NOMA (Non-Orthogonal Multiple Access) is the main technology of 5th generation communication system for controlling the throughputs of users by using power allocation corresponding to information transmission time.
In the previous researches, they assumed that all users have the same channel weights in the aspects of power allocation and sum rate.
However, their assumption makes it difficult to simultaneously satisfy the sum rate and user fairness.
Kim Tong Jin, a researcher at the Faculty of Communication, proposed an improved energy harvesting scheme to achieve the maximum sum rate by using weighted users.
The proposed scheme is based on an energy harvesting model and the sum rate is expressed by the throughput of the Nth user.
He set the channel weight of the Nth user to be a certain value and calculated the weights of other users by using the weight of the Nth user so that all users have the same rate and the scheme has the maximum sum rate. Then, he assumed that the sum rate does not depend on the number of users and the channel weight of the Nth user. Under this assumption, he calculated the optimal information transfer time to maximize the sum rate.
He compared the new scheme with the previous one in terms of the channel weight for the Nth user and information transfer time. The results showed that when the number of users in one source block is increased, the sum rate and user fairness are improved significantly.