3GPP51.010-1Mobile Station (MS) conformance specificationPart 1: Conformance specificationTS
3GPP TS 05.05, annex I calls for a best-case MS measurement observed timing difference (OTD) accuracy of 100 nanoseconds. This level of measurement accuracy implies that:
1. The time delay and phase shift of all components in the test environment must be taken into account.
2. The laboratory equipment utilized to measure the burst alignment of the two base station simulators must support a time resolution of at least 10 nanoseconds.
3. All base station simulators, active RF channel simulators, and time measurement equipment must be phase-locked to a common reference clock.
4. All base station simulators used for this test must be frame synchronized.
Figure A6-1 represents a recommended configuration for the unassisted measurement of E-OTD accuracy. If this test environment is utilized, the effects of differing cable lengths, channel simulator processing delays, etc., must be compensated for in order to establish the RTD between bursts from the base station simulators.
The "unassisted" test environment should require a relatively short time (< 3 000 s) for the test environment to obtain N measurements for the purpose of calculating the RMS90 timing error of the MS. In many cases, the predominant component leading to uncertainty in RTD between the two base station simulators during the measurement period will be phase jitter, which should follow a Gaussian distribution. The standard deviation of this distribution must be kept within a range that allows the test laboratory to confirm that this uncertainty component does not significantly affect the results of the OTD measurements made and reported by the MS. Test labs and base station simulator manufacturers are expected to quantify and document the test environment’s RTD. Test labs and base station simulator manufacturers are also expected to have some means of verifying the standard deviation of the test environment’s RTD (including phase jitter introduced by the RF channel simulators), declaring that this uncertainty will be negligible relative to the 100 nanosecond RMS90 best-case requirements of 3GPP TS 05.05 (V8.7.1), Release 99, annex I.
Figure A6-1: "Unassisted" E-OTD Test Environment