Balázs Héder

General N-State Markov Model for Rain Attenuation Time Series Generation

Nowadays and mainly in the near future the wireless point-to-point or point-to-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.

Convergence analysis of genetic algorithm applied for dynamic optimization of terminal to base station assignment in satellite Fed BFWA systems

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 point-multipoint 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.

Improved Uplink Macro Diversity Combining in Evolved HSPA Systems

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.

Rain Attenuation Time Series Generation on Terrestrial Microwave Links with General N-State Markov Model

Nowadays and mainly in the near future the wireless point-to-point or point-to-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. In this contribution our formerly published N-state Markov chain model is applied to predict first and second order statistics of rain attenuation on a proposed terrestrial microwave link in the planning phase. The first and second order statistics of rain attenuation can be derived directly from the Markov model parameters.

Second order statistics of rain attenuation time series generated with-state Markov chain model

Point-to-point and point-to-multipoint connections operating at high frequencies become increasing importance in the near future wireless communication systems. These systems are applied in feeder network for future cellular mobile communication system or BFWA (broadband fixed wireless access) networks. For accurate planning of the proposed microwave links the estimation of the CCDF (complement cumulative distribution function) of attenuation is highly important to achieve appropriate outage performance. In this work an N-state Markov chain model is investigated, which is used to generate attenuation time series influenced of those wireless links. With our proposed model very accurate realization of the physical fade process can be achieved. This work mainly focuses on the comparison of the generated and the measured attenuation time series, both the first and second order statistics of attenuation will be examined.

Site diversity examination based on rain attenuation measurement

The mobile operators often use point-to-point microwave connections for feeder links in their access network. Wave propagation at the applied frequencies is highly influenced by precipitation especially by rain. Applying appropriate diversity techniques we can overcome on the problem of high outage percentage of the feeder links. In this paper after getting a short description of the countrywide measurement system, a theoretic site diversity (as a possible solution to reduce the effect of rain) is presented based on a particular rain event. Also new results on comparison the achievable diversity performances of the proposed system in case of applying a particular rain event and in case of applying one year rain attenuation measurement

Adaptive terminal to base station assignment in BFWA systems

In point-multipoint systems the signal to interference plus noise ratio 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. In this frequency range wave propagation is highly influenced by precipitation. Applying site diversity can mitigate rain attenuation effects. Present contribution provides a special site diversity method adopting genetic algorithm to adaptively optimize TS-BS assignments from point of view of the interference in BFWA service area. Rain events are generated with a Markov modeled simulation of the rain cell translations.

Estimation of Rain Attenuation Distribution on Terrestrial Microwave Links with General N-State Markov Model

Broadband radio communication systems operate at high carrier frequen-cies, i.e. microwave domain. In this frequency range wave propagation is highly influenced by precipitation, especially rain. For accurate planning of high frequency microwave links (e.g. feeder network of mobile opera-tors) the reliable estimation of rain attenuation distribution on the desig-nated links is essential. In our previous works an N-state Markov Chain model was used to gen-erate rain attenuation time series [5, 6, 8]. The model is applicable to esti-mating the first and second order statistics of rain attenuation. The model parameters were derived from fade slope statistics of attenuation measured on a given terrestrial microwave link only. Rain attenuation or rain rate modeling with time series generation is of great interest in propagation models. Partitioned Fritchman model [4] is applied for rain fade duration modeling of terrestrial [2] and land mobile satellite links [3]. Present contribution based on demonstrates the novel application of our proposed general N-state Markov model to predict rain attenuation statis-tics of a planned microwave link. For parameterizing our model, several measured yearly attenuation time series were considered simultaneously.

Route diversity examination in BFWA systems

In a BFWA (broadband fixed wireless access network) the evolved SINR (signal to interference plus noise ratio) is relevant influenced by the TS (terminal station) to BS (base station) assignment. At the applied 38 GHz frequency band besides the existing interference and noise, the precipitation causes the greatest problem. A time-dependent rain event can cause SINR fluctuation, and that can result in termination of the radio links. If the communication link between TS and its serving BS is affected with heavy rain, a possible solution could be to assign these TS to another BS (route diversity). This method improves the SINR condition for the effected TS, however can lead to SINR degradation in other locations of BFWA serving area. Therefore a special TS-BS assignment criterion must be evaluated to improve the overall SlNR conditions in the whole BFWA area. In this paper the efficiency of the proposed dynamic route diversity method is presented and the attenuation effects of simple obstacles are also taken into account