HK1248441B - Handover using group evolved packet system (eps) bearers - Google Patents

Description

Handover using Evolved Packet System (EPS) bearer

Background Art

Wireless mobile communication technology uses various standards and protocols to transmit data between nodes (e.g., transmission stations) and wireless devices (e.g., mobile devices). Some wireless devices use orthogonal frequency division multiple access (OFDMA) for communication in downlink (DL) transmissions and single-carrier frequency division multiple access (SC-FDMA) for communication in uplink (UL) transmissions. Standards and protocols that use orthogonal frequency division multiplexing (OFDM) for signal transmission include: the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE); the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standards (e.g., 802.16e, 802.16m), which is often referred to in the industry as WiMAX (Worldwide Interoperability for Microwave Access); and the IEEE 802.11 standard, which is often referred to in the industry as WiFi.

In a 3GPP radio access network (RAN) LTE system, a node, which can be a combination of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (often also referred to as an evolved Node B, enhanced Node B, eNodeB, or eNB) and a Radio Network Controller (RNC), communicates with wireless devices, known as user equipment (UE). Downlink (DL) transmissions can be communications from a node (e.g., an eNodeB) to a wireless device (e.g., a UE), while uplink (UL) transmissions can be communications from a wireless device to a node.

In a homogeneous network, nodes, also known as macro nodes, can provide basic wireless coverage to wireless devices in a cell. A cell can be an area where wireless devices can operate to communicate with a macro node. Heterogeneous networks (HetNets) can be used to handle the increased traffic load on macro nodes due to the increased usage and functionality of wireless devices. A HetNet can include a layer of planned high-power macro nodes (or macro eNBs) overlaid with multiple layers of lower-power nodes (small eNBs, micro eNBs, pico eNBs, femto eNBs, or home eNBs [HeNBs]), which may be deployed within the coverage area (cell) of the macro nodes in a poorly planned or even completely uncoordinated manner. Lower-power nodes (LPNs) can be generally referred to as "low-power nodes," small nodes, or small cells.

In LTE, data can be sent from the eNodeB to the UE via the Physical Downlink Shared Channel (PDSCH). The Physical Uplink Control Channel (PUCCH) can be used to confirm receipt of data. The downlink and uplink channels or transmissions can use time division duplexing (TDD) or frequency division duplexing (FDD).

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present disclosure will be apparent from the following detailed description taken in conjunction with the accompanying drawings, which together with the accompanying drawings illustrate, by way of example, features of the present disclosure; and wherein:

FIG1 illustrates a group-based Evolved Packet System (EPS) bearer architecture according to an example;

FIG2 illustrates a handover procedure with a group-based Evolved Packet System (EPS) bearer according to an example;

FIG3 illustrates a handover procedure with a group-based Evolved Packet System (EPS) bearer according to an example;

FIG4 depicts functionality of a target evolved Node B (eNB) operable to facilitate handover according to an example;

FIG5 depicts functionality of a target evolved Node B (eNB) operable to facilitate handover according to an example;

6 depicts a flow diagram of a non-transitory machine-readable storage medium having embodied thereon instructions for facilitating handover at a target evolved Node B (eNB) for a user equipment (UE), according to an example; and

FIG7 shows a diagram of a wireless device (eg, UE) according to an example.

Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. However, it will be understood that the scope of the invention is not intended to be limited thereby.

DETAILED DESCRIPTION

Before disclosing and describing the present invention, it should be understood that the present invention is not limited to the specific structures, processing steps or materials disclosed herein, but extends to their equivalents, as will be understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing specific examples only and is not intended to be limiting. The same reference numerals in different figures represent the same elements. The numbers provided in the flow charts and processes are provided for clarity in illustrating the steps and operations and do not necessarily indicate a particular order or sequence.

Example Embodiments

The following provides an initial overview of the technology embodiments, and then further describes specific technology embodiments in detail later. This initial overview is intended to help readers understand the technology more quickly, but is not intended to identify the key features or essential features of the technology, nor is it intended to limit the scope of the claimed subject matter.

A technique for supporting user equipment (UE) mobility management and handover with evolved packet system (EPS) bearer grouping is described. During a handover procedure, a source evolved Node B (eNB) may handover a UE to a target eNB. For example, the source eNB may send a handover request message to the target eNB to handover the UE to the target eNB. The handover request message may include an EPS bearer group identifier (ID) indicating an EPS group bearer associated with the UE. The EPS group bearer may be associated with a group of UEs, including the UE being handed over from the source eNB to the target eNB. The EPS group bearer may include a group-based S1 or S5/S8 bearer. The handover request message may include a last UE indicator indicating whether the UE is the last UE of the source eNB to use the EPS group bearer. The handover request message may include a downlink (DL) traffic indicator indicating whether DL traffic for the EPS group bearer is ignorable or non-ignorable. In one example, the DL traffic may be ignorable or non-ignorable based on the UE's subscription information.

In one configuration, the target eNB may determine that an EPS group bearer associated with the UE has already been established at the target eNB. Therefore, the target eNB may skip the bearer establishment procedure for establishing the EPS group bearer during the handover procedure. In other words, the EPS group bearer does not need to be re-established for the UE at the target eNB because the EPS group bearer has already been established at the target eNB for other UEs in the same EPS bearer group, thereby reducing the amount of signaling during the handover procedure.

In one example, a target eNB may receive a handover request message from a source eNB during a handover procedure, wherein the handover request message includes an EPS bearer group ID, a last UE indicator, and a DL traffic indicator. If the last UE indicator indicates that the UE is not the last UE of the source eNB to use the EPS group bearer (e.g., UE last indicator = 0) and the DL traffic indicator indicates that DL traffic for the EPS group bearer for the UE is negligible during handover (e.g., DL traffic indicator = 0), the handover procedure may not include: sending a path switch request message from the target eNB to a mobility management entity (MME), sending a modify bearer request message from the MME to a serving gateway (SGW), sending a modify bearer response message from the SGW to the MME, and sending a path switch request confirm message from the MME to the target eNB. In addition, the handover procedure may not include: removing the S1 group bearer with the source eNB at the SGW and switching the DL path for the UE's traffic when the UE is not the last UE and the DL traffic is negligible. In one example, when the UE is not the last UE of the EPS bearer group of the source eNB and its DL traffic is negligible, steps 12 to 16 of the handover procedure may be skipped to minimize core network signaling overhead.

In one example, if the last UE indicator indicates that the UE is the last UE of the source eNB to use the EPS group bearer (e.g., UE last indicator = 1) or the DL traffic indicator indicates that the DL traffic of the EPS group bearer for the UE is not negligible during handover (e.g., DL traffic indicator = 1), the handover procedure may include sending a path switch request message from the target eNB to the MME as in a legacy system, sending a modify bearer request message from the MME to the SGW, sending a modify bearer response message from the SGW to the MME, and sending a path switch request confirm message from the MME to the target eNB. In addition, the handover procedure may include removing the S1 group bearer with the source eNB at the SGW and switching the DL path for the UE's traffic when the UE is the last UE or the DL traffic is not negligible. In one example, when the UE is the last UE or the DL traffic is not negligible, steps 12 to 16 of the handover procedure are performed.

Machine Type Communication (MTC) is a technology that allows wireless and wired systems to communicate with other devices without any human intervention. MTC devices may include mobile devices (e.g., user equipment). In addition, MTC devices may include non-mobile devices (e.g., sensors or meters that collect information). MTC devices may communicate with MTC application servers via mobile networks (e.g., wireless, wired, hybrid), and the MTC application servers may use or request data from the MTC devices. The expansion of mobile networks (e.g., broadband wireless access networks, wide area networks) around the world, along with the increase in speed/bandwidth and reduction in power for wireless communications, has contributed to the growth of MTC. Although the amount of data sent by MTC devices is very small, a large number of these devices connected to a wireless network and used concurrently may increase the data load and overhead costs on the network.

An Evolved Packet System (EPS) network is a connection-oriented transport network that establishes connections between various network nodes. These connections may be referred to as EPS bearers. When a user equipment (UE) registers with the core network during an attach procedure, a default EPS bearer may be established. In one example, a default EPS bearer may be established for a UE configured for MTC. The default EPS bearer may provide always-on connectivity for the UE. In addition, the EPS bearer may provide transport services with specific quality of service (QoS) attributes. For example, QoS parameters associated with an EPS bearer may include a channel quality indicator (CQI), allocation and retention priority (ARP), aggregate maximum bit rate (AMBR), and guaranteed bit rate (GBR).

EPS bearers can provide connectivity between a UE (e.g., a UE configured for MTC) and a packet data network (PDN) gateway (PGW). EPS bearers can be generated from a combination of radio access bearers (RABs), S1 bearers, and/or S5/S8 bearers. RABs (e.g., data radio bearers) can provide over-the-air connectivity between a UE and an evolved Node B (eNB). In other words, RABs can carry EPS bearer packets between the UE and the eNB. The UE and the eNB can be part of E-UTRAN. S1 bearers can provide connectivity between the eNB and the SGW. In other words, S1 bearers can carry EPS bearer packets between the eNB and the SGW. S5/S8 bearers can provide connectivity between the SGW and the PGW. In other words, S5/S8 bearers can carry EPS bearer packets between the SGW and the PGW. The SGW and the PGW can be part of the Evolved Packet Core (EPC). The combination of RABs and S1 bearers can generate an E-UTRAN radio access bearer (E-RAB). Thus, the E-RAB can provide connectivity between the UE and the serving gateway (SGW).

In a conventional Long Term Evolution (LTE) system, a default EPS bearer may be established for each UE (e.g., a UE configured for MTC) that is attached to or registered with the wireless network. Therefore, handling a large number of UEs may result in a relatively large signaling overhead in the core network. In addition, a UE configured for MTC may have infrequent service sessions, and each session may last for a very short duration. A UE configured for MTC may move to idle mode after each short session, which may include releasing a portion of the EPS bearer. For example, when a UE configured for MTC moves to idle mode, the UE may release the E-RAB portion of the EPS bearer (i.e., the RAB and S1 portions of the EPS bearer). In addition, when a new short session is started, the E-RAB portion of the EPS bearer may be re-established for the UE. Establishing and releasing the E-RAB for each short session of MTC service increases the signaling overhead.

In one configuration, group EPS bearers can be used to reduce signaling overhead from UEs communicating with the core network. For example, EPS bearers from multiple UEs (e.g., MTC devices) attached to the same eNB can be grouped into a single S1 or S5/S8 bearer. In other words, EPS bearers from UEs can be tunneled within a single S1 or S5/S8 bearer. This configuration can reduce control signaling overhead due to establishing S1 and S5/S8 bearers, and reduce General Packet Radio Service (GPRS) Tunneling Protocol (GTP-u) tunneling overhead by aggregating packets from multiple UEs within a single GTP-u payload.

Figure 1 illustrates an exemplary group-based Evolved Packet System (EPS) bearer architecture. EPS bearers can be divided into Radio Access Bearers (RABs), group-based S1 bearers, and group-based S5/S8 bearers. All EPS bearers belonging to the same group can be transported over a single S1 bearer and/or S5/S8 bearer, even when the EPS bearers in the same group are for different UEs. In one example, an eNB-based EPS bearer grouping policy can define that EPS bearers with the same Access Point Name (APN) and for UEs connected to the same eNB can be grouped over the S1 and S5/S8 reference points.

As shown in Figure 1, radio access bearers can provide connectivity between UEs and eNBs. For example, eNB#1.1 can be connected to UE#1.1.1 via a first radio access bearer and to UE#1.1.2 via a second radio access bearer. With respect to eNB#1.1, the first radio access bearer and the second radio access bearer can be grouped into a first S1 bearer (i.e., a first group-based S1 bearer). Thus, eNB#1.1 can connect to S-GW#1 using the first S1 bearer, where the first S1 bearer includes the first radio access bearer and the second radio access bearer.

Similarly, eNB#1.2 can be connected to UE#1.2.1 via a third radio access bearer and to UE#1.2.2 via a fourth radio access bearer. With respect to eNB#1.2, the third radio access bearer and the fourth radio access bearer can be grouped into a second S1 bearer (i.e., a second group-based S1 bearer). Thus, eNB#1.2 can connect to S-GW#2 using the second S1 bearer, where the second S1 bearer includes the third radio access bearer and the fourth radio access bearer.

Regarding S-GW#1, the first S1 bearer and the second S1 bearer can be grouped into a first S5/S8 bearer (i.e., a first group-based S5/S8 bearer). Therefore, S-GW#1 can connect to the P-GW using the first S5/S8 bearer, where the first S5/S8 bearer includes the first and second S1 bearers, and the first and second S1 bearers include four radio access bearers.

Group-based EPS bearers allow traffic from multiple users (or UEs) to be grouped into a single connection. In other words, a group EPS bearer can be established for a group of users (or UEs), rather than for individual users (or UEs) as in previous solutions. In this technology, radio access bearers can be separate bearers (i.e., specific to each UE), but S1 bearers and S5/S8 bearers can be used for a group of UEs. In previous solutions, each user (or UE) had its own radio access bearer, S1 bearer, and S5/S8 bearer.

In one configuration, the MME can manage EPS bearer grouping based on UE subscription information, APN, and other criteria (e.g., load balancing). For example, the MME can group EPS bearers that meet the same grouping criteria into two groups. In one example, the MME can select the SGW and PGW for a UE based on the UE's subscription information. If group-based EPS bearer operation is enabled, the MME can select the same SGW and PGW for all UEs in the same group.

In one configuration, the MME can initiate group-based bearer establishment and release. The EPS bearer group ID parameter can be added to the bearer context information. The EPS bearer group ID uniquely identifies an EPS bearer group with the same MME. The EPS bearer group ID can be approximately 4 bytes in size. The MME can create and manage the EPS bearer group ID. The eNB, SGW, and/or PGW can then map the EPS bearers corresponding to the EPS bearer group ID to group-based S1 or S5/S8 bearers.

In one configuration, a group-based EPS bearer establishment procedure may be performed. The group-based EPS bearer establishment procedure may involve including bearer context information (e.g., EPS bearer group ID) so that the SGW and PGW can determine how to map between EPS bearers and EPS bearer groups. In one example, the novel context information (e.g., EPS bearer group ID) may be included in a create session request.

Regarding the group-based EPS bearer establishment process, the first step may involve the MME sending a Create Session Request to the SGW. The Create Session Request may include bearer context information (e.g., EPS bearer ID and EPS bearer group ID). The second step may involve the SGW forwarding the Create Session Request including the EPS bearer ID and EPS bearer group ID to the PGW. The third step may involve the PGW sending a Create Session Response to the SGW, where the Create Session Response includes the UE Internet Protocol (IP) address and bearer context information. The fourth step may involve the SGW forwarding the Create Session Response including the UE IP address and bearer context information to the MME. The fifth step may involve the MME sending an S1-MME message (e.g., Initial Context Setup Request) to the eNB, where the S1-MME message includes the EPS bearer group ID. By including the EPS bearer group ID in the S1-MME message (e.g., Initial Context Setup Request), the eNB can understand how to group the corresponding EPS bearers over the S1 reference point.

In one example, group-based S1 and S5/S8 bearers can be established once for the first EPS bearer/UE in the group. For subsequent EPS bearers/UEs in the same group, the S1 bearer establishment step can be skipped, and the S5/S8 bearer establishment step can be simplified by removing the Tunnel Endpoint Identifier (TEID) information. Furthermore, the MME can track how many active UEs are connected for each EPS bearer group. The MME may not initiate the S1 or S5/8 bearer release procedure until the last EPS bearer/UE in the group is disconnected.

Figure 2 illustrates an exemplary handover procedure with group-based Evolved Packet System (EPS) bearers. The handover procedure may be the result of a user equipment (UE) 210 moving from a source evolved Node B (eNB) 220 to a target eNB 230. In other words, UE 210 may initially be near source eNB 220, but then UE 210 may move closer to target eNB 230, thereby triggering the handover procedure. In previous solutions, because the UE has a separate bearer (i.e., a UE-specific bearer), the entire bearer would be moved from the source eNB to the target eNB. However, when a UE uses a group EPS bearer, the group EPS bearer cannot be moved because other UEs still attached to the source eNB may be using the group EPS bearer. Therefore, when group EPS bearers are being used, the traditional handover procedure may be modified.

The handover procedure between source eNB 220 and target eNB 230 may be further described in 3GPP Technical Specification (TS) 36.300 Release 11. In step 1, source eNB 220 may configure a UE measurement procedure based on area restriction information. Source eNB 220 may deliver measurements of functions that assist in controlling the UE's connection mobility to UE 210. In step 2, UE 210 may deliver a measurement report to source eNB 220. In step 3, source eNB 220 may make a handover decision based on the measurement report and radio resource management (RRM) information (i.e., source eNB 220 may decide to handover UE 210 to target eNB 230).

In step 4, source eNB 220 may deliver a handover request message to target eNB 230. The handover request message may include necessary information for preparing handover at the target side (e.g., E-UTRAN Radio Access Bearer (E-RAB) Quality of Service (QoS) information).

In one example, the handover request message may include an Evolved Packet System (EPS) bearer group identifier (ID) indicating an EPS bearer group associated with UE 210. The EPS bearer group ID may identify to which EPS bearer group UE 210 belongs. The EPS group bearer identified using the EPS bearer group ID may be associated with a group of UEs, including UE 210 being handed over from source eNB 220 to target eNB 230. The EPS group bearer may include a group-based S1 or S5/S8 bearer. When the EPS group bearer is established, the EPS group bearer ID may be created. As previously explained, an EPS group bearer may be used for a group of UEs, rather than each EPS bearer being allocated to each UE as in previous solutions.

In one example, the handover request message may include a last UE indicator indicating whether UE 210 is the last UE of source eNB 220 to use the EPS group bearer. In other words, the last UE indicator may indicate that no other UE is currently using the EPS group bearer with respect to source eNB 220. The last UE indicator may be a binary field indicating whether the UE facing handover is the last UE for the corresponding EPS bearer in source eNB 220. In one example, the last UE indicator may be "0" when UE 210 is not the last UE of source eNB 220 to use the EPS bearer, and may be "1" when UE 210 is the last UE of source eNB 220 to use the EPS bearer.

In conventional solutions, because there is one EPS bearer per UE, when a UE moves from source eNB 220 to target eNB 230, the S1 EPS bearer for that UE, which provides connectivity between source eNB 220 and SGW 250, must be removed. However, when multiple UEs use a group-based S1 bearer, if UE 210 moves from source eNB 220 to target eNB 230 but UE 210 is not the last UE using the group-based S1 bearer, the group-based S1 bearer can be maintained to still provide connectivity between source eNB 220 and SGW 250 for other UEs. The group-based S1 bearer can be maintained until UE 210 is the last UE with respect to source eNB 220. When the last UE moves from source eNB 220 to target eNB 230 (i.e., there are no more UEs using the EPS group bearer with respect to source eNB 220), the group-based S1 bearer can be removed only then.

In one example, the handover request message may include a DL traffic indicator indicating downlink (DL) traffic for the EPS group bearer. The DL traffic indicator is a binary field that may indicate whether the EPS group bearer has minimal or no downlink traffic. Typically, most machine type communications generate uplink traffic (e.g., meter collection information) rather than downlink traffic. Therefore, in some cases, DL traffic may be negligible during handover. In one example, when the DL traffic indicator indicating the DL traffic for the EPS group bearer for the UE during handover is less than a defined threshold (e.g., the DL traffic is negligible during handover), the DL traffic indicator may be represented as "0", and when the DL traffic indicator indicates that the DL traffic for the EPS group bearer for the UE during handover is greater than a defined threshold (e.g., the DL traffic is not negligible during handover), the DL traffic indicator may be represented as "1".

In one example, the EPS bearer group ID, last UE indicator, and DL traffic indicator can be included in the novel EPS bearer context information for each EPS bearer or extended radio access bearer (eRAB) in a handover message. The EPS bearer group ID and DL traffic indicator can be configured by the mobility management entity (MME) 210 during the bearer establishment process and included as part of the UE's bearer context information. In addition, the last UE indicator can be determined by the source eNB 220 and included as part of the UE's bearer context information.

Returning to Figure 2, in step 5, if the target eNB 230 can approve the resources, the target eNB 230 can perform admission control based on the received E-RAB QoS information to increase the probability of a successful handover. The E-RAB can uniquely identify the concatenation of the S1 bearer and the corresponding data radio bearer. The target eNB 230 can configure the required resources based on the received E-RAB QoS information and reserve a cell radio network temporary identifier (C-RNTI) and optionally a random access channel (RACH) preamble.

In step 6, target eNB 230 may prepare for handover with the physical layer (i.e., Layer 1 or L1) and the data link layer (i.e., Layer 2 or L2). Target eNB 230 may pass a Handover Request Confirm message to source eNB 220. The Handover Request Confirm message may include a transparent container to be sent to UE 210 as an RRC message for performing the handover. The container may include a new C-RNTI, a target eNB security algorithm identifier, a dedicated RACH preamble, and other parameters (e.g., a system information block). Once source eNB 220 receives the Handover Request Confirm message from target eNB 230, or upon initiating transmission of a Handover Command in the downlink, data forwarding may be initiated.

In step 7, target eNB 230 may generate an RRC message for performing handover, and the RRC message may be delivered to source eNB 220. Source eNB 220 may deliver the RRC message to UE 210. Specifically, the RRC message may be an RRC Connection Reconfiguration message including mobility control information. Source eNB 220 may perform necessary integrity protection and encryption for the RRC message. UE 210 may receive the RRC Connection Reconfiguration message with necessary parameters (e.g., a new C-RNTI, a target eNB security algorithm identifier, and optionally, a dedicated RACH preamble). Source eNB 220 may instruct UE 210 to perform handover. In other words, UE 210 may be instructed to detach from source eNB 220 and synchronize to target eNB 230 (i.e., the new source eNB).

In step 8, the source eNB 220 may pass a sequence number (SN) status transfer message to the target eNB 230. The SN status transfer message may convey the uplink PDCP SN receiver status and downlink PDCP SN transmitter status of the E-RAB to which the Packet Data Convergence Protocol (PDCP) state preservation applies (i.e., for Radio Link Control Acknowledged Mode or RLC AM).

In step 9, after receiving the RRC connection reconfiguration message including the mobility control information, UE 210 may synchronize with target eNB 230 and then access the target cell via a random access channel (RACH). If a dedicated RACH preamble is indicated in the mobility control information, UE 210 may access the target cell using a contention-free procedure. Alternatively, if a dedicated preamble is not indicated in the mobility control information, UE 210 may access the target cell using a contention-based procedure.

In step 10, target eNB 230 may respond to UE 210 with an uplink (UL) allocation and timing advance. In step 11, when UE 210 has successfully accessed the target cell, UE 210 may transmit an RRC Connection Reconfiguration Complete message (including the C-RNTI) to target eNB 230 to confirm the handover. The RRC Connection Reconfiguration Complete message may include an uplink buffer status report indicating that the handover procedure is complete for UE 210. Target eNB 230 may verify the C-RNTI included in the RRC Connection Reconfiguration Complete message. After step 11 occurs, target eNB 230 may begin transmitting user data to UE 210.

In one configuration, when UE 210 is the last UE in the EPS bearer group with source eNB 220 (i.e., last UE indicator = 1) or the DL traffic is non-negligible (i.e., DL traffic indicator = 1), the handover procedure may include steps 12 to 16. DL traffic may be non-negligible when the level of DL traffic is greater than a defined threshold. Since UE 210 is the last UE, steps 12 to 16 are performed to notify SGW 250 that the corresponding group-based S1 bearer with source eNB 220 should be torn down. Furthermore, steps 12 to 16 are performed to notify SGW 250 that the DL path for the UE's traffic should be switched because the DL traffic is non-negligible.

In step 12, target eNB 230 may send a path switch request message to MME 240 to notify UE 240 that UE 210 has changed cells. The path switch request message may be for each EPS group bearer (or E-RAB) with source eNB 220. The path switch request message may include an EPS bearer group ID and a last UE indicator.

In step 13, MME 240 may send a Modify Bearer Request message to SGW 250. The Modify Bearer Request message may be for each EPS group bearer (or E-RAB) with source eNB 220. The Modify Bearer Request message may include the EPS bearer group ID and the last UE indicator.

In step 14, SGW 250 may switch the downlink data path to the target side. SGW 250 may send one or more "end marker" packets to source eNB 220 over the old path and may then release U-plane and/or transport network layer (TNL) resources toward source eNB 220. In step 14, since UE 210 is the last UE in the EPS bearer group with source eNB 220, SGW 250 may remove the S1 group bearer with source eNB 220. In other words, since UE 210 is the last UE in the EPS bearer group, there is no need to further maintain the EPS bearer group at source eNB 220. Furthermore, since the DL traffic is non-negligible, SGW 250 may switch the downlink data path for the UE's traffic, and thus, UE 210 will continue to receive downlink traffic after switching to target eNB 230.

In step 15, SGW 250 may send a Modify Bearer Response message to MME 240. In step 16, MME 240 may confirm the Path Switch Request message with a Path Switch Request Acknowledge message, which is delivered from MME 240 to target eNB 230. In step 17, target eNB 230 may send a UE Context Release message to source eNB 220. By sending the UE Context Release message, target eNB 230 may notify source eNB 220 of the successful handover and trigger the release of resources by source eNB 220. After receiving the Path Switch Request Acknowledge message from MME 240, target eNB 230 may send a UE Context Release message. In step 18, upon receiving the UE Context Release message, source eNB 220 may release radio and C-plane related resources associated with the UE context.

In one configuration, when UE 210 is about to be handed over from source eNB 220 to target eNB 230, target eNB 230 may determine whether an EPS group bearer associated with UE 210 has already been established at target eNB 230. In other words, target eNB 230 may determine whether another UE is already using the same EPS group bearer. If an EPS group bearer has already been established at target eNB 230, re-establishing the EPS group bearer is unnecessary, thereby saving signaling resources. If an EPS group bearer is not currently established at target eNB 230 (i.e., UE 210 is the first UE to use the EPS group bearer with respect to target eNB 230), target eNB 230 may establish the EPS group bearer. However, target eNB 230 does not need to re-establish the EPS group bearer for subsequent UEs being handed over to target eNB 230, where the subsequent UEs are associated with the same EPS bearer group ID as UE 210.

FIG3 illustrates an exemplary handover procedure with group-based Evolved Packet System (EPS) bearers. The handover procedure may be the result of user equipment (UE) 310 moving from a source evolved Node B (eNB) 320 to a target eNB 330. In other words, UE 310 may initially be near source eNB 320, but then may move closer to target eNB 330, thereby triggering the handover procedure. When group EPS bearers are being used, conventional handover procedures may be modified.

The handover process between source eNB 320 and target eNB 330 may be further described in 3GPP Technical Specification (TS) 36.300 Release 11. In step 1, source eNB 320 may communicate measurements of functions that assist in controlling the UE's connection mobility to UE 310. In step 2, UE 310 may communicate a measurement report to source eNB 320. In step 3, source eNB 320 may make a handover decision based on the measurement report and radio resource management (RRM) information (i.e., source eNB 320 may decide to handover UE 310 to target eNB 330).

In step 4, the source eNB 320 may deliver a handover request message to the target eNB 330. The handover request message may include an evolved packet system (EPS) bearer group identifier (ID), a last UE indicator, and a downlink (DL) traffic indicator, as previously described.

In step 5, target eNB 330 may perform admission control. In step 6, target eNB 330 may deliver a handover request confirm message to source eNB 320. In step 7, target eNB 330 may generate a radio resource control (RRC) message for performing handover, and the RRC message may be delivered to source eNB 320. Source eNB 320 may deliver the RRC message (e.g., an RRC connection reconfiguration message) to UE 310. After receiving the RRC connection reconfiguration message, source eNB 320 may instruct UE 310 to perform handover. In other words, UE 310 may be instructing to detach from source eNB 320 and synchronize to target eNB 330 (i.e., the new source eNB).

In step 8, source eNB 320 may deliver a Sequence Number (SN) Status Transfer message to target eNB 330. In step 9, UE 310 may synchronize with target eNB 330. In step 10, target eNB 330 may respond to UE 310 with an uplink (UL) assignment and timing advance. In step 11, UE 310 may deliver an RRC Connection Reconfiguration Complete message to target eNB 330 to confirm the handover. After step 11 occurs, target eNB 330 may begin delivering user data to UE 310.

In one configuration, when UE 310 is not the last UE in the EPS bearer group with source eNB 320 (i.e., last UE indicator = 0) and DL traffic is negligible (i.e., DL traffic indicator = 0), the handover procedure can skip steps 12 through 16. DL traffic can be negligible when the level of DL traffic is less than a defined threshold. Since UE 210 is not the last UE, steps 12 through 16 can be skipped because SGW 350 does not need to tear down the corresponding group-based S1 bearer with source eNB 320. In other words, the group-based S1 bearer or EPS group bearer is not torn down because it is in use by other UEs with respect to source eNB 320. The handover procedure can include notifying target eNB 330 of SGW 350's S1-U tunnel parameters, but if an S1 bearer has already been established for the same EPS group bearer at target eNB 330, target eNB 330 should already have the S1-U tunnel parameters. An example of a tunnel parameter for S1-U is a General Packet Radio Service (GPRS) Tunneling Protocol (GTP) Tunnel Endpoint Identifier (TEID). Therefore, steps 12 to 16 of the conventional handover procedure can be skipped. Furthermore, since the DL traffic is negligible, SGW 350 does not switch the DL path for the UE's traffic, so steps 12 to 16 can be skipped. Instead, the first uplink packet arriving from target eNB 330 can implicitly trigger step 14 for switching the DL path. In other words, after receiving the first uplink packet, SGW 350 can switch the DL path for the UE's traffic from source eNB 320 to target eNB 330.

Since the handover procedure can skip steps 12 to 16 when UE 310 is not the last UE in the EPS bearer group with source eNB 320 (i.e., last UE indicator = 0) and DL traffic is negligible (i.e., DL traffic indicator = 0), the handover procedure continues with step 17. In step 17, target eNB 330 may send a UE context release message to source eNB 320. In step 18, upon receiving the UE context release message, source eNB 320 may release radio and C-plane related resources associated with the UE context.

Another example provides functionality 400 of a target evolved Node B (eNB) operable to facilitate handover, as shown in the flowchart of FIG4 . The functionality can be implemented as a method, or the functionality can be executed as instructions on a machine, wherein the instructions are embodied on at least one computer-readable medium or a non-transitory machine-readable storage medium. The target eNB can include one or more processors configured to: receive, at the target eNB, a handover request message from a source eNB for handing over a user equipment (UE) from the source eNB to the target eNB, the handover request message including: an evolved packet system (EPS) bearer group identifier (ID) indicating an EPS group bearer of the source eNB and associated with the UE; a last UE indicator indicating whether the UE is the last UE of the source eNB to use the EPS group bearer; and a downlink (DL) traffic indicator indicating whether DL traffic for the UE is ignorable during handover, as in block 410 . The target eNB may include one or more processors configured to perform a handover procedure to establish a connection with the UE based on at least one of the EPS bearer group ID, the last UE indicator, or the DL traffic indicator included in the handover request message, as in block 420 .

In one example, the one or more processors may be further configured to: determine that a last UE indicator indicates that the UE is the last UE of the source eNB to use the EPS group bearer; determine that a DL traffic indicator indicates that DL traffic for the UE is not negligible during handover; and perform a handover procedure at the target eNB to establish a connection with the UE, wherein when the UE is the last UE and the DL traffic is not negligible, the handover procedure includes: removing the EPS group bearer with the source eNB and switching the DL path for the UE traffic. In another example, the handover procedure includes: sending a path switch request message from the target eNB to a mobility management entity (MME) when at least one of the following occurs: the UE is the last UE, or the DL traffic is not negligible.

In one example, the one or more processors are further configured to: determine that the last UE indicator indicates that the UE is not the last UE of the source eNB to use the EPS group bearer; determine that the DL traffic indicator indicates that DL traffic for the UE is negligible during handover; and perform a handover procedure at the target eNB to establish a connection with the UE, wherein, when the UE is not the last UE and the DL traffic is negligible, the handover procedure does not include: removing the EPS group bearer with the source eNB and switching the DL path for the UE traffic.

In one example, the one or more processors are further configured to: determine that an EPS group bearer associated with the UE is not currently established at the target eNB; and perform a bearer establishment procedure to establish the EPS group bearer at the target eNB. In another example, the EPS group bearer is an S1 group bearer or an S5/S8 group bearer. In yet another example, the EPS group bearer is shared by multiple UEs.

In one example, one or more processors are configured to facilitate handover of a UE configured to perform machine type communication. In another example, an EPS bearer group ID and a DL traffic indicator included in a handover request message are configured at a mobility management entity (MME). In yet another example, a last UE indicator included in the handover request message is determined at a source eNB.

Another example provides functionality 500 of a target evolved Node B (eNB) operable to facilitate handover, as shown in the flowchart of FIG5 . The functionality may be implemented as a method, or the functionality may be executed as instructions on a machine, wherein the instructions are embodied on at least one computer-readable medium or a non-transitory machine-readable storage medium. The target eNB may include: one or more processors configured to: receive, at the target eNB, a handover request message from a source eNB for handing over a user equipment (UE) from the source eNB to the target eNB, the handover request message including: an evolved packet system (EPS) bearer group identifier (ID) indicating an EPS group bearer of the source eNB and associated with the UE; a last UE indicator indicating that the UE is not the last UE of the source eNB to use the EPS group bearer; and a downlink (DL) traffic indicator indicating that DL traffic for the UE is ignorable during handover, as in block 510 . The target eNB may include one or more processors configured to: perform a handover procedure to establish a connection with the UE, wherein when the UE is not the last UE and the DL traffic is negligible, the handover procedure does not include: removing the EPS group bearer with the source eNB or switching the DL path for the UE traffic, as in box 520.

In one example, the one or more processors are further configured to: determine that an EPS group bearer associated with the UE is not currently established at the target eNB; and perform a bearer establishment procedure to establish the EPS group bearer at the target eNB. In another example, the EPS group bearer is an S1 group bearer or an S5/S8 group bearer. In yet another example, the EPS group bearer is shared by multiple UEs.

In one example, one or more processors are configured to facilitate handover of a UE configured to perform machine type communication. In another example, an EPS bearer group ID and a DL traffic indicator included in a handover request message are configured at a mobility management entity (MME). In yet another example, a last UE indicator included in the handover request message is determined at a source eNB.

Another example provides at least one non-transitory machine-readable storage medium having stored thereon instructions 600 for facilitating handover at a target evolved Node B (eNB) for a user equipment (UE), as shown in the flowchart of FIG6 . The instructions, when executed, perform the following operations: using at least one processor of the target eNB, receiving a handover request message from a source eNB for handing over the UE from the source eNB to the target eNB, as in block 610. The handover request message may include: an evolved packet system (EPS) bearer group identifier (ID) indicating an EPS group bearer of the source eNB and associated with the UE; a last UE indicator indicating that the UE is the last UE of the source eNB to use the EPS group bearer; or a downlink (DL) traffic indicator indicating that DL traffic for the UE is non-negligible during handover. The instructions, when executed, perform the following operations: using at least one processor of the target eNB, perform a handover procedure to establish a connection between the target eNB and the UE, wherein the handover procedure includes: when the UE is the last UE, removing the EPS group bearer with the source eNB, and if the DL traffic is non-negligible, switching the DL path for the UE traffic, as in box 620.

In one example, the at least one non-transitory machine-readable storage medium may further include instructions that, when executed by at least one processor of the target eNB, perform the following operations: send a path switch request message from the target eNB to a mobility management entity (MME), the path switch request message including the EPS bearer group ID and the last UE indicator. In another example, the at least one non-transitory machine-readable storage medium may further include instructions that, when executed by at least one processor of the target eNB, perform the following operations: send a path switch request message including the EPS bearer group ID and the last UE indicator from the target eNB to a mobility management entity (MME), wherein the MME is configured to send a modify bearer request message including the EPS bearer group ID and the last UE indicator to a serving gateway (SGW). In yet another example, removing the EPS group bearer with the source eNB and switching the DL path for the UE traffic are performed at the serving gateway (SGW).

FIG7 provides an example illustration of a wireless device (e.g., a user equipment (UE), a mobile station (MS), a mobile wireless device, a mobile communication device, a tablet, a mobile phone, or other type of wireless device). The wireless device may include one or more antennas and may be configured to communicate with a node, macro node, low power node (LPN) or transmission station (e.g., a base station (BS)), an evolved Node B (eNB), a baseband unit (BBU), a remote radio head (RRH), remote radio equipment (RRE), a relay station (RS), radio equipment (RE), or other type of wireless wide area network (WWAN) access point. The wireless device may be configured to communicate using at least one wireless communication standard including 3GPP LTE, WiMAX, high speed packet access (HSPA), Bluetooth, and WiFi. The wireless device may communicate using a separate antenna for each wireless communication standard or a shared antenna for multiple wireless communication standards. The wireless device may communicate within a wireless local area network (WLAN), a wireless personal area network (WPAN), and/or a WWAN.

FIG7 also provides an illustration of a microphone and one or more speakers that can be used for audio input and output from the wireless device. The display screen can be a liquid crystal display (LCD) screen or other type of display screen (e.g., an organic light emitting diode (OLED) display). The display screen can be configured as a touch screen. The touch screen can use capacitive, resistive, or another type of touch screen technology. The application processor and graphics processor can be coupled to the internal memory to provide processing and display capabilities. A non-volatile memory port can also be used to provide data input/output options to the user. The non-volatile memory port can also be used to expand the memory capacity of the wireless device. A keyboard can be integrated with the wireless device or wirelessly connected to the wireless device to provide additional user input. A touch screen can also be used to provide a virtual keyboard.

The various techniques, or aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in a tangible medium (e.g., a floppy disk, CD-ROM, hard drive, non-transitory computer-readable storage medium, or any other machine-readable storage medium), wherein when the program code is loaded into and executed by a machine (e.g., a computer), the machine becomes an apparatus for implementing the various techniques. Circuitry may include hardware, firmware, program code, executable code, computer instructions, and/or software. Non-transitory computer-readable storage medium may be a computer-readable storage medium that does not include signals. In the case of program code execution on a programmable computer, the computing device may include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. The volatile and non-volatile memory and/or storage elements may be RAM, EPROM, a flash drive, an optical drive, a magnetic hard drive, a solid-state drive, or other media for storing electronic data. Nodes and wireless devices may also include a transceiver module, a counter module, a processing module, and/or a clock module or a timer module. One or more programs that can implement or utilize the various techniques described herein can use application programming interfaces (APIs), reusable controls, and the like. These programs can be implemented in high-level procedural programming languages or object-oriented programming languages to communicate with a computer system. However, if desired, the programs can be implemented in assembly language or machine language. In any case, the language can be a compiled language or an interpreted language and combined with a hardware implementation.

As used herein, the term processor may include general purpose processors, special purpose processors (eg, VLSI, FPGA, or other types of special purpose processors), and baseband processors used in a transceiver to transmit, receive, and process wireless communications.

It should be understood that many of the functional units described in this specification have been labeled as modules in order to more particularly emphasize their implementation independence. For example, a module can be implemented as a hardware circuit, including custom VLSI circuits or gate arrays, off-the-shelf semiconductors (e.g., logic chips), transistors, or other discrete components. A module can also be implemented using programmable hardware devices (e.g., field programmable gate arrays, programmable array logic, programmable logic devices, etc.).

In one example, multiple hardware circuits or multiple processors can be used to implement the functional units described in this specification. For example, a first hardware circuit or a first processor can be used to perform processing operations, and a second hardware circuit or a second processor (e.g., a transceiver or a baseband processor) can be used to communicate with other entities. The first hardware circuit and the second hardware circuit can be integrated into a single hardware circuit, or alternatively, the first hardware circuit and the second hardware circuit can be separate hardware circuits.

Modules may also be implemented in software so as to be executed by various types of processors. An identified module of executable code may, for example, comprise one or more physical or logical blocks of computer instructions, which may be organized, for example, as objects, procedures, or functions. However, the executable files of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when logically combined together, constitute the module and achieve the module's stated purpose.

In fact, the module of executable code can be a single instruction or many instructions, and can even be distributed on several different code segments, among different programs, and throughout several memory devices. Similarly, operational data can be identified and shown in the module at this, and can be embodied and organized in the data structure of any suitable type in any suitable form. Operational data can be collected as a single data set, or can be distributed on different locations, included on different storage devices, and can exist at least in part only as an electronic signal on a system or network. A module can be passive or active, including an agent that can be operated to perform a desired function.

References throughout the specification to "an example" mean that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in an example" in various places throughout the specification are not necessarily all referring to the same embodiment.

As used herein, for convenience, multiple items, structural elements, constituent elements and/or materials can be proposed in a common list. However, these lists should be understood as if each member of the list is identified as a separate and unique member. Therefore, in the absence of contrary instructions, each member of the list should not be understood as being in fact equivalent to any other member in the same list based solely on their presence in the common group. In addition, various embodiments and examples of the present invention may be mentioned herein, together with the alternatives of their various components. It should be understood that these embodiments, examples and alternatives are not understood as being in fact equivalent to each other, but are regarded as separate and autonomous representations of the present invention.

In addition, the described features, structures or characteristics can be combined in one or more embodiments in any suitable manner. In the following description, a large number of specific details, such as examples of layouts, distances, network examples, etc., are provided to provide a thorough understanding of embodiments of the present invention. However, it should be understood by those skilled in the art that the present invention can be implemented without one or more of the specific details, or with other methods, components, layouts, etc. In other examples, well-known structures, materials or operations are not shown or described in detail to avoid obscuring various aspects of the present invention.

Although the foregoing embodiments illustrate the principles of the present invention in one or more specific applications, it will be apparent to those skilled in the art that numerous modifications in form, use, and details of the implementations may be made without inventive effort and without departing from the principles and concepts of the present invention. Therefore, it is not intended to limit the present invention except as set forth in the claims below.

Claims (19)

1. A target evolved Node B (eNB) operable to facilitate handover, the target eNB comprising one or more processors configured to: At the target eNB, a handover request message is received from the source eNB for handing over a user equipment (UE) from the source eNB to the target eNB. The handover request message includes: An evolved packet system (EPS) bearer group identifier (ID) indicates the EPS group bearer of the source eNB and is associated with the UE, wherein the EPS group bearer is an S1 group bearer or an S5/S8 group bearer. Last UE indicator, used to indicate whether the UE is the last UE of the source eNB to be carried by the EPS group; and Downlink (DL) service indicator, used to indicate whether DL services for the UE during handover are negligible; and A handover procedure is performed at the target eNB to establish a connection with the UE based on at least one of the EPS bearer group ID, the last UE indicator, or the DL service indicator included in the handover request message. 2. The target eNB as claimed in claim 1, wherein the one or more processors are further configured to: The determination of the last UE indicator indicates that the UE is the last UE of the source eNB to be carried by the EPS group; The determination of the DL service indicator indicates that the DL service used by the UE during handover is non-negligible; and The handover procedure is performed at the target eNB to establish a connection with the UE. When the UE is the last UE and the DL service is non-negligible, the handover procedure includes: removing the EPS group bearer with the source eNB and switching the DL path used for the UE service. 3. The target eNB as described in claim 2, wherein the handover process includes: A route switching request message is sent from the target eNB to the Mobility Management Entity (MME) when at least one of the following conditions occurs: The UE mentioned is the last UE, or The aforementioned DL service is indispensable. 4. The target eNB as claimed in claim 1, wherein the one or more processors are further configured to: The last UE indicator indicates that the UE is not the last UE of the source eNB to be carried by the EPS group; The DL service indicator is determined to indicate that DL services used by the UE during handover are negligible; and The handover procedure is performed at the target eNB to establish a connection with the UE. When the UE is not the last UE and the DL service is negligible, the handover procedure does not include: removing the EPS group bearer with the source eNB and switching the DL path used for the UE service. 5. The target eNB as claimed in claim 1, wherein the one or more processors are further configured to: It was determined that no EPS group bearer associated with the UE has been established at the target eNB; and Perform a bearer establishment process to establish an EPS group bearer at the target eNB. 6. The target eNB as claimed in claim 1, wherein the EPS group bearer is shared by multiple UEs. 7. The target eNB as claimed in claim 1, wherein the one or more processors are configured to facilitate handover of a UE configured to perform machine-type communication. 8. The target eNB as claimed in claim 1, wherein the EPS bearer group ID and the DL service indicator included in the handover request message are configured at the Mobility Management Entity (MME). 9. The target eNB as claimed in claim 1, wherein the last UE indicator included in the handover request message is determined at the source eNB. 10. A target evolved Node B (eNB) operable to facilitate handover, the target eNB comprising one or more processors configured to: At the target eNB, a handover request message is received from the source eNB for handing over a user equipment (UE) from the source eNB to the target eNB. The handover request message includes: An evolved packet system (EPS) bearer group identifier (ID) indicates the EPS group bearer of the source eNB and is associated with the UE, wherein the EPS group bearer is an S1 group bearer or an S5/S8 group bearer. Last UE indicator, which indicates that the UE is not the last UE of the source eNB to be carried by the EPS group; and Downlink (DL) service indicator, which indicates that DL services used for the UE during handover are negligible; and A handover procedure is performed at the target eNB to establish a connection with the UE. When the UE is not the last UE and the DL service is negligible, the handover procedure does not include: removing the EPS group bearer with the source eNB, or switching the DL path used for the UE service. 11. The target eNB of claim 10, wherein the one or more processors are further configured to: It was determined that no EPS group bearer associated with the UE has been established at the target eNB; and Perform a bearer establishment process to establish an EPS group bearer at the target eNB. 12. The target eNB as claimed in claim 10, wherein the EPS group bearer is shared by multiple UEs. 13. The target eNB of claim 10, wherein the one or more processors are configured to facilitate handover of a UE configured to perform machine-type communication. 14. The target eNB as claimed in claim 10, wherein the EPS bearer group ID and the DL service indicator included in the handover request message are configured at the Mobility Management Entity (MME). 15. The target eNB as claimed in claim 10, wherein the last UE indicator included in the handover request message is determined at the source eNB. 16. At least one non-transitory machine-readable storage medium storing instructions for facilitating handover for a user equipment (UE) at a target evolved Node B (eNB), the instructions performing the following operations when executed: Using at least one processor of the target eNB, a handover request message is received from the source eNB for handing the UE from the source eNB to the target eNB, the handover request message including: An evolved packet system (EPS) bearer group identifier (ID) indicates the EPS group bearer of the source eNB and is associated with the UE, wherein the EPS group bearer is an S1 group bearer or an S5/S8 group bearer. Last UE indicator, which indicates that the UE is the last UE of the source eNB to be carried by the EPS group; or Downlink (DL) service indicator, which indicates that DL services used for the UE during handover are non-negligible; and Using at least one processor of the target eNB, a handover procedure is performed to establish a connection between the target eNB and the UE, wherein the handover procedure includes: removing the EPS group bearer with the source eNB when the UE is the last UE, and switching the DL path used for the UE service if the DL service is non-negligible. 17. The at least one non-transitory machine-readable storage medium of claim 16, further comprising instructions that, when executed by the at least one processor of the target eNB, perform the following operations: A path switching request message is sent from the target eNB to the Mobility Management Entity (MME), the path switching request message including the EPS bearer group ID and the last UE indicator. 18. The at least one non-transitory machine-readable storage medium of claim 16, further comprising instructions that, when executed by the at least one processor of the target eNB, perform the following operations: A path handover request message including the EPS bearer group ID and the last UE indicator is sent from the target eNB to the Mobility Management Entity (MME), wherein the MME is configured to send a modify bearer request message including the EPS bearer group ID and the last UE indicator to the Serving Gateway (SGW). 19. The at least one non-transitory machine-readable storage medium as claimed in claim 16, wherein the removal of the EPS group bearer with the source eNB and the switching of the DL path for UE services are performed at the serving gateway (SGW).