(12) United States Patent
`Steudle
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006810019B2
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,810,019 B2
`Oct. 26, 2004
`
`(54) REDUCING INTERFERENCE IN INTER(cid:173)
`FREQUENCY MEASUREMENT
`
`(75)
`
`Inventor: Ville Steudle, Turku (FI)
`
`2003/0108027 A1 * 6/2003 Kim et al.
`.................. 370/345
`2003/0193969 A1 * 10/2003 Pecen et al. ................ 370/509
`2003/0207696 A1 * 11/2003 Willenegger et al. ....... 455/522
`2004/0116110 A1 * 6/2004 Amerga et al. .......... 455/422.1
`
`(73) Assignee: Nokia Mobile Phones Ltd., Espoo (FI)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.c. 154(b) by 754 days.
`
`(21) Appl. No.: 09/782,360
`
`(22) Filed:
`
`Feb. 13,2001
`
`(65)
`
`Prior Publication Data
`
`US 2001/0022782 A1 Sep. 20, 2001
`
`(30)
`
`Foreign Application Priority Data
`
`Feb. 18, 2000
`
`(FI) ............................................. 20000380
`
`Int. CI? ............................. H04Q 7/38; H04B 7/26
`(51)
`(52) U.S. CI. ........................ 370/252; 370/336; 455/423
`(58) Field of Search ................................. 370/252, 332,
`370/336, 345; 455/423, 522
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,883,899 A
`6,694,135 B1 *
`2001/0008521 A1 *
`2002/0006119 A1 *
`2003/0026235 A1 *
`2003/0103473 A1 *
`
`3/1999 Dahlman et al. " ......... 370/468
`2/2004 Oksala et al. ... '" ......... 455/424
`7/2001 Virtanen ..................... 370/331
`1/2002 Steudle. '" ........ '" ........ 370/329
`............ 370/342
`2/2003 Vayanos et al.
`.............. 370/318
`6/2003 Warich et al.
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`1020999 A1
`
`7/2000
`
`OTHER PUBLICATIONS
`
`"RRC Connection Mobility", 3G TR 25.922, version 3.0.0.,
`chapter 5, relevant pages.
`* cited by examiner
`
`Primary Examiner-Melvin Marcelo
`(74) Attorney, Agent, or Firm-Perman & Green, LLP
`(57)
`
`ABSTRACT
`
`A method for defining measurement gaps in a wireless
`telecommunications system comprising at least one base
`station and several wireless terminals. The telecommunica(cid:173)
`tions system comprises defining measurement patterns for
`terminals, which measurement patterns set locations of gaps
`used for measurements in a time-slot frame, and the base
`station comprises a transmitter for transmitting the measure(cid:173)
`ment patterns to the corresponding terminals. In the method,
`measurement patterns are defined for the terminals, setting
`the locations of the gaps used for measurements in a
`time-slot frame, the measurement patterns are transmitted
`through the base station to the corresponding terminals and
`various delays are defined for the measurement patterns of
`the terminals so that the gaps of different terminals are in
`substantially different locations in the time-slot frame.
`
`15 Claims, 5 Drawing Sheets
`
`parametres not optimised
`1
`4
`2
`3
`1
`1
`1
`1
`4
`4
`4
`4
`7
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`7
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`1
`2
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`1
`4 -10 4 -10 4 -10 4 ·10
`. -
`
`4 -10 4 -10
`
`-
`
`UE number
`CFN (frame no.)
`iGSN (slot no.)·
`rTGL 1 (slots)
`TGPL 1/2 (frames)
`~rame 1
`Kgap: slot - slot}
`~rame 2
`{gap: slot - slot}
`Iframe 3
`(aap: slot - slot)
`
`4 -10 4 -10 4 -10 4 -10
`
`0-6 8 -14 .4-10
`
`parametres optimised
`2
`1
`4
`3
`1
`1
`2
`1
`0
`4
`8
`4
`7
`7
`7
`7
`1
`1
`2
`2
`0-6 8 -14. 4 -10
`
`0-6 8 -14
`
`-
`
`-
`4 -10
`-
`
`LG Electronics Ex. 1001
`
`LGE_0000001
`
`

`

`u.s. Patent
`
`Oct. 26, 2004
`
`Sheet 1 of 5
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`US 6,810,019 B2
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`LGE_0000003
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`

`

`u.s. Patent
`
`Oct. 26, 2004
`
`Sheet 3 of 5
`
`US 6,810,019 B2
`
`#5
`TGP1
`
`Transmission
`1----'.. gap r-r - - - - - - ,
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`Fig. 4A (Prior Art)
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`Pattern9
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`Fig. 48 (Prior Art)
`
`LGE_0000004
`
`

`

`u.s. Patent
`
`Oct. 26, 2004
`
`Sheet 4 of 5
`
`US 6,810,019 B2
`
`parametres not optimised
`4
`1
`3
`2
`1
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`1
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`
`UE number
`CFN (frame no.) .
`ITGSN (slot no.)
`[TGL 1 (slots)
`rTGPL 1/2 (frames)
`~rame 1
`KQap: sial - slot)
`If'rame 2
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`Iframe 3
`(gap: slot - slot)
`
`Fig. 5
`
`parametres optimised
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`
`-
`4 -10
`-
`
`LGE_0000005
`
`

`

`u.s. Patent
`
`Oct. 26, 2004
`
`Sheet 5 of 5
`
`US 6,810,019 B2
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`LGE_0000006
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`

`

`US 6,810,019 B2
`
`1
`REDUCING INTERFERENCE IN INTER(cid:173)
`FREQUENCY MEASUREMENT
`
`BACKGROUND OF THE INVENTION
`
`5
`
`1. Field of the Invention
`The invention relates to measuring inter-frequencies in a
`mobile telephone system employing frequency division
`duplex (FFD) and especially to optimising said measure(cid:173)
`ments with respect to the total output in a system employing
`code division multiple access (CDMA).
`2. Brief Description of Related Developments
`Third-generation mobile telephone systems called UMTS
`(Universal Mobile Telephone System) and IMT-2000
`(International Mobile Telephone System), for instance, will
`use wideband code division multiple access technology, i.e.
`WCDMA technology, on the radio path. In a WCDMA
`system, all mobile stations in a cell use the same frequency
`between each other on the transmission link from the mobile
`station to the base station and correspondingly, the same
`frequency between each other on the transmission link from
`the base station to the mobile station. A WCDMAsystem can
`in mobile telephone systems be implemented either as
`frequency division duplex (FDD) or time division duplex
`(TDD).
`In an FDD-type WCDMA system, the uplink direction
`(from the mobile station to the base station) and the down(cid:173)
`link direction (from the base station to the mobile station)
`transmissions are independent of each other. Thus, the base
`stations need not be synchronized with respect to each other,
`either. It is, however, typical of CDMA systems that a
`downlink transmission is performed simultaneously from
`several base stations to one mobile station, which transmis(cid:173)
`sion the receiver of the mobile station is arranged to receive.
`This arrangement is called a soft handover, and to control it,
`the mobile station must perform various parameter measure- 35
`ments for both uplink and downlink connections. Corre(cid:173)
`sponding measurements are also used in updating the loca(cid:173)
`tion of a mobile station and in handovers between WCDMA
`and GSM systems.
`The receiver of a mobile station is typically arranged to 40
`receive only one frequency at a time, which means that one
`set of receiving means is enough for the mobile station and
`there is no need to design antenna diversity to them, which
`is advantageous both in view of cost and making the
`structure of the mobile station simple. The mobile station 45
`can also be designed to comprise several receiving means
`(dual receiver), which usually include antenna diversity.
`This type of mobile station is, however, more expensive and
`complex to implement.
`Thus, the parameter measurements described above can
`be performed in a typical one-receiver mobile station only
`when there is no transmission. This also applies to dual(cid:173)
`receiver mobile stations when one set of transmission/
`reception means transmits on almost the same frequency as
`a second set of transmission/reception means performs mea(cid:173)
`surements. In an FDD-type WCDMA system, the transmis(cid:173)
`sion is interrupted for a while by generating in a frame a gap
`during which transmission is interrupted. This is done by
`using what is known as compressed mode or slotted mode in
`which information normally transmitted in a lO-ms frame is
`transmitted in a shorter time. Since the same information is
`transmitted in a shorter time, a gap remains in the frame,
`during which measurements of the parameters described
`above can then be performed. Depending on the measure(cid:173)
`ment situation and the transmitter properties, compressed
`mode is only used in uplink or downlink transmissions, or a
`combined uplink/downlink compressed mode can also be
`used.
`
`15
`
`2
`In CDMA systems, all mobile stations connected to a
`certain cell typically use the same frequency bands in uplink
`and downlink transmissions, which means that the transmis(cid:173)
`sions of various mobile stations and base stations cause
`interference to each other. In addition, due to the signal
`propagation mechanism, signals transmitted from a mobile
`station close to a base station arrive at the base station
`stronger than those transmitted with the same power but
`further away from the base station, i.e. what is known as a
`near-far effect takes place. To maximize the capacity of a
`10 CDMA system in relation to the radio interface, it is essen(cid:173)
`tial that signals arriving at the base station have substantially
`the same average power, i.e. signal-to-interference ratio
`(SIR). Owing to this, CDMAsystems are characterized by a
`fast but complex transmission power control method.
`In the compressed mode described above, a certain
`amount of data to be transmitted is compressed to be
`transmitted in a shorter time, in which case the transmission
`power must be momentarily increased to maintain a constant
`signal-to-interference ratio. Increasing the transmission
`power then also causes interference to the transmissions of
`20 mobile stations in the same cell, and they, too, need to
`increase their transmission power to compensate for the
`interference.
`A problem with the above arrangement is that the present
`WCDMA system does not define where in a time division
`25 frame compressed mode is used, in other words, where in the
`frame a gap is generated for measuring parameters. Thus, the
`gaps may randomly fall anywhere in the frame. If in several
`mobile stations, the gap falls into substantially the same
`place, the compressed places in which transmission power
`30 has been increased, also overlap at least partly. The total
`interference in the system then increases and the average
`transmission power of the mobile stations must be increased.
`Further, increasing the transmission power may cause an
`uncontrolled state in which all mobile stations increase their
`transmission power to its maximum, whereby the capacity
`limit of the system is reached and the quality of the trans(cid:173)
`missions decreases. Because the base station, too, typically
`transmits at the same frequency as the mobile stations, the
`downlink direction transmission power must also be
`increased.
`
`SUMMARY OF THE INVENTION
`In one embodiment, the present invention is directed to a
`method for defining measurement gaps in a wireless tele(cid:173)
`communications system comprising one base station and
`several wireless terminals, the method comprising: defining
`for the terminals in said telecommunications system mea-
`surement patterns which define locations of gaps used for
`measurements in a time-slot frame, and sending the mea(cid:173)
`surement patterns to the corresponding terminals through the
`50 base station. The method is characterized in that various
`delays are defined for the measurement patterns of said
`terminals so that the gaps of different terminals are in
`substantially different locations in the time-slot frame.
`The invention also relates to a wireless telecommunica-
`55 tions system comprising a fixed network, at least one base
`station and several wireless terminals and means for defining
`measurement patterns for terminals, which measurement
`patterns define locations of gaps used in measurements in a
`time-slot frame and which base station comprises a trans(cid:173)
`mitter for transmitting the measurement patterns to the
`60 corresponding terminals. The telecommunications system is
`characterized in that said means for defining measurement
`patterns are arranged to define various delays for said
`terminal measurement patterns so that the gaps of different
`terminals are in substantially different locations in the time-
`65 slot frame.
`The invention further relates to a terminal in a wireless
`telecommunications system, which terminal comprises a
`
`LGE_0000007
`
`

`

`US 6,810,019 B2
`
`3
`receiver for recelvmg measurement pattern definitions
`defined by the telecommunications system and processing
`means for arranging gaps in a time-slot frame according to
`the measurement pattern definitions, and which is charac(cid:173)
`terized in that said processing means are also arranged to set
`for the measurement pattern a delay according to the mea(cid:173)
`surement pattern definitions.
`The invention also relates to a base station in a wireless
`telecommunications system, to which base station means are
`operationally connected for defining measurement patterns 10
`for terminals, which measurement patterns define locations
`of gaps used in measurements in the time-slot frame and
`which base station comprises a transmitter for transmitting
`the measurement patterns to the terminals. The base station
`is characterized in that said means for defining measurement
`patterns operationally connected to said base station are
`arranged to define various delays for said terminal measure(cid:173)
`ment patterns so that the gaps of different terminals are in
`substantially different locations in the time-slot frame.
`The invention is based on the idea that to make
`measurements, especially those performed in compressed
`mode, non-simultaneous, at least partly different delays are
`set for the measurement patterns defining the measurement
`gaps of each mobile station, whereby time-slots also trans(cid:173)
`mitted in compressed mode at a higher data rate are distrib(cid:173)
`uted more evenly to various mobile stations in relation to the
`time-slot frame.
`The method and system of the invention provides the
`advantage that by optimizing the distribution of the mea(cid:173)
`surement gaps between various mobile stations, the inter(cid:173)
`ference caused by mobile stations to each other at a higher
`transmission power is reduced. This provides the further
`advantage that the average transmission power of the system
`remains low, thus improving the capacity of the system.
`
`BRIEF DESCRIPTION OF THE FIGURES
`
`In the following, the invention will be described in greater
`detail by means of preferred embodiments and with refer(cid:173)
`ence to the attached drawings, in which
`FIG. 1 shows the structure of an UMTS mobile telephone
`system in a simplified block diagram,
`FIG. 2 shows a frame structure used on the radio link of
`a WCDMA system,
`FIG. 3 illustrates some parameters used in defining com(cid:173)
`pressed mode,
`FIGS. 4a and 4b show some measurement pattern defi(cid:173)
`nitions according to prior art,
`FIG. 5 shows a comparison between prior art measure(cid:173)
`ment pattern definitions and those of the invention in a table,
`and
`FIG. 6 shows the structure of a radio system and mobile 50
`station of the invention.
`
`4
`ous to a person skilled in the art that a conventional mobile
`telephone system also comprises other functions and
`structures, which need not be described in greater detail
`herein. The main parts of a mobile telephone system are a
`5 core network CN, a UMTS mobile telephone system terres(cid:173)
`trial radio access network UTRAN, and a mobile station or
`user equipment UE. The interface between CN and UTRAN
`is referred to as lu and the air interface between UTRAN and
`UE is referred to as Uu.
`UTRAN typically comprises radio network subsystems
`RNS, the interface between the RNSs being referred to as lur
`(not shown). A radio network subsystem RNS comprises a
`radio network controller RNC and one or more nodes B. The
`interface between RNC and B is referred to as lub. The
`15 service area, i.e. cell, of node B is indicated with C in FIG.
`1.
`
`The user equipment UE can, for instance, be a fixed or a
`portable terminal or one installed in a vehicle. The infra(cid:173)
`structure UTRAN of the radio network comprises radio
`network subsystems RNS, i.e. base station systems. The
`20 radio network subsystem RNS comprises a radio network
`controller RNC, i.e. a base station controller, and at least one
`node B, i.e. base station, under its control.
`The base station B has a multiplexer 114, transceivers 116
`and a control unit 118 which controls the operation of the
`25 transceivers 116 and the multiplexer 114. With the multi(cid:173)
`plexer 114, the traffic and control channels used by several
`transceivers 116 are placed in the transmission link lub.
`The transceivers 116 of the base station B are connected
`to an antenna unit 120 with which a bi-directional radio link
`30 Uu is implemented to the user equipment UE. The structure
`of the frames being transmitted over the bi-directional radio
`link Uu is clearly specified.
`The radio network controller RNC comprises a group
`switching field 110 and a control unit 112. The group
`35 switching field 110 is used for speech and data connection
`and to connect signalling circuits. The base station system
`formed by the base station B and the radio network con(cid:173)
`troller RNC also comprises a transcoder 108. Distribution of
`tasks between the radio network controller RNC and the
`40 base station B as well as their physical structure can vary
`depending on implementation. Typically, the base station B
`takes care of the radio path implementation as described
`above. The radio network controller RNC typically takes
`care of the following: management of radio resources,
`45 control of handover between cells, power adjustment, timing
`and synchronization, paging the subscriber terminal.
`The transcoder 108 is usually located as close as possible
`to a mobile switching centre 106, because speech can then
`be transmitted in mobile telephone system format between
`the transcoder 108 and the radio network controller RNC,
`saving transmission capacity. The transcoder 108 converts
`the different digital coding formats of speech used between
`the public switched telephone network and the mobile
`telephone network to be compatible with each other, for
`instance from the 64 kbit/s format of a public network to
`55 another (e.g. 13 kbit/s) format of a cellular network and vice
`versa. The hardware required is not described in detail
`herein, but it should be noted that other data than speech is
`not converted in the transcoder 108. The control unit 112
`takes care of call control, mobility management, collection
`60 of statistics, and signalling.
`The core network CN comprises an infrastructure belong(cid:173)
`ing to a mobile telephone system and external to UTRAN.
`FIG. 1 describes two of the components in a core network
`CN, i.e. a mobile switching centre 106 and a gateway mobile
`switching centre 104 which handles the connections of the
`mobile telephone system to the outside world, such as to a
`public analogue telephone network (PSTN, public switched
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The invention can be used in all wireless telecommuni(cid:173)
`cations systems needing total transmission power control on
`the uplink transmission path, especially for distributing
`uplink transmissions and interference of terminals evenly in
`relation to time. The method of the invention can also be
`applied to decreasing the transmission power of a downlink
`transmission path. The examples describe the use of the
`invention in a universal mobile telephone system employing
`wideband code division multiple access, without, however,
`limiting the invention to it.
`The structure of an UMTS mobile telephone system is 65
`described with reference to FIG. 1. FIG. 1 only contains the
`blocks essential for explaining the invention, but it is obvi-
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`US 6,810,019 B2
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`5
`telephone network) 101 or a digital telephone network
`(ISDN, integrated services digital network) 102 or to the
`Internet 103. It should be noted that the UMTS system is
`designed so that the core network CN can be identical with
`that of the GSM system, thus making it unnecessary to 5
`rebuild the entire network infrastructure.
`FIG. 2 shows the frame structure of an FDD-type
`WCDMA system in a physical channel. Frames 240A,
`240B, 240C, 240D are numbered sequentially from 1 to 72,
`and they form a 720-millisecond long super frame. The
`length of this super frame is a multiple of the multi-frame of 10
`the GSM system (6x120 ms) which, for its part, makes it
`possible to use the GSM core network in a WCDMAsystem.
`The length of one frame 240 is 10 milliseconds. Frame 240
`is divided into fifteen (0 to 14) slots 230A, 230B, 230C,
`230D. The length of one slot 230C is 2560 chips, i.e. 0.666 15
`milliseconds. One slot 230 typically corresponds to one
`power adjustment period during which power is adjusted
`one decibel up or down, for instance.
`Physical channels are divided into two groups: common
`physical channels and dedicated physical channels.
`The following transport channels are transmitted in the 20
`common physical channels: PCH (paging channel), BCH
`(broadcast channel, RACH (random access channel) and
`FACH (forward access channel).
`Dedicated physical channels comprise dedicated physical
`data channels (DPDCH) 210 and dedicated physical control 25
`channels (DPCCH) 212. Dedicated physical data channels
`210 are used to transmit dedicated control channels, i.e. data
`200 which is generated on the second layer of OSI (Open
`Systems Interconnection) and above. Dedicated physical
`control channels 212 transmit control information generated 30
`on the first layer of OS!. Control information comprises at
`least pilot bits 208 used in channel estimation, feedback
`information (FBI) 204, transmit power control commands
`(TPC) 206, and optionally a transport format combination
`indicator (TFCI) 202. The transport format combination
`indicator 202 indicates to the receiver the transmission 35
`formats of the different transport channels, i.e. the transport
`format combination, used in the frame in question.
`As shown in FIG. 2, on the downlink, the dedicated
`physical data channels 210 and the dedicated physical
`control channels 212 are time-multiplexed to the same slot 40
`230C. However, on the uplink, the channels in question are
`transmitted parallel so that they are I Q/code-multiplexed to
`each frame 240C.
`FIG. 3 shows parameters relevant to the invention, which
`are used in defining compressed mode in an FDD-type
`WCDMA system. A connection frame number (CFN)
`defines the number of the time division frame in which the
`application of the compressed mode is started. In other
`words, CFN defines the frame into whose time-slot(s) a gap
`is left for measuring inter-frequency parameters. A trans- 50
`mission gap starting slot number (TGSN) defines the time(cid:173)
`slot of the 15 time-slots in the frame in question, from which
`the gap starts. Transmission gap length 1/2 (TGL1/2) defines
`how long the gap is as a number of time-slots, in other
`words, it defines the length of time during which transmis(cid:173)
`sion is interrupted at one time. Transmission gap distance
`(TGD) is the distance between two consecutive gaps indi(cid:173)
`cated as a number of time-slots. Transmission gap pattern
`length 1/2 (TGPLI/2) defines the number of consecutive
`frames which comprise one or two gaps. Sequences of
`transmission gap pattern lengths are repeated until the
`required measurement has been made. The total time of
`measurement is defined as a transmission gap period rep(cid:173)
`etition count (TGPRC), which is indicated as a number of
`frames and typically comprises several gap patterns. It
`should be noted that other parameters, too, are used in 65
`compressed mode definition, but a more detailed description
`of them is not essential for the invention.
`
`6
`The performance of the measurements is typically defined
`by means of the parameters TGLI/2, TGPL1/2, TGD and
`TGPRC. The parameters CFN and TGSN are used in some
`measurements to only define the delay to be used, which is
`typically a measurement pattern-specific constant value for
`all mobile stations. For instance, for an internal (inter(cid:173)
`frequency) handover of a WCDMA system, the fixed net(cid:173)
`work UTRAN requests user equipment UE to perform
`inter-frequency parameter measurements. The fixed network
`UTRAN then signals to the user equipment UE monitoring
`settings for the handover and the compressed mode param(cid:173)
`eters to be used for the required measurements. In the
`preparations for an internal (inter-frequency) WCDMA sys(cid:173)
`tem handover, compressed mode can further be divided into
`two operational modes, selection mode and re-selection
`mode. During selection mode, the user equipment UE must
`identify the cell to which the handover will be made. During
`re-selection mode, the user equipment UE measures the
`strength of the signal transmitted by the base station BTS of
`said cell.
`The tables in FIGS. 4a and 4b show some compressed
`mode measurement parameters signalled by the fixed net(cid:173)
`work UTRAN to the user equipment UE for the selection
`mode and correspondingly, for the re-selection mode. For
`the selection mode measurements, FIG. 4a shows seven
`alternative measurement patterns of which the fixed network
`UTRAN then selects one and signals it to the user equipment
`UE to define the measurements of the parameters. The
`measurement pattern used at each time is selected on the
`basis of the measurement to be performed, in other words,
`what different measurements the mobile station should per(cid:173)
`form. The user equipment UE performs measurements dur-
`ing gaps whose length (TGL1) is either 7 or 14 time-slots
`and on the basis of the measurements, the user equipment
`UE reports to the fixed network for instance the timing of the
`frame, the scrambling code used and the chip energy (Ejlo)
`of the primary common control physical channel (CCPCH)
`in the downlink direction. As shown in FIG. 4a, the mea-
`surement parameters TGL1, TGD and TGPL1 of measure(cid:173)
`ment patterns 1 and 2, also 3, 4 and 5, and 6 and 7 are similar
`to each other. When allocating measurement patterns to
`several mobile stations, it is then probable that the gaps fall
`on several mobile stations at least partly simultaneously.
`Then the compressed parts, too, whose transmission power
`has been increased, overlap at least partly, which results in
`an increase in the total interference and in increasing the
`45 average transmission power of the mobile stations. The user
`equipment UE uses the gap period parameters TGPL1 and
`TGPL2 one after the other, but even then the gaps overlap
`at least partly in the measurement patterns 1 and 4, and 2 and
`5, for instance.
`The re-selection mode measurement patterns 8 and 9
`described in FIG. 4b are used when the user equipment UE
`knows the scrambling code used in the new cell. Again, the
`fixed network UTRAN allocates either of the measurement
`patterns 8 or 9 to the user equipment UE depending on the
`55 situation. Since there are only two alternatives and since the
`measurement pattern 9 definitions are multiples of the
`measurement pattern 8 (2x72=144), whereby every second
`gap falls in the same place with respect to the measurement
`patterns 8 and 9, it is again highly probable that the gaps
`defined for mobile stations in the same cell overlap at least
`60 partly.
`The above describes measurements performed for an
`internal (inter-frequency) WCDMAsystem handover as one
`example of a parameter measurement typical of the
`WCDMA system in compressed mode. It should be noted
`that the 3GPP specification also defines in a corresponding
`manner other parameter measurements in compressed mode,
`in which problems described above are also encountered.
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`US 6,810,019 B2
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`7
`For a more detailed description of these measurements,
`reference is made to the document 3G TR 25.922, version
`3.0.0., chapter 5, "RRC Connection Mobility".
`In the following, a preferred embodiment of the invention
`is described by means of an example and with reference to 5
`FIG. 5. As stated above, the parameters CFN and TGSN are
`not typically used in defining measurements performed in
`compressed mode other than by setting the same measure(cid:173)
`ment delay for all mobile stations of a cell. The fixed
`network VTRAN, however, signals the parameters CFN and 10
`TGSN to the user equipment VE in any case, since they are
`needed in forming the radio link frame structure. This makes
`possible the use of said parameters for minimising interfer(cid:173)
`ence without extra signalling. Instead of setting the same
`delay for all mobile stations VE, the fixed network VTRAN
`can preferably allocate different values for the parameters 15
`CFN and TGSN for each mobile station within the limits
`defined by a maximum delay. Then the parameter TGSN,
`which defines the time-slot from which the gap starts, can,
`depending on the measurement pattern, preferably obtain
`values 0 to 14 covering all time-slots in the time-slot frame. 20
`The parameter CFN, which defines the frame from which the
`gap starts, can preferably also vary within the scope of the
`maximum delay defined for the system. The allocation of the
`parameters CFN and TGSN for mobile stations can be
`optimised so that in compressed mode the time-slots trans- 25
`mitted at a higher data rate are distributed as evenly as
`possible to different mobile stations. Then the average
`transmission power and the interference among the mobile
`stations can preferably be kept as low as possible, thus
`improving the output and capacity of the system.
`The table in FIG. 5 shows by way of example the defining
`of measurement parameters for four mobile stations both
`according to prior art, in which the parameters are not
`optimised (table on the left), and according to the invention,
`in which the parameters are optimised especially by means 35
`of the parameters CFN and TGSN (table on the right). In the
`table on the left, the same delay is defined according to prior
`art to user equipment (VE number) VEl, VE2, VE3 and
`VE4 by giving the parameters CFN and TGSN of each
`m