DOUBLY IRREGULAR SPARSE CODE MULTIPLE ACCESS FOR 5G AND BEYOND (B5G) COMMUNICATION SYSTEM

• Main Author: Hidayat, ST, MT, Iswahyudi
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69764
• Institution: Institut Teknologi Bandung

Non–orthogonal multiple access (NOMA) is one of the potential multiple access technique to support massive connectivity for the fifth telecommunication generation (5G) and beyond (B5G). NOMA allocates resource on each user without considering the orthogonality properties, but more on how to use the resources together with sharing principal. NOMA can be divided into two categories, i.e. power domain NOMA and code domain NOMA. The basic idea of SCMA began with the concept of low density spreading code division multiple access (LDS– CDMA). On LDS–CDMA system the code spreader has very low density of ”1”. This properties are different compared to the conventional CDMA, where only few users interefere to each other on each chip. Whereas in SCMA, the setting of the number of users who access the resource is indicated by a mapping matrix. Multidimensional constellation (MDC)–SCMA proposes a mapping matrix that is ordered by knowing that each user accesses the same resource and each resource can be accessed by the same number of users. This dissertation develope SCMA for communication systems of the 5G and beyond (B5G) that require increased spectral efficiency and massive wireless connectivity services with high overloading. This dissertation proposes a new SCMA scheme, called Doubly Irregular Sparse Code Multiple Access (DI–SCMA), which is expected to have a higher overloading factor than the regular SCMA, such that larger number of users can be served. In this double irregular concept, the level of irregularity is applied for both users and resources rather than only for user nodes. This double irregularity in practice is expressed by a mapping matrix showing the number of users accessing the resource (column) and the number of different resources accessed by each user (row). This dissertation proposes an algorithm to design a mapping matrix satisfying the double degree distribution, such that iterative decoding works continuously until all users are decoded. The results show that the proposed mapping matrix is capable of providing services with high overloading factor up to 350%, which is achieved by : (i) multiuser detection (MUD) Q = f2; 3; 4g, and (ii) peeling decoding of which iterative decoding does not stop, because degree distribution is designed properly. In addition, this dissertation also propose a practical MUD Q by making the best mother constellation design by rotating the modulation symbol the longest Euclidean distance to support minimal error. The proposed DI–SCMA in this disseriii tation is expected to support B5G technology in the future to serve more users eventhough the system with limited resources.