Offloading in Heterogeneous Networks: Modeling, Analysis, and Design Insights

TLDR

Offloading data traffic from cellular to WiFi can relieve cellular congestion, yet its overall impact on system performance remains poorly understood. The study seeks to create a tractable model for inter‑RAT offloading across multiple RATs and AP tiers to assess system performance. The authors model each AP tier as an independent Poisson point process, users as another PPP, with i.i.d. Rayleigh fading, and derive the network rate distribution under a weighted association strategy.

Abstract

Pushing data traffic from cellular to WiFi is an example of inter radio access technology (RAT) offloading. While this clearly alleviates congestion on the over-loaded cellular network, the ultimate potential of such offloading and its effect on overall system performance is not well understood. To address this, we develop a general and tractable model that consists of M different RATs, each deploying up to K different tiers of access points (APs), where each tier differs in transmit power, path loss exponent, deployment density and bandwidth. Each class of APs is modeled as an independent Poisson point process (PPP), with mobile user locations modeled as another independent PPP, all channels further consisting of i.i.d. Rayleigh fading. The distribution of rate over the entire network is then derived for a weighted association strategy, where such weights can be tuned to optimize a particular objective. We show that the optimum fraction of traffic offloaded to maximize SINR coverage is not in general the same as the one that maximizes rate coverage, defined as the fraction of users achieving a given rate.