WO2013186322A2

WO2013186322A2 - Data compression in a communications network

Info

Publication number: WO2013186322A2
Application number: PCT/EP2013/062302
Authority: WO
Inventors: Paul Stjernholm; Hans Eriksson; Jens Knutsson; Fredrik Persson; Lars Westberg
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2012-06-13
Filing date: 2013-06-13
Publication date: 2013-12-19
Also published as: WO2013186322A3

Abstract

A method and apparatus for handling data compression in a mobile communications network. As a result of mobility of a mobile endpoint such as a mobile terminal, a first network node receives compression information relating to a remote node. The compression information is selected from any of compression capabilities of the remote node, a type of compression available at the remote node and an identity of the remote node. The received compression information is used to perform a compression operation on first data to produce modified data. The modified data is then sent towards the remote node.

Description

Data Compression in a Communications Network

TECHNICAL FIELD The invention relates to data compression in a mobile communications network. BACKGROUND

When sending data over a communications network, compression is a technique that is used to minimize the bandwidth required by that data in order to make the communications network more efficient. This is particularly important for communications networks that rely on wireless transmission of data. Wireless Area Network (WAN) acceleration/optimization of sending data relies on many different optimization techniques to reduce the bandwidth needed by services when sending data. This lowers the transmission costs and improves the Quality of Experience (QoE) for the end user.

Compressing the size of data content, using techniques such as de-duplication, may significantly reduce the bandwidth required, and solutions to do this are commercially available.

The process of de-duplication is illustrated in Figure 1 , in which a compressor 1 or a de-compressor 2 identifies byte patterns in a payload of a data stream and associates an identified byte pattern with a shorter index, referred to as a signature. This is done for many byte patterns, leading to many signatures, which are stored in a database. The data payload and the associated signatures are transmitted to the remote side, where the same association is stored in a database. This phase is denoted as the learning phase. At some point in time the de-compressor 2 agrees with the compressor 1 to start sending compressed data over the link. Alternatively, a signature can be assigned to a pattern of bytes as soon as the pattern is repeated. Subsequent byte patterns identified by the compressor 1 are replaced with the corresponding signatures, which are sent over the link. At the de-compressor 2, the signatures are again replaced with the full byte patterns. The original data stream is thus recreated and further processed as normal. Solutions are implemented in the network user plane and do not rely on the control plane. A compressor 1 typically associates the signatures with a de-compressor 2. The correct signatures may therefore rely on knowledge of the identity of the decompressor 2 (or compressor 1 ). It is possible that a compressor 1 may associate a signature with a particular byte pattern for sending the data associated with the byte pattern to a particular de-compressor 2, and associate a different signature to the same byte pattern for sending the data associated with the byte pattern to a different decompressor.

Content compression and de-duplication is available between a server and one or more mobile clients targeting the enterprise scenario. However, if the server side is integrated in a mobile network node below a mobility anchor point, for example in a Serving Gateway (SGW), Serving GPRS Support Node (SGSN) or Radio Network Controller (RNC), then the compression and de-compression must take into account mobility of the mobile terminal. The network side needs to be able to compress data so that any mobile terminal may de-compress it, and be able to de-compress data from any mobile terminal. In this case, a mobile terminal may roam into a new cell handled by a different de-compressor, but the network side compressor may not have the identity of the different de-compressor.

Figure 2 illustrates a network architecture intended for an enterprise scenario in which an endpoint (such as a central office) 3 connects to one or more branch offices, or an office connects to a mobile workforce 4, 5, 6. In this case, the office 3 uses compression on the downlink and decompression on the uplink, and the mobile workforce side uses de-compression on the downlink and compression on the uplink.

Existing solutions for mobile clients 4, 5, 6 in an enterprise scenario cannot be directly deployed for a public scenario in a mobile network infrastructure if the downlink compression/uplink de-compression is deployed in a network node below the mobility anchor point, such as a PDN Gateway (PGW) 7 (or a GGSN), as shown in Figure 3. The reason that existing solutions cannot be deployed in this type of architecture is that the identity of the up-link de-compressor may change dynamically owing to mobile terminal mobility. In this example, a terminal 4 is connected to a source eNodeB 8 and a source SGW 9 but, because of mobility of the terminal 4, may subsequently connect to a target eNodeB 10 and a target SGW 1 1 . The compressor needs to know which signatures can be used when compressing data towards a certain de-compressor. For example, if a mobile terminal is connected to a source SGW 9 in a Long Term Evolution (LTE) network, the compressor at the terminal 4 knows the identity of the decompressor associated with the source SGW, and so can send compressed data using signatures. If the mobile terminal subsequently moves and connects to a new target SGW 1 1 , the compressor must communicate with a new de-compressor.

Existing solutions to account for mobile terminal mobility are based on the decompressor sending a notification to the compressor that it has received an unknown signature in a session. This will happen after handover of the mobile terminal, when the new de-compressor has not established a signature database with the compressor. The compressor then resets compression for that session and recommences the learning phase again. However, this approach result in the compression being less efficient since the learning phase can take around 2 hours to reach a compression efficiency of 80%.

A further issue with mobile terminal mobility is that a compressor in the mobile terminal or the network is not aware if compression is supported when the mobile terminal enters a new cell or network. Existing solutions to cater for mobility are based on the de-compressor notifying the compressor of an unknown signature in a session. The compressor then resets compression for that session and recommences the learning phase. However, this approach will result in the compression being less efficient since the learning phase can take two hours to reach 80% of the compression efficiency. Solutions also deploy a handshake procedure between compressor and de- compressor to certify that compression is supported in both ends. However, this solution will induce some delay and payload data may need to be sent uncompressed until the de-compressor is identified.

SUMMARY

It is an object of the invention to address the problems caused by mobile terminal mobility when sending and receiving compressed data.

According to a first aspect, there is provided a method of handling data compression in a mobile communications network. As a result of mobility of a mobile endpoint such as a mobile terminal, a first network node receives compression information relating to a remote node. The compression information is selected from any of compression capabilities of the remote node, a type of compression available at the remote node and an identity of the remote node. The received compression information is used to perform a compression operation on first data to produce modified data. The modified data is then sent towards the remote node. An advantage is that, for example, a compressor at the mobile endpoint is aware of compression information relating to a decompressor on the uplink, and can take it into account in the event of mobile endpoint mobility when the network side compression is deployed below a mobility anchor point in the network. The term "mobility" here refers not just to geographical mobility of the mobile endpoint, but mobility from a network function point of view, for example when the mobile endpoint connects to a new network node for reasons other than geographical mobility. As an option, the compression operation is compression of uncompressed data, the first data is uncompressed data, the modified data is compressed data and the first network node is the mobile endpoint. As an alternative option, the compression operation is de-compression of compressed data, the first data is compressed data, the modified data is de-compressed data and the remote node is the mobile endpoint.

The compression information is optionally provided to the first network node in an Access Network Discovery and Selection Function Managed Object. The compression information is optionally added as any of local information relating to an area within the network, and network wide information relating to the entire network.

As an alternative option, the compression information is provided to the first network node in an Information Entity broadcast to a plurality of network nodes.

As a further alternative option, the compression information is provided to the first network node in an Information Element provided to the first network node in a dedicated handover signalling message.

The modified data is optionally sent between a mobile endpoint and a network node disposed between the mobile endpoint and a mobility anchor point in the mobile communications network. According to a second aspect, there is provided a mobile endpoint for use in a mobile communications network. The mobile endpoint is provided with a receiver for receiving from a further node compression information, the compression information selected from any of compression capabilities of a remote node, a type of compression available and an identity of the remote node. A computer readable medium in the form of a memory is provided for storing the compression information. A processor is provided for using the received compression information to compress data. A transmitter is provided for sending the compressed data on an uplink towards the remote node. Note that the remote node and the further node may or may not be the same node. An advantage of this node is that, for example, a compressor at the mobile endpoint is aware of compression information relating to a decompressor on the uplink, and can take it into account in the event of mobile endpoint mobility when the network side compression is deployed below a mobility anchor point in the network.

According to a third aspect, there is provided a network node for use in a mobile communication network. The network node comprises a receiver for receiving compression information, the compression information selected from any of compression capabilities of a mobile endpoint, a type of compression available and an identity of the mobile endpoint. A computer readable medium in the form of a memory is provided for storing the compression information. A processor is provided for using the received compression information to de-compress compressed data. A transmitter is provided for sending the de-compressed data on a downlink towards the mobile endpoint.

According to a fourth aspect, there is provided a network node for use in a mobile communications network. The network node is provided with a processor for generating a message comprising compression information, the compression information selected from any of compression capabilities of a remote node, a type of compression available and an identity of the remote node. A transmitter is provided for sending the message towards a first node, such that the first node can use the compression information to perform a compression operation on data to be sent to the remote node. This allows the first node to receive compression information and can potentially reduce the time of the learning phase. According to a fifth aspect, there is provided a computer program comprising computer readable code which, when run on a network node, causes the network node to perform the method as described above in the first aspect. According to a sixth aspect, there is provided a computer program comprising computer readable code which, when run on a mobile endpoint, causes the mobile endpoint to behave as a mobile endpoint as described above in the second aspect.

According to a seventh aspect, there is provided a computer program comprising computer readable code which, when run on a network node, causes the network node to behave as a network node as described above in the third aspect.

According to an eighth aspect, there is provided a computer program product comprising a computer readable medium and a computer program as described above in any one of the fifth, sixth or seventh aspects, wherein the computer program is stored on the computer readable medium.

BRIEF DESCRIPTION OF DRAWINGS Figure 1 illustrates schematically in a block diagram a network architecture and signalling for performing de-duplication when sending compressed data;

Figure 2 illustrates schematically in a block diagram a network architecture and signalling for performing de-duplication when sending compressed data in an enterprise scenario with a mobile workforce;

Figure 3 illustrates schematically in a block diagram a network architecture and signalling for inter-SGW handover in an LTE network where the network side compression and decompression is handled at a SGW;

Figure 4 illustrates a policy branch of an ANDSF Managed Object according to an embodiment of the invention; Figure 5 illustrates schematically in a block diagram how a compressor in a mobile terminal uses compression information from the ANDSF Managed Object according to an embodiment of the invention; Figure 6 illustrates schematically in a block diagram an exemplary compressor being notified of compression capabilities of a remote end using mobile system signalling;

Figure 7 is a flow diagram showing exemplary steps; and Figure 8 illustrates schematically in a block diagram an exemplary mobile terminal.

DETAILED DESCRIPTION

Compressions methods such as de-duplication can be deployed in a mobile terminal or other network node and when a remote side is deployed in the mobile network infrastructure below the mobility anchor point such as a PDN Gateway 7 or GGSN. It is necessary to inform nodes involved in compression about receiving nodes compression capabilities and types of compression used, and also in a mobile communications network to inform nodes when a de-compressor (or compressor) at a remote node has changed because of mobility of an endpoint node such as a mobile terminal. In this case, the compressor must be informed of the change in order to select appropriate signatures for the receiving de-compressor.

The deployment of compression and decompression may be performed on several levels in the network depending on the technology used. A solution depends on protocol layers on IP level and above being accessible, which disqualifies some nodes, e.g. the Base Transceiver Station (BTS) in GSM. For example, GGSN/PGW nodes can perform compression, the RNC and eNodeB can perform decompression. This assumes a downlink connection, and it will be appreciated that the roles are reversed for an uplink.

Taking the example of uplink compression, one way to achieve this is to add information to an Access Network Discovery and Selection Function (ANDSF) to support uplink compression decisions in a mobile terminal. The added compression information may be any of compression capability support of the remote side, a type of compression used if several variants exist, and an identity of the de-compressor on the remote side. Of course, other information relating to compression may also be provided. With this information, the compression entity can use the proper signatures relevant to the particular decompressor when compressing the payload.

The information is added to ANDSF, described in 3GPP TS 24.312, Access Network Discovery and Selection Function (ANDSF) Management Object (MO). This provides compression policies to nodes such as the mobile terminal by adding compression information to an ANDSF managed object, as illustrated in the policy branch shown in Figure 4.

The information may be added as local information for an area, e.g. Location Area (LAC), Tracking Area (TAC) or Cell Identity (CI), or as network wide information, i.e. for the PLMN.

In the case where compression is generally supported using the same type of compression it may be added as network wide information.

The de-compression identity should be area-specific where the area coincides with the node hosting the de-compression entity. This allows the compressor in the mobile terminal to select the proper signatures when compressing the payload. If the decompression is located in one single location, e.g. in a GGSN or PGW 7, the de- compression identity is added as network wide information.

Figure 5 illustrates how a compressor 12 uses the compression information from the ANDSF Managed Object (MO) 13 in the mobile terminal 4. The embodiment described above allows higher compression gains in a network uplink compared to a existing solutions, requires a lower consumption of resources over the air interface, and therefore may improve a quality of experience (QoE) for the user.

Note that the embodiment described above can in some circumstances be used when signalling compression information to a network node other than the mobile terminal 4, such as an eNodeB 8. In this case, the compression information may be used for decompressing data sent on a downlink towards the mobile terminal 4.

According to a second embodiment, compression information is added to either the System Information (SI) broadcasted per cell, or in dedicated mobility signalling. The added compression information may be any of compression capability support of the remote side, a type of compression used if several variants exist, and an identity of the de-compressor on the remote side. Of course, other information relating to compression may also be provided. With this information, the compression entity can use the proper signatures relevant to the particular decompressor when compressing the payload.

With this information the compression entity can use the proper signatures relevant to the particular decompressor when compressing the payload.

Adding a new Information Entity (IE) to one 3GPP System Information Block (SIB) (see 3GPP TS 36.331 , Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification, 3GPP TS 25.331 , Radio Resource Control (RRC); Protocol specification, 3GPP TS 44.018, Mobile radio interface layer 3 specification; Radio Resource Control (RRC) protocol) or the IEEE WiFi Beacon Frame Format (see IEEE Standard Part 1 1 : Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications), broadcasted in each cell (as shown in Figure 7), provides information to the mobile terminal 4 of network compression support, e.g. supported / not supported, type of compression and identity of the de-compressor of the remote side. The de-compressor may be identified by the node realizing the compression function if only one compression entity per node is assumed. For IEEE WiFi Beacon Frame Format alternatively a vendor specific IE could be used.

The System Information provides information to terminals at idle mode cell selection/re- selection, but may also be read by the terminal at active mode handover/cell change.

In the event of mobility of the mobile terminal, it will attach to a new network node (such as a new eNodeB 10) and must be notified of the compression capabilities of the new eNodeB 10 or other network nodes that have change as a result of the mobility. Figure 6 illustrates how the compressor 12 at the mobile terminal 4 is notified of a change of de-compressor via a mobile network signalling using a signalling entity 14 such as a receiver.

The System Information only informs the mobile terminal 4 of the network capability. Thus, the network is not aware of the compression capability of the mobile terminal. One way to implicitly inform the network of the terminal capability would be for the terminal to compress information in the uplink and for the network to delay any compression in the downlink until a compressed payload is received. Another approach is for the terminal to append capability information when accessing the network in e.g. the RRC Connection Request message for WCDMA and LTE.

To further enhance the compression gain at mobility when the mobile terminal 4 is in active mode, information may be added to existing mobility signalling messages. Uplink

Adding a new IE in a dedicated handover signalling messages to the mobile terminal 4 provides information of compression support in the network, e.g. supported / not- supported, type of compression, and identity of the de-compressor of the remote side. The de-compressor may be identified by the node realizing the compression function if only one compression function per node is assumed. Note that techniques based on ANDSF and broadcast signalling, as described above, also support uplink compression.

Figure 10.1 .2.1 .1 -1 , "Intra-MME/Serving Gateway HO" in 3GPP TS 36.300, Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Stage 2, describes an intra-MME/SGW handover procedure for LTE. The IE mentioned above could, for example, be appended to an L3 control signalling message RRC Connection Reconfiguration. The corresponding L3 control signalling message for WCDMA could be Physical Channel Reconfiguration (3GPP TS 25.308, High Speed Downlink Packet Access (HSDPA); Stage 2) and for GSM the PS Handover Command (3GPP TS 43.129, Technical Specification Group GSM/EDGE Radio Access Network; Packet-switched handover for GERAN A/Gb mode; Stage 2). For WiFi solutions based on any future handover/cell change signalling could be used as for 3GPP access technologies. Downlink

When a new mobile terminal associates with a network node holding a downlink compressor the compressor needs to be informed of the mobile terminal decompressor identity in order to select the proper signatures to use (learned from previous sessions). The mobile terminal de-compressor could be indentified via e.g. the IMSI or the MSISDN.

The information relating to the mobile terminal 4 de-compressor identity and type of compression may be provided to the target node as part of the handover preparation phase.

An SRNS relocation procedure for WCDMA is shown in Figure 39, "SRNS Relocation Procedure" in 3GPP TS 25.308, High Speed Downlink Packet Access (HSDPA); Stage 2. In this example, the Forward Relocation Request or the Relocation Request messages may be used to convey information relating to the mobile terminal 4 (and therefore the de-compressor, where the mobile terminal 4 has only one decompressor) identity to the downlink compressor.

Figure 9, "PS Handover Preparation Phase; Inter-SGSN case (GERAN A/Gb mode)" 3GPP TS 43.129, Technical Specification Group GSM/EDGE Radio Access Network; Packet-switched handover for GERAN A/Gb mode; Stage 2 describes a PS handover procedure for GSM where, for example, a PS Handover Request and an Update PDP Context Request messages may be used to convey information of the mobile terminal 4 identity to the downlink compressor. A new Information Entity (IE) may be needed in the Update PDP Context Request message to provide a persistent terminal identity. For Wi-Fi, a similar solution based on any future handover/cell change signalling may be used as for 3GPP access technologies.

Figure 5.5.1 .1 .3-1 , "X2-based handover with Serving GW relocation" in 3GPP TS 23.401 , General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access) describes X2-based handover with Serving GW relocation where, for example, a Path Switch Request, a Create Session Request, and a Modify Bearer Request messages can be used to convey information of the mobile terminal 4 identity to the downlink compressor. A new Information Entity (IE) may be needed in the messages to provide a persistent terminal identity.

An Information Entity (IE), containing information of whether the remote side supports compression or not and type of compression, may be added in all applicable described messages above for the compressor to use when deciding to activate compression.

The second embodiment allows higher compression gains, compared to existing solutions, provides lower resource consumption, for example over the air interface, and thereby may improve the Quality of Experience (QoE).

Both embodiments described above can are represented in the flow diagram of Figure 7. This figure gives the example of a mobile terminal 4 compressing data and sending it to the network in an uplink. In order to do this, it must receive compression information for a network node that will perform the decompression. The following numbering corresponds to that of Figure 7:

51 . As a result of mobility, the mobile terminal 4 receives compression information as described above from a remote network node. The compression information may be received in an IE or an ANDSF MO, as described in the two embodiments above. The compression information may identify parameters such as type of compression used, compression capabilities and an identity of the remote node (for example, if the mobile terminal is aware of the identity of the remote node it may be able to determine other factors such as the compression type and capabilities). Note that mobility referred to is not limited to geographic mobility, but mobility from a network function point of view. For example, the mobile terminal 4 may attach to a new network node for reasons other than geographical movement of the terminal, such as load balancing.

52. The mobile terminal 4 uses the received compression information to perform a compression operation on uncompressed data to produce modified, compressed data.

53. The mobile terminal then sends the modified, compressed data towards the remote node. Turning now to Figure 8, there is illustrated a mobile terminal 4 such as a User Equipment (UE). The mobile terminal 4 is provided with a receiver 15 for receiving compression information, such as compression capabilities of a remote node, a type of compression available and an identity of the remote node. A computer readable medium in the form of a memory 16 is provided for storing the compression information 17. A processor 18 uses the received compression information to compress data, and a transmitter 19 is provided for sending the compressed data on an uplink towards the remote node. A program 20 may also be provided which, when executed by the processor 18, cause the mobile terminal 4 to behave as described above. Note that the mobile terminal 4 may be used with either of the first or second embodiments of the invention.

It will be appreciated that function elements illustrated in Figure 8 may be implemented in one or more physical embodiments. For example, the processor 4 may be a plurality of separate processors, and the memory 16 may be a plurality of different physical memories. Similarly, the transmitter 15 and receiver 19 may be implemented in the same physical transmitter or receiver, or as one or more transceivers.

It will be appreciated by the person of skill in the art that various modifications may be made to the above described embodiment without departing from the scope of the present invention. For example, the functions of the network node are described as being embodied at a single node, but it will be appreciated that different functions may be provided at different network nodes. Furthermore, de-duplication is described as an example of data compression/de-compression, but it will be appreciated that the principles of the invention apply to other forms of compression such as information relating to data differencing.

The following acronyms have been used in the above description: ANDSF Access Network Discovery and Selection Function

CI Cell Identity

DL Downlink

DNS Domain Name System

eNodeB enhanced Node B

GGSN Gateway GPRS Support Node GPRS General Packet Radio Service

IE Information Elements

LTE Long Term Evolution

LAC Location Area

OAM Operation and Maintenance

PDN Packet Data Network

PGW PDN Gateway

QoE Quality of Experience

RAN Radio Access Network

RIM RAN Information Management

RNC Radio Network Controller

SGSN Serving GPRS Support Node

SGW Serving Gateway

SI Signalling Information

SIB Signalling Information Block

TAC Tracking Area

TCP Transport Control Protocol

UL Uplink

WAN Wireless Area Network

WCDMA Wideband Code Division Multiple Access

Claims

1 . A method of handling data compression in a mobile communications network, the method comprising:

as a result of mobility of a mobile endpoint, receiving at a first network node, compression information relating to a remote node, the compression information selected from any of compression capabilities of the remote node, a type of compression available at the remote node and an identity of the remote node;

using the received compression information to perform a compression operation on first data to produce modified data; and

sending the modified data towards the remote node.

2. The method according to claim 1 , wherein the compression operation is compression of uncompressed data, the first data is uncompressed data, the modified data is compressed data and the first network node is the mobile endpoint.

3. The method according to claim 1 , wherein the compression operation is decompression of compressed data, the first data is compressed data, the modified data is de-compressed data and the remote node is the mobile endpoint.

4. The method according to any one of claims 1 to 3, wherein the compression information is provided to the first network node in an Access Network Discovery and Selection Function Managed Object.

5. The method according to claim 4, wherein compression information is added as any of local information relating to an area within the network, and network wide information relating to the entire network.

6. The method according to any one of claims 1 to 3, wherein the compression information is provided to the first network node in an Information Entity broadcast to a plurality of network nodes.

7. The method according to any one of claims 1 to 3, wherein the compression information is provided to the first network node in an Information Element provided to the first network node in a dedicated handover signalling message.

8. The method according to any one of claims 1 to 7, wherein the modified data is sent between a mobile endpoint and a network node disposed between the mobile endpoint and a mobility anchor point in the mobile communications network.

9. A mobile endpoint for use in a mobile communications network, the mobile endpoint comprising:

a receiver for receiving from a further node compression information, the compression information selected from any of compression capabilities of a remote node, a type of compression available and an identity of the remote node;

a computer readable medium in the form of a memory for storing the compression information;

a processor for using the received compression information to compress data; and

a transmitter for sending the compressed data on an uplink towards the remote node.

10. A network node for use in a mobile communication network, the network node comprising:

a receiver for receiving compression information, the compression information selected from any of compression capabilities of a mobile endpoint, a type of compression available and an identity of the mobile endpoint;

a processor for using the received compression information to de-compress compressed data; and

a transmitter for sending the de-compressed data on a downlink towards the mobile endpoint.

1 1 . A network node for use in a mobile communications network, the network node comprising:

a processor for generating a message comprising compression information, the compression information selected from any of compression capabilities of a remote node, a type of compression available and an identity of the remote node; a transmitter for sending the message towards a first node, such that the first node can use the compression information to perform a compression operation on data to be sent to the remote node.

12. A computer program, comprising computer readable code which, when run on a network node, causes the network node to perform the method as claimed in any of claims 1 to 8.

13. A computer program, comprising computer readable code which, when run on a mobile endpoint, causes the mobile endpoint to behave as a mobile endpoint as claimed in claim 9.

14. A computer program, comprising computer readable code which, when run on a network node, causes the network node to behave as a network node as claimed in claim 1 1 .

15. A computer program product comprising a computer readable medium and a computer program according to any one of claims 12 to 15, wherein the computer program is stored on the computer readable medium.