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WO1998008353A2 - Systeme de radiocommunication cellulaire et procede d'execution de transfert - Google Patents

Systeme de radiocommunication cellulaire et procede d'execution de transfert Download PDF

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Publication number
WO1998008353A2
WO1998008353A2 PCT/FI1997/000488 FI9700488W WO9808353A2 WO 1998008353 A2 WO1998008353 A2 WO 1998008353A2 FI 9700488 W FI9700488 W FI 9700488W WO 9808353 A2 WO9808353 A2 WO 9808353A2
Authority
WO
WIPO (PCT)
Prior art keywords
bsc
base station
terminal equipment
bscs
msc
Prior art date
Application number
PCT/FI1997/000488
Other languages
English (en)
Other versions
WO1998008353A3 (fr
Inventor
Petri Hokkanen
Original Assignee
Nokia Telecommunications Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nokia Telecommunications Oy filed Critical Nokia Telecommunications Oy
Priority to AU39440/97A priority Critical patent/AU3944097A/en
Publication of WO1998008353A2 publication Critical patent/WO1998008353A2/fr
Publication of WO1998008353A3 publication Critical patent/WO1998008353A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/12—Reselecting a serving backbone network switching or routing node
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/16—Performing reselection for specific purposes
    • H04W36/18—Performing reselection for specific purposes for allowing seamless reselection, e.g. soft reselection

Definitions

  • the present invention relates to cellular radio systems employing code division multiple access and comprising at least one base station in each cell, and a group of base station controllers (BSC) to each of which is coupled at least one base station, the BSC and the base stations coupled thereto constituting a base station system (BSS) , and the BSCs controlling the use of radio resources of the base stations coupled to them.
  • BSS base station system
  • the invention particularly aims at a new method for carrying out a handoff of a subscriber terminal equipment between two different BSSs .
  • a CDMA (Code Division Multiple Access) system is a multiple access method which is based on spread spectrum technology and whose application in cellular radio systems has lately been initiated along with the earlier FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access) technologies.
  • the CDMA technology has several advantages over the earlier methods, such as spectral efficiency and simple frequency planning.
  • the narrow-band data signal of the user is multiplied by a spreading code of much wider bandwidth to a relatively wide band.
  • the bandwidths used include, for example, 1.25 MHz, 10 MHz and 25 MHz.
  • the data signal spreads to the whole band used. All users transmit simultaneously by using the same frequency band.
  • a separate spreading code is employed for each connection between a base station and a mobile station, and the signals from the users can be identified from one another in the receivers on the basis of the spreading code of each connection.
  • Matched filters or correlators in the receivers are synchronized with the desired signal, which is identified on the basis of the spreading code.
  • the data signal is returned in the receiver onto the original band by multiplying it by the same spreading code as in the transmission phase.
  • the signals which have been multiplied by some other spreading code neither correlate nor return to the narrow band in an ideal case. They thus appear as noise from the point of view of the desired signal.
  • An attempt is made for choosing the spreading codes so that they are mutually orthogonal, i.e. they do not correlate with each other.
  • signals between a base station and a mobile station travel by several different paths between the transmitter and the receiver. This multipath propagation is mainly caused by signals reflecting from the surrounding surfaces. Signals that have travelled through different paths arrive at the receiver at different times due to different delays in the propagation time.
  • the spreading codes are not orthogonal with all the delay values . Therefore, signals delayed in different ways cause interference in signal detection.
  • the interference caused by the users to one another is referred to as multiple access interference.
  • a base station transmits to all the mobile stations within its service area by using the same frequency band.
  • the same frequency band is typically in use in adjacent cells as well.
  • the aim is to choose the spreading codes employed by a base station to be mutually orthogonal.
  • the pilot channel is a data unmodulated signal which thus contains no data information and which is transmitted with a specific spreading code.
  • the pilot channel is transmitted by using the same frequency band which contains the actual traffic channels, from which the pilot channel can only be identified on the basis of the spreading code.
  • a pilot channel is used, for example, in power measurements and in generating a coherent phase reference.
  • a base station can also supply the mobile stations in its area with information on the spreading codes employed on the pilot channels of the base stations in the neighboring cells. As a result, the stations are able to recognize transmissions from the neighboring cells. This information may be utilized in carrying out a handoff .
  • the signal from the neighboring cell base station on the same frequency range with the current serving base station begins to appear as ever increasing interference at the receiver of the mobile station.
  • This interference is especially harmful because the spreading codes being employed at the neighboring cells are not necessarily completely orthogonal to the codes in the current cell.
  • the power control of the neighboring cell base station if such a power control is in use, does not take adjacent cells into consideration.
  • the connections tolerate interference to a certain degree.
  • the aim is to keep overlapping of adjacent cells to a minimum.
  • the term overlapping here refers to a simultaneous coverage of the same area by transmission from more than one base station.
  • Hard handoff refers to a handoff in which the existing connection is disconnected before establishing a new one. It is thus a 'break before make' type of a handoff.
  • a so-called soft handoff has been developed in which the terminal equipment for some time communicates with more than one base station simultaneously. A new connection to an adjacent base station is established before breaking the connection to the old one, i.e. it is thus a 'make before break' handoff. In this manner, the reliability of handoffs can be improved . If a soft handoff between cells is not possible, as is the case e.g. between base stations of different BSCs, the overlapping area between them must be larger than in case a soft handoff were possible. This causes more interference in both cells, which in turn reduces the capacity of the cells.
  • Figures la-Id illustrate the phases of the prior art method.
  • the figures show a diagram of an MSC 100, a first BSS 102, a second BSS 104, and a terminal equipment 106.
  • the terminal equipment 106 When approaching the border of the first and second BSC, the terminal equipment 106 has carried out, in a situation of Figure la, a soft handoff with base stations of different BSCs 102, 104, thus having a simultaneous connection 108, 110 to different BSSs.
  • the signal from the second BSC 112 must be applied via 114 the MSC 100 to the first BSC in which the combining takes place and from which the coded signal is applied 116 to the MSC 100.
  • the direct connection 108 is released even though the coding still takes place in the first BSS 102.
  • the transcoding is transferred to take place in the second BSS 104.
  • the connection to the first BSS 102 is disconnected.
  • a cellular radio system employing code division multiple access, and comprising at least one base station in each cell, and a group of base station controllers to each of which is coupled at least one base station, the BSC and the base stations coupled thereto constituting a BSS, and the BSCs controlling the use of radio resources of the base stations coupled to them, and in the system the base stations located at the border of two or more BSSs being coupled to at least two BSCs which control said base station.
  • the invention in addition relates to a method for performing a handoff in a cellular radio system comprising at least one base station in each cell, and a group of BSCs and an MSC coupled to them, and in which at least one base station is coupled to each BSC, the BSC and the base stations coupled thereto constituting a BSS, and the BSCs controlling the use of radio resources of the base stations coupled to them, the method comprising the steps of the first BSC transmitting a message on a handoff need by the terminal equipment to the MSC as the subscriber terminal equipment communicates with a base station which is at the border of the first and second BSS, and the control of the radio resources of which takes place from both the first and second BSC when the terminal equipment moves controlled by the first BSC and using its resources from the direction of the first BSC towards the second BSC, the message containing a description on the radio channel of the terminal equipment; the MSC transmitting information to the second BSC on the handoff request received, the information containing a description on the radio channel of the terminal equipment
  • the method according to the invention provides several advantages.
  • it is possible to avoid a conventional hard handoff, resulting in a better reliability of the connection particularly at the border of two BSSs.
  • the prior art drawbacks such as loading the MSC, can be avoided. Description of the Drawings
  • Figure 1 shows an example of the prior art method described above
  • Figure 2 illustrates the structure of the cellular radio system according to the invention
  • FIG. 3 illustrates the structure of the base station controller and base station according to the preferred embodiment of the invention
  • Figure 4 illustrates the structure of the base station controller and base station according to a second preferred embodiment of the invention.
  • a typical cellular radio systems consists of a plurality of base stations, whose service areas are referred to as cells, and base station controllers.
  • the base stations communicate with subscriber terminal equipments over the radio path, are responsible for channel coding, and comprise the required logic for managing these functions, including conveying of information from the terminal equipments to outside the network and vice versa.
  • the base station controllers control the functions and radio resources of the base stations. If a terminal equipment communicates with more than one base station simultaneously, as is the case in a soft handoff, the base station controllers also combine signals received by several different base stations .
  • an example will be examined of the structure of the cellular radio system according to the invention by means of the chart in Figure 2.
  • the figure shows two BSCs 200, 202 of the cellular radio system, and a group of base stations 204-218.
  • Base stations 204-212 are connected to the first BSC by means of transmission lines 220-230. Further, there is a connection from the BSC to the rest of the network by means of transmission line 242.
  • the area of the first BSC comprises the BSS covered by base stations 204-212.
  • base stations 214-218 are connected to the second BSC. Further, there is a connection from the BSC to the rest of the network by means of transmission line 244.
  • the base stations at the border of the BSSs i.e. base stations 208-212
  • the area of the second BSC correspondingly comprises the BSS covered by base stations 208-218.
  • the resources of base stations 208-212 at the border of the BSSs are shared between both the BSCs.
  • the shared base station only comprises one set of radio frequency parts, as does a normal base station, and from the point of view of cellular planning and the terminal equipment it constitutes just a single cell.
  • a terminal equipment located in the service area of such a shared base station 208-212 may be controlled by either BSC.
  • the figure shows two BSCs 200, 202 and a base station 210 at the border of the BSSs.
  • the base station is provided with an antenna 312 which it uses for transmitting and receiving signals from the terminal equipments, a combiner 308 which is coupled to the antenna and which combines different signals with one another, a group of carrier wave units 306a-306b which transfer the signal to be transmitted onto a carrier frequency, and other required radio frequency parts, and corresponding functions for the receiving direction.
  • the base station further comprises a group of channel units 304a-304d which carry out channel coding and decoding, i.e.
  • the base station naturally contains other components as well, such as filters and amplifiers, which is obvious for a person skilled in the art, but as they are not essential to the present invention, they are not shown in the figure.
  • the base station further comprises a control means 310 which controls the operation of the various parts of the base station, and communicates with the BSCs.
  • the base station in addition comprises a prior art transmission line means 302, which transfers the signal between channel units 304a-304d and BSCs 200, 202 by using transmission lines 228, 234.
  • the BSCs 200, 202 comprise transmission line units 314, 320 which receive a signal from the base stations communicating with the BSC by using transmission lines 228, 234, and forward it to transcoding units 318a-318d, 324a-324d, where the frames are combined and the required transcoding is carried out. From the transcoders, the signal is applied further to the other parts of the network, e.g. to the MSC 300, by means of transmission lines 242, 244.
  • the BSCs further comprise a control processor 316, 322 which controls the operation of the various parts of the BSC, and communicates with the base stations controlled by the BSC.
  • the network i.e. BSC 200 in this case, detects that there exists a need for a handoff between BSCs. For this purpose, BSC 200 transmits from its control means 316 a command to terminal equipment 246 to disconnect the connection to base station 206. This information is also conveyed via the MSC to base station 206. BSC 200 transmits information to MSC 300 on the handoff need by terminal equipment 246. This message contains description on the radio channel of the terminal equipment, i.e. information on the base station, the frequency used and the spreading code of the connection.
  • MSC 300 transmits information to the second BSC 202 on the handoff request received, the information containing description on the radio channel of the terminal equipment with the aforementioned details .
  • the second BSC 202 allocates radio resources for the connection of terminal equipment 246, and controls base station 210 to establish a transmission line connection between the second BSC 202 and base station 210 for the connection of terminal equipment 246 on transmission lines 234.
  • the radio resources comprise one of the transcoders 324a-324d and capacity from the transmission line means 320.
  • control processor 322 of BSC 202 transmits information thereof to MSC 300.
  • MSC 300 transfers terminal equipment 246 to under the control and resources of the second BSC 202, and transmits a message to the first BSC 200 to release its radio resources, i.e. for example the transcoder, related to the connection of the terminal equipment.
  • the connection allocated for the signal of terminal equipment 246 on transmission lines 228 between base station 210 and BSC 200 is also released.
  • terminal equipment 246 is now controlled by BSC 202, and it may, if need be, establish a connection to other base stations that are controlled by BSC 202, e.g. base station 214.
  • BSC 202 base station
  • FIG. 4 The figure shows two BSCs 200,
  • the internal structure of the base station and the BSCs disclosed is largely similar to what was described in
  • the base station is provided with an antenna
  • the base station further comprises a group of channel units 304a-304d which carry out channel coding and decoding, i.e. the required changes between the radio path and the signal to be transmitted to the BSC.
  • channel coding and decoding i.e. the required changes between the radio path and the signal to be transmitted to the BSC.
  • the base station 210 further comprises control means 310 which controls the operation of the various parts of the base station 210, and communicate with the BSCs 200, 202.
  • the base station in addition comprises a transmission line means 302, which transfer the signal between channel units 304a-304d and BSCs 200, 202 by using transmission lines 400, 404.
  • the transmission line means 302 can be implemented by prior art methods.
  • the BSCs 200, 202 comprise transmission line units 314, 320 which receive a signal from the base stations communicating with the BSC by using transmission lines 400, 404, and forward it to transcoding units 318a-318d, 324a-324d, where the frames are combined and the required transcoding is carried out.
  • the signal is applied further to the other parts of the network, e.g. to the MSC 300, by means of the transmission lines 242, 244.
  • the BSCs further comprise a control processor 316, 322 which controls the operation of the various parts of the BSC, and communicates with the base stations controlled by the BSC.
  • the above parts and connections between them can be implemented by methods known by a person skilled in the art.
  • the BSCs further communicate with one another by means of transmission line 402 connected to transmission line units 314, 320.
  • the BSCs may also communicate with other BSCs than those shown in the figure .
  • BSC 200 detects that there exists need for a handoff between BSCs. For this purpose, BSC 200 transmits from its control means 316 a command to terminal equipment 246 to disconnect the connection to base station 206. This information is also conveyed via the MSC to base station 206.
  • BSC 200 transmits information from its control processor 316 to MSC 300 on the handoff need by terminal equipment 246.
  • This message contains description on the radio channel of the terminal equipment, i.e. information on the base station, the frequency used and the spreading code of the connection, and also on the transmission line 402 between BSCs 200 and 202.
  • MSC 300 transmits information to the second control processor 322 of BSC 202 on the handoff request received, the information containing description on the radio channel of the terminal equipment with the aforementioned details, and information on the transmission line 402.
  • BSC 202 Having received the message from the MSC, BSC 202 allocates radio resources for the connection by terminal equipment 246.
  • the radio resources comprise one of the transcoders 324a-324d and capacity from the transmission line means 320.
  • BSC 202 receives a signal from terminal equipment 246 via BSC 200 on transmission line 402.
  • BSC 202 establishes a connection 404 directly to base station 210, and transfers the resources of transmission line 402 onto transmission line 404 connected to the base station, consequently releasing transmission line connection 402 to BSC 200.
  • control processor 322 of BSC 202 transmits a message thereof to MSC 300.
  • MSC 300 Having received the aforementioned message from BSC 202, MSC 300 transfers the terminal equipment to be controlled by BSC 202, and transmits a message to control processor 316 of BSC 200 to release the radio resources employed by the connection of terminal equipment 246.

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

Abstract

L'invention concerne un procédé d'exécution d'un transfert ainsi qu'un système de radiocommunication cellulaire employant l'accès multiple par différence de codes et comprenant au moins une station de base dans chaque cellule, ainsi qu'un groupe de contrôleurs de stations de base (BSC) à chacun desquels est couplée au moins une station de base. Le BSC et les stations de base qui lui sont couplées constituent un système de stations de base (BSS). Les BSC gèrent l'utilisation des ressources de radiocommunication des stations de base qui leur sont couplées. Afin de faciliter un transfert, les stations de base situées à la frontière d'au moins deux BSS sont connectées à au moins deux BSC qui gèrent la station de base.
PCT/FI1997/000488 1996-08-23 1997-08-22 Systeme de radiocommunication cellulaire et procede d'execution de transfert WO1998008353A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU39440/97A AU3944097A (en) 1996-08-23 1997-08-22 Cellular radio system and a method for performing handoff

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US70185196A 1996-08-23 1996-08-23
US08/701,851 1996-08-23

Publications (2)

Publication Number Publication Date
WO1998008353A2 true WO1998008353A2 (fr) 1998-02-26
WO1998008353A3 WO1998008353A3 (fr) 1998-04-30

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PCT/FI1997/000488 WO1998008353A2 (fr) 1996-08-23 1997-08-22 Systeme de radiocommunication cellulaire et procede d'execution de transfert

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AU (1) AU3944097A (fr)
WO (1) WO1998008353A2 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000054531A1 (fr) * 1999-03-05 2000-09-14 Siemens Aktiengesellschaft Procede de partage des ressources dans un systeme de radiotelecommunication
WO2001086988A1 (fr) * 2000-05-11 2001-11-15 Telefonaktiebolaget Lm Ericsson (Publ) Procede de re-radioralliement et de partage des ressources dans des reseaux cellulaires de communications
WO2004015959A3 (fr) * 2002-08-08 2004-04-01 Tait Electronics Ltd Ameliorations concernant des systemes de communication radio
WO2005115026A3 (fr) * 2004-05-18 2007-01-04 Airvana Inc Commande de reseau radioelectrique
US7170871B2 (en) * 2001-06-25 2007-01-30 Airvana, Inc. Radio network control
CN101015224B (zh) * 2004-05-18 2012-05-30 爱尔瓦纳股份有限公司 无线网络控制

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8843638B2 (en) 2007-12-13 2014-09-23 Ericsson Evdo Inc. Handing off active connections

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5499386A (en) * 1993-07-09 1996-03-12 Telefonaktiebolaget L M Ericsson Best server selection in layered cellular radio system
US5432843A (en) * 1993-08-02 1995-07-11 Motorola Inc. Method of performing handoff in a cellular communication system
ATE200378T1 (de) * 1994-01-27 2001-04-15 Nokia Networks Oy Semi-abrupte verbindungsübergabe in einem zellularen telekommunikationssystem
CN1235436C (zh) * 1994-05-20 2006-01-04 Ntt移动通信网株式会社 移动通信方法和使用可靠性信息的基站侧子系统装置
FI98976C (fi) * 1994-07-11 1997-09-10 Nokia Telecommunications Oy Menetelmä kanavanvaihdon suorittamiseksi ja solukkoradiojärjestelmä

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000054531A1 (fr) * 1999-03-05 2000-09-14 Siemens Aktiengesellschaft Procede de partage des ressources dans un systeme de radiotelecommunication
DE19909779A1 (de) * 1999-03-05 2000-09-14 Siemens Ag Verfahren zur Ressourcenzuteilung in einem Funk-Kommunikationssytem
WO2001086988A1 (fr) * 2000-05-11 2001-11-15 Telefonaktiebolaget Lm Ericsson (Publ) Procede de re-radioralliement et de partage des ressources dans des reseaux cellulaires de communications
US6738625B1 (en) 2000-05-11 2004-05-18 Telefonaktiebolaget Lm Ericsson (Publ) Rehoming and resource sharing in communications networks
US7170871B2 (en) * 2001-06-25 2007-01-30 Airvana, Inc. Radio network control
US8160020B2 (en) * 2001-06-25 2012-04-17 Airvana Network Solutions, Inc. Radio network control
WO2004015959A3 (fr) * 2002-08-08 2004-04-01 Tait Electronics Ltd Ameliorations concernant des systemes de communication radio
WO2005115026A3 (fr) * 2004-05-18 2007-01-04 Airvana Inc Commande de reseau radioelectrique
JP2007538476A (ja) * 2004-05-18 2007-12-27 エアヴァナ，インコーポレーテッド 無線ネットワーク・コントロール
CN101015224B (zh) * 2004-05-18 2012-05-30 爱尔瓦纳股份有限公司 无线网络控制

Also Published As

Publication number Publication date
AU3944097A (en) 1998-03-06
WO1998008353A3 (fr) 1998-04-30

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