EP1457077A2 - Cellular telecommunication network using cells of different sizes, corresponding base station, terminal and method - Google Patents

Cellular telecommunication network using cells of different sizes, corresponding base station, terminal and method

Info

Publication number
EP1457077A2
EP1457077A2 EP02803849A EP02803849A EP1457077A2 EP 1457077 A2 EP1457077 A2 EP 1457077A2 EP 02803849 A EP02803849 A EP 02803849A EP 02803849 A EP02803849 A EP 02803849A EP 1457077 A2 EP1457077 A2 EP 1457077A2
Authority
EP
European Patent Office
Prior art keywords
base station
terminal
synchronization
cell
communication
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02803849A
Other languages
German (de)
French (fr)
Inventor
Antoine Bassompierre
Nathalie Goudard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sierra Wireless SA
Original Assignee
Wavecom SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wavecom SA filed Critical Wavecom SA
Publication of EP1457077A2 publication Critical patent/EP1457077A2/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H04W16/32—Hierarchical cell structures
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/04—Reselecting a cell layer in multi-layered cells

Definitions

  • the present invention relates to the field of cellular radiotelephony. More specifically, the invention relates to the transmission of data, in particular at high bit rates, in a radiotelephony system.
  • the third generation radio systems take or will take into account many services and applications supposing the transmission of data at very high data rates.
  • the resources allocated to data transfers (for example files containing sound and / or still or moving images), in particular via the Internet or similar networks, will represent a preponderant part of the available resource and will probably be higher, in the long term.
  • resources allocated to voice communications which should remain substantially constant.
  • the total throughput available to users of radiotelephony equipment is limited. In order to allow sufficient availability of resources, we have traditionally used, in particular, a densification of cells in a given territory.
  • micro-cells which are relatively small cells (corresponding, for example, to that of an urban district) or even “pico-cells”, which are large cells. even smaller (corresponding, for example, to a street or a building).
  • a disadvantage of this technique is that it requires a multiplication of fixed stations (base station or BS from the English "Base Station”), which are relatively complex and expensive elements.
  • base station or BS base station from the English "Base Station”
  • the possible data rate although high, is not optimal.
  • the more cells, and therefore the fixed stations the more complex the management.
  • the third generation UMTS networks (from the English “Universal Mobile Telecommunications System” or “Universal Mobile Telecommunications System”) have a capacity limited by the power used by broadcast channels.
  • broadcast channel describes the point-to-multi-point type channels, for example of the BCH (“Broadcast Channel”) or PCH (“Paging Channel”) type.
  • pico-cells small cells which are intended for high speed transmission for mobile terminals with geographically reduced mobility (a few hundred meters for example).
  • a first objective of the invention is to increase the overall capacity of a cellular network comprising cells of different sizes and in particular the overall throughput of cells of small sizes (pico-cells or micro-cells), by providing a minimum of modifications to the mobile terminals used.
  • the invention also aims to enable the implementation of equipment intended for third generation mobile communications networks, by requiring little or no modification of the current standards in force and in particular the UMTS FDD (“Frequency Division Duplex”) standard. ) (in particular the 25 series of this standard) defined and distributed by the 3GPP committee (or “Third generation partnership project” from the English “3 rd Generation Partnership Project”).
  • the invention provides a cellular communication network comprising at least a first cell, called a large cell, associated with a first base station and geographically including at least a second cell, called a small cell, associated with it.
  • a network terminal can be in particular in communication mode, when communication is established between the terminal and a remote terminal, and in standby mode, when the terminal is not in communication mode but present and available for communication, in one of the cells of the network, remarkable in that the first base station manages the mode standby for the terminals present in the small cell, the second base station being able to take over the communication mode and implementing a common pilot channel.
  • the cellular network is remarkable in that the first base station manages the opening of a communication for a terminal present in the small cell, then the network transfers the management of the communication to the second station basic.
  • the invention allows in particular a transfer of the management of the communication or "hand- fast "over (ie without listening to the SCH channel) between the large and the small cell even if the frequencies are different (this is a real problem in UMTS to make a hand-over when the frequencies are different) .
  • An advantage of the fast hand-over is that it makes it possible to reduce the duration of use of the compressed mode defined by the 3GPP standard when a fast handover is desired. In this mode, a base station and / or a terminal starts transmitting at relatively high power at a first frequency, which makes it possible to create a vacuum which is used to transmit at a second different frequency. This mode therefore creates annoying interference for the network.
  • the cellular network is remarkable that after the end of the communication, the terminal goes into standby mode and is managed by the first base station.
  • the cellular network is remarkable that the second base station comprises means for synchronization on a synchronization signal emitted by the first base station, by hertzian way (SCH).
  • SCH hertzian way
  • the cellular network is remarkable that the second base station comprises means for synchronization on a synchronization signal transmitted by the first base station, by wire link. According to a particular characteristic, the cellular network is remarkable that the terminal deduces its synchronization on the second base station from that on the first base station.
  • the cellular network is remarkable that the synchronization of the terminal on the second base station is a pseudosynchronization, tolerating synchronization errors of the order of 5 to 30 ⁇ s.
  • the invention allows the use of hardware means usually dedicated to the determination of multiple paths and which are here advantageously used to perform fine and rapid synchronization.
  • the invention allows a simple implementation of the synchronization means not only in the base stations but also in the user terminals.
  • the terminal comprises:
  • the analysis means implementing a step of determining at least one path corresponding to the predetermined signal supplying the synchronization means, the path or one of the paths corresponding to the predetermined signal, called the first path, being considered as the basis for synchronization.
  • the cellular network is remarkable that the synchronization means take account only of the determination of at least one path corresponding to the predetermined signal transmitted by the second base station, the determination being implemented by the means of multipath analysis.
  • the cellular network is remarkable that the predetermined signal is a signal (CPICH) dedicated to the processing of multiple paths and transmitted by the second base station. According to a particular characteristic, the cellular network is remarkable that at least certain cells composing it function asynchronously.
  • CPICH signal
  • the cellular network is remarkable that at least certain cells composing it operate synchronously, with a tolerance for synchronization error between them less than 5 ⁇ s.
  • the small cell comprises means for transmitting a synchronization signal (SCH) allowing the terminal to synchronize with the second base station with a lower error tolerance at 5 ⁇ s.
  • SCH synchronization signal
  • the small cell does not need to synchronize with the large cell but has the drawback of not allowing a rapid "hand-over" and of consuming bandwidth.
  • the invention also relates to a base station, remarkable in that, in a cellular network, the base station, called the first base station, is intended to be associated with a cell called the small cell which is itself intended to be geographically included in a cell, known as a large cell, itself associated with a second base station and geographically encompassing at least a second cell, a network terminal being able to be in particular in communication mode, when a communication is established between the terminal and a remote terminal, and in standby mode, when the terminal is not in communication mode but present and available for communication, in one of the cells of the network, and in that the second base station associated with the large cell manages the standby mode for the terminals present in the small cell, the first base station being able to support com mode munication and implementing a common pilot channel.
  • the base station is remarkable in that it is suitable for high-speed communications.
  • the invention also relates to a terminal intended to cooperate with at least one base station as previously described, remarkable in that the terminal comprises:
  • CPICH predetermined signal
  • the terminal is remarkable in that the first synchronization tolerates synchronization errors of the order of 5 to 30 ⁇ s.
  • the terminal is remarkable in that the second synchronization tolerates synchronization errors of less than 5 ⁇ s.
  • the invention relates to a cellular network management method comprising at least a first cell, called large cell, associated with a first base station and geographically including at least a second cell, called small cell, associated itself at a second base station, a network terminal being able to be in particular in communication mode, when a communication is established between the terminal and a remote terminal, and in standby mode, when the terminal is not in communication mode but present and available for communication, in one of the cells of the network, remarkable in that it comprises the following steps: management of a standby mode by the first base station for the terminals present in the small cell; and support for the communication mode and implementation of a pilot common channel by the second base station.
  • the advantages of the terminal, the base station and the management method are the same as those of the telecommunications network, they are not described in more detail.
  • - Figure 1 shows a network diagram according to the invention according to a particular embodiment
  • - Figure 2 illustrates the network of Figure 1 after establishing communication between a terminal and a base station associated with a micro-cell;
  • - Figure 3 describes a "micro-cell" base station of the network illustrated in Figures 1 and 2; and - Figure 4 illustrates a communication protocol between different network elements allowing the transition from a situation illustrated with reference to Figure 1 to a situation illustrated with respect to Figure 2.
  • a network comprising large cells (for example, macrocells), some of these cells comprising smaller cells (for example micro- or pico-cells).
  • the general principle of the invention is based in particular on a pseudosynchronization of each of the small cells on a macro-cell which encompasses it and on the implementation in small cells of dedicated channel management (transmission of data), but not (or to a limited extent) of the management of common channels (that is to say corresponding to point-to-multipoint links), user terminals (or user equipment also denoted UE of l 'English' User Equipments') being attached to the macro-cell encompassing these small cells, when the user equipment is in standby state.
  • the user terminals are in particular mobile or fixed wireless terminals (for example mobile telephones or any other device (in particular portable computers) comprising a wireless communication system).
  • a user equipment does not connect directly to a pico-cell: in standby mode, if it is present in a pico-cell itself included in a macro-cell, the equipment user is managed by this macro-cell, on which it depends. In particular, it receives the signals transmitted on BCH and PCH channels by a base station of the macro-cell. The picocell is then only accessible to the terminal by a “hand-over”, that is to say by a cell transfer managed and decided by the network.
  • the start of a communication that is to say the opening of the dedicated channel, is done on the macro-cell. Only then does the terminal switch to the pico-cell. The terminal thus does not need the system information normally broadcast by a BCH channel (or “Broadcast Channel”) or equivalent which would be specific to the pico-cell.
  • a BCH channel or “Broadcast Channel”
  • the functionality of the pico-cell is restricted, which in particular does not support a terminal in the standby mode.
  • This restriction of functionality of the pico-cell is not a drawback, because the small cells are mainly intended to manage channels reserved for high speed data transmissions more than for the management of mobiles in standby state, but an advantage, the base station of the picocell being greatly simplified.
  • the terminal At the end of a communication on the pico-cell, the terminal returns to standby mode on the macro-cell.
  • the SCH synchronization channels are not necessary for the “hand-over” from the macro-cell to the pico-cell because, on the one hand, the hand-over is pseudo-synchronous and, on the other hand , the destination cell is a pico-cell therefore of very small size.
  • This “hand-over” can therefore be done directly, for example by looking for echoes on the pilot pico-cell channel (CPICH), the temporal uncertainty being very low.
  • CPICH pilot pico-cell channel
  • the synchronization between the pico-cells and the macro-cell does not need, according to the approach of the invention, significant precision.
  • the channel SCH (“Synchronization Channel”) of the macro-cell to which it is attached.
  • the pico-cell may be pseudo-synchronized on a macro-cell by a wire link between the base stations of each of the two cells.
  • a pico-cell is pseudo synchronized on a macro-cell, a synchronization error of a few “chips” (a “chip” has a duration equal to 0.26 micro-seconds in the UMTS standard) on the synchronization of the terminal on the macro -cell does not pose a problem at the terminal to synchronize on the pico-cell.
  • a pico-cell can implement its own SCH channel which allows asynchronous operation of the pcio-cell with respect to a macro-cell which includes it.
  • the disadvantage of this embodiment is that it involves an asynchronous "hand-over” for the transition from the macro-cell to the pico-cell, that is to say a “hand-over” between two asynchronous cells ".
  • an asynchronous "hand-over” is a procedure that takes time especially when it is a "handover” with frequency change as is the case here.
  • the pilot channel is the only common channel that is essential, it allows the mobile when it is not connected to the pico-cell to see that it is in the coverage area. It also makes it possible to “hand-over” the macrocell to the pico-cell.
  • the invention does not require adapting all the pico-cells of the UMTS networks.
  • certain pico-cells can operate according to the mechanism of the invention, other pico-cells having all the broadcasting channels as proposed by the UMTS standard today in force.
  • the network is for example a network compatible with the standard
  • UMTS Universal Mobile Telecommunication System
  • the network includes a large cell 100 (or “macro-cell”) which is managed by a baselOl station (BS).
  • This cell 100 includes two smaller cells 110 and 120
  • Each of the cells 110 and 120 respectively comprises a base station respectively 111 and 121 capable of managing the communications inside the corresponding cell. It is noted that by way of illustration, several terminals (UE) are present in the cell 100. Some of these terminals are also present in one of the small cells 110 and 120.
  • UE terminals
  • the terminal 112 is inside the cell 110 and can therefore receive or transmit signals from or to the base stations 101 and 111.
  • the terminals 122 and 123 are inside 120 and can therefore receive or transmit signals from or to the base stations 101 and 121.
  • the terminals 102 and 103 present in the cell 100 but not in one of the cells 110 and 120 can or transmit signals coming from or bound for the base station 101 but not from the base stations 111 or 121.
  • the links between the various elements of cell 100 have been shown, at a given time: - in fine dotted lines for the links between base stations; in broad dashed lines for the links between the base station 101 and the terminals in standby state (the terminals 112, 122, 123 and 102 according to the example in FIG. 1); and
  • certain terminals are in standby mode, that is to say in a mode where the terminals are not in communication mode but present and available for communication in one of the cells 100, 110 or 120.
  • These terminals including listening to signals emitted by the base station 101 belonging to the macro-cell 100. These signals are emitted on: common transport channels corresponding to the services offered to the upper layers of the communication protocol, in particular on BCH (or “broadcast channel” from English “Broadcast CHannel”) and PCH (or “mobile search channel” from English “Paging CHannel”); and
  • the terminals are not listening to the dedicated channels.
  • the terminal 103 is not in standby mode since it is in communication with the base station 101 on a dedicated channel DCH (from the English “Dedicated CHannel”) which is both up and down.
  • 3GPP networks are well known to those skilled in the art of mobile networks and are in particular specified in the standard “3 rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical Channels and mapping of transport channels onto physical channels (FDD) release 1999 ”reference 3GPP TS25.211 and distributed by the 3GPP publications office. These channels will therefore not be described more fully.
  • FIG. 2 represents the network of FIG. 1 when a certain time has elapsed and in particular after an establishment of a communication between the terminal 123 and the base station 121 inside the micro-cell 120.
  • the terminal 123 is directly connected to the base station 121 via a dedicated DCH up or down channel allowing the transport of the channel and / or the data exchanged.
  • FIG. 3 schematically illustrates the base station 121 as illustrated with reference to FIGS. 1 and 2.
  • the base station 121 comprises, interconnected by an address and data bus 307:
  • wired network interface 300 allowing a link to a fixed infrastructure of the mobile network or to other networks;
  • a reception radio interface 301 making it possible to receive the signals transmitted by the terminals in communication with the base station 121 on dedicated uplink channels and signals transmitted by the base station 101 in particular on the synchronization channel SCH (from the English “CHannel synchronization”) (note that the current UMTS standards do not provide that the SCH channel is listened to only by user equipment and not by a base station);
  • a transmission radio interface 302 making it possible to transmit signals on dedicated downlink channels and on common transport channels corresponding to the physical layer (and not to the upper layers of the communication protocol) (in particular the CPICH channel); and
  • the RAM 306 stores data, variables 309 and intermediate processing results.
  • the non-volatile memory 305 stores in registers which, for convenience, have the same names as the data they store, in particular:
  • the parameters 311 for configuring the base station 121 are the parameters 311 for configuring the base station 121.
  • the base station 121 is implemented in a simpler manner than the base station 101 and in particular includes a simpler operating program than that of the base station 101 since it does not include the functionality of common channels that the base station 121 does not have to manage.
  • the base station 121 does not synchronize on the SCH channel of the base station
  • the radio reception interface 301 therefore makes it possible to receive the signals transmitted by the terminals in communication with the base station 121 on dedicated uplink channels and does not receive signals transmitted by the base station 101 in particular on the SCH synchronization channel (from “Synchronization CHannel”).
  • the wired network interface 300 allowing a link to a fixed infrastructure of the mobile network or to other networks receives a synchronization signal emitted by the base station 101 on the wired network or on a dedicated link connecting the stations of base 101 and 121.
  • the synchronization signal is implemented according to techniques known to those skilled in the art (for example, pulse according to a certain rhythm or particular bit sequence on which the base station 121 sets its own synchronization). This synchronization signal will therefore not be described further.
  • wired synchronization requires a wired link. However, wired synchronization saves bandwidth on the radio medium and is very reliable by not being subject to radio interference.
  • a terminal not shown, comprises interconnected by an address and data bus: - a processor;
  • a reception radio interface making it possible to synchronize in standby mode on a SCH type signal sent by the base station 101 then, in communication mode, on a CPICH type signal sent by the base station 121 and to receive generally the signals transmitted by the base stations 101 and 121 on dedicated downlink channels;
  • - a transmission radio interface making it possible to transmit signals on dedicated uplink channels and on uplink common transport channels; and - a man / machine interface allowing dialogue with the machine for control and maintenance.
  • FIG. 4 illustrates a communication protocol between the base stations 101 and 121 and the terminal 123 during the transition from the situation illustrated with regard to FIG. 1 where the terminal 123 is in standby mode to a situation illustrated with regard to the figure 2 where the terminal 123 is in communication with the base station 121.
  • the base station 101 transmits a signal 400 on the downlink SCH intended for the base stations and the terminals present in the macro-cell 100 and in particular of the base station 121 and of the terminal 123.
  • the station of base 121 and the terminal 123 (which is, according to FIG. 1, in standby mode) are synchronized on the SCH channel of the base station 101.
  • this signal SCH is transmitted regularly by the base station 101 and that as soon as the pseudo-synchronization of the base station 121 degrades beyond a certain predetermined threshold, the base station 121 resynchronizes on the station basic 101.
  • this delay being for example equal to the propagation time of the signal SCH between the base stations 101 and 121;
  • a “hand-over” signal (signal 405 detailed below) transmitted to the terminal 123 and conveying information indicating the position of the synchronization.
  • the base station 101 also transmits a signal 401 on the BCH channel.
  • This downlink signal indicates to terminal 123 which PCH channel it should listen to. Thus, after reception of this signal, the terminal 123 listens to the PCH channel indicated by the signal 401.
  • the base station 101 transmits a signal to the terminal 123 on the PCH channel indicated by the signal 401, this signal making it possible to detect an incoming call.
  • the terminal 123 transmits a signal 403 on the RACH channel (from the English “Random
  • this signal 403 indicating to the base station 101 that the terminal 103 requests the establishment of a communication. Then, the base station 101 transmits a communication channel allocation signal 404 on the FACH channel (from the English “Fast Access CHannel” which is also a common channel corresponding to a high layer service).
  • the hand-over allowing the passage of a communication from the terminal 123 to the base station 121 is made by decision of the network (in particular of the RNC or "Radio Network Controller" connected to the base stations 101 and 121) in function multiple criteria, in particular the speed, the quality of the communication and the specifics of the base station 121 (in particular the fact that it is well suited to handle high-speed communications).
  • the terminal 123 listens to the pilot channel 406 CPICH which according to the invention makes it possible to refine the synchronization of the terminal 123.
  • the cell 120 is small and that the base station 121 is pseudo-synchronized (by pseudo-synchronization, here is understood a synchronization with an accuracy of less than 50 ⁇ s and preferably less than or equal to 30 ⁇ s) on station 101 (c ' that is to say if the synchronization between the cells 120 and 100 is rough and not perfect, the synchronization error being less than approximately 50 ⁇ s and preferably 30 ⁇ s then in synchronized networks, known per se, the error on the synchronization is less than 5 ⁇ s, the resulting synchronization error between the terminal 123 and the base station 121 can be compensated for by using the signal 406.
  • the terminal 123 comprises means s making it possible to take advantage of the multiple paths affecting a signal transmitted by a base station (This phenomenon of multiple paths is well known to those skilled in the art and is in particular the consequence of reflections on obstacles of a signal transmitted in several directions , the different signals received from the same transmitted signal but having followed different paths are generally of different amplitudes and out of phase). It should be noted that in particular a “rake” type receiver makes it possible to determine the different delays affecting a multi-path signal. Thus, if the delay is not too great (that is to say less than 20 ⁇ s within the framework of the 3GPP standard), the terminal 123 is able to synchronize on the CPICH channel.
  • the receiver of the terminal 123 stalling on this hypothetical path searches for at least one path corresponding to a signal transmitted on the CPICH channel of the base station with the means also used for determining the multiple paths in a signal transmitted on a CPICH channel. This is possible because the synchronization differences between the terminal 123 and each of the base stations 101 and 121 are small. The path or one of the determined paths is then used as the synchronization base for the terminal 123 on the base station 121.
  • the CPICH makes it possible to process multi-paths with a delay of 20 ⁇ s, which makes it possible to compensate for an error when the small cell has a radius less than or equal to approximately 6 km (ie the equal delay of the order here of 20 ⁇ s multiplied by the speed of the light). It is also noted that when it is synchronized with the base station 121, the terminal 123 maintains a servo-control on this synchronization via the CPICH channel managed by the base station 121.
  • the terminal 123 and the base station 121 exchange data on dedicated channels DPCH via several signals 407 to 409 of which a small part has been shown.
  • the terminal 123 and / or the base station 121 indicate via the signal 409 that the communication ends.
  • the network imposes on the terminal a "hand-over" to the base station 101. It is noted that this "hand-over" can be carried out quickly with synchronization on the CPICH signal emitted by the base station 101 since the terminal is synchronized with the base station 121 which is itself pseudo-synchronized with the base station 101.
  • the terminal 123 therefore returns to a standby mode and the situation then becomes that which is illustrated with reference to FIG. 1.
  • the base station 101 then transmits signals 410, 411 and 412 respectively on the SCH, BCH and PCH channels, these signals being similar to the signals 400, 401 and 402 respectively described above.
  • the base station of the small cell can transmit a SCH type signal, the terminals then synchronizing on this signal when they are in communication with this base station.
  • the invention is not limited to UMTS or 3GPP networks but extends to any cellular network in which large cells includes smaller cells.
  • the invention is not limited to a purely material installation but that it can also be implemented in the form of a sequence of instructions of a computer program or any form mixing a material part and a part software.
  • the corresponding sequence of instructions may be stored in a removable storage means (such as for example a floppy disk, a CD-ROM or a DVD-ROM) or no, this storage means being partially or totally readable by a computer or a microprocessor.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The invention concerns a cellular communication network comprising at least a first cell (100), called large-size cell, associated with a first base station (101) and geographically including at least a second cell (12), called small-size cell, itself associated with a second base station (121), the first base station managing standby mode for the terminals (123) present in the small-size cell, the second base station capable of taking over communication mode and using a common pilot channel (CPICH).

Description

Réseau de télécommunication cellulaire mettant en œuvre des cellules de tailles différentes , station de base, terminal et procédé correspondant.Cellular telecommunications network using cells of different sizes, base station, terminal and corresponding method.
La présente invention se rapporte au domaine de la radiotéléphonie cellulaire. Plus précisément, l'invention concerne la transmission de données, en particulier à des débits élevés, dans un système de radiotéléphonie.The present invention relates to the field of cellular radiotelephony. More specifically, the invention relates to the transmission of data, in particular at high bit rates, in a radiotelephony system.
Les systèmes de radiotéléphonie de troisième génération, et les suivants, prennent ou prendront en compte de nombreux services et applications supposant la transmission de données à des débits très élevés. Les ressources allouées aux transferts de données (par exemple des fichiers contenant du son et/ou des images fixes ou animées), notamment via le réseau Internet ou des réseaux similaires, représenteront une part prépondérante de la ressource disponible et seront probablement supérieures, à terme, aux ressources allouées aux communications vocales, qui devraient rester sensiblement constantes. Cependant, le débit total offert aux utilisateurs d'équipement de radiotéléphonie est limité. Afin de permettre une disponibilité suffisante des ressources, on a traditionnellement recourt, notamment, à une densification des cellules sur un territoire donné. On crée ainsi une infrastructure de réseau divisée en « micro-cellules » qui sont des cellules de relativement petite taille (correspondant, par exemple, à celle d'un quartier urbain) voire en « pico- cellules », qui sont des cellules de taille encore plus petite (correspondant, par exemple, à une rue ou un immeuble). Un inconvénient de cette technique est qu'elle nécessite une multiplication des stations fixes (station de base ou BS de l'anglais « Base Station »), qui sont des éléments relativement complexes et coûteux. En outre, le débit de données possible, quoique élevé, n'est pas optimal. De plus, au niveau supérieur, il est clair que plus il y a de cellules, donc de stations fixes, plus la gestion est complexe.The third generation radio systems, and the following ones, take or will take into account many services and applications supposing the transmission of data at very high data rates. The resources allocated to data transfers (for example files containing sound and / or still or moving images), in particular via the Internet or similar networks, will represent a preponderant part of the available resource and will probably be higher, in the long term. , resources allocated to voice communications, which should remain substantially constant. However, the total throughput available to users of radiotelephony equipment is limited. In order to allow sufficient availability of resources, we have traditionally used, in particular, a densification of cells in a given territory. This creates a network infrastructure divided into “micro-cells” which are relatively small cells (corresponding, for example, to that of an urban district) or even “pico-cells”, which are large cells. even smaller (corresponding, for example, to a street or a building). A disadvantage of this technique is that it requires a multiplication of fixed stations (base station or BS from the English "Base Station"), which are relatively complex and expensive elements. In addition, the possible data rate, although high, is not optimal. In addition, at the higher level, it is clear that the more cells, and therefore the fixed stations, the more complex the management.
Par ailleurs, les réseaux de troisième génération UMTS (de l'anglais « Universal Mobile Télécommunication System » ou « Système de Télécommunication Mobile Universel ») ont une capacité limitée par la puissance utilisée par les canaux de diffusion. Le terme « canal de diffusion » décrit les canaux de type point à multi-points, par exemple de type BCH (« Broadcast Channel ») ou PCH (« Paging Channel »).In addition, the third generation UMTS networks (from the English “Universal Mobile Telecommunications System” or “Universal Mobile Telecommunications System”) have a capacity limited by the power used by broadcast channels. The term “broadcast channel” describes the point-to-multi-point type channels, for example of the BCH (“Broadcast Channel”) or PCH (“Paging Channel”) type.
Ce phénomène est particulièrement visible sur les cellules de petite taille (pico-cellules) qui sont prévues pour faire de la transmission à haut débit pour des terminaux mobiles à mobilité géographiquement réduite (quelques centaines de mètres par exemple).This phenomenon is particularly visible on small cells (pico-cells) which are intended for high speed transmission for mobile terminals with geographically reduced mobility (a few hundred meters for example).
L'invention selon ses différents aspects a notamment pour objectif de pallier ces inconvénients de l'art antérieur. Plus précisément, un premier objectif de l'invention est d'augmenter la capacité globale d'un réseau cellulaire comprenant des cellules de différentes tailles et notamment le débit global de cellules de petites tailles (pico-cellules ou micro-cellules), en apportant un minimum de modifications aux terminaux mobiles utilisés. L'invention a également pour objectif de permettre la mise en œuvre des équipements destinés aux réseaux de communications mobiles de troisième génération, en ne nécessitant pas ou peu de modifications des normes actuelles en vigueur et notamment la norme UMTS FDD (« Frequency Division Duplex ») (en particulier la série 25 de cette norme) définie et diffusée par le comité 3GPP (ou « Projet de partenariat pour la troisième génération » de l'anglais « 3rd Génération Partnership Project »).The invention according to its different aspects aims in particular to overcome these drawbacks of the prior art. More specifically, a first objective of the invention is to increase the overall capacity of a cellular network comprising cells of different sizes and in particular the overall throughput of cells of small sizes (pico-cells or micro-cells), by providing a minimum of modifications to the mobile terminals used. The invention also aims to enable the implementation of equipment intended for third generation mobile communications networks, by requiring little or no modification of the current standards in force and in particular the UMTS FDD (“Frequency Division Duplex”) standard. ) (in particular the 25 series of this standard) defined and distributed by the 3GPP committee (or “Third generation partnership project” from the English “3 rd Generation Partnership Project”).
Dans ce but, l'invention propose un réseau de communication cellulaire comprenant au moins une première cellule, dite cellule de grande taille, associée à une première station de base et englobant géographiquement au moins une seconde cellule, dite cellule de petite taille, associée elle-même à une seconde station de base, un terminal du réseau pouvant être notamment en mode communication, lorsqu'une communication est établie entre le terminal et un terminal distant, et en mode veille, lorsque le terminal n'est pas en mode communication mais présent et disponible pour une communication, dans une des cellules du réseau, remarquable en ce que la première station de base gère le mode veille pour les terminaux présents dans la cellule de petite taille, la seconde station de base pouvant prendre en charge le mode communication et mettant en œuvre un canal commun pilote.For this purpose, the invention provides a cellular communication network comprising at least a first cell, called a large cell, associated with a first base station and geographically including at least a second cell, called a small cell, associated with it. - even at a second base station, a network terminal can be in particular in communication mode, when communication is established between the terminal and a remote terminal, and in standby mode, when the terminal is not in communication mode but present and available for communication, in one of the cells of the network, remarkable in that the first base station manages the mode standby for the terminals present in the small cell, the second base station being able to take over the communication mode and implementing a common pilot channel.
Selon une caractéristique particulière, le réseau cellulaire est remarquable en ce que la première station de base gère l'ouverture d'une communication pour un terminal présent dans la cellule de petite taille, puis le réseau transfère la gestion de la communication à la seconde station de base.According to a particular characteristic, the cellular network is remarkable in that the first base station manages the opening of a communication for a terminal present in the small cell, then the network transfers the management of the communication to the second station basic.
Ainsi, selon l'invention, il n'est pas nécessaire que la seconde station de base gère un canal dédié à la synchronisation de type SCBL De cette manière, l'invention permet notamment un transfert de la gestion de la communication ou « hand-over » rapide (c'est-à-dire sans écoute du canal SCH) entre la grande et la petite cellule même si les fréquences sont différentes (cela est un vrai problème en UMTS pour faire un hand-over lorsque les fréquences sont différentes). Un avantage du hand-over rapide est qu'il permet de réduire la durée d'utilisation du mode compressé défini par la norme 3GPP lorsqu'un handover rapide est souhaité. Dans ce mode, une station de base et/ou un terminal se met à émettre à relativement forte puissance à une première fréquence, ce qui permet de créer un vide qui est utilisé pour émettre à une deuxième fréquence différente. Ce mode crée donc des interférences gênantes pour le réseau.Thus, according to the invention, it is not necessary for the second base station to manage a channel dedicated to synchronization of the SCBL type. In this way, the invention allows in particular a transfer of the management of the communication or "hand- fast "over (ie without listening to the SCH channel) between the large and the small cell even if the frequencies are different (this is a real problem in UMTS to make a hand-over when the frequencies are different) . An advantage of the fast hand-over is that it makes it possible to reduce the duration of use of the compressed mode defined by the 3GPP standard when a fast handover is desired. In this mode, a base station and / or a terminal starts transmitting at relatively high power at a first frequency, which makes it possible to create a vacuum which is used to transmit at a second different frequency. This mode therefore creates annoying interference for the network.
Selon une caractéristique particulière, le réseau cellulaire est remarquable qu'après la clôture de la communication, le terminal passe en mode veille et est géré par la première station de base.According to a particular characteristic, the cellular network is remarkable that after the end of the communication, the terminal goes into standby mode and is managed by the first base station.
Selon une caractéristique particulière, le réseau cellulaire est remarquable que la seconde station de base comprend des moyens de synchronisation sur un signal de synchronisation émis par la première station de base, par voie hertzienne (SCH).According to a particular characteristic, the cellular network is remarkable that the second base station comprises means for synchronization on a synchronization signal emitted by the first base station, by hertzian way (SCH).
Selon une caractéristique particulière, le réseau cellulaire est remarquable que la seconde station de base comprend des moyens de synchronisation sur un signal de synchronisation émis par la première station de base, par liaison filaire. Selon une caractéristique particulière, le réseau cellulaire est remarquable que le terminal déduit sa synchronisation sur la seconde station de base de celle sur la première station de base.According to a particular characteristic, the cellular network is remarkable that the second base station comprises means for synchronization on a synchronization signal transmitted by the first base station, by wire link. According to a particular characteristic, the cellular network is remarkable that the terminal deduces its synchronization on the second base station from that on the first base station.
Selon une caractéristique particulière, le réseau cellulaire est remarquable que la synchronisation du terminal sur la seconde station de base est une pseudosynchronisation, tolérant des erreurs de synchronisation de l'ordre de 5 à 30 μs.According to a particular characteristic, the cellular network is remarkable that the synchronization of the terminal on the second base station is a pseudosynchronization, tolerating synchronization errors of the order of 5 to 30 μs.
Ainsi, l'invention permet l'utilisation de moyens matériels habituellement dédiés à la détermination de trajets multiples et qui sont ici avantageusement utilisés pour effectuer une synchronisation fine et rapide. Ainsi, l'invention permet une mise en œuvre simple des moyens de synchronisation non seulement dans les stations de base mais également dans les terminaux d'utilisateurs.Thus, the invention allows the use of hardware means usually dedicated to the determination of multiple paths and which are here advantageously used to perform fine and rapid synchronization. Thus, the invention allows a simple implementation of the synchronization means not only in the base stations but also in the user terminals.
Selon une caractéristique particulière, le réseau cellulaire est remarquable que le terminal comprend :According to a particular characteristic, the cellular network is remarkable that the terminal comprises:
- des moyens d'analyse des trajets multiples subis par un signal prédéterminé émis par la seconde station de base ; etmeans for analyzing the multiple paths undergone by a predetermined signal transmitted by the second base station; and
- des moyens de synchronisation sur le signal prédéterminé émis par la seconde station de base tenant compte de l'analyse des trajets multiples ; les moyens d'analyse mettant en œuvre une étape de détermination d'au moins un trajet correspondant au signal prédéterminé alimentant les moyens de synchronisation, le trajet ou un des trajet correspondant au signal prédéterminé, dit premier trajet, étant considéré comme base de synchronisation..means of synchronization on the predetermined signal transmitted by the second base station taking into account the analysis of the multiple paths; the analysis means implementing a step of determining at least one path corresponding to the predetermined signal supplying the synchronization means, the path or one of the paths corresponding to the predetermined signal, called the first path, being considered as the basis for synchronization. .
Selon une caractéristique particulière, le réseau cellulaire est remarquable que les moyens de synchronisation tiennent compte uniquement de la détermination d'au moins un trajet correspondant au signal prédéterminé émis par la seconde station de base, la détermination étant mise en œuvre par les moyens d'analyse des trajets multiples.According to a particular characteristic, the cellular network is remarkable that the synchronization means take account only of the determination of at least one path corresponding to the predetermined signal transmitted by the second base station, the determination being implemented by the means of multipath analysis.
Selon une caractéristique particulière, le réseau cellulaire est remarquable que le signal prédéterminé est un signal (CPICH) dédié au traitement des trajets multiples et émis par la seconde station de base. Selon une caractéristique particulière, le réseau cellulaire est remarquable qu'au moins certaines cellules le composant fonctionnent de façon asynchrone.According to a particular characteristic, the cellular network is remarkable that the predetermined signal is a signal (CPICH) dedicated to the processing of multiple paths and transmitted by the second base station. According to a particular characteristic, the cellular network is remarkable that at least certain cells composing it function asynchronously.
Selon une caractéristique particulière, le réseau cellulaire est remarquable qu'au moins certaines cellules le composant fonctionnent de façon synchrone, avec une tolérance d'erreur de synchronisation entre elles inférieure à 5 μs.According to a particular characteristic, the cellular network is remarkable that at least certain cells composing it operate synchronously, with a tolerance for synchronization error between them less than 5 μs.
Ainsi, dans un réseau asynchrone, selon l'invention, deux cellules de grande taille ne sont généralement pas synchronisées entre elles. En revanche, les cellules de petite taille peuvent être synchronisées ou pseudo-synchronisées (avec une certaine tolérance) sur la cellule de grande taille qui les englobe. Selon une caractéristique particulière, le réseau cellulaire est remarquable que la cellule de petite taille comprend des moyens d'émission d'un signal de synchronisation (SCH) permettant au terminal de se synchroniser sur la seconde station de base avec une tolérance d'erreur inférieure à 5 μs.Thus, in an asynchronous network, according to the invention, two large cells are generally not synchronized with one another. On the other hand, small cells can be synchronized or pseudo-synchronized (with a certain tolerance) on the large cell which includes them. According to a particular characteristic, the cellular network is remarkable that the small cell comprises means for transmitting a synchronization signal (SCH) allowing the terminal to synchronize with the second base station with a lower error tolerance at 5 μs.
Ainsi, selon cette caractéristique particulière, la petite cellule n'a pas besoin de se synchroniser sur la grande cellule mais présente l'inconvénient de ne pas permettre un « hand-over » rapide et de consommer de la bande passante.Thus, according to this particular characteristic, the small cell does not need to synchronize with the large cell but has the drawback of not allowing a rapid "hand-over" and of consuming bandwidth.
L'invention concerne également une station de base, remarquable en ce que, dans un réseau cellulaire, la station de base, dite première station de base, est destinée à être associée à une cellule dite cellule de petite taille qui est elle-même destinée à être englobée géographiquement dans une cellule, dite cellule de grande taille, associée elle-même à une seconde station de base et englobant géographiquement au moins une seconde cellule, un terminal du réseau pouvant être notamment en mode communication, lorsqu'une communication est établie entre le terminal et un terminal distant, et en mode veille, lorsque le terminal n'est pas en mode communication mais présent et disponible pour une communication, dans une des cellules du réseau, et en ce que la seconde station de base associée à la cellule de grande taille gère le mode veille pour les terminaux présents dans la cellule de petite taille, la première station de base pouvant prendre en charge le mode communication et mettant en œuvre un canal commun pilote. Selon une caractéristique particulière, la station de base est remarquable en ce qu'elle est adaptée aux communications à haut débit.The invention also relates to a base station, remarkable in that, in a cellular network, the base station, called the first base station, is intended to be associated with a cell called the small cell which is itself intended to be geographically included in a cell, known as a large cell, itself associated with a second base station and geographically encompassing at least a second cell, a network terminal being able to be in particular in communication mode, when a communication is established between the terminal and a remote terminal, and in standby mode, when the terminal is not in communication mode but present and available for communication, in one of the cells of the network, and in that the second base station associated with the large cell manages the standby mode for the terminals present in the small cell, the first base station being able to support com mode munication and implementing a common pilot channel. According to a particular characteristic, the base station is remarkable in that it is suitable for high-speed communications.
L'invention concerne, en outre, un terminal destiné à coopérer avec au moins une station de base telle que précédemment décrite, remarquable en ce que le terminal comprend :The invention also relates to a terminal intended to cooperate with at least one base station as previously described, remarkable in that the terminal comprises:
- des moyens de première synchronisation ;- first synchronization means;
- d'analyse des trajets multiples subis par un signal (CPICH) prédéterminé émis par la station de base ; et- analysis of the multiple paths undergone by a predetermined signal (CPICH) transmitted by the base station; and
- des moyens de seconde synchronisation plus fine que la première synchronisation, à partir de l'analyse des trajets multiples.- means of second synchronization finer than the first synchronization, from the analysis of the multiple paths.
Selon une caractéristique particulière, le terminal est remarquable en ce que la première synchronisation tolère des erreurs de synchronisation de l'ordre de 5 à 30 μs.According to a particular characteristic, the terminal is remarkable in that the first synchronization tolerates synchronization errors of the order of 5 to 30 μs.
Selon une caractéristique particulière, le terminal est remarquable en ce que la seconde synchronisation tolère des erreurs de synchronisation inférieures à 5 μs.According to a particular characteristic, the terminal is remarkable in that the second synchronization tolerates synchronization errors of less than 5 μs.
De plus, l'invention concerne un procédé de gestion de réseau cellulaire comprenant au moins une première cellule, dite cellule de grande taille, associée à une première station de base et englobant géographiquement au moins une seconde cellule, dite cellule de petite taille, associée elle-même à une seconde station de base, un terminal du réseau pouvant être notamment en mode communication, lorsqu'une communication est établie entre le terminal et un terminal distant, et en mode veille, lorsque le terminal n'est pas en mode communication mais présent et disponible pour une communication, dans une des cellules du réseau, remarquable en ce qu'il comprend les étapes suivantes : gestion d'un mode veille par la première station de base pour les terminaux présents dans la cellule de petite taille ; et prise en charge du mode de communication et mise en œuvre d'un canal commun pilote par la seconde station de base. Les avantages du terminal, de la station de base et du procédé de gestion sont les mêmes que ceux du réseau de télécommunication, ils ne sont pas détaillés plus amplement.In addition, the invention relates to a cellular network management method comprising at least a first cell, called large cell, associated with a first base station and geographically including at least a second cell, called small cell, associated itself at a second base station, a network terminal being able to be in particular in communication mode, when a communication is established between the terminal and a remote terminal, and in standby mode, when the terminal is not in communication mode but present and available for communication, in one of the cells of the network, remarkable in that it comprises the following steps: management of a standby mode by the first base station for the terminals present in the small cell; and support for the communication mode and implementation of a pilot common channel by the second base station. The advantages of the terminal, the base station and the management method are the same as those of the telecommunications network, they are not described in more detail.
D'autres caractéristiques et avantages de l'invention apparaîtront plus clairement à la lecture de la description suivante d'un mode de réalisation préférentiel, donné à titre de simple exemple illustratif et non limitatif, et des dessins annexés, parmi lesquels :Other characteristics and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given by way of simple illustrative and nonlimiting example, and of the appended drawings, among which:
- la figure 1 présente un synoptique de réseau conforme à l'invention selon un mode particulier de réalisation; - la figure 2 illustre le réseau de la figure 1 après établissement d'une communication entre un terminal et une station de base associée à une micro-cellule;- Figure 1 shows a network diagram according to the invention according to a particular embodiment; - Figure 2 illustrates the network of Figure 1 after establishing communication between a terminal and a base station associated with a micro-cell;
- la figure 3 décrit une station de base de « micro-cellule » du réseau illustré dans les figures 1 et 2; et - la figure 4 illustre un protocole de communication entre différents élément du réseau permettant le passage d'une situation illustrée en regard de la figure 1 à une situation illustrée en regard de la figure 2. On considère, dans le mode de réalisation particulier de l'invention décrit ci-après, un réseau comprenant des cellules de grande taille (par exemple, macrocellules), certaines de ces cellules comprenant des cellules de plus petite taille (par exemple micro- ou pico-cellules).- Figure 3 describes a "micro-cell" base station of the network illustrated in Figures 1 and 2; and - Figure 4 illustrates a communication protocol between different network elements allowing the transition from a situation illustrated with reference to Figure 1 to a situation illustrated with respect to Figure 2. We consider, in the particular embodiment of the invention described below, a network comprising large cells (for example, macrocells), some of these cells comprising smaller cells (for example micro- or pico-cells).
Le principe général de l'invention repose notamment sur une pseudosynchronisation de chacune des cellules de petite taille sur une macro-cellule qui l'englobe et sur la mise en œuvre dans les cellules de petite taille d'une gestion des canaux dédiés (transmission de données), mais non (ou de façon limitée) de la gestion de canaux communs (c'est-à-dire correspondants à des liaisons point à multipoint), les terminaux d'utilisateur (ou équipements d'utilisateur noté également UE de l'anglais « User Equipments ») étant rattachés à la macro-cellule englobant ces cellules de petite taille, lorsque les équipements d'utilisateur sont en état de veille.The general principle of the invention is based in particular on a pseudosynchronization of each of the small cells on a macro-cell which encompasses it and on the implementation in small cells of dedicated channel management (transmission of data), but not (or to a limited extent) of the management of common channels (that is to say corresponding to point-to-multipoint links), user terminals (or user equipment also denoted UE of l 'English' User Equipments') being attached to the macro-cell encompassing these small cells, when the user equipment is in standby state.
On note que les terminaux utilisateurs sont notamment des terminaux mobiles ou fixes sans fil (par exemple des téléphones mobiles ou tout autre appareil (notamment ordinateurs portables) comprenant un système de communication sans fil).It is noted that the user terminals are in particular mobile or fixed wireless terminals (for example mobile telephones or any other device (in particular portable computers) comprising a wireless communication system).
Ainsi, selon l'invention, un équipement d'utilisateur ne se connecte pas directement à une pico-cellule : en mode veille, s'il est présent dans une pico- cellule elle-même incluse dans une macro-cellule, l'équipement d'utilisateur est géré par cette macro-cellule, dont il dépend. Il reçoit notamment les signaux émis sur des canaux BCH et PCH par une station de base de la macro-cellule. La pico- cellule n'est alors accessible au terminal que par un « hand-over », c'est-à-dire par un transfert de cellule géré et décidé par le réseau.Thus, according to the invention, a user equipment does not connect directly to a pico-cell: in standby mode, if it is present in a pico-cell itself included in a macro-cell, the equipment user is managed by this macro-cell, on which it depends. In particular, it receives the signals transmitted on BCH and PCH channels by a base station of the macro-cell. The picocell is then only accessible to the terminal by a “hand-over”, that is to say by a cell transfer managed and decided by the network.
Ainsi, le début d'une communication, c'est-à-dire l'ouverture du canal dédié, se fait sur la macro-cellule. Ce n'est qu'ensuite que le terminal bascule sur la pico-cellule. Le terminal n'a ainsi pas besoin des informations systèmes diffusées normalement par un canal BCH (ou « Broadcast Channel ») ou équivalent qui serait propre à la pico-cellule.Thus, the start of a communication, that is to say the opening of the dedicated channel, is done on the macro-cell. Only then does the terminal switch to the pico-cell. The terminal thus does not need the system information normally broadcast by a BCH channel (or “Broadcast Channel”) or equivalent which would be specific to the pico-cell.
Ainsi, selon l'invention, on restreint les fonctionnalités de la pico-cellule qui ne supporte notamment pas de terminal dans le mode veille. Cette restriction de fonctionnalité de la pico-cellule n'est pas un inconvénient, car les cellules de petite taille sont principalement destinées à gérer des canaux réservés aux transmissions de données à haut débit plus qu'à la gestion de mobiles en état de veille, mais un avantage, la station de base de la pico-cellule étant fortement simplifiée.Thus, according to the invention, the functionality of the pico-cell is restricted, which in particular does not support a terminal in the standby mode. This restriction of functionality of the pico-cell is not a drawback, because the small cells are mainly intended to manage channels reserved for high speed data transmissions more than for the management of mobiles in standby state, but an advantage, the base station of the picocell being greatly simplified.
A la fin d'une communication sur la pico-cellule, le terminal retourne en mode veille sur la macro-cellule.At the end of a communication on the pico-cell, the terminal returns to standby mode on the macro-cell.
Par ailleurs, les canaux de synchronisation SCH ne sont pas nécessaires pour le « hand-over » de la macro-cellule vers la pico-cellule car, d'une part, le hand-over est pseudo-synchrone et, d'autre part, la cellule destination est une pico-cellule donc de taille très faible. Ce « hand-over » peut donc se faire directement, par exemple par une recherche des échos sur le canal pilote de la pico-cellule (CPICH), l'incertitude temporelle étant très faible.Furthermore, the SCH synchronization channels are not necessary for the “hand-over” from the macro-cell to the pico-cell because, on the one hand, the hand-over is pseudo-synchronous and, on the other hand , the destination cell is a pico-cell therefore of very small size. This “hand-over” can therefore be done directly, for example by looking for echoes on the pilot pico-cell channel (CPICH), the temporal uncertainty being very low.
On note que la synchronisation entre les pico-cellules et la macro-cellule n'a pas besoin, selon l'approche de l'invention, d'une précision importante. Ainsi, on peut mettre en oeuvre un mécanisme de pseudo-synchronisation de la pico- cellule sur la macro-cellule basée sur l'écoute par la station de base de la pico- cellule, du canal SCH (« Synchronisation Channel ») de la macro-cellule à laquelle elle est rattachée. Compte tenu des très faibles dérives des références de fréquence des stations de base, il n'est pas nécessaire que la pico-cellule se resynchronise souvent sur la macro-cellule.It is noted that the synchronization between the pico-cells and the macro-cell does not need, according to the approach of the invention, significant precision. Thus, it is possible to implement a mechanism of pseudo-synchronization of the pico-cell on the macro-cell based on the listening by the base station of the pico-cell, of the channel SCH (“Synchronization Channel”) of the macro-cell to which it is attached. Taking into account the very small drifts of the frequency references of the base stations, it is not necessary that the pico-cell often resynchronizes on the macro-cell.
Selon une variante, la pico-cellule peut-être pseudo-synchronisée sur une macro-cellule par une liaison filaire entre les stations de base de chacune des deux cellules. Lorsque une pico-cellule est pseudo synchronisée sur une macro-cellule, une erreur de synchronisation de quelques « chips » (un « chip » a une durée égale à 0.26 micro-secondes dans la norme UMTS) sur la synchronisation du terminal sur la macro-cellule ne pose pas de problème au terminal pour se synchroniser sur la pico-cellule. Selon une autre variante de l'invention, une pico-cellule peut mettre en œuvre son propre canal SCH ce qui permet un fonctionnement asynchrone de la pcio-cellule par rapport à une macro-cellule qui l'englobe. L'inconvénient de ce mode de réalisation est que cela implique un « hand-over » asynchrone pour le passage de la macro-cellule à la pico-cellule, c'est-à-dire un « hand-over » entre deux cellules asynchrones ». Or, un « hand-over » asynchrone est une procédure qui prend du temps surtout quand il s'agit d'un « handover » avec changement de fréquence comme c'est le cas ici.According to a variant, the pico-cell may be pseudo-synchronized on a macro-cell by a wire link between the base stations of each of the two cells. When a pico-cell is pseudo synchronized on a macro-cell, a synchronization error of a few “chips” (a “chip” has a duration equal to 0.26 micro-seconds in the UMTS standard) on the synchronization of the terminal on the macro -cell does not pose a problem at the terminal to synchronize on the pico-cell. According to another variant of the invention, a pico-cell can implement its own SCH channel which allows asynchronous operation of the pcio-cell with respect to a macro-cell which includes it. The disadvantage of this embodiment is that it involves an asynchronous "hand-over" for the transition from the macro-cell to the pico-cell, that is to say a "hand-over" between two asynchronous cells ". However, an asynchronous "hand-over" is a procedure that takes time especially when it is a "handover" with frequency change as is the case here.
Le canal pilote est le seul canal commun qui soit indispensable, il permet au mobile lorsqu'il n'est pas connecté à la pico-cellule de voir qu'il est dans la zone de couverture. Il permet également de faire le « hand-over » de la macrocellule vers la pico-cellule.The pilot channel is the only common channel that is essential, it allows the mobile when it is not connected to the pico-cell to see that it is in the coverage area. It also makes it possible to “hand-over” the macrocell to the pico-cell.
Le principe général d'asynchronisme du réseau UMTS n'est cependant pas complètement modifié. Seules les pico-cellules fonctionnant dans le mode décrit précédemment sont pseudo-synchrones de la macro-cellule dont elles dépendent.The general principle of asynchronism of the UMTS network is not however completely modified. Only the pico-cells operating in the mode described above are pseudo-synchronous with the macro-cell on which they depend.
Ainsi, deux pico-cellules dépendant de macro-cellules différentes ne sont pas synchrones.Thus, two pico-cells depending on different macro-cells are not synchronous.
Il est important de noter que l'invention ne nécessite pas d'adapter toutes les pico-cellules des réseaux UMTS. Sur un même réseau, certaines pico-cellules peuvent fonctionner suivant le mécanisme de l'invention, d'autres pico-cellules ayant tous les canaux de diffusion comme proposé par la norme UMTS aujourd'hui en vigueur.It is important to note that the invention does not require adapting all the pico-cells of the UMTS networks. On the same network, certain pico-cells can operate according to the mechanism of the invention, other pico-cells having all the broadcasting channels as proposed by the UMTS standard today in force.
On présente, en relation avec la figure 1, un synoptique de réseau de radiotéléphonie mobile mettant en œuvre l'invention. Le réseau est par exemple un réseau compatible avec la normeReferring to FIG. 1, a block diagram of a mobile radio network implementing the invention is presented. The network is for example a network compatible with the standard
UMTS(« Universal Mobile Télécommunication System ») définie par le comité 3GPP.UMTS ("Universal Mobile Telecommunication System") defined by the 3GPP committee.
Le réseau comprend une cellule de grande taille 100 (ou « macro-cellule ») qui est gérée par une station de baselOl (BS). Cette cellule 100 englobe deux cellules 110 et 120 de plus petite tailleThe network includes a large cell 100 (or “macro-cell”) which is managed by a baselOl station (BS). This cell 100 includes two smaller cells 110 and 120
(« micro-cellule » ou « pico-cellule »).("Micro-cell" or "pico-cell").
Chacune des cellules 110 et 120 comprend respectivement une station de base respectivement 111 et 121 pouvant gérer les communications à l'intérieur de la cellule correspondante. On note qu'à titre illustratif, plusieurs terminaux (UE) sont présents dans la cellule 100. Certains de ces terminaux sont aussi présents dans l'une des cellules 110 et 120 de petite taille.Each of the cells 110 and 120 respectively comprises a base station respectively 111 and 121 capable of managing the communications inside the corresponding cell. It is noted that by way of illustration, several terminals (UE) are present in the cell 100. Some of these terminals are also present in one of the small cells 110 and 120.
Ainsi, le terminal 112 est à l'intérieur de la cellule 110 et peut donc recevoir ou émettre des signaux en provenance ou à destination des stations de base 101 et 111. De même, les terminaux 122 et 123 sont à l'intérieur 120 et peuvent donc recevoir ou émettre des signaux en provenance ou à destination des stations de base 101 et 121.Thus, the terminal 112 is inside the cell 110 and can therefore receive or transmit signals from or to the base stations 101 and 111. Similarly, the terminals 122 and 123 are inside 120 and can therefore receive or transmit signals from or to the base stations 101 and 121.
Néanmoins, les terminaux 102 et 103 présents dans la cellule 100 mais non dans l'une des cellules 110 et 120 peuvent ou émettre des signaux en provenance ou à destination de la station de base 101 mais non des stations de base 111 ou 121.Nevertheless, the terminals 102 and 103 present in the cell 100 but not in one of the cells 110 and 120 can or transmit signals coming from or bound for the base station 101 but not from the base stations 111 or 121.
Sur la figure 1, les liaisons entre les différents éléments de la cellule 100 ont été représentées, à un instant donné : - en traits pointillés fins pour les liaisons entre stations de base ; en traits pointillés larges pour les liaisons entre la station de base 101 et les terminaux en états de veille (les terminaux 112, 122, 123 et 102 selon l'exemple de la figure 1) ; etIn FIG. 1, the links between the various elements of cell 100 have been shown, at a given time: - in fine dotted lines for the links between base stations; in broad dashed lines for the links between the base station 101 and the terminals in standby state (the terminals 112, 122, 123 and 102 according to the example in FIG. 1); and
- en traits pleins pour les liaisons de communication (liaison entre le terminal 103 et la station de base 101).- in solid lines for the communication links (connection between the terminal 103 and the base station 101).
On note qu'ainsi certains terminaux sont en mode veille, c'est-à-dire dans un mode où les terminaux ne sont pas en mode communication mais présents et disponibles pour une communication dans une des cellules 100, 110 ou 120. Ces terminaux dont notamment à l'écoute de signaux émis par la station de base 101 appartenant à la macro-cellule 100. Ces signaux sont émis sur : des canaux de transport communs correspondant aux services offerts vers les couches hautes du protocole de communication, notamment sur des canaux BCH ( ou « canal de diffusion » de l'anglais « Broadcast CHannel ») et PCH (ou « canal de recherche de mobile » de l'anglais « Paging CHannel ») ; etIt is noted that thus certain terminals are in standby mode, that is to say in a mode where the terminals are not in communication mode but present and available for communication in one of the cells 100, 110 or 120. These terminals including listening to signals emitted by the base station 101 belonging to the macro-cell 100. These signals are emitted on: common transport channels corresponding to the services offered to the upper layers of the communication protocol, in particular on BCH (or "broadcast channel" from English "Broadcast CHannel") and PCH (or "mobile search channel" from English "Paging CHannel"); and
- des canaux de transport communs correspondants à la couche physique du protocole de communication, notamment sur des canaux CPICH (ou « canal commun pilote » de l'anglais « Common Pllot CHannel »).- common transport channels corresponding to the physical layer of the communication protocol, in particular on CPICH channels (or “pilot common channel” from the English “Common Pllot CHannel”).
On note également qu'en mode veille, les terminaux ne sont pas à l'écoute des canaux dédiés. En revanche, le terminal 103 n'est pas en mode veille puisqu'il est en communication avec la station de base 101 sur un canal dédié DCH (de l'anglais « Dedicated CHannel ») qui est à la fois montant et descendant.We also note that in standby mode, the terminals are not listening to the dedicated channels. On the other hand, the terminal 103 is not in standby mode since it is in communication with the base station 101 on a dedicated channel DCH (from the English “Dedicated CHannel”) which is both up and down.
Les canaux utilisés par les réseaux 3GPP sont bien connus de l'homme du métier des réseaux mobiles et sont notamment spécifiés dans la norme « 3rd Génération Partnership Project ; Technical Spécification Group Radio Access Network ; Physical Channels and mapping of transport channels onto physical channels (FDD) release 1999 » de référence 3GPP TS25.211 et diffusée par le bureau des publications de 3GPP. Ces canaux ne seront donc pas décrits plus amplement.The channels used by 3GPP networks are well known to those skilled in the art of mobile networks and are in particular specified in the standard “3 rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical Channels and mapping of transport channels onto physical channels (FDD) release 1999 ”reference 3GPP TS25.211 and distributed by the 3GPP publications office. These channels will therefore not be described more fully.
La figure 2 représente le réseau de la figure 1 lorsqu'un certain temps s'est écoulé et notamment après un établissement d'une communication entre le terminal 123 et la station de base 121 à l'intérieur de la micro-cellule 120.FIG. 2 represents the network of FIG. 1 when a certain time has elapsed and in particular after an establishment of a communication between the terminal 123 and the base station 121 inside the micro-cell 120.
On note que selon la figure 2, le terminal 123 est directement relié à la station de base 121 par l'intermédiaire d'un canal dédié DCH montant ou descendant permettant le transport de la voie et/ou des données échangées.Note that according to Figure 2, the terminal 123 is directly connected to the base station 121 via a dedicated DCH up or down channel allowing the transport of the channel and / or the data exchanged.
La figure 3 illustre schématiquement la station de base 121 telle qu'illustrée en regard des figures 1 et 2.FIG. 3 schematically illustrates the base station 121 as illustrated with reference to FIGS. 1 and 2.
La station de base 121 comprend, reliés entre eux par un bus d'adresses et de données 307 :The base station 121 comprises, interconnected by an address and data bus 307:
- un processeur 304 ;- a processor 304;
- une mémoire vive 306 ;- a random access memory 306;
- une mémoire non volatile 305 ;- a non-volatile memory 305;
- une interface réseau filaire 300 permettant une liaison vers une infrastucture fixe du réseau mobile ou vers d'autres réseaux;- a wired network interface 300 allowing a link to a fixed infrastructure of the mobile network or to other networks;
- une interface radio de réception 301 permettant de recevoir les signaux émis par les terminaux en communication avec la station de base 121 sur des canaux montants dédiés et des signaux émis par la station de base 101 notamment sur le canal de synchronisation SCH (de l'anglais « Synchronisation CHannel ») (on note que les normes UMTS actuelles ne prévoient que le canal SCH soit écouté uniquement par des équipements d'utilisateurs et non par une station de base) ;a reception radio interface 301 making it possible to receive the signals transmitted by the terminals in communication with the base station 121 on dedicated uplink channels and signals transmitted by the base station 101 in particular on the synchronization channel SCH (from the English “CHannel synchronization”) (note that the current UMTS standards do not provide that the SCH channel is listened to only by user equipment and not by a base station);
- une interface radio d'émission 302 permettant d'émettre des signaux sur des canaux dédiés descendant et sur des canaux de transport communs correspondant à la couche physique (et non aux couches supérieures du protocole de communication) (notamment canal CPICH) ; eta transmission radio interface 302 making it possible to transmit signals on dedicated downlink channels and on common transport channels corresponding to the physical layer (and not to the upper layers of the communication protocol) (in particular the CPICH channel); and
- une interface homme/machine 303 permettant un dialogue avec la machine pour le contrôle et la maintenance.- a man / machine interface 303 allowing a dialogue with the machine for control and maintenance.
La mémoire vive 306 conserve des données, des variables 309 et des résultats intermédiaires de traitement.The RAM 306 stores data, variables 309 and intermediate processing results.
La mémoire non volatile 305 conserve dans des registres qui par commodité possèdent les mêmes noms que les données qu'ils conservent, notamment :The non-volatile memory 305 stores in registers which, for convenience, have the same names as the data they store, in particular:
- le programme de fonctionnement du processeur 304 dans un registre « prog » 310 etthe operating program of processor 304 in a “prog” register 310 and
- les paramètres 311 de configuration de la station de base 121.the parameters 311 for configuring the base station 121.
On note que la station de base 121 est mise en œuvre de manière plus simple que la station de base 101 et comprend notamment un programme de fonctionnement plus simple que celui de la station de base 101 car n'incluant pas les fonctionnalités de canaux communs que la station de base 121 n'a pas à gérer.It is noted that the base station 121 is implemented in a simpler manner than the base station 101 and in particular includes a simpler operating program than that of the base station 101 since it does not include the functionality of common channels that the base station 121 does not have to manage.
Selon une variante de réalisation de l'invention décrite à la figure 3, la station de base 121 ne se synchronise pas sur le canal SCH de la station de baseAccording to an alternative embodiment of the invention described in FIG. 3, the base station 121 does not synchronize on the SCH channel of the base station
101. Selon cette variante, l'interface radio de réception 301 permet donc de recevoir les signaux émis par les terminaux en communication avec la station de base 121 sur des canaux montants dédiés et ne reçoit pas des signaux émis par la station de base 101 notamment sur le canal de synchronisation SCH (de l'anglais « Synchronisation CHannel »). En outre, l'interface réseau filaire 300 permettant une liaison vers une infrastructure fixe du réseau mobile ou vers d'autres réseaux reçoit un signal de synchronisation émis par la station de base 101 sur le réseau filaire ou sur une liaison dédiée reliant les stations de base 101 et 121. Le signal de synchronisation est mis en œuvre selon des techniques connues de l'homme du métier (par exemple, impulsion suivant un certain rythme ou suite de bits particulière sur laquelle la station de base 121 cale sa propre synchronisation). Ce signal de synchronisation ne sera donc pas décrit davantage. On note que la synchronisation filaire nécessite une liaison filaire. En revanche, la synchronisation filaire permet une économie de bande passante sur le médium radio et est très fiable en n'étant pas soumise aux interférences radio.101. According to this variant, the radio reception interface 301 therefore makes it possible to receive the signals transmitted by the terminals in communication with the base station 121 on dedicated uplink channels and does not receive signals transmitted by the base station 101 in particular on the SCH synchronization channel (from “Synchronization CHannel”). In addition, the wired network interface 300 allowing a link to a fixed infrastructure of the mobile network or to other networks receives a synchronization signal emitted by the base station 101 on the wired network or on a dedicated link connecting the stations of base 101 and 121. The synchronization signal is implemented according to techniques known to those skilled in the art (for example, pulse according to a certain rhythm or particular bit sequence on which the base station 121 sets its own synchronization). This synchronization signal will therefore not be described further. Note that wired synchronization requires a wired link. However, wired synchronization saves bandwidth on the radio medium and is very reliable by not being subject to radio interference.
On note qu'un terminal non représenté comprend reliés entre eux par un bus d'adresses et de données : - un processeur ;It should be noted that a terminal, not shown, comprises interconnected by an address and data bus: - a processor;
- une mémoire vive ; o- a random access memory; o
- une mémoire non volatile ;- non-volatile memory;
- une interface radio de réception permettant de se synchroniser en mode veille sur un signal de type SCH émis par la station de base 101 puis, en mode communication, sur un signal de type CPICH émis par la station de base 121 et de recevoir d'une manière générale les signaux émis par les stations de base 101 et 121 sur des canaux descendants dédiés;a reception radio interface making it possible to synchronize in standby mode on a SCH type signal sent by the base station 101 then, in communication mode, on a CPICH type signal sent by the base station 121 and to receive generally the signals transmitted by the base stations 101 and 121 on dedicated downlink channels;
- une interface radio d'émission permettant d'émettre des signaux sur des canaux dédiés montants et sur des canaux de transport communs montants; et - une interface homme/machine permettant un dialogue avec la machine pour le contrôle et la maintenance.- a transmission radio interface making it possible to transmit signals on dedicated uplink channels and on uplink common transport channels; and - a man / machine interface allowing dialogue with the machine for control and maintenance.
La figure 4 illustre un protocole de communication entre les stations de base 101 et 121 et le terminal 123 lors du passage de la situation illustrée en regard de la figure 1 où le terminal 123 est en mode veille à une situation illustrée en regard de la figure 2 où le terminal 123 est en communication avec la station de base 121.FIG. 4 illustrates a communication protocol between the base stations 101 and 121 and the terminal 123 during the transition from the situation illustrated with regard to FIG. 1 where the terminal 123 is in standby mode to a situation illustrated with regard to the figure 2 where the terminal 123 is in communication with the base station 121.
La station de base 101 émet un signal 400 sur le canal descendant SCH à destination des stations de bases et des terminaux présents dans la macro-cellule 100 et notamment de la station de base 121 et du terminal 123. Ainsi, la station de base 121 et le terminal 123 (qui est, selon la figure 1, en mode veille) sont synchronisés sur le canal SCH de la station de base 101.The base station 101 transmits a signal 400 on the downlink SCH intended for the base stations and the terminals present in the macro-cell 100 and in particular of the base station 121 and of the terminal 123. Thus, the station of base 121 and the terminal 123 (which is, according to FIG. 1, in standby mode) are synchronized on the SCH channel of the base station 101.
On note que ce signal SCH est émis régulièrement par la station de base 101 et que dès que la pseudo-synchronisation de la station de base 121 se dégrade au delà d'un certain seuil prédéterminé, la station de base 121 se resynchronise sur la station de base 101.It is noted that this signal SCH is transmitted regularly by the base station 101 and that as soon as the pseudo-synchronization of the base station 121 degrades beyond a certain predetermined threshold, the base station 121 resynchronizes on the station basic 101.
On note également que le fait que les stations de base 101 et 121 soient fixes et donc que le délai de propagation du signal entre ces deux stations est connu. On peut ainsi utiliser la connaissance de ce délai de propagation pour améliorer la synchronisation du terminal sur la station de base 121 en mettant en œuvre :It should also be noted that the fact that the base stations 101 and 121 are fixed and therefore that the delay in propagation of the signal between these two stations is known. It is thus possible to use the knowledge of this propagation delay to improve the synchronization of the terminal on the base station 121 by implementing:
- un retard de synchronisation de la station de base 121 par rapport au signal SCH émis par la station de base 101, ce retard étant par exemple égal au temps de propagation du signal SCH entre les stations de base 101 et 121 ; et/oua delay in synchronization of the base station 121 with respect to the signal SCH transmitted by the base station 101, this delay being for example equal to the propagation time of the signal SCH between the base stations 101 and 121; and or
- un signal de « hand-over » (signal 405 détaillé plus loin) émis vers le terminal 123 et véhiculant une information indiquant la position de la synchronisation.a “hand-over” signal (signal 405 detailed below) transmitted to the terminal 123 and conveying information indicating the position of the synchronization.
La station de base 101 émet également un signal 401 sur le canal BCH. Ce signal descendant indique au terminal 123 quel canal PCH il doit écouter. Ainsi, après réception de ce signal, le terminal 123 se met en écoute du canal PCH indiqué par le signal 401.The base station 101 also transmits a signal 401 on the BCH channel. This downlink signal indicates to terminal 123 which PCH channel it should listen to. Thus, after reception of this signal, the terminal 123 listens to the PCH channel indicated by the signal 401.
Puis, la station de base 101 émet un signal à destination du terminal 123 sur le canal PCH indiqué par le signal 401, ce signal permettant de détecter un appel entrant.Then, the base station 101 transmits a signal to the terminal 123 on the PCH channel indicated by the signal 401, this signal making it possible to detect an incoming call.
Ensuite, en supposant que le terminal 123 désire initialiser une communication, il émet un signal 403 sur le canal RACH (de l'anglais « RandomThen, assuming that the terminal 123 wishes to initiate a communication, it transmits a signal 403 on the RACH channel (from the English “Random
Access CHannel » qui est un canal commun correspondant à un service de couche haute d'accès au canal), ce signal 403 indiquant à la station de base 101 que le terminal 103 demande l'établissement d'une communication. Puis, la station de base 101 émet un signal 404 d'allocation de canal de communication sur le canal FACH (de l'anglais « Fast Access CHannel » qui est également un canal commun correspondant à un service de couche haute).Access CHannel ”(which is a common channel corresponding to a high layer service of access to the channel), this signal 403 indicating to the base station 101 that the terminal 103 requests the establishment of a communication. Then, the base station 101 transmits a communication channel allocation signal 404 on the FACH channel (from the English “Fast Access CHannel” which is also a common channel corresponding to a high layer service).
Ensuite, la communication s'établit entre le terminal 123 et la station de base 101. Un ou plusieurs signaux 405 contenant des données correspondant à une application du terminal puis des données de contrôle dédiées au handover sont ainsi échangées sur le canal bidirectionnel DPCH.Then, communication is established between the terminal 123 and the base station 101. One or more signals 405 containing data corresponding to an application of the terminal and then control data dedicated to the handover are thus exchanged on the bidirectional channel DPCH.
On note que le hand-over permettant le passage d'une communication du terminal 123 vers la station de base 121 se fait sur décision du réseau (notamment du RNC ou « Radio Network Controller » relié aux stations de base 101 et 121) en fonction de critères multiples, notamment le débit, la qualité de la communication et les spécificités de la station de base 121 (notamment le fait qu'elle est bien adaptée à gérer les communications à haut débit).It is noted that the hand-over allowing the passage of a communication from the terminal 123 to the base station 121 is made by decision of the network (in particular of the RNC or "Radio Network Controller" connected to the base stations 101 and 121) in function multiple criteria, in particular the speed, the quality of the communication and the specifics of the base station 121 (in particular the fact that it is well suited to handle high-speed communications).
La situation du réseau devient alors celle illustrée en regard de la figure 2. Puis, le terminal 123 se met en écoute du canal pilote 406 CPICH qui permet selon l'invention d'affiner la synchronisation du terminal 123. En effet, si la cellule 120 est de petite taille et que la station de base 121 est pseudo- synchronisée (par pseudo-synchronisation, on entend ici une synchronisation avec une précision inférieure à 50 μs et préférentiellement inférieure ou égale à 30 μs) sur la station 101 (c'est-à-dire si la synchronisation entre les cellules 120 et 100 est grossière et non parfaite, l'erreur de synchronisation étant inférieure à environ 50 μs et préférentiellement 30 μs alors dans les réseaux synchronisés, connus en soi, l'erreur sur la synchronisation est inférieure à 5 μs, l'erreur de synchronisation résultante entre le terminal 123 et la station de base 121 peut être compensée par utilisation du signal 406. En effet, le terminal 123 comprend des moyens permettant de tirer partie des trajets multiples affectant un signal émis par une station de base (Ce phénomène de trajets multiples est bien connu de l'homme du métier et est notamment la conséquence de réflexions sur des obstacles d'un signal émis dans plusieurs directions, les différents signaux reçus issus d'un même signal émis mais ayant suivis différents trajets sont généralement d'amplitudes différentes et déphasés). On note qu'en particulier un récepteur de type « rake » permet de déterminer les différents retards affectant un signal multi- trajet. Ainsi, si le retard n'est pas trop important (c'est-à-dire inférieur à 20 μs dans le cadre de la norme 3GPP), le terminal 123 est capable de se synchroniser sur le canal CPICH.The network situation then becomes that illustrated with reference to FIG. 2. Then, the terminal 123 listens to the pilot channel 406 CPICH which according to the invention makes it possible to refine the synchronization of the terminal 123. In fact, if the cell 120 is small and that the base station 121 is pseudo-synchronized (by pseudo-synchronization, here is understood a synchronization with an accuracy of less than 50 μs and preferably less than or equal to 30 μs) on station 101 (c ' that is to say if the synchronization between the cells 120 and 100 is rough and not perfect, the synchronization error being less than approximately 50 μs and preferably 30 μs then in synchronized networks, known per se, the error on the synchronization is less than 5 μs, the resulting synchronization error between the terminal 123 and the base station 121 can be compensated for by using the signal 406. In fact, the terminal 123 comprises means s making it possible to take advantage of the multiple paths affecting a signal transmitted by a base station (This phenomenon of multiple paths is well known to those skilled in the art and is in particular the consequence of reflections on obstacles of a signal transmitted in several directions , the different signals received from the same transmitted signal but having followed different paths are generally of different amplitudes and out of phase). It should be noted that in particular a “rake” type receiver makes it possible to determine the different delays affecting a multi-path signal. Thus, if the delay is not too great (that is to say less than 20 μs within the framework of the 3GPP standard), the terminal 123 is able to synchronize on the CPICH channel.
Ainsi, en considérant qu'un premier trajet se situe à un instant précis fonction de la synchronisation avec la station de base 101, le récepteur du terminal 123 se calant sur ce trajet hypothétique cherche au moins un trajet correspondant à un signal émis sur canal CPICH de la station de base avec les moyens utilisés par ailleurs pour la détermination des trajets multiples dans un signal émis sur un canal CPICH. Ceci est possible car les écarts de synchronisation entre le terminal 123 et chacune des stations de base 101 et 121 sont faibles. Le trajet ou l'un des trajets déterminés est utilisé alors comme base de synchronisation du terminal 123 sur la station de base 121. On note que, dans le cadre de 3GPP, le CPICH permet de traiter des multitrajets avec un retard de 20 μs, ce qui permet de compenser une erreur lorsque la cellule de petite taille possède un rayon inférieur ou égal à environ 6 km (soit le retard égal de l'ordre ici de 20 μs multiplié par la célérité de la lumière). On note également que lorsqu'il est synchronisé sur la station de base 121, le terminal 123 maintient un asservissement sur cette synchronisation par l'intermédiaire du canal CPICH géré par la station de base 121.Thus, by considering that a first path is located at a precise instant as a function of synchronization with the base station 101, the receiver of the terminal 123 stalling on this hypothetical path searches for at least one path corresponding to a signal transmitted on the CPICH channel of the base station with the means also used for determining the multiple paths in a signal transmitted on a CPICH channel. This is possible because the synchronization differences between the terminal 123 and each of the base stations 101 and 121 are small. The path or one of the determined paths is then used as the synchronization base for the terminal 123 on the base station 121. It is noted that, within the framework of 3GPP, the CPICH makes it possible to process multi-paths with a delay of 20 μs, which makes it possible to compensate for an error when the small cell has a radius less than or equal to approximately 6 km (ie the equal delay of the order here of 20 μs multiplied by the speed of the light). It is also noted that when it is synchronized with the base station 121, the terminal 123 maintains a servo-control on this synchronization via the CPICH channel managed by the base station 121.
Ensuite, le terminal 123 et la station de base 121 échangent des données sur des canaux dédiés DPCH par l'intermédiaire de plusieurs signaux 407 à 409 dont une petite partie a été représentée.Then, the terminal 123 and the base station 121 exchange data on dedicated channels DPCH via several signals 407 to 409 of which a small part has been shown.
En fin de communication, le terminal 123 et/ou la station de base 121 indiquent par l'intermédiaire du signal 409 que la communication se termine.At the end of the communication, the terminal 123 and / or the base station 121 indicate via the signal 409 that the communication ends.
Selon une variante non représentée, avant la fin de la communication le réseau impose au terminal un « hand-over » vers la station de base 101. On note que cet « hand-over » peut être effectué rapidement avec synchronisation sur le signal CPICH émis par la station de base 101 puisque le terminal est synchronisé sur la station de base 121 qui est elle-même pseudo-synchronisée sur la station de base 101.According to a variant not shown, before the end of the communication the network imposes on the terminal a "hand-over" to the base station 101. It is noted that this "hand-over" can be carried out quickly with synchronization on the CPICH signal emitted by the base station 101 since the terminal is synchronized with the base station 121 which is itself pseudo-synchronized with the base station 101.
Le terminal 123 retourne donc dans un mode veille et la situation redevient alors celle qui est illustrée en regard de la figure 1.The terminal 123 therefore returns to a standby mode and the situation then becomes that which is illustrated with reference to FIG. 1.
La station de base 101 émet alors des signaux respectivement 410, 411 et 412 sur les canaux SCH, BCH et PCH, ces signaux étant similaires aux signaux respectivement 400, 401 et 402 décrits précédemment.The base station 101 then transmits signals 410, 411 and 412 respectively on the SCH, BCH and PCH channels, these signals being similar to the signals 400, 401 and 402 respectively described above.
Bien entendu, l'invention n'est pas limitée aux exemples de réalisation mentionnés ci-dessus.Of course, the invention is not limited to the embodiments mentioned above.
En particulier, l'homme du métier pourra apporter toute variante dans la définition des canaux qui ne sont pas supportés par la cellule de petite taille.In particular, the person skilled in the art can make any variant in the definition of the channels which are not supported by the small cell.
Ainsi, on pourra considérer que la station de base de la cellule de petite taille peut émettre un signal de type SCH, les terminaux se synchronisant alors sur ce signal lorsqu'ils sont en communication avec cette station de base.Thus, it can be considered that the base station of the small cell can transmit a SCH type signal, the terminals then synchronizing on this signal when they are in communication with this base station.
On note que l'invention ne se limite pas aux réseaux UMTS ou 3GPP mais s'étend à tout réseau cellulaire dans lequel des cellules de grandes taille englobe des cellules de taille plus petite.It should be noted that the invention is not limited to UMTS or 3GPP networks but extends to any cellular network in which large cells includes smaller cells.
On notera que l'invention ne se limite pas à une implantation purement matérielle mais qu'elle peut aussi être mise en œuvre sous la forme d'une séquence d'instructions d'un programme informatique ou toute forme mixant une partie matérielle et une partie logicielle. Dans le cas où l'invention est implantée partiellement ou totalement sous forme logicielle, la séquence d'instructions correspondante pourra être stockée dans un moyen de stockage amovible (tel que par exemple une disquette, un CD-ROM ou un DVD-ROM) ou non, ce moyen de stockage étant lisible partiellement ou totalement par un ordinateur ou un microprocesseur. It will be noted that the invention is not limited to a purely material installation but that it can also be implemented in the form of a sequence of instructions of a computer program or any form mixing a material part and a part software. In the case where the invention is implemented partially or completely in software form, the corresponding sequence of instructions may be stored in a removable storage means (such as for example a floppy disk, a CD-ROM or a DVD-ROM) or no, this storage means being partially or totally readable by a computer or a microprocessor.

Claims

REVENDICATIONS
1. Réseau de communication cellulaire comprenant au moins une première cellule (100), dite cellule de grande taille, associée à une première station de base (101) et englobant géographiquement au moins une seconde cellule (120), dite cellule de petite taille, associée elle-même à une seconde station de base (121), un terminal (123) dudit réseau pouvant être notamment en mode communication, lorsqu'une communication est établie entre ledit terminal et un terminal distant, et en mode veille, lorsque ledit terminal n'est pas en mode communication mais présent et disponible pour une communication, dans une des cellules dudit réseau, caractérisé en ce que ladite première station de base gère le mode veille pour les terminaux présents dans ladite cellule de petite taille, ladite seconde station de base pouvant prendre en charge le mode communication et mettant en œuvre un canal commun pilote (CPICH). 1. Cellular communication network comprising at least a first cell (100), called a large cell, associated with a first base station (101) and geographically including at least a second cell (120), called a small cell, itself associated with a second base station (121), a terminal (123) of said network possibly being in particular in communication mode, when a communication is established between said terminal and a remote terminal, and in standby mode, when said terminal is not in communication mode but present and available for communication, in one of the cells of said network, characterized in that said first base station manages the standby mode for the terminals present in said small cell, said second base capable of supporting the communication mode and implementing a pilot common channel (CPICH).
2. Réseau cellulaire selon la revendication 1, caractérisé en ce que ladite première station de base gère l'ouverture d'une communication pour un terminal présent dans ladite cellule de petite taille, puis ledit réseau transfère la gestion de ladite communication à ladite seconde station de base.2. Cellular network according to claim 1, characterized in that said first base station manages the opening of a communication for a terminal present in said small cell, then said network transfers the management of said communication to said second station basic.
3. Réseau cellulaire selon la revendication 2, caractérisé en ce qu'après la clôture de ladite communication, ledit terminal passe en mode veille et est géré par la dite première station de base.3. Cellular network according to claim 2, characterized in that after the termination of said communication, said terminal goes into standby mode and is managed by said first base station.
4. Réseau cellulaire selon l'une quelconque des revendications 1 à 3, caractérisé en ce que ladite seconde station de base comprend des moyens de synchronisation sur un signal de synchronisation émis par ladite première station de base, par voie hertzienne (SCH).4. Cellular network according to any one of claims 1 to 3, characterized in that said second base station comprises means for synchronization on a synchronization signal transmitted by said first base station, by radio (SCH).
5. Réseau cellulaire selon l'une quelconque des revendications 1 à 3, caractérisé en ce que ladite seconde station de base comprend des moyens de synchronisation sur un signal de synchronisation émis par ladite première station de base, par liaison filaire. 5. Cellular network according to any one of claims 1 to 3, characterized in that said second base station comprises means for synchronization on a synchronization signal transmitted by said first base station, by wire link.
6. Réseau cellulaire selon l'une quelconque des revendications 4 et 5, caractérisé en ce que ledit terminal déduit sa synchronisation sur ladite seconde station de base de celle sur ladite première station de base.6. Cellular network according to any one of claims 4 and 5, characterized in that said terminal deduces its synchronization on said second base station from that on said first base station.
7. Réseau cellulaire selon la revendication 6, caractérisé en ce que ladite synchronisation dudit terminal sur ladite seconde station de base est une pseudo- synchronisation, tolérant des erreurs de synchronisation de l'ordre de 5 à 30 μs.7. Cellular network according to claim 6, characterized in that said synchronization of said terminal on said second base station is a pseudo-synchronization, tolerating synchronization errors of the order of 5 to 30 μs.
8. Réseau cellulaire selon l'une quelconque des revendications 6 et 7, caractérisé en ce que ledit terminal comprend :8. Cellular network according to any one of claims 6 and 7, characterized in that said terminal comprises:
- des moyens d'analyse des trajets multiples subis par un signal prédéterminé émis par ladite seconde station de base ; et - des moyens de synchronisation sur ledit signal prédéterminé émis par ladite seconde station de base tenant compte de ladite analyse des trajets multiples ; lesdits moyens d'analyse mettant en œuvre une étape de détermination d'au moins un trajet correspondant audit signal prédéterminé alimentant lesdits moyens de synchronisation, ledit trajet ou un desdits trajet correspondant audit signal prédéterminé, dit premier trajet, étant considéré comme base de synchronisation..means for analyzing the multiple paths undergone by a predetermined signal transmitted by said second base station; and means of synchronization on said predetermined signal transmitted by said second base station taking account of said analysis of the multiple paths; said analysis means implementing a step of determining at least one path corresponding to said predetermined signal supplying said synchronization means, said path or one of said paths corresponding to said predetermined signal, said first path, being considered as the basis of synchronization. .
9. Réseau cellulaire selon la revendication 8, caractérisé en ce que lesdits moyens de synchronisation tiennent compte uniquement de la détermination d'au moins un trajet correspondant audit signal prédéterminé émis par ladite seconde station de base, ladite détermination étant mise en œuvre par lesdits moyens d'analyse des trajets multiples.9. Cellular network according to claim 8, characterized in that said synchronization means take account only of the determination of at least one path corresponding to said predetermined signal transmitted by said second base station, said determination being implemented by said means multipath analysis.
10. Réseau cellulaire selon l'une quelconque des revendications 8 et 9, caractérisé en ce que ledit signal prédéterminé est un signal (CPICH) dédié au traitement des trajets multiples et émis par ladite seconde station de base.10. Cellular network according to any one of claims 8 and 9, characterized in that said predetermined signal is a signal (CPICH) dedicated to the processing of multiple paths and transmitted by said second base station.
11. Réseau cellulaire selon l'une quelconque des revendications 1 à 10, caractérisé en ce qu'au moins certaines cellules le composant fonctionnent de façon asynchrone.11. Cellular network according to any one of claims 1 to 10, characterized in that at least certain cells making it up work asynchronously.
12. Réseau cellulaire selon la revendication 11, caractérisé en ce qu'au moins certaines cellules le composant fonctionnent de façon synchrone, avec une tolérance d'erreur de synchronisation entre elles inférieure à 5 μs. 12. Cellular network according to claim 11, characterized in that at least certain cells making it up work synchronously, with a tolerance for synchronization error between them less than 5 μs.
13. Réseau cellulaire selon l'une quelconque des revendications 5 à 7, caractérisé en ce que ladite cellule de petite taille comprend des moyens d'émission d'un signal de synchronisation (SCH) permettant audit terminal de se synchroniser sur ladite seconde station de base avec une tolérance d'erreur inférieure à 5 μs. 13. Cellular network according to any one of claims 5 to 7, characterized in that said small cell comprises means for transmitting a synchronization signal (SCH) allowing said terminal to synchronize with said second base station with an error tolerance of less than 5 μs.
14. Station de base, caractérisée en ce que, dans un réseau cellulaire, ladite station de base, dite première station de base, est destinée à être associée à une cellule dite cellule de petite taille qui est elle-même destinée à être englobée géographiquement dans une cellule, dite cellule de grande taille, associée elle- même à une seconde station de base et englobant géographiquement au moins une seconde cellule, un terminal dudit réseau pouvant être notamment en mode communication, lorsqu'une communication est établie entre ledit terminal et un terminal distant, et en mode veille, lorsque ledit terminal n'est pas en mode communication mais présent et disponible pour une communication, dans une des cellules dudit réseau, et en ce que ladite seconde station de base associée à ladite cellule de grande taille gère le mode veille pour les terminaux présents dans ladite cellule de petite taille, ladite première station de base pouvant prendre en charge le mode communication et mettant en œuvre un canal commun pilote (CPICH).14. Base station, characterized in that, in a cellular network, said base station, known as first base station, is intended to be associated with a cell known as small cell which is itself intended to be geographically included in a cell, known as a large cell, itself associated with a second base station and geographically including at least a second cell, a terminal of said network possibly being in particular in communication mode, when communication is established between said terminal and a remote terminal, and in standby mode, when said terminal is not in communication mode but present and available for communication, in one of the cells of said network, and in that said second base station associated with said large cell manages the standby mode for the terminals present in said small cell, said first base station being able to support the mode communication and implementing a pilot common channel (CPICH).
15. Station de base selon la revendication 14, caractérisé en ce qu'elle est adaptée aux communications à haut débit.15. Base station according to claim 14, characterized in that it is suitable for high speed communications.
16. Terminal destiné à coopérer avec au moins une station de selon l'une quelconque des revendications 14 et 15, caractérisé en ce que ledit terminal comprend :16. Terminal intended to cooperate with at least one station according to any one of claims 14 and 15, characterized in that said terminal comprises:
- des moyens de première synchronisation ; - d'analyse des trajets multiples subis par un signal (CPICH) prédéterminé émis par ladite station de base ; et- first synchronization means; - analysis of the multiple paths undergone by a predetermined signal (CPICH) transmitted by said base station; and
- des moyens de seconde synchronisation plus fine que ladite première synchronisation, à partir de ladite analyse des trajets multiples.- means of second synchronization finer than said first synchronization, from said analysis of the multiple paths.
17. Terminal selon la revendication 16, caractérisé en ce que ladite première synchronisation tolère des erreurs de synchronisation de l'ordre de 5 à 30 μs. 17. Terminal according to claim 16, characterized in that said first synchronization tolerates synchronization errors of the order of 5 to 30 μs.
18. Terminal selon l'une quelconque des revendications 16 et 17, caractérisé en ce que ladite seconde synchronisation tolère des erreurs de synchronisation inférieures à 5 μs.18. Terminal according to any one of claims 16 and 17, characterized in that said second synchronization tolerates synchronization errors of less than 5 μs.
19. Procédé de gestion de réseau cellulaire comprenant au moins une première cellule, dite cellule de grande taille, associée à une première station de base et englobant géographiquement au moins une seconde cellule, dite cellule de petite taille, associée elle-même à une seconde station de base, un terminal dudit réseau pouvant être notamment en mode communication, lorsqu'une communication est établie entre ledit terminal et un terminal distant, et en mode veille, lorsque ledit terminal n'est pas en mode communication mais présent et disponible pour une communication, dans une des cellules dudit réseau, caractérisé en ce qu'il comprend les étapes suivantes :19. Cellular network management method comprising at least a first cell, called large cell, associated with a first base station and geographically encompassing at least a second cell, called small cell, itself associated with a second base station, a terminal of said network possibly being in particular in communication mode, when a communication is established between said terminal and a remote terminal, and in standby mode, when said terminal is not in communication mode but present and available for a communication, in one of the cells of said network, characterized in that it comprises the following steps:
- gestion d'un mode veille par ladite première station de base pour les terminaux présents dans ladite cellule de petite taille ; et - prise en charge du mode de communication et mise en œuvre d'un canal commun pilote (CPICH) par ladite seconde station de base. management of a standby mode by said first base station for the terminals present in said small cell; and - support of the communication mode and implementation of a pilot common channel (CPICH) by said second base station.
EP02803849A 2001-11-28 2002-11-28 Cellular telecommunication network using cells of different sizes, corresponding base station, terminal and method Withdrawn EP1457077A2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR0115470 2001-11-28
FR0115470A FR2832896B1 (en) 2001-11-28 2001-11-28 CELLULAR TELECOMMUNICATION NETWORK IMPLEMENTING CELLS OF DIFFERENT SIZES, BASE STATION, TERMINAL AND CORRESPONDING METHOD
PCT/FR2002/004104 WO2003047292A2 (en) 2001-11-28 2002-11-28 Cellular telecommunication network using cells of different sizes, corresponding base station, terminal and method

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KR20040058357A (en) 2004-07-03
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RU2004117791A (en) 2006-01-10
US20050130644A1 (en) 2005-06-16
CN100391292C (en) 2008-05-28
WO2003047292A2 (en) 2003-06-05
FR2832896B1 (en) 2004-07-23
KR100960829B1 (en) 2010-06-08
CN1611089A (en) 2005-04-27
JP2005510987A (en) 2005-04-21
WO2003047292A3 (en) 2003-12-11
AU2002364619A1 (en) 2003-06-10

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