(21) International Application Number:
`
`PCT/FI98/00587
`
`(22) International Filing Date:
`
`13 July 1998 (13.07.98)
`
`(30) Priority Data:
`972984
`
`14 July 1997 (14.07.97)
`
`FI
`
`(71) Applicant(for all designated States except US): NOKIA MO-
`BILE PHONESLTD.[FI/FI]; Keilalahdentie 4, FIN-02150
`Espoo(FI).
`
`(72) Inventors; and
`(75) Inventors/Applicants (for US only): RINNE, Mika [FI/FI];
`Kourakuja 3 B 10, FIN-02320 Espoo (FI). JOKIMIES, Matti
`[FI/FI]; Paaiskynkatu 7 B, FIN-24130 Salo (FI). RAITOLA,
`Mika [FI/FI]; Bertel Jungin aukio 4 C 51, FIN—02600 Espoo
`(FI).
`
`(74) Agent: BERGGREN OY AB; P.O. Box 16, FIN-00101
`Helsinki (FI).
`
`Published
`With international search report.
`Before the expiration of the time limit for amending the
`claims and to be republished in the event of the receipt of
`amendments.
`
`(54) Title) METHOD FOR ALLOCATING TIME TO A MOBILE STATION
`
`(57) Abstract
`
`The invention relates to mobile communications systems,
`morespecifically to the timing of different functions of a mobile
`station. By means of the method according to the invention a
`mobile station (10) can request (100) idle time from a network
`(20) e.g.
`for measuring the strengths of signals from base
`stations. Having received the request the network checks (110)
`whethersuitable idle time is coming up andif not, allocates (120)
`idle time according to the request by the mobilestation. Finally,
`the network informs (130) the mobile station about when and
`
`PCT
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 6;
`H04Q 7/38
`
`(11) International Publication Number:
`
`WO 99/04590
`
`(43) International Publication Date:
`
`28 January 1999 (28.01.99)
`
`(81) Designated States: AL, AM, AT, AU, AZ, BA, BB, BG, BR,
`BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE,
`GH, GM, HR, HU,ID, IL, 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, TJ, 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).
`
`how much the mobile station has measurement time available.
`
`ZTE, Ex. 1016
`
`i
`
`ZTE, Ex. 1016
`
`

`

`Zimbabwe
`
`Albania
`Armenia
`Austria
`Australia
`Azerbaijan
`Bosnia and Herzegovina
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Céte d'Ivoire
`Cameroon
`China
`Cuba
`Czech Republic
`Germany
`Denmark
`Estonia
`
`SI
`SK
`SN
`SZ
`TD
`TG
`TJ
`
`Slovenia
`Slovakia
`Senegal
`Swaziland
`Chad
`Togo
`Tajikistan
`Turkmenistan
`Turkey
`Trinidad and Tobago
`Ukraine
`Uganda
`United States of America
`Uzbekistan
`Viet Nam
`Yugoslavia
`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.
`
`™T
`
`R
`TT
`UA
`UG
`Us
`UZ
`VN
`YU
`ZW
`
`ES
`FI
`FR
`GA
`GB
`GE
`GH
`GN
`GR
`HU
`IE
`IL
`Is
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`Lc
`LI
`LK
`LR
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Treland
`Israel
`Iceland
`Italy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People’s
`Republic of Korea
`Republic of Korea
`Kazakstan
`Saint Lucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`LS
`LT
`LU
`LV
`MC
`MD
`MG
`MK
`
`ML
`MN
`MR
`MW
`MX
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`
`Lesotho
`Lithuania
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`The former Yugoslav
`Republic of Macedonia
`Mali
`Mongolia
`Mauritania
`Malawi
`Mexico
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Singapore
`
`ii
`
`

`

`WO 99/04590
`
`PCT/FI98/00587
`
`Method for allocating time to a mobile station
`
`TECHNICAL FIELD OF THE INVENTION
`
`The invention relates to mobile communication systems, more specifically to the
`timing of various functions of a mobile station.
`
`BACKGROUNDOF THE INVENTION
`
`Current mobile communication systems such as the GSM system are typically based
`on a cellular structure. While moving, mobile stations (MS) often cross cell
`boundaries and at the same time changebase stations, i.e. perform a handover. A
`handover requires complex preparations,
`including e.g. synchronisation to the
`frequency and transmission sequence of the new base station. Synchronisation, in
`turn, requires that the nearby base stations be monitored and listened to. In the GSM
`system, a mobile station regularly monitors several base stations and typically trans-
`mits to the network the signal strength information of the six best base stations.
`However, mobile stations do not employ two receivers, which would facilitate
`continuous monitoring of nearby base stations, because two receivers would mean
`considerably higher complexity and manufacturing costs for the mobile station.
`Therefore, the mobile station needs free time for carrying out measurements. In the
`GSMsystem this is solved by having a pause at every 26th frame on the TCH/F
`channel transferring speech so that the mobile station has about 6 ms to make
`measurements. Such a frameis called an idle frame. The pause is repeated at 120-
`msintervals. In addition, during the same 120-msperiod there are several pauses of
`about 1 ms and 2 ms between the transmission and reception turns of the mobile
`station and base station. In the GSM system, base stations transmit synchronisation
`data on special synchronisation (SCH) and frequency control (FCCH) channels.
`These channels are repeated at certain intervals in time slots 0. However, a mobile
`station connected with another base station may have a reception turn at the same
`time since in the GSM system the base stations are not synchronised with each
`other. Therefore, the mobile station needs a longer pause, or a whole idle frame to
`receive the synchronisation data, for which these short, 1-ms and 2-ms pauses are
`not long enough. These short pauses, however, can be used for measuring the signal
`strengths of the neighbouring base stations. The GSM system and its channel archi-
`tecture, among other things, are discussed in greater detail e.g. in "The GSM System
`for Mobile Communications" by Michel Mouly and Marie-Bernadette Pautet, ISBN
`2-9507190-0-7, Palaiseau 1992. However,
`the use of the idle frame does not
`
`10
`
`15
`
`20
`
`25
`
`30
`
`1
`
`

`

`WO99/04590
`
`PCT/FI98/00587
`
`2
`
`guarantee a fast enough synchronisation to a new cell in new evolving mobile
`communication systemsthat will be discussed below.
`
`New mobile communication systems under development such as the universal
`mobile telephone system (UMTS) put more demands on the mobile stations. For
`example, future systems will employ cells of several different hierarchy levels from
`very small microcells covering possibly only one block to macro cells covering tens
`of kilometres. In such a system, the smaller cells of lower hierarchy levels will be
`used by slowly-moving mobile stations and terminals requiring high transmission
`rates. Small cell size facilitates high transmission capacity and hence new services,
`such as transmission of video images. Microcells are densely located and typically
`overlapping, so typically a mobile station changing channels can choose from
`several cells that in practice offer connections of equally good quality. Mobile
`stations moving fast, e.g. in a car, use larger cells of a higher hierarchy level because
`if they used microcells they would be compelled to change base stations very
`frequently. In addition, macro cells cover the shadow areas possibly left by the
`microcells. Such a multiple-level cell system requires that a mobile station has to
`regularly monitor very manybasestations on almostall cell hierarchy levels.
`
`From the user’s standpoint it is advantageous if the mobile station is capable of
`operating flexibly in more than one parallel mobile communication system,e.g. in
`the GSM system and in the DCS 1800 system. Presently, DCS 1800 systems are
`being constructedto alleviate the traffic problem in high-density areas, such ascity
`centres. There may also be more than two parallel systems in the future. For a
`mobile station to be able to change from a base station of one system to a base
`station of another system it has to regularly monitor the nearby base stations of that
`other system as well. The monitoring is made more difficult by the fact that the
`systems may be synchronised in different ways: precisely synchronised,
`loosely
`synchronised within certain limits, or fully asynchronous. If the base station to be
`monitored belongs to an asynchronous system, the mobile station needs measuring
`time more than usually because it has got no information on when the asynchronous
`base station will transmit the identification signal to be monitored.
`
`In mobile communication systems, communications can be roughly categorised into
`two classes: real time (RT) connections and non-real time (NRT) connections. RT
`traffic typically consists of speech or e.g. video images where nointerruptions or
`delays are allowed. NRT, or packet, communications may includee.g.file transfers
`where interruptions and delays are permitted. The RT classis typically divided into
`two sub-classes, namely, short-delay RT connections and long-delay RT connect-
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`

`

`WO 99/04590
`
`PCT/FI98/00587
`
`ions. Typically, up to 100-ms delays are allowed in the long-delay RT connections.
`The long-delay RT connections are suitable for the transmission of video images,
`for example. The short-delay RT connections are used for transmitting speech. So,
`the quality of active connections affects the requirements on the mobile station in
`connection with a handover. If a mobile station has only NRT connections, a
`momentary interruption in conjunction with a handoveris not harmful. If, however,
`there exist between the mobile station and the old base station one or more RT con-
`nections, the handover must be performed very quickly and without disturbances.
`
`Solutions according to the prior art, such as those used in the GSM system, no more
`facilitate monitoring of the necessary number of base stations as the network
`architecture of the mobile communication system gets more complex and as the
`parallel use of more than one mobile communication system becomes more general.
`
`SUMMARYOF THE INVENTION
`
`An object of the invention is to provide a method facilitating the realisation of
`necessary measurements. Another object of the invention is to provide a method
`with which a mobile station is allocated idle time it needs for measurements or other
`purposes. A further object of the invention is to provide a mobile station and com-
`munications network using the method according to the objects mentioned above.
`
`The objects are achieved by
`- arranging a mobile station to request a certain length of idle time in a certain
`period of time from a network,
`- after which the network checks if it can provide such idle time, and if it can, the
`network provides the mobile station with the idle time it requested, and
`- the network informs the mobile station when and how muchthe mobile station has
`idle time at its disposal.
`
`The method according to the invention is characterised in that it comprisesatleast
`steps wherein
`- a mobile station sends to the network an idle time request, and
`- the network informs the mobile station aboutthe idle time available.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`The mobile station according to the invention is characterised in that it is arranged
`SO as to
`
`- send to the network a request foridle time and
`- receive from the network information about the idle time available to the mobile
`
`station.
`
`

`

`WO 99/04590
`
`PCT/F198/00587
`
`4
`
`The communications network according to the invention is characterisedin thatit is
`arranged so as to
`.
`- receive from at least one mobile station a request for idle time,
`- allocate in response to the reception of said request to the mobile station atleast
`part of the idle time requested by the mobile station, and
`- send to the mobile station information about the idle time available to the mobile
`
`station.
`
`10
`
`Using the method according to the invention a mobile station can ask the network to
`arrange idle time e.g. for the measurement of the strengths of signals from base
`stations or for the synchronisation to a neighbouring base station. Having received
`the request the network checks whether available idle time is coming up soon andif
`not, arranges so that the length of time requested by the mobile station is freed.
`Finally, the network tells the mobile station when and how muchthe mobile station
`has measurementtime available.
`
`15
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention is described in more detail with reference to the preferred embodi-
`ments presented by way of example and to the accompanying drawing wherein
`
`20
`
`25
`
`30
`
`Fig. 1
`Fig. 2
`Fig.3a
`
`Fig.3b
`
`showssignalling according to an embodimentofthe invention,
`showssignalling according to a second embodimentofthe invention,
`shows a method ofallocating idle time according to an embodiment of
`the invention,
`shows
`a second method of allocating idle time according to an
`embodimentof the invention,
`showssignalling according to an embodimentof the invention,
`showsin the form of diagram a few main factors influencing the method
`of arrangingidle time,
`Figs. 6a, 6b illustrate the advantages of coordinating the pauses of several
`connections in the case of NRTtraffic,
`showsthestructure of the mobile station according to the invention,
`showssignalling in an embodimentof the invention in which idle timeis
`used for changing the battery of a mobile station, and
`Fig. 9a and 9billustrate the application of the invention to CDMAbasedsystems.
`
`Fig. 4
`Fig. 5
`
`Fig. 7
`Fig. 8
`
`Like elementsin the Figures are denotedby like reference designators.
`
`

`

`WO99/04590
`
`PCT/FI98/00587
`
`DETAILED DESCRIPTION
`
`Fig. 1 illustrates the operation of a method according to a preferred embodiment of
`the invention. First, a mobile station 10 sends 100 to the network 20 the message
`IDLE_ALLOC_REQ with which the mobile station requests the network to allocate
`idle time. Preferably the mobile station indicates in the message how muchidle time
`it needs and within which timeit needs the idle time. Having received the message
`the network 20 checks 110 whether a suitable pause is coming up in the communic-
`ation between the mobile station and the network. If such a pause is not comingup,
`the network allocates 120 to the mobile station a pause that matches the mobile
`station’s request as well as possible. Then the network sends an IDLE_INFO
`message to the mobilestation, telling it how much and whenit will have idle timeat
`its disposal.
`
`In connection with an IDLE_ALLOC_REQ message or another corresponding
`message the mobile station can put many kindsof different requests to the network.
`As was mentioned above, the mobile station preferably indicates how muchidle
`time it needs and within which period of time it needs the idle time. Additionally,
`the mobile station may indicate thatit also needs idle timelater on, in which caseit
`may indicate e.g. a certain period of time T after which the networkshall allocate to
`the mobile station the indicated amountofidle time. Such an embodimentis illust-
`rated by the end part of Fig. 1, wherein after the transmission of the first
`IDLE_INFO message the network waits 140 for the desired time T, whereafter the
`network repeats the idle time checking step 110 andthe idle time allocating step 120
`and informs 130 the mobile station about the new allocated idle period of time. The
`network may repeat the steps 140, 110 and 120 at desired intervals for the whole
`duration of the connection or e.g. for a certain numberof times, as requested by the
`mobile station.
`
`Fig. 2 shows an example of communications according to a second preferred
`embodimentof the invention. In this embodiment, more than oneidle time requests
`may be in force at the sametime. Fig. 2 alsoillustrates how a mobile station can end
`the recurrence of repeated idle time it requested earlier. In the example of Fig. 2, a
`mobile station 10 sends 100 to the network 20 a request
`for
`idle time
`IDLE_ALLOC_REQ and attaches to the request an identification code 1 and the
`necessary specification of the idle time V1. The network allocates 120 idle time to
`the mobile station as requested and stores into its memory 25 the identification code
`of the request and the specification V1’ of the idle time allocated on the basis of the
`request. Advantageously the network can store this information e.g. in a timealloc-
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`

`

`WO 99/04590
`
`PCT/FI198/00587
`
`6
`
`ation table 25 maintained by a base station communicating with the mobilestation.
`After that, the network informs 130 the mobile station aboutthe allocated time using
`an IDLE_INFO message. In the example of Fig. 2 the mobile station needs later on
`moreidle time and therefore it sends 150 to the network a new request for idle time
`IDLE_ALLOC_REQ to which it attaches the identification code 2 of the new
`request and the specification V2 of the idle time requested. The network provides
`160 the idle time 2 requested by the mobile station and adds the data about the idle
`time to the time allocation table 25. Then the network sends 170 to the mobile
`station the information about the idle time allocated in an IDLE_INFO message.
`After that the mobile station sends 180 to the network an IDLE_DISABLE message
`to which the mobile station attaches the identification code 1 of the idle time to be
`deleted. In response to the reception of the IDLE_DISABLE messagethe network
`deletes the idle time1, i.e. takes it back to communications use and removesthe data
`about the idle time in question from the time allocation table 25. Next, the mobile
`station needs to alter the earlier allocated idle time 2 and therefore it sends to the
`network a new idle time request IDLE_ALLOC_REQ to which it attaches the
`identification code 2 ofthe idle time to be altered and a specification V3 for the new
`idle time. If the new idle time V3 requested by the mobile station substantially
`differs from the previous allocated idle time V2’ the network can, in the manner
`depicted in Fig. 2, first remove 210 the allocation of the previousidle time and then
`allocate 220 an idle time according to the new request V3.
`
`allocation modification message
`time
`idle
`the
`above,
`example
`the
`In
`(IDLE_ALLOC_REQ) and removal message IDLE_DISABLE) werepresented as
`two separate messages. However,
`the invention is not
`limited to this, but
`the
`functions in question can be realised using one command,e.g. in such a waythat in
`the modification message (IDLE_ALLOC_REQ) the requested time is defined as
`zero whentheidle timeis to be deleted.
`
`Such an arrangement with more than one idle time can be advantageously used e.g.
`in such a manner that
`the mobile station has for the whole duration of the
`connection at is disposal a periodically repeated short idle period and, if necessary,
`the mobile station can request for longer idle periods for special situations. Unlike in
`the example of Fig. 1, idle time requests and other messages related to idle times
`have to be accompaniedby an identification code so as to be directed to the correct
`idle time allocation. The identification code may be e.g. the serial number generated
`by the mobilestation for the idle time requests, as shown in the exampleofFig.2.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`

`

`WO 99/04590
`
`PCT/FI98/00587
`
`7
`
`Step 110 in the example of Fig. 1, in which the network checks whether the mobile
`station has idle time available to it, does not limit the various embodiments of the
`invention. As seen from the example of Fig. 2, the network mayalso allocate the
`idle time requested by the mobile station directly, without a separate checking step.
`
`In a preferred embodimentof the invention the network may automatically remove
`all existing idle time allocations in conjunction with a handover or when someother
`condition is met. In such an embodiment the mobile station may advantageously
`indicate in connection with a repeated idle time request IDLE_ALLOC_REQthatit
`needs the idle time in question also after a possible handover so that the network
`will not automatically delete the idle time in question unless so requested by the
`mobile station with an IDLE_DISABLE message. This function is advantageous in
`a case in which the mobile station regularly needs idle time e.g.
`to carry out an
`internal operation of its own or for a purpose not related to the monitoring of base
`stations.
`
`The mobile station may also simply request information about possible available
`idle periods. In such an embodiment the network will not allocate idle time, unless
`specifically requested by the mobile station, but only tells the current situation. Such
`an embodimentis particularly well suited to be used in conjunction with packet-type
`communications as there occurs, depending onthe traffic fluctuation, pauses in the
`packet-typetraffic, unless it is constantly at the maximum volume.
`
`In a preferred embodiment of the invention the network may inform the mobile
`station about pauses in the traffic between the network and the mobile station also
`without a separate request from the mobilestation.
`
`The mobile station can indicate the idle time it needs in many different ways which
`will be described in the paragraphs to follow and illustrated by means of Figs. 3a
`and 3b. In Figs. 3a and 3b the horizontal rows contain the frames’ time slots 0 to 7
`and the vertical columns the frames. Time slots and/or frames requested idle are
`marked black. For example, the mobile station may indicate how many framesit
`needs idle during a certain period of time. In the example of Fig. 3a, the mobile
`station requests one idle frame at ten-frame intervals. There may be more than one
`frame requested idle and the length of the period may be something other than ten
`frames.
`
`In the example of Fig. 3a the pause is repeated regularly every tenth frame. In a
`preferred embodimentof the invention the network may also arrange the frames at
`
`10
`
`15
`
`20
`
`25
`
`30
`
`

`

`WO 99/04590
`
`PCT/FI98/00587
`
`8
`
`irregular intervals, however so that the mobile station always gets the desired
`number of idle frames during a certain period of time. In such an embodimentthe
`network mustindicate to the mobile station the timing of each idle frame.
`
`The mobile station mayalso indicate if the pause can be allocated, advantageously
`from the mobile station’s standpoint, in more than one parts. Thus the mobilestation
`may request e.g. one two-frame and one three-frame pause during the next 26-frame
`period.
`
`The mobile station mayalso requestidle time in terms of timeslots, e.g. by request-
`ing certain time slots in certain frames idle. Such a request is illustrated by the
`example of Fig. 3b, wherein time slots 0, 1 and 5 in frames 1 and 2, 11 and 12, and
`so on, are marked idle. Naturally, the mobile station may also request a certain
`numberof timeslots idle in a certain unit of time without specifying the frame and
`the time slots in which the idle time should be located so that the network can
`allocate the idle time slots optimally according to the traffic situation.
`
`In the examplesof Figs. 3a and 3b the framesare divided into eight time slots like in
`the GSM system. However, the invention is not limited to this time slot division as
`other time slot divisions are possible in other systems. For example, the future
`UMTSsystem will probably use shorter time slots, too, whereby there may be from
`16 to 64 timeslots in a frame according to some of the presently planned
`specifications.
`
`In a preferred embodiment of the invention the mobile station may request the
`network to allocate idle time for a certain specified purpose, say, monitoring of the
`synchronisation signals of a certain base station specified by the mobile station. In
`such an embodiment
`the network finds out the occurrence information of the
`synchronisation signals of the base station specified by the mobile station, located in
`either the same network or another mobile communication system, and, taking into
`account the mobile station’s capabilities, reserves the necessary amountofidle time
`for the moment of occurrence of the synchronisation signals and sends to the mobile
`station the occurrence information of the synchronisation signals in question as well
`as the allocated measurementtime or times. Here, occurrence information refers to
`the frequency and timing of the synchronisation signals and the possible frequency
`hopping or spread spectrum code used by the synchronisation signals as well as each
`location in said code and possible other data needed in the monitoring of the
`synchronisation signals in question. Such an embodimenthas the advantage that the
`mobile station need not inquire for the time of occurrence and frequency of the
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`

`

`WO 99/04590
`
`PCT/FI98/00587
`
`9
`
`synchronisation signals of a certain base station and after that separately request idle
`time for the monitoring of the synchronisation signals in question, but the mobile
`station gets the necessary signal data and idle time on one request.
`
`Preferably, the network allocates to the mobile station the whole amount of time
`requested by the mobile station. In a congested traffic situation this, however, may
`not be possible, in which case the network tells the mobile station how muchidle
`time the network wasable to allocate. The network mayalso allocate to the mobile
`station more time than what was requestedif, due to the size of allocation units, the
`network cannotallocate the exact amountof time requested by the mobile station.
`
`10
`
`15
`
`The network can allocate idle time to the mobile station in may ways, such as
`- by swapping time slots used by mobile stations,
`- stealing certain bursts,
`- interrupting the traffic for a desired time or
`- forming idle frames in the connection.
`These alternatives will be described in moredetail in the paragraphs below.
`
`The network, advantageously a base station communicating with the mobilestation,
`can make arrangements between time slots used in the connections of different
`mobile stations. Such an arrangementis especially suitable when, from the point of
`view of a certain mobile station, the time best suited for the measurementof identi-
`fication signals of a certain neighbourcell or certain neighbour cells does not co-
`incide with a time slot used by the mobile station in question, but with a time slot
`used by another mobile station communicating with the same basestation. The base
`station can then e.g. swap the time slots used by those two mobilestations. If
`necessary, the base station may also swap time slots used by more than two mobile
`stations.
`
`Stealing a burst means that a certain burst is deliberately left unreceived and instead
`of burst reception a desired neighbour cell base station measurementis carried out,
`for example. Such a method naturally loses information, which limits its use. With
`real-time connections, which havestrict requirements regardingthebit rate, allowed
`delays and numberoferrors, burst stealing substantially can be used only if the
`quality of the connection is good andthe transmitted signalis sufficiently coded so
`that the increase in the bit error ratio caused by the absence of one burst will not
`makethe bit error ratio exceed the allowed limit. With real-time connections, burst
`stealing can advantageously be used only if the quality of service (QoS) specified
`for the connection will not go below the allowed limit because ofthe stealing of a
`
`20
`
`25
`
`30
`
`35
`
`

`

`WO 99/04590
`
`PCT/FI98/00587
`
`10
`
`burst. A QoS specification typically involves the bit rate, maximum allowed delay
`and maximum allowed bit error ratio of the connection. Burst stealing may also be
`realised partially by allowing burst stealing only on non-real-time, or packet,
`connections. The ordinary retransmission mechanisms of packet-type com-
`munications will then cause retransmission of a stolen burst so that information will
`
`notbelost.
`
`Burst stealing may also be realised in such a mannerthat the mobile station leavesat
`least one burst untransmitted and uses the time thus freed for other purposes. In such
`an embodimentthe network preferably indicates to the mobile station which bursts
`the mobile station can leave untransmitted.
`
`10
`
`Traffic interruption can be used with non-real-time connections. The network, e.g. a
`base station communicating with the mobile station, can interrupt the packet stream
`to the mobile station for a certain period of time, thereby freeing time for the mobile
`station so that the mobile station can carry out measurements, for example.
`
`15
`
`The mobile station may also make a request to the network for an idle frame. During
`an idle frame the network will not send information to the mobile station and
`
`transmit
`respond to signalling or
`the mobile station will not
`assumes that
`information. How often the mobile station wants the idle frame to be repeated and
`wherein the multiple frame structure are factors that have to specified according to
`the system to which the mobile station wants to synchronise itself. For example, in
`the GSM system the idle frame is repeated every 26th frame and in the GSM/GPRS
`system every 13th frame. So, each mobile station can request the necessary number
`of idle frames for which the network mayallocate the required idle time e.g. in any
`one of the manners described above. A base station communicating with a mobile
`station may advantageously maintain a table indicating each mobile station’s need
`for idle frames.
`
`In a preferred embodiment of the invention the mobile station indicates to the
`network the function set it supports, its probable traffic needs and measurement time
`needsor at least some of these data already whenit contacts the networkforthe first
`time. The mobile station may also indicate whether it is capable of communicating
`with potential parallel mobile communication systems and whetherit will possibly
`need measurementtime for this. The mobile station may also indicate to the network
`its certain measurement-related characteristics such as
`- how long a timeit takes the mobilestation to transit to the frequency measured and
`to return,
`
`20
`
`25
`
`30
`
`35
`
`

`

`WO 99/04590
`
`PCT/FI98/00587
`
`11
`
`takes
`
`-how long a time it
`measurement(s) and
`-the minimum time needed by the mobile station for
`transmission to reception and vice versa.
`
`the mobile station to carry out certain basic
`
`the transition from
`
`In a preferred embodimentof the invention the network may, in order to speed up
`measurements, send to the mobile station certain information related to the
`surroundings of the mobile station and to the beacon signals of the basestations in
`neighbouring cells. The network may transmit such information at regular intervals
`or on separate request by the mobile station. This information advantageously
`comprises one or moreofthe following items:
`- a list of neighbour cells,
`- information aboutdifferentcell hierarchies,
`- information about nearbycells of parallel mobile communication systems,
`- identification data of neighbourcells,
`- the frequencies of the beacon signals of the neighbourcells,
`- the bandwidth of the beaconsignals,
`- information about whether the beacon signal of a base station is continuous or
`discontinuous andif it is discontinuous, information about the occurrence times of
`the beacon signal and the length of the time window needed for the monitoring of
`the beacon signal and
`-a description of the occurrence of the neighbour cells’ frequency and time
`synchronisation signals, e.g. at what frequencies and what moments of time the
`signals in question appear and what kind of frequency hopping or spread spectrum
`code the neighbour cells use and where in said code the synchronising signals are
`sent at each particular time.
`
`In a preferred embodimentof the invention the network selects the information sent
`to the mobile station according to the function set of the mobile station. This kind of
`an embodimentis advantageouse.g. in a case wherein a certain geographic area has
`in addition to the network a parallel mobile communication system but a mobile
`station in the area in question cannot use that parallel mobile communication
`system. In such a situation it would be useless to send to the mobile station
`information about the parallel mobile communication system. Similarly, the mobile
`station may send to the network a request concerning only certain information
`according to its functionset.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`

`

`WO 99/04590
`
`PCT/FI98/00587
`
`12
`
`Fig. 4 shows an example of signalling in a preferred embodimentof the invention
`wherein idle time is used for receiving beacon signals of base stations. In t