Vol 50, No 4 (2016)

The procedure of local optimization of trajectory control of observations is discussed. The solution is obtained in relation to mobile digital direction-finder. The sources of radio emission (SRE), which radiation intensity satisfies to the regularities of the discrete Markov process with two states, as the objects of observation are considered. The sequence of consideration of probabilistic characteristics of the radiation intensity variations in the algorithm of control synthesis is shown. An example is given.

Traditional time/frequency domain filter-based methods would fail due to the serious overlapping of the communication signal and jamming in time/frequency domain. In order to solve this problem, an anti-jamming algorithm based on single channel source separation by exploiting cyclostationary difference is proposed for direct sequence spread spectrum (DSSS) communication. Firstly, the cyclostationary difference among source signals is used to establish the single channel source separation model based on partial priori information of the DSSS signal. Secondly, cost function of the algorithm is constructed by the training sequences and the minimum mean square error criterion; after that, the optimal separation matrix of the pilot mixed signal can be calculated based on this cost function. Thirdly, the purpose of anti-jamming for DSSS communication can be achieved by separating the communication signal from the service mixed signal based on the optimal separation matrix calculated before. Simulation results show that, compared with the unseparated signal of high bit error rate (BER) close to 0.5, the proposed antijamming algorithm is more effective in anti-jamming with the BER as low as 10^–3, which is not only applicable to narrowband jamming such as the single-tone/multi-tone jamming, but also applicable to broadband jamming such as the sweep-spot jamming.

A multiple access chaos shift keying cooperative communication (MA-CSK-CC) system over Rayleigh fading channels and in the presence of Gaussian white noise is investigated in depth in this paper. The simplified half-duplex with a single relay decode-and-forward (DF) cooperative strategy is proposed to illustrate and analysis as an example. Exact and approximation bit-error-ratio (BER) performance expressions are derived. Simulation results demonstrate that the proposed system has a prominent advantage of high BER performance over the conventional multiple access CSK systems that have a single path to transmit signal at the same data rate over Rayleigh fading channels with additive Gaussian white noise. Moreover, based on the BER performance analysis, some useful results are also derived such as the relationships between BER versus spread spectrum factors, BER versus the number of users, etc.

There are many different cloud services available, each with different offerings and standards of quality. Choosing a credible and reliable service has become a key issue. To address the shortcomings of existing evaluation methods, we propose a service clustering method based on weighted cloud model attributes. We calculate user-rating similarity with the weighted Pearson correlation coefficient method based on service clustering, and then compute user similarity combined with the user service selection index weight. This method allows us to determine the nearest neighbors. Finally, we obtain the recommended trust of the service for the target user through the recommendation trust algorithm. Simulation results show that the proposed algorithm can more accurately calculate service recommended trust. This method meets the demand of users in terms of service trust, and it improves the success rate of user service selection.

Along with the development of health informatization, many hospitals have set up PACS systems for centralized storage of patients’ medical examination images. Due to the large amount of image data, traditional methods such as C-MOVE, have slow upload and download speeds. And they also have security problems. Based on the research and development of medical imaging informatics and PACS, a JPEG2000-based method is described according to the PACS work flow and DICOM standard. This method makes the image storage, transmission and display operating in parallel, providing a good solution to timeliness and security problems of image reading and viewing.