Expand LTE Network Spectrum with Cognitive Radios -- From Research to Implementation
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Wireless data traffic is growing extraordinarily, with new wireless devices such as smart phones and bandwidth-demanding wireless applications such as video streaming becoming ever increasingly popular and widely adopted. Correspondingly, we have also witnessed the phenomenal wireless technology evolutions to support higher system capacities from generation to generation. Long Term Evolution (LTE) has been developed as 4G wireless technology that can support next generation multimedia applications with high capacity and high mobility needs. However, the peak data rate from 3G UMTS to 4G LTE-Advanced only increases 55% annually while global mobile traffic increases 66 times with an annual growth rate of 131% between 2008 and 2013. Clearly there is a huge gap between the growth rate of new air interface and the growth rate of consumer's needs. A promising way to alleviate the contention between the actual traffic demands and the actual system capacity growth is to exploit more available spectrum resources. Recently, cognitive radio (CR) technology has been under extensive research and study. It aims to provide abundant new spectrum opportunities by exploiting under-utilized or un-utilized spectrum opportunistically. In this paper, we discuss the technical solutions to expand LTE spectrum with CR technology (LTE-CR), and survey the advances in LTE-CR from both research and implementation aspects. We present detailed key technologies that enable LTE-CR in TVWS, we have conducted extensive system level simulation and also developed a LTE-CR prototype. Both simulation and lab testing results show that applying LTE-CR in TVWS can achieve satisfactory performance.