Dynamic spectrum wireless communication system

Recently, several researches show that the current spectrum allocation results in considerably inefficient spectrum utilization．Therefore, the need to utilize the spectrum flexibly, dynamically, and opportunistically is highly preferred．Dynamic Spectrum Access (DSA) emerges as novel solution to answer the inefficient spectrum allocation problem．DSA is made possible with the advance of radio technology such as software defined radio．Enabling DSA to be implemented in real wireless network though, is not a trivial matter．Conventional wireless network protocol will not work with DSA．Therefore, new wireless network protocol for DSA has attracted considerable interest in research field recently.
We have researched the Opportunistic Spectrum Access (OSA) scheme where Secondary User (SU) is able to opportunistically access Primary User (PU) spectrum bands．We are able to discover the impact of hops number, PU idle duration, and multiple physical data rate to the SU performance．Furthermore, we have proposed a physical rate adaptation algorithm called Auto Rate Increase (ARI) for OSA scheme．ARI aims to select the best link rate under multi-hop and tight PU idle duration for WLAN devices．Simulation results show that ARI can achieve considerable performance increase compared with conventional rate adaptation algorithm．Future research directions include coupling ARI with low overhead routing protocol to further improve the performance and modeling the reactive PU system for PU-SU WLAN bands.