WO2015114077A1

WO2015114077A1 - Multipoint transmission method and multipoint transmission control system using network coding

Info

Publication number: WO2015114077A1
Application number: PCT/EP2015/051901
Authority: WO
Inventors: Haibin Zhang; Ljupco Jorguseski; Jasper Goseling; Jacob Cornelis Van Der Wal
Original assignee: Koninklijke Kpn N.V.; Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno; University Of Twente
Priority date: 2014-01-31
Filing date: 2015-01-30
Publication date: 2015-08-06

Abstract

The disclosure relates to a multipoint transmission system and method for delivering a plurality of data packets at a user device from a first transmission node and a second transmission node over a wireless network interface using a multipoint transmission control system. At least a first network coded data packet and a second network coded data packet are obtained, wherein the first network coded data packet corresponds to a first linear combination of two or more data packets of the plurality of data packets to be delivered at the user device and the second network coded data packet corresponds to a second linear combination of two or more data packets of the plurality of data packets to be delivered at the user device, wherein the first linear combination is different from the second linear combination. The first network coded data packet is provided to the first transmission node for transmission onto the wireless network interface for the user device, and the second network coded data packet is provided to the second transmission node for transmission onto the wireless network interface for the user device.

Description

Multipoint transmission method and multipoint transmission control system using network coding

FIELD OF THE INVENTION

The invention relates to a multipoint transmission method and multipoint transmission control system using network coding. More specifically, the invention relates to a multipoint transmission method and multipoint transmission control system wherein network coded data packets are provided to different transmission nodes.

BACKGROUND

Recent developments in 3GPP standardization relate to Long Term Evolution (LTE) and Long Term Evolution Advanced (LTE Advanced) telecommunications networks and devices. LTE and LTE Advanced, also known as 4G (i.e. fourth generation) mobile communications standard, is a standard for wireless communication of high-speed data for mobile phones and data terminals. It is a successor of GSM/EDGE (also known as 2G or 2.5G) and UMTS/HSPA (also known as 3G) network technologies, increasing the capacity and user data throughput using a different radio interface together with evolutions and improvements in the radio access network and the core network.

Downlink coordinated multipoint (CoMP) transmission is a concept of receiving data at a user device in a coordinated manner from multiple transmission nodes (e.g. cells, base stations, NodeBs in the case of UMTS/HSPA, evolved NodeBs (eNBs) in the case of LTE/LTE Advanced), possibly from geographically separated transmission nodes. The 3GPP Technical Report 'Coordinated multi-point operation for LTE physical layer aspects', TR 36.819, v1 1.1.0 refers to different CoMP categories, including a category termed 'dynamic cell selection' wherein at a particular point in time data is transmitted only from a single transmission node and there is a process to dynamically select which of the transmission nodes transmits the data. For example, selecting a transmission node with the, at the particular point in time, best conditions on the wireless interface allows to increase the rate at which data packets may be delivered at the user device, compared to a single-point mode of operation.

To enable transmission of data to a user device from multiple wireless transmission nodes that are geographically separated from each other, the same data may be provided to each of the involved transmission nodes. In the example shown in FIG. 1A, data packets P1 to P3 are provided from a node, e.g. a gateway GW, to two different geographically separated transmission nodes TN1 and TN2 in order to enable both transmission nodes to transmit, when selected, the data packets to the user de- vice over the wireless interface.

In the multipoint transmission method of FIG. 1A, a same data packet (i.e., each of the data packets P1 to P3) is transmitted to both the first transmission node TN1 and to the second transmission node TN2. Accordingly, the traffic load in the network resulting from multipoint transmission is doubled, tripled, etc. in proportion to the number of involved transmission nodes (i.e. proportional to the size of the CoMP cooperating set) in comparison to single point transmission (and also in comparison with multipoint transmission from multiple geographically collocated transmission points). Moreover, coordination between the wireless transmission nodes may be required in order for one transmission node to know which of data packets P1 to P3 have been delivered at the user device by the other transmission node, such that those data packets need not be transmitted by and may be discarded at the former transmission node.

In the multipoint transmission method of FIG. 1 B, data packets P1 and P3 are transmitted to only TN1 and data packet P2 is transmitted to only TN2 for wireless delivery at the user device, thus reducing traffic load in the network compared to the method of Fig. 1A. However, in the method of Fig. 1 B coordination between the transmission nodes would be more complicated compared to the meth- od of Fig. 1A, for example because in the method of Fig. 1 B not each transmission node is able to deliver any of the data packets P1 to P3 at the user device.

There is a need in the art for an improved method and system for multipoint transmission.

SUMMARY

To that end, in one aspect, the present disclosure presents a multipoint transmission method for delivering a plurality of data packets at a user device from a first transmission node and a second transmission node over a wireless network interface using a multipoint transmission control system.

In one embodiment, the first and second transmission nodes comprise geographically separated transmission nodes, such as cells or base stations (e.g. NodeBs, eNBs).

The transmission nodes may be comprised in a cellular wireless access network to enable the (e.g. mobile) user device to connect to a telecommunications network. One such

telecommunications network comprises a Long Term Evolution (LTE) or LTE-Advanced network. Another example of such a network comprises a UMTS network, for example supporting High Speed Packet Ac- cess (HSPA).

Network coding comprises making a linear combination of (at least the payload of) two or more data packets (e.g. via a bit-wise XOR operation of the two or more data packets), resulting in a network coded data packet. A single network-coded data packet thus represents a single linear combination of the two or more data packets. Note that different linear combinations, and thus different network coded data packets, may be made from a same set of two or more data packets. Also, a linear combination of the two or more data packets of a given (same) size may result in a network-coded data packet of that given size. Overhead information (e.g. overhead bits) may additionally be included to indicate or signal the linear combination made in producing the network coded data packet.

In general, a network coded packet C can be expressed as a linear combination of data packets P:

C_n = a_n-|Pi + a_n2P2 ⁺ 3n3P3 + ...

Network coded data packets C are different if the linear combinations are different, i.e. if either the coding coefficients are different or the involved data packets P are different. Preferably, the vectors of coding coefficients of two or more network coded data packets C are linearly independent. This facilitates resolving the data packets P from the network coded data packets C at e.g. a user device.

By applying network decoding on a sufficient number of different network coded data packets C, the data packets P comprised in the linear combinations represented in the network coded data packets may be resolved. Network decoding may also involve the use of data packets already available (e.g. resolved previously or received as non-network coded data packets).

In this disclosure, a data packet may comprise any block (e.g. an integer number of bits or bytes) of payload data. A data packet typically also has additional overhead (bits or bytes), e.g. header and/or trailer bits, for the purpose of transporting the payload data. Examples of overhead comprise an indication of the data packet (e.g. a packet sequence number) and/or payload destination, of a (logical) channel, of a data packet and/or a payload length and/or an error check (e.g. CRC). A data packet in this disclosure thus comprises e.g. an Internet Protocol (IPv4, IPv6) datagram, possibly with additional overhead such as GTP overhead for tunnelling the IP packet through part of the telecommunications network (e.g. from a gateway (S-GW) to a base station (eNB)), an RLC PDU and a Transport Block as e.g. used on a wireless (radio) connection between a base station (eNB) and a user device (UE).

Performing network coding on two or more data packets is to be understood as performing network coding on at least the payload data in each of the two or more data packets, and not necessarily on overhead bits or bytes in these data packets.

In the disclosed multipoint transmission method, the multipoint transmission control sys- tem obtains at least a first network coded data packet and a second network coded data packet. The first network coded data packet corresponds to a first linear combination of two or more data packets of the plurality of data packets to be delivered at the user device and the second network coded data packet corresponds to a second linear combination of two or more data packets of the plurality of data packets to be delivered at the user device.

The first network coded data packet is provided to the first transmission node for transmission onto the wireless network interface for the user device.

The second network coded data packet is provided to the second transmission node for transmission onto the wireless network interface for the user device.

The first linear combination is different from the second linear combination, such that e.g. two data packets P-i , P₂ from the plurality of data packets to be delivered at the user device are delivered at the user device by resolving P-i , P₂ from two different network coded data packets d , C₂ received from, respectively, the first transmission node and the second transmission node.

In another aspect of the disclosure, a multipoint transmission control system configured for performing the multipoint transmission control method disclosed herein, is presented.

In another aspect of the disclosure, a computer program or suite of computer programs and carrier(s) therefore are disclosed.

In yet another aspect of the disclosure, a telecommunications system is disclosed comprising a multipoint transmission control system and two transmission nodes, preferably geographically separated from each other, connected thereto are disclosed. In still another aspect of the disclosure, a user device is disclosed configured for obtaining the plurality of data packets in the multipoint transmission method disclosed herein.

By feeding, from the multipoint transmission control system, the transmission nodes with network coded data packets comprising (different) linear combinations of the plurality of data packets to be delivered at the user device and providing the transmission nodes with the network coded data packets to be transmitted to the user device over the wireless network interface, a reduction in network traffic is obtained on the first and second connection in comparison with the transmission scenario of FIG. 1 A. The linear combinations may be arbitrary combinations of the plurality of data packets to be delivered at the user device and, therefore, it is not relevant which network coded data packet is or has been transmit- ted from which transmission node. Consequently, transmission coordination between the transmission nodes may be omitted.

The multipoint transmission control system may receive the data packets from an upstream network node, e.g. from a gateway.

It should be appreciated that the method may be executed in a cellular wireless telecom- munications system and the first transmission node and second transmission node are cells (base stations) on geographically separated locations both providing radio coverage for the user device.

It should also be appreciated that the multipoint transmission method may comprise downlink coordinated multipoint transmission using dynamic cell selection, e.g. inter-NodeB or inter-eNB coordinated multipoint transmission using dynamic cell selection.

It should be appreciated that network coding is not necessarily performed by the multipoint transmission control system. Network coded data packets may be received from an external network coding entity.

The multipoint transmission control system may be located anywhere within the system, e.g. within the telecommunications network.

In one embodiment, the multipoint transmission control system may be collocated with or may be integrated with one of the transmission nodes. For example, if ample transmission capacity is available to the collocated or integrated multipoint transmission control system / transmission node, reducing the traffic load on this route yields little or no benefit, while reducing the number of locations does. The embodiment may also reduce the number of acknowledgement indications received by the multipoint transmission control system.

In one disclosed embodiment, the multipoint transmission control system is connected with the first transmission node over a first connection and the second transmission node over a second connection. The first network coded data packet is transmitted over the first connection to the first transmission node for transmission onto the wireless network interface for the user device and the second network coded data packet is transmitted over the second connection for transmission onto the wireless network interface for the user device. Providing the multipoint transmission control system upstream of the transmission nodes improves transmission control capability of the system and may therefore enhance efficient delivery of data packets to the user device. The multipoint transmission node may e.g. be connected to, be collocated with or be integrated with a gateway handling the plurality of data packets to be delivered the user device.

In one disclosed embodiment, the multipoint transmission method further comprises the step at the multipoint transmission control system of receiving a flow control indication from at least one of the first transmission node and the second transmission node to provide one or more further network coded data packets to, respectively, the first transmission node and the second transmission node. The one or more further network coded data packets comprise one or more further linear combinations of two or more data packets of the plurality of data packets to be delivered at the user device. The flow control indication enables flow control of network coded data packets to respective transmission nodes. The fur- ther linear combinations are different from the first and second linear combinations.

The flow control indication for the transmission of one or more network coded data packets may be used in one embodiment to e.g. optimize the timing of transmission from the multipoint transmission control system and/or resource usage on first and second connections. In one embodiment, the flow control indication from a transmission node comprises information relating to, in principle, a sin- gle (further) network coded data packet to be transmitted to the transmission node. An advantage of this embodiment is that the resource usage on the connection from the multipoint transmission control system to the transmission node may be precisely controlled. Another advantage is that it enables the transmission node, by controlling the time of transmitting an indication to the multipoint transmission control system, to control the time of transmitting a (further) network coded data packet from the multipoint transmission control system, and therewith, to control the expected time of arrival of the (further) network coded data packet at the transmission node, e.g. to control the expected time of arrival of the (further) network coded data packet to occur at or shortly before the time the transmission node expects to complete delivery of a preceding network coded data packet to the user device.

In one further embodiment, the flow control indication from a transmission node compris- es information relating to the number of further network coded data packets to be transmitted to the transmission node. An advantage of this embodiment is that indications for the transmission of individual network coded data packets may be avoided, thereby reducing the number of flow control indications to be transmitted in the uplink direction. In one embodiment, the flow control indication from a transmission node comprises information regarding the absolute or relative time that one or more (further) network coded data packets should be transmitted from the multipoint transmission control system to the transmission node or are expected to arrive at the transmission node. An advantage is that it enables the transmission node to control the time of transmitting multiple (further) network coded data packet from the multipoint transmission control system, and therewith, to control the expected time of arrival of the multiple (further) network coded data packet at the transmission node.

In one disclosed embodiment, an acknowledgement indication is received at the multipoint transmission control system from at least one of the first transmission node and the second transmission node indicating delivery of at least one of the first network coded data packet and a data packet of the two or more data packets of the first linear combination at the user device. The acknowledgement indication may also be based on receipt of a non-network coded data packet by the user device. The multipoint transmission control system may perform a control action in response to receiving the acknowledgement indication. The control action is based on the information obtained from the acknowledgement indication that network coded data packets and/or data packets resolved from the network coded data packets and/or non-network coded data packets have been delivered at the user device. Examples of control actions include providing, selecting and/or transmitting further network coded data packets to the transmission node(s) and discarding (deleting) network coded data packets and/or data packets stored at the multipoint transmission control system if these are determined from the acknowledgement information to be no longer necessary.

In one particular embodiment, the acknowledgement indication indicates error-free deliv- ery of the first network coded data packet by the first transmission node or error-free delivery of the second network coded data packet by the second transmission node. This embodiment is particularly useful for flow control of network coded data packets between the multipoint transmission control system and the first transmission node and between the multipoint transmission control system and the second transmission node, respectively. For example, in one embodiment, the control action comprises providing further network coded data packets to respectively, the first transmission node and the second transmission node, wherein the further network coded data packets comprises further different linear combinations of two or more data packets of the plurality of data packets to be delivered at the user device. One example of an acknowledgement indication may be based on and/or comprises a STATUS report as referred to in e.g. 3GPP Technical Specification TS 36.322, V1 1.0.0, Έ-UTRA, Radio Link Control (RLC) protocol specification'.

In one embodiment, the acknowledgement indication comprises identity information of at least one of the first network coded data packet and one or more data packets of the two or more data packets of the first linear combination. In one embodiment, the identity information indicates which network coded data packet has been received error-free at the user device. In one embodiment, the identity information indicates which data packet(s) has/have been resolved from one or more network coded data packets. Non-network coded data packets received error-free by the user device may also be indicated. These embodiments omit the need to know which transmission node transmitted the particular network coded data packet. These embodiments may also facilitate a single control connection between the multipoint transmission control system and the user device. In one embodiment, the control action comprises identifying, from the identity information, the first network coded data packet or one or more data packets of the two or more data packets of the first linear combination and discarding (deleting) at least one of the identified first network coded data packet and one or more identified data packets of the two or more data packets of the first linear combination stored at the multipoint transmission control system. Such an embodiment may save resources in the multipoint transmission control system and/or on network connections. The control action may also involve discarding network coded data packets prepared in advance but determined unnecessary to provide to the transmission node.

In each of the above embodiments, the transmission node(s) may either process or transparently transmit the acknowledgement indication. The transmission node may process indication(s) received from the user device into an acknowledgement indication that relates to one or more network coded data packets (possibly identifying the network coded data packets) and/or to one or more data packets (possibly identifying the data packets) delivered at the user device (e.g. network-decoded from network coded data packets and/or received as non-network coded data packets). The acknowledgment indication a transmission node receives from the user device may also be transparently forwarded by the transmission node towards the multipoint transmission control system. It should be appreciated that an acknowledgement indication transmitted by a transmission node is not necessarily limited to only those network coded data packets (and/or to data packets represented therein) transmitted to the user device by that transmission node.

It should be appreciated that one or more acknowledgement indications may be combined with each other and that one or more acknowledgement indications may be separate from or be combined with flow control indications to transmit one or more (further) network coded data packets.

In one disclosed embodiment, sets of data packets may be distinguished for the plurality of data packets to be delivered at the user device, each set containing two or more data packets of the plurality of data packets. Network coded data packets obtained from linear combinations of data packets from a first set of data packets and from linear combination of a second set of data packets may be provided to the transmission node(s). In one embodiment, the second set of data packets consists of data packets not contained in the first set of data packets, i.e. the first set and second set are disjunct. Distinguishing sets of data packets from which network coded data packets may be obtained facilitates resolving data packets at the user device and may simplify memory management. At the side of the multipoint transmission system, distinguishing sets may facilitate network coding and/or reduce delay in providing network coded data packets. It should be appreciated that a network coded data packet for a particular set does not necessarily comprise a linear combination of all data packets of that set. It should also be appreciated that the same coding coefficients may be used within a set (if different data packets are used for the linear combination) and/or between sets.

In one embodiment, the, e.g. all or substantially all, network coded data packets obtained from linear combinations of data packets from the first set of data packets are provided prior to network coded data packets obtained from linear combinations of data packets from the second set of data packets. In other words, a substantially set-by-set providing or transmission scheme is envisaged here. It should be appreciated, however, that some network coded data packets associated with the second set may already be provided to a transmission node and/or transmitted by a transmission node for the user device before or near completion of providing/transmitting network coded data packets associated with the first set of data packets. Such an embodiment facilitates a smooth transition between obtaining network coded data packets associated with the first set to obtaining network coded data packets associated with the second set. It may also reduce decoding delays at the user device.

In one embodiment, the network coded data packets obtained from linear combinations of data packets from a second set of data packets are provided to and/or transmitted from the multipoint transmission control system only after receiving one or more acknowledgement indications. These one or more acknowledgement indications may indicate delivery at the user device of at least a predetermined number of network coded data packets obtained from linear combinations of data packets from the first set of data packets. Alternatively, the one or more acknowledgement indications may indicate that the data packets of the first set can be decoded or have been decoded by the user device.

One condition on which the predetermined number of network coded data packets is based is whether the number of data packets is sufficient to resolve the data packets of a given set. In one embodiment, the user device may transmit a next set indication received at the multipoint transmission control system indicating to the multipoint transmission control system to proceed providing network coded data packets obtained from linear combinations of two or more data packets from the second set of data packets. In response to receipt of the next set indication, the multipoint transmission control system may omit providing further network coded data packets associated with data packets from the current set. In addition, the multipoint transmission control system may discard data packets from the current set of data packets based on the next set indication. The transmission node may also determine not to transmit and to discard network coded data packets associated with the current set of data packets on the basis of the next set indication.

In another embodiment, the multipoint transmission control system may e.g. count the number of acknowledgement indications received from the transmission nodes indicating delivery of a network coded data packet at the user device and continue transmission of network coded data packets obtained from linear combinations of the first set and refrain from starting transmission of network coded data packets obtained from linear combinations of the second set until the number of acknowledged net- work coded data packets equals or exceeds a predefined number. Alternatively, the multipoint transmission control system may continue as long as there is at least one non-discarded data packet from the first set stored at the multipoint control system.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present inven- tion may take the form of an entirely hardware embodiment, a software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," "module" or "system". Functions described in this disclosure may be implemented as an algorithm executed by a microprocessor of a computer. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied, e.g., stored, thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a solid-state drive, a random access memory (RAM), a non-volatile memory device, a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this disclosure, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless (using electromagnetic and/or optical radiation), wired, optical fiber, cable, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java(TM), Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on a user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor, in particular a microprocessor or central processing unit (CPU), of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer, other programmable data processing apparatus, or other devices create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus pro- vide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the functions noted in the blocks may sometimes be executed in the reverse order, depending upon the func- tionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention will be explained in greater detail by reference to exemplary embodiments shown in the drawings, in which:

FIGS. 1A and 1 B are schematic diagrams of multipoint transmission systems;

FIG. 2 is a schematic illustration of three generations of telecommunications networks; FIGS. 3A and 3B are schematic diagrams of telecommunications systems according disclosed embodiments;

FIG. 4 is a flow chart illustrating some steps of a multipoint transmission method accord- ing to a disclosed embodiment;

FIGS. 5A-5D depict time diagrams illustrating steps of multipoint transmission methods; and

Fig. 6 is a schematic block diagram of a general system (e.g. the multipoint transmission control system) or node (e.g. the transmission node) of a telecommunications network or a user device.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 2 shows a schematic illustration of a telecommunications system 1. The telecommunications system 1 comprises a cellular radio access network system (also indicated as E-UTRAN or (UT)RAN in FIG. 2) and a core network system containing various elements or nodes as described in further detail below.

In the telecommunications system of FIG. 2, three generations of networks are schematically depicted together for purposes of brevity. A more detailed description of the architecture and overview can be found in 3GPP Technical Specification TS 23.002, V12.3.0, 'Network Architecture' which is included in the present application by reference in its entirety.

The lower branch of FIG. 2 represents a GSM/GPRS or UMTS network.

For a GSM/GPRS network, a radio access network (RAN) system comprises a plurality of nodes, including base stations (combination of a BSC and a BTS), not shown individually in FIG. 2. The core network system comprises a Gateway GPRS Support Node (GGSN), a Serving GPRS Support Node (SGSN, for GPRS) or Mobile Switching Centre (MSC, for GSM, not shown in FIG. 2) and a Home Location Register (HLR). The HLR contains subscription information for user devices 2, e.g. mobile stations MS.

For a UMTS radio access network (UTRAN), the radio access network system also com- prises a Radio Network Controller (RNC) connected to a plurality of base stations (NodeBs), also not shown individually in FIG. 2. In the core network system, the GGSN and the SGSN/MSC are connected to the HLR that contains subscription information of the user devices 2, e.g. user equipment UE.

The upper branch of the telecommunications system in FIG. 2 represents a next generation network, commonly indicated as Long Term Evolution (LTE) system or Evolved Packet System (EPS).

The radio access network system, indicated as E-UTRAN, comprises base stations (evolved NodeBs, eNodeBs or eNBs), not shown individually in FIG. 2, providing cellular wireless access for a user device 2, e.g. a user equipment UE. The core network system comprises a PDN Gateway (P- GW) and a Serving Gateway (S-GW). The E-UTRAN of the EPS is connected to the S-GW via a packet network. The S-GW is connected to a Home Subscriber Server HSS and a Mobility Management Entity

MME for signalling purposes. The HSS includes a subscription profile repository SPR for user devices 2.

For GPRS, UMTS and LTE systems, the core network system is generally connected to a further packet network 3, e.g. the internet.

Further information of the general architecture of a EPS network can be found in 3GPP Technical Specification TS 23.401 , V12.3.0, 'GPRS enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access'.

FIGS. 3A and 3B are schematic diagrams of telecommunications systems 1. The telecommunication systems are applied for performing a multipoint transmission method of which some steps are illustrated in the flow chart of FIG. 4. The multipoint transmission method may comprise downlink coordinated multipoint transmission using dynamic cell selection.

In each of the telecommunications systems 1 , a multipoint transmission control system MTC is provided.

In FIG. 3A, the MTC is provided upstream of transmission nodes TN1 and TN2. The MTC receives data packets P1 , P2, P3 from a gateway GW. The MTC may be collocated with or inte- grated in the gateway GW, as indicated by the dashed box. The gateway GW may e.g. comprise the S-GW of the telecommunications system 1 drawn in FIG. 2. In FIG. 3B, the MTC is connected to, collocated with or integrated in a transmission node TN1 .

Transmission nodes TN1 , TN2 are provided on geographically separated locations both providing radio coverage for the user device.

In both systems 1 , in step S1 , the MTC obtains network coded data packets C1 , C2, C3 by making different linear combinations of data packets P1 , P2, P3. MTC may itself contain network coding functionality or may outsource the network coding to another entity within or outside the

telecommunications network 1 .

In step S2, one or more network coded data packets C1 , C3 are provided to first transmission node TN1 for transmission onto a wireless interface for UE 2. In FIG. 3A, network coded data packets are transmitted over a connection 4A in the telecommunications system 1 to TN1 , e.g. a connection between an S-GW and an eNB. In FIG. 3B, one or more network coded data packets are generated or received locally at the location of TN1.

In step S3, one or more other network coded data packets C2 are provided to second transmission node TN2 for transmission onto a wireless interface for UE 2. In FIG. 3A, network coded data packets are transmitted over a connection 4B in the telecommunications system 1 to TN2, e.g. a connection between the S-GW and an eNB. In FIG. 3B, one or more network coded data packets are transmitted over a connection 4C in the telecommunications system 1 to TN2. In an LTE-based network, such a connection may coincide with a so-called X2 interface between neighbouring eNBs.

By feeding, from the multipoint transmission control system MTC, the transmission nodes TN1 , TN2 with network coded data packets C1 , C2, C3 comprising different linear combinations of the plurality of data packets P1 , P2, P3 to be delivered at the user device UE2 and providing the transmission nodes TN 1 , TN2 with the network coded data packets C1 , C2, C3 to be transmitted to the user device UE 2 over the wireless network interface, a reduction in network traffic is obtained in the system of

FIG. 3A on the first connection 4A and second connection 4B in comparison with the transmission scenario of FIG. 1A. In the system of FIG. 3B a reduction in network traffic is obtained on the connection(s) leading towards TN2 (4B and 4C). The linear combinations C1 , C2, C3 may be arbitrary different combinations of the plurality of data packets P1 , P2, P3 to be delivered at the user device UE 2 and, therefore, it is not relevant which network coded data packet C1 , C2, C3 is or has been transmitted from which transmission node TN1 , TN2. Consequently, transmission coordination between the transmission nodes TN1 , TN2 may be omitted.

FIGS. 5A-5D depict time diagrams illustrating steps of multipoint transmission methods.

In FIG. 5A, the MTC obtains network coded data packets C1 , C2, C3, C4 comprising dif- ferent linear combinations of data packets P1 , P2, P3, P4. The MTC provides TN 1 with C1 and TN2 with C2. At some moment in time, TN1 delivers C1 at the UE 2 over the wireless interface and the MTC receives a flow control indication F1 from TN1 . In response to F1 , the MTC provides a further network coded data packet C3 to TN1 that is transmitted onto the wireless interface for the UE 2. A flow control indication F3 is received at the MTC from TN1 for a still further network coded data packet. Meanwhile, TN2 has transmitted network coded data packet C2 (this network coded data packet may have been waiting at TN2 for some time, for example, because, in a dynamic cell selection mode of operation, for some time TN2 has not been selected to transmit onto the wireless interface for the UE 2). The MTC receives a flow control indication F2 from TN2. The MTC provides network coded data packet C4 to TN1 , e.g. in response to reception of flow control indication F3. TN1 transmits C4 onto the wireless interface for the UE 2. The MTC receives a flow control indication F4 from TN1. If the MTC had still not received flow control indication F2 (i.e. the MTC would have received a total of only three flow control indications), e.g. in response to receiving flow control indication F4, a further network coded data packet C5 (not shown) could have been obtained (or used if C5 was already obtained in advance of being needed) and provided to TN1 for transmission onto the wireless interface for the UE 2.

In FIG. 5B, like transmissions are indicated by like references as in FIG. 5A. In FIG. 5B, flow control of further network coded data packets C3, C4 is assisted by acknowledgements indications, in this particular example, A1 , and A3 from transmission node TN1 indicating delivery (here implying error-free delivery) of network coded data packets at the UE 2. The acknowledgement indications A1 , A2, A3, A4 are either transparently forwarded by the transmission nodes TN1 , TN2 or triggered at the transmission nodes TN1 , TN2 in response to receiving delivery confirmation D1 , D2, D3, D4 from UE 2 as indicated in FIG. 5B.

In the time diagram of FIG. 5C, again, like transmissions are indicated by like references. In the case of FIG. 5C, the MTC starts transmitting network coded data packet packets C1 , C2 obtained from linear combinations of, at that moment in time, available data packets P1 , P2. After having provided these network coded data packets C1 , C2 to the transmission nodes TN1 , TN2, respectively, further data packet P3 and data packets P4, P5 arrive at the MTC.

At the time data packet P3 becomes available at the MTC, a network coded data packet C3 may be obtained being a linear combination of e.g. data packets P1 , P2 and P3. The receipt of flow control indication F1 from TN 1 triggers the MTC to provide another network coded data packet, in this example C3, to TN1. In the case of FIG. 5C, the UE is able to resolve P1 , P2 and P3 from C1 , C2 and C3 delivered at the UE 2. The UE 2 indicates this to the MTC by a packet specific indication PSI, indicating that the UE 2 has resolved P1 , P2 and P3. When further data packets P4, P5 are received at the MTC, the MTC is thus made aware that further network coded data packets (e.g. provided in response to having received flow control indications F3, F2) do not need to comprise linear combinations involving P1 ,

P2 and P3 anymore. Network coded data packets C4 and C5 may be obtained that involve linear combinations of solely data packets P4, P5.

In the time diagram of FIG. 5D sets are distinguished for the plurality of data packets P1 , P2, P3, P4, P5, P6, P7 and P8 to be delivered at the user device. A first set consists of data packets {P1 , P2, P3, P4}. A second set consists of data packets {P5, P6, P7, P8}. The size of the set may be predetermined or may also be based on an indication (e.g. a capability indication) by the UE 2 to the MTC. The MTC may determine from the acknowledgement indications A (here also serving as flow control indications) that sufficient network coded data packets C associated with a given set have been delivered at the UE 2. A more explicit indication may be a next set indication NS 1 transmitted from the UE 2 and re- ceived by the MTC (also shown in FIG. 5D). An explicit next set indication enables the method to be applied without the MTC keeping track of received acknowledgement indications A. An explicit next set indication also enables the method to be applied without the transmission nodes transmitting acknowledgement indications A to the MTC and/or without the UE 2 transmitting delivery confirmations D to a transmission node. Any of the indications that a next set should be used results in obtaining and/or providing network coded data packets C5 etc. to TN1 and TN2 associated with data packets P5, P6, P7, P8 from the second set.

The flow control indications F, acknowledgement indications A, packet specific indications PSI and/or next set indications received at the MTC may trigger one or more control actions at the MTC.

In FIG. 5A, a flow control indication F triggers transmission of a further network coded data packet C. Flow control indications may also trigger transmission of more than one network coded data packet C. The same holds for acknowledgement indications A in FIG. 5B.

An indication may also cause discarding of network coded data packets C and/or data packets P stored at the MTC. For example, in FIG. 5B, reception of any of the acknowledgement indica- tions A1 , A2, A3, A4 at the MTC may result in discarding an arbitrary data packet stored at the MTC of the data packets P1 , P2, P3, P4. For example, in FIG. 5C, reception of the PSI at the MTC may result in discarding data packets P1 , P2 and P3 stored at the MTC.

An indication may also cause selection of the data packets P to be included in a linear combination for a further network coded data packet. For example, in FIG. 5C reception of the PSI at the MTC causes further network data packets to be linear combinations of P4 and P5 and to no longer include P1 , P2 or P3. Further, in FIG. 5D, the next set indication NS 1 causes further network coded data packets C5 etc. to be obtained from linear combinations of data packets of the next set.

FIG. 6 is a block diagram illustrating an exemplary data processing system that may be used as a part of a user equipment 2 or as a network node 10A, 10B, 10C, such as base station.

Data processing system 60 may include at least one processor 61 coupled to memory elements 62 through a system bus 63. As such, the data processing system 60 may store program code within memory elements 62. Further, processor 61 may execute the program code accessed from memory elements 62 via system bus 63. In one aspect, data processing system 60 may be implemented as a computer that is suitable for storing and/or executing program code. It should be appreciated, how- ever, that data processing system 60 may be implemented in the form of any system including a processor and memory that is capable of performing the functions described within this specification.

Memory elements 62 may include one or more physical memory devices such as, for example, local memory 64 and one or more bulk storage devices 65. Local memory may refer to random access memory or other non-persistent memory device(s) generally used during actual execution of the program code. A bulk storage device 65 may be implemented as a hard drive or other persistent data storage device. The data processing system 60 may also include one or more cache memories (not shown) that provide temporary storage of at least some program code in order to reduce the number of times program code must be retrieved from bulk storage device 65 during execution. Input/output (I/O) devices depicted as input device 66 and output device 67 optionally can be coupled to the data processing system 60. Examples of input devices may include, but are not limited to, for example, a keyboard, a pointing device such as a mouse, a touchscreen, or the like. Examples of output device may include, but are not limited to, for example, a monitor or display, speakers, or the like. Input device 66 and/or output device 67 may be coupled to data processing system 60 either directly or through intervening I/O controllers. A network adapter 68 may also be coupled to data processing system 60 to enable it to become coupled to other systems, computer systems, remote network devices, and/or remote storage devices through intervening private or public networks. The network adapter 68 may comprise a data receiver for receiving data that is transmitted by said systems, devices and/or networks to said data processing system 60 and a data transmitter for transmitting data to said systems, devices and/or networks. Modems, cable modems, and Ethernet cards are examples of different types of network adapters that may be used with data processing system 60.

As pictured in FIG. 6, memory elements 62 may store an application 69. It should be appreciated that data processing system 60 may further execute an operating system (not shown) that can facilitate execution of the application. Applications, being implemented in the form of executable program code, can be executed by data processing system 60, e.g., by processor 61. Responsive to executing the application 69, the data processing system 60 may be configured to perform one or more operation as disclosed in the present application in further detail.

In one aspect, for example, data processing system 60 may represent a multipoint trans- mission control system MTC or a user device UE. In that case, application 29 may represent a client application that, when executed, configures data processing system 60 to perform the various functions described herein with reference to an MTC or a user equipment. Examples of an MTC include a base station of a telecommunications network 1 providing cellular wireless access, e.g. a NodeB or an eNB. The user equipment can include, but is not limited to, a personal computer, a portable computer, a mobile phone, or the like.

In another aspect, data processing system 60 may represent a transmission node TN as described herein, in which case application 69, when executed, may configure data processing system 60 to perform operations as described in the present disclosure.

It is noted that the method has been described in terms of steps to be performed, but it is not to be construed that the steps described must be performed in the exact order described and/or one after another. One skilled in the art may envision to change the order of the steps and/or to perform steps in parallel to achieve equivalent technical results.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Various embodiments of the invention may be implemented as a program product for use with a computer system or a processor, where the program(s) of the program product define functions of the embodiments (including the methods described herein). In one embodiment, the program(s) can be contained on a variety of non-transitory computer-readable storage media (generally referred to as "storage"), where, as used herein, the expression "non-transitory computer readable storage media" comprises all computer-readable media, with the sole exception being a transitory, propagating signal. In another embodiment, the program(s) can be contained on a variety of transitory computer-readable storage media. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, ROM chips or any type of solid-state non-volatile semiconductor memory) on which in- formation is permanently stored; and (ii) writable storage media (e.g., flash memory, floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored.

Claims

A multipoint transmission method for delivering a plurality of data packets at a user device from a first transmission node and a second transmission node over a wireless network interface using a multipoint transmission control system, the method comprising the steps at the multipoint transmission control system of:

obtaining at least a first network coded data packet and a second network coded data packet, wherein the first network coded data packet corresponds to a first linear combination of two or more data packets of the plurality of data packets to be delivered at the user device and the second network coded data packet corresponds to a second linear combination of two or more data packets of the plurality of data packets to be delivered at the user device, wherein the first linear combination is different from the second linear combination;

providing the first network coded data packet to the first transmission node for transmission onto the wireless network interface for the user device; and

providing the second network coded data packet to the second transmission node for transmission onto the wireless network interface for the user device.

The multipoint transmission method according to claim 1 , wherein the multipoint transmission control system is connected with the first transmission node over a first connection and the second transmission node over a second connection, the method comprising the steps at the multipoint transmission control system of:

transmitting the first network coded data packet over the first connection to the first transmission node for transmission onto the wireless network interface for the user device; and

transmitting the second network coded data packet over the second connection for transmission onto the wireless network interface for the user device.

The multipoint transmission method according to claim 1 or 2, further comprising the step at the multipoint transmission control system of

receiving a flow control indication from at least one of the first transmission node and the second transmission node to provide one or more further network coded data packets to, respectively, the first transmission node and the second transmission node, wherein the one or more further network coded data packets comprise one or more further linear combinations of two or more data packets of the plurality of data packets to be delivered at the user device.

4. The multipoint transmission method according to one or more of the preceding claims, further comprising the steps at the multipoint transmission control system of

receiving an acknowledgement indication from or via at least one of the first transmission node and the second transmission node indicating delivery of at least one of the first network coded data packet and a data packet of the two or more data packets of the first linear combination at the user device; and

performing an action in response to receiving the acknowledgement indication.

5. The multipoint transmission method according to claim 4, wherein the acknowledgement indication indicates error-free delivery of the first network coded data packet by the first transmission node or error-free delivery of the second network coded data packet by the second transmission node.

6. The multipoint transmission method according to claim 5, wherein the action comprises

providing further network coded data packets to respectively, the first transmission node and the second transmission node, wherein the further network coded data packets comprise further linear combinations of two or more data packets of the plurality of data packets to be delivered at the user device.

7. The multipoint transmission method according to claim 4, wherein the acknowledgement indication comprises identity information of at least one of the first network coded data packet and one or more data packets of the two or more data packets of the first linear combination.

8. The multipoint transmission method according to claim 7, wherein the action comprises:

identifying, from the identity information, the first network coded data packet or one or more data packets of the two or more data packets of the first linear combination;

discarding at least one of the identified first network coded data packet and one or more identified data packets of the two or more data packets of the first linear combination stored at the multipoint transmission control system.

9. The multipoint transmission method according to one or more of the preceding claims, the method comprising the steps of:

- distinguishing sets of data packets for the plurality of data packets to be delivered at the user device, each set containing two or more data packets;

providing network coded data packets obtained from linear combinations of data packets from a first set of data packets; providing network coded data packets obtained from linear combinations of data packets from a second set of data packets, wherein the second set of data packets consists of data packets not contained in the first set of data packets.

10. The multipoint transmission method according to claim 9, wherein the, e.g. substantially all, network coded data packets obtained from linear combinations of data packets from the first set of data packets are provided prior to network coded data packets obtained from linear combinations of data packets from the second set of data packets.

1 1. The multipoint transmission method according to claim 9 or 10, wherein the network coded data packets obtained from linear combinations of data packets from a second set of data packets are provided only after receiving one or more acknowledgement indications indicative of at least one of

- delivery at the user device of at least a predetermined number of network coded data pack- ets obtained from linear combinations of data packets from the first set of data packets; and

- network decoding or the ability to network decode the data packets contained in the first set of data packets by the user device.

12. The multipoint transmission method according to claim 9 or 10, wherein the network coded data packets obtained from linear combinations of data packets from a second set of data packets are provided only after receiving a next set indication provided by the user device, the next set indication indicating to the multipoint transmission control system to proceed providing network coded data packets obtained from linear combinations of two or more data packets of the second set of data packets.

13. A computer program or suite of computer programs comprising at least one software code portion or a computer program product storing at least one software code portion, the software code portion, when run on a computer system, being configured for executing the method according to one or more of the claims 1-12.

14. A multipoint transmission control system for delivering a plurality of data packets at a user device from a first transmission node and a second transmission node over a wireless network interface, wherein the multipoint transmission control system is configured for:

15. The multipoint transmission control system according to claim 14 being configured for performing the method according to one or more of the claims 2-12.

16. A telecommunications network comprising the multipoint transmission control system according to claim 14 or 15 and at least a first transmission node and a second transmission node for wireless delivery of a plurality of data packets at a user device.

17. A user device configured for obtaining the delivered plurality of data packets from the multipoint transmission method of one or more of the claims 1-12.

18. The user device according to claim 17, wherein the user device is configured for transmitting or causing the transmission of one or more of:

the one or more acknowledgement indications of one or more of the claims 4-8 and 1 1 ;

the next set indication of claim 12.