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Due to the complexity of the hearts anatomy blurred boundaries of its surrounding organs in cardiac CT images, the whole heart segmentation is still a big challenge. In this paper, method based on watershed and active contour models were proposed for the whole heart CT image segmentation task. Firstly, the Bilateral filtering approach is used to eliminate the noise of the cardiac CT images. Then, the watershed segmentation method is applied to determine the initial seed contours. Finally, the active contour model is adopted in the evolve process iteratively with the previous contour to obtain the precise segmentation boundaries for whole heart CT images. The performance is evaluated with a clinical cardiac CT images dataset, which proved good segementation results as well as the high robustness.

In order to solve the problem of complicated calculation and frequent human intervention, a new method for extracting the centerline of blood vessel based on magnetic resonance angiography (MRA) is proposed in this paper. First of all, according to the different diameter of blood vessels, the multi-scale filtering algorithm is utilized for enhancing the different scales of blood vessels by Hessian matrix. The discriminant function is established based on the gray distribution of the blood vessel and the differential operator, and then the initial position and the orientation direction of the seed point are obtained. Secondly, the new ridge point and tracing direction are optimized in the local arc length range of the initial direction to ensure that the correct ridge point position can be obtained even with large error interference. Finally, we eliminate pseudo-centerlines that do not satisfy the initial conditions and get the final centerline of the vessel to be extracted. The experimental results show that this method can automatically extract the blood vessel centerline from the MRA images without manual intervention.

In this paper, we propose a mixing white light antenna with a homogenizer and an amplification system, and demonstrated its utilization in a four-spectrum mobile VLC. The central element is the homogenizer, which is a square integrating rod that mixes four-spectrum light into white light. Behind it, there are two Fresnel lenses to amplify the light-mixing area. The system is compact with a length of 80 mm and maximal diameter of 58.5 mm. We determined the initial structural parameters of the antenna by theoretical analysis, and then we determine the best parameters by simulation. Simulation results indicate that a 0.75 m×0.75 m area can be illuminated at 1.7 m distance. The detection surface has a high uniformity (76.27%), which can meet illumination and mobile communication requirements simultaneously.

As the traditional frequency and time offset estimation method is complex and sensitive to the frequency offset, in this paper, the process of the initial cell search is described, the reason why the M-segment partial correlation bringing down the risk of incorrect detection of time offset is analyzed. Based on the time offset detected by M-segment partial correlation and the result of ML (Maximum Likelihood) estimation which is proved by Jan-Jaap, a method improving the success probability of initial cell search in the low SNR condition is proposed. In the simulation environment, the performance of the proposed method is compared with the traditional method, proving the proposed method not only less sensitive to frequency offset, but also effective.

In array signal processing, 2-D spatial-spectrum estimation is required to determine DOA of multiple signals. The circular array of sensors is found to possess several nice properties for DOA estimation of wide-band sources. C. U. Padmini, et al. (1994) had suggested that the frequency-direction ambiguity in azimuth estimation of wide-band signals received by a uniform linear array (ULA) can be avoided by using a circular array, even without the use of any delay elements. In 2-D spatial-spectrum estimation for wide-band signals, the authors find that it is impossible to avoid the ambiguity in source frequency-elevation angle pairs using a circular array. In this paper, interpolated circular arrays are used to perform 2-D spatial-spectrum estimation for wide-band sources. In the estimation, a large aperture circular array (r > λmin/2) is found to possess superior resolution capability and robustness.

AODV is an on-demand routing protocol for mobile ad hoc network, with advantages of low load of control, low power consumption as well as low-bandwidth overhead. The routing table in AODV, however, maintains only one route to the specified node. Therefore, the source node needs to re-initiate route discovery process as a route fails. To solve this problem, an improved method is presented in this paper. The proposed scheme suggests that each source node maintains an alternative route to the specified destination node. When the primary route fails, the source node will use the backup route to send packets. Simulation results show that this modification can not only improve the packet delivery fraction but also reduce the average end to end delay, the routing overhead and the route discovery frequency.

Pseudo-orthogonal space-time block coded OFDM system (POSTBC-OFDM) has recently been proposed as a novel scheme for the frequency-selective channel scenario. However, a general assumption underlying the use of space-time codes is that the channel should be quasi-static, which is violated from the nature of high mobility environment. Additionally, large Doppler spread causing rapidly time-varying channels could destroy the orthogonality among neighboring subcarriers and lead to intercarrier-interference (ICI). This paper studies the extension of the POSTBC-OFDM scheme to the rapidly time-varying channel case by adopting sectorized antenna reception technique which could reduce Doppler spread and the channels time-variance by restricting the incident angle of imping waves to a finite range. Simulation results show that this proposed system is not only suitable for high mobility condition, but also can get a better tradeoff among performance, code rate and complexity of receiver.

This paper establishes the emergency problem tree model and knowledge-base based on emergency problem, and then proposes an approach of problem solving. The problem tree model describes the problem structure and the relationships between problems, which can build the contact between problem and knowledge-base. It provides a variety of knowledge and method for decision-makers and help to improve the ability of the prevention and handling emergencies.

In this paper, capacity of the MIMO-OFDM systems using both space diversity and polarization diversity is analyzed. Based on a multi-path channel model defined by IEEE 802.16d indoor channel standard, an MIMO-OFDM system with two transmit antennas and two receive antennas is investigated. In both the transmitter and the receiver, the space diversity and the polarization diversity are simultaneously considered. For comparison, the capacity of a system only with spatial diversity is also examined.

In this paper, a new Rake receiver of the Ultra-wide band (UWB) system with multiple receive antennas is proposed. To economize the system resource, an antenna selection scheme is used. For each selected antenna, the maximal ratio RAKE combination is applied to the multi-path signals. The outputs corresponding to all selected antennas are then combined according to the minimum mean square error (MMSE) criterion. Furthermore, we designed a MMSE equalizer in the time-domain to effectively eliminate the inter-symbol interference. The joint utilization of the antenna selection, RAKE and equalization schemes in the receiver gives the presented system superior performance compared with the existing UWB receivers. Simulation examples based on IEEE 802.15.3a channel model are given.

In this paper, performance of beams-based transmit diversity in a multi-path fading channel is investigated. At the transmitter, Alamouti' s coding signals is transmitted by two independent transmitting beams. Since the received signals at each receive antenna encompasses all the multi-path components from every transmitting beam, a technique is proposed to combine the space-time block coding signals and implement space-time decoding. Simulations are conducted to show the effectiveness of the proposed approach.

Applying smart antennas to an OFDMA system is investigated. A simple resource allocation scheme for array-antenna based OFDMA systems is proposed. The resource allocation algorithm is applied to the pilot data when no beam is formed and channel estimation in frequency-domain is implemented. After piloting, a beam is formed for each user to enhance the performance of the system. Simulations based on the SUI channel model according to the standard of IEEE 802.16e WMAN are carried out to examine the performance of the proposed approach.

This paper presents a space-time coded VBLAST scheme for OFDM communication based on IEEE 802.16d protocol. At the transmitter, the data stream is partitioned into several groups and each group is STBC encoded and OFDM modulated independently. At the receiver, conventional VBLAST detection techniques can be employed. The SUI channel model which is recommended by the IEEE 802.16d working group is used in the simulations to compare performance of the STBC coded VBLAST scheme with that of the classic VBLAST for IEEE 802.16 d-based OFDM systems at the same spectrum efficiency.

In this paper, a simple and efficient post-fast-Fourier-transform (FFT) beamforming scheme for OFDM systems is proposed. The carriers are uniformly divided into several groups in the proposed scheme. For each group, only one beamforming weight is calculated by using the pilot-based channel estimate in the frequency-domain. The remaining weights are linearly interpolated by using the pilot-based weighs. Compared to the existing techniques, the proposed approach exhibits computational simplicity with efficient performance

In this paper, a simple method for space-frequency channel estimation in an orthogonal frequency division multiplexing (OFDM) system with an antenna array is proposed. The space-frequency channel impulse response is estimated in the frequency domain. The estimated channel is further used to implement joint space-frequency channel equalization in the uplink and the beamforming in the downlink. Compared with the existing systems where independent beamforming and channel equalization in frequency domain are conducted, the proposed method can significantly reduce the complexity of the system without loss of performance. Simulations are conducted to show the effectiveness of the proposed approach.

Two new space-time channel models are introduced for simulating 2 GHz wireless mobile communication systems in outdoor environments. The models combine in reason the power and delay parameters in different environments provided by ITU or 3GPP and the angle parameters generated according to 3GPP/3GPP2 joint spatial channel modeling adhoc. The new models can be directly used in the simulations of TD-SCDMA systems and can be easily extended for application to wireless systems in other frequency bands.

An efficient method is presented for multi-path DOA estimation in TD-SCDMA systems. With a specific midamble assignment strategy, a DFT-based algorithm is used to obtain multi-user multi-path space-time channel estimates. DOA estimation for each path is further carried out by using the extracted spatial signature vector. Aside from the simplicity in computation, the proposed DOA estimation method can effectively resolve multi-paths regardless of the correlation and DOA separations of the multi-paths

A Laplace power azimuth spectrum distribution model is applied to the analysis of the performance of a beamformer in CDMA communication systems. The effects of angle spread on beamforming in both the uplink and the downlink are investigated. Compared to a single-antenna-based system, the array processing gains of a mobile communication system with a smart antennas array are derived. Numerical results for a uniform linear array and a uniform circular array, respectively, are provided.