Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-11-23
2003-12-30
Trost, William (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S452200, C455S450000, C455S455000, C370S329000, C370S337000, C370S348000, C370S349000, C370S355000
Reexamination Certificate
active
06671511
ABSTRACT:
The invention relates generally to a method and an arrangement for transferring information in a packet radio service. Especially the invention applies to transferring delay sensitive data, such as speech and video data, in a mobile telecommunications system.
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 the filing of this patent application belong to the second generation of such systems, a well-known example being the GSM system (Global System for Mobile telecommunications). However, the invention also applies to the next or third generation of mobile telecommunications systems, such as a system known as the UMTS (Universal Mobile Telecommunications System) which currently undergoes standardisation.
Internet real time services have gained popularity during the past few years. IP (Internet Protocol) telephony and different streaming applications are already common in the Internet. Also the demand for wireless access to these real time services is expected to be still growing. Packet switched wireless networks, such as GPRS (General Packet Radio Service), are designed to provide data services, e.g. Internet services, cost effectively. In GPRS the channels are not dedicated for one user continuously but are shared between multiple users. This facilitates efficient data multiplexing. However, GPRS is not originally designed for transferring delay sensitive real time data, e.a. IP telephony sessions. For this reason, GPRS contains various technical solutions that do not meet the requirements set by real time traffic. In the following text, a denomination “delay sensitive data” is used for data flows that should be transferred on real time basis and that may have passive periods during which the data flow is suspended.
In order to better understand the problems of the prior art solutions and the idea of the present invention, the structure of a third generation digital cellular radio system is first shortly described, and GPRS is then described in more detail.
FIG. 1
a
shows a version of a future cellular radio system which is not entirely new compared to the known GSM system but which includes both known elements and completely new elements. The terminals are connected to the radio access network RAN which includes the base stations and the base station controllers. The core network of a cellular radio system comprises mobile services switching centers (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 related transmission systems. According, e.g. to the GSM+ specifications developed from GSM, the core network can also provide new services.
In
FIG. 1
a
, the core network of a cellular radio system
10
comprises a GSM+ core network
11
which has three parallel radio access networks linked to it. Of those, networks
12
and
13
are UMTS radio access networks and network
14
is a GSM+ radio access network. The upper UMTS radio access network
12
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
13
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
13
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
12
,
13
and
14
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 generic radio access networks (GRAN). 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 generic radio access network (GRAN) can be defined as a set of base stations (BS) and radio network controllers (RNC) that are capable of communicating with each other using signaling messages.
FIG. 1
b
shows an architecture of a general packet radio service (GPRS). The GPRS is a new service that is currently based on the GSM system but it is supposed to be generic in the future. GPRS is one of the objects of the standardisation 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)
153
, 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
151
via several base stations
152
, i.e. cells. The intermediate mobile communication network provides packet-switched data transmission between a support node and mobile data terminals
151
. Different subnetworks are in turn connected to an external data network, e.g. to a Public Data Network (PDN)
155
, via GPRS gateway support nodes GGSN
154
. The GPRS service thus allows the provision of 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 mobile station shall first make its presence known to the network by performing a GPRS attachment. This operation establishes a logical link between the mobile station and the SGSN, and makes the mobile station available for SMS (Short Message Services)
158
,
159
, over GPRS, paging via SGSN, and notification of incoming GPRS data. More particularly, when the mobile station attaches to the GPRS network, i.e. in a GPRS attachment 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 attachment procedure. In order to send and receive GPRS data, the MS shall activate the packet data address wanted to be used, by requesting a PDP activation procedure (Packet Data Protocol). This operation makes the mobile station known in the corresponding GGSN, and interworking with external data networks can commence. More particularly, a PDP context is created in the mobile station and the GGSN and the SGSN. The packet data protocol context defines different data transmission parameters, such as the PDP type (e.g. X.25 or IP), the PDP address (e.g. X.121 address), the quality of service (QoS) and the 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, the PDP type, the PDP address, the required QoS and the NSAPI, and optionally the access point name (APN).
FIG. 1
also shows the following GSM functional blocks: Mobile Switching Center (MSC)/Visitor Location Register (VLR)
160
, Home Location Register (HLR)
157
and Equipment Identity Register (EIR)
161
. The GPRS system is usually also connected to other Public Land Mobile Networks (PLMN)
156
.
Functions applying digital data transmission protocols are usually described as a sta
Forssell Mika
Parantainen Janne
Nokia Mobile Phones Ltd.
Perman & Green LLP
Trost William
Zewdu Meless
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