Читать книгу Position, Navigation, and Timing Technologies in the 21st Century - Группа авторов - Страница 111

A typical BTS transmits into three different sectors within a particular cell. Ideally, all sectors’ clocks should be driven by the same oscillator, which implies that the same clock bias (after correcting for the PN offset) should be observed in all sectors of the same cell. However, factors such as the unknown separation between the phase centers of the sector antennas and delays due to RF connectors and other components (e.g. cabling, filters, amplifiers) cause the clock biases corresponding to different BTS sectors to be slightly different. This behavior was consistently observed experimentally in different locations, at different times, and for different cellular providers [18, 22]. In the following sections, a stochastic dynamic model for the observed clock bias mismatch for different sectors of the same BTS cell is derived.