Dear Uche,

welcome,

The interpretation of the your constellation is that your signal is 4-QAM modulated. The zero symbol in the constellation appears because you have pauses in the received signal, which will be noise only signal and it be correctly appear as noise signal with zero average amplitude.

As a model for the received signal ,

r(t)= h S(t) +n(t), when the transmitter is active that is S(t) is present,

and r(t)= n(t) for receiving noise only in the absence of the signal S(t)=0.

Best wishges

Additionally, the error vector magnitude (EVM) is very high which is 92% that means vector magnitude is higher between the received signal points and the ideal sampling points. EVM of LTE signal should be less than 20%.

Dear Uche,

another possible answer to the QAM points in the center might be the non-allocated subcarriers. For example, for an LTE signal of 1.4 MHz, you have 72 subcarriers that can transport QAM symbols per OFDM symbol, and depending on the configurations of the cell, some subcarriers might be dis activated (some of the subcarriers "transmit zeros"). In this case, the plot would show the activated subcarriers and the subcarriers that transmit nothing. When they do not transmit QAM symbols, the received constellation shows only the noise around zero.

Good luck!