Content delivery over the Internet to a large number of mobile users offers interesting business opportunities for content providers, intermediaries, and access network operators. A user could receive, for example, music or a digital newspaper directly to a mobile device over wireless networks.Currently, content delivery over the Internet is held back by a number of reasons. Existing network technologies, such as GPRS, have a very limited capacity to transfer large files, such as those required for good-quality pictures in a newspaper. Another problem is security. Content received over the Internet is very vulnerable to being forged. A user who cannot be certain about the source and consistency of the received stock quotes is unlikely to pay for the information. Furthermore, content providers are unwilling to distribute their valuable information over the Internet due to their fear of copyright infringements. Traditionally, content has been considered consumed as soon as it has been downloaded. Content providers have been keen on preventing their content from being transferred over peer-to-peer networks because they consider the delivery itself to be a copyright infringement.In this dissertation, content delivery is separated from content consumption by encrypting the content before delivery. When the users wishes to consume the content, a license which includes the decryption key is provided. The architecture allows content to be delivered to users' devices even before the user commits to consume the content. The user can choose to receive content whenever downloading it is the most convenient and affordable. Thus, the content providers are able to maintain control over the use of their information even after the data has been transferred to the users' terminals. In addition, content received by users can be strongly source authenticated.The architecture allows secure, efficient and reliable delivery of content to a large group of receivers. The architecture does not commit itself to any specific delivery technique, and the content can be delivered using any delivery technique including multicast, broadcast, unicast, and peer-to-peer.This dissertation focuses mostly on multicast as the delivery technique. The efficiency of the multicast delivery over unreliable heterogenous wireless access networks is thoroughly analyzed. Mobile terminals can seamlessly switch between access points and access technologies while continuing to receive data reliably from the network. The multicast delivery uses adaptive error correction and retransmissions to deliver the content as efficiently as possible to a very large number of receivers. The simulations show, that the vast majority of receivers are able to receive the content reliably with a small delay even when the radio network suffers from high packet loss probability.Although the architecture is designed to deliver content to mobile terminals, it is also suitable for delivering content to terminals with fixed Internet connectivity.
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