as) United States
`a2) Patent Application Publication co) Pub. No.: US 2010/0067495 Al
`(43) Pub. Date: Mar. 18, 2010
`
`Lee et al.
`
`US 2010006749S5A1
`
`(54) METHOD OF PERFORMING RANDOM
`ACCESS IN A WIRELESS COMMUNCATION
`SYSTEM
`
`(76)
`
`Inventors:
`
`Young Dae Lee, Anyang-si (KR);
`Sung Duck Chun, Anyang-si (KR);
`Sung Jun Park, Anyang-si (KR);
`Seung June Yi, Anyang-si (KR)
`
`Correspondence Address:
`MCKENNA LONG & ALDRIDGE LLP
`1900 K STREET, NW
`WASHINGTON,DC 20006 (US)
`
`(21) Appl. No.:
`
`12/312,172
`
`(22)
`
`PCTFiled:
`
`Oct. 30, 2007
`
`(86) PCT No::
`
`PCT/KR2007/005384
`
`§ 371 (©)(),
`(2), (4) Date:
`
`Apr. 29, 2009
`
`Related U.S. Application Data
`
`(60) Provisional application No. 60/863,545, filed on Oct.
`30, 2006.
`
`(30)
`
`Foreign Application Priority Data
`
`Feb; %.200% (SR) ssssessssessssesrecvesese 1020070012749
`
` E-UTRAN-
`
`
`Publication Classification
`
`(51)
`
`Int. Cl.
`HO4B 7/216
`
`(2006.01)
`
`(52) US. C0. coeeccccsccsssssssssssssveessesesseesssassssssnenees 370/335
`
`(57)
`
`ABSTRACT
`
`A method of performing random access in a wireless com-
`munication system is disclosed. The method of performing
`random access in a user equipment of a wireless communi-
`cation system which uses multiple carriers includes transmit-
`ting a preamble for random access to a network, receiving a
`random access response message from the network in
`response to the preamble, transmitting a connection setup
`request messageto the network,the connection setup request
`message requesting connection establishment with the net-
`work,and receivinga first message from the network,thefirst
`message including connection setup information and conten-
`tion resolution information in a random access procedure. If
`a user equipmentidentifier of the user equipmentis included
`in the message, the user equipment determines that it has
`successfully performed random access and performs a next
`procedure in accordance with the connection setup informa-
`tion. If the user equipmentidentifier of the user equipmentis
`not included in the message, the user equipment determines
`that it has failed in random access and transmits a random
`
`access preamble to the network again after the lapse of a
`predetermined time period.
`
`APPLE 1025
`APPLE 1025
`
`

`

`Patent Application Publication Mar. 18, 2010 Sheet 1 of 6
`
`US 2010/0067495 Al
`
`E-UTRAN |
`
`

`

`Patent Application Publication Mar. 18, 2010 Sheet 2 of 6
`
`US 2010/0067495 Al
`
`FIG. 2
`
`
`
`_ NAS Security
`
`Idle State Mobility
`Handing
`
`SAE Bearer Control|.
`
`SAE Gateway
`
`___S11||Mobility Anchring
`
`NBcD
`
`|.
`
`Connection
`
`eNB
`Measurement
`Configuration
`& Provision
`
`-
`
`-
`
`Dynamic |
`Resource
`Allocation
`(Scheduler)
`
`
`
`

`

`Patent Application Publication Mar. 18, 2010 Sheet 3 of 6
`
`US 2010/0067495 Al
`
`FIG. 3A
`
`
`
`

`

`Patent Application Publication Mar. 18, 2010 Sheet 4 of 6
`
`US 2010/0067495 Al
`
`FIG. 3B
`
`SAE Gateway
`
`
`
`

`

`
`
`RM&®S®WW.
`
`>oO
`
`a3a
`
`ooma
`BH.
`
`FIG.4
`
`Patent Application Publication Mar. 18, 2010 Sheet 5 of 6
`
`US 2010/0067495 Al
`
`M&Syy
`
`RMSX®S®&Qaws
`
`RMXSS*Oy
`
`
`
`
`
`
`
`[ALI1/L2controlinformationregionL_]Data
`
`region
`
`

`

`Patent Application Publication Mar. 18, 2010 Sheet 6 of 6
`
`US 2010/0067495 Al
`
`FIG. 5
`
`Random access preamble
`
`Random access response
`
`
`
`
`RRC connection request =
`
`RRC connection setup message and,—,
`RRCcontention resolution message
`
`
`
`
`
`FIG. 6
`
`:
`
`
`
`
`
`
`
`
`
`
`
` Random.accessresponse
`
`Random access preamble
`
`
`
`fo
`
`MACscheduling request
`
`_ -~
`
`Resource grant message and +
`MACcontention resolution message
`
`

`

`US 2010/0067495 Al
`
`Mar. 18, 2010
`
`METHOD OF PERFORMING RANDOM
`ACCESS IN A WIRELESS COMMUNCATION
`SYSTEM
`
`TECHNICAL FIELD
`
`[0001] The present invention relates to a wireless commu-
`nication system, and more particularly, to a method ofper-
`forming random access in a wireless communication system.
`
`BACKGROUND ART
`
`In a wideband code division multiple access
`[0002]
`(WCDMA)system according to asynchronous mobile com-
`munication system standard (3GPP: 3” Generation Partner-
`ship Project), examples of a downlink transmission channel
`which transmits data from a network (UTRAN: UMTSTer-
`restrial Radio Access Network) to a user equipmentinclude a
`broadcast channel (BCH) which transmits system informa-
`tion and a downlink shared channel (DL-SCH)whichtrans-
`mits usertraffic or control messages. Traffic or control mes-
`sages of downlink multicast or broadcast service (MBMS:
`Multimedia Broadcasting and Multicast Service) may be
`transmitted through the DL-SCH or a separate multicast
`channel (MCH). Meanwhile, examplesof an uplink transmis-
`sion channel which transmits data from a user equipmentto a
`network include a random access channel (RACH) which
`transmitsinitial control message and an uplink shared chan-
`nel (UL-SCH) which transmits user traffic or control mes-
`sages.
`[0003] Hereinafter, the RACH in the WCDMAsystem will
`be described. The RACHis used to transmit data of short
`length to an uplink, and some RRC messages such as RRC
`connection request message, cell update message, and URA
`update message can be transmitted through the RACH. Fur-
`thermore, a commoncontrol channel (CCCH), a dedicated
`control channel (DCCH), or a dedicated traffic channel
`(DTCH), which is one of logical channels, can be mapped
`with the RACH whichis one of transmission channels. Fur-
`thermore, the RACH whichis one oftransmission channelsis
`again mapped with a physical
`random access channel
`(PRACH)whichis one of physical channels.
`[0004]
`Ifa medium access control (MAC)layer of a user
`equipment commandsa physical layer of the user equipment
`to perform PRACHtransmission, the physical layer of the
`user equipmentselects one access slot and one signature and
`transmits PRACH preamble to the uplink depending on the
`selected result. The preamble is transmitted for an access slot
`period oflength of 1.33 ms, and one signature among 16 kinds
`of signatures is selected and transmitted for a first certain
`length of the access slot.
`[0005]
`Ifthe user equipmenttransmits the preamble, a base
`station transmits a response signal through an acquisition
`indicator channel (AICH)whichis a downlink physical chan-
`nel. The AICH transmitted in response to the preambletrans-
`mits the signature selected by the preamble fora first certain
`time period of an access slot corresponding to the access slot
`to which the preamble is transmitted. At this time, the base
`station transmits acknowledgement (ACK) or non-acknowl-
`edgement (NACK)through the signature transmitted from
`the AICH. If the user equipment receives ACK, the user
`equipment transmits a message part of 10 ms or 20 ms by
`using an orthogonal variable spreading factor (OVSF) code
`corresponding to the transmitted signature. Ifthe user equip-
`ment receives NACK, the MAC of the UE again commands
`
`the physical layer of the user equipment to perform the
`PRACHtransmission after a proper time period. Meanwhile,
`if the user equipmentdoesnot receive the AICH correspond-
`ing to the transmitted preamble, the user equipmenttransmits
`a new preamble at a power higher than that of the previous
`preamble by onelevel after a given access slot.
`[0006] Hereinafter, examples where the user equipment
`transmits messages by using the RACH in the WCDMA
`system will be described.
`[0007]
`In case of the first example, the user equipment
`whichis in an idle modetransmitsan initial control message
`to a network through the RACH. Generally, the user equip-
`ment uses the RACH when the user equipment temporally
`synchronizes with the network and when the user equipment
`desires to acquire radio resources to transmit data to an
`uplink. For example, if the user equipment is powered on and
`first accesses a new cell, the user equipment generally syn-
`chronizes with a downlink and receives system information in
`a cell where the user equipment desires to access. After
`receiving system information, the user equipment transmits
`an access request message for RRC connection. However,
`since the user equipment is not synchronized with the net-
`work temporally and does not yet acquire radio resource of
`the uplink, the user equipment uses the RACH. In other
`words, the user equipment requests the network to provide
`radio resources for transmission of a connection request mes-
`sage, through the RACH. Thebase station which has been
`requested to provide correspondingradio resourcesallocates
`properradio resources to the user equipmentso that the user
`equipment can transmit RRC connection request message.
`Then, the user equipment can transmit the RRC connection
`request message to the network through the radio resources.
`[0008]
`Incase ofthe second example, ina state that the user
`equipmentis connected with the network in a type of RRC,
`the user equipment which is in an RRC connected mode uses
`the RACH. In this case, the user equipmentis allocated with
`radio resources in accordance with radio resource scheduling
`ofthe network, and transmits data to the network through the
`allocated radio resources. However, if data to be transmitted
`do not remain in a buffer ofthe user equipmentany longer, the
`network will not allocate radio resources of the uplink any
`longer. This is because that allocating radio resources of the
`uplink to the user equipment having nodata to be transmitted
`is inefficient.
`
`[0009] The buffer status ofthe user equipmentis reported to
`the network periodically or whenevera specific event occurs.
`If new data occur in the buffer of the user equipment having
`no radio resources, since there are no radio resources of the
`uplink allocated to the user equipment, the user equipment
`uses the RACH. In other words, the user equipment requests
`the networkto provide radio resources required for data trans-
`mission, through the RACH.
`[0010] The RACHis an uplink common channel andis a
`channel available for all user equipments which desires to try
`initial access to the network. Accordingly, if two or more user
`equipments use the RACH simultaneously, collision may
`occur. If collision occurs due to the two or more user equip-
`ments, the network should select one of the user equipments
`to perform a normal procedure, and should perform next
`procedures for the other user equipments after resolving a
`problem causedby the collision. In this case, it is necessary to
`define a procedure of avoiding delay in procedures after ran-
`
`

`

`US 2010/0067495 Al
`
`Mar. 18, 2010
`
`dom accessfor the selected user equipmentand resolving the
`problem caused by collision for the other user equipments.
`
`DISCLOSURE OF THE INVENTION
`
`[0011] Accordingly, the present invention is directed to a
`method of performing random access in a wireless commu-
`nication system, which substantially obviates one or more
`problems dueto limitations and disadvantages ofthe related
`art.
`
`FIG. 4 illustrates an example ofa structure of physi-
`[0019]
`cal channels used in an E-UMTSsystem;
`[0020]
`FIG. 5 is a flow chart
`illustrating a procedure
`according to one embodimentof the present invention; and
`[0021]
`FIG. 6 is a flow chart
`illustrating a procedure
`according to another embodimentofthe present invention.
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`[0022] Hereinafter, structures, operations, and other fea-
`tures of the present invention will be understood readily by
`the preferred embodiments ofthe present invention, examples
`of which are illustrated in the accompanying drawings.
`Embodiments described later are examples in which techni-
`cal features of the present invention are applied to E-UMTS
`(Evolved Universal Mobile Telecommunications System).
`[0023]
`FIG.
`1
`illustrates
`a network structure of an
`E-UMTS. An E-UMTSis a system evolving from the con-
`ventional WCDMA UMTSandits basic standardization is
`currently handled by the 3GPP (3” Generation Partnership
`Project). The E-UMTScanalso be called an LTE (Long Term
`Evolution) system. Release 7 and Release 8 of 3GPPtechni-
`cal specifications (3”” Generation Partnership Project; Tech-
`nical Specification Group Radio Access Network) can be
`referred to obtain detailed information about the UMTSand
`E-UMTS.
`
`[0012] An object of the present invention is to provide a
`method of performing random access in a wireless commu-
`nication system, in which random accessis provided to avoid
`unnecessary delay in the wireless communication system.
`[0013] Another object ofthe present inventionis to provide
`a method ofperforming random access in a wireless commu-
`nication system, in which radio resourcesare efficiently used
`in the wireless communication system.
`[0014]
`To achieve these objects and other advantages andin
`accordance with the purpose of the invention, as embodied
`and broadly described herein, a method of performing ran-
`dom accessin a user equipmentof a wireless communication
`system which uses multiple carriers comprises transmitting a
`preamble for random access to a network, receiving a random
`access response message from the network in responseto the
`preamble, transmitting a connection setup request message to
`the network, the connection setup request message requesting
`connection establishment with the network, and receiving a
`first message from the network, the first message including
`[0024] Referring to FIG. 1, an E-UTRANincludes base
`connection setup information and contention resolution
`stations (hereinafter, referred to as ‘eNode B’ or ‘eNB’),
`information in a random access procedure. If a user equip-
`wherein respective eNBs are connected with each other
`mentidentifier of the user equipmentis included in the mes-
`through X2interface. Also, each of eNBs is connected with a
`sage, the user equipmentrealizes that it has succeeded in
`user equipment (UE) through a radio interface and connected
`random access and performsa next procedure in accordance
`with EPC (Evolved Packet Core) through Si interface. The
`with the connection setup information.If the user equipment
`EPCincludes a mobility managemententity/system architec-
`identifier of the user equipmentis not included in the mes-
`ture evolution (MME/SAE) gateway.
`sage, the user equipmentrealizes that it has failed in random
`[0025] Layers of a radio interface protocol between a UE
`access and transmits a random access preamble to the net-
`and a network can beclassified into a first layer L1, a second
`work again after the lapse of a predetermined time period.
`layer L2 and a third layer L3 based on three lowerlayers of
`[0015]
`In another aspect of the present invention, a method
`OSI (open system interconnection) standard model widely
`of performing random access in a user equipmentof a wire-
`known in communication systems. A physical layer belong-
`less communication system which uses multiple carriers
`ing to the first layer L1 provides an information transfer
`comprises transmitting a preamble for random access to a
`service using a physical channel. A radio resource control
`networkinastate that the user equipmentis connected with
`(hereinafter, abbreviated as ‘RRC’) locatedat the third layer
`the network, receiving a random access response message
`plays arole in controlling radio resources between the UE and
`from the network in response to the preamble, the random
`the network. For this, the RRC layer enables RRC messages
`access response message including a temporary user equip-
`to be exchanged between the UE andthe network. The RRC
`mentidentifier of the user equipment, requesting the network
`layer can be distributively located at network nodes including
`to allocate uplink resources, and receiving at least one of a
`Node B, an AG andthelikeor at either the Node B or the AG.
`resource grant message and a contention resolution message
`[0026]
`FIG. 2isaschematic view illustrating an E-UTRAN
`from the network by using the temporary user equipment
`(UMTSterrestrial radio access network). In FIG. 2, a hatch-
`identifier and a private user equipmentidentifier of the user
`ing part represents functional entities of a user plane and a
`equipment.
`non-hatching part represents functional entities of a control
`plane.
`[0027] FIG.3A and FIG.3B illustrate a structure ofa radio
`interface protocol between the user equipment (UE) and the
`E-UTRAN,in which FIG.3A is a schematic view ofa control
`plane protocol and FIG.3B is a schematic view ofa user plane
`protocol. Referring to FIG. 3A and FIG.3B, a radio interface
`protocolvertically includes a physicallayer, a data link layer,
`and a network layer and horizontally includes a user plane for
`data information transfer and a control plane for signaling
`transfer. The protocol layers in FIG. 3A and FIG. 3B can be
`classified into L1 (first layer), L2 (second layer), and L3 (third
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG.1 illustrates a network structure ofan E-UMTS
`[0016]
`(Evolved-Universal Mobile Telecommunications System);
`[0017] FIG.2is aschematic view illustrating an E-UTRAN
`(Evolved Universal Terrestrial Radio Access Network);
`[0018] FIG.3A and FIG. 3B illustrate a structure ofa radio
`interface protocol between a user equipment (UE) and E-UT-
`RAN,in which FIG. 3A is a schematic view ofa control plane
`protocol and FIG. 3B is a schematic view of a user plane
`protocol;
`
`

`

`US 2010/0067495 Al
`
`Mar. 18, 2010
`
`layer) based on three lowerlayers of the open system inter-
`connection (OSI) standard model widely known in the com-
`munications systems.
`[0028] The physical layeras thefirst layer provides infor-
`mationtransfer service to an upperlayer using physical chan-
`nels. The physical layer (PHY) is connected to a medium
`access control (hereinafter, abbreviated as ‘MAC’) layer
`above the physical layer via transport channels. Data are
`transferred between the medium access control layer and the
`physical layer via the transport channels. Moreover, data are
`transferred between different physical layers, and more par-
`ticularly, between one physical layer of a transmitting side
`and the other physical layer of a receiving side via the physi-
`cal channels. The physical channel of the E-UMTS1s modu-
`lated according to an orthogonal frequency division multi-
`plexing (OFDM)scheme,andtime and frequencyare used as
`radio resources.
`
`[0029] The medium access control (hereinafter, abbrevi-
`ated as ‘MAC’) layer ofthe secondlayer providesa service to
`a radio link control (hereinafter, abbreviated as ‘RLC’) layer
`above the MAClayervia logical channels. The RLC layer of
`the second layer supports reliable data transfer. In order to
`effectively transmit IP packets (e.g., [Pv4 or IPv6) within a
`radio-communication period having a narrow bandwidth, a
`PDCPlayer of the second layer (L2) performs header com-
`pression to reduce the size of a relatively-large IP packet
`header containing unnecessary control information.
`[0030] Aradio resource control (hereinafter, abbreviated as
`“RRC’) layer located on a lowest part of the third layer is
`defined in the control plane only andis associated with con-
`figuration, reconfiguration and release ofradio bearers (here-
`inafter, abbreviated as ‘RBs’) to be in charge of controlling
`the logical, transport and physical channels. In this case, the
`RB meansa service provided by the secondlayer for the data
`transfer between the UE and the UTRAN.
`
`[0031] As downlink transport channels carrying data from
`the network to UEs, there are provided a broadcast channel
`(BCH)carrying system information, a paging channel (PCH)
`carrying paging message, and a downlink shared channel
`(SCH)carryingusertraffic or control messages. Thetraffic or
`control messages ofa downlink multicast or broadcast service
`can be transmitted via the downlink SCH or an additional
`downlink multicast channel (MCH). Meanwhile, as uplink
`transport channels carrying data from UEsto the network,
`there are provided a random access channel (RACH) carrying
`an initial control message and an uplink shared channel (UL-
`SCH)carrying user traffic or control message. As logical
`channels located above the transport channels and mapped
`with the transport channels, there are provided a broadcast
`channel (BCCH), a paging control channel (PCCH), a com-
`mon control channel (CCCH), a multicast control channel
`(MCCH), and a multicast traffic channel (MTCH).
`[0032]
`In the E-UMTS system, an OFDM is used on the
`downlink and a single carrier frequency division multiple
`access (SC-FDMA)onthe uplink. The OFDM schemeusing
`multiple carriers allocates resources by unit of multiple sub-
`carriers including a groupof carriers and utilizes an orthogo-
`nal frequency division multiple access (OFDMA) as an
`access scheme.
`
`[0033] A physical layer of an OFDM or OFDMA scheme
`divides active carriers into a plurality of groups and transmits
`respective groups to different receiving sides. Radio resource
`allocated to each UE whichis defined by a time-frequency
`region on a two-dimensional sphere comprises continuous
`
`sub-carriers. A time-frequency region in the OFDM or
`OFDMA schemeis a rectangular form sectioned by time and
`sub-carrier coordinates. In other words, one time-frequency
`region could be a rectangular form sectioned by at least one
`symbol on a time axis and sub-carriers on a frequency axis.
`Such a time-frequency region can be allocated to an uplink for
`a specific UE, or an eNB can transmit the time-frequency
`region to a specific UE in a downlink.In orderto define such
`a time-frequency region on the two-dimensional sphere, the
`number of OFDM symbols and the numberof continuous
`sub-carriers starting from a point having an offset from a
`reference point should be given.
`[0034] The E-UMTSwhichis currently being discussed
`uses 10 ms radio frame comprising 20 sub-frames. Namely, a
`sub-framehas a length of 0.5 ms. A resource block comprises
`one sub-frame and twelve sub-carriers, each of which is 15
`kHz. One sub-frame comprises a plurality of OFDM symbols
`and a part (for example, first symbol) of the plurality of
`OFDM symbols can be used for transmission of L1/L2 con-
`trol information.
`
`FIG. 41s a diagram illustrating a structure of physi-
`[0035]
`cal channels used in the E-UMTS. In FIG. 4, a sub-frame
`comprises an L1/L2 control information transmission region
`(the hatching part) and a data transmission region (the non-
`hatching part).
`illustrating a procedure
`[0036]
`FIG. 5 is a flow chart
`according to one embodimentofthe present invention. In the
`embodiment of FIG. 5,
`technical features of the present
`invention are applied to a procedureof initial random access
`of a user equipment whichis in an idle mode.
`[0037] Referring to FIG. 5, the user equipmenttransmits a
`random access preamble to a base station eNB [S51]. In other
`words, the user equipmentselects a specific signature among
`aplurality of signatures through one accessslot and transmits
`the selected signature to the base station. At this time, the
`random access preamble may include uplink message infor-
`mation or channel measurement information so that the base
`station may perform resource allocation for uplink message
`transmission. In this case, if at least two user equipments
`simultaneously perform uplink transmission of random
`access preambles by using sameradio resources such as same
`signatures, collision may occur.
`[0038] The basestation transmits a random access response
`message to the user equipment in response to the random
`access preamble [S52]. The random access response message
`includes the signature transmitted from the user equipment,
`grantor rejection information ofthe random access preamble
`transmission, a temporary cell radio network temporary iden-
`tifier (Temporary C-RNTI) allocated to the user equipment,
`and control information related to transmission of the RRC
`connection request message, etc. The control information
`related to transmission of the RRC connection request mes-
`sage includes radio resource allocation information, a mes-
`sage size, and radio parameters (modulation and codinginfor-
`mation and hybrid ARQ information) for transmission of the
`RRC connection request message.
`[0039] The basestation transmits signaling information for
`receiving the random access response message to the user
`equipment through L1/L2 control channel. The signaling
`information includes a random access radio network tempo-
`rary identifier (RA-RNTI) indicating transmission ofthe ran-
`dom access response message and transmission parameters
`related to transmission of the random access response mes-
`sage. Since the RA-RNTIis previously forwarded from the
`
`

`

`US 2010/0067495 Al
`
`Mar. 18, 2010
`
`user equipmentto the base station through system informa-
`tion, etc., the user equipment acquires the signaling informa-
`tion through the L1/L2 control channel by using the RA-
`RNTI and receives the random access response message by
`using the acquired signaling information.
`[0040]
`Ifthe signature transmitted from the user equipment
`and grant information for signature transmission are included
`in the random access response message, the user equipment
`transmits the RRC connection request message to the base
`station [S53]. At this time, the user equipment transmits the
`RRC connection request messageto the base station by using
`the uplink radio resource allocation information, the message
`size, and the radio parameters, which are included in the
`random access response message. The RRC connection
`request message includes a user equipmentidentifier for iden-
`tifying the user equipment. Examples of the user equipment
`identifier include wideband UEidentifiers such as an inter-
`
`national mobile subscriber identity (MSI) or a temporary
`mobile subscriber identity (TMSI).
`[0041]
`Ifthe signature transmitted from the user equipment
`and the rejection information of the signature transmission
`are includedin the random access response message,or if the
`signature transmitted from the user equipment 1s not included
`in the random access response message, the user equipment
`retransmits the random access preamble after a certain time
`without transmitting the RRC connection request message.
`[0042]
`Ifthe RRC connection request message is received
`from the user equipment, the RRC layer of the base station
`transmits the RRC connection setup message or the RRC
`contention resolution message to the user equipment. Prefer-
`ably,
`the RRC layer transmits one RRC message which
`includes the RRC connection setup message and the RRC
`contention resolution message. For another example, after
`transmitting the RRC connection setup message to the user
`equipment,the base station can transmit the RRC contention
`resolution message.
`[0043]
`Ifone RRC message which including the RRC con-
`nection setup message and the RRC contention resolution
`messageis transmitted, padding includedin the message can
`be reduced, whereby the radio resources can be used effi-
`ciently. The RRC message includes user equipmentidentifier
`of a user equipment which has succeeded in random access.
`Preferably, the user equipmentidentifier is a user equipment
`identifier included in the RRC connection request message,
`for example, IMS] and TMSI.
`[0044]
`Ifa plurality of user equipments collide with one
`another during a transmission procedure ofthe random access
`preamble or the RRC connection setup message, only one
`user equipment which has successfully performed random
`access is operated in accordance with the RRC connection
`setup message. In this case, the success ofthe user equipment
`which has succeeded in the random access means that the
`random access preamble transmitted from the user equipment
`has been successfully received by the base station and then
`the RRC connection request has been successfully per-
`formed.
`
`[0045] As described above, the RRC connection setup mes-
`sage included in the RRC message includes the wideband
`user equipmentidentifier such as IMS] and TMS]ofthe user
`equipment which has succeeded in the random access. The
`user equipment receives control
`information required to
`receive the RRC message through the L1/L2 control channel
`by using its temporary C-RNTI. For example, the user equip-
`ment can identify whether a specific channel of the L1/L2
`
`control channelis transmitted to itself in accordance with the
`result of cyclic redundancy code (CRC)test of the specific
`channel by using the temporary C-RNTI. For another
`example, the user equipmentreceives a message indicated by
`the temporary C-RNTIif the temporary C-RNTI1s received
`through the L1/L2 control channel. If the specific channelis
`transmitted to the user equipment,
`the user equipment
`receives the RRC messagetransmitted to a downlink channel
`of a data region, for example, a downlink shared channel
`(DL-SCH)by using control information transmitted through
`the specific channel.
`[0046]
`Ifthe wideband user equipmentidentifier transmit-
`ted through the RRC connection request messageis included
`in the RRC connection setup message, the user equipment
`realizes that it has succeeded in the random access and rec-
`ognizes the RRC connection setup messageas its message. At
`this time, the user equipmentuses the temporary user equip-
`mentidentifier (temporary C-RNTIT)as a private C-RNTI for
`performing communication with a networklater.
`[0047]
`Ifthe wideband user equipmentidentifier transmit-
`ted through the RRC connection request message is not
`included in the RRC message, the user equipmentrealizes
`that it has failed in the random access. Also, if the RRC
`message which includes the wideband user equipment iden-
`tifier is not received for a certain time period, the user equip-
`mentrealizes that it has failed in the random access. Atthis
`
`time, the user equipmentcan start a random access procedure
`again by retransmitting the random access preamble to the
`base station after a certain time period.
`[0048] The aforementioned embodiments of the present
`invention can be applied to a random access procedure for
`initial access performedafter radio link failure or handover.
`[0049]
`FIG. 6 is a flow chart
`illustrating a procedure
`according to another embodimentof the present invention. In
`the embodiment of FIG. 6, technical features of the present
`invention are applied to a random access procedure of a user
`equipment whichis in an RRC connected mode. For example,
`if radio resourcesfor data to be transmittedto the base station
`
`are not allocated to the user equipment, the user equipment
`can transmit data through the random access procedure
`through the RACH. The embodiments described hereinafter
`can be applied to the case where the basestation 1s not uplink-
`synchronized with the user equipment even though it has
`downlink data to be transmitted to the user equipment which
`is in the RRC connected mode.
`
`[0050] Referring to FIG.6, the user equipmenttransmits a
`random access preamble to the base station eNB [S61], and
`receives a random access response message from the base
`station in response to the random access preamble [S62].
`Since the steps S61 and S61 are the same as S51 and S52 of
`FIG.5, their detailed description will be omitted.
`[0051]
`Ifthe signature transmitted from the user equipment
`and grant information for signature transmission are included
`in the random access response message, the user equipment
`transmits a MAC scheduling request message to the base
`station [S63]. At this time, the user equipment transmits the
`MACscheduling request message to thebasestation by using
`the uplink radio resource allocation information, the message
`size, and the radio parameters, which are included in the
`random access response message. Preferably,
`the MAC
`scheduling request message includes a wideband user equip-
`mentidentifier for identifying the user equipment. Examples
`of the user equipmentidentifier include wideband UE iden-
`tifiers such as international mobile subscriber identityMSI)
`
`

`

`US 2010/0067495 Al
`
`Mar. 18, 2010
`
`identity (TMSI). The
`temporary mobile subscriber
`or
`embodimentof FIG.6 is different from that of FIG. 5 in that
`
`scheduling request and contention resolution procedures are
`performed by the MAClayer.
`[0052]
`Ifthe signature transmitted from the user equipment
`and the rejection information of the signature transmission
`are includedin the random access response message,or if the
`signature transmitted from the user equipmentis not included
`in the random access response message, the user equipment
`retransmits the random access preamble after a certain time
`without transmitting the MAC scheduling request message.
`[0053]
`Ifthe MAC scheduling request messageis received
`from the user equipment, the MAClayerofthe base station
`transmits a resource grant message and MAC contention
`resolution message to the user equipment [S64]. The base
`station may simultaneously transmit the resource grant mes-
`sage and the MAC contention resolution message or may
`transmit the MAC contention resolution messageafter trans-
`mitting the resource grant message.
`[0054] The resource grant message may be transmitted
`through the L1/L2 control channel, or may be transmitted
`through L1 signaling by using a physical channelfor resource
`allocation, such as an absolute grant channel (AGCH)or a
`relative grant channel (RGCH). On the other hand, the MAC
`contenti