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This year has marked a rapid increase in interest to improve cellular to Wi-Fi interoperability – not just from mobile operators and their network infrastructure providers, but also from cable operators, fixed-line operators and enterprises. This is a global trend as organizations in every region are developing strategies to leverage Wi-Fi for a variety of reasons, including network congestion relief, improved in-building coverage and ability to offer lower cost wireless service plans. However, in order to achieve truly seamless interoperability across heterogeneous networks from any provider, the industry needs to resolve challenges associated with connectivity, authentication, session persistence and traffic management. This is the objective of several emerging industry standards, including Hotspot 2.0 from the WiFi Alliance, and the 3GPP’s Access Network Discovery and Selection Function, or ANDSF. Whereas Hotspot 2.0 is driven by consumer expectations to leverage Wi-Fi as part of their wireless service, ANDSF is driven by the need of network operators to manage how data traffic flows across various networks.
ANDSF overview
ANDSF is a set of 3GPP standards for mobile devices to automatically discover and select wireless access networks based on policies and priorities defined by the mobile operator. It provides a framework for defining, delivering and enacting network policies on wireless devices. ANDSF allows mobile operators to optimize traffic by managing network priorities and selection from the device based on both real-time conditions (e.g. quality-of-service, location, network conditions, etc.) and operator policies for network prioritization based on costs, performance, subscriber plans, and other factors.
Technical components of the ANDSF standard
As part of its specification, ANDSF defines a standard interface and management method. S14 is the standard interface for communication between the network-based ANDSF server element and the client solution on the mobile device. S14 is based on the Open Mobile Alliance-Device Management application layer protocol and enables OMA-DM bootstrapping and management of device information and functionality using standardized management objects.
The ANDSF management object provides a standard object framework for management of ANDSF policy and access network information on the device and server. The inter-system mobility policy includes prioritization rules for selecting a preferred or restricted network technology, based on a prioritized network list. ISMP incorporates location, roaming, and time of day conditions to enact policy and prioritization. The inter-system routing policy includes prioritized rules for routing traffic on an IP flow basis for devices that support multiple simultaneous connections. Recent 3GPP activity has an additional policy type being developed to address the need for inter-APN routing to support roaming use cases and selection of roaming partners based on location, other available networks, etc.
ANDSF policy control
The ANDSF client continuously evaluates conditions on the device and the active policy parameters to control radio, connection, security, and mobility activities. Various conditions, such as location, time of day and roaming, may affect which rule is active. As conditions change, the policy may trigger the device to initiate a location request (pull) from the ANDSF server. The server then provides the applicable updated policy and additional network discovery information. The server may also initiate a session to update (push) a policy for one device, for many devices within a specified group, or for all devices. As network conditions change, policies can be updated over-the-air using standard OMA-DM technology.
Practical use in mobile industry
ANDSF policies enable a variety of use cases, including offloading of cellular traffic to Wi-Fi networks based on location and/or time of day. For example, when a device is in a location that is typically congested during commute hours, the policy may dictate the selection of a Wi-Fi network until commute hours end. ANDSF can also reduce costs for service providers by simplifying the on-boarding of Wi-Fi partners and providing customers with lower cost options for mobile data. It supports creation of flexible business models and enables new Wi-Fi service offerings and service class differentiation. ANDSF is also gaining momentum in the enterprise mobility market by streamlining the deployment of Wi-Fi configurations and helping enterprises manage telecom expenses by increasing usage of lower-cost Wi-Fi networks.
Looking forward
Although the first release of ANDSF was made available in 2008, commercial deployments are still nascent. There are several reasons for this: for one, Apple iOS devices make up a huge segment of the mobile market, and Apple has made no commitment to support ANDSF in their devices (although iOS 7 now supports Hotspot 2.0). For another, the industry does not have a formal certification process for testing compliance to the ANDSF standard, leaving solution providers and operators on their own to test and validate their implementation of the standard for each device platform. The ANDSF specification is loose with respect to management tree nodes, some of which are optional or temporary, so it takes some agreement between ANDSF solution providers to consistently interpret the nodes. Although, interoperability tool kits have recently been made available to facilitate ANDSF client and server testing with easily accessible debug logs and explicit feedback on the success/failure of each command to pinpoint the trouble areas.
Summary
The ANDSF standard is intended to eliminate the need for users to manually discover and switch between available 3G, “4G” and Wi-Fi networks based on network conditions and performance. It is an important building block for creating a seamless experience across heterogeneous networks for end users. While ANDSF aims to standardize methods for selecting and prioritizing networks, it also gives operators new opportunities to differentiate their services by utilizing the power of policy-on-device. Operators can accelerate deployment of ANDSF, and gain early mover advantage, by selecting pre-validated client and server components to execute their traffic management strategies.
Brian Deeley is a driving force behind Smith Micro’s product strategy and leads teams responsible for product definition, customer requirements and solution delivery. Deeley has over 20 years of experience in technology, bringing ground-breaking hardware and software solutions to market. Previously, Deeley served as VP of marketing and product management at Uniloc. He holds a degree from the University of California, Santa Barbara and an MBA from Indiana University’s Kelly School of Business.
