CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No. 60/779,739 filed Mar. 7, 2006, and U.S. Provisional Application No. 60/792,935 filed Apr. 18, 2006 which are incorporated by reference as if fully set forth. This application is related to U.S. patent application Ser. No. 11/626,538 filed Jan. 24, 2007.
FIELD OF INVENTION
The present invention is related to a wireless communication system. More particularly, the present invention is related to a method and apparatus for supporting handoff and evolved Node B (ENB) relocation procedures in a single tunnel long term evolution (LTE)-based wireless communication system.
BACKGROUND
When an intra-SGSN handoff is implemented, the SGSN 210 switches the tunnel from an old RNC to a new RNC. A combined hard handover and SRNS relocation procedure is used to move the RAN to a core network (CN) connection point at the RAN side from the source serving RNC (SRNC) to the target RNC, while performing a hard handover decided by the RAN. In the procedure, the Iu links are relocated. If the target RNC is connected to the same SGSN as the source SRNC, an intra-SGSN SRNS relocation procedure is performed. If the routing area is changed, this procedure is followed by an intra-SGSN routing area update procedure. The SGSN detects that it is an intra-SGSN routing area update by noticing that it also handles the old routing area. In this case, the SGSN has the necessary information about the WRTU and there is no need to inform the HLR about the new WTRU location.
If the target RNC is connected to a different SGSN than the source SRNC, an inter-SGSN SRNS relocation procedure is performed. This procedure is followed by an inter-SGSN routing area update procedure.
A routing area update (RAU) is used to minimize the paging traffic within a wireless communication system that is grouped into clusters. Each cluster includes a group of cells (Node-Bs). Each cluster is defined by a unique identifier, (i.e., routing area identifier (ID)). Those WTRUs in the wireless communication system that travel across boundaries of the clusters have to perform a registration process called a routing area update. In the RAU, the WTRU informs the core network regarding which area of the system it is operating in. If the WTRU receives a terminated call, the core network pages the WTRU in the last known routing area. This eliminates the need to send a paging message for the WTRU throughout the entire system, which in turn significantly reduces the amount of signalling across the system. Thus, more processing power is allocated to user traffic. The RAU may require the establishment of a new connection between a GGSN and a new RNC. New processes and message formats are needed for a single tunnel approach as compared to those existing in a two tunnel approach.
Similarly,
LTE based networks are all IP Networks (AIPNs). IP traffic generated from the network operator, such as instant messaging, and non third generation partnership project (3G) IP traffic, such as wireless local area network (WLAN) traffic, is anchored and routed through the AGW 315. IP traffic destined for a WTRU does not need to be terminated at the MME/UPE 310. Therefore, a method and system for single IP tunnel functionality is desirable to reduce the delay and processing power at the MME/UPE in LTE-based networks.
SUMMARY
The present invention is related to establishing a single general packet radio service (GPRS) tunneling protocol (GTP) tunnel for user plane traffic between an access gateway (AGW) and an evolved Node B (ENB) in a long term evolution (LTE) based wireless communication network. ENB relocation is implemented in a wireless communication system including at least one WTRU, a source ENB, a target ENB, an old mobility management entity (MME)/user plane entity (UPE), a new MME/UPE and an AGW. An old GTP-U tunnel is established between the source ENB and the AGW. The source ENB sends a relocation required message to the old MME/UPE. The old MME/UPE sends a forward relocation request message to the new MME/UPE. The new MME/UPE sends a relocation request message to the target ENB which indicates a tunnel endpoint identity (TEID) of the AGW, an identification number of the WTRU and the packet data protocol (PDP) address of the WTRU. The new MME/UPE sends an update PDP context request message to the AGW which indicates the TEID of the target ENB. The AGW updates a binding of the target ENB TEID with the PDP address and the identification number of the WTRU. A new GTP-U tunnel is established between the target ENB and the AGW, and the old GTP-U tunnel is released. Both inter-location area (LA) and intra-LA handover scenarios are addressed.
A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example and to be understood in conjunction with the accompanying drawings wherein:
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
When referred to hereafter, the terminology “wireless transmit/receive unit (WTRU)” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to a Node-B, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment.
The features of the present invention may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components.
In accordance with the present invention, the mobility in LTE-based systems is facilitated by anchoring IP sessions at the AGW.
In the case of a single tunnel, the MME/UPE should connect the ENB TEID and the AGW TEID for the user plane by informing each end point of the corresponding TEID of the other end point, (i.e., informing the AGW of the ENB TEID and informing the ENB of the AGW TEID). In the case of a handoff between ENBs, the MME/UPE is responsible for updating and providing the AGW with new ENB TEID information and the establishment of the single tunnel.
Still referring to
In step 832, an old tunnel is established between the source RNC 810 and the GGSN 830. The establishment of the old tunnel may occur, for example, in accordance with the LTE attach procedure described above with respect to
In step 833, the WTRU may optionally report the quality of candidate cells to the source ENB 1110. The radio resource management (RRM) function of the source ENB 1110 may decide the WTRU 805 should be handed over to a target cell. The decision may be based on the measurement report 833 and various other performance and operating criteria as desired.
In step 834, the source ENB 810 decides to perform/initiate ENB relocation. If the measurement report 833 is proved by the WTRU 805, the decision may be based on the reported quality and load of the candidate cells. At this point, both uplink and downlink user and control data flows via at least one of the following tunnels: a radio bearer between the WTRU 805 and the source ENB 810, a single GTP user plane tunnel between the source ENB 810 and the AGW 830; a RANAP control plane tunnel(s) between the source ENB 810 and the old MME/UPE 820; and GTP control plane tunnel(s) between the old-MME/UPE 820 and the AGW 830.
In step 836, the source ENB 810 sends a relocation required message, (including relocation type, cause, source ID, target ID, source ENB to target ENB transparent container), to the old MME/UPE 820. The source ENB 810 sets the relocation type to “WTRU not involved”. The source ENB to target ENB transparent container includes the necessary information for relocation coordination, security functionality and radio resource control (RRC) protocol context information, (including WTRU capabilities).
The old MME/UPE 820 determines from the target ID if the ENB relocation is an intra-MME/UPE ENB relocation or an inter-MME/UPE ENB relocation. In the case of an inter-MME/UPE ENB relocation, the old MME/UPE 820 initiates the relocation resource allocation procedure by sending a forward relocation request message, (IMSI, TEID signaling, MM context, PDP context, target identification, RAN transparent container, RANAP cause) to the new MME/UPE 825 (step 838). For relocation to an area where intra domain connection of RAN nodes to multiple CN nodes is used, the old MME/UPE 820 may, (if it provides intra domain connection of RAN nodes to multiple CN nodes), have multiple target MME/UPEs for each relocation target in a pool area, in which case the old MME/UPE 820 will select one of them to become the new MME/UPE 825. The PDP context contains an AGW address for user plane and uplink TEID for data, (to this AGW address and uplink TEID, for data the old MME/UPE 820 and the new MME/UPE 825 send uplink packets). At the same time, a timer is started on the MM and PDP contexts in the old MME/UPE 820. The forward relocation request message of step 838 is applicable only in the case of inter-MME/UPE ENB relocation.
In step 840, the new MME/UPE 825 sends a relocation request message, (including a permanent non-access stratum (NAS) WTRU identity, cause, CN domain indicator, source RNC to target RNC transparent container, RABs to be setup),to the target RNC 815.
In accordance with the present invention, the relocation request message also indicates a the TEID of the AGW 830 and the association between both the MSISDN of the WTRU 805 and its PDP address with the TEID of the AGW 830
In step 842, RABs are established and a tunnel setup at the target RNC 815 is established in accordance with the present invention. Only the Iu bearers of the RABs are setup between the target ENB 815 and the new MME/UPE 825, since the existing RABs will be reallocated between the WTRU 805 and the target ENB 815 when the target ENB 815 begins handling traffic destined for the WTRU 805. For each requested RAB, the RAB's information elements may contain information such as RAB ID, RAB parameters, transport layer address and Iu transport association. The RAB ID information element contains the network layer service access point identifier (NSAPI) value, and the RAB parameters information element provides the quality of service (QoS) profile. The transport layer address is the MME/UPE address for user data, and the Iu transport association corresponds to the uplink TEID data.
After all necessary resources for accepted RABs including the Iu user plane are successfully allocated, the target ENB 815 sends a relocation request acknowledge message, (RABs setup, RABs failed to setup), to the new MME/UPE 825 (step 844). Each RAB to be setup is defined by a transport layer address, which is the address of the target ENB 815 for user data, and an Iu transport association, which corresponds to the downlink TEID for user data. For each RAB to be set up, the target ENB 815 may simultaneously receive downlink user packets both from the source ENB 810 and from the new MME/UPE 825.
When resources for the transmission of user data between the target ENB 815 and the new MME/UPE 825 have been allocated, and the new MME/UPE 825 is ready for relocation, a forward relocation response message, (cause, RANAP cause, and RAB setup information), is sent from the new MME/UPE 825 to the old MME/UPE 820 (step 846). The forward relocation response message indicates that the target ENB 815 is ready to receive from source ENB 810 the forwarded downlink PDUs, (i.e., the relocation resource allocation procedure is terminated successfully). The RANAP cause is information from the target ENB 815 to be forwarded to the source ENB 810. The RAB setup information, one information element for each RAB, contains the ENB TEID and the ENB IP address for data forwarded from the source ENB 810 to the target ENB 815. If the target ENB 815 or the new MME/UPE 825 failed to allocate resources, the RAB setup information element contains only NSAPI indicating that the source ENB 810 shall release the resources associated with the NSAPI. The forward relocation response message of step 846 is applicable only in case of inter-MME/UPE ENB relocation.
The old MME/UPE 820 continues ENB relocation by sending a relocation command message, (RABs to be released, and RABs subject to data forwarding), to the source ENB 810 (step 848). The old MME/UPE 820 determines the RABs to be subject for data forwarding based on QoS, and those RABs shall be contained in RABs subject to data forwarding. For each RAB subject to data forwarding, the information element shall contain an RAB ID, transport layer address, and Iu transport association. These are the same transport layer address and Iu transport association that the target ENB 815 had sent to the new MME/UPE 825 in the relocation request acknowledge message of step 844, and these are used for forwarding of downlink PDUs from the source ENB 810 to the target ENB 815. The source ENB 810 is now ready to forward downlink user data directly to the target ENB 815 over the Iu interface. This forwarding is performed for downlink user data only.
In step 850, the source ENB 810 may, according to the QoS profile, begin the forwarding of data to the target ENB 815 for the RABs to be subject for data forwarding. The data forwarding during relocation shall be carried out through the Iu interface, meaning that the data exchanged between the source ENB 810 and the target ENB 815 are duplicated in the source ENB 810 and routed at IP layer towards the target ENB 815. For each radio bearer which uses a lossless packet data convergence protocol (PDCP), the GTP-PDUs related to transmitted but not yet acknowledged PDCP-PDUs are duplicated and routed at IP layer towards the target ENB 815 together with their related downlink PDCP sequence numbers. The source ENB 810 continues transmitting duplicates of downlink data and receiving uplink data. Before the role of the serving ENB is taken over by the target ENB 815, and when downlink user plane data starts to arrive at the target ENB 815, the target ENB 815 may buffer or discard arriving downlink GTP-PDUs according to the related QoS profile.
It should be noted that the order of steps 850-876 of the ENB relocation procedure shown in
Before sending the relocation commit message at step 852 for the uplink and downlink data transfer in the source ENB 810, the source ENB 810 is suspended for RABs, which require delivery order. The source ENB 810 shall start the data-forwarding timer. When the source ENB 810 is ready, the source ENB 810 triggers the execution of relocation of ENB by sending a relocation commit message, (ENB contexts), to the target ENB 815 (step 852). The purpose of this procedure is to transfer ENB contexts from the source ENB 810 to the target ENB 815. ENB contexts are sent for each concerned RAB and contain the sequence numbers of the GTP-PDUs next to be transmitted in the uplink and downlink directions and the next PDCP sequence numbers that would have been used to send and receive data from the WTRU 805. For PDP context(s) using delivery order not required (QoS profile), the sequence numbers of the GTP-PDUs next to be transmitted are not used by the target ENB 815. PDCP sequence numbers are only sent by the source ENB 810 for radio bearers, which used lossless PDCP. The use of lossless PDCP is selected by the source ENB 810 when the radio bearer is set up or reconfigured.
If delivery order is required (QoS profile), consecutive GTP-PDU sequence numbering shall be maintained throughout the lifetime of the PDP context(s). Therefore, during the entire ENB relocation procedure for the PDP context(s) using delivery order required (QoS profile), the responsible GTP-U entities, (ENBs and AGWs), shall assign consecutive GTP-PDU sequence numbers to user packets belonging to the same PDP context for uplink and downlink, respectively.
In step 854, the target ENB 815 sends a relocation detect message to the new MME/UPE 825 when the relocation execution trigger is received. For ENB relocation type “WTRU not involved”, the relocation execution trigger is the reception of the relocation commit message at step 852. When the relocation detect message is sent at step 854, the target ENB 815 shall start serving ENB operation.
At step 856, the target ENB 815 sends a RAN mobility information message that contains WTRU information elements and CN information elements. The WTRU information elements include, among others, a new ENB identity and a subscriber radio network temporary identity (S-RNTI). The CN information elements contain, among others, location area identification and routing area identification. The procedure is coordinated in all Iu signaling connections existing for the WTRU 805.
The target ENB 815 establishes and/or restarts the RLC, and exchanges the PDCP sequence numbers, (PDCP sequence number (SNU), PDCP sequence number downlink (SND)), between the target ENB 815 and the WTRU 805. The PDCP SND is the PDCP sequence number for the next expected in-sequence downlink packet to be received in the WTRU 805 per radio bearer, which used lossless PDCP in the source RNC 810. The PDCP SND confirms all mobile-terminated packets successfully transferred before the ENB relocation. If the PDCP SND confirms reception of packets that were forwarded from the source ENB 810, the target ENB 815 shall discard these packets. The PDCP SNU is the PDCP sequence number for the next expected in-sequence uplink packet to be received in the ENB per radio bearer, which used lossless PDCP in the source ENB 810. The PDCP SNU confirms all WTRU originated packets successfully transferred before the ENB relocation. If PDCP SNU confirms reception of packets that were received in the source ENB 810, the WTRU 805 shall discard these packets.
Upon reception of the RAN mobility information message at step 856, the WTRU 805 may start sending uplink user data to the target ENB 815. When the WTRU 805 has reconfigured itself, it sends a RAN mobility information confirm message to the target ENB 815 at step 858. This indicates that the WTRU 805 is also ready to receive downlink data from the target ENB 815.
In step 860, the new MME/UPE 825 sends an update PDP context request message to the AGW 830 which indicates the TEID of the target ENB 815 in accordance with the present invention. In response, the AGW 830 updates the binding of the TEID of the target ENB 815 with the PDP address and the MSISDN of the WTRU 805. Thus, MME/UPE 825 sends the name of the new connection that data will be forwarded to by the AGW 830. Once this information is received, the AGW 830 updates the information pertaining to this tunnel, (i.e., new destination).
For all of the RABs, the target ENB 815 starts uplink reception of data and starts transmission of uplink GTP-PDUs towards the new MME/UPE 825, and the target ENB 815 starts processing the already buffered and the arriving downlink GTP-PDUs and starts downlink transmission towards the WTRU 805.
Upon receipt of the relocation detect message at step 854, the CN may switch the user plane from the source ENB 810 to the target ENB 815. If the ENB relocation is an inter-MME/UPE ENB relocation, the new MME/UPE 825 sends update PDP context request messages, (new MME/UPE address, MME/UPE TEID, QoS negotiated), to the AGW concerned. The MME/UPEs update their PDP context fields and return an update PDP context response (AGW TEID) at step 862. A new GTP user plane tunnel is then established between the target ENB 815 and the AGW 830 at step 864 in accordance with the present invention.
If the new MME/UPE 825 has already received the update PDP context response message from the AGW 830, the new MME/UPE 825 forwards the uplink user data to the AGW 830 over the new GTP user plane tunnel. Otherwise, the new MME/UPE 825 forwards the uplink user data to the IP address of the AGW 830 and TEID(s), which the new MME/UPE 825 had received earlier by the forward relocation request message at step 838.
When the target ENB 815 receives the RAN mobility information confirm message at step 858, (i.e., the ID of the target ENB 815 and an S-RNTI are successfully exchanged with the WTRU 805 by the radio protocols), the target ENB 815 initiates a relocation complete procedure by sending a relocation complete message to the new MME/UPE 825 at step 866.
The purpose of the relocation complete procedure is to indicate by the target ENB 815 the completion of the ENB relocation to the CN. If the user plane has not been switched at relocation detect and upon reception of relocation complete, the CN switches the user plane from the source ENB 810 to the target ENB 815. If the ENB relocation is an inter-MME/UPE ENB relocation, the new MME/UPE 825 signals to the old MME/UPE 820 the completion of the ENB relocation procedure by sending a forward relocation complete message at step 868.
Upon receiving the forward relocation complete message, or if an inter-MME/UPE ENB relocation is taking place, the old MME/UPE 820 sends a forward relocation complete acknowledge message to the new MME/UPE at step 870, and the old MME/UPE 820 sends an Iu release command message to the source ENB 810 at step 872. When the ENB data-forwarding timer expires, the source ENB 810 responds with an Iu release complete message at step 874.
After the WTRU 805 has finished the RNTI reallocation procedure and, if the new routing area identification is different from the old one, the WTRU 805 initiates a routing area update procedure at step 876.
In step 1132, an old tunnel is established between the source ENB 1110 and the AGW 1130. This old tunnel may be established, for example, by way of the LTE attach procedure described above with reference to
In step 1133, the WTRU may optionally report the quality of candidate cells to the source ENB 1110. The radio resource management (RRM) function of the source ENB 1110 may decide the WTRU 1105 should be handed over to a target cell. The decision may be based on the measurement report 1133 and various other performance and operating criteria as desired.
In step 1134, the source ENB 1110 decides to perform/initiate a combined hard handover and ENB relocation. If the measurement report 1133 is proved by the WTRU 1105, the decision may be based on the reported quality and load of the candidate cells. At this point, both uplink and downlink user and control data flows via at least one of the following tunnels: a radio bearer between the WTRU 1105 and the source ENB 1110; GTP user plane tunnel between the source ENB and the AGW; RANAP control plane tunnel(s) between the source ENB 1110 and the old MME/UPE 1120; and GTP control plane tunnel(s) between the old MME/UPE 1120 and the AGW 1130.
In step 1136, the source ENB 1110 sends a relocation required message, (including relocation type, cause, source ID, target ID, source ENB to target ENB transparent container), to the old MME/UPE 1120. The source ENB 1110 sets the relocation type to “WTRU involved”. The source ENB to target ENB transparent container includes the necessary information for relocation coordination, security functionality and RRC protocol context information, (including WTRU capabilities).
The old MME/UPE 1120 determines from the target ID if the ENB relocation is an intra-MME/UPE ENB relocation or an inter-MME/UPE ENB relocation. In the case of an inter-MME/UPE ENB relocation, the old MME/UPE 1120 initiates the relocation resource allocation procedure by sending a forward relocation request message, (IMSI, TEID signaling, MM context, PDP context, target identification, RAN transparent container, RANAP cause) to the new MME/UPE 1125 (step 1138). For relocation to an area where intra domain connection of RAN nodes to multiple CN nodes is used, the old MME/UPE 1120 may, (if it provides intra domain connection of RAN nodes to multiple CN nodes), have multiple target MME/UPEs for each relocation target in a pool area, in which case the old MME/UPE 1120 will select one of them to become the new MME/UPE 1125. The PDP context contains an AGW address for user plane and uplink TEID for data, (to this AGW address and uplink TEID, for data the old MME[UPE 1120 and the new MME/UPE 1125 send uplink packets). At the same time, a timer is started on the MM and PDP contexts in the old MME/UPE 1120. The forward relocation request message of step 1138 is applicable only in the case of inter-MME/UPE ENB relocation.
In step 1140, the new MME/UPE 1125 sends a relocation request message, (including a permanent non-access stratum (NAS) WTRU identity, cause, CN domain indicator, source ENB to target ENB transparent container, RABs to be setup),to the target ENB 1115. For relocation to an area where intra domain connection of RAN nodes to multiple CN Nodes is used, the old MME/UPE 1120 may, if it provides intra domain connection of RAN nodes to multiple CN nodes, have multiple target MME/UPEs for each relocation target in a pool area, in which case the old MME/UPE 1120 will select one of them to become the new MME/UPE 1125. PDP context contains an AGW address for user plane and uplink TEID for data, (to this AGW address and uplink TEID for data). The old MME/UPE 1120 and the new MME/UPE 1125 send uplink packets. At the same time, a timer is started on the MM and PDP contexts in the old MME/UPE 1120. The forward relocation request message is applicable only for inter-MME/UPE ENB relocation.
In accordance with the present invention, the relocation request message also indicates the TEID of the AGW 1130 and the association between both the MSISDN of the WTRU 1105 and its PDP address with the TEID of the AGW 1130.
In step 1142, RABs are established and a tunnel setup at the target ENB 1115 is established in accordance with the present invention. Only the Iu bearers of the RABs are setup between the target ENB 1115 and the new MME/UPE 1125, since the existing RABs will be reallocated between the WTRU 1105 and the target ENB 1115. For each requested RAB, the RAB's information elements may contain information such as RAB ID, RAB parameters, transport layer address and Iu transport association. The RAB ID information element contains the network layer service access point identifier (NSAPI) value, and the RAB parameters information element provides the quality of service (QoS) profile. The transport layer address is the MME/UPE address for user data, and the Iu transport association corresponds to the uplink TEID data.
After all necessary resources for accepted RABs including the Iu user plane are successfully allocated, the target ENB 1115 sends a relocation request acknowledge message, (RABs setup, RABs failed to setup), to the new MME/UPE 1125 (step 1144). Each RAB to be setup is defined by a transport layer address, which is the address of the target ENB 1115 for user data, and an Iu transport association, which corresponds to the downlink TEID for user data. For each RAB to be set up, the target ENB 1115 may simultaneously receive downlink user packets both from the source ENB 1110 and from the new MME/UPE 1125.
When resources for the transmission of user data between the target ENB 1115 and the new MME/UPE 1125 have been allocated, and the new MME/UPE 1125 is ready for relocation, a forward relocation response message, (cause, RAN transparent container, RANAP cause, target-ENB information), is sent from the new MME/UPE 1125 to the old MME/UPE 1120, (step 1146). The forward relocation response message indicates that the target ENB 1115 is ready to receive from the source ENB 1110 the forwarded downlink PDUs, (i.e., the relocation resource allocation procedure is terminated successfully). The RAN transparent container and the RANAP cause are information from the target ENB 1115 to be forwarded to the source ENB 1110. The target ENB information, one information element for each RAB to be set up, contains the ENB TEID and the ENB IP address for data forwarded from the source ENB 1110 to the target ENB 1115. The forward relocation response message of step 1146 is applicable only for inter-MME/UPE ENB relocation.
The old MME/UPE 1120 continues the relocation of ENB by sending a relocation command message, (RABs to be released, and RABs subject to data forwarding), to the source ENB 1110 (step 1148). The old MME/UPE 1120 determines the RABs to be subject for data forwarding based on QoS, and those RABs shall be contained in RABs subject to data forwarding. For each RAB subject to data forwarding, the information element shall contain an RAB ID, transport layer address, and Iu transport association. These are the same transport layer address and Iu transport association that the target ENB 1115 had sent to the new MME/UPE 1125 in the relocation request acknowledge message of step 1144, and these are used for forwarding of downlink PDUs from the source ENB 1110 to the target ENB 1115. The source ENB 1110 is now ready to forward downlink user data directly to the target ENB 1115 over the Iu interface. This forwarding is performed for downlink user data only.
In step 1150, the source ENB 1110 may, according to the QoS profile, begin the forwarding of data to the target ENB 1115 for the RABs to be subject for data forwarding. The data forwarding at ENB relocation shall be carried out through the Iu interface, meaning that the data (GTP-PDUs) exchanged between the source ENB 1110 and the target ENB 1115 are duplicated in the source ENB 1110 and routed at the IP layer towards the target ENB 1115. For each radio bearer which uses a lossless packet data convergence protocol (PDCP), the GTP-PDUs related to transmitted but not yet acknowledged PDCP-PDUs are duplicated and routed at IP layer towards the target ENB 1115 together with their related downlink PDCP sequence numbers. The source ENB 1110 continues transmitting duplicates of downlink data and receiving uplink data. Before the role of the serving ENB is not yet taken over by the target ENB 1115, and when downlink user plane data starts to arrive at the target ENB 1115, the target ENB 1115 may buffer or discard arriving downlink GTP-PDUs according to the related QoS profile.
It should be noted that the order of steps 1150-1184 of the single tunnel combined hard handover and ENB relocation procedure shown in
Before sending the RRC message in step 1152, the uplink and downlink data transfer is suspended in the source ENB 1110 for RABs, which require delivery order. The RRC message is, for example, physical channel reconfiguration for RNS to RNS relocation, or intersystem to UTRAN handover for BSS to RNS relocation, or handover from UTRAN command for BSS relocation, or handover command for BSS to BSS relocation. When the source ENB 1110 is ready, the source ENB 1110 triggers the execution of ENB relocation by sending to the WTRU 1105 the RRC message provided in the target ENB 1115 to source ENB 1110 transparent container, e.g., a physical channel reconfiguration (WTRU information elements, CN information elements) message (step 1152). WTRU information elements include, among others, a new serving ENB identity and S-RNTI. CN information elements contain, among others, location area identification and routing area identification.
The source ENB 1110 continues the execution of ENB relocation by sending a forward serving ENB context (RAB contexts) message to the target ENB 1115 via the old MME/UPE 1120 and the new MME/UPE 1125 (steps 1154, 1156 and 1160). The forward serving ENB context message is acknowledged by a forward serving ENB context acknowledge message, from new MME/UPE 1125 to the old MME/UPE 1120 (step 1158). The purpose of this procedure is to transfer serving ENB contexts from the source ENB 1110 to the target ENB 1115, and to move the serving ENB role from the source ENB 1110 to the target ENB 1115. Serving ENB contexts are sent for each concerned RAB and contain the sequence numbers of the GTP PDUs next to be transmitted in the uplink and downlink directions and the next PDCP sequence numbers that would have been used to send and receive data from the WTRU 1105. PDCP sequence numbers are only sent by the source ENB 1110 for the radio bearers which used lossless PDCP. The use of lossless PDCP is selected by the source ENB 1110 when the radio bearer is set up or reconfigured. For PDP context(s) using delivery order not required (QoS profile), the sequence numbers of the GTP-PDUs next to be transmitted are not used by the target ENB 1115.
If delivery order is required (QoS profile), consecutive GTP-PDU sequence numbering shall be maintained throughout the lifetime of the PDP context(s). Therefore, during the entire serving ENB relocation procedure for the PDP context(s) using delivery order required (QoS profile), the responsible GTP-U entities (the ENBs 1110 and 1115, and the AGW 1130) shall assign consecutive GTP-PDU sequence numbers to user packets belonging to the same PDP context uplink and downlink, respectively.
The target ENB 1115 establishes and/or restarts the RLC and exchanges the PDCP sequence numbers, (PDCP-SNU, PDCP-SND), between the target ENB 1115 and the WTRU 1105. PDCP-SND is the PDCP sequence number for the next expected in-sequence downlink packet to be received by the WTRU 1105 per radio bearer, which used lossless PDCP in the source ENB 1110. PDCP-SND confirms all mobile terminated packets successfully transferred before the serving ENB relocation. If PDCP-SND confirms reception of packets that were forwarded from the source ENB 1110, then the target ENB 1115 shall discard these packets. PDCP-SNU is the PDCP sequence number for the next expected in-sequence uplink packet to be received in the ENB per radio bearer, which used lossless PDCP in the source ENB 1110. PDCP-SNU confirms all mobile originated packets successfully transferred before the serving ENB relocation. If PDCP-SNU confirms reception of packets that were received in the source ENB 1110, the WTRU 1105 discards these packets.
The target ENB 1115 sends a relocation detect message to the new MME/UPE 1164 when the relocation execution trigger is received (step 1164). For ENB relocation type “WTRU involved”, the relocation execution trigger may be received from the Uu interface; (i.e., when the target ENB 1115 detects the WTRU 1105 on the lower layers (step 1162)). When the relocation detect message is sent at step 1164, the target ENB 1115 starts serving ENB operation.
In step 1166, the new MME/UPE 1125 sends an update PDP context request message to the AGW 1130 which indicates a single tunnel configuration and the TEID of the target ENB 1115 in accordance with the present invention. In response, the AGW 1130 updates the binding of the TEID of the target ENB 1115 with the PDP address and the MSISDN of the WTRU 1105.
For all of the RABs, the target ENB 1115 starts uplink reception of data and start transmission of uplink GTP-PDUs towards the new MME/UPE 1125, and the target ENB 1115 starts processing the already buffered and the arriving downlink GTP-PDUs and starts downlink transmission towards the WTRU 1105.
Upon receipt of the relocation detect message at step 1164, the CN may switch the user plane from the source ENB 1110 to the target ENB 1115. If the serving ENB relocation is an inter-MME/UPE ENB relocation, the new MME/UPE 1125 sends update PDP context request messages, (new MME/UPE address, MME/UPE TEID, QoS negotiated), to the AGW concerned. The AGW updates its PDP context fields and return an update PDP context response (AGW TEID) at step 1170. A new GTP user plane tunnel is the established between the target ENB 1115 and the AGW 1130 at step 1174 in accordance with the present invention.
If the new MME/UPE 1125 has already received the update PDP context response message from the AGW 1130, the new MME/UPE 1125 forwards the uplink user data to the AGW 1130 over the new GTP user plane tunnel. Otherwise, the new MME/UPE 1125 forwards the uplink user data to the IP address of the AGW 1130 and TEID(s), which the new MME/UPE 1125 had received earlier by the forward relocation request message at step 1138.
When the WTRU 1105 has reconfigured itself, it sends an RRC message, (e.g., a physical channel reconfiguration complete message), to the target ENB 1115 (step 1168). If a forward serving ENB context message with the sequence numbers is received at step 1160, the exchange of packets with the WTRU 1105 may start. If this message is not yet received, the target ENB 1115 may start the packet transfer for all RABs, which do not require maintaining the delivery order.
When the target ENB 1115 receives the RRC message at step 1168, the target ENB 1115 initiates a relocation complete procedure by sending a relocation complete message to the new MME/UPE 1125 at step 1172. The purpose of the relocation complete procedure is to indicate by the target ENB 1115 the completion of the serving ENB relocation to the CN. If the user plane has not been switched at relocation detect and upon reception of relocation complete, the CN switches the user plane from the source ENB 1110 to the target ENB 1115. If the ENB relocation is an inter-MME/UPE ENB relocation, the new MME/UPE 1125 signals to the old MME/UPE 1120 the completion of the serving ENB relocation procedure by sending a forward relocation complete message at step 1176.
Upon receiving the forward relocation complete message, or if an inter-MME/UPE serving ENB relocation is taking place, the old MME/UPE 1120 sends a forward relocation complete acknowledge message to the new MME/UPE at step 1178, and the old MME/UPE 1120 sends an Iu release command message to the source ENB 1110 at step 1180. When the ENB data-forwarding timer expires, the source ENB 1110 responds with an Iu release complete message at step 1182.
After the WTRU 1105 has finished the reconfiguration procedure and if the new routing area identification is different from the old one, the WTRU 1105 initiates a routing area update procedure at step 1184.
Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. The methods or flow charts provided in the present invention may be implemented in a computer program, software, or firmware tangibly embodied in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage medium includes a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs).
Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine.
A processor in association with software may be used to implement a radio frequency transceiver for use in a wireless transmit receive unit (WTRU), user equipment (UE), terminal, base station, radio network controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any wireless local area network (WLAN) module.