LG LG-UD90c, Service Manual

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LG-KG90C
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The backward open loop power control is carried out in a corresponding mobile station; the mobile
station measures power received from the cell site and then, reversely increases/decreases transmit
power in order to compensate channel changes caused by the forward link path loss and terrain
characteristics in relation to the mobile station in the cell site. By doing so, all the mobile office
transmit signals in the cells are received by the cell site in the same strength.
Moreover, the backward closed loop power control used by the mobile station to control power with
the commands issued out by the cell site. The cell site receives the signal of each corresponding
mobile station and compares this with the pre-set threshold value and then, issues out power
increase/decrease commands to the corresponding mobile station every 1.25 msec (800 times per
second).
By doing so, the gain tolerance and the different radio propagation loss on the forward/backward link
are complemented.
2.3 Voice Encoder and Variable Data Speed
The bi-directional voice service having variable data speed provides voice communication which
employs voice encoder algorithm having power variable data rate between the mobile telephone cell
site and mobile station. On the other hand, the transmit voice encoder performs voice sampling and
then, creates encoded voice packets to be sent out to the receive voice encoder, whereas the receive
voice encoder demodulates the received voice packets into voice samples.
One of the two voice encoders described in the above is selected for use depending on inputted
automatic conditions and message/data; both of them utilize four-stage frames of 9600, 4800, 2400,
and 1200 bits per second. In addition, this type of variable voice encoder utilizes adaptive threshold
values when selecting required data rate. It is adjusted in accordance with the size of background
noise and the data rate is increased to high rate only when the voice of caller is inputted.
Therefore, background noise is suppressed and high-quality voice transmission is possible under the
environment experiencing serious noise. In addition, in case the caller does not talk, data transmission
rate is reduced so that the transmission is carried out in low energy. This will reduce the interference
on other CDMA signals and as a result, improve system performance (capacity, increased by about
two times).
2.4 Protecting Call Confidentiality
CDMA signals have the function of effectively protecting call confidentiality by spreading and
interleaving call information in broad bandwidth. This makes the unauthorized use of crosstalk, search
receiver, and radio very hard substantially. Also included is the encryption function on various
authentication and calls specified in IS-95 for the double protection of call confidentiality.
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