About Measurement Interval and Offset (W-CDMA(3GPP)/HSPA, cdma2000/1xEV-DV, and 1xEV-DO)

Measurement Interval and Measurement Offset parameters are used to specify what segment of the Result Length data is used for data analysis. This feature is applicable to W-CDMA Code Division Multiple Access: One of several digital wireless transmission methods in which signals are encoded using a specific pseudo-random sequence, or code, to define a communication channel. A receiver, knowing the code, can use it to decode the received signal in the presence of other signals in the channel. This is one of several "spread spectrum" techniques, which allows multiple users to share the same radio frequency spectrum by assigning each active user an unique code. CDMA offers improved spectral efficiency over analog transmission in that it allows for greater frequency reuse. Other characteristics of CDMA systems reduce dropped calls, increase battery life and offer more secure transmission. See also IS-95.(3GPP)/HSPA, cdma20001xEV DV, and 1xEV-DO Modulation analysis.

When the Measurement Interval or Measurement Offset parameters are changed, the VSA computes the new trace data results from the current measurement data (Result Length) and does not require a new measurement cycle.

Typical Frame Structure

• Result Length: Result Length determines the signal capture length. This is the data used by the VSA for demodulation and signal analysis. Make sure that the result length is long enough to capture the desired data. Result Length is specified in terms of an integer number of slots or PCGs, as determined by the specific modulation type; For example, W-CDMA/HSPA uses slots and cdma2000/1xEV-DV uses PCGs.

  Result Length may be specified as an integer number of slots (PCG), frames or time. If you choose to use seconds, the VSA will automatically increment the time as necessary to obtain an integer number of slots (PCG).

  Result Length is a primary factor determining measurement speed. Smaller result lengths will increase the measurement speed, but result lengths less than 6 slots (or 6 PCGs) may cause inaccurate measurement results.

• Measurement Interval: The Measurement Interval determines the time length of Result Length data that is used for computing and displaying the trace data results.

• Measurement Offset: The Measurement Offset determines the start position of the Measurement Interval within the Result Length.

• Slot (W-CDMA(3GPP)/HSPA): One W-CDMA(3GPP) time slot is equal to 2560 chips (666.7 µs at the default chip rate) and one frame is 15 slots (10 ms at the default chip rate).

• Slot (1xEV-DO)): One 1xEV-DO time slot is equal to 2048 chips (1.667 ms) at the default chip rate and one frame is 16 slots (26.667ms).

• Slot (cdma2000/1xEV-DV): A 1.25 ms interval on the Forward Packet Data Control Channel (F-PDCCH) and the Forward Packet Data Channel (F-PDCH).

• PCG (cdma2000/1xEV-DV): A 1.25 ms interval on the Forward Traffic Channel except the Forward Packet Data Channel, the Reverse Traffic Channel, and the Reverse Pilot Channel. Each 20 ms frame is divided into 16 equal length periods (i.e., 1.25 ms), called power control groups (PCG) numbered from 0 to 15. Certain power control groups are gated-on (i.e., transmitted), while other groups are gated-off (i.e., not). One PCG is equal to 1.25 ms or 1536 chips at the default chip rate (1.2288 Mcps Mega Chip Per Second: A measure of the number of bits (chips) per second in the spreading sequence of direct sequence spreading code.).

Measurement Exceptions

Not all trace data results use the measurement interval and offset parameters for computing and displaying measurement results. The following trace data results ignore these parameters and use only the first slot (or PCG) of measured data:

• CDE Composite and CDE Layer trace data (See Antenna 1 CDP trace data (W-CDMA(3GPP)/HSPA), Ch 1 CDP trace data (cdma2000)), and Ch 1 CDP trace data (1xEV-DO))

• All Composite Time trace data (See Antenna Composite Trace Data(W-CDMA(3GPP)/HSPA)) , Comp trace data (cdma2000), and Comp trace data (1xEV-DO)).

• Composite Error Summary trace data (See About Comp Error Summary data (W-CDMA(3GPP)/HSPA), About Comp Error Summary data (cdma2000), and Composite Error Summary data (1xEV-DO)).

W-CDMA (3GPP)/HSPA Parameter Links

• Result Length

• Measurement Interval

• Measurement Offset

cdma2000/1xEV-DV Parameter Links

• Result Length

• Measurement Interval

• Measurement Offset

1xEV-DO Parameter Links

• Result Length

• Measurement Interval

• Measurement Offset

See Also

Time tab (W-CDMA(3GPP)/HSPA Demod Properties)

Time tab (cdma2000/1xEV-DV Demod Properties)

Time tab (1xEV-DO Demod Properties)