HK1094999B

HK1094999B - Data signaling method and communications unit for message-based communication

Info

Publication number: HK1094999B
Application number: HK07102181.8A
Authority: HK
Inventors: Hans Hannu; Jan Christoffersson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2003-04-01
Filing date: 2004-03-26
Publication date: 2011-08-05

Description

Data signaling method and communication unit for message-based communication

Technical Field

The present invention relates generally to data signaling in data communication systems, and more particularly to message-based data signaling for state-mediated data in such systems.

Background

Today, the trend of data communication between communication units in different data communication systems is increasing. Typical examples are data communication between computers connected via a communication system such as the internet or a local area network, or data communication between a mobile user equipment and a communication server or node or another mobile user equipment in a radio communication system.

Many application protocols used in data communications require that certain information and data be included in data messages transmitted over the communication system. This data may be required for efficient delivery of data messages throughout the system and/or may be used by the receiving communication unit for interpreting and processing received data messages. Thus, many communicated data messages contain fields that always include more or less the same data for a given pair or combination of communication units. This is generally not a problem for communication systems having bandwidth rich communication links. However, in radio communication systems and other systems, which typically have limited available communication resources, it is generally desirable to reduce the amount of data that must be communicated between communication units.

In addition, multimedia data messages are typically designed for bandwidth rich links. Today, multimedia services employing such multimedia messages are also present in radio communication systems which often have links with poor bandwidth. A problem therefore arises because multimedia messages are not optimized with respect to the size of such radio communication systems. For example, typical Session Initiation Protocol (SIP) messages range from a few hundred bytes to two kilobytes or more. Using these protocols in wireless mobile units that are part of a radio communications network, large message sizes are problematic. Under low rate Internet Protocol (IP) connections, transmission delays are significant. Call setup and function invocation are adversely affected in view of retransmissions and the required repeatability in some flows.

One possible solution is therefore to employ a compression algorithm to compress the transmitted (multimedia) data messages, thereby reducing the amount of data that has to be transmitted for each such message.

There are several different described compression techniques that may be used for data compression in e.g. mobile communication systems. A typical example is signal compression SigComp, which has been recently developed and is further described in request for comments (RFC) document [1, 2 ]. SigComp is a compression solution for compressing data messages generated by application protocols such as SIP, Session Description Protocol (SDP), and Real Time Streaming Protocol (RTSP), and provides a robust lossless compression for such application messages.

However, even data messages compressed by SigComp and other compression protocols still contain some information fields that generally always contain the same data for a given pair of communication units. Although compression techniques reduce the overall size of data messages transmitted over a communication system, there remains the problem of limited available communication resources, particularly for radio communication systems and other bandwidth-poor systems. Therefore, there is a need to further reduce the size of transmitted data messages and compressed data messages.

Disclosure of Invention

The present invention overcomes these and other shortcomings of the prior art arrangements.

It is a general object of the present invention to provide data signaling that reduces the use of communication resources for inter-unit data communication.

It is a further object of the present invention to provide message-based data signaling that reduces the size of data messages transmitted between communication units.

It is a further object of the present invention to provide a data signaling for status mediation in a communication system.

These and other objects are met by the invention as defined in the appended patent claims.

The invention provides a data signaling method for message-based communication between a first communication unit and a second communication unit, comprising the steps of:

-initiating message-based communication between the first communication unit and the second communication unit by providing a status in the first communication unit), the status) comprising communication unit-related data applicable to a plurality of communication messages to be transmitted between the first communication unit and the second communication unit;

-the first communication unit generating a copy of the state;

-sending the state copy and the first identifier of the state copy from the first communication unit to the second communication unit;

-the second communication unit generating a second identifier based on the received state copy;

-the second communication unit comparing the received first identifier with the generated second identifier;

-storing the state copy in the second communication unit; and

-processing the first communication message or the second communication message with the state or the state copy by resizing the first communication message or the second communication message of the plurality of communication messages in dependence on at least a part of the communication unit related data if the second identifier corresponds to the first identifier,

the method is characterized in that: the processing steps comprise the following steps:

-the first communication unit removing at least a part of the communication unit related data in the state from the first communication message to obtain a first reduced size communication message;

-the first communication unit sending a first size reduced communication message to the second communication unit; and

-the second communication unit adding at least a part of the communication unit related data in the state copy to the first reduced size communication message to obtain the first communication message.

The processing step may include the steps of:

-the second communications unit removing at least a part of the communications unit related data in the state copy from the second communications message to obtain a second reduced size communications message; and

-the second communication unit sending the second size reduced communication message to the first communication unit.

The data signaling method may further include the steps of: the first communication unit adds at least a portion of the communication unit related data in the state to the second reduced size communication message to obtain a second communication message.

The storing step may include the steps of: if the second identifier corresponds to the first identifier, the state copy is stored at the second communication unit in a partition dedicated to the first communication unit.

The data signaling method may further include the steps of: the state copy is copied at the second communications unit from the partition dedicated to the first communications unit into the local available state memory of the second communications unit.

The data signaling method may further include the steps of: the state is stored in a locally available state memory of the first communication unit.

The message-based communication between the first communication unit and the second communication unit may comprise a compressed message-based communication between the first and second communication units, wherein the first communication unit compresses the first communication message according to the state before the first communication unit removes at least a portion of the communication unit-related data in the state from the first communication message to obtain the first reduced-size communication message, and the second communication unit decompresses the compressed first communication message according to the state copy after the second communication unit adds at least a portion of the communication unit-related data in the state copy to the first reduced-size communication message.

The message-based communication between the first communication unit and the second communication unit may include compressed message-based communication between the first and second communication units, wherein the second communication unit compresses the second communication message according to the state copy before the second communication unit removes at least a portion of the communication unit-related data in the state copy from the second communication message to obtain the second reduced-size communication message, and the first communication unit decompresses the compressed second communication message according to the state after the first communication unit adds at least a portion of the communication unit-related data in the state to the second reduced-size communication message.

The plurality of communication messages (m1, m2) may be compressed using SigComp compression.

The data signaling method may further include the steps of:

-the second communication unit receiving an acknowledgement identifier from the first communication unit; and

-if the second identifier corresponds to the first identifier, the second communication unit returns an acknowledgement identifier to the first communication unit.

The present invention also provides a communication unit adapted for message-based communication with an external communication unit, comprising:

-means for receiving a copy of a state, the state comprising communication unit related data, applicable to a plurality of communication messages to be transmitted between a communication unit adapted for message based communication with an external communication unit and the external communication unit;

means for receiving a first identifier of a state copy;

means for generating a second identifier based on the received state copy;

a comparison component for comparing the received first identifier and the generated second identifier;

a storage component for storing a copy of the state; and

processing means, responsive to the comparing means, for processing a communication message of the plurality of communication messages using the stored state copy when the second identifier corresponds to the first identifier, the processing means being configured to resize the communication message in dependence on at least a part of the communication unit related data in the state copy,

the method is characterized in that: the communication message is a reduced size communication message and the processing means comprises adding means for adding at least part of the communication unit related data in the state copy to the reduced size communication message.

The processing means may be replaced by a compressor and a decompressor, and the adding means is provided in the decompressor for adding at least a part of the communication unit related data in the state copy to a compressed communication message received from the external communication unit with at least a part of the communication unit related data in the state removed.

The processing means may comprise removing means for removing at least a part of the communication unit related data in the state copy from the communication message.

The processing means may be replaced by a compressor and a decompressor, and the removing means may be provided in the compressor for compressing the communication message by removing at least a part of the communication unit related data in the state copy from the communication message to be sent to the external communication unit.

The compressor and decompressor may be configured to compress and decompress signals using SigComp protocol.

The comparison component may be configured to generate the storage command when the second identifier corresponds to the first identifier, and the storage component may be configured to store the state copy when the storage command is received.

The storage means may be configured to store the state copy in a partition dedicated to the external communication unit.

The communication unit adapted for message-based communication with an external communication unit may further comprise: means for copying the state copy from the partition dedicated to the external communication unit into the locally available state memory.

The communication unit adapted to perform message-based communication with the external communication unit may further comprise means for sending a confirmation identifier to the external communication unit when the second identifier corresponds to the first identifier in response to the comparing means.

-means for generating a status comprising communication unit related data applicable to a plurality of communication messages to be transmitted between a communication unit adapted for message based communication with an external communication unit and the external communication unit;

-means for storing a status;

-means for generating a copy of the state;

-means for providing a state copy for storage in the external communication unit and for providing a first identifier of the state copy to the external communication unit;

-receiving means for receiving an acknowledgement identifier from the external communication unit, the acknowledgement identifier being sent in response to a correspondence between a second identifier and the first identifier, the second identifier being generated by the external communication unit from the state copy; and

-processing means, responsive to the receiving means, for processing a communication message of the plurality of communication messages using the stored state upon determining by receiving the confirmation identifier that the second identifier corresponds to the first identifier, the processing means being configured to resize the communication message in dependence on at least a part of the communication unit related data in the state,

the method is characterized in that: the processing means comprises removing means for removing at least a part of the communication unit related data in the state from the communication message.

The processing means may be replaced by a compressor and a decompressor, and the removing means may be provided in the compressor for compressing the communication message by removing at least a part of the communication unit related data in a state from the communication message to be sent to the external communication unit.

The communication message may be a reduced size communication message and the processing means may comprise adding means for adding at least a part of the communication unit related data in the state to the reduced size communication message.

The processing means may be replaced by a compressor and a decompressor and the adding means may be provided in the decompressor for adding at least a part of the communication unit related data in the state to a compressed communication message received from the external communication unit with at least a part of the communication unit related data in the state copy removed.

Briefly, the present invention relates to message-based data signaling for state brokering in a communication system. A state comprising communication unit related data and being applicable to a plurality of data messages to be transmitted between at least two communication units is generated and used for data communication between the units.

The invention is based on the following facts: some fields in the transmitted message typically more or less often include the same information and data for a particular communication unit pair or combination. Thus, this same data of a message is sent over and over again between the communication units. The present invention provides a scheme for efficient communication between units without the need for retransmission of certain data, which thus allows for reduced message size and reduced communication resource usage.

Thus, a first communication unit, which is to communicate with a second external communication unit, generates a state comprising data or information related to the first unit. This state data is typically used for efficient processing and/or interpretation of the data message, but is not necessary for sending the data message to an external unit. The communication unit related data typically comprises device specific data parts including, for example, capabilities and settings of the unit related to communication and sessions, and/or user specific parts including, for example, a Uniform Resource Locator (URL), a name, an e-mail address, etc. of the user of the communication unit. This state is then stored in a state memory provided in the cell. In addition, a copy of the state is generated and sent to the second communications unit, where it is stored in the corresponding state memory.

Since both communication units now have access to the data in the state and state copy, they can use this data to process messages to be passed between them in order to reduce the message size and thereby save communication resources.

For example, an application message generated in the first communication unit and to be transmitted to a certain application in the second unit is processed with the state stored in the first unit. During this message processing, data contained in the state and found in the message, typically in the message header, is removed from the message prior to sending the message. The resulting reduced size message is then sent to the external second communication unit. There, the number in the state copy is used

In addition to sending the state copy to the second communications unit, the first unit preferably generates the state copy identifier, for example as a hash function value of data in at least a part of the state/state copy. This identifier is then transmitted to the second unit, preferably in a list containing state information available to the first unit. Alternatively, the first communications unit sends some data that allows the calculation of the identifier in the second unit. Once the second unit receives the identifier or data allowing the calculation of the identifier and the state copy, it calculates a second state copy identifier. This calculated identifier is then compared with the identifier received from the first unit. If they match, the state copy is deemed to have been successfully provided and may be stored in the second unit. When the second unit determines that the two identifiers match, it can conclude that the state is present in the first communications unit and it can process the message to be sent to the first unit using the stored state copy.

The second communications unit may also acknowledge successful receipt of the state copy of the first unit. In this case, acknowledgement information, such as a dedicated acknowledgement identifier or state copy identifier received from the first unit, is returned or transmitted to the first communication unit. Alternatively, the second communications unit processes the message to be sent to the first unit using the state copy. The first communications unit may then deduce that the second unit has received the state copy because this copy has already been used to process the now received message.

The teachings of the present invention can be advantageously applied to message compression. In this case, the state or state copy is used during compression in order to reduce the size of the resulting compressed message by removing communication unit related data from the message. Accordingly, during decompression, the state or state copy is used to re-input the omitted data and reconstruct the original uncompressed data message. SigComp protocol is a typical example of a protocol that may be used for such a message compression scheme.

The present invention is advantageously applied to communication systems having a limited amount of communication resources and bandwidth-poor links, where it is generally desirable to reduce the size of communication messages. Typical examples are radio communication systems such as global system for mobile communications (GSM), General Packet Radio Service (GPRS), Enhanced GPRS (EGPRS), enhanced data rates for GSM evolution (EDGE), Universal Mobile Telecommunications System (UMTS) and different Code Division Multiple Access (CDMA) communication systems, but other communication systems such as local area networks can also benefit from the present invention.

The present invention provides the following advantages:

-allowing a reduction of the size of data and application messages transmitted between communication units in the communication system;

-saving communication resources by reducing the amount of resources used for inter-unit communication;

-adaptable to different compression techniques in order to enhance the compression and decompression of messages; and

it is applicable to different types of data and application messages.

Other advantages offered by the present invention will be appreciated upon reading the following description of embodiments of the invention.

Drawings

The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

fig. 1 schematically shows a schematic overview of a communication system according to the present invention, exemplified by a radio communication system, which provides push-to-talk (PTT) services to connected subscriber communication units.

Fig. 2 schematically shows typical data contained in a state according to the invention.

Fig. 3 is a block diagram of an embodiment of a communication unit according to the present invention.

Fig. 4 is a block diagram of another embodiment of a communication unit according to the present invention.

Fig. 5 is a block diagram showing the state processor of fig. 3 and 4 in more detail.

Fig. 6 is a diagrammatic view of the state memory of fig. 3 and 4.

Fig. 7 is a signal diagram illustrating a data signaling method according to the present invention.

Fig. 8 is a block diagram of another embodiment of a communication unit according to the present invention.

Fig. 9 is a flowchart illustrating a data signaling method according to the present invention.

FIG. 10 is a flow chart showing additional steps of the data signaling method of FIG. 9;

FIG. 11 is a flow chart showing additional steps of the data signaling method of FIG. 9;

FIG. 12 is a flow chart showing additional steps of the data signaling method of FIG. 9; and

fig. 13 is a flow chart showing the message processing steps of fig. 9 in more detail.

Detailed Description

The same reference numbers will be used throughout the drawings to refer to corresponding or similar elements.

The present invention relates generally to message-based data signaling between communication units in a communication system. The present invention aims to reduce the size of transmitted data messages, and to this end the use of communication resources in the system is reduced by introducing state mediated data signalling.

The present invention is based on the following observations: certain fields in the transmitted message typically more or less often include the same information and data for a particular pair or combination of communication units. Thus, this same data is sent over and over again between the communication units. The present invention provides a scheme for achieving efficient communication between units without retransmitting certain data, thereby achieving a reduction in message size and a reduction in communication resource usage.

According to the invention, a state is generated in one of the communication units comprising such data or information that is suitable for, i.e. common to, a plurality of data messages. Then, a solution is proposed to provide a copy of this state to an external communication unit to which data messages are to be sent and/or from which data messages are received. Since these communication units will then have access to the above-mentioned state or a copy thereof, the corresponding data in the state can be omitted from the transmitted messages, so that the overall size of the messages sent between the units, i.e. in both directions, is reduced.

In the following, the invention will be described and disclosed with reference to a radio communication system providing communication services to connected mobile units. The present invention is not so limited and is applicable to other communication systems in which units communicate message-based data. A typical example would be one computer communicating with another computer or a server over a local area network or the internet. However, the present invention is advantageously applied to communication systems having a limited amount of communication resources and bandwidth-poor links, where the general need to reduce the size of communication messages is particularly apparent. Typical examples are radio communication systems such as global system for mobile communications (GSM), General Packet Radio Service (GPRS), enhanced GPRS (egprs), enhanced data rates for GSM evolution (EDGE), Universal Mobile Telecommunications System (UMTS), and various Code Division Multiple Access (CDMA) communication systems.

Fig. 1 shows an example of a radio communication system, illustrated as a cellular communication system 1, which provides push-to-talk (PTT) services for connected communication units 100-1 to 100-4.

In addition to having a typical network architecture comprising a plurality of base station systems BSS a1, BSS a2, BSS B including base transceiver stations or node bs BTS a1, BTSA2, BTS B, respectively, and core networks CN a, CN B, the radio communication system 1 further comprises an IP Multimedia Subsystem (IMS)250 having a PTT server 200. This PTT server 200 typically handles call setup signaling for PTT calls as well as flow control for PTT traffic. Furthermore, the routing of IP packets carrying voice data to the correct receiving user equipment 100-2, 100-3, 100-4 in real time is managed by the PTT server 200.

In this figure, four PTT supporting user handsets or devices 100-1 through 100-4 are shown. The user devices 100-1 to 100-4 comprise PIT clients implemented therein and are equipped with PTT hardware or software buttons for performing push-to-talk sessions. The users (owners) of the devices 100-1 to 100-4 typically have a service agreement, such as a subscription agreement, with a PTT service provider, often a network operator. The user equipments 100-1 to 100-3 may be (conventional) mobile units or telephones equipped with PTT clients. A computer or laptop connected to the PTT server 200 via, for example, the internet is also possible.

In a PTT session, a first user wishes to communicate with one (one-to-one communication) or several (one-to-many) other users through a PTT communication. The user typically selects a friend to contact from the address book or PTT book in his communication unit 100-1. This address book preferably also informs the user, i.e. provides him with presence information of which of his friends are currently connected to the communication system 1 and can thus participate in the PTT session. The user then presses a PTT button on his unit 100-1. This PTT key may be a hardware key in unit 100-1 or a key implemented in software. When the key is pressed, session establishment signaling is initiated. When the initial set-up is over, the user can start talking with his friends, i.e. the talk burst starts. When the user releases the button, or presses the PTT stop button, the talk burst ends. During this talk burst, i.e., speech, the talk (speech) is sampled, speech encoded and grouped into a plurality of data packets, typically adaptive multi-rate (AMR) packets or frames, as is known in the art. The AMR packets or frames are encapsulated into IP packets before being transmitted via the radio communication system 1 to the friend's communication units 100-2 to 100-4. The actual number of AMR packets per IP packet typically depends on the acceptable overhead level, the IP version used, and/or the header compression. Furthermore, the real-time transport protocol (RTP) is preferably used in GPRS access networks and core networks. Then, the transmitted IP packet is transmitted from the user equipment 100-1 to the PTT server 200 via the base station BSA 1, the base station system BSS a1, and the core network CNA. The server then routes the packet to the intended communication unit 100-2 to 100-4.

Although the PTT server 200 has been shown in the figure as one communication endpoint communicating with the user equipment 100-1 as the other endpoint, a dedicated communication function, a proxy call session control function (P-CSCF), is typically arranged in the IMS server 250 for receiving and sending messages on behalf of the PTT server 200 and other IMS service nodes. These two communication endpoints can then be considered as this P-CSCF and the user equipment.

In PTT services and other IMS services, the communication units communicate using Session Initiation Protocol (SIP), Session Description Protocol (SDP), Real Time Streaming Protocol (RTSP), and other application protocol messages. Such messages typically comprise data field data (always) filled with the same data. This means that the plurality of messages sent from the first communication unit and the predetermined communication unit comprise a first part of data, which is typically provided in the header of the message, common to the plurality of messages, and a second part of data, which is typically the payload part and some of the data in the header that differs from message to message. Such common so-called communication unit or user-related data is typically used in the communication unit for efficient processing and/or interpretation of data messages. Take SIP as an example. The capabilities and settings of the SIP-enabled communication unit are communicated during session initiation and often do not change unless the capabilities of the device change. Similarly, user-specific information such as a user's Uniform Resource Locator (URL), name, and email address, etc. are likely not to change frequently and will appear regularly in SIP signaling involving a particular user.

According to the invention, a state is generated which comprises communication unit related data common to a plurality of data messages to be transmitted or at least a part of the communication unit related data. This state 10 is schematically shown in fig. 2. As briefly mentioned above, the communication unit related data and thus the status preferably comprises a user specific data part 12(URL, email address, name, etc.) and/or a device specific data part 14 (device capabilities, settings, SDP settings, SIP settings, RTSP settings, etc.). By allowing both communicating units to have access to data in state 10, this data can be omitted from messages transmitted between the units to reduce message size and increase the efficiency of the message flow. Since the units participating in the communication have access to the state 10, they are able to successfully process and interpret any messages received.

Fig. 3 shows a block diagram of a communication unit 100 according to the invention. The unit 100 may be a user device such as a mobile unit, a mobile phone, a Personal Digital Assistant (PDA) or a computer. Further, a SIP, SDP, RTSP or other application protocol server may also be the communication unit 100 according to the present invention. Other non-limiting examples of communication units 100 are PTT servers and other IMS servers, such as P-CSCFs provided in servers or in network nodes of the communication system.

The communication unit 100 typically comprises an input and output (I/O) unit 110 for communicating with external units in the communication system. In particular, this I/O unit 110 is particularly adapted to receive data messages from or to send data messages to, respectively, external units. Furthermore, to improve data communication efficiency, the transmission of state and the reception of state copies is managed by the I/O unit 110.

The communication unit 100 further comprises an application 150, which schematically represents the functionality in the unit 100 to generate messages to be transmitted to external units and to process messages received from said external units. For example, for a PTT-enabled communication unit 100, the application may manage voice sampling, voice encoding, and grouping into data packets, which in turn may be combined into data messages. Accordingly, when the communication unit 100 receives a message comprising PTT data, the application 150 may be adapted to decapsulate the data therein and reconstruct the speech to be played back for the user of the unit 100.

A status handler 140 is provided in the communication unit 100 according to the invention for managing the status including communication unit related data. The state handler 140 is preferably configured to generate a state to be used in message-based communication with the external unit. Alternatively, the state may be generated elsewhere in the unit 100, for example in the application 150. The state handler 140 may be adapted to generate a state from the application 150 that is associated with the communication unit 100 and is applicable to a plurality of messages. This state is then provided to one or more external units with which unit 100 wishes to communicate. Alternatively, a dedicated state is generated and supplied to each external communication unit. In this case, the communication unit 100 will have access to several states, wherein a given state is used for communication with a specific external unit or a specific group of external units. Once the state has been generated by the state handler 140 or some other component in the unit 100, the state handler 140 stores it in an associated state memory 160 provided in the unit 100. Alternatively, the state memory 160 may be located elsewhere as long as the communication unit 100 has access to the data therein.

The state handler 140 is also configured to create a copy of the generated and stored state. This state copy is then sent via the I/O unit 110 to an external unit with which the communication unit 100 is to engage in message-based communication. Accordingly, if the communication unit 100 receives a state copy generated by an external unit, the I/O unit 110 forwards the received state copy to the state handler 140, which stores the state copy in the memory 160.

For a given pair or combination of communication units, the state may be generated on a per-session basis. Thus, the state is only used during a given session to process the transmitted messages. When the session ends, the state and state copy may be deleted from the state store 160. Alternatively, it is possible that the data in the state and state copy are applicable to messages in several different communication sessions with the external unit. Thus, when the session ends, the state/copy will still remain in the state memory 160. However, once the data contained in the state changes, for example due to a change in the settings or capabilities of the communication unit 100, a new copy of the state is preferably generated and sent to the external unit, which then updates the associated state memory 160.

For example, if the communication unit 100 is a mobile unit that is engaged in a PTT communication with other units via a PTT server, the status memory 160 preferably includes a status that includes data associated with the mobile unit. A copy of this state is preferably provided to the IMS server, typically to the P-CSCF functionality in the server. This P-CSCF function typically acts as a communication interface for the IMS server and its included nodes, such as PTT servers, to the mobile unit. The mobile unit 100 and the server may then communicate messages between each other using the states and state copies in an efficient and resource-saving manner. The mobile unit 100 may also include a state copy in the memory 160, where this state copy is generated by and includes data associated with the P-CSCF function. The mobile unit related state and state copy and the IMS related state and state copy are then available for message based communication.

Accordingly, the IMS server (P-CSCF function) preferably includes a state copy of some or all of the mobile units with which it communicates. The server then uses the first state copy to generate messages to be sent to the first mobile unit and/or to process messages received from the first unit. The second state copy is used for messages relating to the second mobile unit and so on.

As described above, if the communication unit 100 has sent a copy of the state to an external communication unit, it may omit the data contained in the state, or at least a part thereof, from the message generated by the application 150 to be sent to the external unit. In this case, the application 150 may be configured to omit this data in the state during message generation. Alternatively, the message processor 130 receives the original message from the application 150 and includes functionality 134 for removing data found in the state from the message, typically from the header of the message. The size of such a processed message is then smaller than the size of the corresponding original message. This reduced size message is then forwarded to the I/O unit 110 and sent to the external unit.

When the I/O unit 110 receives a size reduction message from an external unit, it informs the state handler 140 to provide data from its state or state copy associated with and previously received from the external unit. The message and state copy data are provided to a message handler 130. the message handler 130 includes functionality 132 for entering the data or at least a portion thereof in the state copy into a "missing or empty" data field (typically its header) in the received message. The resulting original version of the message is then forwarded to the application 150, and the application 150 can now successfully process the message after the missing data is added.

The data in the state and state copy of the invention is thus applicable to a plurality of messages to be sent to the external communication unit, i.e. the data is present in (all) of these messages and is typically required for message processing and interpretation in the external communication unit, but is typically not necessary for successful delivery of the message. This data is then omitted or removed from the message using the state/state copy prior to transmission of the message. Furthermore, before processing the received message in the receiving unit, the omitted or removed data is added to the message using the state copy/state, resulting in a message that can be successfully processed in the application.

The communication unit 100 may be provided with a state handler 140 configured to generate states and utilize these states in message processing. In an alternative embodiment, the state handler 140 does not generate the state itself, but is configured to utilize a copy of the state received from an external unit. In another embodiment, the state handler 140 may perform both functions, i.e., message processing with its own generated state and a received state copy.

Furthermore, if the communication unit 100 is implemented to substantially only send messages to external units, without receiving messages therefrom, the message processor 130 may be implemented to include only the state data deletion or removal function 134. Accordingly, if the communication unit 100 is expected to primarily only receive messages from external units, rather than transmit them, the message processor 130 may include the state data addition function 132, but not the state data deleter 134. However, in a preferred embodiment, the message processor 130 may include both message size adjustment components 132, 134.

The units 110, 130, 132, 134, 140 and 150 of the communication unit 100 may be provided as software, hardware or a combination thereof. Units 110, 130, 132, 134, 140, 150, and 160 may be implemented together in communication unit 100. Alternatively, especially for server-implemented embodiments of the communication units in the communication system, distributed implementations are also possible, where some units are located in different network nodes.

The teachings of the present invention are also applicable to compressed message-based communication between communication units. Thus, the data in the generated state and state copy may also or alternatively be used during compression and/or decompression of data messages. In this case, the state and state copy desirably improves message compression by allowing the message size to be reduced after compression, as compared to a compressed message that does not utilize the state of the present invention.

Fig. 4 is a schematic block diagram of a communication unit 100 adapted for compressed message based communication according to the present invention.

The communication unit 100 comprises a compressor 120 adapted to compress messages from the application 150 using the state provided in the state memory 160. The state or state copy is then removed from the message, typically during compression, by a state data removal component 134, which also exists in the message. The overall size of the compressed message is thereby reduced.

A decompressor 130 is provided in the unit 100 for decompressing compressed messages received from an external communication unit. The decompressor 130 is preferably configured to decompress the message based on a state or state copy received from and associated with the external unit sending the compressed message. The data stored in the state/state copy, or at least a portion of this data, is typically input or added to the message during decompression by a state data adder 132.

The state copy generated by the state handler 140 may be sent in an (uncompressed) message to an external unit as discussed above with reference to fig. 3. Alternatively, the state copy is transmitted in a compressed message. In addition, this compact message may also include additional data in addition to the state. This additional data may be application data or messages, instructions or bytecode from the application 150 to inform an external unit how to handle the data in the compressed message, etc.

The state containing communication unit related data applicable to a plurality of messages according to the invention may be a User Specific Dictionary (USD) for compression and decompression purposes. Then, in the communication session, a copy of the USD may be included as part of the initial message to the external communication unit, just before generating further subsequent time-critical signaling messages from the application. This then allows for increased compression efficiency and reduced communication resource utilization once the message begins to flow between units.

The remaining units and components in the communication unit 100 have similar functions as the corresponding units and components disclosed in the embodiment of fig. 3 and are not further discussed here.

Fig. 5 is a schematic block diagram of the state processor 140 of fig. 3 and 4. The state handler 140 preferably comprises a state handler 142 adapted to generate a state and state copy comprising data related to the communication unit in which the handler 142 is implemented. The processor 142 preferably also provides a list of available states in the communication unit. This list may then include information for the different states stored in the state memory and accessible by the state processor 140. The list typically includes an identifier of each available state. This identifier may be a hash function value of the data in the state, for example an identifier calculated using the cryptographic hash algorithm 1 (SHA-1). By sending a list containing the state identifier to the external unit, the communication unit announces its available states that can be used for message processing and compression. Alternatively, instead of transmitting the state copy identifier, data allowing calculation of the identifier may be transmitted, such that the identifier is calculated later in the receiving unit from the received data.

Accordingly, the communication unit may receive a state copy from the external unit together with a list of identifiers of available states in the external unit. Alternatively, this list is provided by the state copy alone. The state processor 142 then computes a second state identifier from the received state copy, for example, a hash function value of the data therein. This second identifier is provided to an identifier comparator 144 provided in the state processor 140 together with the received list of identifiers. This comparator 144 compares the calculated second state identifier with the identifiers in the list. If a match is found, the state copy has been successfully received and is now available for message compression and decompression purposes, e.g. with an external communication unit. In addition, the comparator 144 preferably generates a save OK command to the state processor 142 that instructs the processor 142 that a copy of the received state can now be saved in the state memory unless this has not yet been performed.

The units 142 and 144, the state processor 140 may be provided as software, hardware or a combination thereof. The units 142 and 144 may be implemented together in a state processor. Alternatively, a distributed implementation with some units located elsewhere in the communication unit is also feasible.

Fig. 6 shows an embodiment of a state memory 160 according to the invention, which state memory 160 is suitable for use in the communication units of fig. 3 and 4. Memory 160 is preferably divided (logically or virtually) into a plurality of memory partitions 162; 164-1 to 164-N. First, the memory 160 preferably includes a locally available state memory partition 162 that primarily includes the state that the communication unit itself generates. In addition, multiple partitions 164-1 to 164-N dedicated to different external communication units may be found in the state memory 160. The partitions 164-1 through 164-N may be considered application specific groupings of state copies associated with peer external units. This packet may relate to an application concept such as session, dialog, connection or association, depending on the signal protocol used for the (possibly compressed) message.

The state copy received from the external communication unit is then preferably stored in the state memory 160 in a partition 164-1 to 164-N dedicated to this external unit. For example, partition 1164-1 may include one or several state copies from a first external unit, partition 2164-2 may include one or several state copies from a second external unit, and so on. Each such external unit may then access the limited amount of storage space provided by its partition 164-1 to 164-N in the memory 160 of the other unit. This means that if the communication unit has received several state copies from a given external unit, the partition 164-1 dedicated to this external unit in the state memory 160 may become full. If another state copy is received from this external unit, the state copy in the partition 164-1 dedicated to this external unit, which has been stored in the state memory 160, may have to be deleted from it in order to free up storage space. To increase the available storage space of the external unit, the state copy may be copied or moved from the dedicated partition 164-1 into the locally available memory partition 162.

The idea of using different dedicated partitions 164-1 to 164-N or parts for received state copies is to simplify the identification of the correct state copy to be used when a message is received from or to be sent to a given external unit. Alternatively, other solutions providing a connection between the state copy and the unit sending the state copy may be used. For example, each state copy may be stored with an identifier of the external unit originating the state copy.

Returning to fig. 4, the communication unit 100 may be adapted to acknowledge successful receipt of the state copy, as determined by the comparison of the state identifiers. In a first embodiment of the invention the communication unit 100 receives an acknowledgement identifier from the external unit that has sent the state copy. When the state copy has been saved in a partition dedicated to the external unit, e.g. in the state memory 160, the communication unit 100 returns an acknowledge identifier to the external unit and then declares a successful reception of the state copy. The acknowledgement identifier may be provided with the state copy or in another data message. In another embodiment the communication unit 100 sends an identifier of the state copy to the external unit, either an identifier calculated by the state handler 140 or an identifier in a state list received from the external unit, which then knows that the state copy has been correctly provided. Another possible validation scheme may be such that: the communication unit 100 processes, for example, compressing a message from the application 150 and to be sent to an external unit using the received state copy. Once the external unit receives the message, it can infer that the state copy has been successfully received because the message has been compressed or otherwise processed using the data in the state copy.

The state handler 140 may include a timer or counter that is started upon sending a copy of the state to an external unit. The state copy may be retransmitted to the external unit if no acknowledgement of receipt (acknowledgement identifier, state copy identifier or processed message) has been received when the timer or counter reaches a predetermined threshold.

The units 110, 120, 130, 132, 140 and 150 of the communication unit 100 may be provided as software, hardware or a combination thereof. The units 110, 120, 130, 132, 140, 150 and 160 may be implemented together in the communication unit 100. Or, especially for server-implemented embodiments of communication units in a communication system, it is feasible to employ a distributed implementation with some units located in different network nodes.

Fig. 7 is a signal diagram showing the exchange of states, exemplified as USDs, between two communication units, each comprising an application, a decompressor, a state handler and a compressor, as shown in fig. 4.

A first communication unit wishes to communicate with a second unit using message-based communication of a status broker. In order to reduce the message size and thereby save communication resources and speed up compression and decompression, a USD is generated, which comprises data (user-specific and/or device-specific data) related to the first communication unit and is adapted to (co-used with) a plurality of messages, which USD is stored in a state memory of the first unit. Then, a copy of this USD is generated and provided to the compressor of the first unit together with the USD identifier (ID1) (S1). There, the USD and the ID1 are included in the compressed message and transmitted to the second communication unit (S2). Alternatively, the USD and ID1 are sent in one uncompressed message, two different compressed messages, or an uncompressed message. The ID1 is preferably included in an available status list in the first communication unit.

If the message or messages including the USD copy and ID1 are compressed, the decompressor of the second unit decompresses the message and provides the USD and ID1 to the state handler (S3). The second identifier (ID2) is preferably calculated by the decompressor based on the received USD and forwarded to the state handler (S4). Alternatively, this identifier calculation is performed by the state processor. The state processor may then compare the received ID1 with the calculated ID 2. If they match, the correct USD has been received and saved in the state memory of the second unit, preferably in a partition dedicated to the USD and other state copies from the first unit.

The second communications unit may then confirm receipt of the correct USD copy. The state processor then preferably provides an acknowledgement identifier (either a dedicated acknowledgement identifier or a USD copy identifier) to the compressor (S5), which then sends this acknowledgement identifier (possibly in or as a compressed message) to the first communication unit (S6).

The USD in the first communications unit and the USD copy in the second communications unit are now available for continued data message signalling in order to reduce message size, save communications resources and improve message compression for messages sent in both directions, i.e. messages sent from the first unit to the second unit and messages sent in the reverse direction.

For example, the application in the first communication unit provides a message (m1) to be transmitted to the application of the second unit (S7). The compressor then compresses the message with the USD from the state processor (S8), typically by removing data from the message that is present in the USD and that is not necessary for successful transmission of the message in the communication system. The compressed and reduced size message thus obtained (m 1'_USD) To the second communications unit (S9). There, the decompressor decompresses the message using the USD copy from the state processor (S10), typically by re-adding data previously removed during compression in the first communication unit. The reconstructed complete message is then forwarded to the application, which can now use the message (S11).

The corresponding process may be repeated in the opposite direction, i.e. the message to be sent to the first communication unit is generated by the application of the second unit (m 2). Then, steps S12 to S16 are performed in a similar manner to steps S7 to S11.

Another possibility is that the second communication unit generates its own USD, which the first communication unit should preferably have access to. The steps S1-S3 and possibly steps S4-S6 are then repeated in the opposite direction to that shown in the figure. In this case, application messages generated by the first application and sent to the second communication unit may be compressed or processed using the USD copy associated with the second unit, and messages generated by the second application to be sent to the first unit may be correspondingly compressed or processed using the USD copy of the first communication unit. Alternatively, both USD/USD copies may be used for compression and decompression purposes.

Fig. 8 is a more detailed illustration of a communication unit 100 adapted for message compression using SigComp protocol according to the present invention. This compression protocol is further discussed in the documents [1, 2 ].

The application 150 is similar to that shown in fig. 3 and 4 above and will therefore not be discussed further.

The compressor dispatcher 125 is provided in the communication unit 100 as an interface with the application 150. The application 150 provides the compressor dispatcher with an application message and preferably also an identifier of the external unit to which the message should be sent. The compressor dispatcher 125 then invokes a particular compressor 120-1 to 120-N that ultimately returns a SigComp message to be forwarded to the remote communication unit. The communication unit 100 further comprises one or several compressors 120-1 to 120-N for converting application messages into compressed SigComp messages. In a first embodiment, a single compressor is used for all message compression. In another and more preferred embodiment, multiple compressors 120-1 to 120-N are provided in unit 100, allowing parallel compression of application messages. In this case, each state memory partition and/or external communication unit may have a dedicated compressor 120-1 to 120-N. The (partition or unit) identifier is then used to pass the application message to the correct compressor 120-1 to 120-N. Once the compressor 120-1 to 120-N receives the application message from the compressor dispatcher 125, it typically selects some algorithm to encode the data and compresses it with the USD copy 10-1 to 10-N associated with the partition or remote unit. These copies of the USDs 10-1 through 10-N are managed by a state handler 140, and the state handler 140 is the entity that stores and retrieves the USDs and other states in accordance with the present invention. The state handler 140 preferably has access to a USD 10-1 to 10-N in accordance with the compressors 120-1 to 120-N. The USDs 10-1 to 10-N are typically provided in partitions of a state memory or arranged in another equivalent manner.

According to the invention, when the compressors 120-1 to 120-N have compressed the application message with the USD copy, it returns the resulting SigComp message to the compressor dispatcher 125, which compressor dispatcher 125 forwards the SigComp message to the I/O unit 110 or to the transport layer for sending to the external communication unit.

When the I/O unit 110 receives a SigComp message from an external unit, it forwards the message to the decompressor dispatcher 135. The decompressor dispatcher 135 is an interface to the application 150. The SigComp message is then provided to decompressor 130, where an instance of a generic decompressor virtual machine (UDVM) is preferably invoked. The SigComp message is then decompressed using the data in the USDs 10-1 to 10-N provided by the state handler 140. The resulting application message (uncompressed SigComp message) is sent to decompressor dispatcher 135, which forwards the message to application 150.

The units 110 to 150 of the communication unit 100 may be provided as software, hardware or a combination thereof. The units 110 to 150 may be implemented together in the communication unit 100. Or, especially for server implemented embodiments of communication units in a communication system, embodiments may be employed in which some units are distributed among different network nodes.

Surprisingly, as discussed in document [2], embodiments of the invention adapted to use SigComp can reuse an improved form of shared state transmission between two endpoints.

In clear contrast to the state of the invention, the state of the invention comprising communication unit related data is applicable to (common) multiple application messages and is used to reduce the size of these messages, thereby saving communication resources, but one shared state consists of only uncompressed messages. The shared state is only used to compress related messages received by the endpoint before the current compressed message. Furthermore, once the endpoint receives the shared state, it passes the shared state to an upper layer, i.e., to an application in the endpoint. In addition, the first endpoint generating the shared state stores the shared state in a partition in the state memory dedicated to the external or second endpoint. However, the shared state is not stored in the second endpoint that subsequently receives the shared state.

The purpose of sharing state in SigComp is therefore to compress subsequent messages from previously received messages in one-way communication, whereas the purpose of the present invention is to use state to reduce the amount of data that has to be transmitted in data messages between communication units, i.e. for two-way message transmission.

Fig. 9 is a flowchart illustrating a state-mediated data signaling method according to the present invention. The method begins at step S20 where the first communication unit provides a status comprising data associated with the unit and applicable to a plurality of data messages to be transmitted to at least a second external communication unit. In a next step S21, a copy of this state is generated in the first cell. This copy is then transmitted to the second communications unit in step S22 and stored in the second communications unit in step S23. The first communications unit may now access the state and the second communications unit may access a copy or instance of the state. Then, in a next step S24, the (application) message transmitted between the communication units is processed, and the above state and state copy are used to adjust (reduce or re-establish) the size of the message. This step may be repeated for a plurality of messages sent from the first unit to the second unit and/or from the second unit to the first unit, as indicated by the dashed line 300. The method then ends.

Fig. 10 is a flow chart showing additional steps of the method of fig. 9. The method continues from step S21 of fig. 9. In a next step S30, the first communication unit stores the provided state in a locally available part of the associated state memory, which, if already stored therein, does not have to be performed. The first state identifier is then generated and sent to the second communications unit at step S31. This identifier may be a hash function value of the data in the state or at least a part thereof and is preferably sent in the available state list in the first communication unit. The method then continues to step S22 of fig. 9.

Fig. 11 is a flow chart showing additional steps of the method of fig. 9. The method continues from step S22 of fig. 9. In a next step S40, the second communications unit calculates a second identifier from the received state copy. This calculated identifier is then compared to the announced state identifier (in the state list) received from the first communications unit at step S41. If they do not match, then the state copy is not saved in the second communications unit and the method ends. Optionally, the second communications unit may notify the generator of the state copy, i.e. the first communications unit, that the state copy does not correspond to the received state identifier. However, if the two identifiers match, the method continues to step S23 of fig. 9.

Fig. 12 is a flow chart showing additional steps of the method of fig. 9. The method continues from step S23 of fig. 9. In a next step S50, the second communication unit may optionally copy or move the state copy from the partition in the state memory dedicated to the first communication unit to the locally available memory partition. This increases the available storage space for the state received from and associated with the first unit. The second unit preferably acknowledges receipt of the state copy at step S52, for example by returning a dedicated acknowledgement identifier or state copy identifier to the first communications unit. Alternatively or additionally, in step S52, a message processed with the state copy in the second unit may be sent to the first unit as a confirmation identifier.

Fig. 13 is a flow chart showing the message processing steps of fig. 9 in more detail. The method continues from step S23. In a next step S60, data present in the state, which are not needed for sending the message, but which are subsequently used in the remote second unit for processing and/or interpreting the message, are removed from the (header of the) message by the first communication unit. The resulting size-reduced message is then sent to the second unit in step S61. When the second unit receives this (reduced size) message, the data is re-added to (the header of) the message using the state copy in step S62. The method then ends. To implement the present invention in communication units that communicate using compressed messages, state and state copies are preferably used for message compression and decompression operations to remove and add data, respectively, to reduce the size of any transmitted compressed messages transmitted between the communication units.

It will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departure from the scope thereof, which is defined by the appended claims.

Reference to

[1] Price et al, network working group, request comments: 3320, class: standards Track, Signal Compression (SigComp), month 1 2003.

[2] Hannu et al, network workgroup, request comments: 3321, class: information, Signal Compression (Signal Comp) -Extended Operations, month 1 2003.

Claims

1. A data signalling method for message based communication between a first communication unit (100) and a second communication unit (200), the method comprising the steps of:

-initiating a message-based communication between the first communication unit (100) and the second communication unit (200) by providing a state (10) in the first communication unit (100), the state (10) comprising communication unit related data, applicable to a plurality of communication messages to be transmitted between the first communication unit (100) and the second communication unit (200);

-the first communication unit (100) generating a copy of the state (10);

-sending said state copy and a first identifier (ID1) of said state copy from said first communication unit (100) to said second communication unit (200);

-the second communication unit (200) generating a second identifier (ID2) based on the received state copy;

-the second communication unit (200) comparing the received first identifier (ID1) and the generated second identifier (ID 2);

-storing the state copy in the second communication unit (200); and

-if the second identifier (ID2) corresponds to the first identifier (ID1), processing the first communication message (m1) or the second communication message (m2) with the state (10) or the state copy by adjusting the size of the first communication message (m1) or the second communication message (m2) of the plurality of communication messages in dependence on at least a part of the communication unit related data,

the method is characterized in that: the processing step comprises the following steps:

-said first communications unit (100) removing at least a portion of said communications unit related data in said state (10) from said first communications message (m1) to obtain a first reduced size communications message (m 1'_USD)；

-said first communications unit (100) transmitting said first reduced size communications message (m 1'_USD) To the second communication unit (200); and

-the second communications unit (200) adding at least a portion of the communications unit-related data in the state copy to the first reduced-size communications message (m 1'_USD) To obtain the first communication message (m 1).

2. The method of claim 1, wherein: the processing step comprises the following steps:

-the second communication unit (200) removing the status from the second communication message (m2)Duplicating at least a portion of said communications unit related data to obtain a second reduced size communications message (m 2'_USD) (ii) a And

-the second communications unit (200) sending the second reduced size communications message (m 2'_USD) To the first communication unit (100).

3. The method of claim 2, further comprising the steps of: the first communications unit (100) adding at least a portion of the communications unit-related data in the state (10) to the second reduced-size communications message (m 2'_USD) To obtain the second communication message (m 2).

4. A method according to any one of claims 1 to 3, characterized by:

the storing step includes the steps of: storing the state copy at the second communications unit (200) into a partition (164-1) dedicated to the first communications unit (100) if the second identifier (ID2) corresponds to the first identifier (ID 1).

5. The method of claim 4, further comprising the steps of: copying the state copy from the partition (164-1) dedicated to the first communication unit (100) at the second communication unit (200) into a locally available state memory (162) of the second communication unit (200).

6. The method of claim 1, further comprising the steps of: storing the status (10) in a locally available status memory (162) of the first communication unit (100).

7. The method of claim 1, wherein: the message-based communication between the first communication unit (100) and the second communication unit (200) is comprised in the communication networkCompressed message based communication between first (100) and second (200) communication units, wherein at least a portion of the communication unit related data in the status (10) is removed from the first communication message (m1) at the first communication unit (100) to obtain a first reduced size communication message (m 1'_USD) Previously, the first communications unit (100) compressed the first communications message (m1) according to the status (10) and added at least a portion of the communications unit-related data in the status copy to the first reduced-size communications message (m1 ') at the second communications unit (200)'_USD) After that, the second communication unit (200) decompresses the compressed first communication message according to the state copy.

8. The method of claim 3, wherein: message-based communication between the first communication unit (100) and the second communication unit (200) comprises compressed message-based communication between the first (100) and second (200) communication units, wherein at least a portion of the communication unit-related data in the state copy is removed from the second communication message (m2) at the second communication unit (200) to obtain a second reduced-size communication message (m 2'_USD) Previously, the second communications unit (200) compressed the second communications message (m2) in accordance with the state copy and added at least a portion of the communications unit-related data in the state (10) to the second reduced-size communications message (m2 ') at the first communications unit (100)'_USD) After that, the first communication unit (100) decompresses the compressed second communication message according to the state (10).

9. The method of claim 7 or 8, wherein: the plurality of communication messages (m1, m2) are compressed using SigComp compression.

10. A method according to any one of claims 1 to 3, further comprising the step of:

-the second communication unit (200) receiving an acknowledgement identifier (ACK) from the first communication unit (100); and

-if said second identifier (ID2) corresponds to said first identifier (ID1), said second communication unit (200) returns said acknowledgement identifier (ACK) to said first communication unit (100).

11. A communication unit (100) adapted for message-based communication with an external communication unit (200), comprising:

-means (110) for receiving a copy of a state (10), said state comprising communication unit related data, applicable to a plurality of communication messages to be transmitted between said communication unit (100) adapted for message based communication with an external communication unit (200) and said external communication unit (200);

means (110) for receiving a first identifier (ID1) of the state copy;

means (130) for generating a second identifier (ID2) based on the received state copy;

comparing means (144) for comparing the received first identifier (ID1) and the generated second identifier (ID 2);

a storage means (140) for storing the state copy; and

processing means (130), responsive to said comparing means (144), for processing a communication message (m1 'of said plurality of communication messages with said stored state copy when said second identifier (ID2) corresponds to said first identifier (ID 1)'_USDM2), the processing component (130) being configured to condition the communication message (m1 ') in dependence upon at least a portion of the communication unit related data in the state copy'_USD) The size of (a) is (b),

the method is characterized in that: the communication message is a reduced size communication message (m 1'_USD) And said processing means (130) including a communications message (m1 ') for adding at least a portion of said communications unit-related data in said state copy to said reduced size'_USD) The addition member (132) of (1).

12. A communication unit adapted for message-based communication with an external communication unit (200) according to claim 11, wherein said processing means are replaced by a compressor (120) and a decompressor (130), said adding means (132) being provided in said decompressor (130) for adding said at least part of said communication unit-related data in said state copy to a compressed communication message received from said external communication unit (200) with said at least part of said communication unit-related data in said state (10) removed.

13. A communication unit adapted for message-based communication with an external communication unit (200) according to claim 11, characterized by: the processing means (130) comprises removing means (134) for removing at least a part of the communication unit related data in the state copy from the communication message (m 2).

14. A communication unit adapted for message-based communication with an external communication unit (200) according to claim 13, characterized in that said processing means are replaced by a compressor (120) and a decompressor (130), said removing means (134) being provided in said compressor (120) for compressing a communication message (m2) to be sent to said external communication unit (200) by removing said at least part of said communication unit related data in said state copy from said communication message (m 2).

15. A communication unit adapted for message-based communication with an external communication unit (200) according to claim 12 or 14, characterized by: the compressor (120) and decompressor (130) are configured to compress and decompress signals using SigComp protocol.

16. A communication unit adapted for message-based communication with an external communication unit (200) according to any of claims 11 to 14, characterized by: the comparison component (144) is configured to generate a storage command when the second identifier (ID2) corresponds to the first identifier (ID1), and the storage component (140) is configured to store the state copy upon receipt of the storage command.

17. A communication unit adapted for message-based communication with an external communication unit (200) according to any of claims 11 to 14, characterized by:

the storage means (140) is configured to store the state copy in a partition (164-1) dedicated to the external communication unit (200).

18. A communication unit adapted for message-based communication with an external communication unit (200) according to claim 17, further comprising: -means (142) for copying the state copy from the partition (164-1) dedicated to the external communication unit (200) into a locally available state memory (162).

19. A communication unit adapted for message-based communication with an external communication unit (200) according to any of claims 11 to 14, characterized by: further comprising means (110) for sending an acknowledgement identifier (ACK) to the external communication unit (200) when the second identifier (ID2) corresponds to the first identifier (ID1) in response to the comparing means (144).

20. A communication unit (100) adapted for message-based communication with an external communication unit (200), comprising:

-means (142) for generating a state (10), said state (10) comprising communication unit related data, applicable to a plurality of communication messages to be transmitted between said communication unit (100) adapted for message based communication with an external communication unit (200) and said external communication unit (200);

-means (140) for storing said state (10);

-means (142) for generating a copy of the state (10);

-means (110) for providing said state copy for storage in said external communication unit (200) and for providing a first identifier (ID1) of said state copy to said external communication unit (200);

-receiving means (110) for receiving an acknowledgement identifier (ACK) from the external communication unit (200), said acknowledgement identifier (ACK) being sent in response to a correspondence between a second identifier (ID2) and said first identifier (ID1), said second identifier (ID2) being generated by the external communication unit (200) from said state copy; and

-processing means (130), responsive to said receiving means (110), for processing a communication message (m1, m2 'of said plurality of communication messages with said stored state (10) upon determining by receipt of said acknowledgement identifier (ACK) that said second identifier (ID2) corresponds to said first identifier (ID 1)'_USD) Said processing means (130) being configured to condition said communication message (m1, m2 ') in accordance with at least a portion of said communication unit related data in said state (10)'_USD) The size of (a) is (b),

the method is characterized in that: the processing means (130) comprises removing means (134) for removing at least a part of the communication unit related data in the state (10) from the communication message (m 1).

21. A communication unit adapted for message-based communication with an external communication unit (200) according to claim 20, characterized in that said processing means are replaced by a compressor (120) and a decompressor (130), said removing means (134) being provided in said compressor (120) for compressing a communication message (m1) to be sent to said external communication unit (200) by removing said at least part of said communication unit related data in said state from said communication message (m 1).

22. Such as rightA communication unit adapted for message-based communication with an external communication unit (200) according to claim 20, characterized in that: the communication message is a reduced size communication message (m 2'_USD) And the processing means (130) comprises adding means (132) for adding at least a portion of said communication unit related data in said status (10) to said reduced size communication message (m 2'_USD) In (1).

23. A communication unit adapted for message-based communication with an external communication unit (200) according to claim 22, wherein said processing means is replaced by a compressor (120) and a decompressor (130), said adding means (132) being provided in said decompressor (130) for adding said at least part of said communication unit-related data in said state (10) to a compressed communication message received from said external communication unit (200) with said at least part of said communication unit-related data in said state copy removed.