Adjusting the transmission power of a forward access channel (FACH), and a corresponding network for mobile telecommunications

Description

Technical Field

[0001] The present invention relates to transmission power of a Forward Access Channel (FACH) in a network for mobile telecommunications. The present invention also relates to a network for mobile telecommunications.

Background of the Invention

[0002] As part of radio resource management, a mobile user terminal (user equipment, UE) is moved from one resource state to another in order to maximise the efficiency of the available radio resources (e.g. power, bandwidth). The Universal Mobile Telecommunications System (UMTS) standard requires each mobile user terminal to take either of two states for active data transmission, namely cell forward access channel (Cell-FACH) state and cell dedicated channel (Cell-DCH) state, (see for example Third Generation Partnership Project (3GPP) Technical Specification 25.331).

[0003] In Cell-FACH state, a shared channel, specifically the forward access channel (FACH), is used shared between a group of mobile user terminals and having no associated dedicated physical control channel. The forward access channel (FACH) is used for low volume data and is similar to the broadcast channel and random access channel of older mobile technologies. It may typically be used e.g. for the viewing time after a Web page download. Use of the forward access channel (FACH) gives improved cell capacity at low data rates and thus improves the battery life of the mobile user terminal due to the lower transmission power that is required.

[0004] On the other hand, Cell-DCH state uses a dedicated channel (DCH) to a mobile user terminal which has a dedicated physical control channel, including transmit power control information and pilot information, continuously transmitted. A dedicated channel (DCH) of a cell is typically used for high volume data or voice.

[0005] Whilst in Cell-DCH state, the mobile user terminal reports to the base station when criteria are met such as when the measured signal from a monitored base station goes above or below a threshold, whereupon the base station may choose to add or remove a soft handover leg (i.e soft handover connection, also known as soft handoff connection).

[0006] The standards provide a variety of measurement reporting methods for reporting handover measurements (3GPP Technical Specification 25.331 Section 14.1.2), but whilst the mobile user terminal is in Cell-FACH state, measurements on received signals are disabled as they might result in frequent measurement reports back to the base station thereby reducing the capacity of the channel for user data or voice.

[0007] Furthermore, the standards provide no reliable means for determining the transmit power at which each Forward Access Channel (FACH) frame should be broadcast to the mobile user terminal (UE), so the FACH channel is always broadcast at a high power sufficient to cover the whole cell.

[0008] Furthermore, as regards criteria for transiting between Cell-FACH state and Cell-DCH state, a known criterion is level of occupancy of the buffer (in the mobile user terminal) which stores data to be sent. A buffer occupancy measurement is passed from the mobile user terminal to the base station where a decision to instruct a change of state is made.

[0009] As further background, Dynamic Bearer Control (DBC) is a commonly understood mechanism defined within the 3GPP standards which determines whether, and to what extent, to grant resources, i.e to allocate a data rate, based upon the estimated power consumption. The DBC functional block usually receives no power information or soft handover information. Accordingly, the DBC functional block assumes that a mobile user terminal requires maximum power when transiting into a Cell-DCH state so may allocate a lower data rate than it needs to, or even refuse to provide DCH resources.

[0010] When the base station decides that the mobile user terminal in the Cell-FACH state should transition to Cell-DCH state, it must do so without any soft handover legs i.e. without second or further radio connections between the mobile user terminal and other cells than the primary one. This is because there are no soft handover connections to mobile user terminals in the Cell-FACH state. Also the base station and mobile user terminal must start with a high initial transmit power in order to ensure a rapid synchronisation between the mobile user terminal and the base station. These result in a reduction in the traffic capacity, particularly in cases where the transitions between the two states are frequent.

[0011] It is known from United States Published patent application US 2002/0094833 to provide a method in a network for mobile telecommunications of adjusting the transmission power of a Forward Access Channel from a base station to a mobile user terminal, comprising the steps of:

the base station sending a signal at a first transmission power level to the mobile user terminal,

the mobile user terminal sending a report of one or more parameter values dependent upon measured signal quality

the base station adjusting its transmission power to the mobile user terminal in consequence so as to maintain the measured signal quality within acceptable limits.

Summary of the Invention

[0012] The present invention is characterised over the disclosure of US 2002/0094833 in that the mobile user terminal sends the report upon a predetermined reporting criterion being met, and
in which upon the mobile user terminal transiting from a Cell-FACH state to a Cell-DCH state, the initial transmission power to the mobile user terminal in the Cell-DCH state is dependent upon the last adjusted transmission power level in the preceding Cell-FACH state.

[0013] A method and a network according to the present invention are defined in the independent claims to which the reader should now refer. Preferred features are laid out in the dependent claims.

[0014] An example of the present invention is a method of adjusting the transmission power of a Forward Access Channel (FACH) from a base station to a mobile user terminal in a network for mobile telecommunications. The method comprises steps as follows. The base station sends a signal at a first transmission power level to the mobile user terminal. The mobile user terminal then sends a report of one or more parameter values dependent upon measured signal quality provided a predetermined reporting criterion is met. The base station then adjusts its transmission power to the mobile user terminal in consequence so as to maintain the measured signal quality within acceptable limits.

[0015] A feedback mechanism is thus provided to adjust the power of a transmission to a mobile user terminal in Cell-FACH state. This results in more efficient power allocation and hence improved traffic capacity.

[0016] The predetermined reporting criterion can be that the change in measured signal quality from the measured signal quality of the last report is greater than a predetermined amount. If this criteria is met the transmission power is adjusted in consequence. In some embodiments, a means is thus provided for sending back measurement information at an appropriately low rate to the base station as otherwise, in some circumstances, power control on the FACH channel would significantly increase traffic. Slow power control of the FACH channel is thus provided (slow in the sense of being occasional feedback, rather than the continuous feedback as occurs in a dedicated channel).

[0017] When the mobile user terminal transits from a Cell-FACH state to a Cell-DCH state, the initial transmission power to the mobile user terminal in the Cell-DCH state can be set dependent upon the last adjusted transmission power level in the preceding Cell-FACH state. Thus a more accurate initial transmit power level is provided, which is specific to the mobile user terminal, when being transitioned by the base station from Cell-FACH state to Cell-DCH state. In some embodiments, transiting between states happens at a frequent rate so efficient power allocation (whilst maintaining rapid synchronisation between mobile user terminal and base station during state transitions) is particularly beneficial.

[0018] Transition to the Cell-DCH state preferably occurs dependent upon transmission power in the Cell-FACH state being lower than a predetermined limit. The measurement reports thus provide additional information usable as a factor in determining when to transit between Cell-DCH and Cell-FACH states. In particular the measured SIR of the received signal, for example, can be used as a factor in deciding when to transit from Cell-FACH state, for example to Cell-DCH state.

[0019] Preferably, the adjusted power level is taken as the transmission power level to be used initially in soft handover connection to a neighbouring cell upon the soft handover connection being established. Preferably, the network is a code division multiple access network at least substantially in accordance with a Third Generation Partnership Project standard. Preferably, the measured signal quality is signal to interference ratio (SIR).

[0020] The present invention also provides a corresponding network for mobile telecommunications. An example comprises a base station and a mobile user terminal. The base station is operative to send a signal at a first transmission power level to the mobile user terminal on a Forward Access Channel (FACH). The mobile user terminal is operative to send a report of one or more parameter values dependent upon measured signal quality upon a predetermined reporting criterion being met. The base station is then operative to adjust its transmission power to the mobile user terminal in consequence so as to maintain the measured signal quality within acceptable limits.

Brief Description of the Drawings

[0021] A preferred embodiment of the present invention will now be described by way of example and with reference to the drawings, in which:

Figure 1 is a diagram illustrating a UTRAN network and a mobile user terminal,

Figure 2 is a diagram illustrating a radio network controller and a base station,

Figure 3 is a diagram illustrating an example messaging sequence and

Figure 4 is a diagram illustrating a further example messaging sequence.

Detailed Description

[0022] The preferred network is a Universal Mobile Telecommunications System (UMTS) terrestrial access network (UTRAN), which is a type of wideband code division multiple access (CDMA) network for mobile telecommunications. The UTRAN network is basically as shown in Figure 1. Only one radio network controller and two base stations of the UTRAN network 2 are shown for simplicity. As shown in this Figure, the UTRAN network 2 includes base stations 4. Each base station (Node B in UMTS terminology) 4 typically has three cells 6 (i.e. radio coverage areas, also known as sectors) as the base station 4 typically has three directional antennas (not shown) angled at 120 degrees to each other in azimuth. Radio network controllers (RNC) 8 which are themselves connected to the rest of the telecommunications "world" (not shown) each control several base stations 4 and hence a number of cells 6. A base station 4 is connected to its controlling radio network controller (RNC) 8 via a respective interface 10 known as an IuB interface. In use, a mobile user terminal 12 (often referred to as User Equipment (UE) in UMTS terminology) communicates with a serving radio network controller (RNC) 8 via at least one cell 6 of at least one base station 4 (i.e. communicates with the UTRAN network 2). As shown in Figure 2, the RNC 8 includes a Dynamic Bearer Control (DBC) block as will be described later.

Example Processes

[0023] Figure 3 shows a mobile user terminal entering Cell-FACH state (denoted steps a,b in Figure 3), receiving data (c), detecting that the received signal to interference ratio (SIR) of the serving cell has improved and so triggering a measurement report (d,e), and receiving subsequent data at lower power (f). It also shown transiting to Cell-DCH state (g,h).

[0024] Figure 4 shows a mobile user terminal in Cell-FACH state (j), a neighbour cell having previously been reported as satisfying soft- handover criteria, the neighbour cell no longer meeting the criteria and so sending a measurement report (k), this being received and confirmed (1) by the base station. It also shows a further neighbour no longer meeting the criteria (m) and so acting similarly. It also shows a further neighbour now meeting the criteria (o) and sending a measurement report accordingly. In this case, the RNC decides the measurement reporting is too frequent and so disables (p) the measurement reporting.

Underlying Process

[0025] The general process underlying the Figure 3 and Figure 4 examples is as described in the seven numbered steps as follows.

(1) On entering Cell-FACH state, the mobile user terminal takes measurements of the Serving Cell received quality (Pilot Channel Signal to interference ratio) and sends this back to the base station along with measurements of the same parameter of the neighbouring cells (denoted (a) in Figure 3). When transiting from Cell-FACH state to Cell-DCH state, the base station, of course, needs to transmit at an initial output power which will be reliably received by the mobile user terminal and preferably on the most significant handover legs.

(2) The System Information Broadcast (SIB) channel is read by all mobile user terminals when they enter Cell-FACH state before they are able to start transmission (a in Figure 3). From this channel, a new set of measurement reporting criteria are broadcast to the mobile user terminal (b in Figure 3).
The measurement reporting criteria are Delta SIR, Delta Soft Handover SIR, and Delta Soft Handover SIR Hysteresis being sufficiently large. Delta SIR indicates the absolute difference between the current Measured Signal to Interference Ratio and the last reported SIR to the Base station before a new report must be generated. Delta Soft Handover SIR indicates the difference in SIR between the serving cell and best neighbour SIR before a new report is generated. Delta Soft Handover SIR Hysteresis indicates the required hysteresis on that for reporting addition of the best neighbour or removal of the best neighbour from being considered for handover connection. The Figure 3 example shows the criteria for the best neighbour cell, but can easily be extended to seek multiple best neighbour cells.

(3) When the mobile user terminal detects that at least one of the criteria have been satisfied for a report, it sends a measurement report (d in Figure 3, k in Figure 4) on an unacknowledged mode transmission to the base station. The criteria are:

i) The Serving cell Pilot SIR has changed by more than Delta SIR since the last reported measurement. A first reference level 20 is the measured SIR value SIR1 sent in the last measurement report. A change in SIR of more than DeltaSIR 22 triggers a further measurement report 24 which reports an SIR value SIR2. Also a new reference level 26 is then set of SIR2 being SIR1 + DeltaSIR. When the measured SIR deviates from the reference level 26 by more than DeltaSIR, a further measurement report is triggered 28.

ii) The difference in between the serving cell SIR 31 and best neighbour cell SIR 33 is greater than Delta Soft Handover SIR (34) + Delta Soft Handover SIR Hysteresis (36), the best neighbour SIR 33 being lower than the serving cell SIR 31. The measurement report generated indicates removal of a soft handover leg for use in Cell-DCH state.

iii) The difference between the best neighbour cell 33 and the serving cell SIR 31 has gone to less than Delta Soft Handover SIR (34) - Delta Soft Handover SIR Hysteresis (36), the best neighbour SIR 33 being lower than the serving SIR 31. The measurement report generated indicates inclusion of a new soft handover leg for use in Cell-DCH state.

(4) The base station responds with a measurement response message to the mobile user terminal (e in Figure 3, 1,n in Figure 4). The measurement response message has the following purposes:

i) The response is transmitted at the new power level, and if the mobile user terminal receives the response correctly, the mobile user terminal will not repeat the measurement report message transmission.

ii) The mobile user terminal gets an acknowledgement of measurement report message reception from the base station which means that retransmission is unnecessary.

iii) The message acknowledging receipt of the measurement report by the base station has some optional information elements which may be used to configure the time between reports to a longer interval. Such an option is most useful for mobile user terminals which are of high mobility, and so are generating frequent reports and hence a large amount of interference (p in Figure 4).

The optional elements may also be extended to reconfigure other aspects of the measurement criteria, e.g. to increase hysteresis.

(5) The Base Station uses the most recent report of Serving Cell Pilot SIR (and optionally neighbour cell SIR)to determine the transmit power of a FACH frame to a mobile user terminal (c,e,f,g in Fig.3, 1,p in Fig.4).

(6) In determining the criteria for transiting from Cell-FACH state to Cell-DCH state, the base station takes into account an estimate of the required mobile user terminal transmit power based upon the latest report of serving Cell SIR (g in Fig.3). Basically, the higher the SIR and hence the lower the power estimate is, the less likely is the transition to the DCH state.

(7) When the mobile user terminal transits from Cell-FACH state to Cell-DCH state, the base station sets up the transmissions as follows based upon the last-received report:

a) Perform Dynamic Bearer Control (DBC) based upon the information from the last-received report. The DBC block is in the radio network controller (RNC) controlling the base station as shown in Figure 2 and determines whether and to what extent to grant resources, i.e to allocate a data rate, based upon the estimated power consumption.

b) If the last-received report indicated a neighbour cell meeting the defined criteria then set up a soft handover leg to the neighbour cell as well as the serving cell.

c) Start the initial downlink transmit power based upon the last reported serving cell pilot SIR.

[0026] The reader will note that in the preferred embodiment described above, SIR is the measure of signal quality which is used. In other embodiments, other measures of signal quality are used instead, such as bit error rate, received signal strength, or error vector magnitude.

Abbreviations

[0027] 

3GPP

Third Generation Partnership Project

DBC

Dynamic Bearer Control

DCH

Dedicated channel

FACH

Forward access channel

RNC

Radio network controller

SIR

Signal to interference ratio

UE

User Equipment, i.e. mobile user terminal

UMTS

Universal Mobile Telecommunications System

UTRAN

UMTS terrestrial radio access network

Claims

1. A method in a network for mobile telecommunications of adjusting the transmission power of a Forward Access Channel, FACH, from a base station (4) to a mobile user terminal (12), comprising the steps of:

the base station (4) sending a signal at a first transmission power level to the mobile user terminal that is in cell-FACH state,

the mobile user terminal (12) sending (d) a measurement report (24) of one or more parameter values dependent upon measured signal quality

the base station (4) adjusting (f) its transmission power to the mobile user terminal based on said measurement report so as to maintain the measured signal quality within acceptable limits, characterised in that the mobile user terminal (12) sends the report (24) upon a predetermined reporting criterion being met, and

in which upon the mobile user terminal (12) transiting (h) from a Cell-FACH state to a Cell-DCH state, the initial transmission power to the mobile user terminal (12) in the Cell-DCH state is dependent upon the last adjusted transmission power level in the preceding Cell-FACH state.

2. A method according to claim 1, in which the predetermined reporting criterion is that the change in measured signal quality, from the measured signal quality (20) of the last report is greater than a predetermined amount (22) whereupon the transmission power is adjusted in consequence.

3. A method according to claim 1 or claim 2, in which transition to the Cell-DCH state occurs dependent upon transmission power in the Cell-FACH state being lower than a predetermined limit.

4. A method according to any preceding claims, in which if a soft handover connection is set up, the connection is set up with an initial transmission power from the base station which is mobile user terminal specific.

5. A method according to any of claims 1 to 4, in which the last received parameter values are used to determine whether a soft handover connection is to be set up when transiting from Cell-FACH to Cell-DCH state.

6. A method according to any of claims 1 to 5, in which a dynamic bearer controller in the base station (4) allocates a data rate for Cell-DCH state dependent upon the last received parameter values from the mobile user terminal (12).

7. A method according to any preceding claim, in which the predetermined reporting criterion is such that when the measured signal quality from the best neighbour cell (33) is less than the measured signal quality from the serving cell (31) by more than a first predetermined amount when (32) the mobile user terminal is in a soft handover region but in Cell-FACH state, the best neighbour is removed from a list of cells for soft handover connection in the Cell-DCH state.

8. A method according to any preceding claim, in which the predetermined reporting criterion is such that when the measured signal quality from the best neighbour cell (33) is less than the measured signal quality from the serving cell (31) by less than a first predetermined amount when (30) the mobile user terminal is in a soft handover region but in Cell-FACH state, the best neighbour is added to a list of cells for connection in the Cell-DCH state.

9. A network for mobile telecommunications comprising a base station (4) and a mobile user terminal (12),
the base station (4) being operative to send a signal at a first transmission power level to the mobile user terminal on a Forward Access Channel, FACH,
the mobile user terminal (12) being operative to send (d) a measurement report of one or more parameter values dependent upon measured signal quality,
the base station (4) being operative to adjust (f) its transmission power to the mobile user terminal (12) based on said measurement report so as to maintain the measured signal quality within acceptable limits, characterised in that
the mobile user terminal (2) is operative to send the report (24) upon a predetermined reporting criterion being met, in which upon the mobile user terminal (12) transiting (h) from a Cell-FACH state to a Cell-DCH state, the initial transmission power to the mobile user terminal (12) in the Cell-DCH state is dependent upon the last adjusted transmission power level in the preceding Cell-FACH state.

Ansprüche

1. Verfahren in einem Netz für Mobiltelekommunikation zum Regeln der Sendeleistung eines Abwärts-Zugriffskanals FACH (Forward Access Channel) von einer Basisstation (4) zu einem Mobilbenutzerendgerät (12) mit folgenden Schritten:

Senden eines Signals mit einem ersten Sendeleistungspegel durch die Basisstation (4) zum Mobilbenutzerendgerät, das sich im Cell-FACH-Zustand befindet,

Senden (d) eines Messungsberichts (24) eines oder mehrerer Parameterwerte in Abhängigkeit der gemessenen Signalgüte durch das Mobilbenutzerendgerät (12),

Einstellen (f) durch die Basisstation (4) ihrer Sendeleistung zum Mobilbenutzerendgerät auf Grundlage des Messungsberichts zum Erhalten der gemessenen Signalgüte innerhalb von annehmbaren Grenzen, dadurch gekennzeichnet, daß das Mobilbenutzerendgerät (12) den Bericht (24) bei Erfüllung eines vorbestimmten Berichterstattungskriteriums sendet, und

wobei bei Übergang (h) des Mobilbenutzerendgeräts (12) von einem Zustand Cell-FACH zu einem Zustand Cell-DCH die anfängliche Sendeleistung zum Mobilbenutzerendgerät (12) im Zustand Cell-DCH von dem letzten eingestellten Sendeleistungspegel im vorhergehenden Zustand Cell-FACH abhängig ist.

2. Verfahren nach Anspruch 1, wobei das vorbestimmte Berichterstattungskriterium darin besteht, daß die Änderung der gemessenen Signalgüte von der gemessenen Signalgüte (20) des letzten Berichts größer als ein vorbestimmter Betrag (22) ist, woraufhin die Sendeleistung infolge dessen eingestellt wird.

3. Verfahren nach Anspruch 1 oder Anspruch 2, wobei der Übergang zum Zustand Cell-DCH in Abhängigkeit davon stattfindet, daß die Sendeleistung im Zustand Cell-FACH niedriger als eine vorbestimmte Grenze ist.

4. Verfahren nach einem beliebigen vorhergehenden Anspruch, wobei, wenn eine Verbindung mit sanfter Weiterschaltung aufgebaut wird, die Verbindung mit einer anfänglichen Sendeleistung von der Basisstation aufgebaut wird, die Mobilbenutzerendgeräte-spezifisch ist.

5. Verfahren nach einem der Ansprüche 1 bis 4, wobei die letzten empfangenen Parameterwerte dazu benutzt werden, zu bestimmen, ob bei Übergang vom Zustand Cell-FACH zum Zustand Cell-DCH eine Verbindung mit sanfter Weiterschaltung aufzubauen ist.

6. Verfahren nach einem der Ansprüche 1 bis 5, wobei eine dynamische Trägersteuerung in der Basisstation (4) eine Datenrate für den Zustand Cell-DCH in Abhängigkeit von den letzten empfangenen Parameterwerten vom Mobilbenutzerendgerät (12) zuteilt.

7. Verfahren nach einem beliebigen vorhergehenden Anspruch, wobei das vorbestimmte Berichterstattungskriterium ein solches ist, daß wenn die gemessene Signalgüte von der besten Nachbarzelle (33) um mehr als einen ersten vorbestimmten Betrag geringer als die gemessene Signalgüte von der versorgenden Zelle (31) ist, wenn (32) sich das mobile Benutzerendgerät in einem Gebiet sanfter Weiterschaltung aber im Zustand Cell-FACH befindet, der beste Nachbar aus einer Liste von Zellen für Verbindung mit sanfter Weiterschaltung im Zustand Cell-DCH entfernt wird.

8. Verfahren nach einem beliebigen vorhergehenden Anspruch, wobei das vorbestimmte Berichterstattungskriterium ein solches ist, daß wenn die gemessene Signalgüte von der besten Nachbarzelle (33) um weniger als ein erster vorbestimmter Betrag geringer als die gemessene Signalgüte von der versorgenden Zelle (31) ist, wenn (30) sich das mobile Benutzerendgerät in einem Gebiet sanfter Weiterschaltung aber im Zustand Cell-FACH befindet, der beste Nachbar zu einer Liste von Zellen zur Verbindung im Zustand Cell-DCH zugefügt wird.

9. Netz für Mobiltelekommunikation mit einer Basisstation (4) und einem Mobilbenutzerendgerät (12),
wobei die Basisstation (4) zum Senden eines Signals mit einem ersten Sendeleistungspegel zum Mobilbenutzerendgerät auf einem Abwärts-Zugriffskanal FACH (Forward Access Channel) fungiert;
wobei das Mobilbenutzerendgerät (12) zum Senden (d) eines Messungsberichts einer oder mehrerer Parameterwerte in Abhängigkeit von der gemessenen Signalgüte fungiert,
wobei die Basisstation (4) zum Regeln (f) ihrer Sendeleistung zum Mobilbenutzerendgerät (12) auf Grundlage des Messungsberichts fungiert, um die gemessene Signalgüte in annehmbaren Grenzen zu halten, dadurch gekennzeichnet, daß
das Mobilbenutzerendgerät (2) zum Senden des Berichts (24) bei Erfüllung eines vorbestimmten Berichterstattungskriteriums fungiert, wobei bei Übergang (h) des Mobilbenutzerendgeräts (12) von einem Zustand Cell-FACH zu einem Zustand Cell-DCH die Anfangssendeleistung zum Mobilbenutzerendgerät (12) im Zustand Cell-DCH von dem zuletzt eingestellten Sendeleistungspegel im vorhergehenden Zustand Cell-FACH abhängig ist.

Revendications

1. Procédé dans un réseau de télécommunications mobiles de réglage de la puissance d'émission d'un Canal d'Accès Aller, FACH, depuis une station de base (4) vers un terminal d'utilisateur mobile (12), comprenant les étapes consistant en :

l'envoi par la station de base (4) d'un signal à un premier niveau de puissance d'émission au terminal d'utilisateur mobile qui est dans l'état Cell-FACH,

l'envoi (d) par le terminal d'utilisateur mobile (12) d'un rapport de mesure (24) d'une ou de plusieurs valeurs paramétriques dépendant de la qualité de signal mesurée,

le réglage (f) par la station de base (4) de sa puissance d'émission vers le terminal d'utilisateur mobile de façon à maintenir la qualité de signal mesurée d'après ledit rapport de mesure dans des limites acceptables, caractérisé en ce que le terminal d'utilisateur mobile (12) envoie le rapport (24) quand un critère de rapport prédéterminé est satisfait, et

dans lequel lorsque le terminal d'utilisateur mobile (12) transite (h) d'un état Cell-FACH à un état Cell-DCH, la puissance d'émission initiale vers le terminal d'utilisateur mobile (12) dans l'état Cell-DCH dépend du dernier niveau de puissance d'émission réglé dans l'état Cell-FACH précédent.

2. Procédé selon la revendication 1, dans lequel le critère de rapport prédéterminé est que le changement de la qualité de signal mesurée par rapport à la qualité de signal mesurée (20) du dernier rapport est supérieur à une quantité prédéterminée, (22), sur quoi la puissance d'émission est réglée en conséquence.

3. Procédé selon la revendication 1 ou 2, dans lequel la transition sur l'état Cell-DCH se produit lorsque la puissance d'émission dans l'état Cell-FACH est inférieure à une limite prédéterminée.

4. Procédé selon l'une quelconque des revendications précédentes, dans lequel si une connexion de transfert temporaire est établie, la connexion est établie avec une puissance d'émission initiale depuis la station de base qui est spécifique au terminal d'utilisateur mobile.

5. Procédé selon l'une quelconque des revendications 1 à 4, dans lequel les dernières valeurs paramétriques reçues servent à déterminer si une connexion de transfert temporaire doit être établie ou non lors du transit de l'état Cell-FACH à l'état Cell-DCH.

6. Procédé selon l'une quelconque des revendications 1 à 5, dans lequel un contrôleur de support dynamique dans la station de base (4) alloue un débit de données pour l'état Cell-DCH en fonction des dernières valeurs paramétriques reçues du terminal d'utilisateur mobile (12).

7. Procédé selon l'une quelconque des revendications précédentes, dans lequel le critère de rapport prédéterminé est tel que lorsque la qualité de signal mesurée provenant de la meilleure cellule voisine (33) est inférieure à la qualité de signal mesurée provenant de la cellule de desserte (31) par plus d'une première quantité prédéterminée quand (32) le terminal d'utilisateur mobile est dans une région de transfert temporaire mais dans un état Cell-FACH, la meilleure voisine est supprimée d'une liste de cellules pour la connexion de transfert temporaire dans l'état Cell-FACH.

8. Procédé selon l'une quelconque des revendications précédentes, dans lequel le critère de rapport prédéterminé est tel que lorsque la qualité de signal mesurée provenant de la meilleure cellule voisine (33) est inférieure à la qualité de signal mesurée provenant de la cellule de desserte (31) par moins d'une première quantité prédéterminée quand (30) le terminal d'utilisateur mobile est dans une région de transfert temporaire mais dans un état Cell-FACH, la meilleure voisine est ajoutée à une liste de cellules pour la connexion dans l'état Cell-DCH.

9. Réseau de télécommunications mobiles comprenant une station de base (4) et un terminal d'utilisateur mobile (12),
la station de base (4) servant à envoyer un signal à un premier niveau de puissance d'émission au terminal d'utilisateur mobile sur un Canal d'Accès Aller, FACH,
le terminal d'utilisateur mobile (12) servant à envoyer (d) un rapport de mesure d'une ou de plusieurs valeurs paramétriques dépendant de la qualité de signal mesurée,
la station de base (4) servant à régler (f) sa puissance d'émission vers le terminal d'utilisateur mobile (12) de façon à maintenir la qualité de signal mesurée d'après ledit rapport de mesure dans des limites acceptables, caractérisé en ce que
le terminal d'utilisateur mobile (12) sert à envoyer le rapport (24) quand un critère de rapport prédéterminé est satisfait, sur quoi lorsque le terminal d'utilisateur mobile (12) transite (h) d'un état Cell-FACH à un état Cell-DCH, la puissance d'émission initiale vers le terminal d'utilisateur mobile (12) dans l'état Cell-DCH dépend du dernier niveau de puissance d'émission réglé dans l'état Cell-FACH précédent.

Drawing