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VX8610
LGE Int rnal Us Only
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2. Features and Advantages of CDMA Mobile Phone
2.1 Various Types of Diversities
Wh n mploying th narrow band modulation (30kHz band) that is th sam as th analog FM modulation syst m
us d in th xisting C llular syst m, th multi-paths of radio wav s cr at a s rious fading. How v r, in th CDMA
broadband modulation (1.25MHz band), thr typ s of div rsiti s (tim , fr qu ncy, and spac ) ar us d to r duc
s rious fading probl ms g n rat d from radio chann ls in ord r to obtain high-quality calls.
Tim div rsity can b obtain d through th us of cod int rl aving and rror corr ction cod wh r as fr qu ncy
div rsity can b obtain d by spr ading signal n rgy to wid r fr qu ncy band. Th fading r lat d to normal
fr qu ncy can aff ct th normal 200~300KHz among signal bands and accordingly, s rious ff ct can b avoid d.
Mor ov r, spac div rsity (also call d path div rsity) can b r aliz d with th following thr typ s of m thods.
First, it can b obtain d by th duplication of c ll sit r c iv ant nna. S cond, it can b obtain d through th us of
multi-signal proc ssing d vic that r c iv s a transmit signal having ach diff r nt transmission d lay tim and th n,
combin s th m. Third, it can b obtain d through th multipl c ll sit conn ction (Soft Handoff) that conn cts th
mobil station with mor than two c ll sit s at th sam tim .
2.2 Power Control
Th CDMA syst m utiliz s th forward (from a bas station to mobil stations) and backward (from th mobil
station to th bas station) pow r control in ord r to incr as th call proc ssing capacity and obtain high-quality calls.
In cas th originating signals of mobil stations ar r c iv d by th c ll sit in th minimum call quality l v l (signal
to int rf r nc ) through th us of transmit pow r control on all th mobil stations, th syst m capacity can b
maximiz d.If th signal pow r of mobil station is r c iv d too strong, th p rformanc of that mobil station is
improv d. How v r, b caus of this, th int rf r nc on oth r mobil stations using th sam chann l is incr as d
and accordingly, th call quality of oth r subscrib rs is r duc d unl ss th maximum accommodation capacity is
r duc d.
In th CDMA syst m, forward pow r control, backward op n loop pow r control, and clos d loop pow r control
m thods ar us d. Th forward pow r control is carri d out in th c ll sit to r duc th transmit pow r on mobil
stations l ss aff ct d by th multi-path fading and shadow ph nom non and th int rf r nc of oth r c ll sit s wh n
th mobil station is not ngag d in th call or is r lativ ly n ar r to th corr sponding c ll sit . This is also us d to
provid additional pow r to mobil stations having high call rror rat s, locat d in bad r c ption ar as or far away
from th c ll sit .
Th backward op n loop pow r control is carri d out in a corr sponding mobil station; th mobil station m asur s
pow r r c iv d from th c ll sit and th n, r v rs ly incr as s/d cr as s transmit pow r in ord r to comp nsat
chann l chang s caus d by th forward link path loss and t rrain charact ristics in r lation to th mobil station in th
c ll sit . By doing so, all th mobil transmit signals r c iv d by th bas station hav sam str ngth.
Mor ov r, th backward clos d loop pow r control us d by th mobil station is p rform d to control pow r using
th commands issu d out by th c ll sit . Th c ll sit r c iv s th signal of ach corr sponding mobil station and
compar s this with th pr -s t thr shold valu and th n, issu s out pow r incr as /d cr as commands to th
corr sponding mobil station v ry 1.25ms c (800 tim s p r s cond). By doing so, th gain tol ranc and th
diff r nt radio propagation loss on th forward/backward link ar compl m nt d.
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