An Uplink Random Access Scheme Based on ALOHA System Assisted by Gain Division Multiple Access

Gain division multiple access (GDMA) is a non-orthogonal (NOMA) technique for uplink communications. In GDMA, the receiver employs both magnitudes and phases of channel gains associated to users separate users. power-domain NOMA, power levels users.We apply GDMA concept together with orthogonal frequency (OFDM) combat collision problem in ALOHA system. Our goal minimize complexity devices (users) required coordination obtain high throughput simultaneously random protocol. For proposed unslotted OFDM-GDMA-ALOHA, each user randomly chooses Zadoff-Chu (ZC) sequence as its preamble transmitted packet so that can information timing coarse estimation. Moreover, fine estimation obtained by using cluster-based method. Simulation coded OFDM-GDMA-ALOHA system BPSK modulation demonstrates performance be better than slotted without GDMA.We also provide simulation which shows very achieved if synchronization slots obtained.