OFDMA in the Field-Current and Future Challenges
Orthogonal Frequency Multiplex Division (OFDM) and the corresponding multiple access scheme OFDM-Access (OFDMA) is the result of an evolution spanning decades of digital transmission techniques and advances in the digital signal processing methods and technologies [1]. Initial applications of OFDM were used for broadcast systems. First, it was adopted for digital radio and video broadcasting standards in Europe for the Digital Audio Broadcasting (DAB) system in 1995 and the Digital Video Broadcasting-Terrestrial system (DVB-T) in 1997. Soon after, OFDM technology found its way into wireless standards such as research 802.11a for wireless LAN and the European HiperLAN project in 1999, research 802.16 in 2001 and Mobile WiMAX in 2005. Today OFDMA is selected for all future broadband wireless systems in recognition of its proven advantages for broadband wireless transport. In this article we focus on one of the main applications of OFDMA technology as air interface technology for current and future mobile wireless broadband access systems. The next section provides a brief overview of the evolution of mobile communication systems towards OFDMA and an introduction of the basic principles. In the remaining part of the article, we present challenges faced in the deployment of such systems in the field and we look at some of the solutions used to defuse these challenges.