A survey on heterogeneous access networks: Mobile data offloading

In communication technologies, traffic growth and cost reduction constraints, users´ demand for new services, and advances in technologies (smarter devices) are three main drivers that cause the evolution of network architecture. Data offloading is one of the proposed architectures and defined as utilizing different access technologies for data delivery in users´ access to base station (BS), besides cellular network. Three mentioned drivers can also be considered as main factors for evolution toward data offloading. Mobile data offloading is used to reduce the load and the congestion of cellular network and also utilize network resources more efficiently. Moreover, this technology can provide subscribers with better quality of service. Different access technologies can be utilized to achieve these goals. These alternatives include examples such as ISM band wireless local area networks (WLANs), femtocells, Device-to-Device (D2D) communications and opportunistic communications. In this paper, we review this subject and thoroughly survey the different important offloading approaches. We categorize these approaches in terms of their usage of licensed or unlicensed frequency bands. We also provide some of the important technical challenges of these techniques and review some of the proposed solutions.