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. Rules triggering the mobile offloading action can either be set by an end-user (mobile subscriber) or an operator. The code operating on the rules resides in an end user device, in a server or it is divided between the two. For the 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 the offloading is congestion of the cellular networks. The main complementary network technologies used for the mobile data offloading are Wi-Fi, Femtocell and Integrated Mobile Broadcast.

It is predicted^{[by whom?]} that the mobile data offloading will become a new industry segment. This is due to surge of the mobile data.^[1].

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 smart phone devices possessing Wi-Fi 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 and it will keep out phasing the respected revenue growth ^{[2] [3] [4]}.

Alternatives

Wi-Fi and Femtocell technologies are the primary candidates by the industry^[5]. In addition there are WiMax ^[6][7] and terrestrial networks (LAN) ^[8] offloading for 3G. The Femtocells use the 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 ^[9]. On the other hand, the 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) ^[10] is an emerging technology for tackling e.g. unplanned Femtocell deployment. Wi-Fi technology is different radio technology to cellular but most Internet capable mobiles devices now come with WiFi capability. There are already millions of installed Wi-Fi networks mainly is congested areas such as airports, hotels and city centers and the number is growing rapidly ^[11]. The Wi-Fi networks are very fragmented but recently there has been efforts to consolidate WiFi networks. The consolidation of the WiFi networks proceeds through community approach, FON as the prime example, and by the consolidation of Wi-Fi network operators ^[12].

Wi-Fi

Wi-Fi offloading is an emerging business domain with multiple companies entering to the market with proprietary solutions. 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. A further classification criterion is the initiator of the offloading procedure.

Cellular and Wi-Fi network interworking

Depending on the services to be offloaded and the business model there may be a need for interworking standardization. Standardization efforts have focused on specifying tightly or loose coupling between the cellular and the WiFi networks. 3GPP based Enhanced Generic Access Network (EGAN) ^[13] architecture applies tight coupling as it specifies rerouting of cellular network signaling through Wi-Fi access networks. This makes Wi-Fi a de-facto 3GPP RAN. 3GPP has also specified an alternative loosely coupled solution for Wi-Fi. The approach is called Interworking Wireless LAN (IWLAN)^[14] architecture and it is a solution to transfer IP data between a mobile device and operator’s core network through a Wi-Fi 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 the Wi-Fi networks is to have a 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 the offloading can simply be carried out by switching the IP traffic to use the Wi-Fi connection in mobile client instead of the cellular data connection. In this approach the two networks are in practice totally separated and network selection is done by a client application. Studies show that significant amount of data can be offloaded in this manner to Wi-Fi networks even when users are mobile ^{[15] [16]}.

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 or an open Wi-Fi network is found an offloading procedure is initiated. In the user initiated mode a user is prompted to select, which network technology is used. This happens usually once per a network access session. In the 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 the 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.

ANDSF

Access Network Discovery and Selection Function (ANDSF) is the most complete 3GPP approach to date ^[17] for controlling offloading between 3GPP and non-3GPP access networks (such as Wi-Fi). The purpose of the ANDSF is to assist user devices to discover access networks in their vicinity and to provide rules (policies) to prioritize and manage connections to all networks.

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 Wi-Fi 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). The connection managers do not require coupling of the cellular and the WiFi networks.

Femtocell offloading

Femtocell forum is an industry forum promoting mobile data offloading for 3G/4G network using Femtocell technology. The forum also works to ensure interoperability among vendors and service providers.

References and Data Offloading Reading Materials

1. ^ Perez Sarah (February 11, 2010). "Mobile Data Traffic Surge: 40 Exabytes by 2014". Read Write web blog. http://www.readwriteweb.com/archives/mobile_data_traffic_surge_40_exabytes_by_2014.php. Retrieved August 25, 2011. 
2. ^ Suoranta Risto, Lappeteläinen Antti "Operator's Dilemma - How to take advantage of mobile Internet" [1]
3. ^ Warrior Padmasree, CTO Cisco "Keynote speech in CTIA 2010"
4. ^ Cisco Visual Networking Index: Global Mobile Data Traffic Forecast Update, 2009-2014; Cisco 2010
5. ^ Scherzer Shimon "Femtocell vs. Wi-Fi for Data Offloading & Indoor Coverage" [2]
6. ^ Greenpacket [3]
7. ^ Robb Henshaw "The Role of WiMAX in Enabling Wi-Fi Data Offload Networks"[4]
8. ^ Netsnapper[5]
9. ^ Scherzer Shimon "Femtocell vs. Wi-Fi for Data Offloading & Indoor Coverage" [6]
10. ^ NokiaSiemensNetworks "Self-Organizing Network (SON) Introducing the Nokia Siemens Networks SON Suite – an efficient, future-proof platform for SON" [7]
11. ^ ABI Research "ABI Research Forecasts Wi-Fi Access Point Shipments to Exceed 70 Million by 2010" [8]
12. ^ AT&T press release "More Than 12 Million AT&T, Starbucks Customers to Get Free Wi-Fi Access for a Rich In-Store Experience "[9]
13. ^ 3GPP TR 43.902 [10]
14. ^ 3GPP TS 23.234 [11]
15. ^ Aruna Balasubramanian, Ratul Mahajan, Arun Venkataramani. Augmenting Mobile 3G using WiFi Proc. MobiSys 2010
16. ^ Kyunghan Lee, Joohyun Lee, Yung Yi, Injong Rhee and Song Chong. Mobile Data Offloading: How Much Can WiFi Deliver? Proc. CoNEXT 2010
17. ^ 3GPP TS 23.402 [12]