Capacity Evaluation of Hybrid TDMA-NOMA for High Altitude Platform Systems

The integration of Non-Terrestrial Networks (NTN) with 5th generation (5G) wireless technology is a topic of exploration by the 3rd generation partnership project (3GPP). High Altitude Platform Station (HAPS) is part of NTN which works at an altitude of 20 km above the earth's surface. Technically, HAPS will have a similar role to Base Transceiver Station (BTS). To be able to integrate HAPS and 5G, it is necessary to support multiple access techniques that are in accordance with 5G specifications. Non-Orthogonal Multiple Access (NOMA) is one of the multiple access options that is considered to meet the specifications of 5G. NOMA uses the principle of superposition coding by dividing each user based on the available power allocation. To decipher the information at the receiver, the successive interference cancellation (SIC) technique is still the favorite. NOMA is not a perfect technique, there are parts that need to be further developed to improve its performance. One part that is still being discussed is SIC. The process of parsing information using SIC will take more time when experiencing an increase in users. In addition, the potential for misreading the information will also result in accumulative errors for other users. In order to improve the performance of traditional NOMA, this paper will use a combination of TDMA-NOMA techniques to limit users sharing power allocation. The TDMA timeslot will limit NOMA pairs so the SIC process will not be more complex. As an illustration, the simulation shown in the form of a summary graph of each technique NOMA, TDMA-NOMA, and OMA which leads to the conclusion that TDMA-NOMA shows a superior performance to other techniques.