Code Channel Time/Phase Error Measurement Description

Last updated: October 28, 2004

NOTE

If the Code Channel Time/Phase Error measurement is running at the time the power control transient transmission starts (see Starting the Reverse CLPC Transient ) the measurement will be closed and its operation aborted. Moreover, the Code Channel Time/Phase Error measurements will not be able to start (become initiated) while the transient transmission is in progress.

How is a Code Channel Time/Phase Error measurement made?

This measurement is designed to analyze signals that contain a reverse pilot channel. A call must be connected with one of the following radio configurations selected:

Fwd3, Rvs3
Fwd4, Rvs3
Fwd5, Rvs4

Each code channel timing and phase measurement tests the time and phase alignment of each code channel relative to the reverse channel pilot signal. The time error returns any offset, in nanoseconds, that is detected between the coding of each Walsh channel and the reverse channel pilot. The phase error measurement determines whether there is any phase difference that would cause a rotation in the I/Q constellation away from the decision points. See I/Q Constellation Showing Phase Error .

I/Q Constellation Showing Phase Error

Code channel time/phase error measurements are made by sampling the down-converted input signal, then applying DSP (Digital Signal Processing) techniques to determine the original data input to the mobile station transmitter's Walsh spreading function for each channel. The DSP then generates a representation of what the "ideal" signal would be given the coding and data in use at the time of transmission. The ideal waveform is then compared with the waveform being measured to determine code channel time error and phase error.

Code Channel Time/Phase Error Measurement Results lists the code channel time and phase measurement results:

Code Channel Time/Phase Error Measurement Results
Code Channel Time/Phase Error
Code Channel Time
Code Channel Phase

Code Channel Time/Phase Measurement Graphical Display

The Code Channel measurement displays the timing and phase error of reverse code channels. A marker can be positioned at any of the 16 Walsh code channels along the graph's horizontal axis. The Marker position field setting applies to both the Time and the Phase error graphs.

Code Channel Time/Phase Error shows an example display for the Code Channel Time/Phase Error measurement.

Code Channel Time/Phase Error

NOTE

If the amount of timing or phase error is negligible, the red error bars may momentarily disappear.

The IS-2000 system achieves high data rates by allowing supplemental channels to occupy multiple code channels. Each marker position displays one spread factor 16 code channel. To facilitate the display of high data rate channels occupying more than one marker positions in one contiguous (wide) bar, the Walsh code sequence along the graph's x-axis is displayed in "bit reversed" order to the marker position numbers 0 to 15. See Walsh Numbering on Code Channel Timing and Phase Graphs .

An example of bit reversal is shown in Walsh Channel Bit Reversal Marker Position 13 has a binary coded decimal value of 1101. If you reverse that sequence, the result is 1011. When 1011 is converted back to a decimal value, the result is Walsh code 11.

Walsh Channel Bit Reversal

Walsh Numbering on Code Channel Timing and Phase Graphs
Marker Position Number	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Walsh Code Channel (with spreading factor = 16)	0	8	4	12	2	10	6	14	1	9	5	13	3	11	7	15

The timing and phase graphs, because of the bit-reversed order, can display channels with a spreading factor less than 16, such as the R-SCH (Reverse Supplemental Channel), using one bin 1 .

For example, Code Channel Timing Graph With R-SCH shows four active code channels displayed in four bins. In bin four, Walsh code channels 1, 3, 5, 7, 9, 11, 13, and 15 are all included in a single channel. If the Walsh numbering on the test set's display were sequential, then this channel would have to be displayed as eight bars, each separated by one Walsh code.

Code Channel Timing Graph With R-SCH

Measurement Behavior

Bin 0 corresponding with Walsh 0 will always return zero for Time Error zero and phase error because all other measurements are relative to the pilot channel, which is located at Walsh 0, bin 0.

Input Signal Requirements

The Code Channel Timing and Phase measurement meets or exceeds specifications when the following requirements are met:

The frequency of the signal being measured must be in the range of 412 MHz to 483 MHz, 800 MHz to 960 MHz, or 1.7 GHz to 2.0 GHz, and within 100 kHz of the expected frequency.
The signal level into the test set's RF IN/OUT connector must be in the range of -25 dBm to +37 dBm. The test set can autorange to a signal that is within +/- 9 dB of the expected input level (see RFANalyzer:AUTO:POWer[:SELected]? ).

Key TIA/EIA-98-E Tests Using Code Channel Time/Phase Error Measurement

Calibrating the Code Channel Time/Phase Error Measurement

The code channel time/phase error measurement is automatically calibrated during a channel power calibration. Follow the channel power calibration schedule and the code channel time/phase error measurement will be properly calibrated. Refer to Calibrating the Test Set for a description of channel power calibration.