ly than base stations in mobile networks and spectrum is free. While cellular service excels at covering large areas, Wi-Fi service does extremely well at providing coverage inside buildings where it is relatively inexpensive to add access points. This trend has been made possible by the advent of handsets with chips that support both Wi-Fi and mobile air interfaces. These interfaces are now tightly integrated and have the capability to automatically hand traffic off between cell sites and Wi-Fi networks. They additionally support both voice and data. However, using voice on Wi-Fi networks drains batteries more quickly than on mobile networks. The downside of operating large numbers of small cell sites and hotspots is maintenance. Large carriers can have 50,000 of these sites to manage. Many mobile operators outsource management of their hotspots to other firms. Worldwide Roaming on Wi-Fi When people travel internationally or within the United States they expect Wi-Fi to be available SO that they avoid the extra fees wireless providers charge for using cell phones over LTE and other mobile protocols in other networks. Providers such as AT&T and Comcast offer large networks of Wi-Fi hotspots that are located mainly in the United States. However, using a smartphone in other www.TechnicalPDF.com countries can be problematic with the exception of hotels that offer in-building Wi-Fi either at no charge or at low daily rates. Enterprises that have business in international locations often sign up for Wi-Fi roaming from aggregators such as iPass and Boingo. Wi-Fi aggregators have agreements with independent hotspots to manage their hotspots and for roaming between their locations. iPass manages over 64 million hotspots in more than 160 countries in which their customers' employees roam. Boingo has more than one million hotspots. In addition to roaming internationally, Boingo offers Wi-Fi service in airports for travelers to download video and other content before boarding their airplane. The airport service is a collabo