Spectrally-Null-Constrained ZCZ Sequences for MIMO-OFDM Channel Estimation Over Non-Contiguous Carriers

In cognitive radio (CR) networks with non-continuous carriers, designing spectrally-null-constrained (SNC) sequences with good correlation properties is an important research task. In this letter, two types of SNC sequences with zero correlation zone (ZCZ) property are considered: single-channel SNC-ZCZ sequences and multi-channel SNC-Z-periodic complementary sequences (SNC-ZPCSs), which have potential applications for CR-multiple-input multiple-output (MIMO) channel estimation and CR-quasi-synchronization communications to achieve interference-free performance. The resultant SNC-ZCZ sequence sets are optimal with respect to the theoretical bound and the spectral-null constraint can be set flexibly. Simulation results demonstrate that such sequences are suitable for pilot design in CR-MIMO-orthogonal frequency division multiplexing (OFDM) system. Besides, a construction of multi-channel SNC-ZPCS sets was provided based on single-channel SNC-ZCZ sequence sets.