Advanced Multimedia Communication Systems

A fundamental challenge for present and future communication systems is the ability to transport multimedia content to a wide variety of terminals (TV, PC, PDA, cell phone), over a variety of networks (broadcast, Internet, GPRS, CDMA), at different channel conditions (congestion, high bit-error), different bitrates and different quality-of-service. This challenge leads to a number of technical problems that yet needs to be solved in a number of disciplines, including digital signal processing, telecommunications, networking, antennas and propagation and electronic circuit design. In the following, we first identify these technical problems and then propose solutions to overcome them. Advanced communications systems may need to process multimedia content, at the server, at the terminals and/or in the network. Digital multimedia (includes video, audio, speech and graphics) processing technologies are required to pre-process, encode, stream, transcode, and post-process (to conceal errors) digital content for transmission, as well as analysis, synthesis and summarization of digital content at the production stage. Another important signal processing problem is secure access and digital rights management. As packet networks are making the transition from data communications to time-sensitive multimedia communications, delay and quality of service becomes important performance parameters. Achieving the optimum performance often requires interaction between signal processing (source/channel coding) and protocol design. One of the most challenging problems is multicast multimedia communications that require reliable delivery of data to all participants who have different terminals and bandwidths. Mobile wireless communications services must serve multimedia traffic to both outdoor and indoor environments. It is of paramount importance to be able to characterize these channels accurately. In order to characterize or modify the channel, one needs to develop highly accurate, electromagnetic-based propagation models for both indoor and outdoor applications. There are other means to improve the capacity of the channel; use of smart antennas, diversity techniques and multi element arrays. Smart antennas, fully adaptive or switched beam, can be utilized in mobile communications systems to mitigate the level of interference in an urban area where interference plays a major role in limiting the capacity of the channel. As a result, more communication channels can be added before the threshold is again crossed. However, multi element array technology, which is mainly considered in wireless LAN applications where there is limited mobility, works in Rayleigh fading environment. This communication structure utilizes multiple antennas at both the transmitter and receiver, and improves the channel capacity significantly. The complexity and size of …