LG KD3500 Service Manual page 9

LG-KD3500
connection cell site, both cell sites, and then, new cell site. This method can minimize call
disconnection and prevent the user from detecting the hand-off.
2.6 Frequency Re-Use and Sector Segmentation
Unlike the existing analog cellular system, the CDMA system can reuse the same frequency at the
adjacent cell and accordingly, there is no need to prepare a separate frequency plan. Total
interference generated on mobile station signals received from the cell site is the sum of interference
generated from other mobile stations in the same cell site and interference generated from the mobile
station of adjacent cell site. That is, each mobile station signal generates interference in relation to the
signals of all the other mobile signals.
Total interference from all the adjacent cell sites is the ratio of interference from all the cell sites
versus total interference from other mobile stations in the same cell site (about 65%). In the case of
directional cell site, one cell normally uses a 120°sector antenna in order to divide the sector into
three. In this case, each antenna is used only for 1/3 of mobile stations in the cell site and accordingly,
interference is reduced by 1/3 on the average and the capacity that can be supported by the entire
system is increased by three times.
2.7 Soft Capacity
The subscriber capacity of CDMA system is flexible depending on the relation between the number of
users and service classes. For example, the system operator can increase the number of channels
available for use during the busy hour despite the drop in call quality. This type of function requires
40% of normal call channels in the standby mode during the handoff support, in an effort to avoid call
disconnection resulting from the lack of channels.
In addition, in the CDMA system, services and service charges are classified further into different
classes so that more transmit power can be allocated to high class service users for easier call set-up;
they can also be given higher priority of using hand-off function than the general users.
LGE
LG Electronics Inc.
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