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Graphical Access Probe Power Measurement Description
Last updated: October 28, 2004
This section is only applicable to the lab application.
How is a Graphical Access Probe Power measurement made?
The graphical access probe power measurement consists of a series of up to 60 channel power measurements, each triggered by a rise in RF power detected on the test set's RF input. The measurement trigger threshold is approximately -45 dBm/1.23 MHz.
Access probe sequences are transmitted by the mobile station during registrations or mobile station originated calls. Access probe sequences consist of a series of RF power "steps" which increase in power according to the step size setting until the maximum number of steps is reached or the call processing event completes, for example when the call connects.
Each graphical access probe power measurement cycle is initiated by a GPIB INIT command or by pressing the
START SINGLE
key. During a measurement cycle the following events can trigger access probe power measurements:
-
Registrations (including power-up and timer based)
-
Mobile station originated calls (pressing the SEND key on the mobile station)
-
Test Set originated calls (pressing the Originate Call key on the test set).
When a graphical access probe power measurement is initiated, the test set calculates the number of access probes expected from parameters set up in the Graphical Access Probe Power Setup menu (see
Graphical Access Probe Power Measurement Parameters
) assuming that Call Limit Mode is turned on (see
C. Turn Call Limit On.
). Pressing the
MEASUREMENT RESET
key will clear the display.
Considerations when making Graphical Access Probe Power measurements
Graphical access probe power measurements do not run concurrently with any other measurements. If any measurement(s) are open when graphical access probe power is opened, they will automatically be closed.
When a call is originated from the test set, and call limit is on, the call processing state of the test set remains in a non-idle state (usually Access Probe or Registering) after the graphical access probe measurement has completed. Before attempting the next measurement, the End Call (F3) key must be pressed or a GPIB command to end the origination must be sent before attempting the next measurement.
Changing the number of steps and step size will affect the power level displayed if more than one access probe is transmitted by the mobile station. However, the number of access probes transmitted depends on whether or not the test set responds by acknowledging the access request, thereby ending the access attempt. To view the full access probe sequence, you must prevent the test set from responding to the mobile station access probe request by turning the Call Limit Mode on (key
F10
in Call Parms, 2 of 3 screen). For the GPIB command syntax, see
CALL:CONNected:LIMit[:STATe]<[:SELected]|:TA2000>
.
It is recommended that you always turn the Call Limit Mode on when measuring access probe power. The easiest way to induce access probes from the mobile station is to page the mobile station. If you do not have call limit mode set to on, the call connection will complete, which clears the access probe power result from the measurement screen. Set call limit mode back to off when you have finished measuring access probe power.
When the mobile station performs any type of registration, an access probe power measurement will likely be triggered. Registrations can occur on mobile station power-up, depending on how the mobile station is programmed. Registrations may be requested by the test set at pre-determined time intervals, which will periodically cause the access probe power measurement to update. To control timer based registrations, access the Registration Parameters menu (see
D. Registration Parameters
). For GPIB syntax information on timer-based registrations, see
CALL:REGister:TIMer:STATe
.
It is recommended that you always turn the Timer Based Registration State off when measuring access probe power since the registration events can trigger access probe power measurements to update during a measurement cycle.
Graphical Access Probe Power Measurement Parameters
The parameters shown in the Graphic Access Probe Power Setup menu are different according to the current access channel configured (see
Control Channel Configuration
):
-
When the current access channel is R-ACH, the parameters such as Nominal Power, Nominal Power Extended, Initial Power, Power Step, Number of Steps, Maximum Response Sequence and Preamble Size will be displayed. See
Setting Access Parameters
for details on these parameters:
-
When the current access channel is R-EACH, the parameters such as EACH Nominal Power, EACH Initial Power, EACH Power Step, EACH Number of Steps and Maximum Response Sequence will be displayed. See
Setting Enhanced Access Parameters
for details on these parameters.
-
Measurement Timeout - (see
Timeouts
). The access probe power measurement will remain armed indefinitely until the maximum number of access probes is received, unless the measurement timeout is On or the measurement is reset.
Graphical Access Probe Power Measurement Results
Each measurement is displayed in both a tabular and a bar graph format. See
Graphical Access Probe Power Measurement Display
.
Graphical Access Probe Power Measurement Display
Graphical Display
The graphical display shows an access probe power bar graph covering a time span of up to 120 seconds from the first access probe. Access probe power is displayed using yellow bars on the graph and the graph can display up to 60 access probes, labeled 0 through 59. Power levels are displayed in units of dBm/1.23 MHz.
The number of access probes equals Number of Steps plus 1. For example, when Number of Steps is set to 3, the display shows 4 yellow bars in one access probe sequence.
If the absolute power level of an access probe falls below the range of the graph, the value will cause the bar to be invisible (it will clip). The correct value for the absolute power level will be displayed in the table at the bottom of the display.
The graphical display is accessed by the Graph Control softkey (see
G. Set Up the Graphical View
). The F5 Graph Span softkey is used to adjust the view window. The view window can be adjusted to include a view of the entire 120 second range, or reduced to include only the access probes or access probe sequences of particular interest. If Graph Span is set to display only a portion of the 120 second time period, the F3 Graph Start Time field can be used to move the Graph Span window.
Two markers are available on the graphical display:
-
Position Marker.
The Position Marker can be moved when the F1 Marker Mode is set to Position. This selection is made automatically if the F2 Marker Position field is adjusted. When Marker Mode is set to position, the position marker can be positioned at each access probe power measurement across the current span of the graph. Measurement results that correspond with the Position Marker are displayed above the graph (the two values to the right of the "Mkr" annunciator) and become highlighted in the table whenever the Marker Mode is not turned off.
-
Delta Marker.
The Delta Marker is available when the F1 Marker Mode is set to Delta. This selection will toggle the F2 softkey label to Marker Delta. When the Marker Delta field is adjusted the delta between the Position Marker and the Delta Marker can be easily observed. Measurement results that correspond with the Position Marker and the Delta Marker are displayed above the graph (the two values to the right of the "Mkr" and Delta annunciators, respectively) and become highlighted in the table whenever the Marker Mode is set to Delta.
Tabular Display
A table below the graphical display lists the following measurement results for up to 60 access probes:
-
An access probe number indexed to each marker position.
-
The absolute power of each access probe measurement in units of dBm/1.23 MHz.
-
The delta power between adjacent access probes.
-
The time that each access probe arrived relative to the first access probe.
The table has the capacity to display 20 access probes. To scroll through the table adjust the Position or Delta Marker position field.
Measurement Progress Indicator
A measurement progress indicator in the lower left portion of the display continually updates the ratio of access probes received to the number of access probes expected. Each access probe power measurement cycle ends when the expected number of access probes have been received, the measurement times out, or the measurement is aborted or reset.
If there is a measurement problem associated with an access probe, a non-zero integrity indicator (see
Integrity Indicator
) will be displayed below the table and the access probe's power measurement will appear in reverse video (black text on a white background).
Input Signal Requirements
The graphical access probe power measurement meets or exceeds specifications when the following input signal requirements are met:
-
The frequency of the signal being measured must be within the range of 412 MHz to 483 MHz, 800 MHz to 960 MHz, or 1.7 GHz to 2.0 GHz, and be within 100 kHz of the expected frequency.
-
The average power level of the signal at the RF IN/OUT connector must be between -61 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 the Graphical Access Probe Power Measurement
Calibrating the Graphical Access Probe Power Measurement
The graphical access probe power measurement is automatically calibrated during a channel power calibration. Follow the channel power calibration schedule and the graphical access probe power measurement will be properly calibrated. Refer to
Calibrating the Test Set
for a description of channel power calibration.
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