Browsing by Author "Li, Yonghui"
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Item Full duplex cognitive radio: a new design paradigm for enhancing spectrum usage(IEEE Communications Magazine, 5/14/2015) Liao, Yun; Song, Lingyang; Han, Zhu; Li, YonghuiWith the rapid growth of demand for ever increasing data rates, spectrum resources have become more and more scarce. As a promising technique to increase the efficiency of the spectrum utilization, cognitive radio has great potential to meet such a requirement by allowing unlicensed users to coexist in licensed bands. In conventional CR systems, spectrum sensing is performed at the beginning of each time slot before data transmission. Unfortunately, this results in two major problems: transmission time reduction due to sensing, and sensing accuracy impairment due to data transmission. To tackle these problems, in this article we present a new design paradigm for future CR by exploring full duplex techniques to achieve simultaneous spectrum sensing and data transmission. With FD radios equipped at secondary users (SUs), the SUs can simultaneously sense and access the vacant spectrum, and thus significantly improve sensing performance while increasing data transmission efficiency. The aim of this article is to transform the promising conceptual framework into a practical wireless network design by addressing a diverse set of challenges such as protocol design and theoretical analysis. Several application scenarios with FD-enabled CR are elaborated, and key open research directions and novel algorithms in these systems are discussed.Item V2X Meets NOMA: Non-Orthogonal Multiple Access for 5G-Enabled Vehicular Networks(IEEE Wireless Communications, 2017-12) Di, Boya; Song, Lingyang; Li, Yonghui; Han, ZhuBenefiting from widely deployed infrastructure, the LTE network has recently been considered as a promising candidate to support vehicle-to-everything (V2X) services. However, with a massive number of devices accessing the V2X network in the future, the conventional OFDM-based LTE network faces congestion issues due to its low efficiency of orthogonal access, resulting in significant access delay and posing a great challenge especially to safety-critical applications. The non-orthogonal multiple access (NOMA) technique has been well recognized as an effective solution for the future 5G cellular networks to provide broadband communications and massive connectivity. In this article, we investigate the applicability of NOMA in supporting cellular V2X services to achieve low latency and high reliability. Starting with a basic V2X unicast system, a novel NOMAbased scheme is proposed to tackle the technical hurdles in designing high spectrally efficient scheduling and resource allocation schemes in the ultra-dense topology. We then extend it to a more general V2X broadcasting system. Other NOMA-based extended V2X applications and some open issues are also discussed.