The present invention relates to wireless communication systems. In particular, the present invention relates to a method and apparatus for performing a handover between a Long Term Evolution (LTE) network and a second generation (2G)/third generation (3G) radio access network.
The advances made in wireless communication technology have resulted in the development of numerous mobile communication standards. These standards are broadly categorized into second generation (2G), third generation (3G) and the future, fourth generation (4G) technologies. Examples of 2G/3G technologies include Global System for Mobile communications (GSM), General Packet Radio Service (GPRS), Enhanced Data rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), and the like. The UMTS standard evolved to LTE technology under the Third Generation Partnership Project (3GPP). LTE technology offers a wireless broadband system with higher data rates, lower latency, and higher spectrum efficiency. It is expected that LTE networks will be deployed in densely populated geographical areas, in the initial phases. Thus, mobile terminals may have to perform handover between the LTE networks and the 2G/3G networks so that users can seamlessly move across geographical areas covered by different networks without an interruption in communication.
Certain mobile terminals available today are capable of operating in LTE as well as 2G/3G networks. These mobile terminals employ multiple protocol stacks for wireless communication. Due to the employment of multiple protocol stacks, these mobile terminals can perform a handover between the LTE network and the 2G/3G network. However, the presence of the multiple protocol stacks increases the architectural complexity of the mobile terminals. While the handover is being performed, some of the IP packets generated by the applications running on these mobile terminals may not reach their destination. These IP packets are either lost during their transmission over the wireless connection or are not transmitted by the mobile terminals due to the absence of a free channel. Further, after the handover is complete, some of these IP packets belonging to delay sensitive applications may not be retransmitted by the mobile terminals as it may be too late to transmit those packets.