No abstract

In this paper the performance of the DS-CDMA system employing a suppression filter for rejection of narrow band interference (NBI) is provided. Two types of NBI, namely the binary phase shift keying (BPSK) and the single tone interferences, are considered. The behavior of the DS-CDMA system with and without a suppression filter over a Raleigh fading channel and under the effect of the two types of NBI is analyzed. The effects of suppression filter coefficients, DS-CDMA system parameters, and the NBI parameters on the performance of the system are evaluated analytically. It is shown that the suppression filter is more effective against the single tone NBI than in the case of the BPSK NBI. Moreover, it is proved that using a suppression filter with total three taps is sufficient to mitigate the effect of either the BPSK or single tone NBI.

This paper presents a novel video compression technique tailored to achieve high compression ratio for synthetic and thermal video sequences while maintaining a low level of complexity. The technique relies on the segmentation of each frame into a number of regions. The contours of these regions are subsequently compressed using the entropy encoding. The high compression ratio achieved by this technique can be traded for higher temporal sampling rates to allow the representation of high mobility objects. Three types of video sequences are used to evaluate the proposed technique. These are synthetic, thermal, and real video sequences. Compression Ratio (CR) as well as Peak Signal to Noise Ratio (PSNR) averaged over all frames are calculated for each type and compared to standard video compression techniques. Although the actual CR achieved is dependent on the number and size of the regions within the frame, the frame size, as well as its color representation; our results show significant improvement in CR up to twenty times the CR achieved using standard techniques. Meanwhile, the reduction in PSNR is limited. Although the relative performance of the proposed technique compared to the standard MPEG-I and MPEG-4, is maintained for all types of video sequences; the observed reconstructed video quality for synthetic and thermal videos is superior to the quality of real videos.

This work introduces a novel adaptive technique of filtering for solving the problem of interference suppression in phased array airborne radar systems. In this adaptive process, effects of the interference are suppressed (or minimized) according to a specific set of controlling parameters. This includes the target doppler shift and the interference spatial distributions. The proposed technique is referred to as adaptive space-time filter. Performance of our novel adaptive filter is investigated, evaluated, and compared to the known adaptive filter proposed by H. Ghouz in 1990 [1]. Results of simulation indicate that with adequate filter's complexity, excellent improvement in the signal-to-interference-plus-noise ratio is obtained at the filter's output. In addition, our filter has two main advantages over the one reported in [1]. First, our filter is simple and easy to implement. Second, a minimum total computational time of the adaptation process is required. This includes estimation of the interference space-time covariance matrix and updating the filter's weights as well as the required processing time. Finally, the presented filter is a robust solution to the problem of interference challenging the airborne radar systems, in particular, the strong reflection from the ground clutter sources.

Classical adaptive sidelobe canceller (CASLC) schemes which use only complex spatial weights are inherently narrowband, and consequently perform poorly when attempting to suppress wideband interference. This paper presents a novel solution to this problem by using tapped delay line filters in each spatial auxiliary channel, and utilizing the adaptive space-time processing for performing the required null. This sidelobe canceller is referred to as adaptive space-time sidelobe canceller "ASTSLC". The higher performance achieved by the ASTSLC architecture comes at the cost of a considerable increase in its complexity. ASTSLC technique can be used for compensation due to bandwidth degradations, channel mismatching, and multipath phenomena. In this work, the problem of bandwidth compensation is considered. The objective of our analysis is to develop some insight into the way in which space-time processing leads to performance improvement as compared to the CASLC. Moreover, some quantitative estimates of how the performance varies with array antenna (space processing) and transversal filter (time processing) parameters are also investigated and presented.