Hanyuan Huang, Tao Li and Hui Zhao, Sichuan University, China

Non-orthogonal multiple access (NOMA) can support massive accesses in 5G. Sparse code multiple access (SCMA) is a typical NOMA technology. Basic principle of SCMA is that multiuser bit data directly map into multi-dimensional complex sequences through codebooks. Grantfree SCMA allows users to select codebooks from codebook pool to send data instantly, reducing the cost of overhead and delay of granting process. When the receiver and the sender use same codebook information, the data can be transmitted correctly. But in current SCMA researches, the problem of asymmetric codebook information between sender and receiver caused by the intrusion of codebook pool is not considered. In this paper, abnormal codebook detection is proposed in the grant-free SCMA. Because most of intrusion is unknown, initial detection is realised by comparing characteristics of tested codebooks with those legal ones concluded during codebook design process. In this paper, tested objects in the test process can include but not limit to codebook structure, constellations, distribution of constellations, overall feature of codebook pool. Test is executed until discovering error states or accomplishing all tested contents. Inspired by the distinction between self and non self in the artificial immune system, tested abnormal codebooks are saved to act as detectors. To take full advantages of known non-self codebooks, saved detectors are further evolved, and future detection can do match with detectors which are evolved from those known abnormal codebooks to discover some kinds of unknown abnormal codebooks.

Grant-free SCMA, SCMA codebooks, abnormal codebooks detection, artificial immune system, abnormal codebook evolution.