Method and system for bearer management in a third...

Details Method and system for bearer management in a third... Method and system for bearer management in a third...

1999-06-15

2004-02-10

Pham, Chi (Department: 2663)

Multiplex communications

Communication techniques for information carried in plural...

Adaptive

C370S230100

Reexamination Certificate

active

06690679

ABSTRACT:

TECHNOLOGICAL FIELD
The invention applies generally to the management of bearer services in a third generation mobile telecommunications system. Especially the invention applies to the establishment and upkeep of bearers for services that have different quality of service requirements between a mobile station and the fixed parts of the mobile telecommunications system.
BACKGROUND OF THE INVENTION
The denomination “mobile telecommunications system” refers generally to any telecommunications system which enables a wireless communication connection between a mobile station (MS) and the fixed parts of the system when the user of the mobile station is moving within the service area of the system. A typical mobile communications system is a Public Land Mobile Network (PLMN). The majority of mobile telecommunications systems in use at the time of filing this patent application belong to the second generation of such systems, a well-known example being the GSM system (Global System for Mobile telecommunications). The invention applies mostly to the next or third generation of mobile telecommunications systems. A system known as the UMTS (Universal Mobile Telecommunications System), which currently undergoes standardisation, is used as an example.
In third generation systems the concepts of a bearer and a service are introduced. A bearer generally corresponds to the older concept of a traffic channel, defming for example the user data rate and Quality or Service (QoS) that will be provided by the system for transferring information between a mobile station and some other part of the system. For example a bearer between the mobile station and a base station is a radio bearer and a bearer between a radio network controller and a core network is an Iu bearer (the interface between a radio network controller and a core network is called the Iu interface). A service is something that necessitates information transfer between a mobile station and the fixed parts of the system, like a phone call or the transfer of a text message. A major task for the operation of a third generation mobile telecommunications system is to manage (set up, keep up and tear down as necessary) the bearers so that each requested service can be provided to the mobile stations without wasting the available bandwidth. Some of the problems of bearer management will be illustrated in the following by referring to packet-switched data transmission finctions, where one of the most difficult tasks is to provide a truly reliable QoS for each user. The general packet radio service (GPRS) is a new service to the GSM system, and is one of the objects of the standardization work of the GSM phase 2+ and UMTS at the ETSI (European Telecommunications Standards Institute). The GPRS operational environment comprises one or more subnetwork service areas, which are interconnected by a GPRS backbone network. A subnetwork comprises a number of packet data service nodes (SN), which in this application will be referred to as serving GPRS support nodes (SGSN), each of which is connected to the mobile telecommunications system (typically to a base station through an interworking unit) in such a way that it can provide a packet service for mobile data terminals via several base stations, i.e. cells. The intermediate mobile communication network provides packet-switched data transmission between a support node and mobile data terminals. Different subnetworks are in turn connected to an external data network, e.g. to a public switched data network (PSDN), via GPRS gateway support nodes GGSN. The GPRS service thus allows to provide packet data transmission between mobile data terminals and external data networks when the appropriate parts of a mobile telecommunications system function as an access network.
In order to access the GPRS services, a MS shall first make its presence known to the network by performing a GPRS attach. This operation establishes a logical link between the MS and the SGSN, and makes the MS available for SMS (Short Message Services) over GPRS, paging via SGSN, and notification of incoming GPRS data. More particularly, when the MS attaches to the GPRS network, i.e. in a GPRS attach procedure, the SGSN creates a mobility management context (MM context). Also the authentication of the user is carried out by the SGSN in the GPRS attach procedure. In order to send and receive GPRS data, the MS shall activate the packet data address that it wants to use, by requesting a PDP activation procedure (Packet Data Protocol). This operation makes the MS known in the corresponding GGSN, and interworking with external data networks can commence. More, particularly a PDP context is created in the MS and the GGSN and the SGSN. The PDP context defines different data transmission parameters, such as the PDP type (e.g. X.25 or IP), PDP address (e.g. X. 121 address), quality of service (QoS) and NSAPI (Network Service Access Point Identifier). The MS activates the PDP context with a specific message, Activate PDP Context Request, in which it gives information on the TLLI, PDP type, PDP address, required QoS and NSAPI, and optionally the access point name (APN).
The quality of service defines how the packet data units (PDUs) are handled during the transmission through the GPRS network. For example, the quality of service levels defmed for the PDP addresses control the order of transmission, buffering (the PDU queues) and discarding of the PDUs in the SGSN and the GGSN, especially in a congestion situation. Therefore, different quality of service levels will present different end-to-end delays, bit rates and numbers of lost PDUs, for example, for the end users.
For each PDP address a different QoS may be requested. For example, some PDP addresses may be associated with E-mail that can tolerate lengthy response times. Other applications cannot tolerate delay and demand a very high level of throughput, interactive applications being one example. These different requirements are reflected in the QoS. If a QoS requirement is beyond the capabilities of a PLMN, the PLMN negotiates the QoS as close as possible-to the requested QoS. The MS either accepts the negotiated QoS, or deactivates the PDP context.
Current GPRS QoS profile contains five parameters: service precedence, delay class, reliability, and mean and peak bit rates. Service precedence defines some kind of priority for the packets belonging to a certain PDP context. Delay class defines mean and maximum delays for the transfer of each data packet belonging to that context. Reliability in turn specifies whether acknowledged or unacknowledged services will be used at the protocol layers where such alternatives are available—examples in the known systems are the LLC (Logical Link Control) and RLC (Radio Link Control) layers. In addition, it specifies whether protected mode should be used in case of unacknowledged service, and whether the GPRS backbone should use TCP or UDP to transfer data packets belonging to the PDP context. Furthermore, these varying QoS parameters are mapped to a number of QoS levels available at certain protocol layers.
The known aspects of bearer management and QoS mapping are usually associated with the LLC layer. It has been proposed that the LLC layer should be omitted from future wireless packet-switched communication systems, but the following considerations are in any case useful in understanding the background of the invention.
FIG. 1
illustrates the operation of a known LLC protocol layer
101
in a known Mobile Station (MS) or Serving GPRS Support Node (SGSN). Block
102
represents the known lower layer (RLC/MAC; Radio Link Control/Media Access Control) functions that are needed below the LLC layer
101
in a mobile station. Correspondingly block
103
represents the known lower layer (BSSGP; Base Station Subsystem GPRS Part) finctions that are needed below the LLC layer
101
in a SGSN. The interface between the LLC layer
101
and the RLC/MAC layers is called the RR interface and the interface between the LLC layer
101
and the BSSGP layers is called th

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