RACH Measurement Description
Last updated: December 3, 2008
What is a RACH?
The RACH (Random Access Channel) is used by the mobile station to request a dedicated channel from the base station. The RACH is sent on the random access burst which is the first burst sent to the base station by the mobile station when a call origination or data connection is attempted. The random access burst is only 312.2 us as opposed to the normal GSM burst of 542.8 us.
Measurements that can be performed on a RACH
The test set can perform the following three measurements on a RACH in Active Cell or a test mode:
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Power versus Time
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GSM/GPRS Transmit Power
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Phase and Frequency Error
Only one measurement at a time can be made on the RACH even if two measurements are initiated.
Triggering
The type of triggering used is dependent on whether you are in Active Cell or Test mode:
Active Cell mode:
The default triggering of Auto is acceptable for most signals. (In Active Cell mode Auto is equivalent to Protocol.) However, if the mobile's RACH timing is outside the specified limits you may need to use RF Rise triggering.
Test mode:
The default triggering of Auto should be used. (Trigger Auto is equivalent to RF Rise in a test mode.)
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