Modulation Per Allocation (Custom OFDM)
Menu Path:
This property is only valid when Resource Interface = Type2.
Modulation Per Allocation is an array describing the modulation type associated with each allocation ID, as listed in the Resource Allocations mapping array.
This property is an array of values, with one value for each allocation ID, as listed in the Resource Allocations mapping array. The values are unitless. The modulation value can be used to determine the type of modulation (BSPK/QPSK Quadrature phase shift keying/16-QAM Quadrature Amplitude Modulation/...etc.) for each allocation. If this array is shorter than the highest allocation ID, any values past the end are assumed to be 0.
| QAM Levels | Modulation | Comments |
|---|---|---|
| 0 | Unknown | Modulation auto-detection mode. |
| 1 | BPSK Binary phase shift keying - A type of phase modulation using 2 distinct carrier phases to signal ones and zeros. | |
| 2 | QPSK | |
| 3 | 8 PSK Phase Shift Keying: A broad classification of modulation techniques where the information to be transmitted is contained in the phase of the carrier wave. | |
| 4 | 16 QAM | |
| 5 | 32 QAM | |
| 6 | 64 QAM | |
| 7 | 128 QAM | |
| 8 | 256 QAM | |
| 9 | 512 QAM | Does not support modulation auto-detection mode (zero "Unknown"). |
| 10 | 1024 QAM | Does not support modulation auto-detection mode (zero "Unknown"). |
| 11 | 2048 QAM | Does not support modulation auto-detection mode (zero "Unknown"). |
| 12 | 4096 QAM | Does not support modulation auto-detection mode (zero "Unknown"). |
| 13 | 8192 QAM | Does not support modulation auto-detection mode (zero "Unknown"). |
| 14 | 16384 QAM | Does not support modulation auto-detection mode (zero "Unknown"). |
| 15 | 32768 QAM | Does not support modulation auto-detection mode (zero "Unknown"). |
| 16 | 65536 QAM | Does not support modulation auto-detection mode (zero "Unknown"). |
| n/a | 8 QAM | no QAM Levels value, must use auto-detection mode (0-unknown) |
| n/a | Rotated BPSK/QPSK | no QAM Levels value, must use auto-detection mode (0-unknown) |
Auto-detecting the modulation format:
Modulation value zero “unknown” is a special case that can greatly simplify Custom 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. setup. Modulation value zero “unknown” instructs the demodulator to detect the format automatically based on a statistical algorithm. This algorithm computes a single result (modulation format) for all subcarriers specified as zero. Modulation zero “unknown” is normally used for a group of subcarriers spread across one or more symbols that all utilize the same modulation format.
The auto-detection algorithm does not support any QAM modulation greater than 256QAM. If your signal uses these modulation formats, you must explicitly use QAM levels (9-16) shown in the table above. Auto-detection algorithm does support 8-QAM and rotated versions of BPSK and QPSK. There is no QAM level value corresponding to these formats, so if your signal uses one of these, auto-detection is the only way to demodulate these subcarriers correctly.
See Also
