EP1042878A2 - Dispositif et procede de communication par canaux pour une station mobile dans un systeme de communication asynchrone a acces multiple par repartition de code - Google Patents

Dispositif et procede de communication par canaux pour une station mobile dans un systeme de communication asynchrone a acces multiple par repartition de code

Info

Publication number
EP1042878A2
EP1042878A2 EP99929935A EP99929935A EP1042878A2 EP 1042878 A2 EP1042878 A2 EP 1042878A2 EP 99929935 A EP99929935 A EP 99929935A EP 99929935 A EP99929935 A EP 99929935A EP 1042878 A2 EP1042878 A2 EP 1042878A2
Authority
EP
European Patent Office
Prior art keywords
common
code
short code
transmission signal
channel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99929935A
Other languages
German (de)
English (en)
Inventor
Soon Young Yoon
Ho Kyu Choi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Samsung Electronics Co Ltd
Original Assignee
Samsung Electronics Co Ltd
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 Samsung Electronics Co Ltd filed Critical Samsung Electronics Co Ltd
Publication of EP1042878A2 publication Critical patent/EP1042878A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0067—Rate matching
    • H04L1/0068—Rate matching by puncturing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/204—Multiple access
    • H04B7/216—Code division or spread-spectrum multiple access [CDMA, SSMA]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/10—Code generation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/04—Speed or phase control by synchronisation signals

Definitions

  • the present invention relates generally to an asynchronous CDMA communication system, and in particular, to a device and method for rapidly searching a base station using a common short code.
  • the respective base stations are time- synchronized to a global positioning system (GPS), and transmit the same spreading code with a unique offset value to enable mobile stations to distinguish the respective base stations.
  • GPS global positioning system
  • the base stations transmit spreading codes which are not synchronized to a GPS system.
  • the mobile stations prior to performing communication, the mobile stations should search for an optimal base station (i.e. cell), i.e., search for a spreading code whose receiving power level is highest so as to acquire code sync. Therefore, for an asynchronous mobile station, a cell search time is the sum of a spreading code search time and a code sync acquisition time.
  • the spreading code should be appropriately designed.
  • FIG. 1 illustrates a forward channel transmitter for a base station in a conventional asynchronous CDMA communication system, which is disclosed in a paper entitled “Fast Cell Search Algorithm in DS-CDMA Mobile Radio Using Long Spreading Codes", by K. Higuchi et al., IEEE.
  • the forward channel includes common channels applied (or assigned) in common to all the users belonging to a base station and dedicated channels uniquely assigned to the respective users.
  • the common channels include a pilot channel, a sync channel, a paging channel and a common control channel (CCH);
  • the dedicated channels include traffic channels (TCH) for transmitting voice and data.
  • Each channel transmitter uses a unique orthogonal code to distinguish its own channel from the channels of other channel transmitters.
  • a Walsh code is typically used for the orthogonal code.
  • each base station scrambles its channel transmission signal using a unique long spreading code (LSC) assigned to distinguish the base station.
  • LSC long spreading code
  • a common short code (CSC) is periodically inserted in a spreading code or an LSC after puncturing, so as to enable the mobile stations to rapidly search the base station.
  • the specific common channel is assumed to be a common control channel. Therefore, the CSC is periodically inserted after puncturing corresponding period in the common control channel which has been previously scrambled with the LSC, according to a mask control signal.
  • the CSC is shorter in length than the LSC and is commonly used for every base station.
  • every base station has the same puncturing (i.e.insertion) period.
  • a period of the LSC is multiples of a CSC period.
  • the mobile station searches a CSC transmitted from an optimal base station, i.e., a CSC received with the highest power using a CSC matching receiver, to detect an exact period thereof. Since the LSC period is multiples of the CSC period, the mobile station searches the LSC with the knowledge of the locations where the CSC is inserted therein. Therefore, in searching for an optimal base station having the highest signal strength, the mobile station can reduce the search time by searching for the inserted CSC on a specific pre-designated common channel.
  • FIG. 2 illustrates a common control channel transmitted from a base station
  • FIGs.3 A and 3B illustrate examples of the received common control channel signals using common CSC transmitted from multiple base stations (i.e. cells) A, B and C in an asynchronous system.
  • the received common control signals are shown over one LSC period. More specifically, FIG. 3 A illustrates a case where the received CSCs from multiple base stations are not aligned in time, and FIG. 3B illustrates a case where the received CSCs from multiple base stations are aligned in time.
  • FIG. 3B we omit the received common control channel signals from the base station C to emphasize the time alignment of CSCs from base stations A and B. It is the same situation if more than two received CSC signals from multiple base stations are aligned in time.
  • the received CSCs from multiple base stations are not aligned in time, so that the mobile station may have no difficulty in searching the strongest CSC.
  • Every base station inserts the same CSC in LSC scrambled common control channel signal using the same CSC insertion periods. Therefore, once the received CSCs from multiple base stations are aligned in time, the CSCs are repeatedly collide with each other, as illustrated in FIGs. 4A and 4B.
  • the mobile station has no difficulty in searching the strongest CSC power and CSC period.
  • receiving power during the period of CSC decreases due to phase offset, so that the mobile station may have difficulty in searching the strongest CSC and period.
  • the two time aligned CSCs have opposite phases, the received CSCs from two different base stations A and B offset each other, and finally disturbing the repetitive CSC search.
  • an object of the present invention to provide a device and method for preventing a common short code (CSC) inserted in a predesignated specific common channel spread with a long spreading code (LSC) from being repeatedly phase offset with the CSCs from other base stations.
  • CSC common short code
  • LSC long spreading code
  • the present invention being intended for use in an asynchronous CDMA communication system.
  • CSC modulated common short code
  • a communication device and associated method for rapid searching a base station using a common short code are provided.
  • the present invention is intended for use in an asynchronous CDMA communication system.
  • a pattern generator generates a modulation pattern unique to each base station for modulating a common short code
  • a long spreading code generator generates a long spreading code unique to each base station at predetermined periods.
  • the base station channel transmitter spreads a transmission signal on a specific common channel using the generated long spreading code.
  • a common short code generator generates a common short code used in common by multiple base stations.
  • a common short code inserter modulates the common short code with the modulation pattern unique to each base station and punctures the transmission signal on the common channel scrambled by the long spreading code at predetermined periods to insert the modulated common short code in the punctured transmission signal.
  • FIG. 1 is a diagram illustrating a forward channel transmitter for a base station in a conventional asynchronous CDMA communication system
  • FIG. 2 is a diagram illustrating a signal format of a common channel in a base station device having the channel structure of FIG. 1;
  • FIG. 3A is a diagram illustrating a case where the received common short codes inserted in common channel signals from multiple base stations are aligned in time;
  • FIG. 3B is a diagram illustrating a case where the received common short codes inserted in common channel signals from multiple base stations are are not aligned in time
  • FIG. 4 A is a diagram illustrating a case where the received common short codes inserted in common channel signals from multiple base stations are both aligned in time and in phase;
  • FIG. 4B is a diagram illustrating a case where the received common short codes inserted in common channel signals from multiple base stations are aligned in time but out of phase;
  • FIG. 5 is a diagram illustrating a channel transmission device for a base station in an asynchronous CDMA communication system according to an embodiment of the present invention
  • FIG. 6 is a diagram illustrating the operation of puncturing a common channel signal and inserting a common short code in the punctured common channel signal in a communication device for a base station of FIG. 5;
  • FIG. 7 is a diagram illustrating common channel signals which are punctured to insert therein common short codes modulated according to unique modulation patterns in base station communication devices according to an embodiment of the present invention.
  • FIG. 8 is a diagram illustrating how to prevent repeated phase offset of the received common short codes when the common short codes inserted in common channels of different base stations are aligned in time with each other according to an embodiment of the present invention.
  • multiple base stations using a common carrier frequency puncture a specific predesignated common channel scrambled by the long spreading code designated for a forward link at predetermined periods to insert therein common short codes modulated according to a specific modulation pattern unique to each base station.
  • the unique modulation applied to the respective common short codes the received common short codes at the mobile station are prevented from offsetting each other caused by phase shifts which may occur in the communication channel during the base station search procedure.
  • the respective base stations insert the common short codes (CSCs) in the common control channel scrambled by the long spreading codes (LSCs) at the same periods after puncturing, to reduce a base station (i.e. cell) search time at the mobile station.
  • the common short codes CSCs are modified by a specific pattern unique to each base station prior to their insertion into the punctured common control channel. Therefore, when the received CSCs from multiple base stations become completely aligned with one another, repeated phase offset of the common short codes can be prevented by virtue of the unique modifications applied to the CSCs.
  • FIG. 5 illustrates a forward channel transmitter for a base station according to an embodiment of the present invention, wherein the forward channel transmitter includes a modulation pattern generator, a specific common channel and traffic channels.
  • the specific common channel is a common control channel (CCH) and a Walsh code is used for an orthogonal code.
  • CCH common control channel
  • Walsh code is used for an orthogonal code.
  • a multiplier 511 multiplies a transmission signal on a common control channel by a Walsh code assigned to the common control channel in order that the common control channel becomes orthogonal with respect to other traffic channels.
  • An LSC generator 513 generates a long spreading code (LSC) having a period N LSC for discrimination of the base station.
  • a multiplier 515 multiplies the output from the multiplier 511 by the LSC generator output.
  • a CSC generator 517 generates a common short code (CSC) which will be inserted in the transmission signal on the common control channel scrambled by the long spreading code, at the periods of N csc after puncturing.
  • CSC common short code
  • a modulation pattern generator 519 stores a modulation pattern unique to each base station to prevent repeated offset of the CSCs from multiple base stations at the mobile station receiver.
  • the modulation pattern generator 519 is enabled at predetermined periods to output the modulation pattern, under the control of a puncture controller 525.
  • a multiplier 521 multiplies the CSC output from the CSC generator 517 by the modulation pattern output from the modulation pattern generator 519.
  • a puncturer 523 receiving outputs of the multipliers 515 and 521, punctures the transmission signal on the common control channel to insert therein the modulated CSC output from the multiplier 521 in response to a puncturing control signal output from the puncture controller 525.
  • the puncture controller 525 generates the puncturing control signal for puncturing the common control channel at predetermined periods to insert the CSC in the punctured common control channel.
  • Multipliers 551-55N multiply transmission signals on the corresponding traffic channels by associated Walsh codes assigned to the traffic channels in order that the common control channel becomes orthogonal with respect to other traffic channels.
  • Multipliers 561-56N multiply outputs of the corresponding multipliers 551 -55N by the LSC output from the LSC generator 513 to spread the transmission signals on the corresponding traffic channels.
  • An adder 571 adds the spread transmission signals on the respective traffic channels, output from the multipliers 561-56N.
  • An adder 573 adds the added transmission signal output from the adder 571 to the CSC-inserted transmission signal on the common control channel and transmits the output signal.
  • FIG. 6 illustrates a procedure for puncturing the common control channel of FIG. 5 to insert the modulated CSC in the punctured common control channel.
  • the LSC having a period N LSC on the common control channel signal is punctured and the CSC having a period N csc is inserted in the punctured common control channel signal.
  • a gap between the CSCs is N p *N rsr chips.
  • the puncture controller 525 simultaneously enables the modulation pattern generator 519 and the puncturer 523 , so that the common control channel is punctured and the modulated CSC output from the multiplier 521 is inserted in the punctured common control channel.
  • the transmission signals on the common control channel CCH and the traffic channels TCH are orthogonally spread with the corresponding Walsh codes, for channel separation, and the orthogonally spread channel signals are multiplied by the LSC output from the LSC generator 513, for scrambling.
  • the transmission signal on the common control channel CCH is provided to the puncturer 523.
  • Every base station includes an identical CSC generator 517 for generating the CSC to be inserted in the punctured LSC, and the modulation pattern generator 519 for generating a unique modulation pattern comprised of "+1 " and "-1 ".
  • the modulation pattern is multiplied by the CSC under the control of the puncturer controller 525.
  • the puncturer 523 is activated at each N csc insertion period for an output duration equal to the length of the CSC code.
  • the CSC is multiplied by a unique modulation pattern assigned to the base station prior to inserting the CSC under the control of the puncturer controller 525.
  • the modulated C SC is inserted in the punctured transmission signal on the common control channel CCH which is input to the puncturer 523.
  • Table 1 shows unique modulation patterns assigned to the base stations A, B and C, by way of example.
  • FIG. 7 illustrates the common control channels in which the CSCs are inserted according to the modulation patterns of Table 1.
  • the mobile station receiver should have the modulation patterns of all the base stations as well as the long spreading code. Therefore, by modulating the CSCs using the modulation patterns of Table 1 , it is possible to prevent repeated phase offset even though the CSCs output over the common control channels of the base stations are aligned in time with one another.
  • FIG. 8 illustrates a state where the received CSCs on the common control channels of the two base stations A and B are aligned with each other.
  • the dotted portions represent a state where the received CSCs of the cells A and B are in phase as well as aligned in time
  • the plain portions represent a state where the received CSCs of the cells A and B are aligned in tiem but in opposite phase.
  • FIG. 8 shows a case where the modulation pattern has a period of 5 chips, for simplicity. That is, it is assumed that 5 CSC chips are inserted in the punctured LSC spread to common control channel signal at every LSC period. Further, FIG. 8 does not illustrate the non-punctured common control channel signal, for simplicity.
  • FIG. 8 shows a case where the modulation pattern has a period of 5 chips, for simplicity. That is, it is assumed that 5 CSC chips are inserted in the punctured LSC spread to common control channel signal at every LSC period. Further, FIG. 8 does not illustrate the non-puncture
  • the cell A uses a modulation pattern (+1 +1 -1 -1 +1) and the cell B uses a modulation pattern (-1 +1 -1 +1 +1).
  • reference numeral 812 denotes a common control channel of the cell A, in which the CSCs are inserted after puncturing.
  • Reference numerals 822-830 denote all the possible relative locations where the CSCs for the common control channel of the cell B can locate with respect to the CSCs for the common control channel of the cell A.
  • the dotted portions in the common channel signal of the cell B represent the portions where the common channel signals are aligned in time and in phase with the common channel signals of the cell A, in the case where the phase shift does not occur during transmission
  • the non-dotted portions represent the case where the CSCs of the cells A and B are in the opposite phase while they are aligned in time.
  • the CSCs are offset at the portions having the opposite phase.
  • the offset does not occur repeatedly. That is, due to the unique modulation applied to each CSC codes, consecutive comparisons of CSC codes from different base stations will result in phase offset occurring in some instances and not occurring in others. Therefore, it is possible to search code sync for the LSC based on the fact that the LSC always starts at the same position with the CSC.
  • the common control channel signal of one of two base stations is phase-shifted by 180 degree due to the phase shift during transmission, the dotted portions become same phase so that it is still possible to search the code sync. Therefore, it is possible to prevent a case where the CSCs are not detected repeatedly due to the phase difference no matter whether or not the phase shift occurs during transmission.
  • a base station transmission device punctures a specific common channel spread by the LSC to insert therein a common short code before transmission, and the mobile stations then search the base station using the common short code punctured in the transmission signal received over the specific common channel.
  • the specific common channel transmission device for the base station inserts the CSCs using the unique modulation pattern, so that it is possible to prevent repeated phase offset of the CSCs even though the CSCs of the base stations are aligned in time with each other due to the phase shift during transmission. In this manner, the mobile station can rapidly search the base station to acquire code sync.

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

Abstract

Dispositif de communication pour une station de base dans un système de communication asynchrone à accès multiple par répartition de code. Un générateur de code court commun produit un code court commun utilisé en commun par des stations de base multiples, un générateur de modèle produit un modèle de modulation unique et un générateur de code d'étalement long produit un code d'étalement long unique à des périodes prédéterminées. Un émetteur de canal spécifique étale un signal de transmission sur un canal commun spécifique à l'aide du code d'étalement long. Un introducteur de code court commun module le code court commun à l'aide du modèle de modulation, interrompt le signal de transmission sur le canal commun à des périodes prédéterminées et introduit le code commun court modulé dans le signal de transmission discontinu.
EP99929935A 1998-07-11 1999-07-12 Dispositif et procede de communication par canaux pour une station mobile dans un systeme de communication asynchrone a acces multiple par repartition de code Withdrawn EP1042878A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
KR9828060 1998-07-11
KR1019980028060A KR100273644B1 (ko) 1998-07-11 1998-07-11 비동기 방식의 부호분할다중접속 통신시스템의 기지국 채널통신장치 및 방법
PCT/KR1999/000371 WO2000003549A2 (fr) 1998-07-11 1999-07-12 Dispositif et procede de communication par canaux pour une station mobile dans un systeme de communication asynchrone a acces multiple par repartition de code

Publications (1)

Publication Number Publication Date
EP1042878A2 true EP1042878A2 (fr) 2000-10-11

Family

ID=19543900

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Application Number Title Priority Date Filing Date
EP99929935A Withdrawn EP1042878A2 (fr) 1998-07-11 1999-07-12 Dispositif et procede de communication par canaux pour une station mobile dans un systeme de communication asynchrone a acces multiple par repartition de code

Country Status (7)

Country Link
EP (1) EP1042878A2 (fr)
KR (1) KR100273644B1 (fr)
CN (1) CN1273723A (fr)
AU (1) AU4656799A (fr)
BR (1) BR9906593A (fr)
RU (1) RU2189704C2 (fr)
WO (1) WO2000003549A2 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3439399B2 (ja) * 1999-10-14 2003-08-25 エヌイーシーマイクロシステム株式会社 Ｃｄｍａベースバンド受信装置

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3376224B2 (ja) * 1996-10-23 2003-02-10 株式会社エヌ・ティ・ティ・ドコモ Ｄｓ−ｃｄｍａ基地局間非同期セルラ方式における初期同期方法および受信機
JP3373746B2 (ja) * 1997-01-07 2003-02-04 株式会社鷹山 Ｄｓ−ｃｄｍａ基地局間非同期セルラ方式における初期同期方法および受信機

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0003549A2 *

Also Published As

Publication number Publication date
WO2000003549A3 (fr) 2000-03-30
RU2189704C2 (ru) 2002-09-20
KR20000008309A (ko) 2000-02-07
AU4656799A (en) 2000-02-01
KR100273644B1 (ko) 2000-12-15
WO2000003549A2 (fr) 2000-01-20
BR9906593A (pt) 2000-11-21
CN1273723A (zh) 2000-11-15

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