Patent Application
20080291872
The present invention relates to packet data communications systems such as GSM and code division multiplex access (CDMA) systems such as UMTS systems (W-CDMA (Wideband Code Division Multiplex Access)). More particularly, the present invention relates to aspects of Radio access bearer setup in 3GPP (Third Generation Partnership Project) systems.
The main purpose of the WCDMA Radio Access Network, see schematic example given in
As is well known, the WCDMA Radio Access Network Comprises Two Types of Nodes:
The Radio Base Station (Node B) handles the radio transmission and reception to/from the handset over the radio interface (Uu). It is controlled from the Radio Network Controller via the lub interface. One Radio Base Station can handle one or more cells.
The Radio Network Controller (RNC) controls all WCDMA Radio Access Network functions. It connects the WCDMA Radio Access Network to the core network via the lu interface. There are two distinct roles for the RNC, to serve and to control. The Serving Network controller has overall control of the handset that is connected to WCDMA Radio Access Network. It controls the connection on the lu interface for the handset and it terminates several protocols in the contact between the handset and the WCDMA Radio Access Network. The Controlling RNC has the overall control of a particular set of cells, and their associated base stations.
When a handset requires resources in a cell that are not controlled by its Serving RNC, the Serving RNC must ask the Controlling RNC for those resources. This request is made via the lur interface, which connects the RNC with each other. In this case, the Controlling RNC is also said to be a Drift RNC for this particular handset. This kind of operation is primarily needed to be able to provide soft handover throughout the network.
The main service offered by WCDMA RAN is providing the Radio Access Bearer (RAB). To establish a call connection between the handset and the base station a RAB is needed. The characteristics of the Radio Access Bearers are different depending on what kind of service/information is to be transported.
The RAB carries the subscriber data between the handset and the core network. It is composed of one Radio Bearer between the handset and the Serving RNC, and one lu bearer between the Serving RNC and the core network.
The 3GPP standardisation body has defined four different quality classes of Radio Access Bearers:
Both the Conversational and Streaming RABs require a certain reservation of resources in the network, and are primarily meant for real-time services. The latter RAB types differ mainly in that the Streaming RAB tolerates a higher delay as long as the delay variation is kept low, appropriate for one-way real-time services.
The Interactive and Background RABs are also called ‘best effort’, i.e. no resources are reserved and the throughput depends on the load in the cell. The only difference between the latter RAB's is that the Interactive RAB provides a priority mechanism.
The RAB is characterized by certain Quality of Service (QoS) parameters, such as bit rate and delay.
The core network will select a RAB with appropriate QoS based on the service request from the subscriber, and ask the RNC to provide such a RAB.
The WCDMA Radio Access Network nodes communicate with each other over a trans-port network. The 3GPP specifications provide a very clear split between radio related (WCDMA) functionality and the transport technology, meaning that there is no particular bias to any technology. The transport network may be based on ATM (Asynchronous Transfer Mode) or IP (Internet Protocol).
Transport of packet data units (PDU) between a user entity and a packet data provider network is achieved by means of the GTP (GPRS (General Packet Radio System) Tunnelling Protocol) protocol. The tunnelling protocol utilises encapsulation of Internet packets in GTP packets.
The tunnelling is setup via so-called Packet Data Protocol (PDP) contexts, which exist in the user entities, the SGSN (Serving GPRS Support Node) and the GGSN (Gateway GPRS Support Node). Moreover, the service characteristics of the transmission of PDU are controlled according to the established PDP context. In order to transmit or receive data the user entity must be attached, inferring that a “radio connection” is established between the user entity and the radio base station and a PDP context is activated.
The PDP context comprises
In document 3GPPTS23.060 V6.9.0, the procedure for PDP-context activation, -modification, -deactivation and -preservation functions are explained.
In
According to the known procedure, the Mobile Station sends an Activate PDP Context Request message to the SGSN at power-on or upon activation of a specific service, indicated by “start 0”. The SGSN in turn evaluates (not shown) the request and selects a GGSN to which it sends a Create PDP Context Request, step 4. The GGSN replies with a Create PDP Context Response 4′ to the SGSN if the evaluation is positive. Normally, the PDP Context is activated when the user starts a service e.g. sends an MMS. However, some operators have an always-on principle that means that the mobile activates the PDP Context when they are powered-on. Mobility events such as cell change don't trigger activations.
Thereafter, the SGSN performs the known RAB setup procedure 5.
On the other hand, if the GGSN sends a negative response, the SGSN sends an Activate PDP Context Reject message 9′ to the mobile station.
The GGSN responds by sending a Create PDP Context Response to the SGSN, step 4′.
Dependent on the outcome of the RAB setup procedure, the SGSN sends an Activate PDP Context Accept message, 9, if the RAB setup was successful or an “Activate PDP Context Reject message 9’ if the RAB set-up failed. The RAB set up could fail for various reasons such as insufficient link conditions.
Those mobile stations for which the PDP Context activation attempt failed will have to try again to activate the PDP Context at a later stage. This might require manual interaction from the user.
In existing networks, the RAB Assignment procedure is typically performed at PDP Context activation regardless if the RAB that is established will be used for data traffic immediately or later in time. This behaviour has the effect that radio network resources, such as CDMA code space are reserved unnecessarily resulting in a poorly utilized network. Especially for operators whose business models rely on always-on communication, the behaviour can affect service performance.
It is a primary object of the invention to reduce the number of PDP Context activation failures and to better utilise scarce radio network resources.
This object has been accomplished by the subject matter set forth in claim 1.
It is a secondary object of the invention to provide an alternative way of reducing the number of PDP Context activation failures and to better utilise scarce radio network resources.
This object has been accomplished by the subject matter set forth in claim 8.
Further advantages will appear from the following detailed description of the invention.
As illustrated in
In the following, the reference signs of
As in the prior art, should the GGSN for some reason reject the PDP Context activation attempt 4, i.e. not issue a create PDP context response 4′, the activation procedure is stopped 4B and the Mobile Station is notified with an Activate Context Reject message 9′. In this situation, the Selective RAB Assignment concepts according to the invention are not carried out.
On the other hand, if the Create PDP Context procedure, confer messages 4 and 4′, towards the GGSN is successful, condition 4B, the SGSN will use the selective RAB Assignment procedures described in the following. According to a first aspect of the invention, the SGSN may act in different ways depending on the outcome of Selective RAB Assignment evaluation criteria. According to further aspects of the invention, no RAB assignment or no RAB set up evaluation is carried out.
According to a first aspect of the invention, user and/or service related information is applied as a criterion for when and how the radio network is requested to reserve resources during connection setup. More specifically, the SGSN uses subscription information readily available in the SGSN, to decide if the RAB Assignment procedure shall be run as part of a specific PDP Context activation procedure according to preferred embodiments of the present invention.
The selective RAB Assignment according to a first aspect of the invention is based on an evaluation being carried out on predetermined RAB set-up criteria 4B being based on information in the Mobility Management (MM) Context and/or the PDP Context. The contents of the MM Context and PDP Context are defined in the 3GPP specification 23.060. Typical fields that may be evaluated are the IMSI (International Mobile Sub-scriber Identity) and the Routeing Area in the MM Context and the APN (Access Point Name) and the QoS (Quality of Service) in the PDP Contexts.
As regards the PDP Context evaluation criteria, the following criteria may be used according to the invention:
According to a first embodiment of the invention shown in
There is provided Method of controlling radio access bearer setup in a radio network, wherein a set of predetermined RAB setup criteria 4C are defined, the method comprising the steps of
If the RAB set up criteria evaluation above is negative (4C) the SGSN sends an Activate PDP Context Accept message (9) to the mobile station.
If the RAB set up above is not successful (5B) the SGSN sends an Activate PDP Context Reject message (9′) to the mobile station.
In the above example it appears that mobile stations having a low quality of service level (Best effort) will not be allocated radio resources, when activating a PDP Context at e.g. power-on, whereas mobile stations with higher QoS will. Thereby the radio access bearer demand is reduced.
According to a second embodiment of the invention shown in
There is provided a method of controlling radio access bearer setup in a radio network, wherein a set of predetermine RAB setup criteria are defined. The method comprises the steps of the SGSN
When the SGSN receives a positive Create PDP Context Response from the GGSN, the RAB assignment procedure 5 is carried out or at least initiated, whereupon an Activate PDP Context Accept is issued to the mobile station in question.
When the SGSN does not receive a positive Create PDP Context Response from the GGSN, the RAB assignment procedure 5 is not carried out, and an Activate PDP Context Reject 9′ is issued to the mobile station in question as in the prior art.
This has the effect that if the RAB setup was successful, the mobile station will be able to communicate directly with e.g. the host in the Internet that provides the requested service with a minimum of setup delay.
If, on the other hand the RAB setup failed, the mobile station will still receive an Activate PDP Context Accept signal from the SGSN but it will have to perform a separate Service Request and RAB assignment in order to send and receive data. However, the mobile station needs not to perform a complete PDP Context activation procedure. A second attempt to activate the service as a RAB assignment according to the second embodiment is much quicker than a complete PDP Context activation as the GGSN communication and parts of the QoS negotiation are already done. This again has the effect that the second service setup attempt will be quicker and it will not require any manual intervention as the standalone RAB assignment procedure takes shorter time and is less susceptible to failures than the complete PDP Context activation procedure.
According to the third embodiment of the invention shown in
If no Create PDP context response is received, it is found that the response from the GGSN is negative, whereupon the SGSN transmits an Activate PDP Context Reject 9′ message to the mobile station.
This has the effect that for services that do not require that a communication path is setup through the network immediately at PDP Context activation, no RABs are setup at a time where they are not a seen as needed. This again has the effect that less radio resources are wasted and less radio interference is created as the RABs that would otherwise have been setup would need resources such as but not limited to signal code space and output power from the mobile station and the network base stations. The main benefit with the third embodiment is that for services that do not require a RAB to be setup immediately there is no extra signalling and less radio resources are wasted.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2005/054020 | 12/2/2005 | WO | 00 | 6/2/2008 |
