## 3 Background
### Hotspot
#### 3.4.3 Hotspot 2.0  
Hotspot 2.0 is also known as Passpoint (Wi-Fi certified), which can be used to access Wi-Fi and Wi-Fi Alliance. The purpose of Hotspot 2.0 is to allow the Wi-Fi-enabled mobile device to automatically connect to a Wi-Fi subscriber when the mobile device moves into the Hotspot 2.0 region [88; 89]. In this way, a better on-demand service is provided to the mobile devices. In addition, a scenario for better bandwidth utilization can be developed, where the load on the network operator's infrastructure is reduced to minimize network traffic. Hotspot 2.0 is based on the IEEE 802.11u standard to enable cellular-like roaming. A mobile device that is supported by IEEE 802.11u and subscribed to Hotspot 2.0 can automatically join the network and roam accordingly [90]. A dynamic fairness model is used to charge for the use of the Internet connection in this context. A user priority list is recommended to charge for Internet usage based on time criticality and network traffic types (e.g., audio, video, and data). Hotspot 2.0 is deployed, based on the IEEE 802.11u standard, which defines a formulation for a terminal device to receive WLAN-related information. Hotspot 2.0 consists of some key elements, such as: (i) a terminal device (STA) that supports WPA2, Hotspot 2.0, 802.1X, and Access Network Query Protocol (ANQP); (ii) an access point (AP): the Hotspot 2.0 supports WPA2-801.1X and acts as an ANQP server, and it can send Hotspot 2.0 network information to the connected STAs; (iii) an access controller (AC) that supports 802.1X configuration between the Aps in stacks; (iv) an AAA server: it supports various encryptions such as the Extensible Authentication Protocol (EAP) authentication and key agreement (AKA)/subscriber identification module (SIM), Transport Layer Security (LTS), Tunneled Transport Layer Security (TTLS), and it can also obtain authentication vectors from the Home Location Register (HLR); (vi) BOSS: it provides important operational support as an end-to-end business provider to perform regular customer-facing tasks such as billing, rating, and general service. Network discovery and selection is an important job of Hotspot 2.0. It is formulated as follows. The network discovery service needs the packet exchange between the end STA module and the access point. An end STA module can perform active and passive scans. Both scans can take place parallelly. The STA device must have pre-registration with a home network, with pre-configured network cards, certificates, a username, and a password. An organization identifier (OI) is very important for the working of the STA module. An STA module can communicate with roaming WLAN, however, in that case,the roaming WLAN must have been pre-registered and configured with the home network where which, the STA is located [91]. Figure 2 presents the generic structure of Hotspot 2.0. * STA passive scan: The Hotspot 2.0 access point sends a Beacon frame to the STA module that comprises of network type, Hotspot 2.0 indication, and related network information. Upon receipt of the Beacon frame, the STA module checks the Hotspot 2.0 indication into it. The STA module can learn about basic service set (BSS) load prior to establishing a connection with the access point. If all works correctly, the STA module performs the parsing of the roaming consortium field in the Beacon frame to get details about the OI of the WLAN service provider. * STA active scan: During this scan, the STA module sends a Probe Request frame to the access point along with the network type information. Upon receipt of this frame, the access point matches with the network type of the frame with its own network type. If the network type is matched, it sends the Probe Response frame to the STA module with the necessary BSS load, the internet connectivity flag, and other network details. After receipt of the Probe Response frame at the STA module, the STA module checks the hotspot indication.