WO2000054435A1 - Method and system for synchronizing a base station of a radio communications system - Google Patents

Method and system for synchronizing a base station of a radio communications system Download PDF

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Publication number
WO2000054435A1
WO2000054435A1 PCT/DE2000/000763 DE0000763W WO0054435A1 WO 2000054435 A1 WO2000054435 A1 WO 2000054435A1 DE 0000763 W DE0000763 W DE 0000763W WO 0054435 A1 WO0054435 A1 WO 0054435A1
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Prior art keywords
phase
base station
base stations
bsl
signals
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PCT/DE2000/000763
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German (de)
French (fr)
Inventor
Toplica Pacic
Markus Dillinger
Gerald Ostermayer
Jürgen Schindler
Peter Slanina
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Siemens Aktiengesellschaft
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Publication of WO2000054435A1 publication Critical patent/WO2000054435A1/en

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    • 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
    • H04B7/2687—Inter base stations synchronisation
    • H04B7/2696—Over the air autonomous synchronisation, e.g. by monitoring network activity

Definitions

  • the invention relates to a method and an arrangement for - synchronization of a base station of a radio communication system, in particular a mobile radio system.
  • radio communication systems information such as voice, image information or other data is transmitted with the aid of electromagnetic waves via a radio interface between a transmitting and a receiving radio station, such as a base station or radio station.
  • the electromagnetic waves are emitted at carrier frequencies that lie in the frequency band provided for the respective system.
  • GSM Global System for Mobile Communication
  • the carrier frequencies are in the range of 900 MHz, 1800 MHz and 1900 MHz.
  • UMTS Universal Mobile Telecommunication System
  • 3rd generation systems frequencies in the frequency band of approximately 2000 MHz are provided.
  • a synchronism of the signal transmission on the radio interface is to be achieved by networking several base stations.
  • This synchronicity is particularly important for radio communication systems with a subscriber separation according to a TDMA method (Time Division Multiple Access) and an information tion transmission according to a TDD method (Time Division Duplex) in order to obtain a homogeneous time slot structure.
  • TDMA method Time Division Multiple Access
  • TDD method Time Division Duplex
  • synchronism of the base stations is also sought in known radio communication systems which use a CDMA subscriber separation method in conjunction with an FDD method.
  • hierarchical master / slave structures are generally used for the synchronization, in which, starting from a so-called master base station, the surrounding slave base stations are supplied with a central clock signal.
  • a disadvantage of this concept is an increased technical and organizational effort for the network infrastructure.
  • Another known measure for the synchronization of base stations is the use of a GPS signal (Global Positioning System) to which all base stations synchronize.
  • GPS signal Global Positioning System
  • all base stations are equipped with a GPS receiver, which disadvantageously leads to a significant increase in costs, since so-called micro base stations must also be equipped with such a receiver.
  • an antenna device for ensuring the reception of the GPS signals would have to be led out of the building, which in turn means a high technical outlay.
  • the invention has for its object to provide a method and an arrangement that allow simplified synchronization of a number of base stations of a radio communication system. This object is achieved by the method according to the features of claim 1 and by the base station according to the features of claim 6. Further developments are disclosed in the dependent claims.
  • a respective phase position of at least two signals transmitted by neighboring base stations via a radio interface is determined in a first base station.
  • the phase positions are then compared with the phase position of the signals of the first base station and a controlled variable is derived from the comparison. This controlled variable controls the phase position of the first base station in relation to the phase positions of the neighboring base stations.
  • This method advantageously ensures that each base station synchronizes with the neighboring base stations, as a result of which a hierarchical structure for synchronization in accordance with the described prior art can be dispensed with. There is therefore no clock-providing instance in the network of the base stations. Furthermore, each newly installed base station can synchronize with the surrounding base stations.
  • a respective phase difference between the phase position of the first base station and the phase positions of the neighboring base stations is determined.
  • the phase differences can also be averaged according to a further training based on the first further training.
  • the phase difference mean values within the group of neighboring base stations advantageously converge to zero, i.e. the base stations are synchronized with each other.
  • the phase differences are weighted with a respective weighting coefficient. This enables a base station-specific control of the synchronization. For example, a base station can be selected whose phase position has a greater influence due to a larger weighting coefficient has the regulation of the phase position of the other base stations.
  • a respective transmission time is taken into account for the determination of the phase positions. In this way, time differences owing to a different distance between the base stations can advantageously be compensated for and the accuracy of the regulation increased.
  • FIG. 1 shows a block diagram of a radio communication system, in particular a mobile radio system
  • FIG. 2 shows a schematic representation of the frame structure of the
  • FIG. 3 shows an exemplary structure of a number of adjacent base stations BS
  • FIG. 4 shows a block diagram of an exemplary arrangement for
  • the structure of the radio communication system shown in FIG. 1 and exemplarily designed as a mobile radio system corresponds to the known GSM mobile radio system, which consists of a large number of mobile switching centers MSC which are networked with one another or provide access to a fixed network PSTN. Furthermore, these mobile switching centers MSC are each connected to at least one device for the allocation of radio resources RNM. Each of these devices RNM in turn enables a connection to at least one base station BS.
  • This base station BS is a radio station which communicates via a radio interface. Connections to other radio stations, which can be configured as mobile stations MS or stationary subscriber terminals, can set up and trigger.
  • the functionality of this structure is used by the method according to the invention.
  • FIG. 1 shows an example of a radio connection for the transmission of, for example, user data and signaling information between the base station BS and a mobile station MS, which is located in the radio coverage area of the base station BS.
  • FIG. 2 An exemplary frame structure of the radio interface can be seen in FIG. 2.
  • Each time slot ts within the frequency band B forms a frequency channel fk.
  • the successive time slots ts are structured according to a frame structure. In this way, 16 time slots ts0 to tsl5 are combined to form a time frame tf.
  • part of the time slots tsO to tsl5 in the upward direction and part of the time slots tsO to tsl5 in the downward direction are used, the transmission in the upward direction taking place, for example, before the transmission in the downward direction.
  • a switchover point SP which can be flexibly positioned according to the respective need for transmission channels for the up and down direction.
  • a frequency channel fk for the upward direction corresponds to a frequency channel fk for the downward direction.
  • the other frequency channels fk are structured in the same way.
  • Radio blocks consist of sections with data d, in each of which sections with training sequences tseqn known on the reception side are embedded.
  • the data d are spread individually for each connection with a fine structure, a spreading code c (CDMA code), so that, for example, n connections can be separated at the receiving end by this CDMA component.
  • CDMA code spreading code c
  • the combination of a frequency channel fk and a spreading code c defines a physical transmission channel that can be used for the transmission of signaling and useful information. For the transmission of user information, this physical transmission channel is also referred to as a traffic channel.
  • the spreading of individual symbols of the data d with Q chips has the effect that Q subsections of the duration tchip are transmitted within the symbol duration tsym.
  • the Q chips form the individual CDMA code c.
  • a protection time gp is provided within the time slot ts to compensate for different signal delays of the connections of successive time slots ts.
  • each base station for example BS1, receives signals from all respectively neighboring base stations, for example BS2 ... BS4, and uses phase signals derived from these signals to guide the phase position of its own signal transmission.
  • the averaged and weighted phase difference is chosen as the starting point, n the number of neighboring base stations taken into account, ai the respective weighting coefficient of the neighboring base stations, and ⁇ i the estimated phase relationship the respective neighboring base station.
  • the weighting coefficient ai in particular enables individual control of the synchronization. If the respective phase difference ⁇ i for the signals of the neighboring base stations BS2 ... BS5 becomes zero, the averaged phase difference also converges to zero and the base stations are synchronized.
  • FIG. 4 shows the exemplary structure of an arrangement for synchronization in a first base station BS1.
  • the same arrangement can be implemented in the same way in the further base stations BS2 ... BS5.
  • phase positions of the signals received by the neighboring base stations BS2 ... BS5 are each detected in the first base stations BS1 in a phase detector phase detector and a respective phase difference to the signal of the first base station BS1 is determined.
  • the phase relationships can be determined, for example, by means of a so-called matched filter or by means of an estimation algorithm.
  • a respective transmission time of the signals of the neighboring base stations should be in the phase detector BS2 ... BS5 are taken into account or compensated, since otherwise the determination of the respective phase position would be falsified by a different distance of the neighboring base stations BS2 ... BS5 from the first base station BS1.
  • phase differences can be weighted by a weighting coefficient which is individual for the base station, the sum of the weighting coefficients being selected, for example, equal to one in accordance with the formula (2).
  • a weighting coefficient which is individual for the base station, the sum of the weighting coefficients being selected, for example, equal to one in accordance with the formula (2).
  • the ascertained phase differences are averaged in a device for averaging downstream of the phase detector and are subsequently fed to a control device PI regulator, which can be configured, for example, as a PI controller.
  • the control device controls the phase position of the signal transmission from the first base station BS1.
  • the control signal of the control device controls a downstream oscillator device VCO (Voltage Controlled Oscillator), the output signal of which is used for the signal transmission.
  • VCO Voltage Controlled Oscillator
  • the output signal is fed back to the phase detector in the same way and serves as a reference value for determining the phase differences.
  • the output signal is taken into account by the neighboring base stations BS2 ... BS5 for a corresponding control of the phase position, as is represented by the feedback loop via the air interface radio interface.
  • a synchronization sequence in a transmitted data block can be evaluated to determine the phase positions.
  • This can be a sequence specially provided for this purpose or a sequence already available in the system, the sequences being transmitted periodically by the base stations, for example.
  • these synchronization sequences do not have to be sent from the neighboring base stations BS2 ... BS5 at the same time, since the averaging is carried out, for example, only after all phase positions have been determined.

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

Abstract

According to the invention a phase angle of at least two signals transmitted via a radio interface by adjacent base stations is determined in a first base station. These phase angles are then compared with the phase angles of the signals of the first base station and a controlled variable is derived from the comparison. The controlled variable controls the phase angle of the first base station in relation to the phase angles of the adjacent base stations.

Description

Beschreibungdescription
Verfahren und Anordnung zur Synchronisation einer Basisstation eines Funk-KommunikationssystemsMethod and arrangement for synchronizing a base station of a radio communication system
Die Erfindung betrifft ein Verfahren und eine Anordnung zur — Synchronisation einer Basisstation eines Funk-Kommunikationssystems, insbesondere eines Mobilfunksystems.The invention relates to a method and an arrangement for - synchronization of a base station of a radio communication system, in particular a mobile radio system.
In Funk-Kommunikationssystemen werden Informationen wie beispielsweise Sprache, Bildinformationen oder andere Daten, mit Hilfe von elektromagnetischen Wellen über eine Funkschnittstelle zwischen einer sendenden und einer empfangenden Funkstation, wie beispielsweise einer Basisstation bzw. Funksta- tion, übertragen. Das Abstrahlen der elektromagnetischen Wellen erfolgt dabei mit Trägerfrequenzen, die in dem für das jeweilige System vorgesehenen Frequenzband liegen. Beim GSM (Global System for Mobile Communication) , das unter anderem aus J. Biala „Mobilfunk und Intelligente Netze"", Vieweg Ver- lag, 1995, bekannt ist, liegen die Trägerfrequenzen im Bereich von 900 MHz, 1800 MHz und 1900 MHz. Für zukünftige Mobilfunksysteme mit CDMA- oder TD/CDMA- Übertragungsverfahren über die Funkschnittstelle, wie beispielsweise das UMTS (Universal Mobile Telecommunication System) oder andere Systeme der 3. Generation sind Frequenzen im Frequenzband von ca. 2000 MHz vorgesehen.In radio communication systems, information such as voice, image information or other data is transmitted with the aid of electromagnetic waves via a radio interface between a transmitting and a receiving radio station, such as a base station or radio station. The electromagnetic waves are emitted at carrier frequencies that lie in the frequency band provided for the respective system. In GSM (Global System for Mobile Communication), which is known from J. Biala "Mobile Communications and Intelligent Networks", Vieweg Verlag, 1995, among others, the carrier frequencies are in the range of 900 MHz, 1800 MHz and 1900 MHz. For future mobile radio systems with CDMA or TD / CDMA transmission methods via the radio interface, such as the UMTS (Universal Mobile Telecommunication System) or other 3rd generation systems, frequencies in the frequency band of approximately 2000 MHz are provided.
Für eine Minimierung von Interferenzbeeinflussung durch benachbarte Basisstationen des Funk-Kommunikationssystems, die ein gemeinsames Frequenzband nutzen, soll durch eine Vernetzung von mehreren Basisstationen eine Synchronität der Signalübertragung auf der Funkschnittstelle erreicht werden. Diese Synchronität wird insbesondere für Funk-Kommunikationssysteme mit einer Teilnehmerseparierung gemäß einem TDMA-Ver- fahren (Time Division Multiple Access) und einer Informa- tionsübertragung gemäß einem TDD-Verfahren (Time Division Du- plex) angestrebt, um eine homogene Zeitschlitzstruktur zu erhalten. Eine Synchronität der Basisstationen wird jedoch auch in bekannten Funk-Kommunikationssystemen, die ein CDMA-Teil- nehmerseparierungsverfahren in Verbindung mit einem FDD-Verfahren nutzen, angestrebt.In order to minimize interference interference by neighboring base stations of the radio communication system that use a common frequency band, a synchronism of the signal transmission on the radio interface is to be achieved by networking several base stations. This synchronicity is particularly important for radio communication systems with a subscriber separation according to a TDMA method (Time Division Multiple Access) and an information tion transmission according to a TDD method (Time Division Duplex) in order to obtain a homogeneous time slot structure. However, synchronism of the base stations is also sought in known radio communication systems which use a CDMA subscriber separation method in conjunction with an FDD method.
Gemäß dem Stand der Technik werden allgemein für die Synchronisation hierarchische Master/Slave-Strukturen herangezo- gen, bei denen ausgehend von einer sogenannten Master- Basisstation die umliegenden Slave-Basisstationen mit einem zentralen Taktsignal versorgt werden. Nachteilig tritt bei diesem Konzept ein erhöhter technischer und organisatorischer Aufwand für die Infrastruktur des Netzes auf. Eine weitere bekannte Maßnahme zur Synchronisierung von Basisstationen ist die Verwendung eines GPS-Signals (Global Positioning System) , auf das sich alle Basisstationen synchronisieren. Hierzu werden alle Basisstationen mit einem GPS-Empfänger ausgerüstet, welches nachteilig zu einer deutlichen Kostenerhöhung führt, da auch sogenannte Mikrobasisstationen mit einem derartigen Empfänger ausgerüstet werden müssen. Weiterhin muß sichergestellt werden, daß die Basisstationen jeweils eine Sichtverbindung zu den Satelliten aufweisen. Hierzu müßte bei in Gebäuden installierten Basisstationen eine Antenneneinrichtung zum Sicherstellen des Empfangs der GPS-Signale aus dem Gebäude herausgeführt werden, welches wiederum einen hohen technischen Aufwand bedeutet.According to the prior art, hierarchical master / slave structures are generally used for the synchronization, in which, starting from a so-called master base station, the surrounding slave base stations are supplied with a central clock signal. A disadvantage of this concept is an increased technical and organizational effort for the network infrastructure. Another known measure for the synchronization of base stations is the use of a GPS signal (Global Positioning System) to which all base stations synchronize. For this purpose, all base stations are equipped with a GPS receiver, which disadvantageously leads to a significant increase in costs, since so-called micro base stations must also be equipped with such a receiver. Furthermore, it must be ensured that the base stations each have a line of sight to the satellites. For this purpose, in the case of base stations installed in buildings, an antenna device for ensuring the reception of the GPS signals would have to be led out of the building, which in turn means a high technical outlay.
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Anordnung anzugeben, die eine vereinfachte Synchronisation einer Anzahl von Basisstationen eines Funk-Kommunikationssystems ermöglichen. Diese Aufgabe wird durch das Verfahren gemäß den Merkmalen des Anspruchs 1 sowie durch die Basisstation gemäß den Merkmalen des Anspruchs 6 gelöst. Wei- terbildungen sind in den abhängigen Ansprüchen offenbart. Erfindungsgemäß wird in einer ersten Basisstation eine jeweilige Phasenlage von zumindest zwei von benachbarten Basisstationen über eine Funkschnittstelle gesendeten Signalen ermittelt. Nachfolgend werden die Phasenlagen mit der Phasenlage der Signale der ersten Basisstation verglichen und aus dem Vergleich eine Regelgröße abgeleitet. Diese Regelgröße steuert die Phasenlage der ersten Basisstation im Verhältnis zu den Phasenlagen der benachbarten Basisstationen.The invention has for its object to provide a method and an arrangement that allow simplified synchronization of a number of base stations of a radio communication system. This object is achieved by the method according to the features of claim 1 and by the base station according to the features of claim 6. Further developments are disclosed in the dependent claims. According to the invention, a respective phase position of at least two signals transmitted by neighboring base stations via a radio interface is determined in a first base station. The phase positions are then compared with the phase position of the signals of the first base station and a controlled variable is derived from the comparison. This controlled variable controls the phase position of the first base station in relation to the phase positions of the neighboring base stations.
Vorteilhaft wird durch dieses Verfahren sichergestellt, daß sich jede Basisstation auf die benachbarten Basisstationen synchronisiert, wodurch auf eine hierarchische Struktur zur Synchronisierung entsprechend dem beschriebenen Stand der Technik verzichtet werden kann. In dem Netzwerk der Basisstationen existiert somit keine taktangebende Instanz. Weiterhin kann sich jede neu installierte Basisstation auf die umliegenden Basisstationen synchronisieren.This method advantageously ensures that each base station synchronizes with the neighboring base stations, as a result of which a hierarchical structure for synchronization in accordance with the described prior art can be dispensed with. There is therefore no clock-providing instance in the network of the base stations. Furthermore, each newly installed base station can synchronize with the surrounding base stations.
Gemäß einer ersten Weiterbildung des erfindungsgemäßen Verfahrens wird eine jeweilige Phasendifferenz zwischen der Phasenlage der ersten Basisstation und den Phasenlagen der benachbarten Basisstationen ermittelt. Die Phasendifferenzen können weiterhin gemäß einer auf der ersten Weiterbildung ba- sierenden Weiterbildung gemittelt werden. Vorteilhaft konvergieren die Phasendifferenzmittelwerte innerhalb der Gruppe benachbarter Basisstationen gegen Null, d.h. die Basisstationen sind zueinander synchron.According to a first development of the method according to the invention, a respective phase difference between the phase position of the first base station and the phase positions of the neighboring base stations is determined. The phase differences can also be averaged according to a further training based on the first further training. The phase difference mean values within the group of neighboring base stations advantageously converge to zero, i.e. the base stations are synchronized with each other.
Einer weiteren Weiterbildung zufolge werden die Phasendifferenzen mit einem jeweiligen Gewichtungskoeffizienten gewich- tet. Hierdurch wird eine basisstationsindividuelle Steuerung der Synchronisation ermöglicht. So kann beispielsweise eine Basisstation ausgewählt werden, deren Phasenlage durch einen größeren Gewichtungskoeffizienten einen stärkeren Einfluß auf die Regelung der Phasenlage der weiteren Basisstationen besitzt.According to a further development, the phase differences are weighted with a respective weighting coefficient. This enables a base station-specific control of the synchronization. For example, a base station can be selected whose phase position has a greater influence due to a larger weighting coefficient has the regulation of the phase position of the other base stations.
Gemäß einer weiteren Weiterbildung der Erfindung wird für die Ermittlung der Phasenlagen eine jeweilige Übertragungszeit berücksichtigt. Hierdurch können vorteilhaft Zeitdifferenzen_ aufgrund einer unterschiedlichen Entfernung zwischen den Basisstationen ausgeglichen und die genauigkeit der Regelung erhöht werden.According to a further development of the invention, a respective transmission time is taken into account for the determination of the phase positions. In this way, time differences owing to a different distance between the base stations can advantageously be compensated for and the accuracy of the regulation increased.
Ausführungsbeispiele der Erfindung werden anhand der beiliegenden Zeichnungen näher erläutert.Embodiments of the invention are explained in more detail with reference to the accompanying drawings.
Dabei zeigenShow
FIG 1 ein Blockschaltbild eines Funk-Kommunikationssystems, insbesondere eines Mobilfunksystems, FIG 2 eine schematische Darstellung der Rahmenstruktur der1 shows a block diagram of a radio communication system, in particular a mobile radio system, FIG. 2 shows a schematic representation of the frame structure of the
Funkschnittstelle und des Aufbaus eines Funkblocks, FIG 3 eine beispielhafte Struktur einer Anzahl von jeweils benachbarten Basisstationen BS, und FIG 4 ein Blockschaltbild einer bespielhaften Anordnung zurRadio interface and the structure of a radio block, FIG. 3 shows an exemplary structure of a number of adjacent base stations BS, and FIG. 4 shows a block diagram of an exemplary arrangement for
Synchronisation in einer Basistation BS .Synchronization in a base station BS.
Das in FIG 1 dargestellte und beispielhaft als ein Mobilfunksystem ausgestaltete Funk-Kommunikationssystem entspricht in seiner Struktur dem bekannten GSM-Mobilfunksystem, das aus einer Vielzahl von Mobilvermittlungsstellen MSC besteht, die untereinander vernetzt sind bzw. den Zugang zu einem Festnetz PSTN herstellen. Weiterhin sind diese Mobilvermittlungsstellen MSC mit jeweils zumindest einer Einrichtung zur Zuweisung funktechnischer Ressourcen RNM verbunden. Jede dieser Einrichtungen RNM ermöglicht wiederum eine Verbindung zu zumindest einer Basisstation BS . Diese Basisstation BS ist eine Funkstation, die über eine Funkschnittstelle Kommunikations- Verbindungen zu weiteren Funkstationen, die als Mobilstationen MS oder stationäre Teilnehmerendgeräte ausgestaltet sein können, aufbauen und auslösen kann. Die Funktionalität dieser Struktur wird von dem erfindungsgemäßen Verfahren genutzt.The structure of the radio communication system shown in FIG. 1 and exemplarily designed as a mobile radio system corresponds to the known GSM mobile radio system, which consists of a large number of mobile switching centers MSC which are networked with one another or provide access to a fixed network PSTN. Furthermore, these mobile switching centers MSC are each connected to at least one device for the allocation of radio resources RNM. Each of these devices RNM in turn enables a connection to at least one base station BS. This base station BS is a radio station which communicates via a radio interface. Connections to other radio stations, which can be configured as mobile stations MS or stationary subscriber terminals, can set up and trigger. The functionality of this structure is used by the method according to the invention.
In FIG 1 ist beispielhaft eine Funkverbindungen zur Übertra-- gung von beispielsweise Nutzdaten und Signalisierungsinforma- tionen zwischen der Basisstation BS und einer Mobilstation MS dargestellt, die sich in dem Funkversorgungsgebiet der Basis- Station BS befindet.1 shows an example of a radio connection for the transmission of, for example, user data and signaling information between the base station BS and a mobile station MS, which is located in the radio coverage area of the base station BS.
Eine beispielhafte Rahmenstruktur der Funkschnittstelle ist aus der FIG 2 ersichtlich. Gemäß einer TDMA-Komponente ist eine Aufteilung eines breitbandigen Frequenzbandes, bei- spielsweise der Bandbreite B = 5 MHz, in mehrere Zeitschlitze ts, beispielsweise 16 Zeitschlitze tsO bis tsl5 vorgesehen. Jeder Zeitschlitz ts innerhalb des Frequenzbandes B bildet einen Frequenzkanal fk. Innerhalb eines breitbandigen Frequenzbandes B werden die aufeinanderfolgenden Zeitschlitze ts nach einer Rahmenstruktur gegliedert. So werden 16 Zeitschlitze tsO bis tsl5 zu einem Zeitrahmen tf zusammengefaßt.An exemplary frame structure of the radio interface can be seen in FIG. 2. According to a TDMA component, a division of a broadband frequency band, for example the bandwidth B = 5 MHz, into a plurality of time slots ts, for example 16 time slots tsO to tsl5, is provided. Each time slot ts within the frequency band B forms a frequency channel fk. Within a broadband frequency band B, the successive time slots ts are structured according to a frame structure. In this way, 16 time slots ts0 to tsl5 are combined to form a time frame tf.
Bei einer Nutzung eines TDD-Übertragungsverfahrens wird ein Teil der Zeitschlitze tsO bis tsl5 in Aufwärtsrichtung und ein Teil der Zeitschlitze tsO bis tsl5 in Abwärtsrichtung benutzt, wobei die Übertragung in Aufwärtsrichtung beispielsweise vor der Übertragung in Abwärtsrichtung erfolgt. Dazwischen liegt ein Umschaltzeitpunkt SP, der entsprechend dem jeweiligen Bedarf an Übertragungskanälen für die Auf- und Ab- wärtsrichtung flexibel positioniert werden kann. Ein Frequenzkanal fk für die Aufwärtsrichtung entspricht in diesem Fall einem Frequenzkanal fk für die Abwärtsrichtung. In gleicher Weise sind die weiteren Frequenzkanäle fk strukturiert. Innerhalb der Frequenzkanäle fk werden Informationen mehrererWhen using a TDD transmission method, part of the time slots tsO to tsl5 in the upward direction and part of the time slots tsO to tsl5 in the downward direction are used, the transmission in the upward direction taking place, for example, before the transmission in the downward direction. In between is a switchover point SP, which can be flexibly positioned according to the respective need for transmission channels for the up and down direction. In this case, a frequency channel fk for the upward direction corresponds to a frequency channel fk for the downward direction. The other frequency channels fk are structured in the same way. Within the frequency channels fk information of several
Verbindungen in Funkblöcken übertragen. Diese Funkblöcke bestehen aus Abschnitten mit Daten d, in denen jeweils Abschnitte mit empfangsseitig bekannten Trainingssequenzen tseqn eingebettet sind. Die Daten d sind verbindungsindividu- ell mit einer Feinstruktur, einem Spreizkode c (CDMA-Kode) , - - gespreizt, so daß empfangsseitig beispielsweise n Verbindungen durch diese CDMA-Komponente separierbar sind. Die Kombination aus einem Frequenzkanal fk und einem Spreizkode c de- finiert einen physikalischen Übertragungskanal, der für die Übertragung von Signalisierungs- und Nutzinformationen genutzt werden kann. Für die Übertragung von Nutzinformationen wird dieser physikalische Übertragungskanal auch als Verkehrskanal (Traffic Channel) bezeichnet.Transfer connections in radio blocks. These radio blocks consist of sections with data d, in each of which sections with training sequences tseqn known on the reception side are embedded. The data d are spread individually for each connection with a fine structure, a spreading code c (CDMA code), so that, for example, n connections can be separated at the receiving end by this CDMA component. The combination of a frequency channel fk and a spreading code c defines a physical transmission channel that can be used for the transmission of signaling and useful information. For the transmission of user information, this physical transmission channel is also referred to as a traffic channel.
Die Spreizung von einzelnen Symbolen der Daten d mit Q Chips bewirkt, daß innerhalb der Symboldauer tsym Q Subabschnitte der Dauer tchip übertragen werden. Die Q Chips bilden dabei den individuellen CDMA-Kode c. Weiterhin ist innerhalb des Zeitschlitzes ts eine Schutzzeit gp zur Kompensation unterschiedlicher Signalaufzeiten der Verbindungen aufeinanderfolgender Zeitschlitze ts vorgesehen.The spreading of individual symbols of the data d with Q chips has the effect that Q subsections of the duration tchip are transmitted within the symbol duration tsym. The Q chips form the individual CDMA code c. Furthermore, a protection time gp is provided within the time slot ts to compensate for different signal delays of the connections of successive time slots ts.
In der FIG 3 ist beispielhaft eine Anordnung von fünf benach- barten Basisstationen BS1...BS5 dargestellt. Wie die Pfeile verdeutlichen sollen, empfängt jede Basisstation, beispielsweise BSl, Signale von allen jeweils benachbarten Basisstationen, beispielsweise BS2...BS4, und leitet mittels aus diesen Signalen abgeleiteten Phasenlagen die Phasenlage der ei- genen Signalaussendung .3 shows an example of an arrangement of five neighboring base stations BS1 ... BS5. As the arrows are intended to illustrate, each base station, for example BS1, receives signals from all respectively neighboring base stations, for example BS2 ... BS4, and uses phase signals derived from these signals to guide the phase position of its own signal transmission.
Die Synchronisierung der Basisstationen erfolgt dabei gemäß folgender mathematischer Grundlage: n φ = Σ ai Ψi i = 1The base stations are synchronized according to the following mathematical basis: n φ = Σ ai Ψi i = 1
n mit ^ aj = 1 ( 2 ) i = ln with ^ aj = 1 (2) i = l
mit φ dem Ausgangspunkt für die Regelung, im Falle von (1) wird die gemittelte und gewichtete Phasendifferenz als Ausgangspunkt gewählt, n der Anzahl der berücksichtigten benachbarten Basisstationen, ai dem jeweilige Gewichtungskoef- fizient der benachbarten Basisstationen, und φi der geschätz- ten Phasenbeziehung zu der jeweiligen benachbarten Basisstation. Durch den Gewichtungskoeffizienten ai ist insbesondere eine individuelle Steuerung der Synchronisation möglich. Wird die jeweilige Phasendifferenz φi zu den Signalen der benachbarten Basisstationen BS2...BS5 zu Null, so konvergiert auch die gemittelte Phasendifferenz zu Null und die Basisstationen sind synchronisiert.with φ the starting point for the control, in the case of (1) the averaged and weighted phase difference is chosen as the starting point, n the number of neighboring base stations taken into account, ai the respective weighting coefficient of the neighboring base stations, and φi the estimated phase relationship the respective neighboring base station. The weighting coefficient ai in particular enables individual control of the synchronization. If the respective phase difference φi for the signals of the neighboring base stations BS2 ... BS5 becomes zero, the averaged phase difference also converges to zero and the base stations are synchronized.
In der FIG 4 ist die beispielhafte Struktur einer Anordnung zur Synchronisation in einer ersten Basisstation BS1 darge- stellt. Eine gleiche Anordnung kann in gleicher Weise in den weiteren Basisstationen BS2... BS5 verwirklicht sein.FIG. 4 shows the exemplary structure of an arrangement for synchronization in a first base station BS1. The same arrangement can be implemented in the same way in the further base stations BS2 ... BS5.
Die Phasenlagen der von den benachbarten Basisstationen BS2...BS5 empfangenen Signale werden jeweils in der ersten Basisstationen BS1 in einem Phasendetektor Phase detector de- tektiert und eine jeweilige Phasendifferenz zu dem Signal der ersten Basisstation BS1 ermittelt. Die Phasenbeziehungen können dabei beispielsweise mittels eines sogenannten Matched Filters oder mittels eines Schätzalgorithmus bestimmt werden. Zusätzlich sollte in dem Phasendetektor eine jeweilige Übertragungszeit der Signale der benachbarten Basisstationen BS2...BS5 berücksichtigt bzw. kompensiert werden, da ansonsten die Ermittlung der jeweiligen Phasenlage durch eine unterschiedliche Entfernung der benachbarten Basisstationen BS2...BS5 zu der ersten Basisstation BS1 verfälscht würde. Weiterhin können die Phasendifferenzen durch einen basissta- tionsindividuellen Gewichtungskoeffizienten gewichtet werden, wobei die Summe der Gewichtungskoeffizienten entsprechend der Formel (2) beispielsweise gleich eins gewählt wird. Hierdurch können eine oder mehrere benachbarte Basisstationen einen größeren Einfluß auf die Regelung der Phasenlage in der ersten Basisstation BS1 besitzen.The phase positions of the signals received by the neighboring base stations BS2 ... BS5 are each detected in the first base stations BS1 in a phase detector phase detector and a respective phase difference to the signal of the first base station BS1 is determined. The phase relationships can be determined, for example, by means of a so-called matched filter or by means of an estimation algorithm. In addition, a respective transmission time of the signals of the neighboring base stations should be in the phase detector BS2 ... BS5 are taken into account or compensated, since otherwise the determination of the respective phase position would be falsified by a different distance of the neighboring base stations BS2 ... BS5 from the first base station BS1. Furthermore, the phase differences can be weighted by a weighting coefficient which is individual for the base station, the sum of the weighting coefficients being selected, for example, equal to one in accordance with the formula (2). As a result, one or more neighboring base stations can have a greater influence on the regulation of the phase position in the first base station BS1.
In einer dem Phasendetektor nachgeschalteten Einrichtung zur Mittelung Mean werden die ermittelten Phasendifferenzen ge- mittelt und nachfolgend einer Steuereinrichtung PI-Regulator zugeführt, die beispielsweise als ein PI-Regler ausgestaltet sein kann. Die Steuereinrichtung steuert die Phasenlage der Signalaussendung der ersten Basisstation BS1.The ascertained phase differences are averaged in a device for averaging downstream of the phase detector and are subsequently fed to a control device PI regulator, which can be configured, for example, as a PI controller. The control device controls the phase position of the signal transmission from the first base station BS1.
Das Steuersignal der Steuereinrichtung steuert eine nachgeschaltete Oszillatoreinrichtung VCO (Voltage Controlled Oscillator) an, dessen Ausgangssignal für die Signalaussendung genutzt wird. Das Ausgangssignal wird in gleicher Weise zu dem Phasendetektor zurückgekoppelt und dient als Referenz- wert für die Ermittlung der Phasendifferenzen.The control signal of the control device controls a downstream oscillator device VCO (Voltage Controlled Oscillator), the output signal of which is used for the signal transmission. The output signal is fed back to the phase detector in the same way and serves as a reference value for determining the phase differences.
Das Ausgangssignal wird neben Signalen von weiteren Basisstationen im Sinne einer Regelschleife von den benachbarten Basisstationen BS2...BS5 für eine entsprechende Steuerung der Phasenlage berücksichtigt, wie es durch die Rückkopplungsschleife über die Funkschnittstelle Air Interface dargestellt wird.In addition to signals from other base stations in the sense of a control loop, the output signal is taken into account by the neighboring base stations BS2 ... BS5 for a corresponding control of the phase position, as is represented by the feedback loop via the air interface radio interface.
Vorteilhaft wird durch die Realisierung der Synchronisation in der Art einer PLL (Phase Locked Loop) eine Regelung ermög- licht, die neben der Phasendomäne auch eine Auswertung derRegulation is advantageously made possible by implementing synchronization in the manner of a PLL (Phase Locked Loop). light, which in addition to the phase domain also an evaluation of the
Frequenzdomäne erlaubt.Frequency domain allowed.
Für die Bestimmung der Phasenlagen kann eine Synchronisie- rungssequenz in einem übertragenen Datenblock (burst) ausgewertet werden. Dieses kann eine speziell dafür vorgesehene Sequenz oder eine bereits in dem System zur Verfügung stehende Sequenz sein, wobei beispielsweise eine periodische Ausendung der Sequenzen durch die Basisstationen erfolgt. Vor- teilhaft müssen diese Synchronisationssequenzen nicht zeitgleich von den benachbarten Basisstationen BS2...BS5 gesendet werden, da die Mittelung beispielsweise erst nach Ermittlung aller Phasenlagen durchgeführt wird. A synchronization sequence in a transmitted data block (burst) can be evaluated to determine the phase positions. This can be a sequence specially provided for this purpose or a sequence already available in the system, the sequences being transmitted periodically by the base stations, for example. Advantageously, these synchronization sequences do not have to be sent from the neighboring base stations BS2 ... BS5 at the same time, since the averaging is carried out, for example, only after all phase positions have been determined.

Claims

Patentansprüche claims
1. Verfahren zur Synchronisation einer Basisstation (BSl) eines Funk-Kommunikationssystems, bei dem in einer ersten Basisstation (BSl) eine jeweilige Phasen- läge von zumindest zwei von benachbarten Basisstationen1. Method for synchronizing a base station (BSl) of a radio communication system, in which in a first base station (BSl) a respective phase position of at least two of neighboring base stations
(BS2, BS3...) über eine Funkschnittstelle (Air Interface) gesendeten Signalen ermittelt wird, die jeweilige Phasenlage der Signale der benachbarten Basisstationen (BS2, BS3...) mit der Phasenlage von Signalen der ersten Basisstation (BSl) verglichen wird, und aus dem Vergleich eine Regelgröße abgeleitet wird, die die Phasenlage der ersten Basisstation (BSl) im Verhältnis zu den Phasenlagen der benachbarten Basisstationen (BS2, BS3... ) steuert.(BS2, BS3 ...) via signals sent via a radio interface (Air Interface), the respective phase position of the signals of the neighboring base stations (BS2, BS3 ...) is compared with the phase position of signals of the first base station (BSl), and a control variable is derived from the comparison, which controls the phase position of the first base station (BS1) in relation to the phase positions of the neighboring base stations (BS2, BS3 ...).
2. Verfahren nach dem vorhergehenden Anspruch, bei dem eine jeweilige Phasendifferenz zwischen der Phasenlage der ersten Basisstation (BSl) und den Phasenlagen der benachbarten Basisstationen (BS2, BS3...) ermittelt wird.2. The method according to the preceding claim, in which a respective phase difference between the phase position of the first base station (BS1) and the phase positions of the adjacent base stations (BS2, BS3 ...) is determined.
3. Verfahren nach dem vorhergehenden Anspruch, bei dem die ermittelten Phasendifferenzen gemittelt werden.3. The method according to the preceding claim, in which the determined phase differences are averaged.
4. Verfahren nach Anspruch 2 oder 3, bei dem die Phasendifferenzen mit einem jeweiligen Gewichtungskoeffizienten gewichtet werden.4. The method of claim 2 or 3, wherein the phase differences are weighted with a respective weighting coefficient.
5. Verfahren nach einem vorhergehenden Anspruch, bei dem für die Ermittlung der Phasenlagen eine jeweilige Übertragungszeit berücksichtigt wird.5. The method according to any preceding claim, in which a respective transmission time is taken into account for the determination of the phase positions.
6. Basisstation (BSl) eines Funk-Kommunikationssystems, die eine Anordnung zur Synchronisation bestehend aus einem Phasendetektor (Phase detector) für eine Phasende- tektion von zumindest zwei von benachbarten Basisstationen (BS2, BS3...) über eine Funkschnittstelle übertragenen Signalen und zur Ermittlung einer jeweiligen Differenz zwi- sehen der Phasenlage der ersten Basisstation (BSl) und den Phasenlagen der benachbarten Basisstationen (BS2, BS3...), eine dem Phasendetektor (Phase detector) nachgeschaltete Einrichtung (Mean) zur Mittelung der ermittelten Phasendifferenzen, - eine Steuereinrichtung (PI-Regulator) zur Steuerung der Phasenlage der ersten Basisstation (BSl), und eine der Steuereinrichtung (PI-Regulator) nachgeschaltete Oszillatoreinrichtung (VCO) , dessen Ausgangssignal für die Signalübertragung von der ersten Basisstation (BSl) ver- wendet wird, und das zu dem Phasendetektor (Phase detector) zurückgekoppelt wird, aufweist . 6. Base station (BSl) of a radio communication system, which consists of an arrangement for synchronization a phase detector for a phase detection of at least two signals transmitted from neighboring base stations (BS2, BS3 ...) via a radio interface and for determining a respective difference between the phase position of the first base station (BSl) and the phase positions of the neighboring base stations (BS2, BS3 ...), a device (Mean) connected downstream of the phase detector (phase) for averaging the determined phase differences, - a control device (PI regulator) for controlling the phase position of the first base station (BSl), and an oscillator device (VCO) connected downstream of the control device (PI regulator), the output signal of which is used for signal transmission from the first base station (BS1) and which is fed back to the phase detector.
PCT/DE2000/000763 1999-03-11 2000-03-10 Method and system for synchronizing a base station of a radio communications system WO2000054435A1 (en)

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