Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2002-09-10
2003-11-04
Vo, Nguyen T. (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C455S437000, C380S247000
Reexamination Certificate
active
06643513
ABSTRACT:
TECHNICAL FIELD
These teachings relate generally to wireless communications systems and methods and, more specifically, relate to cellular wireless communications systems and to techniques for a mobile station (MS), also referred to herein as user equipment (UE), to transition from one cell to another.
BACKGROUND
The following abbreviations are herewith defined, at least some of which are referred to in the ensuing description of the prior art and the preferred embodiments.
3GPP
Third Generation Partnership Project
BSC
Base Station Controller
BSS
Base Station System
BTS
Base Transceiver Station
CN
Core Network
CRS
Cell Re-Selection
CS
Cellular System
DL
Down Link (to the MS)
EDGE
Enhanced Data rate for Global Evolution
EGPRS
Enhanced General Packet Radio Service
GERAN
GSM/EDGE Radio Access Network
GPRS
General Packet Radio Service
GMM
GPRS Mobility Management
GSM
Global System for Mobile Communications
GSN
GPRS Support Node
HO
Handover
IE
Information Element
MAC
Medium Access Control
MS
Mobile Station, also referred to herein as User Equipment
(UE)
MSC
Mobile Switching Center
RLC
Radio Link Control
RNC
Radio Network Controller
RR
Radio Resources
RRC
Radio Resource Control
SGSN
Serving GPRS Support Node
TBF
Temporary Block Flow
UL
Uplink (from the MS)
UMTS
Universal Mobile Telecommunications System
URA
User (or UTRAN) Registration Area
UTRAN
Universal Terrestrial Radio Network
Reference can also be made to 3GPP TR 21.905, V4.4.0 (2001-10), Third Generation Partnership Project; Technical Specification Group Services and System Aspects; Vocabulary for 3GPP Specifications (Release 4), as well as to ETSI TR 101 748, V8.0.0 (2000-05), Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms (GSM 01.04 version 8.0.0 release 1999).
By way of introduction, reference is made to
FIG. 1
for the ensuing description of a conventional inter-system handover from UTRAN to GSM. The UE
1
receives the GSM neighbor cell parameters from the RNC of the UTRAN
3
either in a SYSTEM INFORMATION BLOCK or in a MEASUREMENT CONTROL message. These parameters are required in order to be able to measure candidate GSM cells. Based on the measurement report from the UE
1
, including GSM measurements, the RNC of the UTRAN
3
makes a handover decision. After resources have been reserved from the GSM BSS
2
, via MSC
4
, the RNC
3
sends an Inter-System Handover Command message (now also referred to as a HANDOVER FROM UTRAN COMMAND, as shown in FIG.
2
), that also carries an embedded HANDOVER COMMAND of the GSM system. At this point, the GSM RR protocol in the UE
1
takes control and sends a GSM-specific HANDOVER ACCESS message to the GSM BSC. After a successful completion of the handover procedure, the GSM BSS
2
initiates resource release from the UTRAN
3
. In response, the UTRAN
3
releases the radio connection and removes all context information for the UE
1
.
Referring to
FIG. 2
, a more detailed description of the inter-system UTRAN to GSM handover is now provided, as specified in 3GPP TS 25.303, chapter 6.4.11. For CS domain services the UTRAN to GSM inter-RAT Handover procedure is based on measurement reports from the UE
1
, but initiated from the UTRAN
3
. A HANDOVER FROM UTRAN COMMAND is sent using acknowledged data transfer on the Dedicated Control Channel (DCCH). The UE transition from the UTRAN Connected Mode starts when the HANDOVER FROM UTRAN COMMAND is received. The transition to the GSM Dedicated mode, which may also be referred to as the GSM Connected mode, is finished when the HANDOVER COMPLETE message is sent from the UE
1
.
The UTRAN
3
sends a RELOCATION REQUIRED to the CN/AS. This message contains information needed for the GSM system to be able to perform a handover (e.g. serving cell, target cell). Some parts of this information (e.g., MS classmark) are obtained at the setup of the RRC Connection and are stored in the CN.
The CN/AS sends a HANDOVER REQUEST message to BSC-RR
2
allocating the necessary resources to be able to receive the GSM UE
1
, and acknowledges this by sending HANDOVER REQUEST ACKNOWLEDGE to the CN/AS. The HANDOVER REQUEST ACKNOWLEDGE contains a GSM-RR message (HANDOVER COMMAND) with all radio-related information that the UE
1
requires for the handover.
The CN/AS then sends a RELOCATION COMMAND (type UTRAN-to-BSS HARD HANDOVER) to the UTRAN
3
to start the execution of the handover. This message contains a GSM-RR message (HANDOVER COMMAND) with all the information needed for the UE
1
to be able to switch to the GSM cell and perform a handover to GSM.
Upon receipt of the HANDOVER FROM UTRAN COMMAND message in the UE
1
, the UE-RRC entity forwards the GSM-RR message (HANDOVER COMMAND) to the MS-RR entity. To release the UTRAN resources the MS-RR entity requests the UE-RRC entity to release the RRC connection locally. The UE-RRC entity then locally releases the resources on the RLC, MAC and physical layers of the UE
1
.
After having switched to the assigned GSM channel received in the HANDOVER FROM UTRAN COMMAND, the GSM MS sends HANDOVER ACCESS in successive layer
1
frames, just as it typically would have done for a conventional GSM handover initiation.
When the BSC-RR
3
has received the HANDOVER ACCESS it indicates this to the CN/AS by sending a HANDOVER DETECT message. The BSC-RR sends a PHYSICAL INFORMATION message to the GSM MS in unacknowledged mode that contains various fields of physical layer-related information allowing a proper transmission by the MS.
After layer
1
and
2
connections are successfully established, the GSM MS returns the HANDOVER COMPLETE message. The CN/AS is then able to release the UTRAN resources that were used for the UE
1
in the UTRAN Connected Mode. The CN/AS send an IU RELEASE COMMAND to the UTRAN, after which UTRAN can release all network resources from the RLC, MAC and the physical layer. When the release operation is complete, a IU RELEASE COMPLETE message is sent to the CN/AS.
The 3GPP 33.102 specification introduces the UMTS security context. The UMTS security context is used in the Release 1999 (R99) and later UMTS and GSM system releases. Chapter 4.3.2.a of 3GPP 24.008 describes a technique whereby ciphering keys for both GSM and UMTS systems are calculated during authentication. Authentication in the UMTS system guarantees the presence of ciphering keys for both systems.
The inter-system handover (HO) between two cellular system is described in 3GPP 25.331, 04.18 and 05.08 specifications, and in 3GPP 25.303. chapter 6.4.11, Inter-RAT Handover: UTRAN to GSM/BSS, CS domain services. The GSM-RR message that is discussed in the specification 3GPP 04.18, chapter 9.1.15 is the HANDOVER COMMAND. This command is delivered within the HANDOVER FROM UTRAN COMMAND, as is discussed in 3GPP 25.331, chapter 10.2.15.
In the UMTS to GSM inter-system handover the radio system changes from the UMTS radio system to the GSM radio system while an already established user data connection or link, such as a voice data or a circuit-switched data connection, continues after the handover. During this type of inter-system handover it is important that data ciphering or encryption continues uninterrupted in order to guarantee the security goals of 3GPP 33.102. In order for this to occur the GSM ciphering must begin immediately with the first transmitted data frame when handing over to the GSM system. However, the inventors have realized that the specification 3GPP 04.18, as currently written, makes it impossible to immediately initiate the use of GSM ciphering during an inter-system handover to the GSM system.
More specifically, 3GPP 04.18, chapter 3.4.4.1, states in part:
Optionally a cipher mode setting. In that case, this ciphering mode has to be applied on the new channel. If no such information is present, the ciphering mode is the same as on the previous channel. In either case the ciphering key shall not be changed. The HANDOVER COMMAND message shall not contain a cipher mode setting IE that indicates “start ciphering” unless a CIPHERING MODE COMMAND message has been transmitted previo
Laitinen Pasi P.
Timonen Juha T.
Harrington & Smith ,LLP
Moore James K
Nokia Corporation
Vo Nguyen T.
LandOfFree
Method and apparatus for providing immediate ciphering after... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for providing immediate ciphering after..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for providing immediate ciphering after... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3153746