A Low Cost Method for GSM Mobile Synchronization to Base

In wireless communications, a mobile device needs to track the base station frequency and time base very accurately.

For example, in 3GPP GSM standard, the mobile carrier frequency has to track the base station with 0.1ppm accuracy. Along with this, the mobile time base cannot be more than 2μs off of its serving base station [1]. Ideally, a mobile device should use a voltage and temperature compensated oscillator to remain synchronized with its base station.

However, voltage and temperature compensated crystals are relatively expensive. This paper presents a mobile synchronization approach which could afford an inaccurate and inexpensive crystal [2].

The carrier frequency synchronization is achieved by adjusting the fractional-N PLL while the time base synchronization is obtained by introducing simple physical layer algorithms and existing hardware.