Troubleshooting (LTE)

Demodulation fails to lock-on signal

Signal not present.

Check test setup connections.

Carrier too far from center frequency.

Enable extended frequency lock range and adjust center frequency to within ± 37.5 KHz of the carrier frequency.

Input is over-loaded or under ranged.

Adjust input range.

Frequency span is too narrow.

Increase frequency span.

Downlink: Incorrect Cell ID, RS-PRS, or CP Length

Uplink: Incorrect Half-subcarrier Shift, CP Length, or sync slot settings/user allocations.

Make sure that the LTE demodulator settings and user allocations match the input signal.

I and Q channels are swapped.

Enable the Mirror Freq. Spectrum setting.

Signal has an incorrect P-SS Primary Synchronization Signal.

Change sync type to C-RS Cell-specific RS and set Cell ID manually.

Signal has incorrect symbol clock.

Adjust Time Scale Factor to match the signal.

I/Q misaligned using I+jQ receiver.

Ensure that trigger delays for the hardware channels assigned to I and Q are correct.

Signal contains an antenna port transmission with a phase rotation of more than 45 degrees and RS-PRS is set to Custom.

Set RS-PRS to 3GPP to allow RS-PRS to be determined by Cell ID according to the standard.

Both uplink and downlink transmissions present in a TDD Time Division Duplex: A duplexing technique dividing a radio channel in time to allow downlink operation during part of the frame period and uplink operation in the remainder of the frame period. signal being analyzed.

Select Uplink Present in Signal or Downlink Present in Signal, as appropriate.

High EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format.

Time capture includes data where no LTE frame is being transmitted.

Make sure that the entire time capture is filled with an LTE signal.

The demodulator uses all of the time capture data (see Result Length) to calculate equalization coefficients.

PDSCH Physical Downlink Shared Channel parameters not configured correctly for a multi-antenna signal.

Make sure that the precoding type, number of layers, number of codewords, CDD Cyclic Delay Diversity (CDD): To avoid unintentional beamforming, the IEEE 802.11n draft standard uses a process known as Cyclic Delay Diversity (CDD), which basically offsets each spatial stream by a different constant, non-coherent delay. The offset considerably lowers the likelihood of correlated signals being transmitted by two or more antennas. This, in conjunction with a pseudorandom scrambler run over the transmitted data bits, ensures that the likelihood of two spatial streams correlating is very low., and codebook index are set correctly for each user in the LTE Allocation Editor.

Codeword 1 is being transmitted but is not included in analysis.

Make sure the check box to the left of CW1 Mod Type in the PDSCH tab is selected for user mappings that contain CW1 transmissions.

Only P-SS and S-SS Secondary Synchronization Signal have high EVM

P-SS/S-SS Antenna Port is not set correctly.

Make sure the P-SS/S-SS Antenna Port parameter is correct for the signal being analyzed.

The port that P-SS and S-SS are transmitted on needs to be specified because the standard states that the receiver shall not make any assumptions about which antenna port P-SS and S-SS are transmitted on.

The constellation symbol shape, such as dots, is not properly displayed on traces.

The display driver is not functioning correctly.

Contact your PC manufacturer to see if a newer version of the display driver is available. If not, try decreasing the hardware acceleration. See the Windows documentation for instructions.