred.
Thanks
Rakesh
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A good place to start would be understanding the behavioral model first by any scholar book such as :
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I am working on transmitting ECG signal over wireless body area networks. According to IEEE802.15.4 standards , I am using ZigBee transceiver at 2.4 GHZ . Complex baseband equivalent channel model is used.
The steps are as follows :
1.      Signal Compression
2.      Quantization
3.      Coding
4.      OQPSK modulation using the matlab function (oqpskmod)
5.      Fading Channel plus AWGN
6.      Equalization
7.      OQPSK Demodulation using the matlab function (oqpskdemod)
8.      Decoding and Dequantization
*  According to the IEEE 802.15.4 standard, a pulse shaping step is performed in the transmitter after the OQPSK modulation step . 
I didn`t perform this pulse shaping process, and I obtained reasonable results. Is it necessary to perform this step ? 
If  yes , How should the receiver be modified ?
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Your Design should follow IEEE 802.15.4 standard. Since pulse shaping is being used in the standard and ZigBee utilizes the IEEE 802.15.4, you can not ignore it.
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Could anyone please suggest which one is easier to get accepted for conference proceedings inclusion?
Lecture Notes in Computer Science(LNCS), Lecture Notes in Artificial Intelligence (LNAI), Lecture Notes in Bioinformatics (LNBI), LNCS TransactionsLecture Notes in Business Information Processing (LNBIP), Communications in Computer and Information Science (CCIS), Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering (LNICST), and IFIP Advances in Information and Communication Technology (IFIP AICT), formerly known as the IFIP Series.
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What is impact of your paper getting published in Springer Lecture notes?
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I am analyzing the complexity of resource allocation problems in NOMA systems. The network model is shortly summarized as: a base station (BS) and multiple users (UES), singles for all UEs are superimposed at the BS, and the objective is to allocate at the BS so that optimize the resources. In addition, I am using the network sum-rate maximization is a baseline, which is NP-Hard according to my own finding. However, I am not sure about this (NP-Hardness of the sum-rate maximization problem).
Does anyone have any suggestions for me?
Many thanks in advance.
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Most of works are relating to downlink NOMA. For uplink NOMA, different system model and problem formulation should be considered.
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Assuming traffic bandwidth B is equally divided into N subcarriers and each subcarrier may be shared by multiple users in a time-division manner, does the following transmission rate for the k-th user in the i-th cell on the m-th subchannel make sense? Any explanation would be greatly appreciated! Thanks in advance.
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You can have a look at the following article for a precise methodology!
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Hello!! I have some questions regarding the effects of physical parameters over a UE battery usage. I want to know that what are the factors which increase a user's battery drainage in LTE? What are the effects of Low SINR over UE battery? How does Low received power effects ? Distance from a BS ?? Data size and data rate play any role over battery ?? Or any other factors which need to be controlled for Battery Efficiency.
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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
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What do you notice changes in behavior, sociological changes in societies in connection with the advancement of telecommunications technologies?
More and more information is contained in our smartphones? More and more practical information, contacts etc. are archived in smartphones without remembering them.
Once, in the era of fixed-line telephony, people knew by heart the telephone number, whereas now in the era of mobile telephony, mobile, when all information is stored on a smartphone, people remember less and less.
In connection with the above, it is an example of the progressive changes in behavior, sociological changes in societies in connection with the progress of information and telecommunications technologies.
Do you notice these changes?
What are you noticing other progressive changes in behavior, sociological changes in societies in connection with the progress of information and telecommunications technologies?
Please reply
Best wishes
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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.
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Antenna design in one software varies with result in another software. Also which one is better for mesh analysis.
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For antenna parameters HFSS is quite good choice.In case of it's physical and equivalent circuit simulation please try another software, ADS
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Without using triangulation, how might one broadcast a signal that would only be picked up by one antenna out of the many present?  Or, if not one antenna, then perhaps just a few close by.  These antenna are not stationary.  We can use any frequency that we want, although a higher frequency would be best.  Each antenna has a slightly different Q, length, and width.
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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
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we come to generation that subcarriers are no longer orthogonal to each other. here the different parameters such as amplitude, frequency and phase will change for each subcarrier. by using cognitive radio the spread spectrum is reduced. GFDM plays a major role here. im looking for an MATLAB code or LABVIEW code to analyze this. 
anyone related to this work, kindly reply 
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you can search the Matlab Community (File Exchange) or request from 5gnow project
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What is the main difference between dual band and dual radio?
Let
A system equipped with:
Dual Band= 2.4 GHz and 5 GHz
Dual Radio=802.11 and 802.14.5
where 802.11 with 5GHz is deploy between air to air link
and 802.11 with 2.4 GHz between air to ground.
similarly some nodes are also connected through 802.15.4 with 2.4 GHz between air to air.
The above system is dual band dual radio
or triple band dual radio
or triple band triple radio?
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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).
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Hello everyone,
I am preparing to simulate a Fiber To The Home FTTH system. My problem is related to the implementation of multiplexing the upstream from the users (ONUs) using OTDMA. At the OLT, I need to demultiplex these signals using the optical gate to get individual data of each user. How to design the optical gate?. the bit rate is 1.25 Gbps and the number of users is 32.
I am looking forward..
Best regards
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Thanks all
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What is the function of line traps other than communication?
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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.
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If a Journal was not indexed at the time of publication. After few years if that specific journal gets indexed with Scopus or SCI/SCIE. What will be the status of previously published papers?
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Previously published papers are not considered. Only those papers are considered, which are submitted after the journal is indexed.
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I have done my B.E in Telecommunication Engineering from Mehran University of Engineering & Technology, Jamshoro. I want to ask about the scope of a Research Assistant in a Public Sector University in Pakistan. I am getting the opportunity to pursue my career as a Research Assistant but I am reluctant to avail this opportunity due to some unnecessary project conditions.
What do you suggest me whether I should avail this or not? Your advice would be highly appreciated.
Thanks in advance :')
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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.
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I need to buy a telemetry system and I need help. I want DSI but I have better price offers. My problem is that I do not know if the data provided by other producers are real or not.
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Is Brett's choice of system giving you trouble?
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I am trying to connect different UAVs in ad-hoc manner.I am interested to use Wimax from the base station to the backbone UAV, that would be further connected with WIFI.
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you can make some different choice, Wimax is not the best.
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How can we differentiate between D2D communication and Adhoc networks?
I am also wondering what D2D covers what ad hoc networks haven't covered yet ?
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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
Best regards
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Which simulator is better to simulate D2D communication in LTE networks ?
Thanks.
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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.
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chebyshev band stop filter , order 3
pass band = 140 MHz to 145.5 MHz with 1 dB attenuation
stop band = 149.5 MHz to 150.5 MHz with 60 dB attenuation 
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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.
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How does a CoMP scheduler work? Also what are the differences with conventional schedulers and its advantages?
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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.
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How can we simulate directional and omnidirectional antenna in Opnet simulator for UAVs Networks?
Thanks
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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
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I wonder if you could help me with the SNR (end-to-end) expression of a wireless communication system with a detect and forward relay without direct link (please see joined).
Best regard.
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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
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I need materials in any form regarding antenna pattern in Opnet for learning purpose.Your help would be highly appreciated.
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Yes Aparna Sathya Murthy .
I need useful tutorials and links,which might be useful in implementing it in Opnet simulator.
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For my PhD topic and research, I wish to work on intercell interference mitigation (ICI) in heterogeneous networks (HetNets) using cell range expansion (CRE) in combination with hybrid power control (HPC) techniques. How can I effectively implement this?
Actually, I intend exploiting the advantage of CRE in offloading some users from macrocell to small cells (picocells or femtocells). Thereafter, power control technique/algorithm would be used to mitigate co- and cross-tier interference to offloaded users. I will appreciate any guideline on how to implement this, coupled with any helpful codes, links, textbooks and softwares.
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Can you please share, any Matlab code for Interference mitigation you find useful?
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i've noticed that majority of engineers are focusing on the technical side of development of telecom equipment either in mobile communication or any other sub-field , compared to computer networking ,engineers do their best to develop new security solutions ! 
i don't understand why there's always this  lack of interest in security field in telecom  !! 
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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.
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Kindly guide me about choosing best simulator for dynamic routing in Adhoc networks.
Can we use Opnet simulation for high level work?
Thanks
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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.
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Hi
My question is related to underwater acoustic sensor networks.
I have written the attached matlab code to calculate required transmission power based on distance between the sender and receiver and SNR threshold at the receiver(My aim is to calculate energy consumption ultimately). However I get infinity for required Intensity(Req_I) and Required Transmission Power (Req_Pt). Please suggest what is the mistake that is resulting in my required transmission power to be infinity and how can I fix the problem.
Best Regards
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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
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As we know that larger the battery capacity, the longer your drone can function in one single charge of it. Small drones are normally best suited for 20 to 30 minutes flight.Our requirements are beyond this i.e longer flight on a single charge.
So what are the possible ways to overcome this issues and to prolong the flight of a small drone?
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Dear Khan M. Asghar
"I am more interested in things like some constant charging device that dont let the battery down."
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 :-)
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I am designing a VLC system with DMT. For the channel response, I have chosen BPSK on all subcarriers and calculated the SNR of each subcarrier from BER-SNR relation.
For subcarriers with SNR greater than required SNR for BER of 10^-3, I have increased the number of bits over that subcarrier. (for example if subcarriers  SNR is greater than 9.8, I have changed the bits assigned from 1 to 2).For this new bit-loading, I have found that SNR of both QPSK and BPSK loaded subcarriers getting degraded. How can I arrive at a decent bit-loading to maximize the transmission?
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Thank you yousif , lateef and aparna. I have found these references very helpful.
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What could be the maximum distance that one can control a UAV from?
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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.
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Dear and Respected Colleagues
I am requesting to all those respected mentors and researchers working on Optical Communications Please help me on PM to IM conversion to generate UWB pulses?????
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Dear B Das
I have a question on SOA. Please help
It has been learnt that if AWGN/White light source is coupled with CW probe and Pump signals (Data signal) and then the cumulative signal is launched in a SOA for XPM and amplification,then the SOA is very less noise tolerant and the pulse shapes and Eye diagram badly degrades at the receiver side.Why SOA is very sensitive to noise and less immune to it?
please comment and share any written literature on this property of the SOA
regards
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I am working on systematic polar codes. But the problem is, after decoding we need to encode the decoded bits again to have the original information. 
However, belief propagation (BP) decoding provides soft output. There is a problem again: after one iteration, the output (which would be used as the input of next iteration) is changed. Therefore, if it is used as the input in the second iteration, it generates an error. In this case, what would be the possible solution?
Thanks in advance. 
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Dear Mohamed-Mourad Lafifi,
Thanks for your help. Although I have found the solutions, these articles will help someway. 
Thanks again. 
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Hi everyone,
Could anyone show me some approaches for detecting and extracting wideband radar signals in ELINT systems? The receiver bandwidth is about 500 MHz.
I am currently following the time-frequency (T-F) analysis approach. However, I don't know which T-F technique is the most efficient one for this application?
So, could anyone help me in narrowing down the research?
Many thanks.
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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
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I need more information about Gaussian random variable(X) in pathloss formula in page 3 and 3-2 section in attached paper ( "iM-SIMPLE: iMproved stable increased-throughput multi-hop link efficient routing protocol for Wireless Body Area Networks")
I need range of values of  Gaussian random variable Or anything that helps to simulate more...
Thanks
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Its a random variable. You can generate it like this: 
X_dB = sigma*randn(1)
Every time you call this function, you will have a random value generated.
HTH
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Can any one suggest application of microwave absorbers in 5G communication systems?
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Main application of absorbers is isolation enhancement. They also can be used as filters and attenuators. 
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I am trying to simulate a Cognitive Radio Sensor Network using Matlab. Can anyone be of help with a code for doing this? NS-2 can also be ok.
Thank a lot and be blessed
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CRN configuring in NS-2  has more difficuties. Simulink can be tried out...
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Any suggestion/hint will be appreciated.
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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 
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Mode chart is available for Rectangular, Circular and annular ring shaped microstrip antenna. Does anybody have the mode chart for sectoral microstrip antenna/sectoral dielectric resonator antenna?
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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.
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Application is related to dielectric resonator antenna
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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.
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Dear friends
plz let me know the mathematical relation of bandwidth of optical bandpass filter(OBPF) with FWHM/Pulse width of optical gaussian regenerated pulse at OBPF output???
i will be very obliged for your help
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 Dear Mohammad.
The paper you attached in last massage states that they tuned pulse  train of 5 GHz or 10 GHz frequency. Now understand the thing. This developed system can used for any Gbps data rate input.
How look:
For example: 
The input signal is QPSK encoded to one of 4 phase positions for each "wave/cycle of any ps in the case of attcahed paper". If 2 bits can be carried per symbol. Thus:
Thus a 10 GHz carrier can carry 20 Gbps of data in ideal case. or 5 GHZ carrier can carry 10 Gbps of data in ideal. So data rate depends upon on the input signal modulated as well.
Also try to understand the concept of sentence mentioned in paper on page 1, second column line No.13 "The narrowest pulsewidth obtained for 10-Gb/s signal is around 20 ps."
Hope it may help somehow.
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Why so many of wireless gadgets operate at 2.4 GHz or 5.8 GHz? What is the reasons for choosing this specific frequencies for ISM bands?
Your answers will be highly appreciated.Thanks
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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
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Compressive Sensing is very popular technique to process sparse signal. most of the researchers applying CS technique for DVB-T/DAB or OFDM, GSM based passive radars whose bandwidth is small, whereas FM has huge bandwidth.
if CS is not suitable suggest me any other techniques.
Thank you  
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@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:
A Novel Elliptical-Cylindrical Antenna Array for Radar Applications
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 ...
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Is there any advantage offered by using a tapered microstrip line for a patch antenna instead of a regular straight one?? Will it any way help in UWB applications?
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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.
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I have generated a DMT signal on AWG (tektronix 70002A) and then used it to modulate LED(the signal is DC-biased to have voltages above LED threshold).
The signal after photo detection is captured on oscilloscope along with the back to back signal from AWG (A direct coax connection between AWG and oscilloscope).
For back-to back connection, the Sampled data from oscilloscope (25000 sample points) is compared with the input DMT signal shape. It is observed that the input DMT signal can be reconstructed by using the samples between 15227 to 16384. Fig1. Thus the start and end points are identified within the above range.
But the signal after photo-detection (Fig2.) is totally unidentifiable for the corresponding start and end points. Will the aforementioned sample points are the start and end points for the detected signal? Does the delay due to optical and coaxial lengths create significant shift in the start and end points between the signals? Any better method to identify the start and end of the DMT signal?
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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.
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trying to decide if demodulation is done in DSP itself ,instead of demodulation circuit
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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 
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I'm trying to understand the different modulation techniques for the satellite communication
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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
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Hello, please I would like to know if it is possible to re-prgramme a commercial SDR like those proposed by OUTERNET (http://outernet.is/) which are designed to receive satellite data so that the SDR receive GSM data?
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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.
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I am trying to simulate a submarine link by using advanced modulation formats such as 8- and 16-QAM. I know the required OSNR corresponding to those modulation formats, but I know nothing about the maximum launching power (per channel) needed to avoid nonlinear penalties. 
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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.
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Hi all,
I am trying to simulate a very simple wireless communication system. I am giving the description of the system below.
1. The wireless Communication system has one transmit antenna and one
     receive antenna.
2. The wireless channel is having multipath (In the simulation I have used static
     4-tap channel coefficients  just for simplicity)
3. I am adding AWGN noise at the receiver corresponding to the snr value (snr
    varries from 0 dB to 10 dB. Signal power is assumed to be 1)
4. In the receiver I am using Maximum Likelihood sequence estimation. (I am
    using comm.MLSEEqualizer object in MATLAB for implementing MLSE)
   
Now the problem is when I simulate the program, The BER graph is remaining flat between 0.1 to 0.01 even though I increase the snr to 50 dB.
I really can not understand what mistake I have done. Can someone please help me to solve this problem?
I have attached my matlab program and BER graph for your reference.
Regards,
Balaji.D
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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;
 
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I know pricing is a factor but what unique applications require PCR Strip Tubes with Attached Caps. What research application strongly requires this?
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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?
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I am curious about everybody's take on the state-of-the-art on design and classification of metamaterials.  Suppose I wish to identify a metamaterial with a specific permittivity and permeability.  Is there a cookbook procedure to identify/design that metamaterial?  Is there a way to classify various metamaterials that would aid in such a design effort?  What are the fundamental limits?  I think I am asking for a periodic table of metamaterials.
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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,
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As we all experience this that radio waves  loses its strength while transmitting through environment. That is why we have to Amplify the signal before and after processing it.Do you have any solution to improve the strength of RF Waves? 
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Have wireless repeaters just like wired ones.
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Hello,
I would like to know the heat produced by a typical Base Transceiver Station (without the heat produced by the antenna) and the classical dimensions of the equipment shelter containing it.
Thank you by advance
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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?
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I am looking for use cases of Group Communication using multicast in M2M communication. For example , group of lights being switched off or on by a single message . 
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Dear Anshul Anand,
Group-Communication has two parts:
1) Collecting data from a group.
2) Sending commands to a group.