Study On Radio Propagation Model Tuning And Its Application In 3G System

1.IntroductionWith the fast development of mobile communication technology, the third generation mobile communication system is about to be the leader. Three primary standards of 3G, including WCDMA,CDMA2000 and TD-SCDMA, are will hold the market of Chinese mobile communication. Compared with the second generation mobile communication system (for example: GSM), the third generation mobile communication system is a wide-band code division multiple access system. It can offer image operation and many kinds of data operation having higher speed. Therefore, a more complex coverage design and capacity plan is needed.Radio wave propagation model is the basic of radio network planning. A relatively veracious propagation model is favorable for estimating base station's coverage range and forecasting network's coverage condition exactly, then it can help to estimate the amount of base stations meeted the coverage demand. Usual Radio propagation and coverage forecasting are both based on experiential model, but experiential model can't reflect the propagation character of a special environment accurately. Therefore, it is necessary to make radio propagation testing in a special environment, and then tune the radio propagation model used in this environment.This paper makes WCDMA system to be an example, choosing a internal small and medium-sized city as an experiment, raising a simple linear-iterative arithmetic. Then, the arithmetic is used to tune the city's three kinds of typical area, and carry primary radio network planning using tuned model in this city.2.Basic model choosing and data collecting for model tuningPropagation model tuning is based on classical theoretic model. When we obtain a lot of datas after radio propagation tesing, we can tune every parameter of classical theoretic model according to an arithmetic, which can make the final propagation model suit to actual geographical condition and radio environment rather better. Classical theoretic models include Okumura-Hata,CCIR,COST231-Hata,WIM and so on. All the models'applicable condition is different, so not all the models can be used to propagation model tuning in 3G system. By means of experimental simulation and engineering practice, we consider the applicable upper limit frequency of COST231-Hata is close to the frequency of 3G system. Furthermore, this model adds a big city tuning parameter, which can achieve anticipated purpose when it is used in different cities, so we choose this model as the basic of model tuning.The radio propagation testing datas for propagation model tuning are needed after determining the basic model. In this paper, testing datas are collected by CW test. CW test is to span transmiting antenna in typical area, transmit single carrier wave, and note signal power of everywhere by means of receiver in the prearranged path. After collecting instantaneous receiving power datas in the testing area, we also need to do something with the datas, including data percolation,GPS adjustment,geography average and path loss calculation. After doing all the above things with CW testing datas, we can obtain some datas about propagation path loss in the end, and then the datas can be used to propagation model tuning in the next step.3.Propagation model tuningIn this paper, we do some improvement to the model tuning arithmetic in literature [29, 30], and raise a simple linear-iterative arithmetic. This arithmetic is used to tune the radio propagation model based on COST231-Hata model in the precondition of assuring error square sum minimum using least square theory. Furthermore, this arithmetic makes multi-parameters'nonlinear-iterative predigest two parameters'linear-iterative, including attenuating constant K1 and distance attenuating parameter K2, realizing an improved arithmetic with low calculating complexity.According to CW testing datas of a internal small and medium-sized city, we obtain the model tuning results of three kinds of areas, including dense the city zone,along-river city zone and suburb in the small and medium-sized city we have chosen. By means of observing the error distribution of forecasting datas around adjustment and testing datas, it can be found that the precision of forecasting path loss using tuned propagation model is advanced greatly. Furthermore, By means of statistical examination of tuned result, and compared with the result in literature [29, 30], it can be found that the tuning arithmetic in this paper predigests the calculating complexity in the conditon of keeping tuned precision unchangeable, advances the model tuning efficiency, and validates tuned model's availability at the same time.4.Application of tuned model in radio network planningIn order to validate tuned model's practicality, we use tuned model to carry primary radio network planning of WCDMA system in the small and medium-sized city we have chosen, mainly including linking budget and capability estimating. On the one hand, because WCDMA system's coverage is limited by uplink, so we obtain cell's covering radius in different environment. Then, according to the network frame, we obtain the number of base station needed by coverage by means of coverage design. On the other hand, according to capability analysis of uplink and downlink, contacting with experimental simulation, we ascertain that system's capability is limited by downlink. Then, we do some capability analysis of mixed operation to downlink using Campbell method, and obtain the number of base station needed by capability. Finally, comparing the number of base station needed by coverage and capability, we obtaine the final number of base station, which establishes the foundation for particular radio network planning in the next step, and makes the tuned model in this paper get sufficient application.5.ConclusionIn this paper, we raise a simple linear-iterative arithmetic of 3G system based on classical propagation model and radio propagation testing data of internal small and medium-sized city. This arithmetic is an improvement of existed tuning arithmetic. Results of experiment show that in some small and medium-sized city, where terrain character is relatively simple, using the method in this paper to model tuning could embody its advantage sufficiently. The results in this peper offer reference for radio network planning of 3G system in similar city, which is having important realistic meaning.