Joint Wireless Information and Energy Transfer in Cache-assisted Relaying Systems IEEE Wireless Communications and Networking Conference 2018 16 th April, 2018 Sumit Gautam , Thang X. Vu, Symeon Chatzinotas, Björn Ottersten {sumit.gautam, thang.vu, symeon.chatzinotas, bjorn.ottersten }@uni.lu Interdisciplinary Centre for Security, Reliability and Trust (SnT) University of Luxembourg, Luxembourg
Overview Joint Wireless Information and Energy Transfer in Cache-assisted Relaying Systems Introduction Sumit Gautam Thang X. Vu Symeon Chatzinotas System Model Björn Ottersten Basic Schema Introduction Transceiver Architecture System Model Basic Schema Definitions Transceiver Architecture Definitions Maximization of Maximization of Energy stored at the Relay Energy stored at the Relay Problem Formulation Problem Formulation Solution Solution Simulation Results Simulation Results Summary Summary 17
Introduction Joint Wireless ◮ The exponential increase in the usage of wireless devices Information and Energy Transfer in has not only posed substantial challenges to meet the per- Cache-assisted Relaying Systems formance and capacity demands, but also presented some Sumit Gautam Thang X. Vu serious environmental concerns with alarming CO 2 emis- Symeon Chatzinotas Björn Ottersten sions . ◮ By the end of 2020 , this number is expected to cross 50 Introduction 2 System Model billion . Basic Schema Transceiver Architecture ◮ Recent developments in IoTs emphasize on the intercon- Definitions nection between the devices, with or without slightest hu- Maximization of Energy stored at the man mediation. Relay Problem Formulation ◮ Most of these connecting operations involve battery-limited Solution Simulation Results devices that may not be continuously powered = ⇒ man- Summary agement of energy becomes crucial . ◮ In this work, we propose a novel framework to realize the benefit of Wi-TIE combined with caching capability to support future technologies. 17
System Model Joint Wireless Information and Energy Transfer in Cache-assisted Relaying Systems Sumit Gautam Thang X. Vu Symeon Chatzinotas Björn Ottersten Introduction System Model 3 Basic Schema SYSTEM MODEL Transceiver Architecture Definitions Maximization of Energy stored at the Relay Problem Formulation Solution Simulation Results Summary 17
System Model Wi-TIE with Caching at the DF Relay Joint Wireless Information and Energy Transfer in Cache-assisted Relaying Systems Sumit Gautam Thang X. Vu Symeon Chatzinotas Björn Ottersten Introduction System Model Basic Schema 4 Transceiver Architecture Definitions Maximization of Energy stored at the Relay Problem Formulation Solution Simulation Results Summary Figure: 1. System Model: We consider a generic Wi-TIE system in which a DF relay equipped with caching and Wi-TIE capabilities helps to convey information from one source to a destination. Due to limited coverage, there is not direct connection between the source and the destination. This model can find application on the downlink where the base station plays the source’s role and sends information to a far user via a small- or femto- cell base station. 17
System Model Proposed DF Relay Transceiver Design Joint Wireless Information and Energy Transfer in Cache-assisted Relaying Systems Sumit Gautam Thang X. Vu Symeon Chatzinotas Björn Ottersten Introduction Figure: 2. Proposed DF relay transceiver design for hybrid Wi-TIE and Caching with Time System Model Switching (TS) architecture. Basic Schema Transceiver Architecture 5 Definitions Maximization of Energy stored at the Relay Problem Formulation Solution Simulation Results Summary Figure: 3. Convention assumed for distribution of time to investigate the Maximization Problem of Energy stored at the Relay. 17
System Model Definitions Joint Wireless ◮ Denote P S and P R as the transmit power at the source and Information and Energy Transfer in at the relay, respectively. Cache-assisted Relaying Systems ◮ In addition, let g and h denote the channel gain between Sumit Gautam Thang X. Vu the source and the relay and the relay and the destination, Symeon Chatzinotas Björn Ottersten respectively. Introduction ◮ The signal received at the relay when the transmitter trans- System Model mits the symbols x ∈ C , such that E {| x | 2 } = 1 where E {·} Basic Schema Transceiver Architecture and | · | denotes the statistical expectation and the norm Definitions 6 respectively, is given by Maximization of Energy stored at the Relay � y R = P S g x + m . (1) Problem Formulation Solution Simulation Results ◮ Upon receiving y R , the relay decodes and re-encodes the Summary source’s signal to obtain the estimate ˜ x , which is then for- warded to the destination. The signal received at the desti- nation is given by � P R h ˜ y D = x + n . (2) 17
System Model Definitions Joint Wireless ◮ The achievable information rate of the source-relay link is Information and Energy Transfer in � � 1 + P S | g | 2 Cache-assisted Relaying Systems R 1 = B log 2 , (3) σ 2 Sumit Gautam m Thang X. Vu Symeon Chatzinotas Björn Ottersten where B is the channel bandwidth. ◮ When the destination request a file from the library, δ part of that Introduction System Model file is already available at the relay’s cache. Basic Schema ◮ In other words, the relay’s cache can provide, in addition to the Transceiver Architecture Definitions 7 source-relay link, a cache rate Maximization of Energy stored at the R 2 = δ r . (4) Relay Problem Formulation ◮ The achievable information rate of the relay-destination link is Solution Simulation Results � � 1 + P R | h | 2 Summary R 3 = B log 2 (5) . σ 2 n ◮ The harvested energy at the relay is given by E R = ζθ ( P S | g | 2 + σ 2 m ) . (6) 17
Maximization of Energy stored at the Relay Joint Wireless Information and Energy Transfer in Cache-assisted Relaying Systems Sumit Gautam Thang X. Vu Symeon Chatzinotas Björn Ottersten MAXIMIZATION OF Introduction System Model Basic Schema Transceiver Architecture ENERGY STORED AT Definitions Maximization of 8 Energy stored at the Relay THE RELAY Problem Formulation Solution Simulation Results Summary 17
Problem Formulation for Maximization of the Energy stored at the Relay (P1) Joint Wireless ◮ PROBLEM : We represent the overall optimization problem as Information and Energy Transfer in [ ζθ ( P S | g | 2 + σ 2 m ) − ( 1 − ( θ + φ )) P R ] + ( P 1 ) : max (7) Cache-assisted Relaying Systems θ,φ, P R Sumit Gautam subject to ( C 1 ) : φ ( R 1 + R 2 ) ≥ ( 1 − ( θ + φ )) R 3 , (8) Thang X. Vu Symeon Chatzinotas ( C 2 ) : ( 1 − ( θ + φ )) P R ≤ E R + E ext , (9) Björn Ottersten ( C 3 ) : ( 1 − ( θ + φ )) R 3 ≥ r , (10) Introduction System Model ( C 4 ) : 0 < P S ≤ P ⋆ , (11) Basic Schema Transceiver Architecture ( C 5 ) : 0 ≤ θ + φ ≤ 1 . (12) Definitions Maximization of ◮ Here, the objective function of (P1) is the expression of the overall Energy stored at the Relay energy stored at the relay, (C1) ensures the requested data fulfill- Problem Formulation 9 ment at the destination, (C2) safeguards the power management Solution Simulation Results at the relay, and (C3) denotes the QoS constraint. Summary ◮ Clearly, this is a non-linear programming problem involving joint computations of θ , φ and P R , which introduces intractability. ◮ Therefore, we propose to solve this problem using the Karush- Kuhn-Tucker (KKT) conditions. 17
Solution obtained using the KKT Joint Wireless ◮ We denote the Lagrangian of (P1) as follows Information and Energy Transfer in Cache-assisted L ( θ, φ, P R ; λ 1 , λ 2 , λ 3 , λ 4 ) = F ( θ, φ, P R ) − λ 1 · G ( θ, φ, P R ) Relaying Systems Sumit Gautam − λ 2 · H ( θ, φ, P R ) − λ 3 · I ( θ, φ, P R ) − λ 4 · J ( θ, φ, P R ) , (13) Thang X. Vu Symeon Chatzinotas Björn Ottersten where Introduction F ( θ, φ, P R ) = [ ζθ ( P S | g | 2 + σ 2 m ) − ( 1 − ( θ + φ )) P R ] + , (14) System Model Basic Schema Transceiver Architecture G ( θ, φ, P R ) = ( 1 − ( θ + φ )) log 2 ( 1 + γ R , D ) Definitions − φ [ log 2 ( 1 + γ S , R ) + δ r ] ≤ 0 , (15) Maximization of Energy stored at the Relay H ( θ, φ, P R ) = ( 1 − ( θ + φ )) P R − ζθ ( P S | g | 2 + σ 2 m ) Problem Formulation Solution 10 − E ext ≤ 0 , (16) Simulation Results Summary I ( θ, φ, P R ) = r − ( 1 − ( θ + φ )) log 2 ( 1 + γ R , D ) ≤ 0 , (17) J ( θ, φ, P R ) = ( θ + φ ) − 1 ≤ 0 , (18) with γ S , R = P S | g | 2 and γ R , D = P R | h | 2 . σ 2 σ 2 17 m n
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