Secure and reliable transmission mechanism for orthogonal frequency-division multiple access worldwide interoperability for microwave access systems

The most challenging technical issue in worldwide interoperability for microwave access (WiMAX) networks is to find a way to counteract the interference as well as to solve the fading problem in transmissions. Although IEEE 802.16e standard proposes several mechanisms to handle this difficult problem, there are still many external interferences that may collapse ongoing transmissions. To tackle this thorny problem, the authors develop a method called fault-tolerant transmission mechanism (FTM), which re-permutes and scatters slots in each frame space of the downlink transmission in the medium access control (MAC) layer to achieve a higher probability of success in transmissions. FTM can produce approximately 30% more throughput than the IEEE 802.16 standard can and significantly raise the successful transmission probability, while having each transmitted burst size limited to no more than 20 slots (5% of the total downlink frame space). Therefore by adjusting the burst size, rearranging slot places and comparing their patterns, FTM can provide a more reliable, more secure and more efficient transmission mechanism than IEEE 802.16e transmission mechanism. In addition, it is fully compatible with orthogonal frequency-division multiple access (OFDMA) WiMAX systems.