1111111111111111 IIIIII IIIII 11111 1111111111 1111111111 1111111111 11111 11111 1111111111 11111111
`c19) United States
`
`
`c12) Patent Application Publication
`c10) Pub. No.: US 2009/0209256 Al
`
`
`(43) Pub. Date: Aug. 20, 2009
`
`Nakashima et al.
`
`US 20090209256Al
`
`(54)MOBILE COMMUNICATION SYSTEM,AND
`
`(86)PCT No.:
`MOBILE UNIT, BASE STATION UNIT AND
`METHOD THEREFORE
`
`§ 371 (c)(l),
`
`(2), ( 4) Date:
`
`Nov.13, 2008
`
`PCT /JP2007 /059981
`
`(76)Inventors:Daiichiro Nakashima, Chiba-shi
`
`
`(51)Int. Cl.
`
`
`(JP); Hidekazu Tsuboi, Chiba-shi
`H04W 36/00 (2009.01)
`(JP)
`H04B 17100 (2006.01)
`H04M 1100 (2006.01)
`
`
`(52)U.S. Cl. ..................... 455/436; 455/67.11; 455/67.7;
`455/561
`
`
`
`Publication Classification
`
`Correspondence Address:
`
`
`BIRCH STEWART KOLASCH & BIRCH
`POBOX747
`
`
`FALLS CHURCH, VA 22040-0747 (US)
`
`(21)Appl. No.:
`
`12/300,768
`
`
`
`(22)PCT Filed:May 15, 2007
`
`
`
`(57)
`
`ABSTRACT
`
`In mobile communication system having a plurality of mobile
`
`
`
`
`
`
`
`
`
`traits and a plurality of base station units, the system of the
`
`
`
`
`present invention is characterised in that the base station unit
`
`
`
`
`
`
`has a gap period length setting section for setting the length of
`
`
`the gap period for the mobile unit depending on the type of the
`
`
`
`
`radio access technology to be monitored by the mobile unit.
`
`cl
`
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`
`APPLE 1016
`
`

`

`Patent Application Publication
`
`Aug. 20,2009 Sheet 1 of 12
`
`US 2009/0209256 Al
`
`FG 1
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`

`

`Patent Application Publication
`
`Aug. 20,2009 Sheet 2 of 12
`
`US 2009/0209256 Al
`
`FIG. 2
`
`MOBILE UNIT
`
`COMMUNICATION
`
`INSTANTANEOUS COI
`
`SECTION XVALUEWEASUREMENT
`CONTROL \ FEEDBACKINTERVAL
`
`SETTING SECTION
` INSTANTANEOUS
`
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`
`FIG, 3
`
`FEEDBACK iNTERVAL SETTING SECTION
`1200
`rt
`HEAN COI VALUE
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`MEMORY
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`GQI VALUE
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`GQI THRESHOLD VALUE
`
`MODE DECISION
`SECTION
`
`INFORMATION GONCERNING
`MOBILE COMMUN I CAT [ON
`SYSTEM TO BE MONITORED
`
`FEEDBACK INTERVAL
`SETTING SECTION
`
`FEEDBACK INTERVAL
`
`3
`
`

`

`Patent Application Publication
`
`Aug. 20,2009 Sheet 3 of 12
`
`US 2009/0209256 Al
`
`FIG 4A
`
`RADIO
`ACCESS TECHNOLOGY
`UTRA
`
`ul
`
`
`
`
`
`
`
`
`FIG. 4B
`
`LENGTH OF GAP PERIOD
`
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`
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`
`
`
`
`
`
`
`
`NON-3GPP SYSTEM
`
`
`
`
`
`4
`
`

`

`Patent Application Publication
`
`Aug. 20,2009 Sheet 4 of 12
`
`US 2009/0209256 Al
`
`LENGTH OF GAP PERIOD FOR GSM
`20 T20 T20 T20 T20 Tea
`
`
`
`(a)
`
`Cal
`
`(b)
`
`cal
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`

`

`Patent Application Publication
`
`Aug. 20,2009 Sheet 5 of 12
`
`US 2009/0209256 Al
`
`FIG 6
`
`BASE STATION UNIT
`
`COMMUNI CAT | ON
`SECT| ON
`
`INTERVAL SETTING SECTION
`
`CONTROL
`UNIT
`
`RESOURCE ALLOCATION
`
`HG. 7
`
`RESOURCE ALLOCATION INTERVAL SETTING SECTION
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`MEAN GQl
`DERIVING SECTION
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`MODE DECISION
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`SECTION
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`INFORMATION CONCERNING
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`SYSTEM TO BE MON! TORED
`BY MOBILE UNIT
`
`RESOURCE ALLOCATION
`INTERVAL SELECTION
`
`RESOURCE ALLOCATION INTERVAL
`
`6
`
`

`

`Patent Application Publication
`
`Aug. 20,2009 Sheet 6 of 12
`
`US 2009/0209256 Al
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`FIG. 8
`
`MOBILE UNIT
`
`RESET CQ1 REPORT
`TIMER
`
`
` S10
`
`
`S11
`WHICH MODE 1S
`MEASUREMENT MODE
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`THE CURRENT ODE?
`
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`NON 3GPP
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`TYPE OF
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`SET AT ORDINARY MODE $22
`
`
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`SFT AT MEASUREMENT MODE
`
`7
`
`

`

`Patent Application Publication
`
`Aug. 20,2009 Sheet 7 of 12
`
`US 2009/0209256 Al
`
`HG. 9
`
`BASE STATION UNIT
`C_start)
`
`.
`
`$100
`RESET GQ] FEEDBACK
`TIMER
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`$101
`
`Mitel MODE 18
`THE CURRENT MODE?
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`MEASUREMENT MODE
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`$103
`
`URD I NARY
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`
`UTRA
`
`TYPE OF
`RADIG ACCESS TECHNOLOGY
`TO BE MONITORED BY MOBILE
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`8
`
`

`

`Patent Application Publication
`
`Aug. 20, 2009 Sheet 8 of 12
`
`US 2009/0209256 Al
`
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`Patent Application Publication
`
`Aug. 20,2009 Sheet 9 of 12
`
`US 2009/0209256 Al
`
`BASE STATION UNIT
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`

`

`Patent Application Publication
`
`Aug. 20, 2009 Sheet 10 of 12
`
`US 2009/0209256 Al
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`Patent Application Publication
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`Aug. 20, 2009 Sheet 11 of 12
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`US 2009/0209256 Al
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`Patent Application Publication
`
`Aug. 20,2009 Sheet 12 of 12
`
`US 2009/0209256 Al
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`

`

`US 2009/0209256 Al
`
`Aug. 20, 2009
`
`MOBILE COMMUNICATION SYSTEM, AND
`MOBILE UNIT, BASE STATION UNIT AND
`METHOD THEREFORE
`
`TECHNICAL FIELD
`
`[0001] The present invention relates to a mobile communi-
`cation system, and a mobile unit, a base station unit and a
`mobile communication methodtherefore and, particularly to
`such system, and a mobile unit, a base station unit, and a
`mobile communication method adapted to provide wireless
`communication between cells to which the same frequencies
`are assigned underthe sameradio access technology, between
`cells to which mutually different frequencies are assigned
`under the same radio access technology, or between cells
`under mutually different radio access technologies.
`[0002]
`Priority is claimed on Japanese Patent Application
`No. 2006-136259 filed May 16, 2006, the content ofwhich is
`incorporated herein by reference.
`
`BACKGROUND ART
`
`Ina cellular mobile communication system based
`[0003]
`on the sameradio access technology (RAT), a numberofbase
`station units are remotely located, each of which constitutes a
`wireless communication area, thereby to provide a service
`area, wherein a mobile unit in one ofthe cells is allowed to
`have accessto the base station unit through a radio channel.
`When the mobile unit moves from one cell to another during
`on-going conversation, the so-called handover HOis per-
`formed to permit the communication to be continued in a
`seamless manner.
`
`[0004] There are two different types of handover, i.e., the
`intra-frequency handover (intra-freq HO) on one hand, and
`the inter-frequency handover(inter-freq HO) on the other.
`[0005]
`Inaddition, ina cellular mobile communication sys-
`tem based on mutually different radio access technologies,
`there is the inter-RAT handover (inter-RAT HO) performed
`when a mobile unit movesacross a cell-to-cell border based
`on mutually different radio access technologies.
`[0006] The cell-to-cell handover under the same radio
`access technology, which maybecalled intra-RAT handover
`(intra-RAT HO), is in Contrast to the last-mentioned inter-
`RAT HO.
`
`[0010] The well-known W-CDMA (wideband-code divi-
`sion multiple access) radio access technology provided by the
`3GPP (3rd generation partnership project) has been in use for
`the third generation, cellular mobile communication systems
`as the standard radio access technology. For the W-CDMA
`system, the so-called compressed modeis provided to moni-
`tor or measure the performanceofbasestation units operating
`at mutually different frequencies to provide the intra-RAT-
`HO (and inter-freq-HO) and/or inter-RAT-HO (and inter-
`freq-HO).
`[0011] Under the above-mentionedsituation, the base sta-
`tion unit sets a gap period, as show in FIG. 13 (a), during
`which the data transmission through the dedicated channel
`DPCH is stopped. Onthe other hand, the mobile unit switches
`its frequency during the gap period, thereby to monitor the
`function of the base station unit operating at a different fre-
`quency.
`Inthe 3GPP, the high speed downlink packet access
`[0012]
`HSDPAto realize for downlink a high speed packet transmis-
`sion at a maximum transmission rate of 14.4 Mbps, whichis
`an extension of W-CDMA wireless interface, has already
`been adopted as a technology standard (Non-Patent Docu-
`ment 2 referred to). In the adopted standard, high-speed
`downlink shared control channel HS-SCCH andhigh-speed
`physical downlink shared channel HS-PDSCHare addition-
`ally defined for downlink as independent channels separate
`from the above-mentioned dedicated channel to which the
`compressed mode is inherently applied. Similarly, high-
`speed dedicated physical control channel HS-DSPCCH is
`additionally defined for uplink.
`[0013]
`In the HSDPA, adaptive modulation and coding
`scheme AMCSis adopted, which switches, depending on
`downlink channel quality indicator CQI indicative of the
`current state of the transmission paths for the respective
`mobile units, wireless transmission parameters such as data
`modulation schemefor the shared data channel, error correc-
`tion scheme, codingrate for the error correction code, spread-
`ing factorsfor time/frequency domain,andthe order of code-
`multiplexing of multicodes. In addition, hybrid automatic
`repeat request scheme HARQ1s also adopted, under which a
`mobile unit sends the acknowledgement/negative acknow]-
`edgement ACK/NACKsignals and the CQIsignal hack to the
`base station unit through the dedicated control channel.
`[0014]
`FIGS. 13 (&) and 13(c) illustrate examples of packet
`[0007] Referring to FIG. 12 illustrating the handoverpro-
`signals transmitted from a base station unit to a mobile unit,
`cessing to be performed while the mobile unit is in motion,
`with FIG. 13 (6) showingashared control channelfor the base
`base station units BS1, BS2, BS3 and BS4 are separately
`station unit-to-mobile unit transmission and FIG. 13(c) show-
`located on a two-dimensional plane. These base station units
`ing a shared data channelfor the base station Unit-to-mobile
`unit transmission.
`BS1, BS2, BS3 and BS4 provide wireless communication
`links to mobile units through carrier waves at frequencies f1,
`f2, £3 and f4, respectively; and using radio access technolo-
`gies RAT1, RAT1, RAT1 and RAT2,respectively.
`[0008] Base station units BS1, BS2, BS3 and BS4 can be in
`communication with mobile units MS1, MS2, MS4 and MSG
`located in cell c1; with mobile units MS4 and MSSlocated in
`cell c2, with mobile units MS2 and MS3 located in cell c3;
`and with mobile units MS6 and MS7located in cell c4.
`
`In the HSDPA,a mobile unit does not have, during
`[0015]
`the time period corresponding to the gap period, those packet
`data allotted thereto which are addressedto itself, because the
`exchangeofdata transmission with a basestation unit cannot
`be performedif the base station unit operating at a different
`frequency is to be monitored or measured. The basestation
`unit is therefore adapted to send, in advanceofthe provision
`of the gap period, instructions to the mobile unit to stop the
`allotmentofdata for a shared data channel through the shared
`control channel. In response to the instructions, the mobile
`unit provides the gap period, thereby to perform the monitor-
`ing and the measurementofthe base station unit operating at
`a different frequency.
`[0016] More specifically, in contrastto the situation of FIG.
`13 (a), wherein the base station unit provides the gap period
`
`[0009] Mobile unit MS4 in motion betweencells cl and c2
`performsthe handoverbasedon the intra-RAT-HO(andinter-
`freq-HO). Similarly, mobile unit MS2 in motion between
`cells c1 andc3 performsthe handover based on theintra-RAT-
`HO(andintra-freq-HO); while mobile unit MS6 in motion
`between cells cl and c4 performs the handover based on the
`inter-RAT-HO(andinter-freq-HO).
`
`14
`
`14
`
`

`

`US 2009/0209256 Al
`
`Aug. 20, 2009
`
`by applying the data compression or the like to continuous
`data to be sent to a mobile unit, the gap period is provided in
`the case of FIGS. 13(6) and 13(c) by preventing the allotment
`ofthe packet control signal and the packetdata for the mobile
`unit to the gap period.
`[0017]
`It is to be noted here that the radio interface of
`W-CDMA-or HSDPA-based mobile communication system
`is generally referred to as universal terrestrial radio access
`UTRA.
`
`Further study is now in progress for the evolved
`[0018]
`universalterrestrial radio access EUTRA andfor the evolved
`universalterrestrial radio access network EUTRAN,both for
`the third generation radio access technology.
`[0019] The orthogonal frequency division multiplexing
`access OFDMA has been proposedfor providing the down-
`link for the SUTRA, while the AMOStechnique has been
`applied to the OFDMA system as the EUTRA scheme (Non-
`Patent Documents 3 and 4 referred to). For the EUTRA
`scheme,the radio frame structure for the downlink transmis-
`sion and a mapping method for the radio channel have been
`proposed (Non-Patent Document4 referred to).
`[0020]
`In regard to the intra-RAT-HO(andthe intra-freq-
`HO)and/or the inter-RAT-HO (andthe inter-freq HO) forthe
`EUTRA/EUTRAN,an autonomous gap control method for
`autonomously providing the gap period whenthe instanta-
`neous CQ] value becomeslowerthan the mean CQ]value has
`been proposed as a method for controlling the gap period to
`monitor or measure a different frequency-based base station
`unit (FIG. 1 of Non-Patent Document5 referredto).
`[0021]
`FIGS. 14(a) and 14(6) illustrate a method of con-
`trolling the gap period, which has been proposedin thepast.
`In the prior-art methodillustrated, the mobile unit receives the
`shared pilot channel, measures the instantaneous CQI values
`at a predetermined CQI measurementinterval, and reports the
`measured CQI values to the base station unit. At the same
`time, the mobile unit averages the instantaneous CQIvalues
`at a predetermined interval (a system parameter) to provide
`mean CQI values, and then compare the mean CQI values
`with a CQIthreshold value, which is also a system parameter.
`When the mean CQIvalue is lower than the CQI threshold
`value, the mobile unit sets itself in a measurement mode for
`monitoring or measuring the base station unit operating at a
`different frequency.
`[0022]
`In the measurement mode, the mobile unit stops
`receiving the signals from the base station unit currently in
`communication, thereby to provide the gap period, when the
`measured instantaneous CQI value is lower than the mean
`CQI value. Uponreceipt ofthe instantaneous CQI value from
`a certain mobile unit, the base station unit provides a mean
`CQI value for that mobile unit in a manner similar to the
`calculation at the mobile unit. The base station unit then
`
`compares the mean CQI value with a CQIthreshold value,
`which is a system parameter. When the mean CQI valueis
`higher than the CQIthreshold value, the basestation unit sets
`itself at an ordinary mode, while it sets itself at a measurement
`mode when the mean CQ]valueis lower than the CQIthresh-
`old value. In the measurement mode, the base station unit
`stops transmission of data packets to the mobile unit currently
`in communication therewith, to provide the gap period, when
`the measured instantaneous CQ]valueis lower than the mean
`CQIvalue.
`[0023] As shown in FIG.14 (a), the mobile unit terminates
`the gap period to resume the measurement of instantaneous
`CQIvalues and the report to the base station unit, after the
`
`completion of the monitoring or measurement of the base
`station unit operating at a different frequency. A similar pro-
`cessing is repeatedly performedthereafter, as shown in FIG.
`14 (6), which illustrates the successive formation ofa plural-
`ity of gap periods g1 to g6.
`[0024] A next-generation mobile unit adapted to the
`EUTRA/EUTRANis required to be operable in a plurality of
`mobile communication systems, which utilize mutually dif-
`ferent radio access technologies. More specifically, such
`next-generation, mobile unit must be operable in mobile com-
`munication systems utilizing the UTRA, GSM (global sys-
`tem for mobile communication), or other radio access tech-
`nologies, which are not specified even in the 3GPPstandards.
`Such mobile communication systems may have a different
`frame length, different frame structure, and different means
`or processes for measuring the quality of signal reception at
`the mobile units. As a result, a mobile unit under control by a
`base station unit ofthe EUTRA/EUTRANmobile communi-
`
`cation system maynot alwaysbeable toset, in the inter-RAO-
`HO(and the inter-freq-HO), the length of the gap period
`whichis optimum to such radio access technology, due to the
`difference in minimum required gap length for the monitoring
`or measurementofa different radio access technology-based
`base station unit. Whenthe length of the gap periodis set at a
`value longer than a minimum required gap, that results in an
`unutilized portion in the gap period, adversely affecting the
`spectral efficiency as well asthe timeefficiency.
`Tachikawa
`[0025] Non-Patent Document
`1: Keiji
`“W-CDMA Mobile Communication System,” ISBN4-621-
`04894-5
`
`[0026] Non-Patent Document 2:3GPP TRtechnical Report
`25.858 and HSDPAspecification—related materials (http://
`www.3gpp.org/ftp/Specs/htm]-info/25-series.htm)
`[0027] Non-Patent Document 3: 3GPP TR (Technical
`Report) 25.913, V2.1.0 (2005-05), Requirements for Evolved
`Universal Terrestrial Radio Access (UTRA) and Universal
`Terrestrial Radio Access Network (UTRAN). (http://www.
`3gpp.org/ftp/Spec/html-info/259 13 htm)
`[0028] Non-Patent Document 4: 3GPP TR (Technical
`Report) 25.814, V1.0.1 (2005-11), Physical Layer Aspects
`for Evolved UTRA. (hitp://www.3gpp.org/ftp/Specs/html-
`info/25814.htm)
`Inc.
`[0029] Non-Patent Document 5: NTT DoCoMo,
`“Measurementfor LTE Intra- and Inter-RAT Mobility,” 3GPP
`TSG RAN WG2 Meeting #50, Sophia Antipolis, France, 9-13
`Jan. 2006
`
`DISCLOSUREOF INVENTION
`
`Problem to be Solved by the Invention
`
`[0030] With a view to obviating the difficulties described
`above, it is an object of the invention to provide a mobile
`communication system, and a mobile unit, a base station unit
`and a method therefore, capable of utilizing frequency and
`time in a moreefficient manner.
`
`Meansfor Solving the Problem
`
`[0031] According to the present invention,there is provided
`a mobile communication, system having a plurality ofmobile
`units and a plurality of base station units, wherein the base
`station unit has a gap period setting section for setting the
`length of a gap period fora mobile unit, depending on the type
`of radio access technology to be monitored by the mobile
`unit.
`
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`
`[0032] According to one aspect of the invention, there is
`provided a mobile communication system of the type
`described above, wherein the gap periodsetting section ofthe
`base station unit is adaptedto set the length of the gap period
`for the mobile unit, depending onthe typeofthe radio access
`technology to be monitored and reported by the mobile unit.
`[0033] According to another aspect of the invention, there
`is provided a mobile communication system of the type
`described above, wherein the gap period setting section is
`adapted to set the lengths ofa plurality of the gap periods for
`the mobile unit, depending on the types of the radio access
`technologies to be monitored by the mobile unit.
`[0034] According to the presentinvention,there is provided
`a mobile communication system havinga plurality of mobile
`units and a plurality of base station units, wherein the base
`station unit has a gap period setting section for setting the
`length of a gap period for a mobile unit, depending on the type
`of combinations of the radio access technology to be moni-
`tored by the mobile unit and the frequency band utilized for
`the wireless communication.
`
`[0035] According to one aspect of the invention, there is
`provided a mobile communication system of the type
`described above, wherein the gap periodsetting section ofthe
`base station unit is adaptedto set the length of the gap period
`for the mobile unit, depending on the type of the combination
`of the radio access technology monitored and reported by the
`mobile unit and the frequency band utilized for the wireless
`communication.
`
`[0036] According to another aspect of the invention, there
`is provided a mobile communication system of the type
`described above, wherein the gap periodsetting section ofthe
`base station unit is adapted to simultaneously set the lengths
`ofa plurality of gap periods for the mobile unit, depending on
`the type of the combination ofthe radio access technology to
`be monitored by the mobile unit and the frequency band
`utilized for the wireless communication.
`
`[0037] According to still another aspect of the invention,
`there is provided a mobile communication system as
`described above, wherein the gap periodsetting section ofthe
`base station unit is adapted to set the lengths of the gap
`periods by resetting, when the basestation unit receives from
`a mobile unit a reception quality indicator, a gap period of a
`length set at a longer value than the short gap length among
`the plurality of the simultaneously set gap lengths, and by
`continuously setting, when the base station unit does not
`receive within the short gap length from the mobile unit a
`reception quality indicator, a gap periodset at a value longer
`than the short gap length.
`[0038] According to still another aspect of the invention,
`there is provided a mobile communication system as
`described above, wherein the mobile unit has a gap period
`setting section for setting the length of the gap period,
`dependingonthe type ofradio access technology to be moni-
`tored.
`
`[0039] According to still another aspect of the invention,
`there is provided a mobile communication system as
`described above, wherein the mobile unit has a gap period
`setting section for setting the length of the gap period,
`depending on the type of the combination ofthe radio access
`technology to be monitored and the frequency bandutilized
`for the wireless communication.
`
`decision section for determining, based on the reception qual-
`ity indicator, a measurement mode for monitoring the adja-
`cent base station unit or an ordinary modefor not monitoring
`the adjacentbase station unit, wherein the gap periodsetting
`section of the mobile unit is adapted to set the length of the
`gap period onthe basis of the decision performedat the first
`mode-decision section and the reception quality indicator,
`wherein the base station unit has a second mode-decision
`section for determining, based on file reception quality indi-
`cator fed back from the mobile unit, whether the mobile unit
`is in the measurement mode or the ordinary mode, and
`wherein the gap period setting section at the base station unit
`sets the gap length onthe basis of the decision performedat
`the second mode decision selection.
`
`[0041] According to still another aspect of the invention,
`there is provided a mobile communication system as
`described above, wherein the mobile unit has a first mode
`decision section for determining the measurement mode for
`monitoring an adjacent base station unit or the ordinary mode
`for not monitoring an adjacentbase station unit, wherein the
`gap periodsetting section of the mobile unit is adaptedto set
`the length of the gap period on the basis of the result of the
`decision performedat the first mode decision section and the
`reception quality indicator, and wherein the gap periodset-
`ting section of the base station unit is adaptedto set the length
`of the gap on the basis of the decision performedat thefirst
`mode decision section and the reception quality indicator fed
`back from the mobile unit.
`
`[0042] According to still another aspect of the invention,
`there is provided a mobile communication system as
`described above, wherein the mobile unit has a first mode
`decision section for determining, on thebasis ofthe reception
`quality indicator, the measurement mode for monitoring an
`adjacentbase station unit or the ordinary mode for not moni-
`toring a adjacent base station unit, wherein the gap length
`setting section ofthe mobile unit is adaptedto set, on the basis
`of the decision performedat the first mode decision section
`and the reception quality indicator, the length of the gap
`period, and wherein the gap length setting section of the base
`station unit is adapted to set, based on the reception quality
`indicator fed back from the mobile unit, the length of the gap
`period.
`[0043] According to a further aspect of the invention, there
`is provided a mobile unit, wherein the mobile unit adapted to
`perform wireless communication with a base station unit has
`a gap length-setting section for setting the length of the gap
`period depending onthe type of the radio access to be moni-
`tored.
`
`[0044] According to still further aspect of the invention,
`there is provided a mobile unit, wherein the mobile unit for
`performing wireless communication with a base station has a
`gap setting sectionforsetting the length ofthe gap, depending
`on the type of combination of the radio access technology to
`be monitored and the frequency bandutilized for the wireless
`communication.
`
`[0045] According to a further aspect of the invention, there
`is provided a base station unit, wherein the base station unit
`for communication with a mobile unit has a gap periodsetting
`section for setting the length of the gap period, depending on
`the type of radio access technology to be monitored by the
`mobile unit.
`
`[0040] According to still another aspect of the invention,
`there is provided a mobile communication system as
`described above, wherein the mobile unit has a first mode-
`
`[0046] According to still further aspect of the invention,
`there is provided a base station unit, wherein the base station
`unit for communication with the mobile unit has a gap setting
`
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`
`FIG. 12 illustrates the handover processing to be
`[0063]
`performed while the mobile unit is in motion.
`[0064]
`FIG. 13 shows an example of a dedicated channel
`transmitted from the base station unit to the mobile unit.
`
`FIG. 14 showsanillustration for describing a con-
`[0065]
`ventional method of controlling the gap period.
`
`REFERENCE SYMBOLS
`
`In the drawings, reference letters/numerals BS1,
`[0066]
`BS2, BS3 and BS4 denote basestation units; MS1, MS2,
`MS4 and MSG, mobile units; 11, mean CQI value deriving
`section; 12, memory; 13, mode decision section; 14, feedback
`interval selection section; 21, mean CQI value deriving sec-
`tion; 22, memory; 23, mode decision section; 24, resource
`allocation interval selection section; 30, communication sec-
`tion; 31, timer; 32, control section; 33, instantaneous CQI
`value measuring section; 34, feedback interval selection sec-
`tion; 40, communication section; 41, timer; 42, control sec-
`tion; and 43, resource allocation interval setting section.
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`First Embodiment
`
`section for setting the length of the gap period for the mobile
`unit, depending on the type ofcombination ofthe radio access
`technology to be monitored by the mobile unit andthe fre-
`quency band utilized for the wireless communication.
`[0047] According to a further aspect of the invention, there
`is provided a mobile communication method for providing
`wireless communication between a plurality of mobile units
`and a plurality of base station units, wherein the base station
`unit is adapted to set the length of the gap period for the
`mobile units, depending on the type of radio access technol-
`ogy to be monitored by the mobile unit.
`[0048] According to still further aspect of the invention,
`there is provided a mobile communication method for pro-
`viding mobile wireless communication between a plurality of
`mobile units and a plurality of base station units, wherein the
`base station unit is adaptedto set the length ofthe gap period,
`for the mobile unit, depending on the type of combination of
`the radio access technology to be monitored by the mobile
`unit and the frequency bandutilized for the wireless commu-
`nication.
`[0049] As described above, in the present invention, the
`base station unit is adaptedto set the length of the gap period
`for the mobile unit, depending on the type of radio access
`technology to be monitored by the mobile unit.
`[0050] This makesit possible for the basestation unitto set
`the length of the gap period depending on the type of radio
`[0067] A mobile communication system accordingtoafirst
`embodimentof the invention will now be described.
`access technology to be monitored by the mobile unit, with
`the result that the setting of redundant gap period can be
`avoided to utilize the radio frequency spectrum moreeffi-
`ciently.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows an example of downlink radio frame
`[0051]
`structure for a 3GPP-based EUTRA.
`
`FIG. 2 schematically showsin blocks a mobile unit
`[0052]
`accordingto a first embodimentofthe present invention.
`[0053]
`FIG. 3 schematically showsin blocksthe structure
`of feedback interval setting section 34 (FIG. 2) in thefirst
`embodiment.
`
`FIG. 4A showsthe relationship between the radio
`[0054]
`access technology usedin the first embodimentand the length
`of the gap period.
`[0055]
`FIG. 4B shows the relationship among the radio
`access technology frequency band utilized and the length of
`the gap period.
`[0056] FIG.5 showsillustration for describing the length of
`the gap period to be set by the base station unit in the first
`embodiment.
`
`FIG. 6 showsin blocks the structure of the base
`[0057]
`station unit in the first embodiment.
`
`FIG. 7 shows in blocks the structure of resource
`[0058]
`assignment interval setting section 43 (FIG.6).
`[0059]
`FIG. 8 shows a flow chart for the processing per-
`formed at feedback interval selection unit 14 of the mobile
`unit in the first embodiment.
`
`FIG. 9 shows a flow chart for the processing per-
`[0060]
`formedat resource allocation interval selection section 24 of
`the base station unit in the first embodiment.
`
`FIG. 10 shows an illustration for describing the
`[0061]
`resource allocation interval in the second embodimentof the
`invention.
`
`FIG. 11 showsa flow chart for the processing per-
`[0062]
`formedat the resource allocation interval selection section 24
`of the base station in the second embodiment.
`
`17
`
`InFIG. 1 showing an example ofthe downlink radio
`[0068]
`signal frame structure for the 3GPP-based EUTRA with time
`and frequency taken along the abscissa and the ordinate,
`respectively, the downlink radio frame consists of a plurality
`of subcarriers occupying two dimensional radio resource
`blocks RB defined by frequency bandwidth Bch and trans-
`mission timing interval TTI. In FIG. 1, BW denotesthefre-
`quency bandwidth of the downlink signal; Bch, frequency
`bandwidth of the resource block; Bsc, frequency bandwidth
`of the subcarrier