WO2000003500A1 - Procede et appareil de determination des intervalles de temps optimaux entre les canaux de communications - Google Patents

Procede et appareil de determination des intervalles de temps optimaux entre les canaux de communications Download PDF

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Publication number
WO2000003500A1
WO2000003500A1 PCT/SE1999/001269 SE9901269W WO0003500A1 WO 2000003500 A1 WO2000003500 A1 WO 2000003500A1 SE 9901269 W SE9901269 W SE 9901269W WO 0003500 A1 WO0003500 A1 WO 0003500A1
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WIPO (PCT)
Prior art keywords
rate
remote station
frames
elapsed
remote
Prior art date
Application number
PCT/SE1999/001269
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English (en)
Inventor
Bela Rathonyl
Original Assignee
Telefonaktiebolaget Lm Ericsson (Publ)
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.)
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Publication date
Application filed by Telefonaktiebolaget Lm Ericsson (Publ) filed Critical Telefonaktiebolaget Lm Ericsson (Publ)
Priority to AU53896/99A priority Critical patent/AU5389699A/en
Publication of WO2000003500A1 publication Critical patent/WO2000003500A1/fr

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W56/00Synchronisation arrangements
    • H04W56/004Synchronisation arrangements compensating for timing error of reception due to propagation delay
    • H04W56/0045Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by altering transmission time
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/24Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H04B7/2662Arrangements for Wireless System Synchronisation
    • H04B7/2671Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
    • H04B7/2678Time synchronisation
    • H04B7/2681Synchronisation of a mobile station with one base station
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W92/00Interfaces specially adapted for wireless communication networks
    • H04W92/04Interfaces between hierarchically different network devices
    • H04W92/10Interfaces between hierarchically different network devices between terminal device and access point, i.e. wireless air interface

Definitions

  • This invention relates generally to electrical telecommunication and more particularly to selecting time differences between wireless communication channels and even more particularly to methods and apparatus for selecting optimal time differences between uplink and downlink radio channels to maximize use of resources.
  • Modern communication systems such as cellular and satellite radio systems, employ various modes of operation (analog, digital, dual mode, etc.), and access techniques such as frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and hybrids of these techniques.
  • FDMA frequency division multiple access
  • TDMA time division multiple access
  • CDMA code division multiple access
  • Microcell generally refers to a cell having a size comparable to the sizes of cells in a conventional cellular telephone system (e.g., a radius of at least about 1 kilometer), and the terms “microceH” and “picocell” generally refer to progressively smaller cells.
  • a microcell might cover a public indoor or outdoor area, e.g., a convention center or a busy street, and a picocell might cover an office corridor or a floor of a high-rise building.
  • FIG. 1 is an exemplary hierarchical, or multi-layered, cellular system.
  • An umbrella macrocell 10 represented by a hexagonal shape makes up an overlying cellular structure.
  • Each umbrella cell may contain an underlying microcell structure.
  • the umbrella cell 10 includes microcell 20 represented by the area enclosed within the dotted line and microcell 30 represented by the area enclosed within the dashed line corresponding to areas along city streets, and picocells 40, 50, and 60, which cover individual floors of a building.
  • the intersection of the two city streets covered by the microcells 20 and 30 may be an area of dense traffic concentration, and thus might represent a hot spot.
  • FIG. 2 is a block diagram of an exemplary cellular mobile radiotelephone system, including an exemplary base station 110 and mobile station 120.
  • the base station includes a control and processing unit 130 which is connected to a mobile switching center (MSC) 140 which in turn is connected to the public switched telephone network (PSTN) (not shown).
  • MSC mobile switching center
  • PSTN public switched telephone network
  • the base station 110 handles a plurality of voice channels through a voice channel transceiver 150, which is controlled by the control and processing unit 130.
  • each base station includes a control channel transceiver 160, which may be capable of handling more than one control channel.
  • the control channel transceiver 160 is controlled by the control and processing unit 130.
  • the control channel transceiver 160 broadcasts control information over the control channel of the base station or cell to mobiles locked to that control channel. It will be understood that the transceivers 150 and 160 can be implemented as a single device, like the voice and control transceiver 170, for use with control and traffic channels that share the same radio carrier.
  • the mobile station 120 receives the information broadcast on a control channel at its voice and control channel transceiver 170. Then, the processing unit 180 evaluates the received control channel information, which includes the characteristics of cells that are candidates for the mobile station to lock on to, and determines on which cell the mobile should lock.
  • the received control channel information not only includes absolute information concerning the cell with which it is associated, but also contains relative information concerning other cells proximate to the cell with which the control channel is associated, as described for example in U.S. Patent No. 5,353,332 to Raith et al., entitled "Method and Apparatus for Communication Control in a Radiotelephone System".
  • D-AMPS digital advanced mobile phone service
  • TIA/EIA/IS-136 published by the Telecommunications Industry Association and Electronic Industries Association
  • TIA/EIA Telecommunications Industry Association and Electronic Industries Association
  • PCS 1900 EIA SP 3389 standard
  • the PCS 1900 standard is an implementation of the GSM system, which is common outside North America, that has been introduced for personal communication services (PCS) systems.
  • next generation systems are currently under discussion in various standards setting organizations, which include the International Telecommunications Union (ITU), the European Telecommunications Standards Institute (ETSI), and Japan's Association of Radio Industries and Businesses (ARIB).
  • ITU International Telecommunications Union
  • ETSI European Telecommunications Standards Institute
  • ARIB Japan's Association of Radio Industries and Businesses
  • packet data networks that are also usually designed and based on industry-wide data standards such as the open system interface (OSI) model or the transmission control protocol/Internet protocol (TCP/IP) stack.
  • OSI open system interface
  • TCP/IP transmission control protocol/Internet protocol
  • each radio channel is divided into a series of time slots, each of which contains a block of information from a user.
  • the time slots are grouped into successive frames that each have a predetermined duration, and successive frames may be grouped into a succession of what are usually called superframes.
  • the kind of access technique (e.g., TDMA or CDMA) used by a communication system affects how user information is represented in the slots and frames, but current access techniques all use a slot/frame structure.
  • Time slots assigned to the same user which may not be consecutive time slots on the radio carrier, may be considered a logical channel assigned to the user.
  • a predetermined number of digital bits are transmitted according to the particular access technique (e.g., CDMA) used by the system.
  • cellular radio communication systems also provide logical channels for control messages, such as paging/access channels for call-setup messages exchanged by base stations and mobile stations.
  • an air interface protocol is required in order to allow a mobile station to communicate with the base stations and an MSC.
  • the air interface protocol is used to initiate and to receive cellular telephone calls and is defined in the communications industry by Layer 1 (physical layer), Layer 2 (link layer), and Layer 3 (radio resource control (RRC) layer).
  • Layer 1 physical layer
  • Layer 2 link layer
  • RRC radio resource control
  • the functionality of a Layer 2 includes the delimiting, or framing, of Layer 3 messages, which may be sent between communicating Layer 3 peer entities residing within mobile stations and cellular switching systems.
  • the physical layer (Layer 1) defines the parameters of the physical communications channel, e.g., carrier radio frequency spacing, modulation characteristics, etc.
  • Layer 2 defines the techniques necessary for the accurate transmission of information within the constraints of the physical channel, e.g., error correction and detection, etc.
  • Layer 3 defines the procedures for reception and processing of information transmitted over the physical channel.
  • TIA/EIA IS-136 and TIA/EIA/IS-95 for example specify air interface protocols.
  • FIG. 3 schematically illustrates pluralities of Layer 3 messages 11, Layer 2 frames 13, and Layer 1 time slots, or channel blocks, 15.
  • groups of time slots corresponding to Layer 3 messages may constitute a logical channel, and as described above, the time slots for a given Layer 3 message would usually not be consecutive slots on a carrier. On the other hand, the time slots could be consecutive; as soon as one time slot ends, the next time slot could begin.
  • FIG. 4 shows a general example of a channel configured as a succession of time slots 1, 2, . . . , i in each of a succession of frames 1, 2, . . ., j that would be sent on a carrier signal. Each group of j frames might constitute a superframe. It will be appreciated that this description does not change significantly for TDMA and CDMA techniques.
  • a feature of many systems is that the rates at which both the MS and the BS can transmit user information bits can be different for different channels in the system and can change from time to time even within a channel, for example in response to changes in the amount of information to be transmitted.
  • the rate is sometimes permitted to change only at the beginnings of frames and must keep a constant value throughout an entire frame. This is typical of the third generation system currently being considered by ARIB.
  • An MS is allocated a set of different rates that can be used for the transmission of information bits.
  • the BS controls the allocation of the rate for each channel and sends messages to the MS to inform the MS which rates it is allowed to use. Such a message can be sent by a BS in each frame it transmits.
  • the slot/frame structure of a BS will be temporally offset from the slot/frame structure of a MS.
  • the processor in an MS needs some time to prepare each frame.
  • an apparatus for selecting an optimal time difference between frames of communication channels between a base station and a remote station includes a device for determining an internal delay of the remote station and a device for transmitting messages to the base station in frames that begin at times based on the internal delay.
  • the apparatus may employ channels that are implemented on radio frequency carrier signals and the time difference may be selected so that radio resources of the communication system are used maximally.
  • the device that determines the internal delay may further include a device for configuring the remote station for communication at a first transmission rate; a device for providing a rate-change message to the remote terminal; a device for measuring a time elapsed until the remote station's configuration has changed to a second transmission rate in accordance with the rate-change message; and a device for adjusting the measured elapsed time to derive the internal delay.
  • elapsed time measurements may be obtained for each combination of a set of first and second transmission rates. Also, a plurality of elapsed times may be measured, and a selected one of the elapsed time measurements may be adjusted to derive the internal delay.
  • a method of determining an optimal time difference between frames of communication channels in a communication system having at least one base station and remote station and in which base stations control rates of transmission of remote stations includes the steps of: configuring a remote station for communication at a first transmission rate; providing a rate-change message to the remote terminal; measuring a time elapsed until the remote station's configuration has changed to a second transmission rate in accordance with the rate-change message; and adjusting the measured elapsed time to derive the optimal time difference.
  • the optimal time difference may be derived such that radio resources of the communication system are used maximally.
  • elapsed time measurements may be obtained for each combination of a set of first and second transmission rates.
  • a plurality of elapsed times may be measured, and a selected one of the elapsed time measurements may be adjusted to derive the optimal time difference.
  • FIG. 1 illustrates a hierarchical, or multi-layered, cellular communication system
  • FIG. 2 is a block diagram of a cellular mobile radiotelephone system
  • FIG. 3 illustrates pluralities of Layer 3 messages, Layer 2 frames, and Layer 1 time slots
  • FIG. 4 shows a general example of a channel configured as a succession of time slots 1, 2, . . . , i in each of a succession of frames 1, 2, . . ., j;
  • FIG. 5 illustrates a time relation between channels in a communication system
  • FIG. 6 is a flow chart of a method of determining a time difference between channels.
  • FIG. 5 illustrates a time relation between channels in a communication system.
  • a channel CHI comprises a succession of time slots 1, 2, . . ., i in each of a succession of frames 0, 1, 2, . . ., j sent on one carrier signal, and another channel CH2 is also configured as a later occurring succession of time slots 1, 2, . . . , i in each of a succession of frames 1, 2, . . ., j sent on a second carrier signal.
  • the channel CHI may be a forward (downlink) channel from a BS to a MS that includes messages transmitted by the transceivers 150, 160 shown in FIG. 2, and the channel CH2 may be a reverse (uplink) channel from the MS to the BS that includes messages transmitted by the transceiver 170 also shown in FIG. 2.
  • the time relation between the slot/frame structures of CHI and CH2 is determined when the MS sets up the uplink, i.e., the first time the MS begins to transmit on CH2. This time relation or time difference may be called T diff as shown in FIG. 5.
  • This time relation of the slot/frame structures of the BS and MS is due to the time needed for propagation of signals between the BS and MS as well as any time the MS processor 180 and transceiver 170 needs for preparing and transmitting each frame. Although illustrated in FIG. 5 as less than a frame length, it will be understood that the time difference may be greater than one frame length.
  • the length of a frame in some current communication systems is 20 msec and in others it is 10 msec, and some current remote stations need about 2.5 msec to prepare and transmit a frame.
  • the time difference may be in addition to or subsumed by an intentional delay that may be called for by the air interface protocol. It is not necessary for a communication system to use frame number or slot number synchronization, although some systems use a relative slot synchronization. This means that a slot sent by a MS is temporally related to a received slot from the BS by a certain value, but not that an uplink slot number k (where k - 0, 1, . . ., i- 1) must follow downlink slot number k.
  • Section 3.2.6.2 of the Specification for the Air-Interface for the 3G Mobile System, vol. 3 of the ARIB specification calls for delaying uplink transmissions by one- half of a time slot relative to downlink transmissions.
  • T diff in FIG. 5.
  • An arbitrary fixed value has been used in the past for the time relation between the frames of channels CHI, CH2.
  • a fixed value for T diff has not been chosen according to any specific rule, i.e., any value could be chosen regardless of the possible transmission rates on CHI and CH2. This time difference can cause a waste of communication system resources because the MS does not change its rate as fast as it can; this waste is eliminated by Applicant's invention.
  • the MS determines an optimal value of T diff instead of using a fixed value of T diff .
  • the determined value of T djff which may have been stored in a suitable memory like a register, RAM, EEPROM, etc., is fetched by the terminal's processing unit 180 when the terminal is setting up an uplink channel.
  • the optimal value of T diff can be determined for each permitted transmission rate either once, e.g., when the terminal is manufactured, or from time to time during the life of the mobile, e.g., when the terminal is powered up.
  • One way this can be done is by running a special test program in the terminal, a flow diagram of which is illustrated in FIG. 6.
  • the terminal is initially configured for communication at a first transmission rate (step 602), and then a simulated rate-change message either is generated internally by the terminal or is provided to the terminal by an external test equipment (step 604).
  • a timer that is either in the terminal or in the external test equipment measures the time elapsed until the terminal's configuration has changed to the commanded rate (step 606).
  • This procedure may be followed for each possible combination of beginning and ending transmission rates (step 608), and the procedure may be carried out more than once for each combination, with one (e.g., the largest) elapsed time measurement or an average of the measurements being retained for each combination (step 610).
  • the set can be used as the desired values of T diff or more preferably can first be adjusted by adding a safety margin, e.g., 10% of the respective measured elapsed time (step 612).
  • a safety margin e.g. 10% of the respective measured elapsed time
  • a special-purpose device e.g., a portion of an application specific integrated circuit (ASIC) could be used for determining T diff rather than the terminal's general-purpose processor.
  • the terminal could be configured to carry out the procedure of FIG. 6 while it is communicating with the network. It might be necessary to accumulate elapsed time values in a piecemeal fashion, rather than all at once for a whole rate set, and the first uplink channel and one or more subsequent uplinks might not be optimal because it or they would not be established based on measured elapsed times, but communication could be established more quickly by not having to wait for the execution of a special test routine.
  • T diff that is determined by the processing unit 180 is preferably "optimal" in that communication system resources are maximally utilized; this usually means that T difr is as small as possible.
  • the MS chooses T diff such that the MS can change its transmission rate as fast as possible, most preferably in the first frame or slot starting after a rate-change message has been received from the BS.
  • each remote station may have a respective value of T diff since the performance of the components of each remote station can be expected to differ slightly from the performance of components of other remote stations.
  • the value T diff may vary as a function of how the internal delay of the remote station relates to the set of possible transmission rates on the channel. Since the possible set of rates can vary widely in many communication systems, T diff can also vary for a single MS, depending on which rate set and which rate is used. It will be understood that rather than determining T diff for each possible transmission rate and in each remote station, it may be advantageous simply to select one or more fixed values that permit most remote stations to handle rate change as fast as possible.
  • transmitting messages in frames that begin at times based on the time relation T diff can be readily modified to transmitting messages in slots that begin at times based on the time relation T djff .

Abstract

La présente invention concerne un appareil et un procédé destinés à une station à distance pouvant faire partie d'un système de communications ayant au moins une station de base, et où les stations de base et la station mobile communiquent en échangeant des messages via leurs canaux respectifs organisés par trames, une station de base contrôlant la vitesse de transmission de la station à distance. Par ailleurs, pour sélectionner un intervalle de temps optimal entre les trames des canaux respectifs, un temps d'attente interne pour la station à distance est déterminé. Les messages en direction de la station de base sont transmis dans des trames qui débutent à des heures basées sur le temps d'attente interne. Les canaux peuvent être mis en oeuvre sur des signaux porteurs radiofréquence, l'intervalle de temps étant sélectionné de manière à ce que des ressources radio du système de communications soient utilisées à leur maximum.
PCT/SE1999/001269 1998-07-13 1999-07-13 Procede et appareil de determination des intervalles de temps optimaux entre les canaux de communications WO2000003500A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU53896/99A AU5389699A (en) 1998-07-13 1999-07-13 Method and apparatus for determining optimal time differences between communication channels

Applications Claiming Priority (2)

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US11433198A 1998-07-13 1998-07-13
US09/114,331 1998-07-13

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WO2000003500A1 true WO2000003500A1 (fr) 2000-01-20

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4937812A (en) * 1986-09-17 1990-06-26 Nec Corporation Subsidiary station capable of automatically adjusting an internal delay in response to a number signal received in a downward signal by the subsidiary station
WO1995012257A1 (fr) * 1993-10-27 1995-05-04 Motorola Inc. Appareil et procede d'adaptation d'un systeme radiotelephonique numerique a un trafic d'abonnes plus important
WO1997015131A2 (fr) * 1995-10-18 1997-04-24 Telefonaktiebolaget Lm Ericsson Procede d'amelioration de l'efficacite de la transmission dans des reseaux mobiles

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4937812A (en) * 1986-09-17 1990-06-26 Nec Corporation Subsidiary station capable of automatically adjusting an internal delay in response to a number signal received in a downward signal by the subsidiary station
WO1995012257A1 (fr) * 1993-10-27 1995-05-04 Motorola Inc. Appareil et procede d'adaptation d'un systeme radiotelephonique numerique a un trafic d'abonnes plus important
WO1997015131A2 (fr) * 1995-10-18 1997-04-24 Telefonaktiebolaget Lm Ericsson Procede d'amelioration de l'efficacite de la transmission dans des reseaux mobiles

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