We present a receiver structure with joint blind equalization, carrier recovery, and timing recovery. The blind equalizer employs a decomposition transversal filtering technique which can reduce the complexity of convolution to about a half. We analyze the performance surface of the equalizer cost function and show that the global minima correspond to perfect equalization. We also derive proper initial tap settings of the equalizer for convergence to the global minima. We describe the timing recovery and the carrier recovery methods employed. And we describe a startup sequence to bring the receiver into full operation. The adaptation algorithms for equalization, carrier recovery, and timing recovery are relatively independent, resulting in good operational stability of the overall receiver. Some simulation results for cable-modem type of transmission are presented.

Multiple access interferecnce (MAI) is a major factor limiting the performance of direct-sequence code-division multiple access (DS-CDMA) systems. Since the amount of MAI is dependent on the correlation among user signals, one way to reduce it is to reduce such correlation. In mobile multiuser communication, each user experiences a different time-varying channel response. This user-dependent characteristic in channel variation can be exploited to assist the separation of different user signals, in addition to the capability provided by the spreading codes. As the correlation among different user channels are expected to decrease with increase in time span, enhanced decorrelation among different users' signals can be effected by spacing out the chips of one modulated symbol in time. Thus we consider chip-interleaving DS-CDMA (CI-DS-CDMA) in this study. We investigate its performance through theoretical analysis and computer simulation. Employing only a slightly modified rake receiver structure, CI-DS-CDMA is shown to attain significant performance gain over conventional DS-CDMA, in multiple access communication over single- and multi-path fading channels, without complicated multiuser detection. CI-DS-CDMA also has a lower demand for short-term power control than conventional DS-CDMA, especially in one-path Rayleigh fading. Results of the theoretical analysis and the computer simulation agree well with each other.

We consider the edge-linking approach for accurate locating of moving object boundaries in video segmentation. We review the existing methods and propose a scheme designed for efficiency and better accuracy. The scheme first obtains a very rough outline of an object by a suitable means, e.g., change detection. It then forms a relatively compact image region that properly contains the object, through a procedure termed "mask sketch." Finally, the outermost edges in the region are found and linked via a shortest-path algorithm. Experiments show that the scheme yields good performance.

A global motion parameter estimation method is proposed. The method can be used to segment an image sequence into regions of different moving objects. For any two pixels belonging to the same moving object, their associated global motion components have a fixed relationship from the projection geometry of camera imaging. Therefore, by examining the measured motion vectors we are able to group pixels into objects and, at the same time, identify some global motion information. In the presence of camera zoom, the object shape is distorted and conventional translational motion estimation may not yield accurate motion modeling. A deformable block motion estimation scheme is thus proposed to estimate the local motion of an object in this situation. Some simulation results are reported. For an artificially generated sequence containing only zoom activity, we find that the maximum estimation error in the zoom factor is about 2. 8 %. Rather good moving object segmentation results are obtained using the proposed object local motion estimation method after zoom extraction. The deformable block motion compensation is also seen to outperform conventional translational block motion compensation for video material containing zoom activity.