| Summary: | 碩士 === 亞東技術學院 === 資訊與通訊工程研究所 === 93 === This paper presents an optimal electromagnetic wave propagation model of realistic 3G network in Banciao urban area which based on Okumura-Hata and COST231-Hata model. In addition, we estimate orthogonal factor and system capacity of this area. Finally, we optimize system performance by adjusting the antenna azimuth and pilot channel power of 3G Node Bs.
This kind of method is different from traditionally adjusting propagation model by using single CW measurement data; we offer a different approach to tune the propagation model by employing different scrambling code and base station antenna height. The result shows very good consistent in the bias and slope of the propagation model.
The modified COST231-Hata model (Banciao model) to adapt the 3G frequency band around 2GHz and the base station height range extended to fourteen meter. We simulate in Banciao area, and prove to be more adaptive than the COST231-Hata model. In comparison with COST231-Hata AIRCOM model, the measured coverage probability of downlink interference ratio value above one of Banciao model is 27.31%, less than the AIRCOM propagation model 33.74% and COST231-Hata model 34.54%. The measured coverage probability of downlink Ec/Io value range from 0dB to -10dB is 75.01%, more than AIRCOM propagation model, 69.71% and COST231-Hata model 68.56%.
Especially, we estimate the 3G network capacity of this area. Firstly, we use Banciao model to calculate the coverage probability of downlink interference ratio above one for 0.732 by the cell planning tools. Secondly, we employ Ray-tracing method to simulate the electromagnetic wave delay spread and delay profiles of this area. Because of the delay profiles statistics characteristic, we find the delay path occurring probability density function is exponential function. Using Monte Carlo simulation method, we obtain downlink orthogonal factor of this area：Voice, 12.2kbps (SF=128), which is 0.7263；PDA, 64kbps (SF=32), which is 0.5759；Packet data, 144kbps (SF=16), which is 0.4753。Suppose Node B assign voice loading is 50%, PDA loading is 30%, packet loading is 20%. In this condition, we estimate 3G single cell downlink capacity of this area which in average, 1261.83kbps, by using the estimated downlink interference ratio and orthogonal factor.
At last, we are using Banciao model to optimize the network performance in this area. We suggested adjusting FET 3G Node B antenna azimuth which is easiest way. The target are following：Ec/Io、downlink interference ratio、number of pilot polluters。The Ec/Io coverage probability range 0dB between -10dB. When we change Node B antenna azimuth alone, we get 5% improvement in Ec/Io coverage probability.
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