<< Chapter < Page Chapter >> Page >

Stage three: anticipating impairments

In the third design stage, the choices are less constrained. Elements of the third stage are shown inthe lower half of the receiver schematic (the “adaptive layer” of [link] ) and include the selection of algorithms forcarrier, timing, frame synchronization, and equalizer adaptation. There are several issues to consider.

One of the primary stage three activities is algorithm selection—which performance function to use in each block.For example, should the M 6 receiver use a phase-locked loop, a Costas loop, or a decision-directed method for carrier recovery?Is a dual loop needed to provide adequate carrier tracking, or will a single loop suffice?What performance function should be used for the equalizer? Which algorithm is best for the timing recovery?Is simple correlation suitable to locate the training and marker segment?

Once the specific methods have been chosen, it is necessary to select specific variables and parameterswithin the algorithms. This is a traditional aspectof engineering design that is increasingly dominated by computer-aided design, simulation, and visualization tools.For example, error surfaces and eye diagrams can be used to compare the performance of the various algorithms in particular settings.They can be used to help determine which technique is more effective for the application at hand.

As software-aided design packages proliferate, the need to understand the computational mechanicsunderlying a particular design becomes less of a barrier. For instance, Software Receiver Design has relied exclusively on the filter design algorithms built into M atlab . But the specification of the filter (its shape,cutoff frequencies, computational complexity, and filter length) cannot be left to M atlab . The more esoteric the algorithm, the less transparent is theprocess of selecting design parameters. Thus, Software Receiver Design has devoted considerable space to the design and operation of adaptive elements.

But, even assuming that the tradeoffs associated with each of the individual components are clear, how caneverything be integrated together to succeed at a multifaceted design objective such as the M 6 receiver?

Sources of error and tradeoffs

Even when a receiver is fully operational, it may not decode every symbol precisely. There is alwaysa chance of error. Perhaps part of the error is due to a frequency mismatch, part of the error is due tonoise in the channel, part of the error is due to a nonoptimal timing offset, etc.This section (and the next) suggest a general strategy for allocating “part of” the error to each component.Then, as long as the sum of all the partial errors does not exceed the maximum allowable error, there is a goodchance that the complete receiver will work according to its specifications.

The approach is to choose a method of measuring the amount of error, for instance, the average of the squared recovery error.Each individual component can be assigned a threshold, and its parameters can be adjusted so that it does not contributemore than its share to the total error. Assuming that the accumulation of the errors from various sourcesis additive, the complete receiver will have no larger error than the concatenation of all its parts.This additivity assumption is effectively an assumption that the individual pieces of the system do not interact witheach other. If they do (or when they do), then the threshold allotments may need to be adjusted.

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
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
for teaching engĺish at school how nano technology help us
Anassong
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
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
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, Software receiver design. OpenStax CNX. Aug 13, 2013 Download for free at http://cnx.org/content/col11510/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Software receiver design' conversation and receive update notifications?

Ask