What is cell reselection in LTE

Test the performance of your LTE eNB

Metrological solution

The R&S®SMW200A vector signal generator can generate standard-compliant LTE signals. Equipped with options for additive white Gaussian noise (AWGN) and fading, various fading profiles and noise levels are available to reliably simulate realistic transmission conditions for UL performance tests on eNBs. Standard-compliant tests of HARQ feedback and UL timing adjustment require a serial feedback line between the eNB to be tested and the signal generator. To test only the HARQ feedback, a simple line for transmitting binary ACK / NACK information is sufficient.

HARQ feedback performance tests

According to the 3GPP conformity specification, the PUSCH must achieve certain throughput values ​​with defined signal-to-noise ratios (SNR) and fading profiles. Various test scenarios are specified, including sophisticated multipath propagation profiles together with various predefined signal settings. These fixed reference channels (FRC) determine the modulation method, the channel coding information and the assigned number of resource blocks. The required FRCs and fading profiles are in the R&S®SMW200A implemented.

The R&S also simulates®SMW200A performs the tasks of the end device so that the eNB can control the transmission of the channel-coded data packets. If the eNB requests the retransmission of a data packet, for example due to difficult transmission conditions, the signal generator automatically uses the next redundancy version or the version encoded in the feedback command of the eNB.

UL timing adjustment tests

3GPP also states that the timing adjustment capabilities of the eNB must be checked. The test according to 3GPP TS36.141, Section 8.2.2, requires the simulation of two end devices: a stationary end device as a reference and a moving end device that is time-adjusted by the eNB. Two different scenarios are defined for the canal conditions.

Thanks to its two-path concept, the R&S®SMW200A fully supports the timing adjustment test. The moving end device is simulated according to the predefined scenario 1 or 2 on one generator path and the stationary end device on the other. Depending on the requested time shifts, the signal generator delays the UL signals of the simulated end devices in real time or brings them forward.

The required throughput is only achieved if the eNB to be tested sends the correct UL timing commands. These UL timing adjustment tests include HARQ retransmissions.

The ability to simulate realistic LTE signals with fading and to process HARQ feedback and UL timing adjustment commands make the R&S®SMW200A an ideal and comfortable solution for base station tests.