Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
  • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
  • H04B7/2662—Arrangements for Wireless System Synchronisation
  • H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
  • H04B7/2678—Time synchronisation
  • H04B7/2681—Synchronisation of a mobile station with one base station
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/06—Synchronising arrangements
  • H04J3/0635—Clock or time synchronisation in a network
  • H04J3/0682—Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W56/00—Synchronisation arrangements
  • H04W56/0055—Synchronisation arrangements determining timing error of reception due to propagation delay
  • H04W56/0065—Synchronisation arrangements determining timing error of reception due to propagation delay using measurement of signal travel time
  • H04W56/009—Closed loop measurements

Definitions

• the invention relates to the field of communications networks in which it is not possible to know precisely the propagation time of a signal, and more particularly the management of communications within such networks.
• Certain communications networks and in particular those called “random access”, require fine synchronization of the transmissions of the communication terminals which are attached to their communications management equipment, such as base stations.
• the networks broadcast, generally periodically, via their communications management equipment, reference signals
• pilot beacon which represent the clock that the terminals, which are attached to them, must use as internal time reference to synchronize their emissions with respect to a predetermined configurable model and generally broadcast periodically.
• pilot beacon When a terminal receives a pilot beacon it sets its internal clock on the clock defined by this pilot beacon.
• the time taken by a pilot beacon to reach a terminal varies either according to the position of said terminal relative to the coverage area of the base station to which it is attached (in the case of a radio network), or characteristics of the transmission medium providing the link between said terminal and its attached communications management equipment (in the case of a heterogeneous wired network).
• each terminal attached to communications management equipment, transmitting at times defined by the model associated with said audit equipment and referenced with respect to the time of reception of the pilot beacon, said equipment therefore receives the signals transmitted by the terminals attached to it almost anytime and not at specific times, so that the synchronization of the terminals n is not effective. More precisely, due to the time offsets between the internal time references of the various terminals, the time windows for reception of the communications management equipment, set on its own internal time reference and of width equal to that of the access slots, are no longer suitable. In an attempt to remedy this drawback, certain solutions have been proposed.
• TDMA type cellular networks such as GSM networks
• a time compensation or "timing advance” to be applied to the instants of emission of its following accesses.
• Each time compensation is determined at a base station. It corresponds to the round trip propagation time between the base station and the terminal concerned, in the internal time reference frame of the base station.
• the time compensation is transmitted to the terminal concerned via a signaling channel, so that it immediately applies it to its transmission chain.
• the main drawback of this solution lies in the fact that it monopolizes the resources of each base station for the calculation and transmission of the time compensations to the terminals which are attached to it and which are in the course of communication. In addition, this solution is not applicable to the first network access of a terminal.
• TDMA-type cellular networks such as GMR networks (for example Thuraya)
• GMR networks for example Thuraya
• access slots the network access slots
• the main drawback of this solution lies in the fact that the increase in on-call times comes at the expense of the number of access slots available (only 4 remain available out of the initial 8).
• time reference does not necessarily come directly from the satellites of the GNSS network; it can indeed come from terrestrial relays.
• This method is characterized by the fact that it consists in: transmitting to the terminals, by means of the equipment and in at least one signaling channel (common or dedicated), a reference signal and an associated message comprising information representative of the time of transmission of the reference signal with respect to the GNSS network time frame, then, when a terminal receives a reference signal and the associated message, to date the time of reception of this message so that the terminal can determine a time difference between the time of emission and the time of reception of the message and deduce therefrom the propagation time of the associated reference signal.
• a signaling channel common or dedicated
• the reference signal defines a reference (such as for example a pilot beacon) for the time synchronization of the terminals with respect to a model (or card) defining access slots authorized to the network
• a reference such as for example a pilot beacon
• the transmission of the reference signal and the associated message can be carried out in the same signaling channel (for example in the common channel BCH in the case of a CDMA type network) or in separate signaling channels.
• the invention also provides communications management equipment for a communications network (possibly with random access), comprising management means responsible for generating reference signals intended to be transmitted, in a signaling channel (common or dedicated) , to communication terminals attached to it, and having, like each of the terminals, an internal time reference defined with respect to the time reference of a satellite positioning network (or GNSS network) and provided by a receiver
• GNSS that it contains or to which it is coupled.
• This equipment is characterized by the fact that its management means are also responsible for generating messages each comprising information representative of the time of emission of each reference signal transmitted with respect to the time frame of reference of the GNSS network so that they are transmitted to the terminals in a signaling channel.
• the communications management equipment can generate each reference signal and the associated message so that they are transmitted in the same signaling channel or in separate signaling channels.
• the invention also provides a communication terminal for a communications network (possibly with random access) comprising at least one communications management equipment of the type presented above.
• This communication terminal is characterized by the fact that it comprises: - reception means capable of defining, from signals originating from a satellite positioning network (or GNSS network), an internal time reference with respect to the reference system time of this GNSS network, and loaded processing means, when they receive a reference signal and an associated message, comprising information representative of the time transmission of the reference signal with respect to the GNSS network time frame, transmitted by the communications management equipment to which their terminal is attached, in at least one signaling channel (common or dedicated), from the time of reception of the message, then determine the time difference between the time of emission and the time of reception of the message in order to deduce from this time difference the propagation time of the reference signal associated with the message.
• - reception means capable of defining, from signals originating from a satellite positioning network (or GNSS network), an internal time reference with respect to the reference system time of this GNSS network
• the processing means of a terminal can be responsible for deducing from the propagation time that they have determined a time offset representative of the round trip propagation time between the equipment and the terminal concerned, then applying this offset to the model, in this case, the communication terminal comprises a transmission chain responsible for synchronize on the offset model in order to transmit, in one of the authorized access slots, a request for access to the network to the communications management equipment on which said terminal depends.
• the invention is particularly well suited, although not exclusively, to random access communications networks chosen from the FDMA, TDMA and CDMA networks, and more particularly those of W-CDMA, CDMA 2000 type via satellite (or IS-95 ) or terrestrial, TTA, CCSA, (S-) UMTS, GMR, GSM and (S-) GSM / GPRS, as well as those used for optical communications by optical fibers.
• it generally relates to all communications networks in which it is not possible to know precisely the propagation time of a signal, and in particular certain wired communications networks, such as for example those using electrical lines. , and Internet Protocol (IP) networks.
• IP Internet Protocol
• communications communications including a gateway type satellite communications management equipment and communication terminals, all coupled to a satellite positioning network.
• the appended drawing may not only serve to complete the invention, but also contribute to its definition, if necessary.
• the object of the invention is to enable the propagation time of signals to be determined by communication terminals attached to a communications network, possibly with random access.
• Communication terminal is understood here to mean any network equipment capable of exchanging data in the form of signals, either with other equipment, via their home network (s), or with its own home network . It could therefore be, for example, user equipment, such as fixed or portable computers, fixed or portable telephones, or personal digital assistants (or PDAs), or servers. It is considered in what follows, by way of illustrative example, that the communications network is a random access network, such as a CDMA 3G type satellite network, such as for example an S-UMTS network, operating according to the mode. called frequency duplexing (or FDD for “Frequency Division Dupleix”) or the so-called time duplexing mode (or TDD for “Time Division Dupleix”).
• FDD Frequency Division Dupleix
• TDD Time Division Dupleix
• the invention is not limited to this single type of network. It relates in fact to all the communication networks to which communication terminals can access by means of a random access procedure, based for example on the transmission of a preamble (or access request) during access time slots. (or “access slots”), and in which there is a significant dispersion (or divergence) of the times of propagation of the signals between a communications management equipment and the communication terminals attached to it.
• the invention relates in particular to random access communications networks which include radio relays or repeaters, possibly of the satellite type, such as for example the FDMA, W-CDMA, CDMA 2000 satellite networks (or IS-95) or terrestrial, TTA, CCSA, GMR, GSM and S-GSM / GPRS.
• the invention also relates to wired networks using heterogeneous transmission media and / or ensuring both local and distant links (for example transatlantic), such as for example certain optical fiber optic networks, with or without relays, and some networks using power lines as a communication medium. It also relates to Internet Protocol (IP) networks.
• IP Internet Protocol
• the communication terminals are user equipment (UE) of the mobile telephone type, attached to the S-UMTS network.
• UE user equipment
• S-UMTS UMTS network with satellite access
• CN Core Network
• the satellite access network first of all comprises at least one communications management equipment item, represented here in the form of a satellite base station SG (or “Gateway”), connected to the Core Network CN by an RNC node ( or "Radio Network Controller"), and at least one SAT telecommunications satellite allowing the exchange of data by wave between the SG gateway and UE user equipment (here mobile phones) equipped with a transmitter / satellite receiver.
• a communications management equipment item represented here in the form of a satellite base station SG (or “Gateway”), connected to the Core Network CN by an RNC node ( or "Radio Network Controller"), and at least one SAT telecommunications satellite allowing the exchange of data by wave between the SG gateway and UE user equipment (here mobile phones) equipped with a transmitter / satellite receiver.
• the satellite link constitutes a satellite interface.
• the RNC provides both service and control. Its English name is then "controlling and serving RNC".
• the SG gateway integrates a Node B (or base station) of the S-UMTS network responsible for signal processing, and in particular for managing requests for access to said S-UMTS network.
• Node B is also associated with one or more cells, each covering a radio zone in which one or more pieces of UE user equipment may be located.
• the cell or cells of a Node B are included in the coverage area ZC of the satellite SAT which is associated with the gateway SG which integrates it (here, a cell corresponds to a satellite spot). -s
• the SG gateway includes a satellite positioning receiver RG1, responsible for analyzing the signals supplied by a satellite positioning network (shown in the figure by its constellation CS of satellites SN).
• the satellite positioning network is a GNSS network (for “Global Navigation Satellite System”), such as for example the GPS network, or the GLONASS network, or even the future GALILEO network.
• GNSS network for “Global Navigation Satellite System”
• the signals providing the time reference do not necessarily come directly from the satellites of the GNSS network; they can indeed come from terrestrial relays.
• the GNSS receiver RG1 is in particular responsible for determining, from the signals received from the GNSS network, the current time within the GNSS network, called GNSS time (or system time), so that Node B sets its internal clock on this GNSS time.
• Node B has an internal time reference defined in relation to the time reference of the GNSS network.
• This internal time reference allows a MG management module of Node B to generate reference signals, defining here what a person skilled in the art calls a "pilot beacon" and intended to be transmitted by the gateway SG, via the satellite SAT, to the user equipment UE which are located in the area ZC coverage of said SAT satellite.
• the transmission of the reference signals is done, in the example described, in broadcasting mode in a common signaling channel. It is important to note that in the example network described just as in other types of networks, this transmission can be done in dedicated signaling channels.
• Node B is also responsible for generating messages comprising a model (or card) defining (time slots) access (or “access slots”) during which the user equipment UE attached to it are authorized to transmit network access requests (or preambles).
• models are generally configurable and broadcast periodically to user equipment UE by the gateway SG on which they depend, via the SAT satellite and in a common signaling channel. For example, in an access network of the “slotted ALOHA” type, the width of an access slice is equal to 5120 chips (which corresponds to 1.3 ms).
• the access slot model is used by UE user equipment, which is attached to a Node B, to determine the times (slots) at which they are authorized to transmit signals to the SG gateway which includes said Node B, in particular during each first access to the network.
• RACH dedicated random access channel
• the satellite SAT then transmits the signed preamble to the gateway SG which communicates it to its Node B so that it initiates a preamble acknowledgment procedure.
• the message which is associated with a transmitted preamble, can only be transmitted by the UE user equipment provided that said preamble has actually been acknowledged by the Node B.
• the transmission of a preamble can only be done during the 'one of the authorized access slots, defined by the model received.
• this model is used for all the UE user equipment located in the same cell (or ZC coverage area), the emission chains CE of these user equipments must be synchronized or calibrated with respect to the same time reference. , that is to say that of Node B on which they depend.
• reference signals pilot beacons
• the invention firstly proposes to equip each user equipment UE with a GNSS receiver RG2, responsible, like the GNSS receiver RG1 of the gateway SG, for analyzing the signals transmitted by the GNSS CS network to determine the GNSS time (or system time), so that its CE transmission chain can be temporally aligned with it.
• the user equipment UE has an internal time reference defined with respect to the time reference of the GNSS network.
• the invention also proposes to adapt the MG management module that includes each Node B of the S-UMTS network so that each time it generates a reference signal (or pilot beacon) it also generates an associated message comprising information representative of the time of transmission of this reference signal with respect to the time reference of the GNSS network on which its internal time reference is calibrated (thanks to the GNSS receiver RG1).
• Each reference signal (or pilot beacon) and the associated message are then communicated by the Node B to the gateway SG so that it transmits them to the user equipment UE in at least one common signaling channel.
• the S-UMTS standard requires that UE user equipment listen to the different Pilot, SCH and BCH signaling channels before initiating a network access request, it is therefore not necessary to modify the radio interface and standard network access procedures implemented by user equipment.
• this PM processing module is responsible for listening to the signaling channel (for example BCH), in v * which the messages associated with the reference signals are transmitted, in order to detect each message and date its time of reception with respect to GNSS time, supplied by the GNSS GR2 receiver and used to calibrate the CE transmission chain.
• the PM processing module Once the PM processing module is in possession of the time of emission contained in a message and the time of reception of said message, it determines the time difference between these two hours, then it deduces from this time difference (by a simple subtraction) the time (called “propagation”) taken by the reference signal, associated with the message, to reach its user equipment UE.
• the PM processing module is also responsible for deducing the time offset which must be applied to the model (here access slots) in order to take account of the round trip propagation time of the reference signal. To do this, it multiplies by 2 the value of the propagation time that it has just deducted, since it only corresponds to the single outward journey (from the gateway SG to the user equipment UE). Then, the PM processing module applies the time offset to the access slot model.
• the transmission chain CE then only has to synchronize (or lock itself) on the model shifted by the PM processing module in order to transmit to the Node B on which it depends a request for access to the network, in the 'one of the authorized access slots of said model, according to the procedure described above.
• the processing module PM of a communication user equipment UE according to the invention, and the management module MG of a communication management equipment SG according to the invention, can be produced in the form of electronic circuits, software (or computer) modules, or a combination of circuits and software.
• the invention also provides a method for calculating the propagation time of a reference signal between a communications management equipment SG of a communications network (possibly with random access) and user equipment UE attached to this equipment.
• management system, SG management equipment and user equipment UE each having an internal time reference defined with respect to the time reference of a GNSS CS network and supplied by a GNSS receiver. This can in particular be implemented using the communications management equipment SG and the communication terminals UE presented above.
• This method consists in: transmitting to the terminals UE, by means of the equipment SG and in at least one signaling channel (common or dedicated), a reference signal and an associated message comprising information representative of the time transmission of the reference signal with respect to the time reference of the GNSS CS network, then, when a terminal UE receives a reference signal and the associated message, to date the time of reception of this message so that this terminal UE can determine a time difference between the time of emission and the time of reception of the message and deduce therefrom the propagation time of the associated reference signal.
• a signaling channel common or dedicated
• the calculations performed by the terminals are simpler than those of the prior art based on the use of ephemeris, which now no longer need to be broadcast, thus making it possible to free up resources. Furthermore, since the ephemeris is no longer broadcast, the terminals no longer need to listen to the information broadcasting service before initiating a request for access to the network.
• the transmissions of the terminals being synchronized with each other, this allows in the case of networks of the TDMA type to reduce the guard time between access slots, and in the case of networks of the CDMA type to significantly reduce interference and therefore increase the transmission capacity while allowing a reduction in the necessary transmission power, because the CDMA codes are synchronized and therefore orthogonal to each other.
• the invention is not limited to the embodiments of a communication terminal, of communications management equipment and of a propagation time calculation method described above, only by way of example, but it encompasses all the variants that those skilled in the art can envisage within the framework of the claims below.
• a communications management equipment arranged in the form of a satellite base station (or gateway), but the communications management equipment can also be arranged in the form of a station. basic, such as a Node B or a BTS coupled to a GNSS receiver.
• the invention is not limited to this single type of random access network.
• FDMA random access communication networks
• CDMA Code Division Multiple Access
• TDMA time division multiple access
• the networks of communications comprising radio relays or repeaters, possibly of satellite type, linked to a base station, as well as optical fiber optic networks with or without relays.
• the invention is also not limited to only random access networks. It indeed concerns, as indicated previously, all the communications networks, wired or not, in which it is not possible to know precisely the propagation time of a signal. Consequently, the invention is not limited to the timing of the transmission, whether it is a timing in order to access the network for the first time, as described above, or a setting in order to allow subsequent accesses to the network, in particular in the case of CDMA 2000 and IS95 networks. It can also concern the precise adaptation of timers (or “timers”) via messages with a sending date, used in particular in IP communications and in certain mobile or cellular phones. It can also concern servers, repeaters and routers in which data is temporarily blocked, for example for analysis or in the event of traffic overload. Thus, the invention can make it possible to reduce interference, in particular in the case of the use of dedicated signaling channels, and / or to optimize the receivers on the infrastructure side.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Time-Division Multiplex Systems (AREA)
• Radio Relay Systems (AREA)

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• 2004
  • 2004-05-17 FR FR0450953A patent/FR2870414B1/fr not_active Expired - Fee Related
• 2005
  • 2005-04-29 US US11/569,237 patent/US20080247352A1/en not_active Abandoned
  • 2005-04-29 EP EP05746893A patent/EP1751891A1/de not_active Withdrawn
  • 2005-04-29 WO PCT/FR2005/050290 patent/WO2005114873A1/fr active Application Filing
  • 2005-04-29 CN CNA2005800196641A patent/CN101015140A/zh active Pending

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