OFDM for Cognitive Radio Systems: Novel Power Allocation and Bit Loading Algorithms

Adaptive Subcarrier Allocation and Bit Loading for Multiuser OFDM Systems

This paper proposes a new algorithm of adaptive subcarrier allocation and bit loading for simultaneous voice and data transmission in multiuser OFDM systems. The algorithm dynamically assigns the number of subcarriers and bits/per symbol on each subcarrier for each user in a single cell. To cope with the stringent delay requirement of voice service, the subcarriers with low channel gains are as...

X Power Allocation in OFDM-Based Cognitive Radio Systems

Power Allocation in OFDM-Based Cognitive Radio Systems

In this thesis, we develop an subcarrier transmission suboptimal power allocation algorithm and an underlay subcarrier transmission optimal power allocation algorithm for the orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems with different statistical interference constraints imposed by different primary users (PUs). Given the fact that the interference constr...

Bit Loading Algorithms for Adaptive OFDM Wireless Systems

The main goal of next generation wireless systems is to provide multimedia communication with spectrally efficient communication. Most of the up-to-date systems have been standardised to use OFDM modulation which prevents inter-symbol interference and make use of parallel subcarriers. The large number of subcarriers helps to avoid the effects of fast fading by distributing channel coded informa...

Efficient Power Loading in MIMO-OFDM Based Cognitive Radio Networks

Due to their spectrum shaping capability and high adaptability, the multi-carrier systems are considered as prime candidates for use in the Cognitive Radio (CR) networks. In these structures, the deactivation of the primary users’ (PUs) bands makes the secondary users (SUs) use a limited number of sub-carriers, so the total capacity of CR networks is reduced. However, multiple transmit antennas...