Non-Orthogonal Multiple Access (NOMA) technology has been proven effective in serving multiple users simultaneously by applying superposition coding at the transmitter side and Successive Interference Cancellation (SIC) at the receiver side. NOMA has the advantage of improving communication performance, saving bandwidth usage, improving fairness, and increasing system channel capacity. However, behind the promising advantages of NOMA, factors such as channel gain and power allocation techniques must be considered.
These considerations became the focus of Rummi Santi Rama Sirait’s research in her dissertation entitled “Performance Evaluation of Massive loT Network Multiple Access Scheme with NOMA”. This dissertation evaluates the performance of a NOMA-based Internet of Things (loT) access network with power allocation techniques using Lagrange multiplier optimization and Karush-Kuhn-Tucker (KKT) conditions. In addition, the condition of the imperfect SIC process (impSIC) on the Nakagami-m fading channel is also taken into account in this study.
Rummi evaluates the performance of the proposed power allocation scheme concerning parameters such as channel capacity, Outage Probability (OP), and Bit Error Rate (BER). The results of this evaluation are then compared with the Orthogonal Multiple Access (OMA) scheme, the NOMA scheme with the Fixed Power Allocation (FPA) method, and the NOMA scheme with the Dynamic Power Allocation (DPA) method.
Evaluation of channel capacity, OP, and BER shows that the performance of a massive loT multiple access network with NOMA is affected by the number of users served on one sub-carrier, fading coefficient (m), user target rate, and residual interference value. The results show that the optimized DPA-NOMA method significantly affects the system channel capacity.
“The FPA-NOMA scheme can provide greater channel capacity compared to the OMA scheme and the FPA-NOMA scheme. Under the condition of 30 dBm transmission power, the channel capacity of the optimized DPA-NOMA scheme reaches 0.55 Mbps/Hz, while the FPA-NOMA scheme only reaches 0.29 Mbps/Hz and the OMA scheme reaches 0.081 Mbps/Hz,” said Rummi.
The channel capacity performance of user NOMA with ImpSIC in the DPA method is better than the FPA method. An increase in SIC error leads to an increase in residual interference, which in turn can degrade system performance. When the transmission power is 30 dBm, the channel capacity with r=0 is 0.062 Mbps/Hz, 0.5 is 0.050 Mbps/Hz and 0.042 Mbps/Hz.
The presence of residue in the SIC process results in a decrease in the capacity obtained by the system because the residue is considered an interference signal, thus affecting the Signal to Interference and Noise Ratio (SINR) value which also affects the resulting channel capacity value. Increasing the value of the user’s target rate can also worsen the performance of the OP user, this is because more power is used to support a larger target rate.
“Rummi’s results show that the power allocation method used to determine different power levels for each NOMA user affects the system’s channel capacity gain. This research has the potential to make a significant contribution to the development of IoT communication technology,” said Prof. Dr. Heri Hermansyah, S.T., M.Eng., IPU, Dean of the Faculty of Engineering UI (FTUI).
Rummi Santi Rama Sirait’s research dissertation on Performance Evaluation of Sema Multiple Access Massive IoT Network with NOMA succeeded in earning a cumlaude degree with a GPA of 3.92. Rummi was recorded as the 136th doctoral graduate of the Department of Electrical Engineering and the 533rd doctoral graduate of the Faculty of Engineering, Universitas Indonesia. The open session was chaired by Prof. Dr. Ir. Yanuar, M.Eng. M.Sc. with Ir. Gunawan Wibisono, M.Sc., Ph.D. and co-promoter Dr. Wibowo Hardjawana. The examination team consisted of Prof. Dr. Ir. Eko Tjipto Rahardjo, M.Sc.; Prof. Ir. Gamantyo Hendrantoro, M.Eng., Ph.D.; Prof. Dr. Ir. Muhamad Asvial, M.Eng.; Prof. Dr. Muhammad Suryanegara, S.T., M.Sc., IPU; and Ajib Setyo Arifin, S.T., M.T., Ph.D.
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Public Communication Bureau
Faculty of Engineering, Universitas Indonesia