Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-12-13 Cooperative journals: 《计算机应用研究》
Abstract： Aiming at the problems of low system throughput rate and low system identification rate of traditional dynamic frame time gap Aloha multi-label collision prevention algorithm (DFSA) , this paper proposes an UHF RFID collision prevention algorithm (OVSF-DFSA) which can be identified in parallel. By combining the code division multiple access technology based on orthogonal variable spread spectrum factor (OVSF) code as spread spectrum code and dynamic frame time slot ALOHA (DFSA) protocol, the algorithm breaks the limitation of recognizing only one tag in a single time slot and realizes the transformation from label collision to code collision. Based on theoretical analysis and simulation experiment, this paper explores the performance of the system throughput rate, total time slot number and system recognition rate under the algorithm. Experimental results show that when the frame length of fs>2 and OVSF code length m>2, and the tag number is greater than 200, the system throughput rate under OVSF-DFSA algorithm is m times that of DFSA algorithm, and compared with DFSA, MS-DFSA and PIGDFSA algorithm, OVSF-DFSA algorithm has better performance in the above performance.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-08-13 Cooperative journals: 《计算机应用研究》
Abstract： Aiming at the problem of high complexity and low practicability caused by the Bessel functions in the traditional first- and second-order moments estimation algorithm, this paper proposed an improved moments estimation method based on the order selection of Bessel function. Firstly, this algorithm calculated the moments estimation value corresponding to different K by using original estimation formula, then calculated moments estimation value with Bessel function of different orders, further solved the corresponding K value and its estimation accuracy, finally, determined the order of Bessel function acquired and improved the estimation method. Experimental results show that the improved method obtains good performance in time consuming, especially for small K.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-07-09 Cooperative journals: 《计算机应用研究》
Abstract： The performance of the V2V communication system depends on the characteristics of the wireless channel, so it is very important to use a suitable model to characterize the communication channel. This paper studied the vehicular communication channel in the 3D street scattering environment. Considering the scatterers such as tall buildings and trees on both sides of the road, and the transmitting and receiving ends are moving, use multi-antenna technology to establish the elliptic column scattering model. Using geometric analysis, this paper duduced the time auto-correlation function (ACF) and cross-correlation function (CCF) ; compare the difference of ACF and CCF in the case of line-of-sight(LOS) and non-line-of-sight (NLOS) , this paper verified the feasibility of the simulation method; study the difference in channel capacity under different antenna arrays and scattering environments, which highlight 3D models more accurately. The consistency between the measurements results and the theoretical analysis shows the usability of this 3D model and broadens the research of vehicular communication systems.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-05-18 Cooperative journals: 《计算机应用研究》
Abstract： In order to improve the statistical properties of multipath fading and more accurate description of wireless channel. This paper proposed an improved simulation model based on Monte Carlo method (MCM) for uncorrelated multiple Rayleigh fading channels. Based on the angle of arrival (AOA) , the multipath element (k) is introduced into the new simulation model, which improved the爉ethod of evaluating AOA. Through the simulation analysis of the channel model parameters AOA, k, the number of low frequency oscillator and the mean square error (MSE) , the results show that a pretty good agreement statistical property of the new model and those of the underlying reference model has been observed. Compared with MCM, the new model has a significant improvement in the autocorrelation properties in the same conditions and the MSE is about a quarter of the original. The new method is useful for the design of wireless channel simulator, frequency-selective channel.
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