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Title: Fundamental limits of robust interference management : from content-oblivious to content-aware wireless networks
Author: Piovano, Enrico
ISNI:       0000 0004 9350 8531
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2020
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In this thesis we progress towards the understanding of the fundamental limits of wireless networks with partial instantaneous channel state information at the transmitter (CSIT). We first consider classical content-oblivious networks, where the edge-nodes are unaware of the kind of requested content. We study the K-user multiple-input-single-output (MISO) broadcast channel (BC), where a K-antenna transmitter serves K single-antenna users, and we characterize the optimal degrees-of-freedom (DoF) region under arbitrary CSIT levels for the users. We then study the overloaded MISO BC with two groups of CSIT qualities. We propose a transmission scheme where no CSIT codewords are superimposed on top of spatially-multiplexed codewords. We show that the developed strategy outperforms the existing schemes and achieves the entire DoF region. Next, we move from content-oblivious networks to content-aware networks, where the edge-nodes can predict the most popular content. We first consider the K-user cache-aided MISO BC, where users are equipped with a cache memory. For a symmetric setting, in terms of channel strength levels, partial channel knowledge levels and cache sizes, we characterize the sum-generalized-degrees-of-freedom (sum-GDoF) up to a constant multiplicative factor of 12. We further show that the characterized order-optimal sum-GDoF is also attained in a decentralized setting, where no coordination is required for content placement in the caches. We then study the cache-aided interference channel, where an arbitrary number of cache-equipped transmitters serve an arbitrary number of cache-equipped receivers. Transmitters communicate with receivers over two heterogenous parallel subchannels: one with perfect CSIT, and the other with no CSIT. Under the assumptions of uncoded placement and separable one-shot linear delivery over the two sub-channels, we characterize the optimal sum-DoF to within a constant multiplicative factor of 2. We extend the result to decentralized setting, and we characterize the optimal one-shot linear sum-DoF to within a factor of 3.
Supervisor: Clerckx, Bruno Sponsor: Imperial College London ; Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral