Patent Publication Number: US-2017374696-A1

Title: Method and device for connectionless bearer service

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for a connectionless bearer service in wireless cellular networks. 
     BACKGROUND OF THE INVENTION 
     This section introduces aspects that may be helpful in facilitating a better understanding of the invention. 
     Accordingly, the statements of this section are to be read in this light and are not to be understood as admission about what is in the prior art. 
     In further wireless networks, e.g. of the fifth generation (5G), small data transmission or short transaction based communication is a typical scenario for Machine to Machine communication (M2M) and Internet of Things (IoT). This necessitates in general reduction of signalling overhead in connection with small data packets as the signalling overhead is significant compared to the overall data sent on the network. Thus, reduction of signalling overhead for bearer setup and release is one key element to achieve network efficiency when small, sporadic data packets are sent, e.g. in Machine to Machine communication scenarios. Further, many 5G scenarios require ultra low latency communication with negligible setup delays. 
     In current wireless networks of the fourth generation (4G) with their connection-oriented bearer services, transmission of small data is extremely inefficient. The signalling load in the networks may exceed the load caused by the user data itself. 
     In addition, the connection oriented nature of the bearer services incurs necessarily a connection setup delay (approximately more than 50 ms), which exceeds the requirements of 5G to support real-time applications with response times lower than 10 ms. 
     The 3rd Generation Partnership Project (3GPP) has recognized the problem in its report 3GPP TR 23.887 and provides potential solutions to mitigate some of the issues described above. These solutions are involving the control plane very much and therefore do not solve the control plane overload. 
     European patent application 2683211 describes a method for the support of data transmission in a packet mobile network in which a tunnel over an interface between a serving radio access node and a serving user plane CN node is predefined and identified using information referred to as connection ID information. The connection ID information provides a reference to the external packet data network and to the serving user plane CN node. EP 2683211 thus presents a pre-established connection-oriented approach in which signaling for connection setup is avoided by pre-establishing tunnels that may be used. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to address the above mentioned problems. 
     For this purpose, an embodiment of the invention provides a method for establishing a connectionless bearer service, the method comprising: transmitting a data packet comprising user data and header data, the header data comprising at least a virtual access network identifier, wherein the virtual access network identifier is a unique identifier defining a unique virtual access network for the connectionless bearer service, the virtual access network defining a unique data path from a source to a destination of the data packet and vice versa. This method has the advantage that a connection establishment, which is time consuming and especially for small data is very inefficient, is omitted. The source of the data packet is a network node from which the data packet originates. The destination, or sink, of the data packet is a network node which is the destination of the data packet. No multiple paths are possible from a source to a sink in the virtual access network. For a given pair of endpoints (each being capable of being source or destination) there thus exists merely one path. The virtual access network is composed of a subset of all network nodes of the network, the subset being suitable to form a path between the source and the sink of the virtual access network. A connectionless bearer service is to be understood as a service for data transmission not using a connection oriented data transmission procedure. There is no need for a connection setup procedure as performed in connection oriented networks. 
     According to an embodiment, the header data further comprises an access destination address. The access destination address is within the physical network of a mobile access network a unique identifier of a destination of the data packet. 
     According to an embodiment, the header data further comprises an access source address. The access source address is within the physical network of a mobile access network a unique identifier of a source of the data packet. 
     According to an embodiment, different virtual access network identifiers are assigned to different services received or provided by the same device. By assigning different virtual access network identifiers for different services, multiple virtual access networks are defined, even if they contain the same source and the same sink and include the same network nodes in the network path. This has the advantage that the different virtual access networks can have different properties, e.g. different Quality of Service properties. 
     Embodiments of the invention further relate to a method for forwarding data packets in a connectionless bearer service, the method comprising: forwarding a data packet comprising user data and header data, the header data comprising at least a virtual access network identifier, wherein the virtual access network identifier is a unique identifier extending across virtual networks and defines a unique virtual access network for the connectionless bearer service, the virtual access network defining a unique data path from a source to a destination of the data packet and vice versa. This method has the advantage that the effort for connection establishment over the access network, which is time consuming and especially for small data is very inefficient, is omitted. 
     The source of the data packet is a network node from which the data packet originates. The destination, or sink, of the data packet is a network node which is the destination of the data packet. No multiple paths are possible from a source to a sink in the virtual access network. For a given pair of endpoints (each being capable of being source or destination) there thus exists merely one path. The virtual access network is composed of a subset of all network nodes of the network, the subset being suitable to form a path between the source and the sink of the virtual access network. A connectionless bearer service is to be understood as a service for data transmission not using a connection oriented data transmission procedure. There is no need for a connection setup procedure as performed in connection oriented networks. 
     According to an embodiment, the method further comprises a step of forwarding by a network node a data packet sent by a User Equipment to the virtual access network. The data packet is forwarded to the neighbouring network node one level higher in the hierarchy of the virtual access network tree structure. The network node contains a forwarding table. Data regarding the network node one level lower in the hierarchy of the virtual access network from which a data packet was received is added to the forwarding table. Further, the forwarding table contains a source address of the data packet. The entries of the forwarding table are kept for a certain time in the network node. The time how long an entry in the forwarding table is kept is a design parameter, but preferably, it is longer than a response time to a request message. 
     According to an embodiment, the network node further forwards a data packet to a neighbouring network node one level lower in the hierarchy of the virtual access network according to the forwarding table of the network node. Thus, when receiving a data packet in upstream communication, from a User Equipment to the network, the forwarding table is maintained as described above. When a response is received in the network node, which should be sent from the network to the User Equipment, the forwarding table recognizes the destination address of the data packet, which corresponds to the source address in an upstream communication data packet and determines the correct network node one level below in the tree structure and the appropriate link for reaching the destination address. 
     According to an embodiment, the header data further comprises an access destination address. The access destination address is a unique destination address of the data packet extending across networks. The header data further comprises an access source address. The access source address is a unique source address of the data packet extending across networks. 
     According to an embodiment, the forwarding tables in the network nodes and the virtual access network identifiers define a connectionless tunnel protocol for forwarding data packets from a access source address to a access destination address. 
     Embodiments of the invention further relate to a network node for performing a method for forwarding data packets as described above. 
     Embodiments of the invention further relate to a network node for forwarding data packets in a connectionless bearer service, the network node comprising: a receiver for receiving a data packet comprising user data and header data, the header data comprising at least a virtual access network identifier, wherein the virtual access network identifier is a unique identifier extending across virtual networks and defining a unique virtual access network for the connectionless bearer service, the virtual access network defining a unique data path from a source to a destination of the data packet and vice versa; a source address analyser for analysing the source of a data packet according to the header data of the data packet; a memory configured to store a forwarding table, the forwarding table indicating the network node one level lower in the hierarchy of the virtual access network from which the data packet was received and a source address of the data packet; and a transmitter for sending a data packet downstream to a network node one level lower in hierarchy of the virtual access network according to the information stored in the forwarding table. 
     Embodiments of the invention further relate to a User Equipment for establishing a connectionless bearer service. The User Equipment is configured to perform a method for establishing a connectionless bearer service as described above. 
     Embodiments of the invention further relate to a virtual access network for transmitting data related to a dedicated service is proposed. The virtual access network comprises at least one source endpoint, at least one sink endpoint and at least one network node in the network path between the source endpoint and the sink endpoint. The virtual access network is a network slice of a physical radio access network. The virtual access network has a tree structure and is allocated to a dedicated service. The virtual access network is configured by a virtual access network identifier and is established by providing forwarding tables related to the virtual access network identifier in the network nodes as described above. The virtual access network provides a service oriented connectionless bearer service. 
     Further advantageous features of embodiments of the invention are defined and are described in the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments of apparatus and methods in accordance with embodiments of the present invention are now described, by way of examples only, and with reference to the accompanying drawings, in which: 
         FIG. 1  schematically depicts a wireless network architecture; 
         FIG. 2  depicts a schematic overview of a connection oriented bearer service; 
         FIG. 3  schematically depicts a data packet according to an embodiment of the invention; 
         FIG. 4  depicts a schematic overview of a network according to an embodiment of the invention; 
         FIG. 5  depicts a method for forwarding data packets according to an embodiment of the invention; 
         FIG. 6  depicts a schematic overview of a connectionless bearer service according to an embodiment of the invention; 
         FIG. 7  depicts a schematic overview of a connectionless bearer service according to an embodiment of the invention; 
         FIG. 8  depicts a schematic overview of a connectionless bearer service according to an embodiment of the invention; and 
         FIG. 9  schematically depicts a network node that may be used in embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof. 
       FIG. 1  schematically depicts an architecture for a wireless network, e.g. a 4G or a future 5G network. A User Equipment  1  communicates to a base station, e.g. an eNodeB  2 . A communication direction from User Equipment  1  to base station, e.g. eNodeB  2 , may be referred to as upstream. A communication direction from base station, e.g. eNodeB  2 , to User Equipment  1  may be referred to as downstream. User Equipment  1  and eNodeB  2  belong to the Evolved Universal Mobile Telecommunication System Terrestrial Radio Access Network (E-UTRAN). The eNodeB  2  is connected to a Serving Gateway (S-GW)  3 . The Serving Gateway  3  is connected to a Packet Data Network Gateway (P-GW)  4 , which provides access to the external network  5 , e.g. the Internet. 
       FIG. 2  depicts a schematic view of a connection oriented bearer service. An end-to-end connection between a User Equipment  1  and an external network  5  is depicted as end-to-end bearer  21 . It is provided by an Evolved Packet Switched System bearer (EPS-bearer)  22  and an external bearer  23  providing connection to an external network  5 , e.g. the Internet. An EPS-bearer  22  uniquely identifies traffic flows that receive a common Quality of Service (QoS) treatment between a User Equipment  1  and a Packet Data Network Gateway (P-GW)  4 . The EPS-Bearer  22  is a virtual connection between the User Equipment  1  and the Packet Date Network Gateway  4 , which identifies data sent and received between these two end points with specific QoS attributes, e.g QCI, GBR, Allocation Retention Priority. The Evolved UTRAN Radio Access Bearer (e-RAB)  24  transports the packet of an EPS-Bearer  22  between the User Equipment  1  and the Serving Gateway (S-GW)  3 . The S5/S8 Bearer  25  transports the packets of an EPS bearer  22  between the Serving Gateway  3  and the Packet Data Network Gateway  4 . The Radio Bearer  26  transports packet of an E-RAB  24  between the User Equipment  1  and the eNodeB  2 . An S1 Bearer  27  transports the packets of an E-RAB  24  between the eNodeB  2  and the Serving Gateway  3 . Packet exchange between the User Equipment  1  and the external network  5  are assigned to one or more EPS-Bearer  22  by means of Traffic Flow Templates (TFT) Defining Service Data Flows (SDF). The Radio Bearer  26 , S1 Bearer  27  and S5/S8 Bearer  25  are bound together by switching tables. The switching tables thus providing a connection oriented connection. 
       FIG. 3  schematically depicts a message format for a data packet  30  to be transmitted with a connectionless tunnelling protocol CLTP according to an embodiment of the invention. The data packet  30  being formed includes payload data  31 , also referred to as user data, and header data. The header data includes header data as known in the art which is necessary for data transmission, e.g. checksum data, flags, etc. and which are not described in further detail. 
     Further, the data packet  30  contains a virtual access network identifier  32 . The virtual access network identifier  32  is a unique identifier extending across physical networks and defining a unique virtual access network for the connectionless bearer service. A unique virtual access network is described in more detail with regard to the figures below. 
     Further, the data packet  30  contains an access source address  33 . The access source address  33  is an identifier of the origin of the data packet. Preferably, the access source address  33  is a unique source address identifying the source device from which the data packet  30  originates. In upstream communication, the source device of a data packet  30  is e.g. a User Equipment  1 . In downstream communication, the source device of a data packet  30  is e.g. a Packet Data Network Gateway  4 . 
     Further, the data packet  30  contains an access destination address  34 . The access destination address  34  is an identifier of the destination of the data packet  30 . Preferably, the access destination address  34  is a unique destination address identifying the destination device to which the data packet is to be sent. In upstream communication, the destination device of a data packet  30  is e.g. Packet Data Network Gateway  4 . In downstream communication, the destination device of a data packet  30  is e.g. a User Equipment  1 . 
     Preferably, both access source address  33  and access destination address  34  are unique addresses. This means, each access source address  33  and each access destination address  34  is assigned to a concrete device even when considering multiple networks, including neighbouring networks. This way, it is assured that one access source address  33  or one access destination address  34  is not assigned to two devices in different physical networks and the addresses allow therefore a distinct identification of the source and destination device, respectively. 
       FIG. 4  schematically depicts a wireless network scenario  40  according to an embodiment of the invention. For sake of simplicity, only a few network elements are shown. Wireless access is provided to User Equipments  42 , e.g. by an LTE or 5G network. The User Equipments  42  are connected to a external networks  50 , e.g. the Internet including servers, cloud like infrastructure and other network devices  50 . The User Equipments  42  connect to respective base stations  44 , e.g. eNodeBs by a Radio Access link  43   a ,  43   b ,  43   c , which provides a wireless connection. The base stations  44  are connected to Serving Gateways  46  by corresponding network links  45   a ,  45   b ,  45   c . The Serving Gateways  46  are connected to Packet Data Network Gateways  48  by corresponding network links  47   a ,  47   b ,  47   c . The Packet Data Network Gateways  48  are connected to the external networks  50 , e.g. by an external bearer. Multiple links  49  to the external networks  50  are available. The external networks  50  are e.g. the Internet, Operator Networks and Private Networks based on IP technology and devices of the external network  50  are e.g. servers and cloud devices. The path on which data packets  30  are sent through the network is defined by the virtual access network identifier (vACC-ID)  32 . The virtual access network defined by the virtual access network identifier  32  is to be understood as a network, e.g. a hierarchical network having a tree structure connecting a source and a sink, i.e. a network node which is the destination of a data packet  30  transmitted. In  FIG. 4 , in the upstream, a source of a data packet  30  is a User Equipment  42  and a sink of the data packet  30  is a Packet Data Network Gateway  48 , which provides connection to the external networks  50 . In the downstream, a source of a data packet  30  is a Packet Data Network Gateway  48  and a sink of the data packet  30  is a User Equipment  42 . The Packet Data Network Gateway  48  identifies by means of the destination address of the IP packet and in general by the traffic flow template (TFT) on which virtual access network a data packet is to be sent and assigns a virtual access network identifier  32 . The source is identified in the data packet  30  by an access source address  33 . The sink of a data packet  30 , i.e. the destination of a data packet  30  is identified by its access destination address  34 . The access source address  33  and the access destination address  34  are unique addresses also when exceeding a virtual access network. Thus, the access source address  33  and the access destination address  34  are unique addresses when considering the radio access network, e.g. an LTE or 5G network. The virtual access network contains only networks elements  42 ,  44 ,  46 ,  48  between the source and the destination of a data packet  30  transmitted. No multiple paths are possible from a source to a sink in the virtual access network. In other words, the virtual access network defines a unique data path from the source to the sink and vice versa. The virtual access network is composed of a subset of all network nodes of the network.  FIG. 4  depicts three virtual access networks. The first one contains links  43   a ,  45   a ,  47   a ,  49   a . The links of the first virtual access network are depicted by solid lines and the tree structure is shown. The second virtual access network contains links  43   b ,  45   b ,  47   b ,  49   b . The links of the second virtual access network are depicted by dashed lines and the tree structure is shown. The third virtual access network contains links  43   c ,  45   c ,  47   c ,  49   c . The links of the third virtual access network are depicted by crossed lines and the tree structure is shown. 
     In a network having a tree structure, receiving data packets and subsequently forwarding the received data packets in the upstream path from the User Equipment  42  to the network  51  is distinct. At each network node, due to the tree structure, only one data path is available to a network node one level higher in hierarchy. In contrast, in the downstream path from the network  51  to the User Equipment  42 , at each network node a decision has to be made on which link the data packet  30  that is received by the network node is forwarded in order to provide it to the right receiving User Equipment  42 . This decision is made based on a forwarding table, which is generated in the upstream path as described below. 
       FIG. 5  schematically depicts a method for forwarding data packets in a connectionless bearer service between a User Equipment  42  and a Packet Data Network Gateway  48 , which is connected to an external network  50  and for forwarding data packet between the Packet Data Network Gateway  48  and the User Equipment  42 . A data packet  30  originating from a User Equipment  42  is received  52  in a network node  44 ,  46 ,  48 . The data packet  30  comprises a virtual access network identifier  32  describing a virtual access network  43   a ,  45   a ,  47   a ,  49   a ;  43   b ,  45   b ,  47   b ,  49   b ;  43   c ,  45   c ,  47   c ,  49   c . The data packet further comprises an access source address  33  and an access destination address  34 . In step  53 , the virtual access network identifier  32 , the virtual access source address  33  and the virtual access destination address  34  are extracted from the data packet  30 . In step  54 , a forwarding table is established in the network node  44 ,  46 ,  48  or if the forwarding table already exists in the network node  44 ,  46 ,  48 , a new data entry is added to the forwarding table. The forwarding table is dedicated to at least one virtual access network which is identified by the virtual access network identifier  32 . The forwarding table at least contains information about the source address  33  from which a data packet  30  originates in the upstream, which is the destination address of downstream data packets. Further, the forwarding table at least contains a corresponding logical link (port) on which the data packet  30  has been received, which is the link on which downstream data packets will be sent if they have the corresponding destination address. This information is tied to a virtual access network and hence associated to a corresponding virtual access network identifier  32 . In one embodiment, for each virtual access network a forwarding table is established in a network node  44 ,  46 ,  48  including the virtual access network identifier  32 , the address information and the link information as described above. In one embodiment, only one forwarding table is generated in a network node  44 ,  46 ,  48  including the above mentioned information for all virtual access networks which are present in the network node  44 ,  46 ,  48 . In step  55 , a data packet  30  is forwarded upstream to a network node  44 ,  46 ,  48  one level higher in hierarchy. In step  56 , a data packet  30  is received from a network node  44 ,  46 ,  48  one level higher in hierarchy. The access destination address  34  of the data packet  30  is extracted in step  57 . In step  58 , preferably by using the virtual access network identifier, it is determined if this access destination address  34  is available in a forwarding table of a virtual access network of the network node  44 ,  46 ,  48 . If the access destination address  34  is available in the forwarding table of the network node  44 ,  46 ,  48 , the corresponding link is determined and the data packet  30  is forwarded on this link in step  59 . If the access destination address  34  is not available, the data packet  30  is broadcast to all links in the direction to network nodes  44 ,  46 ,  48  on a lower hierarchy level. This way, it is ensured that the data packet  30  is provided to the right link, even if it is also provided to links which would not be necessary. This enhances data traffic only for the exceptional case, as in most cases the link would be available in the forwarding table of a network node  44 ,  46 ,  48  due to previous uplink communication. Each network node  44 ,  46 ,  48  between a source and a sink of a virtual access network establishes and manages a forwarding table as described above. As each virtual access network is organized as a tree structure and no loops are present, upstream communication is easily possible within the virtual access network just by forwarding a data packet  30  to the corresponding network node  44 ,  46 ,  48  in the same virtual access network one hierarchy higher, and at the same time a forwarding table is generated for downstream forwarding in the virtual access network. According to one embodiment, the forwarding information which was not used for a certain time is deleted from the forwarding table, as it can be assumed that this link is not further used in the next future. The information is again included in the forwarding table, if a further corresponding upstream request is received at the corresponding network node  44 ,  46 ,  48 . 
       FIG. 6  depicts a schematic view on a connectionless bearer service. An end-to-end connection between a User Equipment  1  and sink in the external network  5  is depicted as end-to-end bearer  21 . It is provided by an Evolved Packet switched System bearer (EPS-bearer)  22  and an external bearer  23  providing connection to an external network  5 , e.g. the Internet. An EPS-bearer  22  uniquely identifies traffic flows that receive a common Quality of Service (QoS) treatment between a User Equipment  1  and a Packet Data Network Gateway  4 . The EPS-Bearer  22  is a virtual connection between the User Equipment  1  and the Packet Date Network Gateway  4 , which identifies data sent and received between these two end points with specific QoS attributes, e.g QCI, GBR, Allocation Retention Priority. This corresponds to the connection oriented bearer service as described with regard to  FIG. 2 . Further, in  FIG. 6  a connectionless bearer  61  is illustrated which is based on a connectionless tunnel protocol. According to the connectionless tunnel protocol, data packets  30  are forwarded from the User Equipment  1  to the Packet Data Network Gateway  4 . From there, the data packets  30  are forwarded to the external network, e.g. the Internet. 
       FIG. 7  illustrates a further embodiment of a connectionless bearer service. The radio bearer  26  between User Equipment  1  and the base station  2  is realized as known in the art, i.e. with a 4G or 5G connection oriented radio link. A connectionless tunnel protocol as described above provides a connectionless bearer  71  between the base station  2  and the Packet Data Network Gateway  4 . 
       FIG. 8  illustrates a further embodiment of a connectionless bearer service. A connectionless tunnel protocol provides a connectionless bearer  81  between the User Equipment  1  and the Serving Gateway  3 . The data packets  30  are then transported by the S5/S8 Bearer  25  of an EPS bearer  22  between the Serving Gateway  3  and the Packet Data Network Gateway  4 . 
       FIG. 9  schematically depicts a network node  80  that may be used in embodiments of the invention. The network node  80  is configured to forward data packets in a connectionless bearer service. The network node  80  comprises a receiver  81 , a source address analyser  83 , a memory  85  and a transmitter  87 . 
     The receiver  81  is configured to receive a data packet, the data packet comprising user data and header data as described above with respect to data packet  30 . The header data thus comprises at least a virtual access network identifier, wherein the virtual access network identifier is a unique identifier extending across virtual networks and defines a unique virtual access network for the connectionless bearer service. The virtual access network defines a unique data path from a source to a destination of the data packet and vice versa. 
     The source address analyser  83  is configured for analysing the source of a data packet according to the header data of the data packet, the source being upstream from the network node  80 . The source address analyser  83  may take the form of a processor or may be part thereof. Such processor may be a single dedicated processor, a single shared processor, a plurality of individual processors, some of which may be shared, or may be realized with hardware logic optimized for the purposes of embodiments of the invention. 
     The memory  85  is configured to store a forwarding table. The forwarding table indicates the network node a received data packet shall be forwarded to. For downstream packets the forwarding table indicates the network node one level lower in the hierarchy of the virtual access network from which a data packet with a certain source address was received. The forwarding table is indexed by source addresses of data packets received in upstream. 
     A transmitter  87  configured to send a data packet to a network node one level lower in hierarchy of the virtual access network does this according to the information stored in the forwarding table. A transmitter  87  configured to send a data packet upstream just forwards packets received from any receiver configured to receive upstream data packets. For this it might use a default entry in the forwarding table. 
     The functions of the various elements shown in the Figures, including any functional blocks, may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, the functions may be provided, without limitation, by digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non volatile storage. Other hardware, conventional and/or custom, may also be included.