Service Manual

LGP-2300/2310W
LG Information & Communications, Ltd.
- 6 -
avoided. Moreover, space diversity (also called path diversity) can be realized with the following three types of
methods.
First, it can be obtained by the duplication of cell site receive antenna. Second, it can be obtained through the
use of multi-signal processing device that receives a transmit signal having each different transmission delay
time and then, combines them. Third, it can be obtained through the multiple cell site connection (Soft Handoff)
that connects the mobile station with more than two cell sites at the same time.
2.2 Power Control
The CDMA system utilizes the forward (from a base station to mobile stations) and backward (from the mobile
station to the base station) power control in order to increase the call processing capacity and obtain high-quality
calls. In case the originating signals of mobile stations are received by the cell site in the minimum call quality
level (signal to interference) through the use of transmit power control on all the mobile stations, the system
capacity can be maximized.If the signal power of mobile station is received too strong, the performance of that
mobile station is improved. However, because of this, the interference on other mobile stations using the same
channel is increased and accordingly, the call quality of other subscribers is reduced unless the maximum
accommodation capacity is reduced.
In the CDMA PCS system, forward power control, backward open loop power control, and closed loop power
control methods are used. The forward power control is carried out in the cell site to reduce the transmit power
on mobile stations less affected by the multi-path fading and shadow phenomenon and the interference of other
cell sites when the mobile station is not engaged in the call or is relatively nearer to the corresponding cell site.
This is also used to provide additional power to mobile stations having high call error rates, located in bad
reception areas or far away from the cell site.
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 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 is 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 1.25msec (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