<< Chapter < Page Chapter >> Page >

Figure 1 highlights three major performance categories in terms of bit-error probability P B size 12{P rSub { size 8{B} } } {} versus E b / N 0 size 12{E rSub { size 8{b} } /N rSub { size 8{0} } } {}

The leftmost exponentially shaped curve highlights the performance that can be expected when using any nominal modulation scheme in AWGN interference. Observe that at a reasonable E b / N 0 size 12{ {E rSub { size 8{b} } } slash {N rSub { size 8{0} } } } {} level, good performance can be expected.

The middle curve, referred to as the Rayleigh limit , shows the performance degradation resulting from a loss in E b / N 0 size 12{ {E rSub { size 8{b} } } slash {N rSub { size 8{0} } } } {} that is characteristic of flat fading or slow fading when there is no line-of-sight signal component present. The curve is a function of the reciprocal of E b / N 0 size 12{ {E rSub { size 8{b} } } slash {N rSub { size 8{0} } } } {} , so for practical values of E b / N 0 size 12{ {E rSub { size 8{b} } } slash {N rSub { size 8{0} } } } {} , performance will generally be “bad.”

The curve that reaches an irreducible error-rate level, sometimes called an error floor , represents “awful” performance, where the bit-error probability can level off at values nearly equal to 0.5. This shows the severe performance degrading effects that are possible with frequency-selective fading or fast fading.

If the channel introduces signal distortion as a result of fading, the system performance can exhibit an irreducible error rate at a level higher than the desired error rate. In such cases, the only approach available for improving performance is to use some forms of mitigation to remove or reduce the signal distortion.

The mitigation method depends on whether the distortion is caused by frequency-selective fading or fast fading. Once the signal distortion has been mitigated, the P B size 12{P rSub { size 8{B} } } {} versus E b / N 0 size 12{ {E rSub { size 8{b} } } slash {N rSub { size 8{0} } } } {} performance can transition from the “awful” category to the merely “bad” Rayleigh-limit curve.

Next, it is possible to further ameliorate the effects of fading and strive to approach AWGN system performance by using some form of diversity to provide the receiver with a collection of uncorrelated replicas of the signal, and by using a powerful error-correction code.

Figure 2 lists several mitigation techniques for combating the effects of both signal distortion and loss in SNR. The mitigation approaches to be used when designing a system should be considered in two basic steps:

1) choose the type of mitigation to reduce or remove any distortion degradation;

2) choose a diversity type that can best approach AWGN system performance.

Questions & Answers

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
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
Maciej
characteristics of micro business
Abigail
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 ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
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
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
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
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
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
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Berger describes sociologists as concerned with
Mueller Reply
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Principles of digital communications. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10805/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Principles of digital communications' conversation and receive update notifications?

Ask