Coded Caching Under Asynchronous Demands

The work focuses on optimizing coded caching under asynchronous demands. We consider a single-stream setting where users are allowed to request content at arbitrary time-slots. Aiming to minimize the total system delay required to serve all users, i.e. from the moment of the first request to the delivery of the last bit of requested information, we design a pair of placement and delivery algorithms and show that the achievable performance is within a multiplicative factor of 2 from the optimal, under the assumption of uncoded placement, and within a multiplicative factor of 4.02 in the general placement case. Interesting characteristics of our algorithms are that i) a placement phase agnostic to the users' arrival times is adequate to provide a near-optimal delay, and ii) the proposed delivery algorithm requires low complexity and, at the same time, requires no non-causal information. Further, we show that systems are able to withstand some degree of asynchronicity without an increase in the delay compared to an equivalent synchronous setting. Finally, we highlight an interesting connection between coded caching under asynchronous demands and coded caching in wireless environments under uneven channel strengths.