Interface Description EMII-800 Service Manual Application Information
EMII-800 V1.0 AnyDATA.NET Proprietary
Use Subject to Restrictions
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.
2.5 Soft Handoff
During the soft hand, the cell site already in the busy state and the cell site to be engaged in the call later participate in the call
conversion. The call conversion is carried out through the original call 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 cel l site
