An orthogonal frequency-division multiplexing (OFDM) signal is obtained by spreading a sequence of N.sub.bit number of bits to obtain N.sub.symb number of modulation symbols based on multiplying each bit in the sequence of N.sub.bit number of bits with a corresponding spreading sequence in a sequence of N.sub.bit number of spreading sequences. Each spreading sequence in the sequence of N.sub.bit number of spreading sequences is a linear phase sequence having a constant rotational phase angle . The N.sub.symb number of modulation symbols are multiplied with a discrete Fourier transform precoder to obtain N.sub.symb number of Fourier coefficients. The OFDM signal including the N.sub.symb number of Fourier coefficients mapped onto K number of OFDM subcarriers is transmitted.

Described herein are systems, methods, and instrumentalities associated with wireless communications using single carrier waveforms. A wireless transmit/receive unit (WTRU) as described herein may receive configuration information that may indicate a control channel element (CCE) and a plurality of resource groups associated with the CCE. Each resource group may include a respective time resource element (TRE) and a respective frequency resource group (FRG), wherein each respective TRE may include a non-integer number of time units, and each respective FRG may include multiple frequency units. The WTRU may determine that the CCE may be associated with a downlink control channel transmission, and further determine allocation pattern information associated with the resource groups in a search space. The WTRU may receive the downlink control channel transmission based on the determined allocation pattern information and receive a downlink shared channel transmission based on information in the downlink control channel transmission.