SIM868_Time To First Fix

Hello everyone. My question is specific to the TTFF after a cold start. What I figured out is that the TTFF can be significantly high after a cold start i.e when the device is inside a multi-storey building for a prolonged time and then exposed to open sky for Space Vehicle data acquisition. The scenario turns worse if the device is in continuous motion there after and the delay can extend to few hours. Please let me know how can this issue be resolved & whether getting a chip-set of higher acquisition channel be of any help?

We always get signal within a couple of minutes. Always prefer to use Active antenna with these modules which need external GPS antenna.