A-GPS Solution in the Test Set
To allow the testing of A-GPS capability of a mobile stations, the test set provides an "RRLP pipe" mode. The test set provides a mechanism for passing encoded RRLP messages over the air to the mobile station and retrieving the mobile station's response. The test set does not provide for encoding or decoding the A-GPS messages. It also does not validate the message contents. The complete RRLP message must be encoded and decoded external to the test set. The test set accepts hexadecimal character strings to represent the RRLP binary message content.
You can enable/disable automatic header creation and segmentation of the RRLP binary message by setting the RRLP Header state.
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When the RRLP Header state is set to ON, the Application Protocol Data Unit (APDU) ID and APDU Flags field are present in the RRLP messages, the test set creates the APDU ID and APDU Flags field. The individual RRLP messages can be up to 1000 bytes, or 2000 characters of hex.
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When the RRLP Header state is set to OFF, the Application Protocol Data Unit (APDU) ID and APDU Flags field are not present in the RRLP messages. You must create the APDU ID and APDU Flags field and include them in the hexadecimal message.The individual RRLP messages can be no longer than 251 characters of hex. However, the first two octets of the message sent by the mobile are also checked to ensure they carry the correct Protocol Discriminator, Skip Indicator and Message Type.
The RRLP pipe can only be setup and controlled using GPIB commands. See
CALL:PPRocedure:PMEasurement:PIPE
for information about each of the RRLP pipe commands.
When the test set's RRLP layer is in RRLP pipe mode, the standard RRLP message interface for E-OTD testing in the test set is disabled. However, either type of RRLP message (E-OTD or A-GPS) can be sent in the RRLP pipe mode. Messages sent using the RRLP pipe mode must be encoded external to the test set. See
E-OTD (Enhanced Observed Time Difference)
for more information about the E-OTD testing in the test set.
Time To First Fix (TTFF) response time
The TTFF response time measurement is defined in 3GPP TS 51.010 "... starting from the moment that the MS has received the final RRLP MEASURE POSITION REQUEST sent before the MS sends the MEASURE POSITION RESPONSE containing the Location Information or the GPS Measurement Information, and ending when the MS starts sending the MEASURE POSITION RESPONSE ".
In order to achieve an accurate measurement of this response time duration, the time of the final RRLP pipe transmission frame e.g. the MEASURE POSITION REQUEST and the time of the first frame of an MS transmitted RRLP frame e.g. MEASURE TRANSMISSION RESPONSE are stored by the test set and are available to the user. The resolution of both the transmit and receive times is one GSM frame period i.e. 4.615mS. The operation to calculate the TTFF is ((RxTime - TxTime + GSM Hyperframe) modulo GSM Hyperframe) x 4.615 mS.
Query the frame number of the last transmitted RRLP pipe message with GPIB command
CALL:PPRocedure:PMEasurement:PIPE:SEND:TSTamp?
. Query the received RRLP pipe message with
CALL:PPRocedure:PMEasurement:PIPE:DATA:RX:TSTamp?
. And remember to clear the transmit timestamp before query the frame number with
CALL:PPRocedure:PMEasurement:PIPE:SEND:TSTamp:CLEar
.
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