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Advanced Television Systems Committee(ATSC) standardsare a set
of standards
developed by theAdvanced Television Systems Committeefordigital
televisiontransmission
over terrestrial, cable, and satellite networks.
ATSC 3. will provide even more services to the viewer and
increased bandwidth efficiency
and compression performance, which re!"ires breaking backwards
compatibility with the
c"rrent version. ATSC 3. is e#pected to emerge within the ne#t
decade. $%&'
n information theory, a lowdensity paritycheck (LDPC) code is a
linear error correcting
code, a method of transmitting a message over a noisy
transmission channel.
An LDPCis constr"cted "sing a sparse bipartite graph.
Hierarchical modulation, also called layered modulation, is one
of the signal
processingtechni!"es form"ltiple#ingandmod"latingm"ltiple data
streams into one single
symbol stream, where baselayer symbols and enhancementlayer
symbols are
synchrono"sly overplayed before transmission.
*se of cyclic prefixis a key element of enabling the +- signal
to operate reliably.The cyclic prefixacts as a b"ffer region or
g"ard interval to protect the +- signals
from intersymbol interference.
Orthogonal frequencydivision multiplexing(O!D") is a method of
encoding digital data
on m"ltiple carrier fre!"encies. +- has developed into a pop"lar
scheme
for widebanddigital comm"nication, "sed in applications s"ch as
digital television and a"dio
broadcasting, -S/nternet access, wireless networks,powerline
networks, and &0mobile
comm"nications.
+- is a fre!"encydivision m"ltiple#ing(-) scheme "sed as a
digital m"lti
carrier mod"lationmethod. A large n"mber of closely spaced
orthogonals"bcarrier
signalsare "sed to carry data$%'on severalparalleldata streams
or channels. 1ach s"b
carrier is mod"lated with a conventional mod"lation scheme (s"ch
as !"adrat"re amplit"de
mod"lationorphaseshift keying) at a low symbol rate, maintaining
total data rates similar to
conventional single-carriermod"lation schemes in the same
bandwidth.
The primary advantage of +- over singlecarrier schemes is its
ability to cope with
severechannelconditions (for e#ample,atten"ationof high
fre!"encies in a long copper
wire, narrowbandinterferenceand fre!"encyselectivefadingd"e
tom"ltipath) witho"tcomple# e!"ali2ation filters. Channel
e!"ali2ationis simplified beca"se +- may be
viewed as "sing many slowly mod"lated narrowbandsignals rather
than one rapidly
mod"lated widebandsignal. The low symbol rate makes the "se of
ag"ard intervalbetween
symbols affordable, making it possible to eliminate intersymbol
interference(S) and "tili2e
echoes and timespreading (on analog"e T these are visible as
ghostingand bl"rring,
respectively) to achieve adiversity gain, i.e. a signaltonoise
ratioimprovement. This
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