Access Network Discovery and Selection Function is a standard that is used in the area of traffic offloading. It allows mobile operators to outsource the data traffic of mobile devices from the mobile network to networks with other network technology such as Wi-Fi networks. Among other things, the end devices are informed via ANDSF of the rules (policies) for changing networks.
The abbreviation ANDSF stands for Access Network Discovery and Selection Function. It is a standard of the 3rd Generation Partnership Project (3GPP). It provides mobile telephony providers with procedures to outsource the data traffic of mobile devices such as smartphones to access networks with other wireless network technology such as Wi-Fi networks or WiMAX networks.
This outsourcing is referred to as traffic offloading or mobile traffic offloading and is intended to avoid overload situations, improve the network supply to end customers, and reduce infrastructure costs for providers. ANDSF provides the end devices with, among other things, the rules (policies) for changing networks and provides information about the available alternative wireless networks. Both terminal and network-initiated changes are supported. In addition to ANDSF, other technologies, processes, and standards are defined for traffic offloading, such as Hotspot 2.0 for automatic login and authentication in Wi-Fi networks.
Basics Of Traffic Offloading
The term traffic offloading describes the idea and the necessary procedures to outsource data traffic from 3G, 4G or 5G– based mobile networks to alternative access networks with wireless technology such as in Wi-Fi networks. The goal of traffic offloading is to relieve the pressure on mobile phone networks and to avoid traffic jams caused by too many end devices and excessive use.
Mobile phone providers have the advantage of improving their customers’ network coverage without having to invest in additional mobile phone infrastructure and radio frequency licenses. Depending on the method used, offloading can in principle is triggered by the end device, the network, or the provider.
The mobile phone providers are pursuing the strategy of automating traffic offloading. Ideally, it should take place unnoticed for the user without interaction or intervention, and disconnection. This gives the providers maximum control options for the distribution of traffic flows and traffic loads. To implement seamless traffic offloading, standards such as ANDSF (Access Network Discovery and Selection Function) or Hotspot 2.0, also called Passpoint, were developed by various organizations.
How Access Network Discovery And Selection Function Works And Components
ANDSF uses the client-server model for communication between the end device and the network. The ANDSF client, also called user equipment (UE), communicates with an ANDSF server via OMA-DM (Open Mobile Alliance Device Management). Typical end devices are, for example, smartphones with iOS or Android operating systems.
The S14 interface is used as the interface for communication. The IP- based interface supports both push and pulls mechanisms. With the pull method, the UE contacts the server and requests information and rules for the network change. The push method communicates the policies to the UE without a specific request from the end device.
ANDSF can be used to transmit a list of available Wi-Fi networks within range of the end device. Also, information such as supported access technologies, network frequencies, and network identifiers such as SSID can be transmitted. ANDSF knows an Inter-System Mobility Policy (ISMP) and an Inter-System Routing Policy (ISRP), which can be communicated to the UE depending on the type of device. ISMP contains rules for end devices that only support an active network connection. The rules relate to the offloading of all terminal traffic. ISRP is intended for end devices that can operate several active network connections at the same time. This makes it possible to distribute traffic to different access networks via ISRP.
Advantages Through The Use Of Access Network Discovery And Selection Function
Traffic offloading with Access Network Discovery and Selection Function offers numerous advantages for both mobile operators and users.
These Advantages Are:
- Intelligent, seamless offloading to Wi-Fi networks without user interaction and disconnection.
- The comprehensive set of rules for changing networks can be implemented.
- Different information options for the end devices – push, pull, time-based, location-based.
- Manufacturer-independent standard – support of different network and end device technology with different operating systems.
- Automatic selection of the optimal access network.
- Reduction of the energy consumption of mobile devices by using local Wi-Fi hotspots.
- Avoidance of congestion and congestion in the cellular networks.
- Improved network coverage for mobile phone users – better radio coverage of areas with high user density or in buildings.
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