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WO1999030519A1 - Procede de synchronisation entre stations de base, et systeme cellulaire - Google Patents

Procede de synchronisation entre stations de base, et systeme cellulaire Download PDF

Info

Publication number
WO1999030519A1
WO1999030519A1 PCT/FI1998/000919 FI9800919W WO9930519A1 WO 1999030519 A1 WO1999030519 A1 WO 1999030519A1 FI 9800919 W FI9800919 W FI 9800919W WO 9930519 A1 WO9930519 A1 WO 9930519A1
Authority
WO
WIPO (PCT)
Prior art keywords
terminal
base stations
base station
terminals
timing
Prior art date
Application number
PCT/FI1998/000919
Other languages
English (en)
Inventor
Harri Holma
Antti Toskala
Original Assignee
Nokia Networks Oy
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 Nokia Networks Oy filed Critical Nokia Networks Oy
Priority to AU12395/99A priority Critical patent/AU1239599A/en
Priority to JP2000524946A priority patent/JP2001526509A/ja
Priority to EP98955625A priority patent/EP1034673A1/fr
Publication of WO1999030519A1 publication Critical patent/WO1999030519A1/fr
Priority to NO20002640A priority patent/NO20002640D0/no

Links

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
    • H04B7/2684—Synchronisation of a mobile station with more than one base station
    • 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

Definitions

  • the present invention relates to a method for synchronizing base stations in a cellular radio system which comprises in each cell at least a base station and a number of terminals, and in which method the base station transmits a reference signal, and the terminals can simultaneously communicate with one or more base stations and simultaneously receive the reference signal from more than one base station, and in which method the base stations and the terminals use a TDD method for communication, and in which method the connections between the base stations and the terminals comprise common channels and dedicated channels.
  • base stations of cellular radio systems may be either synchronous or asynchronous with respect to one another, depending on the system.
  • signals of the base stations are either synchronous or asynchronous with respect to one another.
  • Systems applying a CDMA multiple access method provide an example of systems in which it is advantageous to apply macrodiversity.
  • a narrow-band data signal of a user is multiplied to a relatively wide band by a spreading code having a considerably wider band than the data signal.
  • Known test systems use bandwidths such as 1.25 MHz, 10 MHz and 25 MHz.
  • the data signal spreads over the entire band used. All users transmit by simultaneously using the same frequency band.
  • a specific spreading code is used on each connection between a base station and a mobile station, and different user signals can be distinguished from one another at receivers on the basis of the user-specific spreading code.
  • the aim is to select the spreading codes in such a way that they are orthogonal with respect to one another, i.e. do not correlate with one another.
  • Correlators in conventionally implemented CDMA receivers are synchronized with the desired signal which is recognized on the basis of the spreading code.
  • the data signal is restored to the original band by multiplying it again by the same spreading code as at the transmission stage.
  • the signals multiplied by some other spreading code do not correlate and are not restored to the narrow band. From the viewpoint of the desired signal, they thus appear as noise.
  • the aim is thus to detect the signal of the desired user from the group of several interfering signals.
  • the spreading codes correlate, and the signals of the other users make the detection of the desired signal difficult by distorting the received signal non-linearly. Such interference caused by different users to one another is called multiple-access interference.
  • the base stations usually transmit a reference signal by means of which the terminals recognize the transmission of the base station.
  • This reference signal or a pilot signal, is usually a data-unmodulated signal that is multiplied by a known spreading code.
  • Macrodiversity is easy to implement by CDMA technique. Two base stations, for example, then transmit a signal to one terminal. The terminal is able to receive and utilize the two signals. Correspondingly, in the other transmission direction, more than one base station can receive the transmission of the same terminal.
  • macrodi- versity is also referred to as soft handover.
  • the terminal communicating with a first base station is approaching the border of a cell and gradually also starts receiving signals from the base station of a neighbouring cell.
  • the terminal can simultaneously communicate with the two base stations, and when moving on deeper into the area of the latter base station, the terminal can gradually switch off the connection to the first base station. From the viewpoint of the user, handover between the base stations takes place unnoticed, and the signal quality remains good all the time.
  • TDD-CDMA Time Division Duplex
  • a TDD technique divides a transmission frame in which a signal is transmitted between a transmitter and a receiver into two parts that are used in different transmission directions.
  • the TDD technique is illustrated in Figure 1 presenting by way of example a feasible TDD frame.
  • the frame is divided into two parts 100, 102, which are separated by a short guard time 104.
  • the first part 100 of the frame is used in transmission direction from base station to terminal, for example.
  • the second part 102 of the frame is used in transmission direction from terminal to base station.
  • Between the two parts is a relatively short guard time, during which no transmissions occur.
  • the guard time is required because of a propagation delay in order that the transmissions of different transmission directions would not overlap.
  • the synchronization of the signals is essential in a situation in which the terminal simultaneously communicates with more than one base station. If the signals coming from the different base sta- tions are not synchronous with respect to one another, and different parts of the TDD frame therefore overlap, then interference occurs between different transmission d'rections.
  • base stations are synchronized with one another mainly in two different manners. Firstly, synchronization can be achieved by allocating a common clock signal to all base stations. This requires a separate cabling for all base stations, which makes the synchronization expensive and difficult to implement. Secondly, the base stations can be provided with a GPS receiver which receives a clock signal transmitted by a satellite. This adds to the costs of the base station and is difficult to implement if the base station is located indoors.
  • An object of the invention is to provide a method and a cellular radio system implementing the method so as to solve the above-mentioned problems. This is achieved by the method of the type presented in the introduction, which is characterized in that the terminal measures the timing difference of the reference signals it has received from the different base stations and reports it to one or more base stations, and that, on the basis of the measured timing difference, the one or more base stations adjust the timing of the common and the dedicated channels they have transmitted to the terminals.
  • the invention also relates to a method for synchronizing base stations in a cellular radio system which comprises in each cell at least a base station and a number of terminals, and which base station transmits a reference signal, and which terminals can simultaneously communicate with one or more base stations and simultaneously receive the reference signal from more than one base station, and the base stations and in which method the termi- nals use a TDD method for communication.
  • the method of the invention is characterized in that when the terminal receives a reference signal from the base station not communicating with it, the terminal measures the timing difference of the detected reference signal in relation to one or more reference signals from the base stations communicating with the terminal, and that it reports the measured difference to one or more base stations communicating with the terminal, and that, on the basis of the measured timing difference, the one or more base stations adjust the timing of the signals they have transmitted to the terminals with respect to each other.
  • the invention also relates to a cellular radio system comprising in each cell at least a base station and a number of terminals, and which base station is arranged to transmit a reference signal, and which terminals are arranged to simultaneously communicate with one or more base stations by using a TDD method and to simultaneously receive the reference signal form more than one base station.
  • the system of the invention is characterized in that the terminal comprises means for measuring a timing difference between a reference signal transmitted by the base station not communicating with the terminal and one or more reference signals transmitted by the base stations communicating with the terminal, and means for reporting the measured dif- ference to the one or more base stations communicating with the terminal, and that on the basis of the measured timing difference, the one or more base stations are arranged to adjust the timing of the signals they have transmitted to the terminal in relation to each other.
  • the method and system of the invention provide many advantages. With the help of the invention the base stations can be advantageously synchronized without additional equipments and arrangements required in connection with soft handovers. Synchronizations can always be performed in the event of handovers, and if no handovers occur for some time, and there is a risk of the base stations losing the common synchronization, then one of the terminals can be commanded to measure the timing difference between the pilot signals of the base stations.
  • Figure 2 illustrates an example of a cellular radio system to which the invention can be applied
  • Figure 3 shows the structure of a terminal of the system of the invention.
  • the invention can be applied to any cellular radio system in which base stations transmit a pilot signal or a reference signal corresponding thereto.
  • a cellular radio system using a TDD-CDMA method is used as an example, but the essential features of the invention are independent of the multiple access method used.
  • Figure 2 illustrates an example of a cellular radio system to which the invention can be applied.
  • the figure shows two adjacent cells 200, 202 of the radio system, each cell being served by a cell-specific base station 204, 206.
  • the base stations communicate with a base station controller 208 which communicates with the rest of the telephone network via a mobile services switching centre 210.
  • Figure 2 also shows two subscriber terminals 214, 216.
  • the first terminal 214 communicates with the first base station 204, and the second terminal communicates with the second base station 206.
  • the connections in this example are implemented by TDD technique in which both transmission directions are on the same frequency band and by a CDMA multiple access method in which each connection has a specific spreading code for use.
  • the two cells 200, 202 use the same frequency band.
  • the transmissions of the base stations are not synchronous, then the transmissions of different transmission directions at different base stations possibly overlap in time. In that case, when the first terminal 214, for example, attempts to receive transmission from the first base station 204, then the second terminal 216 may simultaneously transmit a signal to the second base station 206, and the reception of the first terminal 214 in that case fails.
  • the connections between the base stations and the terminals com- prise dedicated channels and common channels.
  • the dedicated channels are connection-specific channels, such as a speech channel or a control channel associated with it, for example.
  • the common channels transmitted by the base station can be received by several terminals.
  • the base stations transmit a refer- ence signal, or a pilot signal, which is in the CDMA system a data- unmodulated signal.
  • the first and the second base station 204, 206 each transmits a pilot signal, and the terminals are able to separate these signals from each other.
  • the pilot signal can be received over the entire coverage area of the base station.
  • the terminals detect the pilot signal of the base station of a neighbouring cell particularly at the periphery of the cells.
  • the terminals start measuring the intensity of the pilot signal for the purpose of a possibly forthcoming handover. Let us assume that the first terminal 214 has detected a pilot signal transmitted by the second base station 206.
  • the terminal measures the timing difference of the pilot sig- nals it has received from the first base station 204 and the second base station 206 and reports the measured result to the first base station 204 communicating with the terminal.
  • the first base station 204 reports the timing difference measured by the terminal 214 to the second base station 206 via the base station controller 208, for example.
  • the sec- ond base station 206 is able to adjust its timing to be congruent with the first base station 204.
  • the base station 204 is able to adjust its timing to be congruent with the base station 206.
  • Base station areas generally comprise several terminals that move and simultaneously receive pilot signals of more than one base station and prepare or perform handover between the base stations. Adjusting synchronization requires only small modifications to the conventional soft handover, and the synchronization operation of the invention thus does not interfere with the normal operation of the terminal. Synchronization adjustment operation can be a continuous process ensuring that the clocks of the base stations do not lose the common synchronization. If no terminals performing handover exist at a given time, the base stations can command one of the terminals to perform the timing measurement.
  • the base stations should be synchronized with an accuracy which prevents the signals from different transmission directions from overlapping more than a fraction of the length of a frame. If it is assumed that the length of the frame is 10 ms, for example, a sufficient synchronization accuracy is within the range of 100-200 ⁇ s. Propagation delays of radio signals can be ignored in the present description, since the distance of 5 km, for example, only corresponds to a propagation delay of 17 ⁇ s.
  • the base station controller is able to arrange the base stations within its area into some kind of hierarchy according to which the base stations synchronize with one another. This helps the base stations to know which base station has to change its synchronization at a given time.
  • the terminal comprises an antenna 300 by means of which the received signal is applied via a filter 302 to radio frequency parts 304 converting the signal into an intermediate frequency. From the radio frequency parts 304 the signal is applied to a multiplier 306 multiplying the signal by the desired spreading code 308. From the multiplier the signal is further applied to decoding means 301 and further to other parts 322 of the receiver.
  • the signal 324 to be transmitted in transmitting direction is applied to an encoder 312 performing channel encoding or a corresponding encoding, and further to a multiplier 314 multiplying the signal by a connection-specific spreading code 316.
  • the multiplied signal is applied via radio frequency parts 318 and a filter 302 to the, antenna 300.
  • the terminal further comprises control means 320 controlling the operation of the other parts of the apparatus.
  • the control means are preferably implemented by a processor and software suitable for the purpose.
  • Figure 3 only shows the essential parts of the terminal.
  • the apparatus may also comprise other components, including filters, amplifiers, encoding means and decoding means, as it is obvious to those skilled in the art.
  • the details of the structure of the apparatus may deviate from the above description, depending on the multiple access method used, for example.
  • the signal to be transmitted is not multiplied by a spreading code.
  • the terminal can receive a pilot signal from more than one base station. In that case, the received signal is multiplied by a spreading code used by the desired base station. The pilot signal is then detected from the total signal received.
  • the terminal comprises the means
  • the terminal comprises the means 320, 312 to 318 for reporting the measured difference to one or more base stations communicating with the terminal.
  • the base stations of the system are arranged to adjust their timing on the basis of the timing difference measurement.
  • the operations of the invention can preferably be implemented by software in the base stations of the system.

Landscapes

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

Abstract

L'invention concerne un procédé de synchronisation entre stations de base, et un système radiocellulaire comprenant dans chaque cellule au moins une station de base (204, 206) et plusieurs terminaux (214, 216). Les stations de base émettent un signal de référence, et les terminaux peuvent communiquer simultanément avec une ou plusieurs stations de base et recevoir simultanément le signal de référence émis par plus d'une station de base. Afin d'assurer une synchronisation facile entre les stations de base, le terminal mesure la différence de synchronisation entre un signal de référence émis par une station de base ne communiquant pas avec le terminal et un ou plusieurs signaux de référence émis par des stations de base communiquant avec le terminal. Le terminal signale la différence mesurée à la ou aux station(s) de base communiquant avec le terminal. En fonction de la différence de synchronisation, la ou les stations de base ajuste(nt) la synchronisation des signaux qu'elle(s) a (ont) envoyés au terminal, les uns par rapport aux autres.
PCT/FI1998/000919 1997-11-24 1998-11-23 Procede de synchronisation entre stations de base, et systeme cellulaire WO1999030519A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
AU12395/99A AU1239599A (en) 1997-11-24 1998-11-23 Base station synchronization method and cellular system
JP2000524946A JP2001526509A (ja) 1997-11-24 1998-11-23 ベースステーション同期方法及びセルラーシステム
EP98955625A EP1034673A1 (fr) 1997-11-24 1998-11-23 Procede de synchronisation entre stations de base, et systeme cellulaire
NO20002640A NO20002640D0 (no) 1997-11-24 2000-05-23 FremgangsmÕte for synkronisering av basestasjoner, samt celledelt system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI974310A FI974310A7 (fi) 1997-11-24 1997-11-24 Menetelmä tukiasemien synkronisoimiseksi ja solukkoradiojärjestelmä
FI974310 1997-11-24

Publications (1)

Publication Number Publication Date
WO1999030519A1 true WO1999030519A1 (fr) 1999-06-17

Family

ID=8550000

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1998/000919 WO1999030519A1 (fr) 1997-11-24 1998-11-23 Procede de synchronisation entre stations de base, et systeme cellulaire

Country Status (7)

Country Link
EP (1) EP1034673A1 (fr)
JP (1) JP2001526509A (fr)
CN (1) CN1279867A (fr)
AU (1) AU1239599A (fr)
FI (1) FI974310A7 (fr)
NO (1) NO20002640D0 (fr)
WO (1) WO1999030519A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003506933A (ja) * 1999-07-30 2003-02-18 アリ・ホッティネン 周波数分割二重および時間分割二重通信システム間のソフトハンドオフを実行するためのシステムおよび方法
EP1566901A1 (fr) * 2004-02-18 2005-08-24 Siemens Aktiengesellschaft Procédé de synchronisation pour un système de radiocommunications
US6961398B2 (en) * 2000-04-07 2005-11-01 Interdigital Technology Corp. Base station synchronization for wireless communication systems
US7046754B2 (en) 2001-02-27 2006-05-16 Interdigital Technology Corporation Method for establishing a communication link
WO2010051845A1 (fr) 2008-11-06 2010-05-14 Nokia Siemens Networks Oy Appareil et procédé de synchronisation décentralisée
US7773562B2 (en) 2003-05-13 2010-08-10 Interdigital Technology Corporation Soft and softer handover in time division duplex code division multiple access (TDD-CDMA) networks
US7813311B2 (en) 2002-02-05 2010-10-12 Interdigital Technology Corporation Method and apparatus for synchronizing base stations
WO2010124930A1 (fr) * 2009-04-30 2010-11-04 Nokia Siemens Networks Oy Procédé et appareil servant à fournir une quantification de signaux de synchronisation
US9736803B2 (en) 2012-03-16 2017-08-15 Huawei Technologies Co., Ltd. Cell configuration method, synchronization method, user equipment, and base station

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AU4985701A (en) * 2000-04-06 2001-10-23 Interdigital Tech Corp Synchronization of timing advance and deviation
CN100428653C (zh) * 2004-11-16 2008-10-22 戴闽鲁 基站间时间同步关系及tdd共信道干扰基站的判定方法
US8514837B2 (en) * 2006-06-14 2013-08-20 Koninklijke Philips N.V. Method of communicating data in communication systems
CN101237272B (zh) * 2007-02-02 2012-12-19 中兴通讯股份有限公司 射频通道同步系统及方法
CN101369824B (zh) * 2008-10-21 2012-03-28 北京北方烽火科技有限公司 一种基站失步检测装置及方法

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WO1994030024A1 (fr) * 1993-06-14 1994-12-22 Telefonaktiebolaget Lm Ericsson Alignement temporel de transmission dans une liaison descendante d'un systeme amdc
EP0845877A2 (fr) * 1996-11-28 1998-06-03 Oki Electric Industry Co., Ltd. Système de communication mobile pour effectuer un transfert d'appel avec différence de phase et signaux de synchronisation de trame corrigés

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
JPH06334593A (ja) * 1993-05-21 1994-12-02 N T T Idou Tsuushinmou Kk 移動通信システム基地局同期法
WO1994030024A1 (fr) * 1993-06-14 1994-12-22 Telefonaktiebolaget Lm Ericsson Alignement temporel de transmission dans une liaison descendante d'un systeme amdc
EP0845877A2 (fr) * 1996-11-28 1998-06-03 Oki Electric Industry Co., Ltd. Système de communication mobile pour effectuer un transfert d'appel avec différence de phase et signaux de synchronisation de trame corrigés

Cited By (24)

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Publication number Priority date Publication date Assignee Title
JP2011019241A (ja) * 1999-07-30 2011-01-27 Qualcomm Inc 周波数分割二重および時間分割二重通信システム間のソフトハンドオフを実行するためのシステムおよび方法
JP2003506933A (ja) * 1999-07-30 2003-02-18 アリ・ホッティネン 周波数分割二重および時間分割二重通信システム間のソフトハンドオフを実行するためのシステムおよび方法
US9247513B2 (en) 2000-04-07 2016-01-26 Interdigital Technology Corporation Base station synchronization
US6961398B2 (en) * 2000-04-07 2005-11-01 Interdigital Technology Corp. Base station synchronization for wireless communication systems
US6980615B2 (en) 2000-04-07 2005-12-27 Interdigital Technology Corp. Base station synchronization
US8416904B2 (en) 2000-04-07 2013-04-09 Interdigital Technology Corporation Base station synchronization
US7379518B2 (en) 2000-04-07 2008-05-27 Interdigital Technology Corporation Base station synchronization
US7924961B2 (en) 2000-04-07 2011-04-12 Interdigital Technology Corporation Base station synchronization
US7433437B2 (en) 2001-02-27 2008-10-07 Interdigital Technology Corporation Method for establishing a communication link
US8503512B2 (en) 2001-02-27 2013-08-06 Intel Corporation Method of generating an index value
US9247509B2 (en) 2001-02-27 2016-01-26 Intel Corporation Method of generating an index value
US7046754B2 (en) 2001-02-27 2006-05-16 Interdigital Technology Corporation Method for establishing a communication link
US7746920B2 (en) 2001-02-27 2010-06-29 Interdigital Technology Corporation Method of generating an index value
US7813311B2 (en) 2002-02-05 2010-10-12 Interdigital Technology Corporation Method and apparatus for synchronizing base stations
US7773562B2 (en) 2003-05-13 2010-08-10 Interdigital Technology Corporation Soft and softer handover in time division duplex code division multiple access (TDD-CDMA) networks
EP1566901A1 (fr) * 2004-02-18 2005-08-24 Siemens Aktiengesellschaft Procédé de synchronisation pour un système de radiocommunications
WO2010051845A1 (fr) 2008-11-06 2010-05-14 Nokia Siemens Networks Oy Appareil et procédé de synchronisation décentralisée
WO2010124930A1 (fr) * 2009-04-30 2010-11-04 Nokia Siemens Networks Oy Procédé et appareil servant à fournir une quantification de signaux de synchronisation
US9736803B2 (en) 2012-03-16 2017-08-15 Huawei Technologies Co., Ltd. Cell configuration method, synchronization method, user equipment, and base station
US10244498B2 (en) 2012-03-16 2019-03-26 Huawei Technologies Co., Ltd. Cell configuration method, synchronization method, user equipment, and base station
US10492158B2 (en) 2012-03-16 2019-11-26 Huawei Technologies Co., Ltd. Cell configuration method, synchronization method, user equipment, and base station
US10609666B2 (en) 2012-03-16 2020-03-31 Huawei Technologies Co., Ltd. Cell configuration method, synchronization method, user equipment, and base station
US11375466B2 (en) 2012-03-16 2022-06-28 Huawei Technologies Co., Ltd. Cell configuration method, synchronization method, user equipment, and base station
US11825432B2 (en) 2012-03-16 2023-11-21 Huawei Technologies Co., Ltd. Cell configuration method, synchronization method, user equipment, and base station

Also Published As

Publication number Publication date
FI974310L (fi) 1999-05-25
JP2001526509A (ja) 2001-12-18
FI974310A0 (fi) 1997-11-24
NO20002640L (no) 2000-05-23
NO20002640D0 (no) 2000-05-23
FI974310A7 (fi) 1999-05-25
EP1034673A1 (fr) 2000-09-13
CN1279867A (zh) 2001-01-10
AU1239599A (en) 1999-06-28

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