Field
The present disclosure relates generally to communication systems, and more particularly, to inter-RAT handover.
Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink, SC-FDMA on the uplink, and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
A radio access technology (RAT) is the underlying physical connection method for a radio based communication network. Many modern phones such as smart phones support several RATs in one device such as Bluetooth, Wi-Fi, and 3G, 4G or LTE. RAT can be GSM, CDMA, WiMAX, LTE, TD-SCDMA or any other wireless technology used to provide air interface to mobile devices to obtain various services (voice, email, internet, VOIP). A mobile device associated with one RAT may have a neighbor cell associated with a different RAT. The mobile device may perform neighbor cell measurements and send a measurement report to the network. Based on the measurement report provided by the mobile device, the network may initiate handover from the current RAT to the other RAT, which is referred to as inter-RAT handover.
The network may receive several measurement reports for several different neighbor cells at around the same time. The network may use the first measurement report received to initiate handover to the neighbor cell associated with the first measurement report. Thus the network might not carry out the inter-RAT handover to the strongest neighbor cell, but just to the first reported neighbor cell.