There’s some key problems of transmission of multi—service mixed signals in fibers for C—RAN, so the influence of
dispersion and crosstalk on transmission of mixed signals is researched. Besides, the evolution of multi—service signals
is theoretically analyzed. A scheme for transmitting mixed signals is proposed, by which the optical carrier will filtered.
The carrier loading mixed RF signals are modulated by direct modulation. Then mixed signals will be transmitted.
Mixture transmission of LTE signals and random radio signals is simulated, obtained the maximum transmission distance
of signals at which signals can keep high-quality, with the help of the analysis of performance of the transmission system.
This transmission distance can meet the demand of access networks, which means that the proposed scheme is available.
The paper gives a set of new low power radio propagation models in the picocell environments suitable to some urban and rural conditions in China. A number of propagation measurements was taken by the authors using two antenna height of 3.2 m to 7.5 m at frequency 900 MHZ. Test settings were chosen in rural open areas, suburban streets, and urban streets, crossroads and overbridges in order to study propagation in variety of environments. Based on the obtained data in different environments, this paper takes the further steps to discuss the variations of signal strength with distance that have distinct near and far regions separated by a breakpoint and the effect of antenna height and type by analyzing the two ray model, and then gives a new propagation model, which was proved well-fitted to the measured results in some places. Moreover, this model was applied to make the radio propagation prediction for CT2 Campus Network, which is now running well. This also shows the practicality and reliability of the model in Chinese environments. Up to present, the measurement database has been established and a CAD software package which can predict the radio coverage area for rural and urban in China is going to be finished.