Unified models for adaptive OFDM systems when QAM or PSK modulation is applied

In this paper, the solutions of the major bit-loading problems that are found in the literature, are unified into simple equations (models). These equations give an insight of the affection of the channel over a multicarrier system. Moreover, the models allow the transition from the solution of one loading problem to the solution of the others. The models are dependent on the modulation type that is used. We examine the quadrature amplitude modulation (QAM) modulated orthogonal frequency division multiplexing (OFDM), and the phase shift keying (PSK)-modulated OFDM systems. For each modulation type, the continuous throughput model is extracted. The continuous throughput model refers to a system that its subcarriers can be loaded with non-integer number of bits. The non-integer bit distribution can then be rounded to integers, using a rounding method. The models except from the calculation of the optimised quantities (total data rate, total power and symbol error rate) without the need of running a loading algorithm to its extent, provide a means to manipulate a whole multicarrier system in a way similar to single-carrier system. Copyright (c) 2007 John Wiley & Sons, Ltd.