Embedded Space-Time Coding for Wireless Broadcast Chih-Hung Kuo, Chang-Su Kim, Robert Ku, and C.-C. Jay Kuo Integrated Media Systems Center and Department of Electrical Engineering University of Southern California, Los Angeles, California 90089-2564 ABSTRACT An embedded space-time coding method is proposed for wireless broadcast applications. In the proposed system, a transmitter sends out multi-layer source signals by encoding different layers with different space-time codes. Then, the receiver can retrieve different amount of information depending on the number of antennas. The receiver with only one antenna can decode only the base layer information with a low complexity, while the receiver with more antennas can retrieve more layers of information. We derive an analytic bound on the error probability, and show both analytic and experimental results in this work. Keywords: Space-time coding, multi-resolution broadcast, scalable encoding. 1. INTRODUCTION The progress in signal processing and communication technologies has enabled digital wireless broadcast applications, leading to the commercialization of high-definition television (HDTV), digital video broadcast (DVB), and digital audio broadcast (DAB). A broadcast system differs from the point-to-point transmission in that different receivers can have different receiving capabilities. In [1], the performance of a broadcast channel was analyzed in an information theoretic framework. In [2], a multi-resolution modulation technique was proposed to provide different receiving quality according to the distance between the transmitter and the receiver. The source is divided into several layers so that the receiver with a lower signal power can still reconstruct the base-layer information while the receiver with a higher signal power can get all the information. The layered or scalable source coding technique has become mature for the last few years. For example, JPEG- 2000 and MPEG-4 fine granularity scalability (FGS) [3] have been adopted as standards for the progressive encoding of still image and video, respectively. The encoded bitstream has the property that the receiver can reconstruct the source with a rate-distortion tradeoff, even if only parts of the data are received. The scalable coding technique has inspired the exploration of many Internet applications, since the server can perform multicast and/or broadcast with a less storage space. In this work, we investigate a wireless broadcast system using multiple transmission antennas that supports the transmission of a scalable media source. Recently, the space-time coding (STC) technique has been extensively studied to exploit the transmission antenna diversity. Wireless channels are susceptible to environmental noise, and can be degraded due to the motion of the mobile station. The concept of diversity has been developed to overcome these channel impairments. The diversity is the method to provide the receiver several replicas of the signal over independent fading channels [4]. Different ways have been adopted to employ the diversity, such as the frequency diversity, the time diversity, the angle-of-arrival diversity, and the polarization diversity. The spectrum spreading (including frequency hopping and DS-CDMA), the RAKE receiver, and the error-correction coding also exploit the concept of diversity. The antenna diversity, which uses more than one antennas in the transmitter or the receiver, is also capable of providing the diversity in wireless transmission. A space-time code integrates the antenna diversity with coding techniques to achieve a higher capacity and reduce co-channel interference in multiple access. Tarokh et al. [5] derived an analytical bound on the symbol error rate and presented the criteria for STC to achieve the maximal diversity. Similar to conventional channel coding schemes, STC can be divided into two categories: trellis and block codes. The trellis (or the convolutional) STC can be decoded by the well-known Viterbi algorithm. However, the complexity of decoding the space-time block codes (STBC) is much lower than that of the trellis codes. Alamouti [6] first proposed STBC. This block code has the advantage of allowing a low-complexity maximum-likelihood decoder, and exploits the orthogonal property of the code matrix to achieve Send correspondence to {ckuo, cskim, cckuo}@sipi.usc.edu and DrRobertKu@aol.com