Applied Mechanics and Materials Vols. 195-196

Abstract: This paper gives a brief introduction to the immune algorithm and combines the method of moment (MOM) which was usually used in the design of reconfigurable antenna with immune algorithm to optimize the reconfigurable antenna. By using the immune algorithm, we present an antenna reconfigurable scheme which can realize the frequency agility ranging from 8GHz-17GHz.

Abstract: In this paper, based on QR decomposition, an improved detection algorithm for quasi-orthogonal space-time block code (QOSTBC) using square QAM constellation is presented. In the proposed method, by executing single complex symbol twi-detection for each block and selecting the optimal result, the BER performance is much better than that of the linear receivers. Compared with conventional maximum-likelihood (ML) decoding, though the bit error rates (BER) performance is with a slight loss, the improved detection algorithm reduces the decoding complexity significantly. The derivation and simulation results of the proposed algorithm are presented.

Abstract: The direct sequence spread spectrum (DS-SS) signal is a typical kind of LPI signals widely-used in the modern digital communication system, and it is difficult to be detected for its statistical characteristic similar to noise. An algorithm for estimating the code rate, carrier frequency of DS-SS signals was proposed using time-smoothing cyclic periodogram instead of cyclic spectrum according to cyclostationary feature of DS-SS signal to improve the precision of parameter estimation. The estimation performance was analyzed for the cyclic spectrum by time-smoothing cyclic periodogram from the tapering points in the case of limited data length. Simulation results showed that the proposed algorithm is effective.

Abstract: This paper presents an efficient algorithm to extract the polyphase modulation parameters from intercepted signals. The algorithm is essentially based on the cyclic spectral analysis method. A calculation of parameters extraction relative error as a function of different signal patterns reveals the performance of the algorithm, which is validated via simulation examples.

Abstract: Receiver timing synchronization is one of the most important tasks in DRM system. An effective method of fine timing for DRM is presented. Firstly, it is shown that characteristics of DRM pilot pattern from consecutive OFDM symbols can increase the resolution in time and frequency domain to obtain exact channel impulse response (CIR). Secondly, we take Maximum Difference Scaling (MDS) which arrived the best fine timing point during the input samples in DRM receiver to get the concentration of the CIR. This approach has no path alias and is always able to synchronize to the first arriving path even though it is not the strongest path. In the actual coherent DRM System, this method proves to be effective and reliable.

Abstract: In the paper, it proceeds in-depth research and analysis to the existing capacitance current measurement methods, and the infuse signal method is chosen to achieve capacitance current accurate measurement on this basis. The method has the advantage of measurement error small, real-time good and safe reliable.

Abstract: In order to combat multi-path fading across multiple protocol layers in the wireless networks effectively, cooperative diversity is developed with a virtual multi-antenna array, and spatial diversity can be achieved with the relaying. In this paper, we study an improved opportunistic relaying which could be applied to future Internet of Things. Simulation results shows it has better outage probability and spectral efficiency, and based on the model we propose a simplified power allocation method, which has close performance to the exhaustive search method. It has less calculation complexity and lower outage probability, which would be more applicable for future cooperative systems.

Abstract: Research on shaping filtering algorithms in wireless communication systems has important practical value. Based on the digital base-band shaping filter, which is widely used in the area of software radio, an improved re-sampling filtering algorithm is proposed in this paper. By the design of truncated raise cosine filter, the continuous sequence of digital spread-spectrum signal can be restored. The piecewise parabola interpolation filter is established to carry out the signal re-sample, and the Farrow implementation structure is adopted to reduce the calculation cost. The algorithm is validated through the experiment using simulated and true signals respectively, which demonstrate that not only the out band power of frequency division multi signals can be effectively suppressed, but also the steadiness of re-sampling signals is improved during the dynamic environment.

Abstract: This paper firstly reviews the current state of knowledge on the effects from rain when radio waves through the atmosphere briefly. Then we describes some work being carried out by ITU to characterize rainfall attenuation in particular, and put forward an optimized model in which we lead in area overlap factor and the height relationship between base station and mobile station, to simplify the ITU model , the simulation was given by MATLAB. Finally we got results confirming the veracity of the optimized model.

Abstract: In this paper, continuous phase modulation (CPM) with rate-compatible punctured ring convolutional codes is investigated. Some typical schemes with maximum normalized minimum squared euclidean distance (NMSED) are searched and given. The performance of bit error rate for rate-compatible punctured ring convolutional coded CPM on AWGN channel is simulated, and simulation results show that this system can provide good performance of bit error rate and variable-rate capabilities. Furthermore, simulation results also prove that the transmission efficiency increases when code rate is decreasing.