Non-alloc (LTE)

Default: Cleared

When Non-alloc is selected, unused subcarriers are shown on applicable traces, such as IQ Meas and Error Vector Time/Error Vector Spectrum.

Non-Alloc signals consist of unused subcarriers in the LTE Long Term Evolution frame. The demodulator expects Non-alloc subcarriers to be null (zero power). Non-Alloc signals include the following:

Unallocated user data subcarriers
The unused DC subcarrier In an orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) signal, the subcarrier whose frequency would be equal to the RF center frequency of the station.
Unused P-SS Primary Synchronization Signal and S-SS Secondary Synchronization Signal subcarriers: these signals are 6 RBs (72 subcarriers) wide in the frequency domain, but only the center 62 subcarriers are actually used, and the remaining 10 are set to zero.
Unused PDCCH Physical Downlink Control Channel subcarriers
Subcarriers reserved for C-RS Cell-specific RS in a signal with multiple C-RS antenna ports. For example, in a signal with four C-RS ports, port 0 will not transmit on the subcarriers that are used for C-RS in the other three antenna port transmissions.

For downlink, manually defined and autodetected user allocations are always considered allocated and are not included in Non-alloc, whether or not they are enabled for display in Composite Include. For uplink, only those channels that are specified as being present in the signal are considered allocated.

The Non-Alloc channel shown in Frame Summary only includes information from unallocated PDSCH Physical Downlink Shared Channel subcarriers. See the Frame Summary Non-alloc topic for more information.