600 Chapter 17
W-CDMA Downlink Digital Modulation for Receiver Test
Out-of-Synchronization Testing Overview
Out-of-Synchronization Testing Overview
The signal level transmitted by the UE is based on transmit power control (TPC) control information
received from the base station. This control information is contained in the DPCCH. When the DPCCH
power level is significantly reduced, the UE may not be able to decode the TPC bits. When the UE can no
longer decode the TPC bits, it has no way of controlling its power output and should terminate transmission.
When the DPCCH power level is restored, the UE should be able to decode the TPC information and begin
transmitting.
Out-of-synchronization testing is used to determine whether or not a UE can detect that the base station’s
dedicated physical control channel (DPCCH) power has decreased to an undesired level and to also detect
when the DPCCH power returns to a sufficient amplitude. When the UE determines that the DPCCH power
is too low, it is required to discontinue its transmission. When the proper DPCCH power level is received,
the UE is required to begin transmitting. This test is described in the 3GPP specifications.
The ESG provides a method of out-of-synchronization testing by implementing an adjustable discontinuous
transmission (DTX) period for the dedicated physical channel (DPCH). Since the DPCCH is multiplexed
with the dedicated physical data channel (DPDCH) onto the DPCH, injecting a DPCH DTX period
simulates a DPCCH low power condition. The length of the DTX period is determined by an input DTX
gating signal. You are given the option of either having the DTX period occurring on the positive
transition/duty period of the trigger signal or occurring on the negative transition/period. The DTX gating
can be provided by an external source or you can simply use the ESG’s LF Output function as demonstrated
in the procedure “Configuring the DPCH DTX Gating Trigger Signal” on page 606.
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