An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: generate (606) a synchronization signal for transmission over one or more symbols, wherein the number of symbols is dependent on a subcarrier spacing.

The present disclosure relates to demodulation reference signal (DMRS) design with code division multiplexing (CDM) group expansion. A network device may be configured to generate a DMRS and send the DMRS to a wireless device. The DMRS may be coded with one of a plurality of expanded orthogonal cover codes (OCCs) belonging to an expanded CDM group. The expanded CDM group may be generated by expanding a legacy CDM group including a plurality of legacy OCCs. The number of frequency domain elements in each of the plurality of expanded OCCs may be expanded as twice the number of frequency domain elements in each of the plurality of legacy OCCs.

An extensible communication system is described herein. The system includes a first module for receiving a root index value and for generating a constant amplitude zero auto-correlation sequence based on the root value. The system further includes a second module for receiving a seed value and for generating a Pseudo-Noise sequence based on the seed value. The system further includes a third module for modulating the constant amplitude zero auto-correlation sequence by the Pseudo-Noise sequence and for generating a complex sequence. The system further includes a fourth module for translating the complex sequence to a time domain sequence, wherein the fourth module applies a cyclic shift to the time domain sequence to obtain a shifted time domain sequence.