VoIP in applications for wireless access

Voice over IP (or VoIP) is a common term to refer to the different protocols that are used to transport real-time voice and video and the necessary signaling by means of the Internet Protocol (IP). H.323 [1] is an ITU-T standard for real-time voice and video communication over packet networks. During the past two years it has become the standard on the Internet for VoIP. Another relatively recent example is SIP (Session Initiation Protocol) [2] for establishing multimedia sessions, that has been adopted as an RFC by the IETF. The cost to transmit digital information end-to-end is dropping dramatically, while there has been a tremendous increase in the available bandwidth. Not only has this been true in backbone networks, it has become the trend in access networks for both fixed and wireless access. The price/performance of end-user electronics is dropping while there has been a tremendous increase in computational power. As far as personal communication and mobility is concerned, we are in the position to create new applications and services [3,4] that go far beyond what telephony systems have been concerned with and able to accomplish. One of the main contributing factors is the Internet Protocol, which allows these new applications to benefit from the fact that end-user devices are now able to use multiple services over a single access. The result is that we are now able to build new interactive services, which can combine both voice and data simultaneously. While this has been widely accepted for fixed access networks, there has been quite some disagreement about what it takes to provide interactive multimedia applications over wireless access networks. In the local area, Wireless LAN access has been available for some time and end-user devices and applications are beginning to appear in the market that address the needs of office-environments (for example the Symbol Technology "phone" which uses a wireless LAN infrastructure). In addition, there is presently a strong trend towards third-generation wireless networks for wide-area access. The basic premise is that here too, lots of bandwidth is needed to provide multimedia services and that the delivery of bandwidth should be handled by QoS-related services that are packed with the network access. Our approach is radically different by proposing to use end-to-end connectivity between hosts on top of IP (over wireless access) to bring mobile multimedia services, and that already the data-rate that is available for wireless access to …