Method and apparatus for transmitting indication in wireless communication system
09736744 · 2017-08-15
Assignee
Inventors
Cpc classification
International classification
H04W4/00
ELECTRICITY
Abstract
A method and apparatus for transmitting an indication in a wireless communication system is provided. An eNodeB (eNB) of a first system transmits an indication, which indicates that handover of a user equipment (UE) from the eNB to a radio network controller (RNC) of a second system is a necessary handover, to the RNC. In addition, a method and apparatus for receiving an indication for inter-radio access technology (RAT) unnecessary handover in a wireless communication system is provided. An eNB of a first system transmits a request for measuring, by a UE, quality of signals from the first system, and information related to the inter-RAT unnecessary handover, and receives an indication for the inter-RAT unnecessary handover.
Claims
1. A method for transmitting an indication in a wireless communication system, the method being performed by a first eNodeB (eNB) and comprising: receiving, from a second eNB, an inter radio access technology (IRAT) ping-pong detection indication, the IRAT ping-pong detection indication indicating that an IRAT ping-pong is detected by the second eNB, the IRAT ping-pong being a handover of a user equipment (UE) from the first eNB to the second eNB via a radio network controller (RNC); transmitting, to the RNC, a request for a handover report message; receiving, from the RNC, the handover report message indicating whether or not the IRAT ping-pong is an unnecessary handover in response to the request; performing a handover of the UE from the first eNB to the RNC; and transmitting, to the second eNB via the RNC, an IRAT necessity indication based on the handover report message, wherein the IRAT necessity indication indicates that the handover of the UE from the first eNB to the RNC is a necessary handover when the handover report message indicates that the IRAT ping-pong is not the unnecessary handover.
2. The method of claim 1, wherein the first eNB and the second eNB are based on: a 3rd generation partnership project (3GPP) long term evolution (LTE); or an evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN).
3. The method of claim 1, wherein the RNC is based on a universal mobile telecommunications system (UMTS) terrestrial radio access network (UTRAN).
4. The method of claim 1, wherein, if a moving path of the UE is not always present within the coverage of the first eNB and the second eNB, the handover report message indicates that the IRAT ping-pong is not an unnecessary handover.
5. A first eNodeB (eNB), comprising: a radio frequency (RF) unit configured to transmit and receive a radio signal; and a processor operatively coupled to the RF unit, the processor being configured to: receive, from a second eNB, an inter radio access technology (IRAT) ping-pong detection indication, the IRAT ping-pong detection indication indicating that an IRAT ping-pong is detected by the second eNB, the IRAT ping-pong being a handover of a user equipment (UE) from the first eNB to the second eNB via a radio network controller (RNC); transmit, to the RNC, a request for a handover report message; receive, from the RNC, the handover report message indicating whether or not the IRAT ping-pong is an unnecessary handover in response to the request; perform a handover of the UE from the first eNB to the RNC; and transmit, to the second eNB via the RNC, an IRAT necessity indication based on the handover report message, wherein the IRAT necessity indication indicates that the handover of the UE from the first eNB to the RNC is a necessary handover when the handover report message indicates that the IRAT ping-pong is not the unnecessary handover.
6. The first eNB of claim 5, wherein the first eNB and the second eNB are based on: a 3rd generation partnership project (3GPP) long term evolution (LTE); or an evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN).
7. The first eNB of claim 5, wherein the RNC is based on a universal mobile telecommunications system (UMTS) terrestrial radio access network (UTRAN).
8. The first eNB of claim 5, wherein, if a moving path of the UE is not always present within the coverage of the first eNB and the second eNB, the handover report message indicates that the IRAT ping-pong is not an unnecessary handover.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DESCRIPTION OF EXEMPLARY EMBODIMENTS
(16) The technology described below can be used in various wireless communication systems such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), etc. The CDMA can be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA-2000. The TDMA can be implemented with a radio technology such as global system for mobile communications (GSM)/general packet ratio service (GPRS)/enhanced data rate for GSM evolution (EDGE). The OFDMA can be implemented with a radio technology such as institute of electrical and electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), etc. IEEE 802.16m is an evolution of IEEE 802.16e, and provides backward compatibility with an IEEE 802.16-based system. The UTRA is a part of a universal mobile telecommunication system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of an evolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA in downlink and uses the SC-FDMA in uplink. LTE-advance (LTE-A) is an evolution of the 3GPP LTE.
(17) For clarity, the following description will focus on the LTE-A. However, technical features of the present invention are not limited thereto.
(18) Detection of inter-radio access technology (RAT) ping-pong is described below.
(19)
(20) Referring to
(21) A user equipment (UE) moves from the E-UTRAN cell 1 to the E-UTRAN cell 2. A path of the UE is always in coverage of the E-UTRAN cell 1 and/or the E-UTRAN cell 2. However, the UE may be handed over from the E-UTRAN cell 1 to the UTRAN cell, and handed over to the E-UTRAN cell 2 again within a definable limited time. This may happen when threshold of the E-UTRAN cell is set too high, and signal strength of the UTRAN cell is good. Even though the UE is always in the coverage of the E-UTRAN cell 1 and/or the E-UTRAN cell 2, the UE may be handed over to the UTRAN cell by very short time.
(22) To detect inter-RAT ping-pong, two step solutions may be proposed.
(23) 1) Step 1 is based on enhanced UE history information including a HO cause value and possible ping-pong indication on X2 interface. Statistics regarding inter-RAT ping-pong occurrences are collected by the responsible node, and the statistics regarding the inter-RAT ping-pong occurrence may be based on evaluation of UE history information IE in a handover required message.
(24) That is, in case of inter-system handover from the E-UTRAN to the UTRAN, the source eNB shall, if supported, include HO cause value IE in the UE history information IE of the handover required message. For example, in
(25) Table 1 shows UE history information. The UE history information contains information about cells that a UE has been served by in active state prior to the target cell.
(26) TABLE-US-00001 TABLE 1 IE type and Semantics Assigned IE/Group Name Presence Range reference description Criticality Criticality Last Visited Cell 1 to Most recent — — List <MaxNr information is OfCells> added to the top of this list >Last Visited M — — Cell Information
(27) Table 2 shows last visited cell information. The last visited cell information may contain E-UTRAN or UTRAN cell specific information.
(28) TABLE-US-00002 TABLE 2 IE type and Semantics Assigned IE/Group Name Presence Range reference description Criticality Criticality CHOICE Last Visited M — — Cell Information >E-UTRAN Cell >>Last Visited E- M — — UTRAN Cell Information >UTRAN Cell >>Last Visited M OCTET — — UTRAN Cell STRING Information >GERAN Cell >>Last Visited M — — GERAN Cell Information
(29) Table 3 shows last visited E-UTRAN cell information. The last visited E-UTRAN cell information contains information about a cell that is to be used for RRM purposes.
(30) TABLE-US-00003 TABLE 3 IE type and Semantics Assigned IE/Group Name Presence Range reference description Criticality Criticality Global Cell ID M E-UTRAN — CGI 9.2.1.38 Cell Type M 9.2.1.66 — Time UE stayed M INTEGER The duration of the — in Cell (0 . . . 4095) time the UE stayed in the cell in seconds. If the UE stays in a cell more than 4095 s, this IE is set to 4095. Time UE stayed O INTEGER The duration of the YES ignore in Cell (0 . . . 40950) time the UE stayed Enhanced in the cell in 1/10 Granularity seconds. If the UE stays in a cell more than 4095 s, this IE is set to 40950. HO Cause O 9.2.1.3 The cause for the YES ignore Value handover from the E-UTRAN cell.
(31) Referring to Table 1 to Table 3, the HO cause value is additionally included in the UE history information.
(32) If the evaluation indicates a potential inter-RAT ping-pong and the source eNB of the 1st inter-RAT handover is different than the target eNB of the 2nd inter-RAT handover, the target eNB may use a HO report message to indicate the occurrence of potential inter-RAT ping-pong to the source eNB. For example, in
(33) Table 4 shows a HO report message. The HO report message contains information for too early inter-RAT HO without connection failure.
(34) TABLE-US-00004 TABLE 4 IE/Group IE type and Name Presence Range reference Semantics description HO Type M ENUMERATED (LTE to UTRAN, LTE to GERAN, . . .) HO Report M ENUMERATED The “Early IRAT Type (Unnecessary HO Handover” code-point shall to another RAT, . . . , be used by the RNC Early IRAT according to TS 25.413 [19]. Handover) HO Source M IRAT Cell ID Contains the cell ID of the ID B.1.8 source cell for the HO. This IE shall contain an E- UTRAN CGI, and shall be set to the same value as the Reporting Cell Identifier IE in TS 48.018 [18] HO Target M IRAT Cell ID Contains the cell ID of the ID B.1.8 target cell for the HO. This IE shall contain either a UTRAN Cell ID or a GERAN Cell ID. Candidate 1 to Cell List <maxNrOf CandidateCells> >Candidate M IRAT Cell ID This IE shall contain an E- Cell ID B.1.8 UTRAN CGI.
(35) Referring to Table 4, a HO report type field in the HO report message includes ‘Early IRAT Handover’. That is, the eNB2 may indicate the eNB1 that the inter-RAT ping-pong may occur by using the HO report type included in the HO report message.
(36) 2) Step 2 is based on the unnecessary HO to another RAT procedure. For detecting the inter-RAT ping-pong coverage verification may be performed to check if the mobility to other RAT was inevitable. If E-UTRAN coverage during the inter-RAT ping-pong needs to be verified for the purpose of determining corrective measures, the unnecessary HO to another RAT procedure may be used.
(37) That is, like the unnecessary HO to another RAT procedure, the eNB1 request the RNC that a UE measures LTE signals and the RNC reports measurement reports to the eNB1. If an inter-RAT handover towards LTE is executed from the RNC within the indicated measurement period, the measurement period expires. In this case, the RNC may also send the HO report. No HO report shall be sent in case no E-UTRAN cell could be included, or if the indicated period of time is interrupted by an inter-RAT handover to a RAT different than LTE or by an intra-UMTS handover with SRNC relocation or inter-BSS handover. As described in Table 4, ‘Early IRAT Handover’ code-point may be used for the HO report of the RNC.
(38) According to the two step solutions shown in
(39)
(40) Referring to
(41) Therefore, if the eNB1 concludes that UEs should be handed over to the 3G cell first, then the eNB1 needs to indicate the necessity of handover to the eNB2. Accordingly, a method for transmitting an indication which notifies that the handover from the eNB1 to the RNC is a necessary handover, when the eNB and the RNCs performs handover after concluding that the handover to the 3G cell is not the unnecessary handover, may be proposed.
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(43) At step S100, an eNB2 detects an inter-RAT ping-pong, and transmits an indication of the inter-RAT ping-pong to an eNB1. This step corresponds to the step 1 procedure shown in
(44) At step S200, the eNB1 request an RNC that UEs measure LTE signals, and the RNC reports that handover of UEs is not unnecessary. This step corresponds to the step 2 procedure shown in
(45) Based on the measurement reports received by the RNC, the eNB1 may know that the handover to an RNC1 is not unnecessary. Accordingly, the eNB1 keeps handing over UEs to the RNC1 first, and does not handover UEs to the eNB2 directly. In this case, at step S300, the eNB1 hands over UEs to the RNC1 with indication which indicates that this handover from the eNB1 to the RNC1 is a necessary handover. At step S310, the RNC1 hands over UEs to an RNC2 with indication which indicates that this handover from the eNB1 to the RNC1 is a necessary handover. At step S320, the RNC2 hands over UEs to the eNB2 with indication which indicates that this handover from the eNB1 to the RNC1 is a necessary handover.
(46) Upon receiving the indication, the eNB2 may know that detected inter-RAT ping-pong is not the unnecessary handover. Accordingly, at step S330, the eNB2 does not detect inter-RAT ping-pong, and does not transmit the indication of the inter-RAT ping-pong to the eNB1.
(47) According to an embodiment shown in
(48) The inter-RAT ping-pong requires 1) unnecessary HO to another RAT, and 2) short staying time at another RAT. Therefore, if the inter-RAT ping-pong occurs, the unnecessary HO to another RAT also occurs. It means that, by avoiding the unnecessary HOs to another RAT, it is possible to avoid the inter-RAT ping-pong.
(49) Based on this comprehension, the reason why the inter-RAT ping-pong is distinguished from the unnecessary HO to another RAT is to apply different handover policy to the inter-RAT ping-pong. For example, it is possible that in case that the UE will stay at another RAT (3G network) shortly, even though the signal strength of the LTE in 3G cell coverage is low, the eNB does not hand over the UE to the 3G network. This case corresponds to the inter-RAT ping-pong. On the other hand, it is possible that in case that UE will stay at another RAT (3G network) lengthy, only when the signal strength of the LTE in the 3G cell coverage is high, the eNB does not hand over the UE to the 3G network. This case corresponds to the unnecessary HO to another RAT.
(50) Accordingly, a method for distinguish short stay UEs at 3G network (inter-RAT ping-pong UEs) in the step 2 procedure may be proposed.
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(52) At step S210, the eNB1 hands over the UE to the RNC with request for measuring quality of signals from LTE, and staying time threshold of the UE at 3G network.
(53) At step S211, the RNC hands over the UE to the eNB2. At step S212, the RNC detects the inter-RAT unnecessary HO. In this case, staying time of the UE at the 3G network is measured.
(54) At step S213, if the measure staying time of the UE at the 3G network is smaller than the staying time threshold of the UE at the 3G network, the RNC transmits an indication about the inter-RAT unnecessary HO which cause the inter-RAT ping-pong.
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(56) At step S220, the eNB1 hands over the UE to the RNC with request for measuring quality of signals from LTE, and measuring staying time of the UE at the 3G network.
(57) At step S221, the RNC hands over the UE to the eNB2. At step S222, the RNC detects the inter-RAT unnecessary HO. In this case, staying time of the UE at the 3G network is measured.
(58) At step S223, the RNC transmits an indication about the inter-RAT unnecessary HO with the staying time of the UE at the 3G network.
(59) According to embodiments shown in
(60) In the current discussion about step 2 procedure shown in
(61)
(62) Referring to
(63) Accordingly, a method for recognizing a cell identification of LTE which the UE (which requested to measure LTE signals while it stays at 3G network) is finally handed over to may be proposed.
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(65) At step S230, the eNB1 hands over the UE to the RNC with request for measuring quality of signals from LTE. At step S231, the RNC hands over the UE to the eNB2. At step S232, the RNC detects the inter-RAT unnecessary HO.
(66) At step S233, the RNC transmits an indication about the inter-RAT unnecessary HO with an identity of an LTE cell which the UE was finally handed over to.
(67)
(68) At step S240, the eNB1 hands over the UE to the RNC with request for measuring quality of signals from LTE, and an identity of a destination LTE cell. At step S241, the RNC hands over the UE to the eNB2. At step S242, the RNC detects the inter-RAT unnecessary HO, and checks an identity of an LTE cell which the UE was handed over.
(69) At step S243, if the identity of the LTE cell where the UE was handed over is the same as the identity of the destination LTE cell, the RNC transmits an indication about the inter-RAT unnecessary HO.
(70) According to embodiments shown in
(71) Meanwhile, current step 2 procedure shown in
(72) 1) When the eNB1 requests the RNC that the UE measures LTE signals during it stays in 3G network, the RNC cannot recognize whether this request is for ‘unnecessary HO detection’ or ‘inter-RAT ping-pong detection’.
(73) 2) If the RNC cannot recognize whether the request of the eNB1 is for ‘unnecessary HO detection’ or ‘inter-RAT ping-pong’ detection, the indicated measurement period may be used for two options. That is, if it is assumed that the signal strength from LTE when the UE stays at 3G network is strong enough, the indicated measurement period may indicate either a period of time to measure LTE signals for ‘unnecessary HO detection’, or a time threshold for ‘inter-RAT ping-pong detection’. If the indicated measurement period indicates the time threshold for ‘inter-RAT ping-pong detection’, if staying time of the UE at 3G network is smaller than the time threshold, then it is considered as the inter-RAT ping-pong. Otherwise, it is not considered as the inter-RAT ping-pong. The period of time to measure LTE signals for ‘unnecessary HO detection’ and the time threshold for ‘inter-RAT ping-pong detection’ are different each other, and usually the former is much shorter than the latter.
(74) 3) When the RNC reports the detected information to the eNB1, the source eNB cannot recognize whether this report is for ‘unnecessary HO detection’ or ‘inter-RAT ping-pong detection’. For example, in case that the RNC includes ‘Early IRAT Handover’ field in the HO report, if the purpose of measurement request from the eNB1 was ‘unnecessary HO detection’, then the indicated measurement period might be set long, therefore the report about ‘inter-RAT ping-pong’ detection is not correct information to the eNB1.
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(76) At step S250, the eNB1 hands over the UE to the RNC with request for measuring quality of signals from LTE, and with an indication about whether the request is for inter-RAT ping-pong detection or unnecessary HO detection.
(77) At step S251, the RNC hands over the UE to the eNB2. At step S252, the RNC detects the inter-RAT unnecessary HO. At step S253, the RNC transmits an indication about the inter-RAT unnecessary HO.
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(79) At step S260, the eNB1 hands over the UE to the RNC with request for measuring quality of signals from LTE. At step S261, the RNC hands over the UE to the eNB2. At step S262, the RNC detects the inter-RAT unnecessary HO. In this case, staying time of the UE at the 3G network is measured.
(80) At step S263, the RNC transmits an indication about the inter-RAT unnecessary HO with the staying time of the UE at the 3G network.
(81)
(82) An eNB 800 includes a processor 810, a memory 820, and an RF (radio frequency) unit 830. The processor 810 may be configured to implement proposed functions, procedures, and/or methods in this description. Layers of the radio interface protocol may be implemented in the processor 810. The memory 820 is operatively coupled with the processor 810 and stores a variety of information to operate the processor 810. The RF unit 830 is operatively coupled with the processor 810, and transmits and/or receives a radio signal.
(83) An RNC 900 may include a processor 910, a memory 920 and a RF unit 930. The processor 910 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor 910. The memory 920 is operatively coupled with the processor 910 and stores a variety of information to operate the processor 910. The RF unit 930 is operatively coupled with the processor 910, and transmits and/or receives a radio signal.
(84) The processors 810, 910 may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The memories 820, 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. The RF units 830, 930 may include baseband circuitry to process radio frequency signals. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in memories 820, 920 and executed by processors 810, 910. The memories 820, 920 can be implemented within the processors 810, 910 or external to the processors 810, 910 in which case those can be communicatively coupled to the processors 810, 910 via various means as is known in the art.
(85) In view of the exemplary systems described herein, methodologies that may be implemented in accordance with the disclosed subject matter have been described with reference to several flow diagrams. While for purposed of simplicity, the methodologies are shown and described as a series of steps or blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the order of the steps or blocks, as some steps may occur in different orders or concurrently with other steps from what is depicted and described herein. Moreover, one skilled in the art would understand that the steps illustrated in the flow diagram are not exclusive and other steps may be included or one or more of the steps in the example flow diagram may be deleted without affecting the scope and spirit of the present disclosure.