Novel code selecting/spacing ALOHA system

In this paper, a code selecting/spacing ALOHA system is proposed. The proposed system not only use Nm spreading codes but also M time slots. The proposed system varies in packet size from KNm Tc to KMNmTc, where K is the number of symbols per packet and Tc is the chip duration. So, the length of the packet for the proposed system changes according to the source data although the message bits per packet are constant. The number of symbols per packet of the proposed system is smaller than that of the conventional direct sequence spread spectrum multiple access (DS/SSMA) ALOHA system. Therefore, the proposed system is expected for improving the throughput performance of the conventional DS/SSMA ALOHA system. In the result of the throughput performance evaluation on the additive white Gaussian noise (AWGN) channel, it is shown that the throughput performance of the proposed system is about 2 times higher than that of the DS/SSMA ALOHA system