OFDM for Future Wireless Systems

  • Rahman, Muhammad Imadur, (Projektdeltager)



The nature of Wireless Local Area Networks (WLAN) and Wireless Personal Area Networks (WPAN) applications demands high datarates. Naturally dealing with ever-unpredictable wireless channel at high data rate communications is not an easy task. So, the idea of multicarrier transmission has surfaced recently to be used for combating the hostility of wireless channel. OFDM is a special form of multicarrier transmission where all the subcarriers are orthogonal to each other. OFDM promises a higher user data rate transmission capability at a reasonable complexity and precision. Future telecommunication systems must be very efficient spectrally to support number of users with high data rate. OFDM uses the available spectrum very efficiently. This is very useful for multimedia communications. Thus, OFDM stands a good chance to become the prime technology for 4G. Pure OFDM or hybrid OFDM will be most likely the choice for physical layer multiple access technique in the future generation of telecommunications systems. OFDM has a long history of presence in wireless arena. Though the idea was first generated during the second world war mainly for military communications, in recent years OFDM is adopted for several standards related to broadcasting and wireless data applications. Broadcast systems, such as Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB), were the first public wireless systems to use OFDM. Recently IEEE 802.11a, HiperLAN/2 and MMAC WLAN standards have also followed the suit. Perhaps the greatest milestone in OFDM history is the emergence of the OFDM technology as a competitor to the future generations of wireless systems. These future systems, expected to emerge by the year 2010, promise to eventually deliver on the wireless Nirvana of anywhere, anytime, anything communications. Should OFDM gain prominence in this arena, and telecom giants are banking on just this scenario, then OFDM will become the technology of choice in most wireless links worldwide 4G systems will not only be characterized by a higher data rate than existing wireless systems, but also will be specified as having higher mobility and better link quality. The current systems will undoubtedly fail in meeting these added requirements on system performance. Thus, an enormous demand for research to find out new ideas and technologies are present. Channel modeling will be the first and foremost task for designing future OFDM systems. High-data rate systems will require an amalgamation of MIMO and OFDM techniques. So, some of the main focuses of the PhD work are diversity introduction; and capacity enhancement via MIMO signaling techniques. Synchronization and channel estimation issues will continue to be one of the core issues to be solved in next generation OFDM systems. The main goal of the research around these topics will be finding low complexity and power efficient algorithms. Finally, feasible implementation of the studied techniques will be considered at the last phase of the PhD studies. At the very beginning of the studies, considerable amount of time will be spent to master the knowledge in and around the research area. Extensive literature studies will be performed. This will be supported by some selected PhD level courses, which will be attended whenever available. Number of research publications will be made and presented in various forums to establish, investigate and validate the research work. (Muhammad Imadur Rahman & Suvra Sekhar Das)
Effektiv start/slut dato31/12/200431/12/2004