EP1561361A1 - Method for controlling a handover - Google Patents

Method for controlling a handover

Info

Publication number
EP1561361A1
EP1561361A1 EP03810985A EP03810985A EP1561361A1 EP 1561361 A1 EP1561361 A1 EP 1561361A1 EP 03810985 A EP03810985 A EP 03810985A EP 03810985 A EP03810985 A EP 03810985A EP 1561361 A1 EP1561361 A1 EP 1561361A1
Authority
EP
European Patent Office
Prior art keywords
component
sgsn
sbsc
handover
message
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Withdrawn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
EP03810985A
Other languages
German (de)
French (fr)
Inventor
Christina Gessner
Toby Kier Proctor
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.)
Nokia Solutions and Networks GmbH and Co KG
Original Assignee
Siemens AG
Nokia Siemens Networks GmbH and Co KG
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 Siemens AG, Nokia Siemens Networks GmbH and Co KG filed Critical Siemens AG
Publication of EP1561361A1 publication Critical patent/EP1561361A1/en
Withdrawn legal-status Critical Current

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
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H04W28/06—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information

Definitions

  • the invention relates to a method for controlling a handover in radio communication systems.
  • radio communication systems signals are exchanged between radio terminals and base stations via a so called radio interface or air interface.
  • radio terminals are for example mobile or stationary user equipments (UE) .
  • base stations (NB - Node B) are access stations associ- ated with a land based communication network.
  • Examples of known radio communication systems are second generation digital mobile radio communication systems like GSM (Global System for Mobile Communication) based on TDMA (Time Division Multiple Access) and providing data rates up to 100 kbit/s, or third generation digital mobile radio communication systems like UMTS (Universal Mobile Telecommunication System) based on CDMA (Code Division Multiple Access) with data rates up to 2 Mbit/s.
  • GSM Global System for Mobile Communication
  • TDMA Time Division Multiple Access
  • CDMA Code Division Multiple Access
  • a context transfer or relocation between a source node and a target node should be employed. This relocation is inter alia mentioned in "Optimisation of SRNS relo- cation for real-time services" TSG-RAN WG #21, R2-011180, Bu- san, Korea, 21 st to 25 th May 2001, Agenda Item 9.2.3, Source Nokia.
  • Inter-RAT Radio Access Technologie
  • CS circuit switched domain services
  • Inter-RAT handover for PS (packet switched) domain services create additional problems for the transfer of an applied ROHC context in that the SGSN (Serving GPRS Support Node) and RNC (Radio Network Controller) do not possess a common protocol.
  • the SGSN Server GPRS Support Node
  • RNC Radio Network Controller
  • the hea- der compression is performed in the SNDCP in the SGSN
  • the header compression is performed in the PDCP (Packet Data Convergence Protocol) in the RNC.
  • PDCP Packet Data Convergence Protocol
  • An object of the invention is to provide a method for trans- ferring a protocol context during a handover procedure.
  • a first component transmits a handover request message to a second component.
  • the second component then transmits a message back to the first component, wherein the message contains information about a protocol context.
  • the first component transmits the handover request message inclu- ding the protocol context to the second component.
  • the inventive method makes an efficient use of existing message flows, thereby avoiding major changes to the systems ⁇ core network and RAN functionalities.
  • the invention is in ge- neral based on packet switched handover methods and message flows described in "Issues relating to PS Handover on an enhanced Gb", 3GPP GERAN Adhoc on A/Gb Evolution, Tdoc AHAGB- 006, Sweden, ll th -13 th June 2002, Source: Siemens.
  • the flow chart in the figure shows an example of a possible message exchange between various components of the radio com- munication system for a handover of a packet switched service.
  • the handover could for example be performed as a so called intrasyste handover within a GERAN based radio communication system, or as a so called intersystem handover from a GERAN based radio communication system to an UTRAN based radio communication system.
  • a similar flow chart could be defined for corresponding cell change procedures.
  • the SBSC Source Base Station Controller
  • MS Mobile Station
  • a message exchange procedure to handover the connection to respectively a TBSC (Target BSC) of the GERAN system or a RNC (Radio Network Controller) of an UTRAN system, in each case connected to a t-SGSN (Target-SGSN) .
  • the SBSC transmits a handover required message HO required to the s-SGSN (Source-SGSN) to which it is affiliated.
  • the s-SGSN replies to the received message by transmitting a HO reject message together with information related to the required ROHC context ROHC info.
  • This information is analysed in the SBSC and used to retransmit, in a third step (3) , the handover required message HO required to the s-SGSN, this time including the ROHC context ROHC info.
  • the s-SGSN subsequently forwards the handover request message HO required to the t-SGSN (tar- get-SGSN) of the target system, and the t-SGSN forwards it respectively to a TBSC (Target BSC) or to a RNC.
  • the TBSC or RNC then creates a new PDCP (Packet Data Convergence Protocol) for the handover, including the received new ROHC context ROHC info.
  • PDCP Packet Data Convergence Protocol
  • the described message flow is one in a variety of examples for an implementation of the method according to the invention, which, depending on the exact message flows to be deployed during a cell change or handover, could be modified accordingly.

Landscapes

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

Abstract

According to the inventive method for controlling a handover, a first component transmits a handover request message to a second component S-SGSN. The second component then transmits a message HO reject to the first component, wherein the message contains information relating to a protocol context ROHC. Finally, the first component retransmits the handover request message including the information relating to the protocol context to the second component.

Description

METHOD FOR CONTROLLING A HANDOVER
Field of the invention
The invention relates to a method for controlling a handover in radio communication systems.
Background of the invention
In radio communication systems, signals are exchanged between radio terminals and base stations via a so called radio interface or air interface. Such radio terminals are for example mobile or stationary user equipments (UE) . On the other side, base stations (NB - Node B) are access stations associ- ated with a land based communication network. Examples of known radio communication systems are second generation digital mobile radio communication systems like GSM (Global System for Mobile Communication) based on TDMA (Time Division Multiple Access) and providing data rates up to 100 kbit/s, or third generation digital mobile radio communication systems like UMTS (Universal Mobile Telecommunication System) based on CDMA (Code Division Multiple Access) with data rates up to 2 Mbit/s.
In such radio communication systems of the second and third generation, efficient header compression methods become increasingly important. Different methods are applicable and different protocol architectures are employed to make use of this feature. The so called robust header compression (ROHC) technique for an efficient transport of for example RTP (Real Time Protocol) /UDP (User Datagram Protocol) /IP packets over the radio interface is currently discussed for usage in SNDCP (Subnetwork Dependent Convergence Protocol) protocols of the enhanced Gb mode, i.e. in the context of GERAN (Global Evolution Radio Access Network - GSM/EDGE Radio Access Network) evolution towards the support of real time services. In this context, also requirements of such real time services, like for example streaming and conversational services with predefined time constraints, have to be taken into account. Any such header compression mechanism used therefore must also perform during for example handover or cell change.
In order to avoid a resource and time consuming re-initialisation of the header compression context following a handover or cell change, a context transfer or relocation between a source node and a target node should be employed. This relocation is inter alia mentioned in "Optimisation of SRNS relo- cation for real-time services" TSG-RAN WG #21, R2-011180, Bu- san, Korea, 21st to 25th May 2001, Agenda Item 9.2.3, Source Nokia.
The so called Inter-RAT (Radio Access Technologie) handover for CS (circuit switched) domain services is inter alia described in chapter 6.4.11 of the technical specification "In- terlayer procedures in Connected Mode" (Release 5) , 3GPP TS 25.303, V5.1.0 (2002-06) .
Inter-RAT handover for PS (packet switched) domain services create additional problems for the transfer of an applied ROHC context in that the SGSN (Serving GPRS Support Node) and RNC (Radio Network Controller) do not possess a common protocol. Specifically, in the GPRS protocol architecture the hea- der compression is performed in the SNDCP in the SGSN, whereas in the UTRAN protocol architecture the header compression is performed in the PDCP (Packet Data Convergence Protocol) in the RNC. Object' of the invention
An object of the invention is to provide a method for trans- ferring a protocol context during a handover procedure.
Statement of the invention
According to the inventive method for controlling a handover, a first component transmits a handover request message to a second component. The second component then transmits a message back to the first component, wherein the message contains information about a protocol context. Finally, the first component transmits the handover request message inclu- ding the protocol context to the second component.
The inventive method makes an efficient use of existing message flows, thereby avoiding major changes to the systems λ core network and RAN functionalities. The invention is in ge- neral based on packet switched handover methods and message flows described in "Issues relating to PS Handover on an enhanced Gb", 3GPP GERAN Adhoc on A/Gb Evolution, Tdoc AHAGB- 006, Stockholm, Sweden, llth-13th June 2002, Source: Siemens.
Brief description of the figures
The invention may be understood more readily, and various other aspects and features of the invention may become apparent from consideration of the following description and the figure as shown in the accompanying drawing sheet, wherein the figure shows a flow chart of a message exchange for handover. Detailed description of the invention
The flow chart in the figure shows an example of a possible message exchange between various components of the radio com- munication system for a handover of a packet switched service. The handover could for example be performed as a so called intrasyste handover within a GERAN based radio communication system, or as a so called intersystem handover from a GERAN based radio communication system to an UTRAN based radio communication system. A similar flow chart could be defined for corresponding cell change procedures.
In the given example, the SBSC (Source Base Station Controller) of the GERAN system, which has currently established a packet switched connection with a user equipment MS (Mobile Station) , initiates a message exchange procedure to handover the connection to respectively a TBSC (Target BSC) of the GERAN system or a RNC (Radio Network Controller) of an UTRAN system, in each case connected to a t-SGSN (Target-SGSN) .
In a first step (1), the SBSC transmits a handover required message HO required to the s-SGSN (Source-SGSN) to which it is affiliated. The s-SGSN then, in a second step (2), replies to the received message by transmitting a HO reject message together with information related to the required ROHC context ROHC info. This information is analysed in the SBSC and used to retransmit, in a third step (3) , the handover required message HO required to the s-SGSN, this time including the ROHC context ROHC info. The s-SGSN subsequently forwards the handover request message HO required to the t-SGSN (tar- get-SGSN) of the target system, and the t-SGSN forwards it respectively to a TBSC (Target BSC) or to a RNC. The TBSC or RNC then creates a new PDCP (Packet Data Convergence Protocol) for the handover, including the received new ROHC context ROHC info. Further exchanges of messages shown in the figure for executing and concluding the handover of the connection are well known from the art as aforesaid.
The described message flow is one in a variety of examples for an implementation of the method according to the invention, which, depending on the exact message flows to be deployed during a cell change or handover, could be modified accordingly.
The inventive method features inter alia the following advantages :
- An interworking of systems with different radio access technologies is ensured and header compression techniques are maintained in an efficient way;
- Additional header re-initialisation procedures in the target cell are avoided, thereby saving radio resources; - Well established message flows used for cell change or handover are reused;
- Only minor impacts on the core and radio network operation are required;
Transfer of the context remains transparent to the core network, which simplifies implementation of the procedure in the core network;
- No need to introduce new protocol entity (e.g. PDCP) for header compression in BSCs; and
- Method is easily applicable to other protocol contexts be- sides header compression.

Claims

Claims
1. Method for controlling a handover, wherein a first component (SBSC) transmits a handover request message (HO required) to a second component (s-SGSN), the second component (s-SGSN) transmits a message (HO reject) to the first component (SBSC) , wherein the message contains information relating to a protocol context (ROHC info) , and the first component (SBSC) retransmits the handover request message (HO required) including the information relating to the protocol context (ROHC info) to the second component (s- SGSN) .
2. Method according to claim 1, wherein the second component (s-SGSN) transmits a handover reject message (HO reject) to the first component (SBSC) .
3. Method according to claim 1 or 2, wherein the handover is executed for a packet switched service.
4. Method according to one of the previous claims, wherein the protocol context relates to a header compression.
5. Method according to one of the previous claims, wherein the first component (SBSC) and the second component (s-SGSN) relate to the same or different radio communication systems (GERAN, UTRAN) .
6. Radio communication system, comprising at least a first component (SBSC) with means for transmitting a handover request message (HO required) , and a second component (s-SGSN) with means for receiving the handover request message (HO required) from the first compo- nent (SBSC), and means for transmitting a message (HO reject) to the first component (SBSC) containing information relating to a protocol context (ROHC info) , wherein the first component (SBSC) comprises means for re- ceiving the message (HO reject) from the second component (s- SGSN) , and wherein the means for transmitting in the first component (SBSC) are used to retransmits the handover request message (HO required) to the second component (s-SGSN) including the received information relating to the protocol context (ROHC info) .
7. Component (SBSC) of a radio communication system, with means for transmitting a handover request message (HO required) to a second component (s-SGSN) , and, upon reception of a message (HO reject) from a second component (s-SGSN) containing information relating to a protocol context (ROHC info) using receiving means, for retransmitting the handover request message (HO required) to the second component (s- SGSN) including the received information relating to the pro- tocol context (ROHC info) .
EP03810985A 2002-11-13 2003-11-12 Method for controlling a handover Withdrawn EP1561361A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB0226453 2002-11-13
GBGB0226453.9A GB0226453D0 (en) 2002-11-13 2002-11-13 Method for controlling a handover
PCT/EP2003/012662 WO2004045234A1 (en) 2002-11-13 2003-11-12 Method for controlling a handover

Publications (1)

Publication Number Publication Date
EP1561361A1 true EP1561361A1 (en) 2005-08-10

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EP03810985A Withdrawn EP1561361A1 (en) 2002-11-13 2003-11-12 Method for controlling a handover

Country Status (5)

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EP (1) EP1561361A1 (en)
AU (1) AU2003301944A1 (en)
BR (1) BR0316199A (en)
GB (1) GB0226453D0 (en)
WO (1) WO2004045234A1 (en)

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Also Published As

Publication number Publication date
WO2004045234A1 (en) 2004-05-27
GB0226453D0 (en) 2002-12-18
AU2003301944A1 (en) 2004-06-03
BR0316199A (en) 2005-09-27

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