`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`
`(51) International Patent Classification 7 :
`
`
`
`(11) International Publication Number:
`WO 0035121
`
`HO04B 7/02, H04Q 7/38
`
`
`15 June 2000 (15.06.00)
`(43) International Publication Date:
`
`
`(21) International Application Number: PCT/EP98/07949|(81) Designated States: AL, AM, AT, AU, AZ, BA, BB, BG, BR,
`
`BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD,
`
`
`GE, GH, GM, HR, HU, ID,IL, IN, IS, JP, KE, KG, KP,
`KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK,
`MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG,
`
`
`SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU,
`ZW, ARIPO patent (GH, GM, KE, LS, MW, SD, SZ, UG,
`ZW), Eurasian patent (AM, AZ, BY, KG, KZ, MD, RU, TI,
`
`
`TM), European patent (AT, BE, CH, CY, DE, DK, ES, FI,
`
`
`FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OAPI patent
`(BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE,
`
`
`SN, TD, TG).
`
`
`
`
` (74) Agent: PELLMANN, Hans-Bernd; Tiedtke-Buhling—Kinne,
`Published
`Bavariaring 4, D-80336 Miinchen (DE).
`With international search report.
`
`
`PCT
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`(22) International Filing Date:
`
`8 December 1998 (08.12.98)
`
`(71) Applicant (for all designated States except US): NOKIA
`NETWORKSOY[FI/FI]; P.O. Box 300, FIN-00045 Nokia
`Group(FI).
`
`
`
`(72) Inventor; and
`(75) Inventor/Applicant (for US only): RINNE, Mikko, J. [FI/FI];
`Nokia Networks OY, P.O. Box 407, FIN-00045 Nokia
`Group (FI).
`
`
`
`
`
`
`
`
`
`($4) Title) A METHOD FOR CALL SETUP IN A RADIO TELECOMMUNICATION NETWORK USING MACRO DIVERSITY
`
`CDMA_NW
`
`Ss
`
`Ls|7 Le|7
`
`Rell
`
`BCCH_1
`(BSIC_1)
`
`BCCH.i
`(e8te_t)
`
`BOCH_N
`(BSIC_N)
`
`(57) Abstract
`
`The present invention proposes a method for providing macro diversity in a radio telecommunication network (CDMA_NW) when
`establishing a communication link, with the method substantially residing in transmission of a newly specified first signal to a selected base
`station (BS) when setting up communication within an access request message (ARM), and wherein upon receipt of each respective access
`grant message a dedicated control channel DCCHis establisched between a respective requesting first type radio transceiver device (MS)
`and the respective plurality of second type radio transceiver devices (BS), the identification codes of which were included in the access
`request message (ARM)and which transmitted a respective one of said access grant messages (AGM). The present invention relates to
`the respective methods performed by the first and second type transceiver devices as well as to the respective devices as such and to a
`telecommunications network comprising the same and operated according to the proposed methods,
`
`
`
`1
`
`DELL 1017
`
`DELL 1017
`
`1
`
`

`

`Zimbabwe
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.
`Albania
`ES
`Lesotho
`SI
`Slovenia
`Armenia
`FI
`Lithuania
`SK
`Slovakia
`Austria
`FR
`SN
`Luxembourg
`Senegal
`Australia
`GA
`Latvia
`Swaziland
`GB
`Monaco
`Chad
`Azerbaijan
`GE
`Bosnia and Herzegovina
`Republic of Moldova
`Togo
`Barbados
`GH
`Madagascar
`Tajikistan
`Belgium
`Turkmenistan
`The former Yugoslav
`Burkina Faso
`Republic of Macedonia
`Turkey
`Mali
`Bulgaria
`Trinidad and Tobago
`Benin
`Ukraine
`Mongolia
`Brazil
`Mauritania
`Uganda
`Belarus
`Malawi
`United States of America
`Canada
`Mexico
`Uzbekistan
`Central African Republic
`Viet Nam
`Niger
`Congo
`Netherlands
`Yugoslavia
`Switzerland
`Norway
`Céte d'Ivoire
`New Zealand
`Cameroon
`Poland
`China
`Portugal
`Cuba
`Romania
`Russian Federation
`Czech Republic
`Sudan
`Germany
`Denmark
`Sweden
`Estonia
`Singapore
`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`LS
`LT
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Ireland
`Israel
`Iceland
`Italy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People’s
`Republic of Korea
`Republic of Korea
`Kazakstan
`Saint Lucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`TD
`TG
`TJ
`
`™T
`
`R
`TT
`UA
`UG
`Us
`UZ
`VN
`YU
`ZW
`
`2
`
`

`

`WO 00/35121
`
`PCT/EP98/07949
`
`A METHOD FOR CALL SETUP IN A RADIO TELECOMMUNICATION NETWORK USING
`MACRODIVERSITY
`
`FIELD OF THE INVENTION
`
`The present invention relates to a method for setting up
`
`communication in a radio telecommunication network with
`
`10
`
`reduced possibility of failure in connection setup. The
`present invention also relates to accordingly adapted
`devices operated in the network and a corresponding system.
`
`BACKGROUND OF THE INVENTION
`
`15
`
`Conventionally,
`
`in radio telecommunication networks a
`
`communication is established between a first type of radio
`
`transceiver devices which may move within the network
`
`(hereinafter mobile stations MS) and a respective one of a
`
`plurality of second type radio transceiver devices which
`
`20
`
`are stationary (hereinafter base station BS) and constitute
`
`the network. Hitherto, such networks were operated
`
`according to a time divisional multiple access (TDMA)
`
`method. However, due to the increasing traffic load, most
`
`recent developments in mobile telecommunication, for
`
`25
`
`example, use a method of code divisional multiple access
`
`(CDMA) or wideband code divisional multiple access (WCDMA),
`
`to increase the available traffic capacity in the network.
`
`Such a CDMA and/or WCDMA method may also easily be combined
`
`In principle, according to CDMA, a
`with the TDMA method.
`channel is not specified by a time slot for transmission,
`
`30
`
`but by the code used for transmission. Thus, using CDMA, it
`
`becomes possible to transmit on a plurality of channels
`
`defined by a respective channelization code, within the
`
`same time slot.
`
`35
`
`3
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`WO 00/35121
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`PCT/EP98/07949
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`a
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`Now, when a user wants to communicate via the network and,
`
`for example, switches on his mobile station MS,
`
`the mobile
`
`station MS selects one of the base stations BS present in
`
`the neighborhood of and monitored by the mobile station MS.
`
`Normally,
`
`the mobile station selects the base station from
`
`which the strongest signal via the respective broadcast
`
`control channel BCCH is received in downlink DL. The BCCH
`
`is a downlink point-to multipoint channel used to broadcast
`
`system- and cell-specific information. To the selected base
`
`10
`
`station, an access request message ARM is sent from the
`
`mobile station MS in a subsequent uplink UL transmission
`
`via the random access channel RACH, requesting that a
`
`communication channel is to be established. The RACH is an
`
`uplink channel that is used to carry control information
`
`15
`
`from a mobile station.
`
`The base station answers this request, if a channel can be
`
`assigned to the requesting mobile station, with an access
`
`grant message AGM via the access grant channel AGCH.
`
`20
`
`In consequence, a so-called dedicated control channel DCCH
`
`is established between the mobile and base station as a
`
`result of the above described "handshaking". The DCCH is a
`
`bi-directional channel that is used to carry control
`information between the network, i.e.
`the respective base
`
`25
`
`station, and the mobile station.
`
`The above mentioned channels are logical channels each,
`
`which are respectively mapped to a physical channel. For
`
`30
`
`example,
`
`the BCCH is mapped to the primary common control
`
`the RACH is mapped to the
`physical channel (Primary CCPCH),
`physical random access channel
`(PRACH), while the DCCH is
`
`mapped to the dedicated physical data channel
`
`(DPDCH).
`
`4
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`WO 00/35121
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`PCT/EP98/07949
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`oS ee
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`A further detailed description of the fundamental logical
`
`and physical channel structure is considered to be
`
`dispensable here, since the fundamentals are set out in
`
`corresponding ETSI technical specifications / technical
`
`reports (see for example ETSI, TR 101 146 V3.0.0 of
`
`December 1997, pages 31 et seq., setting out technical
`
`details for the Universal Mobile Telecommunications System
`
`UMTS intended to be operated according to WCDMA).
`
`10
`
`However, when setting up a radio link, or, stated in other
`
`words, when setting up a DCCH for subsequent data
`
`communication on traffic channels of a radio link, such an
`
`initially established link is rather sensitive to
`
`fluctuations, i.e. changes in the channel conditions. Such
`changes may be caused due to the rapidly moving mobile
`
`15
`
`station and/or due to the changed environmental conditions
`like mountains / high buildings coming unexpectedly between
`
`the mobile station MS and the base station BS which is
`
`expected to send and/or previously sent the access grant
`
`20
`
`message AGM.
`
`Hence, since such fluctuations may be significant,
`the
`initial link for a DCCH may be affected quite heavily,
`which can often lead to an interruption of the DCCH, and
`thus to a failed connection setup.
`
`25
`
`In the American IS-95 system as a known radio
`
`telecommunication system operating according to CDMA, a
`
`stand-alone dedicated control channel SDCCH is set up in
`the beginning of the connection for performing the
`
`30
`
`"handshaking" in setting up the connection. However, also
`the link established with this SDCCH according to the
`American IS-95 standard, accordingly,
`is as sensitive to
`
`fluctuations on the corresponding radio link as described
`
`5
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`

`

`WO 00/35121
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`PCT/EP98/07949
`
`og
`
`before. This SDCCH does not support macro diversity, which
`
`means a simultaneous connection to several base stations.
`
`Likewise, other known radio telecommunications systems like
`
`GSM and others operating on the basis of a "pure" TDMA
`
`method, do not provide a feature of macro diversity.
`
`SUMMARY OF THE INVENTION
`
`10
`
`Consequently, it is an object of the present invention to
`
`provide a method for setting up communication in a radio
`
`telecommunication network with reduced possibility of
`
`failure in connection setup. Moreover, it is an object of
`
`the present invention to provide corresponding devices
`
`15
`
`adapted to carry out the method of the invention and
`
`constituting a novel telecommunication system.
`
`According to the present invention, with regard to a first
`
`type radio transceiver device (mobile station),
`
`this object
`
`20
`
`is achieved by a method performed by a first type radio
`
`transceiver device for setting up at least one
`
`communication channel between said first type radio
`
`transceiver device and at least one of a plurality of
`
`second type radio transceiver devices, said second type
`
`25
`
`radio transceiver devices constituting a radio
`
`telecommunication network, said method comprising the steps
`
`of listening to the respective broadcast control channel of
`
`said plurality of second type radio transceiver devices,
`
`recognizing a respective identification code used by a
`respective one of said plurality of second type radio
`
`30
`
`transceiver devices and transmitted on at least one of said
`
`respective broadcast control channels, composing an access
`
`request message based on said recognized identification
`
`codes, and accessing a random access channel of a selected
`
`6
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`

`

`WO 00/35121
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`PCT/EP98/07949
`
`wai
`
`sae
`
`one of said plurality of second type transceiver stations
`
`using said access request message.
`
`Furthermore, with regard to a second type radio transceiver
`
`device (base station), this object is achieved by a method
`
`performed by a second type radio transceiver device for
`
`setting up a communication channel between a first type
`
`radio transceiver device and said second type radio
`
`transceiver device, said second type transceiver device
`
`10
`
`being part of a radio telecommunication network constituted
`
`by a plurality of said second type radio transceiver
`
`devices, said method comprising the steps of listening to
`
`an access request message transmitted from said first type
`
`radio transceiver device on a random access channel to said
`
`15
`
`second type radio transceiver device, and composed of a
`
`plurality of identification codes of respective second type
`
`radio transceiver devices, decomposing said access request
`
`message into the plurality of identification codes,
`
`recognizing the identification codes used by said second
`
`20
`
`type radio transceiver devices, creating an access grant
`
`message based on said particular recognized identification
`
`code of said second type transceiver device, and accessing
`
`an access grant channel of said second type transceiver
`
`station using said access grant message.
`
`25
`
`Moreover,
`
`the underlying object is achieved by a method for
`
`providing macro diversity in a radio telecommunication
`
`network when establishing a communication link,
`
`the method
`
`comprising the steps as defined in any of claims 1 to 5,
`the steps as defined in any of claims 6 to 12, and wherein
`
`30
`
`upon receipt of each respective access grant message a
`dedicated control channel is established between a
`
`respective requesting first type radio transceiver device
`
`and the respective plurality of second type radio
`transceiver devices,
`the identification codes of which were
`
`35
`
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`

`

`WO 00/35121
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`PCT/EP98/07949
`
`-— E—
`
`included in the access request message, and which
`
`transmitted a respective one of said access grant messages.
`
`Also,
`
`the invention provides correspondingly adapted first
`
`and second type transceiver devices and a radio
`
`telecommunication system comprising the same.
`
`Favorable refinements of the present invention are defined
`
`in the respective dependent claims.
`
`Accordingly, with the present invention it is in advantage
`
`possible to establish macro diversity in a telecommuni-
`
`like for example a CDMA system, already in
`cation system,
`the beginning of establishing a connection.
`In particular,
`this advantage is attributable to the fact of the specific
`signal transmission that is effected at a very first time
`
`between a requesting mobile station MS and a base station
`
`BS, when a dedicated channel like for example a dedicated
`
`control channel DCCH is to be set up.
`
`Furthermore, due to specifically composing of the access
`
`request message by (compression) coding the plural base
`
`station identification codes BSIC,
`
`the access request
`
`messages ARM can advantageously be kept short.
`
`The present invention can also advantageously be applied to
`common telecommunications standards in relation to the air
`
`interface in Europe as well as in Japan.
`
`In particular, it
`
`can be used also in connection with most recently developed
`or just being developed standards like for example
`UMTS/IMT-2000, or the standard developed by NTTDoCoMo.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`15
`
`20
`
`25
`
`30
`
`8
`
`

`

`WO 00/35121
`
`PCT/EP98/07949
`
`a
`
`In the following,
`
`the present invention will be described
`
`with reference to the drawings,
`
`in which:
`
`1 schematically shows, as an example, a CDMA
`Fig.
`telecommunications network consisting of base stations BS,
`with a mobile station MS present therein, and signals
`transmitted there between in an initial stage of setting up
`a connection;
`
`10
`
`Fig. 2 illustrates a flow chart of the method carried out
`
`at the mobile station side when setting up a connection;
`
`IS
`
`20
`
`Fig.
`
`3 illustrates a flow chart of the method carried out
`
`at the base station side when setting up a connection;
`
`4 depicts a block diagram of basic hardware structure
`Fig.
`of a mobile station adapted to implement the present
`invention;
`
`5 depicts a block diagram of basic hardware structure
`Fig.
`of a base station adapted to implement the present
`invention; and
`
`6 is a schematic diagram as an example for the used
`Fig.
`data format of the proposed access request message ARM.
`
`25
`
`DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
`
`In a CDMA system, each base station BS as a second type
`radio transceiver device broadcasts an information about
`which codes are available at the base station via the BCCH.
`A respective mobile station recognizes this code as
`transmitted on the BCCH of a first base station. The first
`or selected base station is, for example,
`the one which
`transmits the strongest one of the received signals when
`
`30
`
`35
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`

`

`WO 00/35121
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`PCT/EP98/07949
`
`= BP =
`
`the mobile station monitors the CDMA system network.
`
`Subsequently,
`
`the mobile station uses this code to access
`
`the RACH for connection setup.
`
`According to the present
`invention, it is suggested to
`immediately add more than one base station when setting up
`a connection or radio link, respectively,
`to thereby
`provide macro diversity already at the initial stage of
`connection setup. This is attributable to the modification
`
`10
`
`of the first signal that is transmitted from a respective
`
`mobile station MS to the selected base station when a
`
`dedicated control channel DCCH is to be set up.
`
`In
`
`particular, this modification resides in the inclusion of
`
`the identification of other base stations BS to be included
`
`15
`
`in an active set of base stations by means of which macro
`diversity is provided,
`into the first access request or
`random access, respectively.
`
`In order to keep the initially transmitted message short,
`which is a requirement resulting from the conditions
`
`20
`
`the
`imposed by signal run time delay on the air interface,
`base station identification codes are specifically composed
`to form an access request message to be transmitted in the
`
`25
`
`the identification
`access request burst. Advantageously,
`codes of the base stations are encoded, preferably
`compressed encoded by subtracting a code value of
`neighboring base stations from the code value of the
`selected first (predetermined) base station to thereby
`produce a considerably shorter value to be encoded in the
`
`30
`
`access request message.
`
`The efficient use of compression by subtraction makes it
`desirable that the identifiers of nearby or neighboring
`base stations are close to each other (in terms of their
`
`10
`
`10
`
`

`

`WO 00/35121
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`PCT/EP98/07949
`
`-9.
`
`code values). However, this is not a pre-requisite for the
`present invention for being properly carried out.
`
`The above described aspects are now set out in greater
`detail herein below.
`
`Fig.
`
`1 schematically shows a radio telecommunications
`
`network CDMA_NW consisting of plural base stations BS
`
`(BS_1, ..., BS_i, ..., BS_N), with a mobile station MS
`present therein, and signals transmitted there between in
`
`10
`
`an initial stage of setting up a connection. As shown in
`Fig. 1, each of the base stations BS_1, ..., BS_i, ...,
`BS_N broadcasts on the respective BCCH (BCCH_l,
`...,
`BCCH_i,
`..., BCCH_N)
`information about what code (preamble
`code)
`is available in the cell associated to the respective
`base station. This broadcast information is referred to as
`
`base station identifier code (or identifier) BSIC and
`denoted by BSIC_1, ..., BSIC_i, «...BSIC_N.
`
`Nevertheless, alternatively, each broadcast control channel
`
`1 may
`BCCH of a respective base station BS shown in Fig.
`indicate (not shown in Fig. 1)
`the identifications BSIC of
`
`neighboring cells in addition to its own identifier code.
`
`This will avoid that a mobile station MS will have to
`
`decode plural BCCH messages which do not originate from the
`selected ("best") base station transmitting the strongest
`Signal to the mobile station MS. Then,
`the mobile station
`
`would immediately have a knowledge of plural or even all
`identifier codes BSIC_1, ..., BSIC_N of the neighboring
`base stations after decoding only the strongest received
`BCCH signal.
`
`15
`
`20
`
`25
`
`30
`
`A respective mobile station MS receives these information
`
`of the identifier code, processes it (as described further
`below), and creates an access request message ARM
`
`35
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`= Ei =
`
`transmitted via the random access channel RACH to the
`
`respective base station BS which has been selected, i.e.
`
`which provides the strongest signal received at the mobile
`
`station MS.
`In Fig. 1, for explanatory purposes only, base
`station BS_1 is assumed to represent the selected base
`
`station,
`
`to which the access request message ARM is sent
`
`via the random access channel RACH1.
`
`The access request message ARM is composed of respective
`
`10
`
`selected base station identifier codes BSIC's, and thus
`
`adapted to establish a radio link between the mobile
`
`station MS and each of those base stations BS the
`
`identifier codes of which are contained in the access
`
`request message ARM.
`
`In response to the receipt of the ARM,
`
`15
`
`a respective selected base station BS,
`
`the BSIC of which
`
`base station was contained in the ARM, sends (not shown in
`
`Fig. 1) an access grant message AGM to the mobile station,
`
`if access to a channel provided by the respective base
`
`station is possible. Subsequently,
`
`for example a dedicated
`
`20
`
`control channel DCCH (not shown in Fig. 1) will be
`
`established between the mobile station MS and the
`
`respective base station BS. According to the present
`
`invention, as a result, at least one but preferably two or
`
`more control channels like DCCH's are simultaneously active
`
`25
`
`between the mobile station MS and respective base stations
`
`thereby providing macro diversity from the very
`BS,
`beginning of connection setup. Those base stations BS which
`
`have established a link to the mobile station constitute
`
`the so-called active set of base stations providing macro
`diversity.
`
`30
`
`2 shows a flow chart of the method steps as carried
`Fig.
`out at the mobile station MS side when setting up a
`connection.
`In step S0,
`the procedure starts after a user
`has, for example, switched on his mobile station.
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`35
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`WO 00/35121
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`= 2 .-
`
`Subsequently, during a step Sl,
`
`the mobile station MS
`
`listens to the BCCH's broadcast from the respective base
`
`stations.
`
`In the next step, step S2,
`
`the mobile station MS
`
`derives or recognizes the respective base station
`
`identifier code BSIC from the listened BCCH information.
`
`This may be achieved by listening to each of the BCCH's,
`
`or, alternatively, by listening only to the strongest (as
`
`the selected) of the received BCCH's, provided that on the
`
`BCCH of each base station BS also the identifiers BSIC's of
`
`10
`
`the neighboring base stations are additionally indicated.
`
`Based on the plurality of recognized identifier codes
`
`BSIC's,
`
`the mobile station MS composes,
`
`in step S3, an
`
`access request message ARM to be sent to the base station
`
`BS which sends, for example,
`
`the strongest BCCH.
`
`15
`
`Alternatively, another base station BS to which the access
`
`request message ARM is to be transmitted may be selected,
`
`for example the one which is closest to the mobile station.
`
`However, other selection criteria can of course be adopted.
`
`20
`
`Composing the access request message in step S3 is
`
`preferably done by encoding the same so that the ARM is
`compressed and encoded.
`In a suitable manner,
`the
`
`individual BSIC's of neighboring base stations BS can be
`
`subtracted from the BSIC of a first base station, i.e. a
`
`25
`
`predetermined and/or selected base station (for example the
`
`one which has sent the strongest signal during the previous
`
`listening step).
`
`Once the access request message ARM has been composed by
`the mobile station MS,
`the mobile station uses, step S4,
`
`30
`
`the message ARM when accessing the random access channel
`
`RACH of the base station BS which has been selected.
`
`the mobile station processing is ended
`in a step S5,
`Then,
`insofar as the proposed method is concerned.
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`The random access message ARM forms part of the data
`
`transmitted in the random access burst structure.
`
`Additionally, within the random access burst data field,
`
`information as to which service is requested by the base
`
`station BS, i.e. for example set up of a dedicated control
`
`channel DCCH is included. This will be described in greater
`detail below with reference to Fig. 6.
`
`10
`
`4 of the drawings schematically shows a corresponding
`Fig.
`block circuit diagram for the mobile station MS. The
`
`respective base stations BS (BS_1 to BS_N in Fig. 1)
`broadcast in donwnlink transmission direction DL on
`
`respective BCCH's. Each BCCH carries the respective base
`
`15
`
`station identifier code BSIC. Information contained in the
`
`BCCH is received at the mobile station MS and listened to
`
`by a listening means for downlink transmission LMDL. The
`
`received and listened information is supplied to a downlink
`
`recognizing means RMDL, which recognizes the received
`...,
`individual base station identifier codes BSIC (BSIC_l,
`BSIC_i,
`..., BSIC_N) among the received information. The
`individual BSIC's are supplied to a composing means for
`uplink message composition CMUL. Based on the recognized
`BSIC's,
`the uplink composition means CMUL generates or
`composes, respectively, an access request message ARM. The
`
`thus obtained message ARM is fed to an accessing means for
`uplink transmission AMUL, which processes the ARM message
`so that it can be transmitted via the respective random
`access channel RACH (RACH_1 in Figs.
`1 & 4)
`in uplink
`transmission direction UL to the corresponding base station
`
`BS, which has been selected or predetermined.
`
`It is to be understood, that the composing means for uplink
`transmission CMUL is adapted to process the input
`information, i. e.
`the BSIC's, as described above in
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`connection with step $3. Also,
`
`the alternative mentioned
`
`above in that the BSIC identifiers of neighboring base
`
`stations are transmitted together on each BCCH of a base
`
`station is applicable in connection with the present
`
`invention.
`
`The above description was related to the present invention
`
`insofar as the mobile station side is concerned. In the
`
`following,
`
`the present invention will be described insofar
`
`10
`
`as the base station side is concerned.
`
`Fig.
`
`3 shows a flowchart of the method steps as carried out
`
`at the base station BS side when setting up a connection
`
`(radio link).
`In step $6,
`the procedure starts at a
`respective base station constituting the network, i.e.
`
`15
`
`either at the selected base station BS or a non-selected
`
`one of the base stations.
`
`In step S7,
`
`the base station
`
`listens to the access request message ARM transmitted via
`
`the random access channel RACH from a requesting mobile
`station MS.
`
`20
`
`In step S8 it is checked whether the ARM message is
`
`received by the base station. This can for example be done
`by checking a message discriminator contained in said ARM
`
`25
`
`message. Alternatively, it is conceivable to send the ARM
`
`message only during a specified time window during which it
`can be received. Other checking methods are however also
`
`conceivable.
`
`30
`
`this means
`If the ARM message is received (YES in step $8),
`that the subject base station BS is the selected one (e.g.
`BS_1 in Fig. 1). Then the flow proceeds with steps S9 to
`$12 and S16.
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`Namely,
`
`then the thus received access request message ARM
`
`is decomposed,
`
`in a step S89,
`
`to thereby obtain the
`
`individual base station identifier codes BSIC of which the
`
`access request message ARM has previously been composed
`
`prior to transmission. Then,
`
`in a step S10,
`
`the base
`
`station BS recognizes its proper base station identifier
`
`code BSIC (BSIC_1 in the chosen example) contained in the
`
`received access request message for further using the same.
`
`Remaining and/or other base station identifier codes BSIC
`
`10
`
`which do not identify the subject base station but other
`
`base stations of the network (like e.g. identifiers
`
`..., BSIC_N in the chosen example) are
`BSIC_2,..., BSIC_i,
`transmitted to a network control element like a base
`
`station controller BSC. Using this recognized BSIC,
`
`the
`
`15
`
`base station BS then creates, step S11, an access grant
`
`message AGM,
`
`in case a channel can be offered by the base
`
`station to the requesting mobile station. Thereafter, ina
`
`step S12,
`
`the base station accesses the access grant
`
`channel AGCH for transmitting the access grant message AGM
`
`20
`
`to the requesting mobile station.
`
`In step $16,
`
`the base
`
`station processing is terminated insofar as the proposed
`method is concerned.
`
`If, however,
`
`the ARM message is not received (NO in step
`
`25
`
`$8),
`
`this means that the subject base station BS is not the
`
`selected one but presumably one which belongs to the
`
`selected active set for providing macro diversity (e.g.
`
`BS2,
`
`..., BS_N in Fig. 1). Then the flow proceeds with
`
`steps S13 to $16.
`
`30
`
`In step S13, it is checked whether a base station
`
`identifier BSIC, particularly the identifier of the subject
`base station (i.e. BSIC_i if base station BS_i is
`concerned)
`is received from the base station controller
`
`35
`
`BSC. If not, NO in step $13,
`
`this indicates that the
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`identifier of the subject base station was not contained in
`
`the ARM message and that the base station does not form
`
`part of the active set. The flow proceeds then to step S16
`and the procedure ends.
`
`If the identifier BSIC of the subject base station is
`received, YES in step S13, this indicates that the
`
`identifier of the subject base station was contained in the
`
`ARM message and that the base station does form part of the
`
`the base
`in a subsequent step S14,
`active set. Then,
`station creates an access grant message AGM in case a
`channel can be offered by the base station to the
`the
`requesting mobile station. Thereafter,
`in a step S15,
`base station accesses the access grant channel AGCH for
`transmitting the access grant message AGM to the requesting
`mobile station.
`In step S16,
`the base station processing is
`terminated insofar as the proposed method is concerned.
`
`By the above processing,
`those base stations BS which form
`the active set for providing macro diversity are enabled to
`establish a channel to the requesting mobile station,
`if a
`respective channel is available.
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`10
`
`15
`
`20
`
`5 of the drawings schematically shows a corresponding
`Fig.
`block circuit diagram for the base station device BS. The
`
`25
`
`transmits or sends
`requesting mobile station MS (not shown)
`the previously composed access request message ARM in
`uplink direction on an associated random access channel
`
`to the selected or predetermined base
`RACH (RACH_i)
`Station, for example the i-th base station BSi . At the
`base station side,
`the information contained in the RACH is
`received and listened to using a listening means for uplink
`transmission LMUL. The uplink listening means LMUL is
`adapted to provide the received access request message ARM
`at its output for further processing by the base station.
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`The access request message ARM, when received,
`
`is fed to a
`
`decomposing means DCM, which performs a reverse processing
`
`as compared to the uplink composing means CMUL at the
`
`mobile station side. This reverse processing provides, at
`
`the output of the decomposing means DCM,
`
`the individual
`
`base station identifier codes BSIC contained in the access
`
`request message. These individual codes BSIC are supplied
`
`to an uplink recognizing means RMUL which is adapted to
`
`recognize the specific identifier code BSIC_i of the
`
`subject base station BS_i among the decomposed codes. The
`recognized code associated to (or used by) and identifying
`the subject base station BS_i is output from the uplink
`recognizing means RMUL and input to a downlink composing
`
`means CMDL.
`
`10
`
`15
`
`Furthermore,
`
`the other base station identifier codes BSIC
`
`contained in the access request message ARM and obtained by
`
`decomposing the ARM message, are forwarded to the base
`
`station controller BSC (not shown) as a further network
`
`20
`
`element via an additional output terminal. The base station
`
`controller BSC in turn informs the respective base stations
`
`BS identified by their BSIC's that they are selected to
`
`form part of the active set for establishing macro
`
`diversity, and instructs the respective base stations to
`
`25
`
`compose also corresponding access grant messages AGM to be
`
`sent to the requesting mobile station via the corresponding
`
`access grant channels AGCH of the respective base stations,
`
`if a channel can be assigned.
`
`In this connection it has to
`
`be noted that all other identifier codes BSIC can be
`
`30
`
`transmitted to the remaining base stations BS which will
`
`check whether they belong to the active set. Alternatively,
`
`the base station controller BSC may inform each of these
`
`other base stations BS individually by sending the
`
`respective BSIC code of the base station to the base
`
`35
`
`Station.
`
`(See step S13 in Fig. 3).
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`The downlink composing means CMDL uses the identifier code
`
`BSIC_i of the base station in order to compose an access
`grant message AGM, if the base station BS_i has an
`available channel for the requesting mobile station MS. The
`identifier code BSIC_i used by said downlink composing
`means CMDL is either the code immediately recognized by the
`base station BS_i if said base station is the selected
`
`(strongest) one, or the BSIC_i received via the base
`station controller BSC if the subject base station is not
`
`10
`
`the selected one but is intended to belong to the active
`
`set of base stations. To this end,
`
`the downli