Yuan Dongfeng

Antenna downtilt performance in urban environments

This paper discusses antenna downtilt concepts and performance in an actual operating cellular system, the relationship between antenna height, downtilt angle, and coverage radius is also discussed. Theoretical calculation and actual operating data collected from the cellular system are compared. We draw the two following conclusions. In modern urban propagation environments, the coverage area control by antenna downtilt is reduced in a cell with a radius less than 2 km under occasional high-rise distributed tall building environment. For field engineering, to some extent, it is difficult for the base station engineer to measure and adjust accurately the calculated downtilt angle in cellular field work, so a new method should be found.

A multi-grade mean morphologic edge detection

A method of edge detection based on multi-grade mean mathematical morphology is put forward. The properties of the edge detector are analyzed, and other morphologic methods are compared with it. The method results in good edge detection and at the same time raises the de-noising capacity.

Reducing PAPR of OFDM with convolutional code and 8-ask mapping

High peak-to-average power ratio (PAPR) has become one of the major disadvantages in OFDM system. Selective mapping (SLM) is an effective scheme to reduce PAPR. A novel scheme which uses convolutional code and 8-ask mapping based on SLM is presented in this paper. Simulation results show that the new scheme can reduce the PAPR significantly while the BER performance is low enough.

On the performance of interleaved convolutional codes and the comparison with BCH codes in different mobile channels

The 3-state and 4-state Markov models are proposed as the long-bursting error possibility models of mobile channels. The coding and decoding of simple convolutional codes and the method of interleaving are combined. The error-correcting performance of interleaved convolutional codes in nine different channels with different modulation styles, vehicle speeds, and different information transmitting rates is simulated and researched. In addition, the above is compared with former research work on BCH codes and analyzed. Some significant conclusions are obtained.

Some methods of image enlarging with interpolation

In this paper some methods are given for the gray images to be 2/spl times/ enlarged with interpolation. After comparison, the methods of wavelet and fractal are more suitable to the processing of image enlarging.

Research on error-correcting scheme of image transmission in fast fading mobile channel

We adopt the (2,1,3) convolutional code combined with an interleaving technique as the anti-interference measure. We simulate and discuss the performance of error-correction of a standard image transmitted through eight mobile channels which have four different modulation styles and two different vehicle speeds; we also compare the performance with that in an AWGN channel. We study the influence of the fast fading characteristics on the reliability of image transmission, the error-correcting performance of the convolutional codes in the mobile channel and the significance of the interleaving technique. At the same time we prove the results obtained are similar to previous ones. We also obtain some significant conclusions and propose some ideas for the mobile image communication system.

Channel modeling and perforumance estimation of block codes with periodic and changeable interfeaving degree in the digital mobile channel

In this paper, a simple partitioned Markov model with three states for the digital mobile channel is presented based on a field test curve. The expression of the model and its transition probability matrix P are obtained and error distribution probability P(n,m) is calculated In terms of the matrix P, From P(nm), the performance for a few of Interleaved block podes, which are BCH codes and Golay code is estimated by use of the BSC model and the simulation results is given. At the meantime, additional time-delay caused by the periodic interleaving is obtained. A few of group of the changeable Interleaving degree scheme is presented and the comparison between the periodic and changeable Interleaving degree scheme is obtained by means of the analysis to the error characterization in the digital mobile channel.

The modelling for the mobile communication channel

A simple partitioned Markov model with three states for a mobile communication channel is presented based on a field test curve. By curve fitting the author obtains the model parameters and its state transition probability matrix. From these parameters, the author generates the error sequence by software on a computer and the statistical characterization of this error sequence is calculated. The results are close to the ones obtained from the real field test curve.<<ETX>>

Propagation effects on handoff activity in a cellular system

The handoff performance is very important in a cellular radio system, especially in densely populated urban areas. This paper presents some statistical results of currently operating cellular system in Jinan city and through field measurements, we analyze propagation effects on intercell handoff and intracell handoff in the Jinan cellular system. We conclude that a new, practical handoff algorithm should be applied for handoff initiation and decision in cellular system under modern urban propagation environments.

Research of Wavelet based Multicarrier Modulation system with Woven Convolutional Codes

In this paper, we first provide an overview of the woven convolutional codes (WCC) and an iterative decoding scheme for WCC. Then we present a new coded wavelet based multicarrier modulation (WMCM) systems scheme by using WCC as channel coding scheme. Using simulation analysis, we lastly shown the bit error rate (BER) performance of WCC coded WMCM scheme. The simulation results show that increasing the number of decoding iterations of WCC-WMCM can not bring so much coding gain in the low regions of Eb/No. But in the middle to high regions of Eb/No, increasing the number of decoding iterations can greatly improve the performance of WCC-WMCM. We also get that the frame- length will also impact the system performance.