Performance analysis of STBC noma systems in dampered channels

Nowadays, the increase in the number of users and the communication of objects with each other has caused an increase in data traffic and has made it important to use resources more efficiently. For these reasons, the orthogonal multiple access (OMA) communication technique has become inadequate. Especially with the transition to 5G technology, the inadequacy of the OMA technique has become even more evident. The search for a solution to this situation has directed the non-orthogonal multiple access (NOMA) technique, which provides more efficient use of resources. In this study, transmissions of 2-user and 3-user structures located at different distances were realized in the Rayleigh channel by using NOMA technique. Then, in order to make the NOMA technique more efficient, Alamouti Space-Time Block Coding (STBC) structure was used. Simulations were performed for the traditional NOMA structure and 2x1 (2 Transmitter-1 Receiver) Alamouti-STBC NOMA structure and 2x2 (2 Transmitter-2 Receiver) Alamouti-STBC NOMA structure for 2 users and 3 users by applying the Quadrature Phase Shift Keying (QPSK) modulation method from the source in MATLAB program depending on the power (P) variable. In the simulations, the changes in the bit error rate (BER) and service interruption probabilities depending on the P variable were created and their changes were examined. As a result of examining the graphs, it was concluded that the 2x2 Alamouti-STBC NOMA structure for 2 users has better BER performance for each user (Near user, Far user) in the Rayleigh channel compared to the traditional NOMA, 2x1 Alamouti-STBC NOMA structures. Again, it was observed that the 2x2 Alamouti-STBC NOMA structure has better service interruption probability performance for each user (Near user, Far user) in the Rayleigh channel compared to the traditional NOMA, 2x1 Alamouti-STBC NOMA structures. Again, as a result of examining the graphs in the simulations made for 3 users, it was concluded that the 2x2 Alamouti-STBC NOMA structure has better BER performance for each user (Near user, Middle user, Far user) in the Rayleigh channel compared to the traditional NOMA, 2x1 Alamouti-STBC NOMA structures. Again, it was observed that the 2x2 Alamouti-STBC NOMA structure has better service outage probability performance for each user (Near user, Middle user, Far user) in the Rayleigh channel compared to the traditional NOMA, 2x1 Alamouti-STBC NOMA structures.