IQ Ref Time (LTE)
shows the same information as the IQ Ref trace when the data is shown in the or trace format. When the data is shown in any other format, time is on the horizontal axis instead of frequency as in the trace.
The information in the IQ Ref topic applies to , with the exception mentioned above.
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
