Mobile WiMAX access network is being developed to support various multimedia services such as mobile Internet Protocol Television (IPTV), mobile Video-on-Demand (VoD), and mobile internet services. This mobile network is a shared radio medium which utilizes a point-to-multipoint method, where one base station (BS) can be connected to many mobile stations (MS). That is to say that a mobile IPTV viewer can join a specific multicast group over mobile WiMAX access network, while others, at the same time, are able to receive the same program channel, even though they do not belong to the same multicast group. This, however, is different from the traditional Internet Group Management Protocol (IGMP) version, used for IPTV services, in network layer which does not allow immediate program channel sharing. This is because the Connection ID (CID) is required before the Multicast Broadcast Service (MBS) can transmit its service flows in mobile WiMAX. Therefore, in this case, viewers always need to perform two processes before they are able to view the program channels, i.e. performing the IGMP join/leave at network layer and obtaining the CID at Medium Access Control (MAC) layer. This paper propose a new extended IGMP protocol which can be used in mobile WiMAX radio access network especially for mobile IPTV services to reduce the channel change time on the network.