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A17.4 A17.4

This model is a modified version of the Extended Hata model which was developed in CEPT for studies of Short Range Devices (SRD). The basis for modification was an assumption, that although SRD devices are usually operated at low antenna heights (typically person-carried devices, i.e. with antenna height of about 1.5 m), but the interference would usually occur at relatively short distances (up to 100 m or so) when direct- or near- LOS LoS might be assumed.

The expression of b(H_b) parameter in the standard Extended Hata model, giving large extra losses for transmitter antenna heights below 30 m, was considered to be unnecessarily severe. Therefore, the only difference between Extended Hata-SRD and Extended Hata model lies in the new expression for the antenna gain factor b(H_b), which for Extended Hata model is expressed asas 

b = min(0, 20 log20log(Hb/30));                                                                                                                            (Eq. 205)

to be replaced in Hata-SRD model by :

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