"Multi-antenna Interference Management for Coded Caching"

Antti Tolli, Adjunct Professor, EE, University of Oulu

April 13th (Friday), 10:00am
Harold Frank Hall (HFH), Rm 4164

In Coded Caching (CC), instead of simply replicating high-popularity contents near-or-at end-users, the network should spread different contents at different caches such that common coded messages broadcast during the network high-peak hours to different users with different demands would benefit all the users simultaneously. In this talk, a single cell downlink scenario is considered where a multiple-antenna base station delivers contents to multiple cache-enabled user terminals. Most of the existing work for wireless CC focus on the Degrees-of-Freedom (DoF) analysis in the high Signal-to-Noise-Ratio (SNR) regime. Using the ideas from multi-server coded caching scheme developed for wired networks, a joint design of CC and general multicast beamforming is proposed to benefit from spatial multiplexing gain, improved interference management and the global CC gain, simultaneously. Utilizing the multiantenna multicasting opportunities provided by the CC technique, the proposed method is shown to perform well over the entire SNR region, including the low SNR regime, unlike the existing DoF optimal schemes based on zero forcing (ZF). Instead of nulling the interference at users not requiring a specific coded message, general multicast beamforming strategies are employed, optimally balancing the detrimental impact of both noise and inter-stream interference from coded messages transmitted in parallel. The proposed scheme is shown to provide the same degrees-of-freedom at high SNR as the state-of-art methods and, in general, to perform significantly better than several base-line schemes including, the joint ZF and CC, max-min fair multicasting with CC, and basic unicasting with multiuser beamforming.

About Antti Tolli:

photo of Antti Tolli Antti Tolli (M'08, SM'14) received the Dr.Sc. (Tech.) degree in electrical engineering from the University of Oulu, Oulu, Finland, in 2008. Before joining the Centre for Wireless Communications (CWC) at the University of Oulu, he worked for 5 years with Nokia Networks as a Research Engineer and Project Manager both in Finland and Spain. In May 2014, he was granted a five year (2014-2019) Academy Research Fellow post by the Academy of Finland. He also holds an Adjunct Professor position with University of Oulu. During the academic year 2015-2016, he visited at EURECOM, Sophia Antipolis, France. He has authored more than 140 papers in peer-reviewed international journals and conferences and several patents all in the area of signal processing and wireless communications. His research interests include radio resource management and transceiver design for broadband wireless communications with a special emphasis on distributed interference management in heterogeneous wireless networks. He is currently serving as an associate editor for IEEE Transactions on Signal Processing.

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