Title: A Data Rate Maximization Algorithm for Multiuser OFDM Systems
Authors: Zeljko Ilic, Alen Bazant
Abstract: In this paper, we consider multiuser orthogonal frequency division multiplexing (OFDM) systems with adaptive algorithm that maximizes the total data rate in downlink transmission. Assuming knowledge of the instantaneous channel gains for all users, we propose a new multiuser OFDM subcarrier, bit, and power allocation loading algorithm, with constrains, that maximizes the total data rate taking the users requests on the minimum SNR (Signal-to-Noise Ratio) on each subcarrier. This is done by solving the maximization problem via two steps: subcarrier assignment for users, and bit and power allocation for subcarriers. In order to reduce the computational complexity of the proposed problem we propose a simple method, in the form of a theorem, which assignes subcarriers to users and distributes bits and power among them. We tested the proposed algorithm in a multiuser environment for various subcarrier SNR values requested by users, and for various levels of intereference in the OFDM system. The results show that our loading method obtains a better data rate in some situations than the algorithm described in [5], which states that the data rate of a multiuser OFDM system is maximized when each subcarrier is assigned to only one user. Results show that the total number of bits per OFDM symbol or data rate grows with the number of users in the system.