LTE / LTE-Advanced
- Use the LTE test case wizard for your eNB conformance testing
- Test the ON/OFF power of your TD-LTE base station
- Visualize your radio network performance
- Simplify field testing of remote radio heads
- Test your remote radio head solutions
- Filtering and how it impacts the performance of your LTE signal
- Time windowing and how OFDM impacts the shape of your LTE signal
- Test the performance of your LTE eNB
- TOOL: LTE Resource Allocation
- VIDEO: LTE-Advanced - Carrier aggregation testing with a real DUT presented at GSMA MWC 2012
- VIDEO: Combined PQA and RF test system for video over LTE testing presented at GSMA MWC 2012
- VIDEO: Test system for mobile wireless location based services presented at GSMA MWC 2012
- VIDEO: Multi-band LTE MIMO drive test presented at GSMA MWC 2012
- VIDEO: Voice over LTE audio quality testing presented at GSMA MWC 2012
- VIDEO: LTE protocol testing with SRVCC support presented at GSMA MWC 2012
- VIDEO: LTE rollout challenges: Straight talk from Rohde & Schwarz at LTE World Summit 2011
- More Applications
Your task
Since 3GPP does not specify a filter for long term evolution (LTE), the receiver cannot rely on a defined signal shape like in 3G. This creates possibilities and also presents challenges. The design engineer can optimize the transmitter chain for an LTE signal either for in-channel performance (transmit quality, e.g. EVM) or for out-of-channel performance (ACP, SEM). The challenge is to find the right balance between both.
The transmission scheme used also has a major impact on the shape of a signal. The spectrum of an OFDM signal shows spectral spikes that are caused by the discontinuity between two OFDM symbols during signal generation.
The OFDM principle leads to discontinuities between two consecutive symbols.
Spikes on both edges of the spectrum result from discontinuities at the transition between two consecutive OFDM symbols.
T&M solution
To reduce these spectral spikes, time domain windowing can be applied during signal generation.
Smoothing the transition between two consecutive OFDM symbols reduces the spectral spikes. Rohde & Schwarz signal generators, including the
The screenshots below illustrate the impact that selecting a transition time of 1 μs and 9 μs has on a spectrum. Spectral spikes are clearly reduced with increasing transition time. While spectral spikes can be minimized by applying time windowing, the EVM performance degrades because time domain windowing acts like an artificial intersymbol interference (ISI). The
The extensive feature set, including time windowing, as well as preset and user-specific filter types available for Rohde & Schwarz signal generators enable test engineers to verify the behavior of their transmitter circuit against specified tolerances and to optimize their design to achieve the best performance.
Impact of a transition time of 1 µs (left) and 9 µs (right) on a spectrum. As time domain windowing increases, spectral spikes are reduced while EVM performance degrades.
