Energy-Aware Opportunistic Mobile Data Offloading Sylvia Kouyoumdjieva and Gunnar Karlsson ITC28, COST Action ACROSS on "Quality Engineering for a Reliable Internet of Services"  Würzburg, 2016-09-16

Opportunistic Mobile Data Offloading Goal: Minimize traffic volumes in the cellular network. Assumption 1: Nodes have infinite battery capacity! Assumption 2: Nodes are altruistic!

Opportunistic Mobile Data Offloading (2) Goal: Deliver satisfactory application throughput at a low energy price. Realistic assumption 1: Nodes have limited battery capacity! Realistic assumption 2: Nodes are selfish!

Data-seeking vs Data-fulfilled Nodes Data-seeking node: Node that is still in search for contents Objective: Obtain all content items at a low energy cost Data-fulfilled node: Node that has obtained all content items Objective: Contribute to data dissemination at a low(est) energy cost

Data-seeking (Searches for data) Data-seeking Nodes Duty cycling [1] Cycling interval Tc Listening duration d ~ Uni(0, Tc) Data-seeking (Searches for data) [1] S.T. Kouyoumdjieva, G. Karlsson,  Impact of Duty Cycling on Opportunistic Communication, in Mobile Computing, IEEE Transactions on, vol.15, no.7, pp. 1686 - 1698, July 2016

Data-fulfilled Nodes Strict Selfishness Node opts out of dissemination process after it obtains all content items. Progressive Selfishness [2] Node behaves in a progressively selfish manner after it obtains all content items. w, inactivity window [2] S.T. Kouyoumdjieva, G. Karlsson, Energy-aware opportunistic mobile data offloading under full and limited cooperation, in Elsevier Computer Communications, vol. 84, pp. 84-95, June 2016

Is Duty Cycling Really Needed? Configuration Energy Goodput ON-SS, p = 10% 56.3% 86.2% DC-SS, p = 10% 30.4% 82.8% ON-SS, p = 100% 20.8% 98.3% DC-SS, p = 100% 11.5% 97.4% +26% -4% ON-SS Nodes are always listening while data-seeking then become strictly selfish when data-fulfilled DC-SS Nodes duty cycle while data seeking then ditto p – percentage of participating nodes in dissemination process [3] S.T. Kouyoumdjieva, G. Karlsson, The Virtue of Selfishness: Device Perspective on Mobile Data Offloading, in Proc. IEEE WCNC 2015

Evaluation Scenarios: Mobility Subway Station Östermalm Characteristics: 12 entry points High mobility scenario Area: 5872 m2 Characteristics: 5 entry points Burstiness and queuing Area: 1921 m2 Legion Studio – designing and dimensioning large-scale spaces via simulation of pedestrian behaviors Traces are available at: http://crawdad.org/kth/walkers/

Evaluation Scenarios: Metrics Goodput (Application throughput) How much data is offloaded? Energy Consumption How much energy is consumed in comparison to a direct cellular download? Initial content availability q Amount of data initially injected into a node’s cache Injection probability pi Probability that a node obtains contents by the operator upon entering the area

Evaluation Scenarios: Configurations ON – Nodes do not apply any energy saving mechanisms DC – Nodes duty cycle while data-seeking and data-fulfilled DC-SS – Nodes duty cycle while data-seeking and become strictly selfish when data-fulfilled DC-PS – Nodes duty cycle while data-seeking and become progressively selfish when data-fulfilled

Evaluation Scenarios: Cooperation Full Cooperation All nodes in the system follow the progressive selfishness algorithm. Limited Cooperation A subset of nodes are entirely egocentric; non- cooperative nodes only consume resources of other peers in the network without contributing to the data dissemination.

Performance under Full Cooperation

Östermalm: Effect of Node Density (1) * S.T. Kouyoumdjieva, G. Karlsson, Energy-Aware Opportunistic Mobile Data Offloading for Users in Urban Environments, in Proc. IFIP/TC6 Networking, Toulouse, France, May 2015

Enhanced Progressive Selfishness (1)

Enhanced Progressive Selfishness (2)

Östermalm w/ λ = 0.01 n/s: Effect of Initial Content Availability (1)

Östermalm w/ λ = 0.15 n/s: Effect of Initial Content Availability (2)

Subway: Effect of Injection Probability

Performance under Limited Cooperation

Östermalm w/ λ = 0.01 n/s: Effect of Node Density (1)

Östermalm w/ λ = 0.15 n/s: Effect of Node Density (2)

Östermalm w/ λ = 0.15 n/s: Effect of Injection Probability (1)

Östermalm w/ λ = 0.15 n/s: Effect of Injection Probability (2) Goodput Energy consumption

Conclusions We examined the performance in terms of goodput and energy consumption of direct D2D communication in the context of opportunistic mobile data offloading with nodes under full and limited cooperation. We introduced progressive selfishness on top of duty cycling. Energy savings from opportunistic communication up to 90% without significant loss in goodput. Total energy consumption comparable to that consumed by nodes when downloading data _directly_ from the cellular network. Tolerance for up to 50% of non-cooperative nodes without significantly deteriorating goodput and energy consumption at a system level.

References [1] S.T. Kouyoumdjieva, G. Karlsson,  Impact of Duty Cycling on Opportunistic Communication, in Mobile Computing, IEEE Transactions on, vol.15, no.7, pp. 1686 - 1698, July 2016 [2] S.T. Kouyoumdjieva, G. Karlsson, Energy-Aware Opportunistic Mobile Data Offloading under Full and Limited Cooperation, in Elsevier Computer Communications, vol. 84, pp. 84-95, June 2016 [3] Ó. Helgason, S.T. Kouyoumdjieva, G. Karlsson, Opportunistic Communication and Human Mobility, in Mobile Computing, IEEE Transactions on, vol.13, no.7, pp.1597-1610, July 2014 [4] Mobility traces: http://crawdad.org/kth/walkers/