Signalling method

Details Signalling method Signalling method

2001-08-23

2004-05-25

Nguyen, Duc M. (Department: 2685)

Telecommunications

Radiotelephone system

Zoned or cellular telephone system

C455S426100, C455S560000

Reexamination Certificate

active

06741860

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The invention concerns control of connections in cellular telecommunication systems, particularly setting up and releasing of connections.
BACKGROUND OF THE INVENTION
For clarification of common terms used in this document, an overview of certain cellular telecommunication system configurations is presented in the following.
Proposals for third-generation systems include UMTS (Universal Mobile Telecommunications System) and FPLMTS/IMT-2000 (Future Public Land Mobile Telecommunications System/International Mobile Telecommunications at 2000 MHz). In these plans cells are categorised according to their size and characteristics into pico-, nano-, micro- and macrocells, and an example of the service level is the bit rate. The bit rate is the highest in picocells and the lowest in macrocells. The cells may overlap partially or completely and there may be different terminals so that not all terminals necessarily are able to utilise all the service levels offered by the cells.
FIG. 1
shows a version of a future cellular radio system which is not entirely new compared with the known GSM system but which includes both known elements and completely new elements. In current cellular radio systems the bottleneck that prevents more advanced services from being offered to the terminals comprises the radio access network RAN which includes the base stations and base station controllers. The core network of a cellular radio system comprises mobile services switching centres (MSC), other network elements (in GSM, e.g. SGSN and GGSN, i.e. Serving GPRS Support Node and Gateway GPRS Support node, where GPRS stands for General Packet Radio Service) and the related transmission systems. According e.g. to the GSM+ specifications developed from GSM the core network can also provide new services.
In
FIG. 1
, the core network of a cellular radio system
20
comprises a core network CN
931
which has three parallel radio access networks linked to it. Of those, networks
932
and
933
are UMTS radio access networks and network
934
is a GSM radio access network. The upper UMTS radio access network
932
is e.g. a commercial radio access network, owned by a telecommunications operator offering mobile services, which equally serves all subscribers of said telecommunications operator. The lower UMTS radio access network
933
is e.g. private and owned e.g. by a company in whose premises said radio access network operates. Typically the cells of the private radio access network
933
are nano- and/or picocells in which only terminals of the employees of said company can operate. All three radio access networks may have cells of different sizes offering different types of services. Additionally, cells of all three radio access networks
932
,
933
and
934
may overlap either entirely or in part. The bit rate used at a given moment of time depends, among other things, on the radio path conditions, characteristics of the services used, regional overall capacity of the cellular system and the capacity needs of other users. The new types of radio access networks mentioned above are called UMTS terrestrial radio access networks (UTRAN). Such a network can co-operate with different types of fixed core networks CN and especially with the GPRS network of the GSM system. The UMTS terrestrial radio access network (UTRAN) can be defined as a set of base stations (BS) and radio network controllers (RNC) that are capable of communicating with each other using signalling messages.
The terminal
10
shown in
FIG. 1
is preferably a so-called dual-mode terminal that can serve either as a second-generation GSM terminal or as a third-generation UMTS terminal according to what kind of services are available at each particular location and what the user's communication needs are. It may also be a multimode terminal that can function as terminal of several different communications systems according to need and the services available. Radio access networks and services available to the user are specified in a subscriber identity module
936
(SIM) connected to the terminal.
FIG. 1
further shows some details of the structure of a radio access network. A radio access network
932
,
934
typically comprises one or more base stations
937
and a controlling unit
42
. In UMTS radio access networks
932
,
933
the controlling unit is called the radio network controller (RNC), and in GSM networks
934
the controlling unit is called a base station controller (BSC). The radio access networks typically comprise also other network elements such as transcoder units.
FIG. 1
further shows a mobile services switching centres (MSC)
43
which basically controls circuit-switched connections of mobile stations
10
and a Serving GPRS Support Node (SGSN)
41
which basically controls packet switched connections of mobile stations
10
.
In cellular telecommunication systems, connections are set up and resources reserved on demand and released when not needed Moving mobile stations place additional requirements for the system, connections need to be transferred from one base station to another, which often requires a substantial change in the routing of the connection through the network. The exchanges of information between various network elements which are necessary for executing such functionality are handled by mobility management (MM protocols and radio resource control (RRC) protocols. Mobility management protocols mainly take care of the mechanisms allowing a mobile station to move within the cellular network and security issues, while RRC protocols mainly take care of controlling the use of radio resources over the air interface, the connection between a mobile station and the BSC/RNC, and handovers. The execution of the RRC protocols is mainly performed by the mobile station and the BSC/RNC. Some parts of the RRC protocol, such as functionality related to inter-MSC handovers, are executed by the MSC. The execution of the MM protocols is mainly performed by the mobile station and the MSC. The protocols used in the GSM system are described further in the book “The GSM System for Mobile Communications” by Michel Mouly and Marie-Bernadette Pautet, ISBN 2-9507190-0-7, Palaiseau 1992. Mobility management protocols for third generation cellular networks are discussed, for example, in patent application WO 98/37721, where emphasis is set on minimizing the number of MM messages sent over radio interface in situations, where a radio access network is connected to, for example, many core networks, each having dedicated mobility management.
In principle, the MM and RRC protocols are mainly separate. However, in order to reduce signalling, many MM functions are started or finished as a result of events in the RRC level, without explicit messaging in the MM level. For example, during releasing of a connection in the present GSM system, the MM protocol changes its state from a WAIT FOR NETWORK COMMAND state to the IDLE state as a response to releasing of the radio resources in the RRC level. Therefore, the releasing of radio resources in the RRC level implicitly acts as a control signal for the MM level. However, this approach creates problems in the new cellular systems under development, such as the UMTS system. Some of these problems are described in the following with reference to FIG.
2
.
FIG. 2
shows a mobile station
10
and the cellular network
20
, various entities taking care of executing the protocols such as the MM protocol entity
11
and the RRC protocol entity
12
of the mobile station. At the network side, corresponding entities are the MM protocol entity
21
in the MSC and the RRC protocol entity
22
in the RNC. The MM and RRC entities are typically realized using software programs executed by a processing unit such as a microprocessor in the control unit of a MS or a network element.
Some services take care of the mobility management of their connections themselves, independently from the MSC. An example of such services is the GPRS service. Their independent mobility managem

Affiliated with

Also associated with

Rating

Signalling method does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Signalling method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Signalling method will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3217929