Nowadays and mainly in the near future the wireless point-to-point or pointto-multipoint connections are operating in high frequency. These systems are applied in feeder network for future cellular mobile communication systems or BFWA (Broadband Fixed Wireless Access) networks. Besides the obvious benefits of the applied high carrier frequency there is a significant disadvantage, the considerable attenuation caused by precipitation, especially by rain. For accurate planning of the proposed microwave links the statistics of the expectable rain attenuation is highly important. Applying our previous research results the this work provides a general N-state Markov Chain model to generate rain attenuation time series on a proposed microwave link according to the link parameters. The first and second order rain attenuation statistics of the generated time series can be derived directly from the Markov model parameters, so the N-state Markov model can be applied for prediction of rain attenuation on the proposed link even in the early planning phase. With our proposed model very accurate realisation of the physical fade process can be achieved.
The need to improve the performance and the efficiency of the existing HSPA systems resulted in the 3GPP study item HSPA Evolution. The proposed system architecture for Evolved HSPA is a flat one, where network nodes are interconnected with packet based transport. As a result of the flat architecture, mobility control and handover decisions are done by the Evolved HSPA Node B that incorporates the RNC functionalities as well. During handovers the uplink traffic is forwarded through the Iur interface to the serving Evolved HSPA Node B that is combining the received flows and forwards the combined flow towards the core network. The system performance and efficiency can be improved by reducing the amount of the forwarded traffic. This paper discusses the available option and proposes an alternative solution that has minimal impact on the delay sensitive real time traffic. The improvement options are evaluated with simulations. The results are showing that the alternative forwarding strategies are improving the efficiency of the system.
In point-multipoint (PmP) systems the signal to interference and noise ratio (SINR) highly depends on the assignment of terminal stations (TS) to base stations (BS). The Broadband Fixed Wireless Access (BFWA) systems operate at high carrier frequencies, i.e. microwave domain. In this frequency range wave propagation is highly influenced by precipitation, especially rain. Feeding of base stations can be solved with fiber optic or e.g. with satellite. In this work satellite feeding is assumed, which avoids land demolition caused by fiber deployment, but its drawback is the precipitation attenuation of Earth-space links. Applying site diversity can mitigate rain attenuation effects; however, known site diversity methods are only considering downlink channel quality and during site diversity terminals do not consider decisions of each other. By site diversity when downlink signal level decreases below a threshold, terminal station can be assigned to an other base station, though in pointmultipoint systems this base station re-assignment can raise uplink interferences at other terminals. Present contribution provides a special site diversity which adopts genetic algorithm (GA) to simultaneously optimize downlink and uplink SINR values in BFWA. A convergence analysis method of the applied genetic algorithm is provided using Markov chain model.
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