A multimedia presentation always (1) has some real-time requirements to keep the video/audio continuity, and (2) delivers compressed media, units to reduce the network bandwidth requirement. In multimedia mobile systems, e.g., mobile personal communication systems (PCSs), (1) the re-transmission policy for recovering the lost information, which occurs during handoff, cannot be adopted because it cannot meet the real-time requirement, and (2) if some inter-unit-based compression techniques are adopted, the characteristic of losing information during hand off results in losing a number of media units, which causes very serious discontinuity in video/audio presentations. Additionally, a multimedia system always allocates a lot of buffers at client site to smooth the random network delays. However, the client devices in mobile systems, i.e., the mobile PCS handsets, are not always associated with larger buffers in order to reduce the cost, physical size, etc. These issues should be resolved to have smooth multimedia presentations in a mobile PCS environment. In this paper, we present a mobile PCS network architecture to achieve smooth multimedia presentations, and propose a new concept, which is called glue-point, in the design of handoff protocols to keep the continuity property in video/audio presentations. Based on the glue-point concept, several handoff protocols that can achieve smooth multimedia presentations in a mobile PCS environment are presented.
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