|
|
CDMA System Time Parameters
Last updated: July 25, 2008
Overview
The CDMA system time is the time reference used by all IS-95/IS-2000 and IS-856 systems. It is synchronous to UTC time (Universal Coordinated Time) except for leap seconds and uses the same time origin as GPS (Global Positioning System) time. Access terminals (ATs) use the same system time, offset by the propagation delay from the AN to the AT.
The test set emulating an AN allows you to set the
CDMA System Time
,
Leap Seconds
and
IS856 Local Time Offset (hh.mm)
which are sent to the AT in the overhead messages (
Sync Message
and
SectorParameters Message
). The AT determines its local time based on these parameters. When the AT successfully synchronize its system time to the test set, the local time that is displayed on the AT's screen should be same as the
CDMA Local Time
displayed on the test set's
CDMA System Time Information
window.
The settable CDMA system time provides convenience to verify AT's time-based applications such as alarms, calendar, meeting scheduler, etc.
(
Lab Application Only
) The settable CDMA system time is required by multiple test sets synchronization. For details, see
Multi-unit Synchronization
.
CDMA System Time Parameters and Information
-
CDMA System Time
The CDMA System Time consists of two portions:
CDMA System Time (Date)
and
CDMA System Time (Time)
which are set from the
CDMA System Time Parameters
menu when the test set is in idle state. The CDMA system time in the test set starts at what you set (or internal RTC time when shipped from the factory) and keeps going as the UTC time (Universal Coordinated Time) without leap seconds. It is shown on the
CDMA System Time Information
window and updated every two seconds. To get a more accurate CDMA system time running in the test set, use
CALL[:CELL]:CSTime:TIME
? query command which has one second resolution.
The
CDMA System Time (Date)
can be set to any date from January 6, 1980 to January 5, 2080. The
CDMA System Time (Time)
can be set to any time of the day. You can change the CDMA system time while the test set is in idle state. When setting the CDMA system time from the front panel, you can use a simple way. For example, to set the CDMA System Time to January 1, 2000 2:00 PM, you can simply enter 2000.1.1 in the
CDMA System Time (Date)
field and enter 14 in the
CDMA System Time (Time)
field. Moreover, <second> you enter in odd number will be automatically rounded up to an even number.
The CDMA system time is stored in the test set's non-volatile RAM. Power-cycle, full preset and save/recall operations do not affect the ongoing CDMA system time but power cycle may cause minor uncertainty on CDMA system time. (see
Operating Consideration
).
GPIB Command:
CALL[:CELL]:CSTime:DATE
and
CALL[:CELL]:CSTime:TIME
-
Leap Seconds
Specifies the leap seconds since the start of CDMA system time. It is ranged from 0 to 255 seconds. It is used by
CDMA Local Time
calculation.
It is stored in the test set's non-volatile RAM and is not affected by power cycle, full preset or save/recall operations.
GPIB Command:
CALL[:CELL]:CSTime:LOCal:LEAP
-
IS856 Local Time Offset (hh.mm)
Specifies the local time offset from CDMA system time. It is ranged from -17.00 to +17.00 hours. It is used by
CDMA Local Time
calculation.
It is stored in the test set's non-volatile RAM and is not affected by power cycle, full preset or save/recall operations.
GPIB Command:
CALL[:CELL]:CSTime:LOCal:OFFSet[:SELected]
or
CALL[:CELL]:CSTime:LOCal:OFFSet:TA856
-
CDMA Local Time
Like the CDMA system time, the CDMA local time consists of two portions:
CDMA Local Time (Date)
and
CDMA Local Time (Time)
which are shown on the
CDMA System Time Information
window and updated every two seconds. The CDMA local time is a calculated value which is based on the formula:
CDMA Local Time = CDMA System Time (Date) + CDMA System Time (Time) - Leap Seconds + Local Time Offset
The CDMA local time is primarily used to verify the correctness of the time displayed on the AT's screen. When the AT successfully acquires and synchronizes with the test set, the time displayed on the AT's screen should be same as the
CDMA Local Time (Date)
and
CDMA Local Time (Time)
that are shown on the test set.
GPIB Command:
CALL:STATus:CSTime:LOCal:DATE?
and
CALL:STATus:CSTime:LOCal:TIME?
Changing the Local Time Offset or Leap Seconds results in the CDMA local time immediately updated on the test set's CDMA System Time Information window. However, since these parameters are sent to the AT in the overhead message (
SectorParameters Message
), the local time displayed on the AT's screen may not be same as that on the test set until the updates in the overhead message is received by the AT.
Operating Consideration
-
The
CDMA System Time (Date)
and the
CDMA System Time (Time)
are available only in
Active Cell
or
IS-856 Test Mode
operating mode.
-
The
CDMA System Time (Date)
and the
CDMA System Time (Time)
can only be set when the test set is in idle state.
Most ATs will immediately open a session with the test set once they reach the idle state upon power-up. You can close the session at any time (see
Session Closing State
) and the data connection will be taken to the idle state. However, most ATs will try to immediately re-establish a session. You can prevent the AT from re-establishing a session by turning
Call Limit Mode
on.
-
There is about +/- 1 second uncertainty on CDMA system time when any of the following actions is performed.
-
Cycle power the test set.
-
Perform the Channel Power Calibration, Open Loop ALC Calibration or Average Power Calibration (See
Calibrating the Test Set
).
-
Change the Digital Bus Path setting on the test set (See
Digital Bus Information
).
-
Switch the application format (for example switch between cdma2000 and 1xEV-DO applications) (see
Test Application Switching
).
-
Switch the
Operating Mode
from
CW
(with
Test Signal
set to
AM
or
DSB-SC
) to
Active Cell
or
IS-2000 Test Mode
.
|
|
top
of page