ormation.РMore powerful smartphones and laptops areРing more popular nowadays, demandingРadvanced multimedia capabilities. This hasРresulted in an explosion of wireless mobileРdevices and services. The EMO pointed out thatРthere has been a 92 percent growth in mobileРbroadband per year since 2006 [2]. It has beenРpredicted by the Wireless World ResearchРForum (WWRF) that 7 trillion wireless devicesРwill serve 7 billion people by 2017; that is, theРnumber work-connected wireless devicesРwill reach 1000 times the world’s population [4].РAs more and more devices go wireless, manyРresearch challenges need to be addressed.РOne of the most crucial challenges is theРphysical scarcity of radio frequency (RF) spectraРallocated for munications. CellularРfrequencies use ultra-high-frequency bands for
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