<title>Rate-distortion optimized multimedia delivery via orthogonal frequency division multiplexing (OFDM)</title>

Abstract

This work describes a method to optimally transmit multimedia data over wireless fading channels via Orthogonal Frequency Division Multiplexing (OFDM). It is well known that multimedia data is sensitive to fading effects because each data bit varies in importance. Hence, reliable broadband wireless media communication systems maintain a number of very specific needs such as unequal error protection and time-varying bandwidth requirements, etc. Up to now, most OFDM systems allocate bits in a uniform manner across the subcarrier distribution. This type of methodology is fine for text data transmission with a performance measure in terms of the bit error rate (BER), but not sufficient to maintain high end-to-end visual quality for multimedia data transmission. To improve the overall system performance, we focus on optimal bit allocation in a rate-distortion sense. Our algorithm examines the data content and its associated performance and allocates the most important bits to the best channels in order to minimize the overall distortion. The proposed scheme demands channel state information that specifies estimates on the subcarrier quality distribution. It is demonstrated by experimental results that a significant gain in multimedia QoS is achieved with our approach with a layered video codec i.e. Motion JPEG2000.