Mobile data offloading
Mobile data offloading, also called data offloading is the use of complementary network technologies for delivering data originally targeted for cellular networks. The mobile data offloading action can be performed by an end-user a.k.a mobile subscriber or an operator. For end users the purpose for doing mobile data offloading is based on data service cost control and availability of higher bandwidth. For the operators the main purpose for offloading is congestion of the cellular networks. The main complementary network technologies used for mobile data offloading are WiFi and Femtocell.
It is predicted that mobile data offloading will become a new industry segment [1]. This is due to surge of the mobile data [2].
Mobile data surge
Increasing need for offloading solutions is caused by the explosion of the Internet data traffic and especially the growing portion of the traffic going through mobile networks. This has been enabled by numerous smart phone devices possessing WiFi capabilities together with large screens and different Internet applications from browsers to video and audio streaming applications. In addition to smart phones laptops with 3G access capabilities are also seen as one major source mobile data traffic. It has been estimated that the total Internet traffic will pass 500 Exabytes/year milestone in 2013. Annual growth rate of 50% is expected to continue.
Network technology alternatives for mobile data offloading
WiFi and Femtocell technologies are the primary candidates by the industry [3]. In addition there are WiMax offloading experiments for 3G [4]. The Femtocells use standard cellular radio technologies thus each mobile is capable of participating in the data offloading process, though some modification is needed to accommodate the different backhaul [5]. On the other hand, cellular radio technologies are founded on the ability to do network planning within licensed spectrum. Hence, it may turn out to be difficult, both technically and business wise, to mass deploy Femtocell access points. Self Organizing Network (SON) [6] is a emerging technology for tackling e.g. unplanned Femtocell deployment. WiFi technology is different radio technology to cellular but most Internet capable mobiles devices now come with WiFi capability. There are already millions of installed WiFi networks mainly is congested areas such as airports, hotels and city centers and the number is growing rapidly [7]. The WiFI networks are very fragmented but recently there has been efforts to consolidate WiFi networks. The consolidation of WiFi network take place both in community approach, FON as the prime example, and by the consolidation of WiFi network operators [8].
WiFi offloading
WiFi offloading is an emerging business domain with multiple companies entering to the market with proprietary solutions [9], [10] [11][12]. As standardization has focused on degree of coupling between the cellular and WiFi networks. The competing solutions can be classifying based on the minimum needed level of network interworking. The further classification criteria is the initiator of the offloading procedure.
Cellular and WiFi network interworking
Depending on the services to be offloaded and the business model there may be a need for interworking standardization. The standardization efforts have focused on specifying tightly or loose coupling between cellular and WiFi networks. 3GPP [13] based Enhanced Generic Access Network (EGAN) [14] architecture applies tight coupling as it specifies rerouting of cellular network signaling though WiFi access networks. This makes WiFi access network as a de-facto 3GPP RAN. 3GPP has also specified an alternative loosely coupled solution to utilize the WiFi networks. The approach is called Interworking Wireless LAN (IWLAN) [15] architecture and it is a solution to transfer IP data between a mobile device and operator’s core network through a WiFi access. In the IWLAN architecture, a mobile device opens a VPN/IPsec tunnel from the device to the dedicated IWLAN server in the operator’s core network to provide the user either an access to the operator’s walled-garden services or to a gateway to the public Internet. With loose coupling between the networks the only integration and interworking point is the common authentication architecture.
The most straightforward way to offload data to WiFi networks is to have direct connection to the public Internet. This no coupling alternative omits the need for interworking standardization. For majority of the WEB traffic there is no added value to route the data through the operator core network. In this case offloading can simply be carried out by switching the IP traffic to use WiFi connection in mobile client instead of 3G data connection. In this approach these two networks are in practice totally separated and network selection is done by client application.
Initiation of offloading procedure
There are three main initiation schemes, WLAN scanning initiation, user initiation and remotely managed initiation. In the WLAN scanning based initiation the user device performs periodically WLAN scanning. When a known WLAN is found offloading procedure is initiated. In user initiated user is prompted, usually once per session, which network technology is used. In remotely managed approach a network server initiates each offloading procedure by prompting the connection manager of a specific user device. Operator managed is a subclass of remotely managed approach. In the operator managed approach operator is monitoring its network load and user behavior. In the case of the forthcoming network congestion the operator initiates the offloading procedure.
WiFi offloading solutions
uAxes - Ubiquitous Access
uAxes is a mobile data offloading solution by Notava [16]. uAxes does not require coupling between particular WiFi and cellular networks instead it focus on easy utilization of leased 3rd party WiFi capacity. But in the presence of IWLAN or EGAN implementation uAxes may perform the offloading transaction over these protocols. uAxes is a remotely initiated offloading concept. uAxes system uses embedded SMS to initiate individual user devices to perform the offloading process even if WLAN radio is turned off. The operator may pin point each individual device to be offloaded at a given moment. By using the remotely managed uAxes solution the user device may be supplied with proper WiFi keys specific the current location and valid for a specific time duration [17].
Operating System Connection Manager
Many operating systems provide a connection manager that can automatically switch to wifi network if the connection manager detects a known wifi network. Such functionality can be found from most modern operating systems (for example from all Windows versions beginning from XP SP3, Ubuntu, Nokia N900 and Apple iPhone).
Femtocell offloading
Femtocell forum is an industry forum promoting mobile data offloading for 3G/4G network using Femtocell technology. The forum also works to insure interoperability among vendors and service providers.
Alternative approaches
According to Mobile Predictions Annual Survey [18] tiered pricing and even larger investment in 4G infrastructure are the main alternatives for the mobile data offloading. On the other it has been stated that mobile data surge is so phenomenal that 4G investment alone does not address the full problem [19].