New generation which have grown up with Internet and interactive gaming, are no longer satisfied with traditional one-waybroadcasting of TV pro grams. The paradigm shift from push-based media broadcasting to pull-based media streaming has been started in recent years and will be accelerated in the next few years. Internet Protocol Television (IPTV) is a good example to illustrate this claim. IPTV describes a mechanism for transporting TV streams encapsulated in IP packets using networking protocols and tries to offer more interactivity and more control over the content. When offered via wireless technologies, IPTV can pave the way for quad-play in next generation networks. However, the stringent QoS requirements of IPTV streams are very hard to achieve in wireless networks. This is mainly related to the natural characteristics of wireless environments, such as frequent packet loss, vulnerability to physical factors and fluctuations in channel condition. The problem becomes even worse in multi-hop wireless networks. WiMAX as one of the 4G candidates has several outstanding features that make it an ideal candidate to deliver IPTV services to fixed and mobile subscribers. In this thesis, we investigate same of the challenges of IPTV transmission, mainly in wireless networks. The type of wireless networks which will be covered by this thesis is based on OFDMA-based WiMAX networks. In particular, we focus on the following aspects: the efficiency of multicasting, modeling the behavior of IPTV users, capacity evaluation and effects of overhead in WiMAX networks, and reducing channel switching delay. The objectives are related to each other and each objective is investigated in a dedicated chapter.