Mobile communication method and mobile station

Abstract

In a state where a mobile station UE is communicating with a radio base station S-eNB supporting “extended PDCP-SN,” the mobile terminal continues communications even if it performs a reconnection procedure with a radio base station T-eNB not supporting “extended PDCP-SN.” A mobile communication method according to the invention includes the steps of, when detecting RLF in the bearer in the above-described state, the mobile station UE resetting setting of “extended PDCP-SN” and establishing a bearer using “conventional PDCP-SN” by performing a reconnection procedure with a radio base station T-eNB not supporting “extended PDCP-SN.”

Claims

1. A mobile communication method, comprising the steps of: when a mobile station detects a radio link failure in a radio link with a first radio base station in a state where a bearer using an extended sequence number as a sequence number in a PDCP layer is established between the mobile station and the first radio base station, causing the mobile station to establish a bearer using a regular sequence number which is a sequence number shorter than the extended sequence number by performing a reconnection procedure with a second radio base station not supporting the extended sequence number; and causing the mobile station to reset setting of the extended sequence number and a COUNT value simultaneously when information which instructs use of the extended sequence number is not included in RRC connection reconfiguration transmitted from the second radio base station.

2. A mobile station, comprising: a transmitter/receiver; and a processor coupled to the transmitter/receiver that performs a reconnection procedure, wherein, when a radio link failure is detected by the transmitter/receiver in a radio link with a first radio base station in a state where a bearer using an extended sequence number as a sequence number in a PDCP layer is established with the first radio base station, the processor establishes a bearer using a regular sequence number which is a sequence number shorter than the extended sequence number by performing a reconnection procedure with a second radio base station not supporting the extended sequence number, and the processor resets setting of the extended sequence number and a COUNT value simultaneously when information which instructs use of the extended sequence number is not included in RRC connection reconfiguration transmitted from the second radio base station.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an overall configuration diagram of a mobile communication system according to a first embodiment of the invention.

(2) FIG. 2 is a functional block diagram of a radio base station according to the first embodiment of the invention.

(3) FIG. 3 is a functional block diagram of a mobile station according to the first embodiment of the invention.

(4) FIG. 4 is a sequence diagram showing an operation of a mobile communication system according to the first embodiment.

(5) FIG. 5 is a sequence diagram showing an operation of the mobile communication system according to Modification 1 of the invention.

(6) FIG. 6 is a diagram for illustrating a conventional mobile communication system.

(7) FIG. 7 is a diagram for illustrating the conventional mobile communication system.

(8) FIG. 8 is a diagram for illustrating the conventional mobile communication system.

(9) FIG. 9 is a diagram for illustrating the conventional mobile communication system.

(10) FIG. 10 is a diagram for illustrating the conventional mobile communication system.

(11) FIG. 11 is a diagram for illustrating the conventional mobile communication system.

(12) FIG. 12 is a diagram for illustrating the conventional mobile communication system.

(13) FIG. 13 is a diagram for illustrating the conventional mobile communication system.

(14) FIG. 14 is a diagram for illustrating the conventional mobile communication system.

MODE FOR CARRYING OUT THE INVENTION

(15) (Mobile Communication System according to First Embodiment of the Invention)

(16) Referring to FIGS. 1 to 4, a mobile communication system according to a first embodiment of the invention is described.

(17) In the embodiment, an LTE mobile communication system is described as an example, but the invention is not limited to such a mobile communication system but can be applied to a mobile communication system in any other scheme.

(18) As illustrated in FIG. 1, a mobile communication system according to the embodiment includes a radio base station S-eNB supporting “extended PDCP-SN” and a radio base station T-eNB not supporting “extended PDCP-SN,” in other words, supporting only “conventional PDCP-SN.”

(19) As illustrated in FIG. 2, a radio base station eNB according to the embodiment includes a reconnection procedure unit 11. The reconnection procedure unit 11 is configured to perform processing for a reconnection procedure of a mobile station UE.

(20) As illustrated in FIG. 3, a mobile station UE according to the embodiment includes a reconnection procedure unit 21. The reconnection procedure unit 21 is configured to perform processing for a reconnection procedure of a mobile station UE.

(21) When RLF (Radio Link Failure) is detected in a radio link with a radio base station S-eNB in a state where a bearer using “extended PDCP-SN” is established with the radio base station S-eNB, the reconnection procedure unit 21 resets the setting of “extended PDCP-SN” (and a COUNT value), and then performs a reconnection procedure with a radio base station T-eNB not supporting “extended PDCP-SN” to establish a bearer using “conventional PDCP-SN.”

(22) Hereinafter, referring to FIG. 4, an operation of a mobile communication system according to the embodiment is described.

(23) As illustrated in FIG. 4, at step S1001, when the mobile station UE detects RLF in a radio link with a radio base station S-eNB in a state where a bearer using “extended PDCP-SN” is established with the radio base station S-eNB, the mobile station UE determines to perform a reconnection procedure with a radio base station T-eNB.

(24) Here, the mobile station UE resets the COUNT value and also resets the setting of “extended PDCP-SN.”

(25) At step S1002, the mobile station UE transmits “RA preamble” to the radio base station T-eNB. At step S1003, the radio base station T-eNB transmits “RA response” to the mobile station UE.

(26) At step S1004, the mobile station UE transmits “RRC connection re-establishment request” to the radio base station T-eNB. At step S1005, the radio base station T-eNB transmits “RRC connection re-establishment” to the mobile station UE.

(27) At step S1006, the mobile station UE transmits “RRC connection re-establishment complete” to the radio base station T-eNB. At step S1007, the radio base station T-eNB transmits “RRC connection reconfiguration” to the mobile station UE. At step S1008, the mobile station UE transmits “RRC connection reconfiguration complete” to the radio base station T-eNB.

(28) In the mobile communication system according to the embodiment, when determining to perform the reconnection procedure with the radio base station T-eNB, the mobile station UE can establish a bearer using “conventional PDCP-SN” with the radio base station T-eNB while forgetting the setting of “extended PDCP-SN” and thereby can continue the communications.

(29) (Modification 1)

(30) Referring to FIG. 5, a mobile communication system according to Modification 1 of the invention is described by paying attention to a difference from the mobile communication system according to the above-described first embodiment.

(31) In the mobile communication system according to Modification 1, a reconnection procedure unit 21 is configured to, when RLF is detected in a radio link with a radio base station S-eNB in a state where a bearer using “extended PDCP-SN” is established with the radio base station S-eNB, establish a bearer using “conventional PDCP-SN” by performing a reconnection procedure with a radio base station T-eNB not supporting “extended PDCP-SN” and reset the setting of “extended PDCP-SN” and a COUNT value.

(32) Hereinafter, referring to FIG. 5, an operation of the mobile communication system according to Modification 1 is described.

(33) As illustrated in FIG. 5, at step S2001, when detecting RLF in a radio link with a radio base station S-eNB in a state where a bearer using “extended PDCP-SN” is established with the radio base station S-eNB, the mobile station UE determines to perform a reconnection procedure with a radio base station T-eNB.

(34) At step S2002, the mobile station UE transmits “RA preamble” to the radio base station T-eNB. At step S2003, the radio base station T-eNB transmits “RA response” to the mobile station UE.

(35) At step S2004, the mobile station UE transmits “RRC connection re-establishment request” to the radio base station T-eNB. At step S2005, the radio base station T-eNB transmits “RRC connection re-establishment” to the mobile station UE.

(36) At step S2006, the mobile station UE transmits “RRC connection re-establishment complete” to the radio base station T-eNB. At step S2007, the radio base station T-eNB transmits “RRC connection reconfiguration” to the mobile station UE.

(37) Here, if an information element which instructs use of “extended PDCP-SN” is not included in “RRC connection reconfiguration,” the mobile station UE resets the COUNT value and also resets the setting of “extended PDCP-SN.”

(38) At step S2008, the mobile station UE transmits “RRC connection reconfiguration complete” to the radio base station T-eNB.

(39) In the mobile communication system according to Modification 1, when determining to perform the reconnection procedure with the radio base station T-eNB, the mobile station UE can establish a bearer using “conventional PDCP-SN” with the radio base station T-eNB while forgetting the setting of “extended PDCP-SN” based on the content of “RRC connection reconfiguration” received during the reconnection procedure and thereby can continue the communications.

(40) The features of the above-described embodiment may also be expressed as follows.

(41) A first feature of this embodiment is summarized as a mobile communication method, including the steps of: when a mobile station UE detects RLF (radio link failure) in a radio link with a radio base station S-eNB (first radio base station) in a state where a bearer using “extended PDCP-SN (extended sequence number) ” as a sequence number in a PDCP layer is established between the mobile station UE and the radio base station S-eNB, causing the mobile station UE to reset setting of “extended PDCP-SN” and a COUNT value; and causing the mobile station UE to establish a bearer using “conventional PDCP-SN (regular sequence number)” which is a sequence number shorter than “extended PDCP-SN” by performing a reconnection procedure with a radio base station T-eNB (second radio base station) not supporting “extended PDCP-SN.”

(42) A second feature of this embodiment is summarized as a mobile communication method, including the steps of: when a mobile station UE detects RLF in a radio link with a radio base station S-eNB in a state where a bearer using “extended PDCP-SN” is established between the mobile station UE and the radio base station S-eNB, causing the mobile station UE to establish a bearer using “conventional PDCP-SN” by performing a reconnection procedure with a radio base station T-eNB not supporting “extended PDCP-SN”; and causing the mobile station UE to reset setting of the “extended PDCP-SN” and a COUNT value.

(43) A third feature of this embodiment is summarized as a mobile station UE, including: a reconnection procedure unit 21 configured to perform a reconnection procedure. Here, the reconnection procedure unit 21 is configured to, when RLF is detected in a radio link with a radio base station S-eNB in a state where a bearer using “extended PDCP-SN” is established with the radio base station S-eNB, reset setting of the “extended PDCP-SN” and a COUNT value, and thereafter establish a bearer using “conventional PDCP-SN” by performing a reconnection procedure with a radio base station T-eNB not supporting “extended PDCP-SN.”

(44) A fourth feature of this embodiment is summarized as a mobile station UE, including: a reconnection procedure unit 21 configured to perform a reconnection procedure. Here, the reconnection procedure unit 21 is configured to, when RLF is detected in a radio link with a radio base station S-eNB in a state where a bearer using “extended PDCP-SN” is established with the radio base station S-eNB, establish a bearer using “conventional PDCP-SN” by performing a reconnection procedure with a radio base station T-eNB not supporting “extended PDCP-SN,” and reset setting of “extended PDCP-SN” and a COUNT value.

(45) It is to be noted that the reset of the COUNT value includes reset of a related state variable.

(46) It should be noted that the foregoing operations of the mobile station UE and the radio base station eNB may be implemented by hardware, maybe implemented by a software module executed by a processor, or may be implemented in combination of the two.

(47) The software module may be provided in a storage medium in any format, such as a RAM (Random Access Memory), a flash memory, a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electronically Erasable and Programmable ROM), a register, a hard disk, a removable disk, or a CD-ROM.

(48) The storage medium is connected to a processor so that the processor can read and write information from and to the storage medium. Instead, the storage medium may be integrated in a processor. The storage medium and the processor may be provided inside an ASIC. Such an ASIC may be provided in the mobile station UE and the radio base station eNB. Otherwise, the storage medium and the processor may be provided as discrete components inside the mobile station UE and the radio base station eNB.

(49) Hereinabove, the present invention has been described in detail by use of the foregoing embodiments. However, it is apparent to those skilled in the art that the present invention should not be limited to the embodiments described in the specification. The present invention can be implemented as an altered or modified embodiment without departing from the spirit and scope of the present invention, which are determined by the description of the scope of claims. Therefore, the description of the specification is intended for illustrative explanation only and does not impose any limited interpretation on the present invention.

(50) Note that the entire content of Japanese Patent Application No. 2012-161676 (filed on Jul. 20, 2012) is incorporated by reference in the present specification.

INDUSTRIAL APPLICABILITY

(51) As described above, the invention can provide a mobile communication method and a mobile station which enables communications to be continued even when reconnection procedure with a radio base station T-eNB not supporting “extended PDCP-SN” is performed on a mobile station UE communicating with a radio base station S-eNB supporting “extended PDCP-SN.”

EXPLANATION OF THE REFERENCE NUMERALS

(52) eNB radio base station UE mobile station 11, 21 reconnection procedure unit