LTE and the Evolution to 4G Wireless: Design and Measurement Challenges, 2nd Edition

6.4.6.2 Coupling Measurements Across Domains

One of the most powerful 89600 VSA software tools used in modulation analysis is the coupling of markers across different measurements, traces, and domains. This tool is particularly effective for analyzing LTE signals, which can have a high symbol content (large number of symbols per frame, burstiness, etc.) and a large number of different signal elements (channels, reference signals, OFDM subcarriers, etc.). Coupled markers allow the user to understand the identity and characteristics of a symbol simultaneously in time, frequency, power, and error. To make this analysis even more specific, coupled markers can be combined with the selection or de-selection of individual LTE physical signals and physical channels for display and analysis.

An example of the use of coupled markers across multiple measurement displays is shown in Figure 6.4-12. This downlink demodulation measurement takes advantage of the 89600 VSA software’s ability to simultaneously show multiple color-coded displays and a complete marker table. With markers coupled and all LTE physical signals and physical channels selected for analysis, a peak search in either the error vector spectrum or error vector time mode indicates the largest error during the measurement interval of one subframe (14 symbols for normal CP). The exact symbol associated with this error can now be understood in terms of time domain OFDMA symbol index, frequency domain subcarrier number, IQ magnitude ...