Science topic

# Wireless Computing - Science topic

Explore the latest questions and answers in Wireless Computing, and find Wireless Computing experts.
Questions related to Wireless Computing
• asked a question related to Wireless Computing
Question
Can you tell me the bands allotted for 5G systems
Currently, the FCC is actioning spectrum in the 27.5 GHz to 28.35 GHz, 24.25 GHz to 24.45 GHz, and 24.75 GHz 25.25 GHz, range for millimeter-wave 5G use. The FCC may also be considering opening 3.7 GHz to 4.2 GHz mid-band frequencies for 5G, and may also be considering opening 4.9 GHz public safety bands for 5G access.
• asked a question related to Wireless Computing
Question
Frameworks such as Apache Storm, Flink, Heron and Spark were developed to run on clusters or cloud. These such kinds of infrastructures do not have memory, CPU and bandwidth limitations. In contrast, computing resources at the network edge are constrained regarding their capabilities. I am aware of the Apache Edgent and Nifi frameworks. However, they were conceived to run locally on a single computing resource. If you want to run them in a distributed infrastructure, you might create your own stack of components (broker + framework).
Himadri Nath Saha, it seems to be a fascinating motivation scenario. The investments and the continuous growth of streaming games have imposed new requirements of response time (i.e., ultra-low latency). I am looking for DSP systems where latency-sensitive applications can be easily deployed on geo-distributed constrained resources avoiding creating a multi-tier of components.
• asked a question related to Wireless Computing
Question
I was going through mac protocols and wondering what will be a suitable MAC protocol for UAV swarm while conducting a mission.
Any idea?
Dear Anik,
I suggest you to see links and attached files on topic.
Paper Title (use style: paper title) - laccei
Survey on Unmanned Aerial Vehicle Networks: A Cyber ... - arXiv
Survey of Important Issues in UAV Communications Networks - arXiv
Best regards
• asked a question related to Wireless Computing
Question
As we know that, throughput is amount of transferred data for a specific time. I want to fix data size and make time variable. The definition will be "The amount of time required to transfer a specific amount of data". What is the term for this?
Dear Anik Islam Abhi,
this is "transfer / transmission time". I would use the following terms:
Transmission over a data link: transmission time; packet / data transmission time; (mean) packet / data transmission time
(mean => variable packet / data length)
When transmission over multiple data links (delays in nodes) I would use the terms: transfer time; packet/data transfer time; (mean) packet/data transfer time
Best regards
• asked a question related to Wireless Computing
Question
Any differences between spectrum access protocols and medium access protocols
I think spectrum access protocol is a special case of medium access protocol. Medium access protocol can be accomplished also by time division multiple accessing, code division multiple accessing, space division multiple accessing and frequency division multiple accessing which is spectrum access protocol.
Best wishes
• asked a question related to Wireless Computing
Question
I am trying to simulate the issue of energy efficiency in 5G using Discrete Event Simulation (DES). I am struggling to find a way how to abstract the issue of resources allocation. How can I transfer the issue into code? I am doing the simulation using JAVA language. Is there anyone have an idea how can I do that, please?
Note:
The research based on this paper " Energy-Efficient Power Control: A Look at 5G Wireless Technologies "
Solar Powered Cellular Networks
[1] A. Jahid, A. B. Shams, and M. F. Hossain, "PV Powered CoMP based Green Cellular Networks with Standby Grid Supply." International Journal of Photoenergy 2017(8) · February 2017
[2] A. Jahid, A. B. Shams, and M. F. Hossain, "Energy Efficiency of JT CoMP Based Green Powered LTE-A Cellular Networks." International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET 2017), Chennai, India - March 2017.
[3] A. B. Shams, A. Jahid, and M. F. Hossain, "A CoMP based LTE-A simulator for Green Communications." International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET 2017), Chennai, India - March 2017.
[4] A. Jahid, A. B. Shams, and M. F. Hossain, "Energy Cooperation among BS with Hybrid Power Supply for DPS CoMP Based Cellular Networks." 2nd International Conference on Electrical, Computer & Telecommunication Engineering (ICECTE), Rajshahi University of Engineering & Technology (RUET), Bangladesh, December 2016.
• asked a question related to Wireless Computing
Question
we have an architecture consist a three tier: tier 1 consist terminal nodes, tier 2 consist fog nodes, tier 3 consist cloud server . We have given two equation, one is the service delay in fog and the other is the service delay in cloud. In addition, we have given some parameters that we should use to calculate these equations. you can find the equations is attached file. the following is the given parameters:
In the system, the number of fog node=10, which connected to a single cloud service provider.
The terminal node are assumed to be uniformly distributed among the virtual cluster VC.
Data generation rate from each terminal node being 1 packet/s.
Length of each data packet is taken as 65,536 and bytes and the machine instruction size is assumed to be 64 bits.
Processing speed of the devices at the fog computing tier= 1256 MIPS.
Processing speed of the devices at the cloud computing tier= 124,850 MIPS.
Please help me using these parameters to calculate the two equations. I'm not able to find the relation between the required parameters to calculate the equations and the given ones!.
• asked a question related to Wireless Computing
Question
I am researching throughput of random access with capture.
I am wondering throughput of S-ALOHA considering frequency  reuse factor?
In my opinion, the throughput becomes FG exp(-FG), where F is frequency reuse factor and G is transmission attempt per unit time. From that equation, the maximum throughput is not changed even when F is changed.
However, i thought if the freq. reuse factor increases, the max. throughput decreases.
Does anyone have any idea for get throughput of S-ALOHA considering frequency reuse factor?
Dear Choi,
You can make a survey on previous research articles related to S-ALOHA and review CDM-based results and discussion.
• asked a question related to Wireless Computing
Question
Most common low-cost Bluetooth modules used in micro-controller based projects are limited to around 1 Mbps thru Serial Port Profile (SPP). In addition, while the modules can transfer short data packets at all baud rates, they halt or fail completely when trying to achieve sustained high data rates. How to successfully transfer/stream data at all available baud rates for prolonged period of time? Are there any other feasible options for use i.e. different profile of Bluetooth in this case?
The standard data rate of 1 Mbps and ( cough! ) "enhanced" data rate of 2Mbps is pretty much what you have to work with.  The high speed devices are still fairly expensive and uncommon, as you mention, those get you to 25Mbps.    That is the native symbol rate.  So not much to "fix" there.
As for Bluetooth cutting out?  That's not a feature of Bluetooth, it could be a number of factors specific to your use case: drivers, RF environment, the transport methods, the computing devices.  I consider that not to be an intrinsic Bluetooth issue.   For synchronous transfer near maximum throughput, you do not have an throughput to retry lost block because the aggregate of valid and retried data exceeds the available throughput.   So you cannot run at 1Mbps, as there is no room for errors.   The strategy is to reduce the bulk of the data, leaving ample headroom.
For asynchronous data transmission, you need s TCP-like transport mechanism.  Heck, even things like Z-Modem does a block integrity check and re-transmission, is appropriate.
Another factor is the RF space.   Bluetooth devices come in 3 distance ranges - in some cases the only difference is the type of antenna in the device.   The maximum range of 100 meters is achievable.   Its also possible to attach yagi antennas to bluetooth interfaces dramatically extend the range.   I have, myself, sent bluetooth over 500 meters with very cheap yagis.  You can even do this with low power devices.  More gain is always better,
The point of the above paragraph is that if you improve the gain of the antennas, you can have much more immunity to ambient RF.   Improving the SNR will help increase the throughout.
Hope that helps.
• asked a question related to Wireless Computing
Question
Does two eNBs in LTE networks communicate using wireless medium or wired medium?
Ok thanks a lot
• asked a question related to Wireless Computing
Question
If graph G(V, E) represents femtocell topology where vertices V and edge set E show femtocell and their interfering relation respectively. We may say, there is an edge between two femtocells if their distance is less than 2R. Considering this scenario of the femtocell, can we model the femtocell as a unit disk graph?
I would answer yes, if the femtocell is being used outdoors, and you are looking for seamless coverage between femtocells. But frequently, femtocells are used to improve indoor coverage, without offloading to WiFi. So in this case, the femtocell coverage is more or less confined to inside the building.
(Parenthetical editorial comment: While in principle, femtocells are the natural progression of the cellular model, to reuse spectrum even more effectively, some of the interest in femtocells is tied to LTE-U. This is where the cellular service gets to grab free, unlicensed spectrum, the same spectrum used by WiFi, to sell revenue-making cellular service. If you offload to WiFi, instead, the cell company does not make revenue from those sessions.)
• asked a question related to Wireless Computing
Question
Dear researchers?
I am a bit confuse about, when we do scheduling algorithm high proirity for something, the scheduling happened before data buffer or after?
I am wondering, if the data buffered and and buffer size is full, is that able to replace packets in the buffer with new data comes with high priorty?
Thanks
No, when the packets are in the buffer, you should be able to treat them differently based on different criteria, e.g., priority. It depends on the implementation.
• asked a question related to Wireless Computing
Question
I found some scholars clarified that the relationship between the Shannon transform and Stieltjes transform with
\frac{\gamma}{\log e}\frac{d}{d\gamma}\mathcal{V}_N(\gamma) = 1 - \frac{1}{\gamma}\mathcal{S}_N(-\frac{1}{\gamma})
However, other scholars claimed that this equality was modified as
\mathcal{V}_N(x) = \frac{1}{N}\log \det (\mathbf{I}_N + \frac{1}{x}\mathbf{B}_N) = \int_{0}^{+\infty}\log (1+\frac{\lambda}{x})dF_N(\lambda) = \int_{x}^{+\infty}(\frac{1}{\omega}-\mathcal{S}_N(-\omega))d\omega
Here $\mathcal{S}_X(.)$ denotes the stieltjes transform, whereas $\mathcal{V}_X(.)$ is the shannon transform. So how can I obtain the last equation from the first equation?
***I mean, given that***
\frac{\gamma}{\log e}\frac{d}{d\gamma}\mathcal{V}_N(\gamma) = 1 - \frac{1}{\gamma}\mathcal{S}_N(-\frac{1}{\gamma})
***How can I obtain this***
\mathcal{V}_N(x) = \int_{x}^{+\infty}(\frac{1}{\omega}-\mathcal{S}_N(-\omega))d\omega
I did some calculations, but not sure that they are equal.
Try this PDF on Stieljest and related transform. If people are interested in pusuing this further, please let me know, yangbrookchen@yahoo.co.uk. I find yahoo easier to handle.
Yang
• asked a question related to Wireless Computing
Question
As there is no topology called best topology for all engineering Applications, I would like to study  different network topologies applied in different engineering field. I would like to make worth discussion to analysis different topologies with advantages and disadvantages. Can one suggest good book to study different Network Topologies and their Applications in different Engineering?
There is a huge literature on k-node connected and k-edge connected networks, network loading, network design, networks with bounded rings, etc. Try looking at past issues of the journal "Networks".
• asked a question related to Wireless Computing
Question
Expect to hear a whole lot more about Li-Fi - a wireless technology that transmits high-speed data using visible light communication (VLC) - in the coming months. With scientists achieving speeds of 224 gigabits per second in the lab using Li-Fi earlier this year, the potential for this technology to change everything about the way we use the Internet is huge. Now, scientists have taken Li-Fi out of the lab for the first time, trialing it in offices and industrial environments in Tallinn, Estonia, reporting that they can achieve data transmission at 1 GB per second - that's 100 times faster than current average Wi-Fi speeds.
Sure its feasible. You can achieve lots of capacity, when using optical frequencies, simply because you're so high up in the spectrum. A tiny sliver of spectrum has huge potential, because that tiny sliver can be a lot wider, in terms of Hz of bandwidth, than anything remotely feasible in the radio frequency bands.
The problem will be obstructions, though, because light won't diffract around obstacles as radio frequencies do. So range will be limited. Can't cover an entire house with just one access point, as you can with WiFi. Can't go through bad weather as you can with radio, either.
The irony in this is that modulating light, incoherent light such as that used in VLC, is really primitive stuff. Because the source is incoherent, you're limited to using either on-off keying (like Morse code) or intensity modulation (like AM radio). The huge capacity is possible regardless, but the modulation techniques are definitely early 20th century!
• asked a question related to Wireless Computing
Question
I need the codes that can enable my software to communicate with pressure sensors.
Thank you!
You need to  establish what sensor are you going to use, because you could possible find some sensor that can use some standard automation protocol, such as Hart, Modbus, Fielbus, with these information you can look for some API implementation of your field protocol. I think that there are some API of Modbus in Java ( http://stackoverflow.com/questions/4689381/need-modbus-java-library )
• asked a question related to Wireless Computing
Question
I'm doing research and need to divide the frequency range of LTE in sub-bands but I do not know the starting point and the end point of this band that I used. The experience that I am doing is the following:
Track 1 = Downlink 1920-1940 - Uplink 2110-2130 - Bandwidth 20 MHz
Track 2 = Downlink 1940-1960 - Uplink 2130-2150 - Bandwidth 20 MHz
Track 3 = Downlink 1960-1980 - Uplink 2150-2170 - Bandwidth 20 MHz
which band can I go to? If I try to 10MHz bandwidth,  can there be more interference?
Can anyone can help me? Thank you very much.
Hi Fabio,
Please look at the LTE 36.141 specification document
Here, under section 5.7, you see the LTE carrier frequency assignment
Also, what do you mean "can there be more interference?" ?
Regards
Ramesh
• asked a question related to Wireless Computing
Question
In slowly varying environments, AR-models can be used for channel tracking. But in highly non-stationary environments, such as vehicular channels, these models do not apply. What are the alternative algorithms used for vehicular channel tracking and prediction? Are there any good references for that?
Thank you,
This is the best reference for that:
• asked a question related to Wireless Computing
Question
The question may be stupid but it really confuses me for a long time.
I read a lot of papers in wireless sensor network. Many researchers model their problems into the form of ILP. However, ILP is NP-Complete so it is not efficient for solving a problem.
So why people write their problems into the form of ILP? Do they do that to make their problem clear to see and easy to understand? Or do I make some mistakes understanding the relations between ILP and NPC?
I am really appreciated that you can help me to solve this question.
The previous answer is great and gives some good examples. Another "reason" for ILP that I might add is that it is often the most obvious and most straightforward way to represent the selection of discrete alternatives (for example a binary variable X_ j is 1 or 0). I'd even ask what would you do instead? Perhaps represent X_ j as a real number bounded by 1 and zero (relaxation of the problem). This is a strategy for attacking the case, but you would have to agree that fractional solutions are not representative of the real problem that we have set. (This occurs in facility location, portfolio selection, and many other areas.) So the problem might require branch and bound or other implicit enumeration schemes to finish off the selection of only integer solutions.
I think that if you want to understand some of the beauty (and difficulty) of ILP check out the knapsack problem. Almost as simple as you could imagine, and yet there are integer variables with real meaning and significance for this model. While this is "difficult" it has not stopped clever algorithmic approaches that improve over the most obvious greedy heuristic.
• asked a question related to Wireless Computing
Question
I want to implement a Chebsyhev fourth order transfer function. I don't want the impedance values and scaling procedure. What I want is the procedure to implement any fourth or higher order transfer function using passive elements only.
Dear Amr,
I would propose the following procedure:
- From the filter requirement, determine the filter function and the order of the filter.
for example as in your question, Chebychev, fourth order.
Then you can get H(s) of the filter as H(s) = 1/ D(s),
where the denominator polynomial coefficients are known
Then you propose the circuit for the implementation, which in your case is a passive network composed of L and C elements.. Then you derive the transfer characteristics of this circuit by means of circuit analysis, say Hi(s), putting it in the form of H(s).
By equating the corresponding coefficients of of the denominator of both responses we get a number of algebraic equations equals the number of unknowns which are the element values of the circuit.
You can solve these equations using Matlab.
The source and load resistances may be Tartary chosen. eg RS=0 and RL=infinity.
• asked a question related to Wireless Computing
Question
In wireless mesh networks, how do I decide the packet transmission with improved throughput under power constraint?
you can use fazzy logic or automata  for select best decide  for your network ;
for example fuzzy help you consider several parameters and select best decide base this parameters
or you can use automata for determinat state probability for next dicide
best regard ..
• asked a question related to Wireless Computing
Question
i want to run parallel cloudlet or bulk data in cloud computing which is the best energy efficient technique for this available in cloud computing
• asked a question related to Wireless Computing
Question
token bucket gives token to each node to get connected in network, to transfer data .
when some node need to communicate in network (emergency case), where its stacked in network in other position based on token.
i need any alternate used to consider emergency case , to rearrange the token , or suggest me with alternate algorithm which consumes less energy in energy limited environment like polar regions.
Each packet should have a field called Priority and composed of 3 bits. So, priority varies from 0 to 7 (respectivelly, from 000 to 111, in binary). Hence, the receiver node will compare its own priority to the received packet, such that the highest priority is 0.
If its priority is higer than the one of the received packet, then, it can ignore the received packet and send its own packet.
So, in emergency case, the node wishing to send must set its priority field to 0.
Of course, if you want to increase the priority levels according to the network density, you can add of PRIORITY field having more than 3 bits.
Hope this will help.
• asked a question related to Wireless Computing
Question
Could you please help me how i can generate an independent sample fast fading from Rayleigh distribution (NLOS) and the Rician distribution (LOS), I can the correlation in time due to mobility and also the correlation in frequency due to the multipath delay profile. i just need to get a statistically reasonable fading model.
and some information about Jakes model.
Thank you
You can use the attached MATLAB which is supported by the ns-3 developers for simulating small scale fading in LTE according to the 3GPP documentations:https://www.nsnam.org/docs/release/3.21/models/html/lte-user.html
• asked a question related to Wireless Computing
Question
Hi every body.
as you know, some papers set a packet size and a time slot length in the simulations to calculate the packet delivery rate. but didnt describe the scenario in details. the question is : does a  complete data packet is transmitted in a single time slot ? or multiple slots are needed to transmit a packet.
The size of packet depends on the application as well as the protocol. Time slot based scheduling is taken care by MAC layer and not the routing protocol. Routing protocols determine the packet structure for data as well as route maintenance. number of packets at source network layer and receiver network layer can be counted to determine packet delivery
• asked a question related to Wireless Computing
Question
What kind of path loss model will be considered for mm Wave communication
• asked a question related to Wireless Computing
Question
I have 2 IEEE 802.11e network scenarios and i need to know the difference between them. One is a network where we assume stations transmit only one traffic type, say 4 stations and one transmits video, another transmits voice, another data, like that and the second scenario is where each station transmits all 3 or 4 traffic types. Question is:
1. How is throughput analysed/affected in 2nd scenario considering each STA has multiple EDCAF.
2. How do i analyse transmission probability on the channel?
Or maybe you can use multiple instances of iPerf to mimic different traffic types. Suppose that in Scenario 2 you create an iPerf instance in a station using UDP and certain bandwidth; another instance using TCP at another bandwidth and so on for as many Access Categories/Traffic Types as you want. This way you get the aggregate throughput from each iPerf instance and compare it to those achieved in Scenario 1 using the same tools (but instead of instances you run a single iPerf process in each station, of course).
• asked a question related to Wireless Computing
Question
if we have 2 devices like walky talky and mobile phone, for a particular situation, is it possible the mobile to use the channel allocated to walky talky to send data/information ?
In principle, why not?
Walkie talkies typically operate either in the citizens band, high HF, or in the VHF spectrum. Whereas mobile phones operate at high UHF, above 700 MHz to the GHz ranges. So that's one problem. The antenna requirements, for small hand held devices with no external antenna, would make use walkie talkie frequencies quite inefficient.
But mobile phones are already multiband devices, after all, so why not (in principle)? Mobile phones already detect frequencies available at any given location, and pick the best one to use. So I don't think there's anything intrinsically impossible about designing a "mobile phone" to use other frequency bands than those allocated to cellular. However, the spectrum allocation authority in your country would most likely not allow this.
• asked a question related to Wireless Computing
Question
Say I have some device which can store data but does not have any capability to send/receive, but my second device from far away places like, say 1km or so should be able to receive the data from the device wirelessly.
I mean every technology like Bluetooth, satellite, wifi etc require both the device able to send and receive. But I am in find of a system mentioned below
Does anybody know how Balise works and its internal mechanism ?
Yes zigbee is one way to go as mentioned
• asked a question related to Wireless Computing
Question
I would like to use a wifi protocol for image transmission. I am planning to use 802.11p or ac. I would like to know the important differences between these two so that I can finalize a suitable one for my outdoor application. Thanks in advance.
Thank you Jose and Alessandro.
• asked a question related to Wireless Computing
Question
I am working in WSN. While my implementaion, I am facing the lifetime of the sensor node. Any one help me to overcome this.
Dear P. Prakasam,
Lifetime of the sensors in WSN be improved can be improved by two ways:
1. By saving its transmission energy and 2. By saving its processing energy
(With the efficient use of aggregation and routing protocols and data compression techniques may also be used to reduce the size of data, etc.)
• asked a question related to Wireless Computing
Question
I need to analyse their performance in terms of job completion time and if possible  potential interference of wireless links.
You can use NS3, MATLAB (Simulink) or OPNet.
• asked a question related to Wireless Computing
Question
How to determine the weight of a link in wireless mesh network and the criteria behind ??
@diamel teguig sir thnks for your view on it..
@muhammad naveed-sir How to determine the weight of a link in wireless mesh network and what are the criteria which kept in mind before allotting or assigning  weights to it..
• asked a question related to Wireless Computing
Question
We work on cross platform mobile development. We need to compare our work to others. What are the available programs (open source or evaluation version) of cross platform mobile development? Is there any metrics that can be used for comparison other than percentage of accepted lines of code?
I used Mosync "http://www.mosync.com" for building couple of applications and you can simply use JQuery mobile within Mosync to create whatever applicaitons you would like to create. You can use any webservice and call it with ajax from your JQMobile pages to interact with your server. So all what you need to do is:
1. Learn JQMobile
2. Learn Ajax calls
3. Have a web service that controls and interacts with your database and code. (I personally use web2py framework as a server and write my controllers with python).
4. Create a hybrid application or an HTML5 application inside mosync and start adding JQMobile pages inside it and call your web services using ajax.
5. Build to any platform.
6. Test your project either on the web, phone emulator or connect your phone to your computer and test it.
• asked a question related to Wireless Computing
Question
I want to find the position of slave device with respect to master device by using bluetooth? consider a scenario in which on master device called laptop having bluetooth and another slave device cell phone also having bluetooth facility. I want to find the distance between these two devices along with the direction of slave with respect to the master i.e. laptop.can is it possible?
My dear @Shrikant, the following US patent Hybrid bluetooth/RFID based real time location tracking US 6717516 B2 may be the solution to your need!
• asked a question related to Wireless Computing
Question
How could be the precoder matrix be designed for spatial modulation transmitter and receiver.
We can also use Geometric Mean Decomposition (GMD) for  precoding. The GMD composite the channel into subchannels with equal SNR.
• asked a question related to Wireless Computing
Question
.
WMAN enables the users to create wireless connections between multiple locations within a metropolitan area. It connects the multiple office buildings in a city or on a university campus. WMAN does not require high cost of placing fiber or copper cabling and leasing lines. Further, WMAN can work as backups for wired networks.
WMAN uses either infrared light or radio waves to transfer data. WMAN is supported with three different standards.
• 802.16
• HiperMAN
• HiperACCESS
In addition, Back haul and last mile are two fundamental types of WMAN.
The advantage of MWAN for implementing metropolitan area network is its beauty due to less cost than fiber-based Local area networks (LANs) due to several reasons. It is easy to use, extend, exchange or back up prevailing fiber infrastructure within hours, preserving time and money on personnel. It also eradicates leased line costs, fiber trenching cost in laying fiber. Another noteworthy benefit of implementing the WMAN is to bridge the “digital divide” by affording linking communities that have not had the access to wireless internet connections and LAN. Implementing of WMAN allows companies, government agencies, etc. to swiftly increase their internet service into new marketplaces for generating better revenues. From other side, WMAN has security issue because it consists of large area and having problem being hacked the information. A WMAN is merely a bigger WAN track, and thus provides the larger chance for a hacker.
• asked a question related to Wireless Computing
Question
OFDM was selected by many standards for wireless mobile networks like WIMAX and LTE. OFDM has advantages of simple receiver with the ability to combat ISI. It can also provide more capacity because of its orthogonal narrowband subcarriers. I like that we highlight more the advantages and disadvantages that OFDM provides compared to other modulation and multiple access techniques of the past such as WCDMA, multi carrier CDMA and TDMA techniques as well as to other techniques suggested in the literature and whether future networks will continue to rely on OFDM/OFDMA or not.
Dear dr. Ismat,
It seems that the orthogonal frequency division multiplexing and multiple accessing is the most suitable modulation technique for the wide band communication systems either wireless or wired. Compared to single carrier system, it has many advantages especially the inter symbol interference in multipath channels. OFMD has more immunity against multipath effects. OFDM is more easier to implement and equalize. It is also more robust against deep frequency selective fading. Compared to FDM it is more band width efficient since the subcarriers are allowed to overlap as they are orthogonal by making their frequency is an integral multiple of the inverse of the symbol time.. Every carrier is M-QAM modulated according to the available signal to noise ratio. So, the bandwidth efficiency can be increased for higher signal to noise ratio.Consequently, one can make full use of the channel conditions to increase the bandwidth efficiency and increase the bit rate of the communication system.
It out performs the wideband code divination multiplex accessing as it has a higher bandwidth efficiency and easier to control than the spread spectrum in WCDMA. Time division multiplexing is used with single carrier systems which outlined at the beginning of the comment.
The OFDM sums many advantages against the other modulation and multiple accessing techniques more than its drawbacks.
The drawbacks are the high peak to average power ratio which makes the power amplifier expensive and more power hungry. The other drawback is the intercarrier interference. But there are powerful techniques to mitigate these draw backs.
In the foreseen future, OFDM may remain the most preferable modulation and multiple accessing technique. It is even the recommended modulation technique for the ultrawideband UWB communication systems.
• asked a question related to Wireless Computing
Question
Should it be implemented at the card's driver file? Or at the OS kernel? Which files should be modified?
Could you please provide the necessary steps?
• asked a question related to Wireless Computing
Question
I want to simulate 802.11n frame aggregation. Can we simulate this using NS2. Is there any kind of patching required for the same.
Please tell me how to do this.
Thanks & Regards,
You should uses NS3, it supports b/g/e/n/a (n only siso)
• asked a question related to Wireless Computing
Question
There are a lot of tools used for these purposes. I would like to know the most important and widely used tools currently.
Thanks for your answer. My question was more inclined towards Wired and Wireless LAN (Wi-Fi) Site Surveying, in computers.
• asked a question related to Wireless Computing
Question
Thanks.
You can try to implement
COngestion Detection and Avoidance (CODA) approach described by Wan et al.
I am not sure about how to exactly implement in opnet. You need check the opnet developer manual specifying that how to incorporate your own protocols or something like that.
Another way is to use Castalia network simulatior which is specifically designed for WSN, while openet is general purpose and also not free.
• asked a question related to Wireless Computing
Question