Ofdm Adaptive Modulation And Coding Techniques

Orthogonal Frequency Division Multiplexing(OFDM) has become the key technology of wireless communications because of its high frequency efficiency and resistance of multi-path interference and frequency selective fading; Adaptive coded modulation can take full use of channel information, adjust sending parameter in time, optimize the overall performance of system, thus it has also widely used in modern wireless communication systems. Combining those two technologies can bring its own advantage into full play and meet the broadband and being smarter requirements of wireless communications, it is also the trend of future wireless communications.Adaptive coded modulation mode switching algorithm is the core technology of adaptive coded modulation on OFDM system, because it directly determines the performance of OFDM adaptive coded modulation system. This thesis point out some problems met in the adaptive coded modulation on OFDM sub-band and introduce several switching algorithm on coded modulation mode with some analysis and comparison. Then we propose a new switching algorithm on OFDM sub-band adaptive coded modulation, curves overlap algorithm.In order to testify the performance of switching algorithm on coded modulation in OFDM adaptive coded modulation system, we have built two OFDM adaptive coded modulation system with different bandwidth (60MHz and 8MHz) and detailed description on all the modules one after another. Finally, simulation and performance comparison for several switching algorithm on code modulation in the two systems are carried out. The results show that curves overlap algorithm can improve data transfer rate of the system a lot on the condition of meeting target error rate.