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In order to design an effective analysis tool, we have to be familiar with the effects of all the parameters we make available (processing gain, sequence length, SNR of channel, number of users, degree of generator polynomial). We tested our model and concluded our results were consistent with what we would expect from a CDMA system. The following are some relationships between some parameters and the bit rate error we found especially interesting.

Generator polynomial vs number of users: For an polynomial of order x, the number of users must be less than 2x in order to minimize bit error ratio. For any number of users N, the minimum order polynomial that corresponds to the number of users>N must be used in order to minimize error.

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Number of users vs number of errors: As the number of users in a system increases, the bit error rate increases as well. Modulation sequences are assigned to each user by taking one PN sequence with a long period and assigning users delayed versions of the sequence. Increasing users will cause each user's sequence to be less orthogonal with the rest of the users, resulting in more errors at the receiving end.

Processing Gain vs number of errors: The processor gain (also referred to as spreading factor) is the ratio of the bandwidth of the pseudo-random code to the bandwidth of our desired signal. The processing gain is also the number of "chips" used to transmit a single simple. A greater the processing gain results in fewer errors in our received signal. However, in practical applications, processing gain is limited by the available bandwidth. We plotted the effect of different processing gains against the bit error rate to observe the trade off between error rate and processing gain. This plot is shown below:

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SNR vs number of users: In our model, SNR specifies the ratio of signal power to noise power in the additive white Gaussian noise channel. In a communication channel, we would like to have a high SNR. For the majority of our simulation, we set the SNR to 0(dB) to simulate a worst case scenario, where the power of the signal and the power of noise are equal. However, for a better understanding, we will show some of the effects of the SNR on few and multiple users.

First, we wanted to how SNR affected the bit error rate if the system had a small number of users (<40). Choosing 30 users for our simulation, we saw that SNR had a significant effect on bit error rate. As the SNR increases (e.x. from -5 to 5) we can see a close to quadratic relationship between the SNR and the number of errors.

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We chose to include 150 users in our system to demonstrate how SNR affected bit error rate for a large number of uers. We observe that the SNR seems to have no effect on the bit error rate. Overall, the bit error rate is high for all SNR values. When there are many users, the SNR of the channel becomes less important because the waveforms transmitted by other users look like noise. Even with a high SNR, the channel will appear noisy because of the other users. Due to the randomness of the channel the BER varies by +/- 0.5%

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Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Elec 301 projects fall 2011. OpenStax CNX. Jun 18, 2012 Download for free at http://cnx.org/content/col11431/1.1
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