42 filling algorithm (explained in section 3.1). In , Yin and Liu simulate their algorithm and show that it outperforms OFDM-TDMA in terms of achievable rate and outage probability. Their results clearly show the advantages of OFDMA over OFDM-TDMA. By considering the different channel gains seen by different users at any given time, OFDMA outperforms standard OFDM-TDMA. Despite their great results, their algorithm suffers from having a high computational complexity of O ( N 4 ). In , Rhee and Cioffi attempt to overcome this drawback by developing an algorithm with a lower computational complexity. Instead of maximizing the total data rate,  uses the RA approach to maximize the minimum of each user’s data rate. Rhee and Cioffi allow the variable c m,n (defined by equation E15) to assume any real value in between 0 and 1, instead of binary 0 or 1. This simple change turns the resource allocation problem into a typical convex optimization problem. As was explained before, convex
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