Based on the popular orthogonal frequency division multiplexing (OFDM), frequency division multiple access (OFDMA) has emerged as a primary multi-user multiple access scheme in broadband wireless communication systems. In this paper, recent patents on resource allocation techniques in OFDMA-based wireless systems are overviewed. Specifically, we use single cell single input single output (SISO) as the base model and discuss inventions on OFDMA resource allocation in single cell, multi-cell, multiple input multiple output (MIMO), relay and cognitive radio scenarios. As the new multiple access scheme, OFDMA has many advantages over its predecessor CDMA. These patents demonstrate how to exploit the full potential of OFDMA by efficient subcarrier and power allocation in practical wireless communication systems. Finally, this paper forecasts that resource allocation for cooperative systems, hybrid systems, and cognitive Ad Hoc networks will be future research directions. This overview paper aims to provide valuable insight to OFDMA fundamentals for both system engineers and research scholars.