RECEPTION OF DATA

The present invention relates to a method for controlling data transmission in a telecommunications network, as well as to a communication system, network node and user equipment suitable for use in such a method.

Communication networks typically operate in accordance with a given standard or specification which sets out what the various elements of the network are permitted to do and how that should be achieved. For example, the standard may define whether the user or more precisely, user equipment is provided with a circuit switched service or a packet switched service. The standard may also define the communication protocols which shall be used for the connection. The given standard also defines one or more of the required connection parameters. The connection parameters may relate to various features of the connection. The parameters may define features such as the maximum number of traffic channels, quality of service and so on or features that relate to multislot transmission.

In other words, the standard defines the "rules" and parameters on which the communication within the communication system can be based. Examples of the different standards and/or specifications include, without limiting to these, specifications such as GSM (Global System for Mobile communications) or various GSM based systems (such as GPRS: General Packet Radio Service), AMPS (American Mobile Phone System), DAMPS (Digital AMPS), WCDMA (Wideband Code Division Multiple Access) or CDMA in UMTS (Code Division Multiple Access in Universal Mobile Telecommunications System) and so on. The user equipment, i.e. a terminal that is to be used for communication over a particular communication network, has to be implemented in accordance with the predefined "rules" of the network.

A communication network is a cellular radio network consisting of cells. In most cases the cell can be defined as a certain area covered by one or several base transceiver stations (BTS) serving user equipment (UE) ₁ such as mobile stations (MS), via a radio interface and possibly connected to a base station subsystem (BSS). Several cells cover a larger area, and form typically a radio coverage area referred to as a location area (LA) or in some standards as a routing area (RA). It should be appreciated that the size of the location area or routing area depends on the system and circumstances, and may equal to one cell or be even smaller, such a part of a coverage area of a base station. A feature of the cellular system is that it provides mobility for the mobile stations, i.e. the mobile stations are enabled to move from a location area to another, and even from a network to another network that is compatible with the standard the mobile station is adapted to.

The user equipment (UE) within one of the cells of the cellular system can be controlled by a node providing controller function. Examples of the controller nodes include a base station controller (BSC) and a radio network controller (RNC). In UMTS the radio access network thereof is controlled by a radio network controller (RNC). The controller can be connected further to a gateway or linking node, for example a gateway GPRS support node (GGSN) or gateway mobile switching center (GMSC), linking the controller nodes to other parts of the communication system and/or to other communication networks, such as to a PSTN (Public Switched Telecommunications Network) or to a data network, such as to a X. 25 based network or to a TCP/IP (Transmission Control Protocol/Internet Protocol) based network. The network may also include nodes for storing information of mobile stations subscribing the networks or visiting the networks, such as appropriate home location registers (HLR) and visitor location registers (VLR).

When a user equipment communicates with a communication network, a communication path has been established between the user equipment and an

element or node of the network. The network node is typically one of the controller nodes. At least a part of the communication between the user equipment and the actual destination node will then pass through the controller node.

A communication system needs to be able to provide various different functions in order be able to operate. These functions can be divided in different categories. A category comprises functions that relate to the actual carrying of the communication such as voice or multimedia or other data content in the system. Another category can be seen as being formed by control or management functions such as the control of various services and the actual communication. Signalling of messages associated with different functions is thus understood as being implemented on different planes. For example, control messages are communicated on a control plane and the actual communication is then transported on a user plane. The communication on the user plane is supported the signalling of the control messages on the control plane.

Typically the communication systems provide this by means of separate channels, e.g. by means of separated signalling and communication channels. Such arrangements are employed e.g. by signalling system 7 (SS7) core networks and Q.931/GSM/WCDMA subscriber access. Therefore the term "Signalling channel" may be used when referring to control plane communications. Similarly the term communication channel may be used when referring to user plane communications.

The various functions of the communication systems may have been developed quite independently from each other and may use different protocols in different communication systems. The standards and protocols define e.g. which plane shall be used for a certain purpose.

In a third generation (3G) UMTS PMLN (3GPP UTRAN), various nodes including a BS (base station), RNC and SGSN (serving GPRS support node), may be involved in providing user and control plane communications to a mobile station. Examples of functions performed in such nodes include radio resource control (RRC), media access control (MAC) and packet data convergence protocol (PDCP). PDCP is used to format data into a suitable structure prior to transfer over the air interface. The main role of PDCP is header compression and decompression for packet data of a user connection.

In 3GPP UTRAN, RRC and PDCP functions are both located in the RNC (see Figure 1). The configuration of PDCP is controlled by RRC and the signaling of the configuration for PDCP between the network and a user equipment (UE) is done via RRC signaling. More specifically, the operation of PDCP header compression (HC) for a user connection, for example, is controlled by rather complex RRC radio bearer (RB) control procedures described in TS 25.331 UTRAN RRC protocol specification, Section 8.2. The "PDCP info IE" that can be included in the RRC RB setup or reconfiguration message to indicate which algorithms shall be established and to configure the parameters of each of the algorithms has the following format:

The ciphering in 3GPP UTRAN is controlled by RRC security mode procedures, see TS 25.331 Section 8.1.12, in a similar fashion to the RB control procedure.

However, certain access networks may be arranged differently such that different nodes perform these functions. For instance, in the proposed 3GPP Long Term Evolution (LTE) access scheme (otherwise known as 3GPP E-UTRAN), disclosed in 3GPP TR 23.882, there are only two user plane elements: an evolved Node B (eNB) and an access Gateway (aGW). When compared to e.g. 3G this means that RNC and SGSN user-planes are not used for 3GPP LTE access.

3GPP LTE is a packet-switched only access scheme, also known as "3.9G". At the same time 3GPP is also performing a feasibility study associated with streamlining the 3GPP PS network architecture to be used for LTE access.

In 3GPP LTE or E-UTRAN system, as shown in Figure 2 it has been agreed that the PDCP, including HC as its main function, and ciphering for the user-plane will be located in an aGW and RRC will be located in an eNB (sometimes referred to as a BS). However, no convenient method has been provided for configuring PDCP in such an environment.

Embodiments of the present invention aim to address one or more of these problems.

According to one embodiment of the present invention, there is provided a method for controlling data transmission in a telecommunications network, comprising transmitting control information between a network node and a user equipment, wherein the control information is associated with configuration of a data packaging protocol used for communication between the network node and the user equipment, and the control information is transmitted using the data packaging protocol.

According to another embodiment of the present invention, there is provided a network node configured to transmit control information towards a user equipment, wherein the control information is associated with configuration of a data packaging protocol used for communication between the network node and the user equipment, and the network node is configured to generate and/or transmit the control information using the data packaging protocol.

According to another embodiment of the present invention, there is provided a user equipment configured to receive control information from a network node, wherein the control information is associated with configuration of a data packaging protocol used for communication between the network node and the user equipment, and the user equipment is configured to receive the control information via the data packaging protocol.

According to another embodiment of the present invention, there is provided a communication system comprising a network node and a user equipment, wherein the network node is configured to transmit control information towards the user equipment, the control information being associated with configuration of a data packaging protocol used for communication between the network node and the user equipment, the network node is configured to generate and/or transmit the control information using the data packaging protocol, and the user equipment is configured to receive the control information from the network node via the data packaging protocol.

According to another embodiment of the present invention, there is provided a network node comprising means for transmitting control information towards a user equipment, wherein the control information is associated with configuration of a data packaging protocol used for communication between the network node and the user equipment, and the network node comprises means for generating and/or transmitting the control information using the data packaging protocol.

Preferably the data packaging protocol formats or ciphers packet data, for example performs data unit header compression and/or decompression, or data ciphering, and is most preferably a packet data converge protocol. The data packaging protocol may be used for user plane communication between the network node and user equipment.

Preferably the control information defines a data unit header compression configuration for use in the data packaging protocol. In an alternative embodiment, the control information defines a ciphering configuration.

Preferably the control information is transmitted in a data packet generated by a data packaging function in the network node. More preferably, the data packet is a control protocol data unit comprising a payload and a header, the payload

comprising the control information and the header comprising configuration type information defining the type of control information comprised in the payload.

In one preferred embodiment, user (plane) data is transmitted between the network node and the user equipment in user protocol data units, each user protocol data unit including a header and a payload comprising the user data, and wherein the header of each control or user protocol data unit further comprises information defining whether the protocol data unit comprises control information or user data.

Preferably the network node is an access gateway, e.g. aGW of a 3GPP E- UTRAN.

The method preferably further comprises a step of sending an acknowledgement of receipt of the control information, e.g. from the user equipment to the network node after the user equipment has received the control information from the network node. User plane data is preferably communicated between the network node and user equipment only following receipt of the acknowledgement.

The method preferably further comprises setting a timer, e.g. in the network node, when sending the control information. In a preferred embodiment, the control information is resent if the timer expires before an acknowledgement of receipt of the control information is received.

Embodiments of the present invention may advantageously provide an efficient method for communicating configuration information concerning a data packaging protocol such as PDCP between a network node and a user equipment. The method uses the data packaging protocol signaling itself to transmit the control information, rather than for example using a dedicated control plane signaling protocol such as RRC to configure the PDCP. This results in a simpler and more convenient method for configuring the data

packaging protocol than would otherwise be the case, especially in a communication system where the PDCP and RRC functions are located in different nodes (e.g. as in a 3GPP E-UTRAN). For instance, if communication of PDCP configuration is done via RRC signalling, the signalling path will be first from aGW to BS (eNB), then from BS back to aGW, then from aGW to UE via BS. Alternatively an upper layer RRC would need to be defined in aGW.

Both of these alternative solutions would make the system more complicated. Embodiments of the present invention may release the RRC signalling burden for configuring PDCP header compression and ciphering configuration. Moreover, no RRC upper part layer is needed in aGW for this purpose, which simplifies the radio interface protocol.

For better understanding of the present invention, reference will now be made by way of example to the accompanying drawings in which:

Figure 1 shows some element of a 3G UTRAN network;

Figure 2 shows some elements of a 3GPP E-UTRAN network in which embodiments of the present invention may be implemented;

Figure 3 shows a control packet data unit according to one embodiment of the present invention.

Figure 4 shows the main signaling sequences according to one embodiment of the invention.

Reference is made to Figure 2 which illustrates a context in which the present invention may be used, i.e. a cellular telecommunication system providing a packet switched service. The communications system comprises a 3GPP LTE access network, only selected parts of which are shown.

The mobile communication system allows a mobile station MS (or user equipment UE) to communicate with an evolved node B (eNB) or base (transceiver) station (BS) via a wireless connections. Each base station has a radio transceiver capable of transmitting radio signals in downlink (DL) to the mobile stations within the cell area and receiving radio signals in uplink (UL) from the cell area next to the base station. By means of these signals the base station can communicate with the mobile station (MS) in that cell, which itself includes a radio transceiver.

Data to be transmitted from and to the user equipment, which comprise mobile stations, may be speech data, video data or other data. Any packet data transmission may be encoded into a form suitable for transmission at a bit rate which is dependent on the application and the source of the data.

The eNB is connected to an access gateway (aGW). Thus, during a connection, a mobile station (MS) may communicate with an access gateway via the eNB. The eNB may be connected to one or more further nodes of the cellular network, for example a controller node or a Mobility Management Entity (MME) such as an evolved SGSN (e-GSN-c). The eGSN-c operates in the control plane only, and thus does not provide user plane functions.

The mobile node or mobile station MS may be a user equipment such as a dual- or multi-mode mobile station, that may communicate via the eNB of the 3GPP LTE system. The location of the mobile station could be fixed (for example if it is providing radio communications for a fixed site) or the MS could be moveable (for example if it is a hand portable transceiver or "mobile phone"). When the mobile station is moveable it may move between cells of the cellular radio system.

The packet data service may be a connectionless service where information symbols are transmitted within data packets. The size and length of the data

packets may vary. The information symbols are typically carried by means of packet data bearers. The transmission speed of a bearer is defined by a parameter referred to as bitrate. More particularly, bitrate defines the bit rate that has been allocated for a user of the packet data services. Packet data traffic may include various kinds of data transmission, such as voice over IP (VoIP), short messages or text only emails and transmission of large documents in the background and interactive browsing of the world wide web (WWW).

The dual- or multi-mode mobile station may consist of a Mobile Equipment (ME), and one or more Subscriber Identity Modules (SIMs). The mobile equipment ME is the radio terminal used for radio communication over the interface between the user equipment and the eNB. The SIM is typically a smart card that holds the subscriber identity, performs authentication algorithms, and stores authentication and encryption keys and some subscription information that is needed at the terminal. These SIM functions may me implemented by one or two cards, depending on the application.

The aGW may communicate with the UE, e.g. via user plane signaling, by preparing data packets (protocol data units, D-PDU) using PDCP. The data packets are sent to the UE via the eNB. According to embodiments of the present invention, PDCP control protocol data units (C-PDU) are used to control and communicate the configuration of PDCP between the aGW and the UE. The lower layers (MAC and physical layer, located in the eNB) are not aware of the C-PDU. They handle the C-PDU in the same way as normal PDCP Data PDU (D-PDU).

PDCP C-PDU consists of the PDU header and the control payload. The structure of C-PDU is shown in Figure 3.

Here D/C is a one-bit field which indicates the PDU is a C-PDU or a D-PDU. C- PDU Type field indicates the type of C-PDU (e.g. a type which controls the

configuration of header compression, or a type which controls the configuration of ciphering etc.). The table below gives an example of the C-PDU contents. The C-PDU type field can be extended further for more control functions.

Table 1 An Example of C-PDU Contents

In a preferred embodiment, the header of PDCP D-PDUs also includes a D/C field, in order to distinguish PDCP C-PDU and D-PDU.

The transmission of PDCP C-PDU between the aGW and UE should be reliable enough to make sure that the configuration information has been successfully communicated between aGW and UE before the D-PDU is received by the receiver. Accordingly, in a preferred embodiment, a timer mechanism is used for acknowledgement of C-PDU reception.

The main signalling sequences for one such embodiment are shown in Figure 4. The transmitter, e.g. the aGW, sends a C-PDU to the receiver, e.g. the UE. At the same time as sending the PDCP C-PDU, the aGW starts a timer to wait for ACK from the receiver, .i.e. the UE. PDCP of the receiver responds by sending an acknowledgement (ACK) to the transmitter after receiving each PDCP C- PDU. If the timer expires before the transmitter receives the ACK, the transmitter

resends the C-PDU again. Once the transmitter (aGW) receives the ACK, it starts sending D-PDUs, comprising e.g. user plane data, to the receiver (UE).

It should be appreciated that whilst embodiments of the present invention have been described in relation to mobile stations, embodiments of the present invention are applicable to any other suitable type of user equipment.

The embodiments of the invention have discussed communication between an aGW and a user equipment. Embodiments of the present invention may also be applicable to communication between a user equipment and other network elements in certain cases.

It is also noted herein that while the above describes exemplifying embodiments of the invention, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention as defined in the appended claims.