Testing a GPRS Mobile Station

1. Configure the base station emulator, mobile station, and measurement execution parameters

Before starting to transfer data and make measurements on a GPRS mobile station, you may need to configure some, or all of the following parameters:

• Broadcast channel (BCH) parameters:

  • Cell Band (see CALL[:CELL]:BAND[:SELected] )

  • Broadcast Channel (ARFCN) (see CALL[:CELL]:BCHannel[:ARFCn][:SELected][:SELected] )
  • Cell Power (see CALL[:CELL]:POWer:AMPLitude[:SELected] )
• Packet data traffic channel (PDTCH) parameters:
  • Packet Data Traffic Channel Band (see CALL:PDTCH:BAND )
  • Packet Data Traffic Channel (ARFCN) (see CALL:PDTCH[:ARFCn][:SELected] )
  • Packet Data Traffic Channel Coding Scheme (see CALL:PDTCH:CSCHeme )
  • Downlink Packet Data Traffic Channel Power Control:
    • Downlink Power Reference Level (dB) (see CALL:PDTCH:PZERo:LEVel )
    • Downlink Power Reduction Level (dB) (see CALL:PDTCH:PREDuction:LEVel[1|2] )
    • Downlink Burst Power Reduction Selection (see CALL:PDTCH:PREDuction:BURSt[1|2|3|4] )

      Note: In order to make use of power reduction levels, you must set the downlink PDTCHs to be on a different ARFCN from the broadcast channel. This is because the power level across all timeslots on the BCH must remain constant. Therefore, power reduction levels are ignored if the BCH and PDTCH are on the same ARFCN.

    • Unused Downlink Burst Power Reduction Selection (see CALL:PDTCH:PREDuction:UBURst )

      Note: In order to make use of power reduction levels, you must set the downlink PDTCHs to be on a different ARFCN from the broadcast channel. This is because the power level across all timeslots on the BCH must remain constant. Therefore, power reduction levels are ignored if the BCH and PDTCH are on the same ARFCN.

  • Packet Data Traffic Channel Protocol Control:
    • Packet Timeslot Reconfigure (see CALL:PDTCH:PMESsage:PTReconfig )
    • Packet Power Timing Advance (see CALL:PDTCH:PMESsage:PPTadvance )

  • Data Connection Parameters:

    • Data Connection Type (see CALL:FUNCtion:DATA:TYPE )
    • Data Connection Frame Number Type (see CALL:FUNCtion:DATA:FRAMe:STARt )
    • Data Connection LLC Frame Check Sequence (see CALL:FUNCtion:DATA:BLER:LLC:FCSequence )
    • BLER Block Polling Interval (see CALL:FUNCtion:DATA:BLER:POLLing:INTerval )
    • Payload Pattern (BLER) (see CALL:FUNCtion:DATA:PAYLoad:PATTern:BLER )
    • Payload Pattern (ETSI B) (see CALL:FUNCtion:DATA:PAYLoad:PATTern:ETSIB )

  • Multislot Configuration (see CALL:PDTCH:MSLot:CONFiguration )
  • First Downlink Burst to Loop (see CALL:PDTCH:MSLot[:FIRSt]:DOWNlink:LOOPback[:BURSt] )

Note that some BCH and PDTCH parameters are fixed parameters. This means that their values cannot be changed (see Fixed Parameters ).

• Mobile station operating parameters:
  • PDTCH MS TX Level (see CALL:PDTCH:MS:TXLevel[:SELected]:BURSt[1|2] )
  • Guard Band Period Length (see CALL:MS:TX:BURSt:GPLength )

• Measurement execution parameters:
  • The SETup subsystem is used to configure measurement parameters. For a brief description of this subsystem and links to the GPIB commands, see SETup Subsystem . For a more detailed description of measurement execution parameters along with programming examples, see Step 3: Set Measurement Parameters .

• Deferred parameters (if required):
  • Deferred parameters allow you to set up a new data connection ahead of time.This is useful if you plan to reconfigure the data connection after your first set of measurements to make more measurements on the new channel. The settings you make are only applied when a channel change is executed using the CALL:HANDover | HANDoff[:IMMediate] . For a list of the deferred parameters see Configuring the Packet Data Traffic Channel (PDTCH) . For more details on using deferred parameters see Using Deferred Parameters .

2. Switch on the GPRS mobile station, perform an attach and establish a data connection

Ensure the GPRS mobile station you want to test has either a GSM Test SIM card, or a standard GSM SIM card installed. When you connect your mobile station to the test set and switch the mobile station on, it should automatically perform a GPRS attach. (For those mobile stations which do not automatically perform a GPRS attach, you may have to instruct the mobile station to go into a data mode. The method for doing this will vary from one mobile station to another. For example, you may have to press a key on the mobile station's keypad, or make a selection from the mobile station's on-screen menu system.)

The mobile station must be GPRS attached before you can use the command CALL:FUNCtion:DATA:START to start the data connection. You can verify that a data connection has been successfully established, by checking that the connection status is "transferring". (If you require more details on connection states see Data Connection Processing State Synchronization ).

If you have problems starting the data connection with your mobile station under normal conditions, you may want to try changing the frame numbering scheme using the command CALL:FUNCtion:DATA:FRAMe:STARt .

If you have problems establishing a data connection using the BLER Data Connection Type specifically, you may want to change the setting of the Data Connection LLC Frame Check Sequence (see CALL:FUNCtion:DATA:BLER:LLC:FCSequence ) or the BLER Block Polling Interval (see CALL:FUNCtion:DATA:BLER:POLLing:INTerval ).

If you require more troubleshooting information related to getting the mobile to perform a GPRS attach, or start a data connection, see GPRS Data Connection Troubleshooting .

3. Make measurements and obtain results

Now that the data connection is successfully established, you can start making concurrent transmitter measurements and gathering results. Output RF Spectrum, Transmit Power, Phase and Frequency Error, and Power versus Time are all available for GPRS. In addition, you can make Receiver Bit Error, or Block Error measurements in parallel with your transmitter measurements.

The FETch subsystem is used to obtain transmitter and receiver measurement results. For a description of this subsystem along with links to the GPIB commands, see FETCh? Subsystem .

You may want to vary the downlink power to stress the mobile's receiver during your testing (see Downlink PDTCH Power Control ).

If you want the test set to perform Transmit Power, and Phase and Frequency Error measurements on both bursts of a multislot configuration which features two adjacent uplink timeslots, you can select only one burst at a time to measure (using the command RFANalyzer:MSLot:MEASurement:BURSt ). In order to optimize your test code, the recommended method is to select the first burst you want to measure, perform the first set of Transmit Power, and Phase and Frequency Error measurements and then repeat these measurements after you have selected the second burst. To select a multislot configuration with two adjacent uplink timeslots (that is, D2U2 or D3U2) use CALL:PDTCH:MSLot:CONFiguration . Note that the Power versus Time measurement can measure over both bursts in a multislot configuration with two adjacent uplink timeslots. If you require more details on the Power versus Time measurement, see GPRS Power versus Time Measurement .

For more details on the process of making measurements and gathering results, see Step 5: INITiate and FETCh Measurements .

4. Reconfigure the data connection and make more measurements (if required)

In order to test the mobile station using different parameters, such as channel number, channel band, or mobile station transmit level, you have to reconfigure the data connection. To do this, you can execute a channel change using the CALL:HANDover | HANDoff[:IMMediate] . This applies the deferred parameters that you set earlier (see Deferred Parameters above). If you require more details on the process of reconfiguring the data connection, see Step 6: Reconfigure Test Set and Mobile Station Connection Parameters .

Note that additional PDTCH protocol control parameters are available in case your mobile station does not support the Packet Timeslot Reconfigure (PTR) message. (If you require details on these parameters, see CALL:PDTCH:PMESsage:PPTadvance and CALL:PDTCH:PMESsage:PTReconfig ).

5. Disconnect the Mobile Station from the base station emulator

When your testing is complete, you need to end the data connection (using CALL:FUNCtion:DATA:STOP ) and then initiate the GPRS detach procedure from the mobile station. If you require more details, see Step 7: End the Connection . You should note that the GPRS detach procedure is optional in a testing environment. The test set can be left in the Attached data connection state and will recognize if a different mobile station performs a GPRS attach.

Downlink PDTCH Power Control

For GPRS-specific testing of mobile stations, you must take into consideration the multislot mode of operation (where a single packet data connection uses multiple timeslots on the same ARFCN possibly at different power levels). In GPRS, downlink power levels are referenced to the power reduction reference level (which in turn is referenced to the BCCH). ETSI refers to these power reduction levels as PR values, and the reference level is known as P0. In the test set, the power reduction levels are implemented as two values (PRL1 and PRL2) which can be mapped to any downlink burst.

P0, PRL1, and PRL2 are shown in the figure below. Note that the BCH (including GPRS indicator) is shown on the same ARFCN in the figure only to illustrate the BCH level. To make use of power reduction levels, you must set the downlink PDTCHs to be on a different ARFCN from the BCH.

GPRS Power Reduction Levels

Use the following commands to set the BCH power, P0 reference level, and PDTCH power reduction levels:

• To set the Cell Power (BCH power level), use CALL[:CELL]:POWer:AMPLitude[:SELected] .
• To set the P0 Reference Level, use CALL:PDTCH:PZERo:LEVel .
• To set the Downlink Power Reduction Level (dB) for PRL1 and PRL2, use CALL:PDTCH:PREDuction:LEVel[1|2] .
• To make the Downlink Burst Power Reduction Selection (either PRL1 or PRL2) for each PDTCH burst, use CALL:PDTCH:PREDuction:BURSt[1|2|3|4] .
• To make the Unused Downlink Burst Power Reduction Selection (either PRL1 or PRL2) for all PDTCH bursts that are not being used for transmitting downlink PDTCH(s), use CALL:PDTCH:PREDuction:UBURst .

Fixed Parameters

A number of GPRS parameters currently have fixed values. These fixed parameters are shown in the following table.