Physical Layer Caching in 5G Wireless Networks
09:30 am
Room 4475 (Lifts 25-26), 4/F Academic Building, HKUST

Thesis Examination Committee

Prof Christopher Kin Ying LEUNG, CIVL/HKUST (Chairperson)
Prof Vincent LAU, ECE/HKUST (Thesis Supervisor)
Prof Lin DAI, Department of Electronic Engineering, City University of Hong Kong (External Examiner)
Prof Chin-Tau LEA, ECE/HKUST



The spectral efficiency of small-cell wireless networks is limited by the severe interference from the neighboring base stations (BSs) as well as the backhaul capacity of the BSs. In this thesis, we propose a physical layer (PHY)-caching scheme to address these two issues. To address the interference issue, by properly caching some popular contents at the BSs, the proposed PHY-caching can opportunistically transform the topology of the radio access network from an unfavorable topology (e.g., relay or interference topology) into a more favorable multiple-input and multiple-output (MIMO) broadcast topology and enjoy spectrum efficiency gain without large backhaul consumption. To address the backhaul issue, we consider to exploit spatial caching diversity (i.e., caching different subsets of popular content files at neighboring BSs) that can greatly improve the cache hit probability, thereby leading to a better overall system performance. A key issue in exploiting spatial caching diversity is that the cached content may not be located at the nearest BS, which means that to access such content, a user needs to overcome strong interference from the nearby BSs. We propose a joint design of frequency reuse and caching, such that the benefit of an improved cache hit probability induced by spatial caching diversity and the benefit of interference coordination induced by frequency reuse can be achieved simultaneously. Moreover, we propose an interference-aware dual-mode caching and user-centric open-loop cooperative transmission scheme that embraces spatial caching diversity and user-centric open-loop cooperative transmission, and alleviate the interference issue in the system. For each of the above proposed schemes, we study corresponding parameter optimizations that maximize the spectral efficiency benefits, and quantify the benefits with respect to some important system parameters. The proposed solution for each problem is compared with some state-of-the-art baselines, and it is shown through simulations that significant performance gain can be achieved.

09:30 am
Room 4475 (Lifts 25-26), 4/F Academic Building, HKUST
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