User Guide

PAMS
Technical Documentation
NHP–4
System Overview
Page 3–30
Issue 1 04/99
Master (System) start time is shown on both circles but the mobile does not know
System start time until it decodes the Sync channel. Remember that both the Pilot
and Sync channels do not contain a Long Code so they both repeat at the same rate
of 26.67 msec. The mobile starts decoding the Synch channel information of the
strongest cell site when it acquires that cell’s Pilot channel. The mobile does not
decode Sync channels of the weaker cell sites received during the search.
Sync Channel
The Sync Channel has a lot of important information, some of which is listed below..
Pilot PN offset of base station: The Pilot PN offset is the base station’s time slot
number.
System Time
: Is the MASTER start time.
Local Time Offset from System Time:
Long Code State: This is very important! The state of the “Long Code” 320
milliseconds in the future is sent. The CDMA Long Code was started in Jan 1, 1980
and has been running ever since. Remember this code only repeats its self once
every 41 days, so it would take too long to search through the entire code. Not only
does the CDMA cellular phone need to know when the present long code sequence
started, it also needs to know where the code is “right now”. That’s what is meant
by “Code State”.
SID, NID of Cellular System: System Identification, Network Identification
Paging Channel Data Rate: 0, 9600: 1, 4800
Base Station Protocol Revision: 1 – IS95; 2 – IS95A; 3 – TSB74
Leap Seconds From Start of System Time: This is the delay from system time for
the clock based on the “slot cycle index”.
Daylight Savings Time Flag: Self explanatory.
Paging Channel
Once the mobile has system time and long code state, the Paging channel
information can be read. If required the mobile will register with the base station at
this time. The phone must register if it is in a slotted mode. When a phone is in a
slotted mode it goes to sleep for a few seconds periodically and then wakes up to
check for a page. The sleep period based on the “slot cycle Index” must be known
to the base station or the phone could be paged while asleep and miss the page.
The following is a partial list of Paging channel information:
System Parameters Message: This message provides the mobile with
information, such as network, system and base station identification numbers, the
number of paging channels supported, registration information, and the soft
hand–off thresholds.
Access Parameters Message: When a mobile calls the base station it uses a
channel called the “Access Channel”. This message gives the mobile information
that dictates the behavior of access probes when a CDMA mobile initiates a call.
Neighbor List Message: The neighbor list gives the mobile the PN Offsets of
surrounding cell sites that may become likely candidates for soft hand–offs.