Minimizing File Transfer Time in Opportunistic Spectrum Access Model

TL;DR

This paper investigates minimizing file transfer time in opportunistic spectrum access with heterogeneous channels, proposing optimal policies, heuristics, and extensions to Markovian channels, supported by simulations.

Contribution

It introduces a new framework for minimizing transfer time, contrasting with throughput-focused methods, and develops efficient algorithms including a heuristic for practical online use.

Findings

Max-throughput policy does not minimize transfer time.

Proposed policies significantly reduce transfer time compared to baseline.

Performance is affected by channel correlation and switching delays.

Abstract

We study the file transfer problem in opportunistic spectrum access (OSA) model, which has been widely studied in throughput-oriented applications for max-throughput strategies and in delay-related works that commonly assume identical channel rates and fixed file sizes. Our work explicitly considers minimizing the file transfer time for a given file in a set of heterogeneous-rate Bernoulli channels, showing that max-throughput policy doesn't minimize file transfer time in general. We formulate a mathematical framework for static extend to dynamic policies by mapping our file transfer problem to a stochastic shortest path problem. We analyze the performance of our proposed static and dynamic optimal policies over the max-throughput policy. We propose a mixed-integer programming formulation as an efficient alternative way to obtain the dynamic optimal policy and show a huge reduction in computation time. Then, we propose a heuristic policy that takes into account the performance-complexity tradeoff and consider the online implementation with unknown channel parameters. Furthermore, we present numerical simulations to support our analytical results and discuss the effect of switching delay on different policies. Finally, we extend the file transfer problem to Markovian channels and demonstrate the impact of the correlation of each channel.