RMS Error Vector Time (LTE)
shows the Root Mean Square (RMS) average 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. for each symbol. The RMS average for each symbol is calculated from the subcarrier EVMs of currently selected channels and signals (see Composite Include).
The value "ss" in the "xRMS: ss" or "xPeak: ss" annotation at the top of the trace is how many subcarriers were included in the current measurement. Only symbols containing channels/signals selected in Composite Include are included in the count.
MBMS mixed-mode CP
MBMS Multimedia Broadcast Multicast Service signals are transmitted during the MBSFN region of MBSFN subframes using Extended CP 1) Contention period, or 2) Cyclic prefix mode (6 symbols per slot). The non-MBSFN region of these subframes (and the rest of the frame) can be transmitted in Normal or Extended CP mode.
For mixed-CP-mode LTE Long Term Evolution frames, traces that show time on the x-axis in units of syms (OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. symbols) would need unevenly spaced x-axis points to correctly represent the time locations of the symbols (since extended CP symbols are longer than normal CP symbols).
Instead of using non-uniform x-axis spacing of symbol points, the LTE demodulator shows the time axis as if all the slots used Normal CP (with 7 symbols per slot), and for MBSFN slots, the demodulator fills the first 6 symbols of the slot with the extended CP symbols, leaving the 7th symbol blank.
See Also
