Driven by growing spectrum shortage, Long-term Evolution in unlicensed spectrum (LTE-U) has recently been proposed as a new paradigm to deliver better performance and experience for mobile users by extending the LTE protocol to unlicensed spectrum. In the paper, we first present a comprehensive overview of the LTE-U technology, and discuss the practical challenges it faces. We summarize the existing LTE-U operation modes and analyze several means for LTE-U coexistence with Wi-Fi medium access control protocols. We further propose a novel hyper access-point (HAP) that integrates the functionalities of LTE small cell base station and commercial Wi-Fi AP for deployment by cellular network operators. Our proposed LTE-U access embedding within the Wi-Fi protocol is non-disruptive to unlicensed Wi-Fi nodes and demonstrates performance benefits as a seamless and novel LTE and Wi-Fi coexistence technology in unlicensed band. We provide results to demonstrate the performances advantage of this novel LTE-U proposal.
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