METHOD AND APPARATUS FOR PERFORMING HANDOVER IN A WIRELESS COMMUNICATION SYSTEM

• US 20090232097A1
• Filed: 03/10/2009
• Published: 09/17/2009
• Est. Priority Date: 03/13/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: TANEJA, Mukesh
• Granted Patent: US 8,199,719 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/02 Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
• CPC Class Codes: H04W 36/023 Buffering or recovering information during reselection
• CPC Class Codes: H04W 36/1443 between licensed networks
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems

Abstract

A method for performing handover by wireless User Equipment (UE) is provided. The UE includes a Long Term Evolution-Mobile Extreme Convergence (LTE-MXC) application processor, a LTE processor and a Digital Signal Processor (DSP). The UE buffers a set of IP packets when a Radio Access Technology (RAT) indicator is less than a pre-defined threshold and sends the set of IP packets to the LTE processor and the DSP. The LTE processor transmits the set of IP packets to the LTE network and sends acknowledgement signals to the LTE-MXC application processor and the DSP. When the handover is complete, the LTE processor sends the transmission status of the set of IP packets to the DSP. The UE also includes multimode Radio Resource Control (RRC) and Non-Access Stratum (NAS) modules.

Claims

1. A method for performing handover by a wireless user equipment (UE), the wireless UE being in communication with a wireless communication system, the wireless communication system comprising a plurality of radio access networks (RANs), at least one of the plurality of radio access networks being a long term evolution (LTE) network, the wireless UE comprising a Long Term Evolution-Mobile Extreme Convergence (LTE-MXC) application processor, a LTE processor and a digital signal processor supporting MXC modem (UMTS/GSM) functionality, the method comprising:

buffering a set of IP packets when a radio access technology (RAT) indicator is less than a pre-defined threshold;

initiating a handover by at least one of the wireless UE and the LTE network;

sending the set of IP packets to the LTE processor and the digital signal processor when the handover is initiated;

transmitting the set of IP packets to the LTE network by the LTE processor;

sending one or more acknowledgment signals to at least one of the LTE-MXC application processor and the digital signal processor, wherein the one or more acknowledgement signals indicate a successfully transmitted subset of the set of IP packets sent to the LTE processor;

sending one or more messages to the digital signal processor and the LTE-MXC application processor when the handover is complete, wherein at least one of the one or more messages indicates transmission status of the set of IP packets sent to the LTE processer; and

transmitting a subset of the set of IP packets to one of the plurality of RANs based on the received one or more messages, wherein the subset of IP packets is transmitted by the digital signal processor.

2. The method for performing handover of claim 1, wherein the handover performed by the wireless UE is between the LTE network and one of the plurality of RANs, wherein the one of the plurality of RANs is one of a UMTS radio access network (UTRAN) and a GSM radio access network (GRAN).

3. The method for performing handover of claim 1, further comprising generating the set of IP packets prior to buffering the set of IP packets, wherein the set of IP packets is generated by the LTE-MXC application processor.

4. The method for performing handover of claim 1, further comprising monitoring the RAT indicator.

5. The method for performing handover of claim 1, further comprising sending the set of IP packets to the LTE processor prior to the initiating of the handover.

6. The method for performing handover of claim 1, further comprising sending the one or more acknowledgment signals to the LTE-MXC application processor prior to the initiating of the handover.

7. The method for performing handover of claim 1, further comprising dropping the successfully transmitted subset of IP packets when the LTE-MXC application processor receives the one or more acknowledgement signals from the LTE processor.

8. The method for performing handover of claim 1, wherein the successfully transmitted subset of IP packets are IP packets received by the LTE network from the LTE processor.

9. The method for performing handover of claim 1, wherein the transmission status of the set of IP packets includes information about the subset of IP packets, wherein the subset of IP packets includes IP packets not successfully transmitted to the LTE network by the LTE processor.

10. The method for performing handover of claim 1, wherein the subset of IP packets is transmitted by the digital signal processor when the handover is complete.

11. A wireless user equipment (UE) for communication via a wireless communication system, the wireless communication system comprising a plurality of radio access networks (RANs), at least one of the plurality of radio access networks being a Long Term Evolution (LTE) network, the wireless UE comprising:

a Long Term Evolution-Mobile Extreme Convergence (LTE-MXC) application processor configured to generate, buffer and send IP packets;

a multi-mode radio resource control (MMd_RRC) module located within the LTE-MXC application processor for establishing a wireless connection between the wireless UE and at least one of the plurality of RANs;

a multi-mode non-access stratum (MMd NAS) module located within the LTE-MXC application processor for establishing a wireless connection between the wireless UE and at least one of a core network providing circuit-switched services and a core network providing packet-switched services;

a LTE processor, operatively coupled to the LTE-MXC application processor, for receiving IP packets from the LTE-MXC application processor, sending messages to the LTE-MXC application processor and transmitting IP packets to the LTE network, wherein at least one of the messages indicates transmission status of the IP packets received by the LTE processor; and

a digital signal processor operatively coupled to the LTE processor and the LTE-MXC application processor, wherein the digital signal processor is configured to receive IP packets from the LTE-MXC application processor, receive messages from the LTE processor, and transmits IP packets to one of the plurality of RANs based on the received messages.

12. The wireless UE of claim 11, wherein the MMd_RRC module is capable of establishing a wireless connection between the wireless UE and at least one of the plurality of RANs based on a Radio Access Technology (RAT) indicator.

13. The wireless UE of claim 11, wherein the messages include acknowledgement signals, wherein the acknowledgement signals indicate successfully transmitted IP packets.

14. The wireless UE of claim 13, wherein the LTE-MXC application processor is further configured to drop IP packets based on the acknowledgement signals received from the LTE processor.

15. The wireless UE of claim 13, wherein the digital signal processor is further configured to drop IP packets based on the acknowledgement signals received from the LTE processor.

16. The wireless UE of claim 11, wherein the transmission status of IP packets includes information about IP packets not successfully transmitted to the LTE network by the LTE processor.

17. The wireless UE of claim 11, further comprising an LTE-MXC baseband processor, wherein the MMd_RRC module and the MMd_NAS module are located in the LTE-MXC baseband processor 18. A wireless user equipment (UE) comprising a Long Term Evolution-Mobile Extreme Convergence (LTE-MXC) application processor, a LTE processor and a digital signal processor supporting MXC modem (UMTS/GSM) functionality, the wireless UE further comprising:

a multi-mode radio resource control (MMd_RRC) module configured to operate in a MMd_RRC_detached state, a MMd_RRC_connected state and a MMd_RRC_idle state, wherein in the MMd_RRC_detached state the multimode RRC module is configured to;

monitor a radio access technology (RAT) indicator, establish a wireless connection between the wireless UE and at least one of a LTE cell, a UMTS cell and a GSM cell based on the RAT indicator, and

perform a state transition to the MMd_RRC_connected state by cell reselection,

wherein in the MMd_RRC_connected state the MMd_RRC module is configured to;

perform a handover from an LTE_connected state to an UTRAN_connected state and vice-versa,

perform a handover from the LTE_connected state to a GSM_connected state and vice-versa,

perform a handover from the LTE_connected state to the GSM_connected state via a GPRS_Packet_Transfer_Mode state and vice-versa,

perform a handover from the LTE_connected state to the GPRS_Packet_Transfer_Mode state and vice-versa,

perform a handover from the UTRAN_connected state to the GSM_connected state and vice-versa,

perform a state transition to the MMd_RRC_idle state when at least one of the LTE cell, the GSM cell and the UMTS cell is inactive for a time period greater than a first predefined time threshold, and

perform a state transition to the MMd_RRC_detached state when the wireless connection between the wireless UE and at least one of the LTE cell, the GSM cell and the UMTS cell is released,

wherein in the MMd_RRC_idle state the MMd_RRC module is configured to;

perform a state transition to the MMd_RRC_detached state, and

perform a state transition to the MMd_RRC_connected state when there is new activity on the wireless connection between the wireless UE and at least one of the LTE cell, the GSM cell and the UMTS cell; and

a multi-mode non-access stratum (MMd NAS) module, wherein the MMd_NAS module is configured to operate in a MMd_NAS_detached state, a MMd_NAS_connected state, and a MMd_NAS_idle state, wherein the MMd_NAS module is further configured to;

establish a wireless connection between the wireless UE and at least one of a core network providing circuit-switched services and a core network providing packet-switched services in the MMd_NAS_detached state,

wherein in the MMd_NAS_connected state, the MMd_NAS module is configured to;

perform a state transition to the MMd_NAS_idle state when the wireless connection between the wireless UE and at least one of the core network providing packet-switched services and the core network providing circuit-switched services is released,

perform a state transition to the MMd_NAS_idle state when the LTE network is inactive for a time period greater than a third predefined time threshold, and

perform a state transition to the MMd_NAS_detached state when the wireless connection between the wireless UE and the LTE network is released,

wherein in the MMd_NAS_idle state, the MMd_NAS module is configured to;

perform a state transition to the MMd_NAS_connected state when there is new activity on the wireless connection between the wireless UE and the LTE network,

perform a state transition to the MMd_NAS_connected state when the wireless connection between the wireless UE and at least one of the core network providing packet-switched services and the core network providing circuit-switched services is established, and

perform a state transition to the MMd_NAS_detached state.