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Within a single cell, the transmitter implements multiple users that send messages by sequencing them in time.In TDMA, where the signal intended for each user is transmitted during a designated time slot, all users employ the same band of frequencies.The frame structure for the B 3 I G TDMA is shown in [link] . This may be contrasted with the FDMA situation where users each employtheir own frequency range, as was discussed in [link] .

The Time Division Multiple Access (TDMA) frame structure used in the B^3IG. The indicated sizes are valid for the 8-bit ASCII encoding.
The Time Division Multiple Access (TDMA) frame structure used in the B 3 I G . The indicated sizes are valid for the 8-bit ASCII encoding.

Typically, adjacent cells transmit on different frequencies, though frequencies may be reused in cells that are sufficiently far away.Adjacent cells may use frequencies that are close to each other – and may even overlap slightly due to relaxed spectral masks.Consequently, it is not unreasonable to expect some interference from adjacent cells. B 3 I G makes it easy to study the effects of this kind of interference.

In Code Division Multiple Access (CDMA), each user is assigned a code which is mutually orthogonal to all of the other users. All users transmit at the same time and in the same frequency range, and the decoding relies on the orthogonality of the codes. B 3 I G does not currently implement a CDMA protocol.

Constructing the received signal

The B 3 I G Transmitter (i.e., the base station) simulates K simultaneous users using TDMA. Each receiver (i.e., each mobile device in [link] ) retains and decodes only its intended portion of the signal. For single-user operation, K = 1 .

Each of the three blocks in [link] is itself built from several components that are familiar from previous chapters. The system that generatesthe analog received signal (i.e. the actual transmitter and channel) is shown in block diagram form in [link] . This is, of course, the magical M 6 Transmitter from [link] . When the signal arrives at the front end of the receiver,it is transformed into a sampled IF signal as in [link] .

The front end of the B^3IG transmission system filters for the desired frequency range, adjusts the gain, and modulates to the IF frequency. After a final filtering, the samples give the received signal r.
The front end of the B 3 I G transmission system filters for the desired frequency range, adjusts the gain, and modulatesto the IF frequency. After a final filtering, the samples give the received signal r .

The original message in [link] is a character string of English text. Each character is mapped into asequence of 4-PAM symbols. The mappings may be made using the M atlab function letters2pam.m , which converts each letter to an eight-bit binary string, and hence tofour 4-PAM symbols as in [link] . Alternatively, the mappings may be made with the more terse text2bin.m , which converts each letter to a 7-bit binary string, thus assigning seven 4-PAM symbols to every pair of letters.This mapping is familiar from [link] .

In order to decode the message at the receiver, the recovered symbols must be properly grouped, thestart of each group must be located, and the desired user data must be extracted. To aid this TDMA frame synchronization, apreamble is inserted in the symbol stream at the start of every frame. The preamble is a short text message that starts each frameand it is assumed to be known at the receiver. Like the message, it is encoded in 4-PAM symbols.The unknown messages for each user are placed in sequence after the preamble, as in [link] .

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Software receiver design. OpenStax CNX. Aug 13, 2013 Download for free at http://cnx.org/content/col11510/1.3
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