HK1085076B - Allocating data transmission resources in packet-switched data transmission - Google Patents

Description

Allocating data transmission resources in packet switched data transmission

Background

The present invention relates to allocating data transmission resources in packet switched data transmission and in particular to optimizing radio interface resources in wireless packet switched data transmission.

Third generation mobile systems, known as UMTS (universal mobile telecommunications system) and IMT-2000 (international mobile telephony system), will provide not only circuit switched voice services but also packet switched services in the form of a packet radio network GPRS (general packet radio service) designed for GSM systems. Packet-switched data transmission enables the use of mobile stations and, on the other hand, the allocation of mobile system resources, in particular radio interfaces, to the required users for the use of different data services.

When a terminal user of the UMTS system wants to use a packet switched application, for example to download a video file from the network to the terminal, the radio resource management system RRM of the UMTS system allocates an application based capacity reservation for the radio bearers, which depends not only on the application used but also on the available radio bearer parameters. In a typical unidirectional data transmission, for example, when downloading a file from the network, the terminal may be allocated a data rate of x bits/second in the downlink direction (from the base station to the terminal) and a data rate of 0 bits/second in the uplink direction (from the terminal to the base station). In such applications, uplink data transmission is typically not required and, therefore, resources need not be allocated thereto.

One of the parameters defining a radio bearer is the method used by the terminal to compress the header field of the data packet. Header compression of transmitted data packets and decompression of received data packets are performed on the packet data convergence protocol layer PDCP of the UMTS system. The PDCP layer of the terminal typically supports several header compression methods in order to enable connection establishment with as many network layer protocols as possible. Some header compression methods also require a reverse connection for making different acknowledgements and resolving error conditions. The determined bandwidth then needs to be reserved for the reverse connection, but, on the other hand, compression of the header field reduces the bandwidth requirement of the forward connection.

The problem with the above solution comes from using application based capacity allocation together with header compression methods that require bi-directional connections. If the terminal has only header compression methods available to it that require a bi-directional connection and the terminal sends a capacity allocation request to an application, which is typically unidirectional, such as downloading a file from the network as described above, the radio resource management system RRM allocates a unidirectional connection for the radio bearer only on the basis of the application. The available compression methods cannot operate and the connection cannot be established without being able to reserve sufficient bandwidth for the reverse connection with the particular scheme involving the new capacity allocation request. In all cases this is not possible and, in any case, such a scheme complicates an optimal allocation of radio resources.

Brief description of the invention

It is therefore an object of the present invention to devise an improved method and apparatus for carrying out the method so as to reduce the above-mentioned disadvantages.

According to one aspect of the present invention there is provided a method of allocating data transmission resources in a packet switched telecommunications system comprising a terminal and a fixed network on which is defined an operable entity for defining resources for a radio bearer, wherein the radio bearer resources are defined for the terminal on the basis of an application used by the terminal on the radio bearer, characterised by defining a compression method for a header field in a data packet used on the radio bearer before defining the resources for the radio bearer, and defining the resources of the radio bearer in such a way that the resources also include capacity required by the selected compression method for the header field in the data packet.

According to another aspect of the present invention there is provided a packet switched telecommunications system comprising a terminal and a fixed network comprising an operable entity for defining resources for a radio bearer, in which system the resources of a radio bearer are arranged to be defined on the basis of an application used by the terminal on said radio bearer, characterised in that a compression method for a header field in a data packet used on the radio bearer is arranged to be defined before the radio bearer resources are defined, and said radio bearer resources are arranged to be defined in such a way that said resources also comprise the capacity required by a selected compression method for the header field in the data packet.

According to another aspect of the present invention there is provided a network element for a packet switched telecommunications system, the network element comprising an operable entity for defining resources for radio bearers, the network element being arranged to: defining a compression method of a header field in a data packet for use on a radio bearer; defining resources of the radio bearer based on an application used by a terminal on the radio bearer; and controlling the definition of said radio bearer resources in accordance with the capacity required by the selected compression method of the header fields in the data packet.

According to another aspect of the present invention there is provided a terminal for a packet switched telecommunications system, the terminal comprising an application capable of requesting radio bearer resources from a network of the packet switched telecommunications system, said terminal being arranged to: transmitting information on compression methods of header fields in data packets supported by the terminal to the network, and performing data transmission of the one application according to a configuration of radio bearer resources defined by the network, thereby controlling the definition of the radio bearer resources according to a capacity required by the selected header field compression method.

The invention is based on selecting a compression method that has been used on the radio link before the radio bearer is established and this information is sent to the radio resource management system RRM, which takes into account the bi-directional compression algorithm that may be selected in the capacity allocation and allocates the required capacity for the downlink and uplink.

The method and system of the present invention provide the advantage that header compression methods requiring a bi-directional connection can also be run immediately on radio bearers due to applications requiring only unidirectional radio bearers. Another advantage is that no additional signalling is needed to establish the reverse connection, since the bi-directional characteristic is already taken into account when establishing the radio bearer. Another advantage is that the overall bandwidth allocated to the radio bearer can be optimized when considering the bandwidth required by the compression method and the benefits deriving from the use of the compression algorithm as a smaller data volume.

Brief Description of Drawings

The invention will now be described by way of preferred embodiments with reference to the accompanying drawings, in which:

figure 1 shows a block diagram of the structure of a UMTS system,

figures 2a and 2b show the protocol stacks for UMTS control signaling and user data transmission,

figure 3 shows a block diagram of a functional model of the PDCP layer,

fig. 4 shows capacity allocation signaling for an embodiment of the present invention.

Detailed Description

In the following, the invention will be described using a packet radio service according to the UMTS system as an example. However, the invention is not limited to UMTS systems but can be applied to any packet switched data transmission method for which the capacity allocation of the packet data connection requires the use of header compression methods to be taken into account.

The structure of a UMTS mobile telephone system is depicted in fig. 1. Fig. 1 contains only the blocks that are essential for explaining the invention, but it is obvious to a person skilled in the art that a conventional mobile telephone system also comprises other functions and structures, which need not be described in more detail here. The main parts of the mobile telephone system are the core network CN, the UMTS mobile telephony system terrestrial radio access network UTRAN, and the mobile stations or user equipment UE. The interface between the CN and the UTRAN is called lu and the interface between the UTRAN and the UE is called Uu.

The UTRAN typically comprises several radio network subsystems RNS, the interface between which is called lur (not shown). The RNS comprises a radio network controller RNC and one or more base stations BS, also called node BS. The interface between RNC and B is called lub. The base station BS typically handles the radio path implementation and the radio network controller RNC manages at least the following aspects: management of radio resources, control of handovers between cells, power regulation, timing and synchronization, paging of user terminals.

The core network CN consists of infrastructure belonging to the mobile telephone system and external to the UTRAN. In the core network, a mobile switching centre/visitor location register 3G-MSC/VLR is connected to a home location register HLR and preferably also to a service control point SCP of the intelligent network. The home location register HLR and the visitor location register VLR comprise information about mobile subscribers: the home location register HLR contains information about all subscribers in the mobile network and the services to which it subscribes, and the visitor location register VLR contains information about mobile stations visiting the area of a certain mobile switching centre MSC. A connection is formed to the serving node of the packet radio system 3G-SGSN (serving GPRS support node) through the interface Gs' and to the fixed telephone network PSTN/ISDN through the gateway mobile switching centre GMSC (not shown). The connection from the serving node 3G-SGSN to the external data network PDN is formed through an interface Gn to a gateway node GGSN (gateway GPRS support node) further connected to the external data network PDN. A connection is established from the mobile switching centre 3G-MSC/VLR and the serving node 3G-SGSN to the radio network UTRAN (UMTS terrestrial radio access network) via the interface lu. It should be noted that the UMTS system is designed in such a way that the core network CN may be identical to that of the GSM system, for example, in which case the entire network infrastructure need not be re-established.

The UMTS system also comprises a packet radio system which is implemented to a large extent in accordance with the GPRS system connected to the GSM network, to which reference is made in the name of network elements. UMTS packet radio needs may comprise several gateways and service nodes and several service nodes 3G-SGSN are typically connected to one gateway node 3G-GGSN. The nodes 3G-SGSN and 3G-GGSN act as routers supporting mobility for the mobile stations, controlling the mobile system and routing data packets towards the mobile stations irrespective of their location and protocols used. The serving node 3G-SGSN contacts the mobile station MS via the radio network UTRAN. The task of the serving node 3G-SGSN is to detect mobile stations capable of establishing packet radio connections in its service area for sending and receiving data packets to and from said mobile stations and to track the location of the mobile stations in its service area. Furthermore, the serving node 3G-SGSN is in contact with the mobile switching centre 3G-MSC and the visitor location register VLR via a signalling interface Gs' and with the home location register HLR via an interface Gr. Records associated with the packet radio service and comprising subscriber-specific packet data protocol content are also stored in the home location register HLR.

The gateway node 3G-GGSN acts as a gateway between the UMTS network packet radio system and the external data network PDN (packet data network). The external data network comprises a UMTS or GPRS network of the second network operator, the internet, an x.25 network or a private local area network. The gateway node 3G-GGSN contacts said data network via an interface Gi. Data packets sent between the gateway node 3G-GGSN and the serving node 3G-SGSN are always encapsulated according to the gateway tunneling protocol GTP. The gateway node 3G-GGSN also includes the PDP (packet data protocol) address of the mobile station and routing information, i.e. the 3G-SGSN address. The routing information is used to link data packets between the external data network and the serving node 3G-SGSN. The network between the gateway node 3G-GGSN and the serving node 3G-SGSN uses an IP protocol, preferably IPv6 (internet protocol, version 6).

Figures 2a and 2b show the UMTS protocol stack for controlling signalling (control plane) and user data transmission (user plane) in the packet radio service of the UMTS system. Fig. 2a shows a protocol stack for controlling signaling between a mobile station MS and a core network CN. The mobility management MM, the call control CC and the session management SM of the mobile station MS are signaled at the highest protocol layer between the mobile station MS and the core network CN in such a way that the base station BS and the radio network controller RNC located in between are transparent to this signaling. The radio resource management of the radio link between the mobile station MS and the base station BS is managed by a radio resource management system RRM which transmits control data from the radio network controller RNC to the base station BS. These functions related to the general management of mobile systems constitute a group called core network protocol (CN protocol), also called non-access stratum. In contrast, the signaling related to the radio network control between the mobile station MS, the base station BS and the radio network controller RNC is done at a protocol layer called the radio access network protocol (RAN protocol), i.e. the access layer. These include the transport protocols at the lowest layer, whose control signaling is sent to the higher layers for further processing. The most basic of the higher access stratum is the radio resource control protocol RRC responsible for establishing, configuring, maintaining and releasing the radio link between the mobile station MS and the radio network UTRAN, and sending control information from the core network CN and the radio network RAN to the mobile station MS. In addition to this, the radio resource control protocol RRC is responsible for allocating sufficient capacity for the radio bearers in e.g. application based capacity allocation according to the instructions of the radio resource management system RRM.

The protocol stack shown in figure 2b is used for transmitting UMTS packet switched user data. On the Uu interface between the radio network UTRAN and the mobile station MS, lower layer data transmission on the physical layer is performed according to the WCDMA or TD-CDMA protocol. The MAC layer on the physical layer sends data packets between the physical layer and the RLC layer handles the logical management of the radio links of the different radio bearers. The RLC functions include, for example, segmentation of user data (RLC-SDU) to be transmitted into one or more RLC data packets RLC-PDU. Data packets of the PDCP layer above the RLC (PDCP-PDU), including header fields of higher layers, may optionally be compressed. Thereafter, the PDCP-PDUs are forwarded to the RLC and they correspond to one RLC-SDU. User data and RLC-SDU are segmented and transmitted in RLC frames, to which address and authentication information essential for data transmission are added. The RLC layer is also responsible for retransmission of corrupted frames. The serving node 3G-SGSN manages the routing of data packets from the mobile station MS through the radio network RAN to the correct gateway node 3G-GGSN. This connection uses the tunneling protocol GTP, which encapsulates and tunnels all user data and signaling through the core network. The GTP protocol runs on top of the IP used by the core network.

One of the tasks of the PDCP layer is to enable data packets from the higher application level layer to be transferred transparently between the UMTS terminal and the elements of the radio network UTRAN to the lower link level layer and vice versa. Therefore, it must be possible to modify the PDCP layer in such a way that it can also send data packets of other network-level protocols than the IP protocol already supported (IPv4, IPv 6).

Another important task of the PDCP layer includes functions related to improving channel efficiency. These functions are typically based on different optimization methods, such as compression algorithms for the data packet header field. Since the network-level protocol currently planned for UMTS is the IP protocol, the compression algorithms used are those standardized by the IETF (internet engineering task force). However, any header compression algorithm selected according to the network-level protocol used in each case may be applied to the PDCP layer. Some header compression algorithms require a bi-directional connection between the terminal and the network and therefore may handle various acknowledgements and manage recovery from errors.

The tasks of the PDCP layer also include sending data packets PDCP-SDU and related PDCP sequence number to the new radio network subsystem in an internal handover between UMTS radio network subsystems (SRNS relocation). Another task is to multiplex several radio bearers into the same one RLC entity when needed.

Fig. 3 shows a functional model of the PDCP layer, in which one PDCP entity is defined for each radio bearer. Since in current systems a single PDP context is defined for each radio bearer, one PDCP entity is also defined for each PDP context and a certain RLC entity is defined for each PDCP entity on the RLC layer. As mentioned, the PDCP layer may in principle be operatively implemented in such a way that several PDP contexts are multiplexed on the PDCP layer, in which case one RLC entity receives data packets from several radio bearers simultaneously on the RLC layer below the PDCP layer.

Each PDCP entity may use one or more header compression algorithms or no algorithm. Several PDCP entities can also use the same algorithm. The radio resource controller RRC negotiates an appropriate algorithm and parameters controlling the algorithm for each PDCP entity and then proposes the selected algorithm and parameters to the PDCP layer through a PDCP-C-SAP point (PDCP control service access point). The compression method used depends on the type of network level protocol used on the connection, the type indicated for the radio resource controller when activating the PDP context.

Indication and differentiation of various compression methods on the PDCP layer is achieved by means of packet identifiers pID connected to data packet PDUs. A table is created for the packet identifier PID values of each PDCP entity, wherein different compression algorithms are matched to different data packets and the value of the packet identifier PID is determined as a combination of these. If no compression algorithm is used, the packet identifier PID gets a value of zero. For each compression algorithm and its combination with different data packet types, the PID values are determined sequentially in such a way that the PID value of each compression algorithm starts from n +1, where n is the last PID value defined for the previous compression algorithm. The order of the compression algorithms is determined in a negotiation with the radio resource controller RRC. The PDCP entity at the end of each data packet connection can identify a compression algorithm for transmitting and receiving data packets based on the PID value table. However, this information is not stored in the radio resource controller RRC.

In application-based capacity allocation, where for example a mobile station MS sends a request to the network for establishing a radio bearer, the capacity request is sent as control signalling from the mobile station MS to a function SM (session management) managing the core network connection, from where it is forwarded to the corresponding function SM of the serving node 3G-SGSN. The serving node 3G-SGSN negotiates with the radio resource management system RRM of the radio network controller RNC whether radio resources according to the capacity request are available. If there are sufficient resources, the serving node 3G-SGSN gives the radio resource management system RRM a resource allocation task, which consists in allocating the limited radio resources to the different radio bearers as optimally as possible. The radio resource management system RRM determines which radio resource parameters are optimal for using the application and defines the most suitable parameters for the radio bearer in terms of the available radio resource capacity. The radio resource management system RRM sends an indication to the radio resource control protocol RRC that performs the actual radio resource allocation. For applications requiring only unidirectional connections, all available capacity, e.g. xkbit/s, is typically allocated to one direction, typically the downlink direction, and no capacity, i.e. 0kbit/s, is allocated to the other direction, i.e. the uplink direction. If the terminal then tries or is forced to use a header compression algorithm requiring a bi-directional connection, the data transmission between the network and the terminal will be unsuccessful.

Now with the invention this can be avoided in such a way that the compression method for the radio link has been selected before the radio bearer is established and the information is sent to the radio resource management system RRM which takes into account the bi-directional compression algorithm that may be selected in the capacity allocation. In this case, the overall bandwidth allocated for the radio bearer can be optimized by taking into account the bandwidth required by the compression algorithm and the benefits deriving from using the compression algorithm as a smaller amount of data.

This can be illustrated by means of figure 4 showing the signalling of an embodiment of allocating capacity for a bi-directional connection. The PDCP layer of the user equipment UE supports at least one compression algorithm requiring a bi-directional connection. When a radio bearer is established, information (400) on the compression algorithm supported by the user equipment UE is sent to the radio resource control layer RRC of the radio network controller RNC in a UE-capacity message, for example, known per se. The radio network controller RNC decides (402) the compression algorithm used on the radio bearer and proposes (404) it to the radio resource management system RRM. In response to the application-based capacity allocation request, the radio resource management system RRM of the serving node 3G-SGSN and the radio network controller RNC negotiate whether there are sufficient radio resources as described above. The RRM allocates capacity for the radio bearers if sufficient radio resources are available in such a way that a bandwidth is defined that is as optimal as possible based on the application, but also takes into account possible limitations set by the compression algorithm. On the basis of these conditions, the RRM decides how to configure the radio resource controller RRC and informs the RRC of the configuration instructions (406). On the basis of this configuration, the RRC makes the final capacity allocation (408) for the radio bearer in question, which allocation also ensures that sufficient capacity is allocated for the reverse connection if necessary.

The above process can be illustrated using the following example. The end user wants to download a video file from the network and due to the application used to play the video file the data transmission rate required for the downlink is 100kbit/s and 0kbit/s in the uplink direction. On the basis of the UE-capacity message sent by the terminal, the radio resource controller RRC notices that the PDCP entities of the terminal and the base station support a header compression algorithm requiring a bi-directional connection according to the internet standard recommendation RFC 2507. The RRC selects the compression algorithm described for the radio bearer and proposes it to the radio resource management system RRM. Using the described compression algorithm requires a data transmission rate of, for example, 5kbit/s in the uplink direction. If the header portion of the overall data transmission is estimated to be 30kbit/s, e.g., (whereby the payload data portion is 70kbit/s) and the header portion after header compression is 10kbit/s, the data transmission rate in the downlink direction can be set to 80kbit/s, for example. In this way, the RRM set radio resource controller RRC is configured in such a way that 80kbit/s is allocated to the downlink and 5kbit/s to the uplink, thereby ensuring the operation of the desired compression method and that the 20kbit/s saved in the downlink direction with respect to the application based capacity allocation can be allocated to another user.

In the above, the invention has been described in connection with wireless packet switched data transmission, in particular in connection with radio resources of a UMTS system. However, the invention is not limited to wireless data transmission only, but can also be used in packet-switched data transmission by wire, using application-based data transmission capacity allocation packet switching. In an Internet Protocol (IP) based connection, such as a TCP (transmission control protocol) or UDP (user datagram protocol) connection, the possible header compression methods are indicated for the receiving party and data transmission resources are allocated for the terminal connection taking into account the capacity required for the header compression method in the allocated data transmission resources.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in many different ways. The invention and its embodiments are thus not limited to the examples described above but may vary within the scope of the claims.

Claims (16)

1. A method of allocating data transmission resources in a packet-switched telecommunications system comprising a terminal and a fixed network on which is defined an operable entity for defining resources for radio bearers for which radio bearer resources are defined on the basis of applications used by terminals on said radio bearers, characterized by

A method of compression of header fields in data packets for use on a radio bearer defined before resources are defined for the radio bearer, and

the resources of the radio bearer are defined in such a way that said resources also comprise the capacity required by the selected compression method of the header fields in the data packets.

2. A method as claimed in claim 1, characterized in that

Sending the compression method of the header field in the data packet supported by the terminal to the operational entity in the fixed network defining the compression method to be used.

3. A method as claimed in claim 1 or 2, characterized in that

Capacity in both directions is defined for the radio bearer in response to a selected compression method of a header field in a data packet requiring a bi-directional connection.

4. A method as claimed in claim 1 or 2, characterized in that

The packet switched telecommunications system is a UMTS system and the operable entities for defining resources for radio bearers include a radio resource control protocol RRC and a radio resource management system RRM.

5. A method as claimed in claim 4, characterized in that

Defining resources of said radio bearers in a radio resource management system RRM.

6. A method as claimed in claim 5, characterized in that

Sending the defined radio bearer resources to a radio resource control protocol, RRC, that allocates radio resources of the radio bearer.

7. A method as claimed in claim 4, characterized in that

The compression method of the header field in the data packets supported by the convergence protocol PDCP of the terminal UE is sent to the radio network controller RNC defining the compression method to be used.

8. A packet-switched telecommunications system comprising terminals and a fixed network comprising an operable entity for defining resources for radio bearers, in which system the resources of a radio bearer are arranged to be defined on the basis of applications used by the terminals on said radio bearer, characterized in that

The compression method of header fields in data packets used on a radio bearer is arranged to be defined before defining radio bearer resources, and

the radio bearer resources are arranged to be defined in such a way that the resources also comprise the capacity required for the selected compression method of the header fields in the data packets.

9. A telecommunication system as claimed in claim 8, characterized in that

The compression method of the header field in the data packets supported by the terminal is arranged to be transmitted to said operational entity of the fixed network defining the compression method to be used.

10. A telecommunication system as claimed in claim 8 or 9, characterized in that

The packet switched telecommunications system is a UMTS system and the operable entities for defining resources for radio bearers include a radio resource control protocol RRC and a radio resource management system RRM.

11. A network element for a packet-switched telecommunications system, the network element comprising an operable entity for defining resources for radio bearers, the network element being arranged to:

defining a compression method of a header field in a data packet for use on a radio bearer;

defining resources of the radio bearer based on an application used by a terminal on the radio bearer; and

the definition of the radio bearer resources is controlled according to the capacity required by the selected compression method of the header fields in the data packet.

12. The network element of claim 11, wherein the network element is further arranged to:

capacity in both directions is defined for the radio bearer in response to the selected compression method of the header field in the data packets requiring a bi-directional connection.

13. The network element of claim 11, wherein the network element comprises a radio resource control protocol and a radio resource management system as an operable entity to define resources for radio bearers.

14. A network element as claimed in claim 13, wherein the radio resource management system is arranged to define the resources of the radio bearers.

15. A network element as claimed in claim 14, wherein the radio resource management system is arranged to send the defined radio bearer resources to a radio resource control protocol which allocates radio resources of radio bearers.

16. A terminal for a packet switched telecommunications system, the terminal comprising an application capable of requesting radio bearer resources from a network of the packet switched telecommunications system, said terminal being arranged to:

transmitting information on a compression method of a header field in a data packet supported by the terminal to the network, an

The data transmission of said one application is performed according to a configuration of radio bearer resources defined by the network, whereby the definition of radio bearer resources is controlled according to the capacity required by the selected header field compression method.