US005831974A
`5,831,974
`(114) Patent Number:
`United States Patent 55
`Suonvieri
`[45] Date of Patent:
`Nov. 3, 1998
`
`
`[54] TESTING EQUIPMENTFORA BASE
`STATION NETWORK
`
`[75]
`
`Inventor:
`
`Jukka Suonvieri, Tampere, Finland
`
`[73]
`
`aSlOaovyWdCnNY&EeSSae
`
`Assignee: Nokia Telecommunications Oy, Espoo,
`Finland
`
`Appl. No.:
`
`676,252
`
`PCTFiled:
`
`Nov.20, 1995
`
`PCT No.:
`
`PCT/FI95/00639
`
`§ 371 Date:
`
`Sep. 20, 1996
`
`§ 102(e) Date: Sep. 20, 1996
`
`[87]
`
`PCT Pub. No.: WO96/16522
`
`PCT Pub. Date: May 30, 1996
`
`[30]
`
`Foreign Application Priority Data
`
`Nov. 21,1994
`
`[FI]
`
`Finland oer 945468
`
`Int. Cho cece H04Q 7/34; HO4B 17/00
`US. C1. cece 370/252; 370/337; 370/347;
`370/350; 455/67.4
`Field of Search o....c.cccccccceeeeee 370/313, 314,
`370/328, 336, 337, 345, 347, 252, 246,
`350, 519, 249; 455/67.8, 226.1, 423, 456,
`517, 508, 67.4, 524, 67.1
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,350,644 10/1967 MECNAIr ounce ceeceeten ce ceeeeneee 370/356
`5,278,832
`1/1994 Binzel et al. wee eeeee 370/347
`
`5,363,375
`11/1994 Chuanget al. veces 370/332
`
`5,471,649
`we 455/67.4
`11/1995 Reesetal. ..
` 5,544,171
`5,483,537
`1/1996 DUpUY veccccsscsceccssseteseessseeeesens 370/337
`8/1996 Godecker....
`« 370/337
`8/1997 Kohlschmidt 0.0 eens 370/337
`5,654,960
`FOREIGN PATENT DOCUMENTS
`
`12/1994 European Pat. Off.
`630 125
`2 277 232 10/1994 United Kingdom .
`91/15904 10/1991 WIPO.
`95/02306
`1/1995 WIPO.
`
`.
`
`Primary Examiner—Douglas W. Olms
`Assistant Examiner—Seema S. Rao
`
`Attorney, Agent, or Firm—1P Group of Pillsbury Madison &
`Sutro LLP
`
`[57]
`
`ABSTRACT
`
`A testing equipment for a base station in a time division
`multiple access radio system employing timing advance is
`located at one base station site under control of a respective
`base station to perform test procedures on basestations. The
`testing equipment simulates the operation of a normal
`mobile station on the radio path,
`in test procedures. In
`contract to known systems, in which the maximum distance
`between the testing equipmentand a basestationto be tested
`is determined by the maximum value of a timing advance,
`the present
`testing equipment provides a preset
`timing
`advance offset (TDor¢s¢7), Which shifts the normal timing
`advance range (TDyoragaz) in such a mannerthatthe testing
`equipmentis also capable of testing base stations the dis-
`tance of which from the testing equipments is further than
`the maximum distance that would be determined by the
`maximum value of a normal timing advance.
`
`11 Claims, 3 Drawing Sheets
`
`
`LONG-DISTANCE AREA
`
`
`
`LOCAL AREA
`BTS1O
`
`
`
`
`
`FRAME.
`1
`FRAME 2
`
`
`TS0[7S1 |TS2 |7S3}TS4 |TS5 |7S6 [787 so [rsa | ts2 |...
`
`Ry
`
`|ers--st4
`
`OFFSET OF 3 TIMESLOTS
`|
`
`benl I
`pt
`PRESET
`4
`i
`TI
`TIMING ADVANCE
`te
`|
`|_11S5]7S6| 187 [750151 [TS2]7s3|TS4 [135 [786 [157] ... smears
`Pua
`1!
`NORMAL
`TIMING ADVANCE i
`TOTAL
`)
`-
`TIMING ADVANCE
`
`1
`
`APPLE 1011
`
`1
`
`APPLE 1011
`
`

`

`U.S. Patent
`
`Sheet 1 of 3
`
`Nov. 3, 1998
`
`5,831,974
`
`
`
`
`
`DUPLEX
`
`CTRL
`
`ANT
`
`2
`
`

`

`U.S. Patent
`
`Nov. 3, 1998
`
`Sheet 2 of 3
`
`5,831,974
`
`
`
`
`LONG-DISTANCE AREA
`
`LOCAL AREA
`
`
`
`BTS1
`()
`
`FIG. 2
`
`3
`
`

`

`U.S. Patent
`
`Nov. 3, 1998
`
`Sheet 3 of 3
`
`5,831,974
`
`
`
`TSO) TS1|TS2]TS3)TS4}TS5|TS6|TS7|TSO}TS1] TS2|... |BTS-STM
`
`FRAME 1
`
`FRAME 2
`
`Rx
`
`| OFFSET OF 3 TIMESLOTS
`
`||
`
`||
`
`tx
`
`
`
`
`
`TS5|TS6 |TS7 {TSO |TS1|TS2 |TS3|TS4 |TS5|TS61TS7 |... |STM-~BTS
`
`etbeg
`TIMING ADVANCE
`
`FIG. 3
`
` FRAME 1
`
`FRAME 2
`
`Ry
`
`OFFSET OF 3 TIMESLOTS
`btm
`
`PRESET
`
`| 1
`
`|
`
`ix
`TIMING ADVANCE
`I
`
`
`|_17S5|7S6| 787|TS0|TS1 |TS2|7S3 |TS4 |7S5|TS6|157]... |STM—BTS
`
`!
`,
`1
`tu
`NORMAL
`—ye}eg|
`TIMING ADVANCE '
`1
`TOTAL
`|
`1
`TIMING ADVANCE
`;
`|
`
`FIG. 4
`
`4
`
`

`

`5,831,974
`
`1
`TESTING EQUIPMENT FOR A BASE
`STATION NETWORK
`
`This application claim benefit of international applica-
`tion PCT F195/00639, filed Nov. 20, 1995
`
`FILED OF THE INVENTION
`
`The present invention relates to a testing equipmentfor a
`base station network in a time division multiple access
`(TDMA)radio system employing timing advance control, in
`which a maximum value defined for a timing advance
`determines a maximum distance betweena base station and
`a mobilestation, this testing equipment being located at one
`base station site under control of the respective base station
`to perform test procedures on base stations,
`the testing
`equipment simulating the operation of a normal mobile
`station on the radio path during the test procedures.
`BACKGROUND OF INVENTION
`
`In radio systems, for instance in cellular systems, one of
`the most crucial factorsis the quality of the radio connection
`between a base station and a mobile radio station. The
`
`quality of this radio connection is essentially affected by the
`condition of the radio sections,
`i.c.
`the antennas and
`transceivers, of the base station. Therefore, it is important
`that the condition of a base station can be monitored by
`meansof different measurements andtests.
`
`In a known solution, a base station is provided with a
`testing equipment with a dedicated antenna and a transceiver
`so that it is capable of establishing a connection with the
`base station over the radio path, like a normal subscriber
`station. In addition, the testing equipment is provided with
`necessary measuring equipment for performing desired test
`measurements and test calls on the base station. A testing
`equipmentlocated at one base station site can also be used
`for measuring neighboring base stations, whereby a dedi-
`cated testing equipment for each base station is avoided.
`In digital time division multiple access (TDMA) radio
`systems, a number of mobile radio stations can use the same
`carrier wave (radio channel) on the time division principle
`for communicating with a base station. The carrier wave is
`divided into successively recurring frames, which are
`divided further into time slots, for instance into eight time
`slots, which are allocated to users as the need arises. Short
`data bursts are transmitted in the time slots. A mobile radio
`station synchronizes with a signal arriving from the base
`station and transmits a burst in accordance with this syn-
`chronization signal (or “sync”) in such a manner that the
`burst of the mobile station is received at the base station in
`
`a timeslotallocated to this specific mobile station. However,
`mobile stations may be located at different distances from
`the base station, it being thus necessary to synchronize the
`transmission moment of each mobile station with the base
`
`station, taking into account the propagation delay dueto this
`distance in such a mannerthat the signal from each mobile
`station, regardless of its distance from the base station, is
`received in the correct timeslot at the base station. In order
`to do this,
`the base station measures the time difference
`between its own transmission and the transmission received
`from a mobile station and determines a suitable timing
`advance for the mobile station on this basis. By meansofthis
`timing advance, the mobile station advances the transmis-
`sion momentin relation to the basic momentprovided by the
`sync obtained from the base station. Different factors inter-
`nal to the system restrict the highest possible timing advance
`to a certain maximum value. This maximum valueof timing
`
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`advance then determines the largest cell size that a base
`station of the system is able to serve. For instance in the
`pan-European mobile communication system GSM (Global
`System for Mobile Communication), timing advance may be
`given values within a range of 0-233 us, which is equivalent
`to the size of a cell with a radius of 35 km at the most.
`
`This restriction due to timing advance also leads to the
`fact that a testing equipmentlocated at one basestationsite
`cannot be used for testing neighboring base stations which
`are located at an excessive distance from the testing
`equipment,
`for
`instance at a distance of over 35 km.
`However, since the antennas of both a base station to be
`tested and the testing equipment are usually located at
`relatively elevated sites in a high place in terrain, overlong
`radio connections are in most cases possible as regards the
`coverage, ie. the attenuation of the radio path and natural
`obstacles.
`
`SUMMARYOF THE INVENTION
`
`The object of the present invention is to provide a testing
`equipment for a base station network, which can also be
`used for testing base stations located at a distance longer
`than the maximum distance determined by timing advance.
`This is achieved with the testing equipment for a base
`station network according to the invention, characterized in
`that the testing equipment comprises a preset timing advance
`offset, which shifts the normal
`timing advance range
`upwards in such a mannerthat the testing equipmentis also
`capable of testing base stations the distance of which from
`the testing equipmentis longer than the maximum distance
`which equates to a maximum normaltiming advance.
`The testing equipment of the invention employs a preset
`timing advanceoffset for measuring base stations located at
`overlong distances. To putit differently, an additional timing
`advance offset is preset in the transmission of the testing
`equipment, this timing advance offset increasing the timing
`advance in such a mannerthat the distance of a base station
`
`to be tested is compensated for even if it is located at an
`overlong distance from the testing equipment. Above the
`preset timing advance offset value, the timing advance can
`be adjusted within a normal range according to the control
`of a tested base station. In other words, the base station to be
`tested measures the distance of the testing equipment in a
`normal manner and adjusts the testing equipment to use a
`suitable timing advance value on this basis. Therefore, the
`selection of a preset timing advance offset does not need to
`be particularly accurate. The testing equipment modifies the
`timing advance command transmitted by the basestation to
`be tested by adding the assigned timing advanceto the preset
`timing advanceoffset. In an access burst, the testing equip-
`ment uses the preset timing advance offset value instead of
`the normal value 0. Preferably, the preset timing advance
`offset has the value 0 for the local area (for distances
`corresponding to a normalcell size) and one or more values
`deviating from zero for the long-distance area, ie.
`for
`overlong distances.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`In the following, the invention will be described in more
`detail by meansof the preferred embodiments of the inven-
`tion with reference to the accompanying drawings,in which:
`FIG. 1 showsthe radio system of the invention,
`FIG. 2 illustrates the establishment of the local area and
`the long-distance area of the base station network
`measurement,
`
`5
`
`5
`
`

`

`5,831,974
`
`3
`FIG. 3 illustrates the normal timing of the transmission
`and reception of the testing equipment in a local area,
`FIG. 4 illustrates the timing of the testing equipment
`according to the invention in a long-distance area, and
`FIG. 5 is a block diagram of the testing equipment of the
`invention.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENT OF THE INVENTION
`
`The present invention is intended to be applied in any
`radio network in which digital time division multiple access
`(TDMA)and timing advance are applied.
`FIG. 1 illustrates a radio system in which the testing
`equipment STM of the invention is connected by a fixed
`control link 11 to a base station BTS1 at a basestation site
`
`SITE1. In the radio system which the base station BTS1
`belongs to, the next higher-level network elementis a base
`station controller BSC, to which the base station BTS1 is
`connected by a fixed digital transmission link 12, such as a
`PCM link. The base station controller BSC is connected to
`a mobile exchange MSC bya digital transmission link 13
`and to an operation and maintenance center OMCcontrol-
`ling the operation of the entire system by a transmission link
`14. From the center OMC,the radio network operator can
`change different parameters of the network and control the
`operation of the network elements, such as the base stations
`BTS. In addition, base stations BTS2 and BTS3 are also
`connected to the base station controller BSC by digital
`transmission links.
`
`By meansof the testing equipment located at the base
`station site SITE1, it is possible to test both the base station
`BTS1 of said base station sitel and one or more neighboring
`base stations one or more of whichis orare located ata site
`thatis or sites that are geographically separated from SITE1.
`Providing each basestation of the base station network with
`a dedicated testing equipment can be avoided in this manner.
`By meansofthe testing equipment STM,it is possible, for
`instance, to establish test calls, make test calls via a desired
`base station, perform sensitivity and interference
`measurements, etc. Especially as regards test calls,
`the
`testing equipment STM must be capable of simulating the
`operation of a normal mobile station of the radio network on
`the radio path. The testing equipment can thus be imple-
`mented for instance with a conventional mobileradiostation
`equipment, which is provided with a link 11 to a basestation
`and the software of which is arranged to perform measure-
`ments and tests under control of that base station.
`
`FIG. 5 shows a simplified block diagram of a testing
`equipment STM of the invention,
`the testing equipment
`being located at a base station. The block diagram shows,for
`the sake of simplicity, only those parts of the testing equip-
`ment which are necessary for understanding the invention.
`The testing equipment comprises an antenna ANT,a duplex
`filter 51, a receiver 52, a transmitter 53, frame units 55 and
`56, and a control unit 57. The radio receiver 52 and the radio
`transmitter 53 contain all the radio frequency parts of the
`testing equipment STM. The frame units 55 and 56 contain
`all the baseband signal processing relating to reception and
`transmission,
`for instance channel coding,
`interleaving,
`burst establishment, etc. The control unit 57 controls the
`operation and timing of the testing equipment in such a
`mannerthat the testing equipment STM simulates perfectly
`the operation of a conventional mobile station on the radio
`path. The control unit 57 communicates with the base station
`BTS1 via the control link 11, receiving control commands
`and possibly transmitting measurement reports. The control
`
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`unit 57 also generatesall the signalsrelating to the timing of
`transmission and reception, synchronizes the transmission
`and reception and adjusts the necessary timing advance
`according to the preset of the invention and the timing
`advance value received from a basestation to be tested over
`the radio path.
`the timing advance area used in
`As explained above,
`TDMAsystems determines the maximum distance r,,,.
`between a base station BTS and a mobile station,
`this
`distance being about 35 km in the GSM system. In the
`present document, this normal cell size is referred to as the
`local area of the testing equipment. The area located beyond
`this maximum distancerexis referred to as the long-distance
`area of the testing equipment STM in this document. FIG. 2
`illustrates the local and long-distance areas of the testing
`equipment STM located at the base station BTS1. The base
`station BTS2 of FIG. 1 is thus located in the local area at a
`distance of 20 km from the testing equipment, and it can be
`tested by the testing equipment using a conventional timing
`advanceat the base station site SITE1. As for the basestation
`
`BTS3, it is located in the long-distance area at a distance of
`45 km from the testing equipment, and it cannot be tested
`with conventional means from the basestation site SITE1.
`
`Thus, another testing equipment has conventionally been
`needed at the base station BTS3 or in a sufficiently close
`proximity to it.
`FIG. 3 illustrates the timing of the transmission and
`reception of the testing equipment STM according to the
`specifications in testing operations taking place in the local
`area. Both the downlink carrier (BTS-STM)and the uplink
`carrier (STM-BTS)are divided into successively recurring
`frames, which are divided further into TDMAtimeslots, for
`instance into eight time slots TSO-TS7, which are allocated
`to users as the need arises. Short data bursts are transmitted
`in the time slots TS0-TS7. The STM synchronizesits uplink
`transmission Tx with the downlink signal received from the
`base station. The transmission Tx and the reception Rx of a
`conventional mobile station and of the testing equipment
`STM measuring a base station in the local area take place
`exactly as specified for the mobile station in such a manner
`that the STM transmits its own burstto the base station BTS
`with an offset OFFSETofthree time slots as compared with
`the moment when the STM receives a burst from the base
`station BTS (for instance time slot TSO) Since mobile
`stations may be located at different distances from the base
`station, the transmission moment of each mobile station is
`synchronized with the base station in radio systems, taking
`into account the propagation delay due to this distance in
`such a mannerthat the signal is received in the correct time
`slot at the base station. In order to do this, the base station
`BTS measuresthe time difference between its own downlink
`
`transmission and the uplink transmission received from a
`mobile station and determines a suitable timing advance
`Timing Advance for the mobile station on this basis. By
`means of this timing advance, the mobile station advances
`the transmission momentin the uplink direction in relation
`to the basic momentprovided by the sync obtained from the
`base station. If the STM tests the base station BTS1 of its
`own base station site SITE1, the distance is zero and the
`timing advance value is zero. If the STM tests the base
`station BTS2,the base station BTS2 detects this distance by
`measuring and provides the STM with a timing advance
`compensating for this distance, and the establishmentof the
`test call can be continued in the normal manner.
`
`The operation of the testing equipment is in accordance
`with what is described above when the testing equipment
`operates in a local measurement mode. For long-distance
`6
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`6
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`

`

`5,831,974
`
`5
`the STM can be adjusted to a long-
`area measurement,
`distance measurement mode by a command given from the
`base station BTS1 via the control connection 11.
`
`In the long-distance measurementstate, the STM is com-
`mandedto use a preset timing advance offset in addition to
`the normal timing advance. The preset timing advanceoffset
`shifts the lower limit of the normal timing advance range
`from zero to the mentioned preset timing advance offset
`value. Assumeas an example that the normal timing advance
`range is between 0 to 63. Also assumethat a value 30 of the
`preset timing advance offset is used in the long-distance
`measurementstate. The timing advance can thus be adjusted
`within a range of 30 to 93, which may correspond to
`distances within a range of 15 to 60 km,for instance.
`The timing of the reception Rx and transmission Tx of the
`testing equipment STM ofthe invention in the long-distance
`measurement modeis illustrated in FIG. 4 To measure a base
`station BTS,
`the base station BTS1 adjusts the testing
`equipment STM to a long-distance measurementstate,
`where the STM usesa preset timing advanceoffset TDegser
`At the beginningofthe test call, irrespective of whetherit is
`a question of testing a mobile originating call or a mobile
`terminating call, the STM transmits an access burst to the
`base station BTS on the random access channel RACH,the
`timing advance offset value TD,»,., being used in this access
`burst instead of the value 0. The base station BTS receives
`the access burst and determines the distance between the
`base station and the testing equipment STM in the normal
`manner. In this determination, the base station BTS assumes,
`however, that the STM has used the normal timing advance
`O in the transmission of the access burst. The BTS thus
`
`estimates the distance of the testing equipment STM to be
`shorter by the distance according to the preset
`timing
`advance offset TD,,., than the actual distance is. The BTS
`then provides the testing equipment STM, by means of
`downlink signalling, with the normal timing advance value
`TD,oral Colresponding to the estimated shorter distance.
`The STM modifies the normal timing advance value TD,,,,-
`mai obtained from the base station BTS by adding the preset
`timing advance offset value TD,»,., thereto so that the total
`timing advance is TD797=TDorrse7+TDnormat:
`Assume, for instance, that TDoprs-7=30. The STM uses
`the timing advance value 30 in the access burst it transmits
`to the base station BTS2. The base station BTS2 providesthe
`testing equipment STM with a timing advance TDyoraar=
`10. The STM thus uses the value TD,57=30+10=40 as the
`connection continues. In this example,
`the preset timing
`advance offset was actually not even necessary, a semicolon
`the normal timing advance area would have been sufficient.
`The base station BTS2 would thus have actually adjusted, on
`the basis of the measurementcarried out by it, the testing
`equipment STM to directly use the value 40.
`As another example, assume that TDorps¢-7=30, but the
`STM transmits an access burst to the base station BTS3. The
`base station BTS3 providesthe testing equipment STM with
`the normal timing advance value TDyoragay =40. The STM
`thus uses the timing advance value TD,57=30+40=70 as the
`connection continues. This testing of the base station BTS3
`is possible only because the STM is capable of using
`excessive timing advance values in the manner according to
`the invention.
`
`It should be noticed that the timing advance preset of the
`invention may be remotely controlled instead of having a
`base station, or, in addition, also some other network ele-
`mentof the radio network controlling the testing operation.
`Such a network element maybefor instance,the base station
`controller BSC or the operation and maintenance center
`OMC.
`
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`The figures and the description relating thereto are merely
`intendedto illustrate the present invention. It will be appar-
`ent that the disclosed testing equipment can be modified and
`varied without deviating from the scope and spirit of the
`appended claims.
`I claim:
`
`1. A testing equipmentfor a base station network in a time
`division multiple access radio system employing time
`advance control, in which a maximum value defined for a
`timing advance determines a maximum distance between a
`base station and a mobile station, comprising:
`said testing equipment being located at one basestation
`site which site is under control of a respective base
`station to perform test procedures on each of a plurality
`of base stations;
`said testing equipment being arranged for simulating
`operation of a normal mobile station on a respective
`radio path during said test procedures;
`said testing equipment being arranged to shift a normal
`timing advance range upwards by a preset
`timing
`advance when transmitting to a base station having a
`distance from the testing equipment which is longer
`than said maximum distance.
`2. The testing equipment according to claim 1, wherein:
`the testing equipmentis arrangedto use said preset timing
`advance offset in access bursts.
`
`3. The testing equipment according to claim 2, wherein:
`the testing equipmentis arranged to use a timing advance
`whichis the sum of the timing advance provided by a
`base station to be tested and said present
`timing
`advanceoffset.
`4. The testing equipment according to claim 2, wherein:
`the value of said preset timing advanceoffset is zero when
`the testing equipment
`is arranged for
`testing said
`respective base station or at
`least one base station
`neighboring said respective base station.
`5. The testing equipment according to claim 2, wherein:
`the testing equipment is arranged to select at least one
`value deviating from zero for the preset timing advance
`offset in order to test base stations located beyond said
`maximum distance.
`6. The testing equipment according to claim 2, wherein:
`the testing equipment
`is arranged to have said preset
`timing advance offset be remotely controlled by a base
`station or some other network element.
`
`7. The testing equipment according to claim 1, wherein:
`the testing equipmentis arranged to use a timing advance
`whichis the sum of the timing advance provided by a
`base station to be tested and said present
`timing
`advanceoffset.
`
`8. The testing equipment according to claim 1, wherein:
`the value of said preset timing advanceoffset is zero when
`the testing equipment
`is arranged for
`testing said
`respective base station or at
`least one base station
`neighboring said respective base station.
`9. The testing equipment according to claim 1, wherein:
`the testing equipment is arranged to select at least one
`value deviating from zero for the preset timing advance
`offset in order to test base stations located beyond said
`maximum distance.
`
`10. The testing equipment according to claim 1, wherein:
`the testing equipment
`is arranged to have said preset
`timing advance offset be remotely controlled by a base
`station or some other network element.
`11. A testing equipment for a base station network in a
`time division multiple access radio system employing tim-
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`5,831,974
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`ing advance control, in which a maximum value defined for
`a timing advance determines a maximum distance between
`a base station and a mobile station, comprising:
`said testing equipment being located at one base station
`site in a base station network, which site is under
`control of a respective base station,
`to perform test
`procedures on each ofa plurality of base stations;
`said testing equipment being arranged for simulating
`operation of a normal mobile station on a respective
`radio path during said test procedures;
`said testing equipment being arranged to advancea trans-
`mission of an access burst to whichever basestation is
`
`in
`timing advance offset,
`being tested, by a preset
`transmission to the base station being tested, when the
`testing equipment is setting up a test call to a base
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`station being tested, if the distance of that base station
`from the testing equipment is longer than said maxi-
`mum distance;
`
`said testing equipment being arranged to receive a timing
`advance value determined by the base station being
`tested in response to said access burst; and
`said testing equipment being arranged to use as a timing
`advancefortesting the base station being tested, which
`is the sum of said timing advance received from the
`base station being tested and said preset timing advance
`offset, in transmissions subsequentto said access burst
`to the base station being tested.
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