Adaptive modulation and resource allocation in OFDM systems

Abstract

The aim of this project is to explore the adaptive modulation and resource allocation in orthogonal frequency-division multiplexing (OFDM) systems. As a digital data encoding scheme on multiple subcarrier frequencies, OFDM profits from its relatively high efficiency, low power consumption and high resistance to interference, stands out from the crowd and occupies an important position in wideband digital communication. Along with the arisen of 4G mobile communications, how to optimize its modulation scheme and resource allocation becomes a hot issue. This paper can be broken into two parts, discussing scheme optimization for single user and multiuser. For single user, target transmitting rate is fixed and the objective is to minimize total power, simple resource allocation algorithms was proposed and compared with traditional bit loading scheme. Their bit error performance comparison indicated that they have same performance and proposed resource allocation algorithms are simpler; for multiuser, efficiency performance of OFDM with sum power constraint and Time Division Multiple Address (TDMA) were compared. Result indicated that multiuser OFDM outperforms multiuser TDMA a lot. These findings showed that adaptive modulation and resource allocation can achieve better performance compared with traditional fixed power and fixed rate allocation.