A simultaneous network search scheme for fast roaming and handover of the simultaneous voice and LTE mobile devices

Most of the countries in the world are currently providing 2G or 3G mobile communication services with limited coverage of LTE services. Therefore when an LTE service user moves into or around such countries, the LTE terminal needs to roam or handover to 2G or 3G network for service quality. For LTE terminals that can be connected to 3GPP Legacy (such as GSM, UMTS, and HSPA) and CDMA networks, it normally takes more than 2 minutes to select one of several candidate networks for roaming and 20 seconds to 2 minutes to handover to other networks before getting out of the LTE service area, which is considered very long by many LTE users. This paper proposes a scheme for fast roaming and handover that simultaneously searches for multiple networks with a Dual RF LTE terminal for both voice and data communication. In our experiment with the simultaneous network search implemented in a commercial LTE terminal with dual RF, the network selection time for roaming was reduced by 15% to 40% and the delay time for handover in LTE network was reduced by 90%.