The foregoing and other aspects of embodiments of this invention are made more evident in the following Detailed Description, when read in conjunction with the attached Drawing Figures, wherein:
The exemplary embodiments of this invention address the foregoing and other problems, and provide support for a seamless and lossless HO in E-UTRAN that enhances the robustness of the HO against at least the situation discussed above, that is, the failure of the UE to correctly receive the HANDOVER COMMAND in Step 4 of
Reference is made first to
The UE 10 includes a data processor (DP) 10A, a memory (MEM) 10B that stores a program (PROG) 10C, and a suitable radio frequency (RF) transceiver 10D for bidirectional wireless communications with the eNode B 12, which also includes a DP 12A, a MEM 12B that stores a PROG 12C, and a suitable RF transceiver 12D. The eNode B 12 is coupled via the data path 13 to the aGW 14 (containing the MME/UPE functionality) that also includes at least one DP 14A and a MEM 14B storing an associated PROG 14C. At least one of the PROGs 10C, 12C and 14C is assumed to include program instructions that, when executed by the associated DP, enable the electronic device to operate in accordance with the exemplary embodiments of this invention, as will be discussed below in greater detail.
Also shown in
Each eNode B 12, 12′ may be assumed to include a HO control function or unit 12E. Each eNode B 12, 12′ may be further assumed to include a Timer unit 12F, referred to below as Timer_T1, that operates in conjunction with the HO unit 12E. The UE 10 may be assumed to include a HO control function or unit 10E and an associated Timer 10F also referred to below as Timer_T2. The HO units 10E, 12E and Timer units 10F, 12F are constructed and operated in accordance with the exemplary embodiments of this invention, as described in greater detail below. Each eNode B 12, 12′ may also be assumed to include a RRC function 12G, the operation of which in certain exemplary embodiments of this invention is discussed below. A corresponding RRC function 10G is shown in the UE 10.
It should be noted that while the HO and timer units 10E, 12E, 10F, 12F are shown as separate elements in
In general, the various embodiments of the UE 10 can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.
The exemplary embodiments of this invention may be implemented by computer software executable by the DP 10A of the UE 10, the DP 12A of the eNode Bs 12 and 12′, the DP 14A of the aGW 14, or by hardware, or by a combination of software and hardware.
The MEMs 10B, 12B and 14B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The DPs 10A, 12A and 14A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.
Describing now the exemplary embodiments of this invention in even further detail, and referring to
As can be appreciated, if either Timer_T1 and Timer_T2 times out, i.e., reaches the maximum allowed time value measured in, for example, milliseconds or seconds, then it can be assumed that an error has occurred during the HO signaling message flow, and corrective action can be taken.
For example, in the event that Timer_T112F expires and the eNB 12 does not receive an expected message, and for the case where Timer_T112F is applied in the target eNB 12′ as shown in
Further by example, and in the event that Timer_T112F expires and the eNB 12 does not receive an expected message, and for the case where Timer_T1 is used in the source eNB 12, the source eNB 12 begins paging the ACTIVE state UE in the current cell as in message 4b in
In the event that Timer_T210F expires, and the UE 10 does not receive the expected message(s) from the network, such as from the source eNB 12 in the current cell, the UE 10 begins listening to the paging channel of the current cell and, if possible, to the paging channel(s) of those neighboring cell(s) that the UE was able to measure and report at Step 1 in
It can be noted that in current LTE E-UTRAN system concepts the paging of an IDLE state UE 10 is originated from the aGW 14, and the PAGING message is formed and sent by the RRC unit 12G of the eNB 12. However, in accordance with the exemplary embodiments of this invention the eNB RRC unit 12G is permitted to initiate paging of an ACTIVE state UE 10 for control purposes. The source eNB 12 may use the currently valid, also referred to as the old C-RNTI as the UE ID for paging. In the case where the target eNB 12′ is also allowed to page the UE 10, as shown in message 4c of
However, if the radio connection is actually lost, and the RRC is not allowed to initiate paging of the ACTIVE state UE 10, it is within the scope of the exemplary embodiments of this invention for the source or target eNB 12, 12′ to notify the aGW 14 upon the expiry of Timer_T1 so that urgent paging can be initiated from the aGW 14, and Timer_T2 may be generalized and extended so as to force the UE 10 back to the IDLE state, as from the ACTIVE state, to listen for possible urgent paging initiated by the aGW 14.
It can be noted that in this case the eNB 12 may send the HO command and related information to the aGW 14 to be included in the IDLE state page, or the eNB 12 RRC functionality 12G may know that the IDLE state page initiated by the aGW 14 should include this information. In either case it is most desirable that the aGW 14 request only a subset of the eNBs located in a paging area to page the UE 10, such as only the source eNB 12 and the target eNB 12′. As such, the paging notification sent from the aGW 14 preferably includes at least the identifications of the involved source and target eNBs 12, 12′.
Optional messages 4d and 4e in
For the case where the UE 10 transitions back to the IDLE state to receive the page, it is not implied that the current call is dropped. For example, a temporary state transition to IDLE may be performed for call recovery purposes so as to receive the necessary HO information. During this period the ACTIVE context of the UE 10 may remain in effect, at least for some predetermined maximum amount of time such as one set by an associated RRC 10G timer.
Note further in this regard that the UE 10 needs to contact the target eNB 12′ to establish the radio connection and become RRC_ACTIVE, and during this time the target eNB 12 may communicate with the MME/UPE 14 to resume the LTE_ACTIVE state.
It can be further noted that in certain previous systems a central node, such as the RNC in UTRAN and a BSC in GSM, was responsible for HO, and timers have been defined to cope with HO failure, for example the timers T3103 and T3124 in GSM. However, the HO execution in the E-UTRAN system that is of particular interest to the exemplary embodiments of this invention does not involve a central node, and instead it is handled locally by the eNBs 12, 12′. Thus, an aspect of the exemplary embodiments of this invention is in providing distributed HO-related timers (Timer_1, Timer_2) at those nodes, like the eNBs 12 and UE 10, where the HO-related signaling and control resides.
Clearly, the use of the exemplary embodiments of this invention provides a simple and effective technique to enhance the robustness of the intra E-UTRAN handover.
Referring to
During operation of Step 4B, and if the communication is initiated by the target eNB 12′, the target eNB sends a notification to the source eNB 12, and the source eNB 12 sends the communication in a Paging channel of the serving cell. The target eNB 12′ may also send the communication in a Paging channel of the target cell. During operation Step 4B, the UE 10 may be in the ACTIVE state.
Referring to
It should be further appreciated that the exemplary embodiments of this invention, in a further aspect thereof, provide an eNB-resident computer program product that functions to perform HO of the UE 10 by: initiating operation of a timer in at least one of the target eNB 12′ and source eNB 12 after initiation of the HO procedure and, in the event the timer expires before the UE 10 can be expected to respond to a HO-related message sent from the source eNB 12, initiating a communication to the UE 10 on a Paging channel from at least one of the target eNB 12′ and source eNB 12, where the communication includes information contained in the HO-related message.
It should be further appreciated that the exemplary embodiments of this invention, in another aspect thereof, provide a network device, such as the eNB, that is constructed to perform HO of the UE 10, and that includes a timer unit and a unit to initiate operation of the timer unit in at least one of the target eNB 12′ and source eNB 12 after the HO procedure is started and, in the event the timer expires before the UE 10 can be expected to respond to a HO-related message sent from the source eNB 12, to initiate a communication to the UE 10 on a Paging channel from at least one of the target eNB 12′ and source eNB 12, where the communication includes information contained in the HO-related message.
Referring to
The UE 10 may be in the Active state for Steps B and C, or it may transition to the IDLE state before beginning to listen to the Paging channel.
It should be further appreciated that the exemplary embodiments of this invention, in a further aspect thereof, provide a UE 10 resident computer program product that functions to perform a HO procedure by: initiating operation of a timer after the start of the HO procedure; and, in the event the timer expires before the UE 10 receives an expected HO-related message sent from a source eNB, to begin listening to a Paging channel of a current cell and, optionally, to Paging channel(s) of neighboring cell(s); to receive the expected HO-related message and associated information from a received page; and to continue with the HO procedure using the HO-related message and associated information received through the Paging channel.
It should be further appreciated that the exemplary embodiments of this invention, in still another aspect thereof, provide the UE 10 that is constructed to a perform HO procedure, and that includes a timer unit and a unit to initiate operation of the timer unit after the start of the HO procedure; where in the event the timer unit expires before the UE 10 receives an expected HO-related message sent from a source eNB, the UE 10 begins to receive a Paging channel of a current cell and, optionally, a Paging channel(s) of neighboring cell(s); to receive the expected HO-related message and associated information from a received page; and to continue with the HO procedure using the HO-related message and associated information received through the Paging channel.
In
In
Further, in
In
In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, logic flow diagrams, message flow diagrams, or by using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
As such, it should be appreciated that at least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be fabricated on a semiconductor substrate. Such software tools can automatically route conductors and locate components on a semiconductor substrate using well established rules of design, as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility for fabrication as one or more integrated circuit devices.
Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this invention.
Furthermore, some of the features of the various non-limiting and exemplary embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.
This patent application claims priority under 35 U.S.C. § 119(e) from Provisional Patent Application No. 60/840,283 filed Aug. 25, 2006, the disclosure of which is incorporated by reference herein in its entirety.
Number | Date | Country | |
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60840283 | Aug 2006 | US |