Optimized user equipment supporting relay communication, and related method

Abstract

The invention relates to a method for relaying a communication in a network, wherein a user equipment (UER) relays a communication between a network node entity (eNB) and a target entity (UET), the method including the steps, generating a logical channel at least between the user equipment relay (UER) and the target entity (UET), and assigning at least one identifier (LC_ID_R) to said logical channel, and upon reception from the network node entity (eNB), at the user equipment relay (UER), of data received with said identifier (LC_ID_R), the user equipment relay (UER) forwards the received data to the target entity (UET).

Claims

1. A method, performed by a first user equipment configured to support relay communication between a network node entity and a second user equipment, the method comprising: receiving, from the network node entity, information which comprises a first Layer 2 identifier to identify a connection between the network node and the first user equipment which supports relay communication; mapping the first Layer 2 identity to a second Layer 2 identity, wherein the second Layer 2 identity identifies a direct link between the first user equipment which supports relay communication and the second user equipment; and communicating with the second user equipment based on the second Layer 2 identity.

2. The method of claim 1, wherein the first Layer 2 identity is a source Layer 2 ID that identifies a sender of data in communication via the direct link.

3. The method of claim 1, wherein the second Layer 2 identity is a destination Layer 2 ID that identifies a destination of data sent in communication via the direct link.

4. The method of claim 1, wherein the first user equipment, configured to perform relay communication, also is configured to provide end-to-end service between the first user equipment and a core network.

5. A first user equipment configured to support relay communication between a network node entity and a second user equipment, the first user equipment comprising: a transceiver circuit configured to receive, from the network node entity, information which comprises a first Layer 2 identity to identify a connection between the network node and the first user equipment which supports relay communication; and a processor to map the first Layer 2 identity to a second Layer 2 identity, wherein the second Layer 2 identity identifies a direct link between the first user equipment which supports relay communication and the second user equipment, wherein the transceiver circuit is further configured to communicate with the second user equipment based on the second Layer 2 identity.

6. The first user equipment which supports relay communication of claim 5, wherein the first Layer 2 identity corresponds to a source Layer 2 ID that identifies a sender of data in communication via the direct link.

7. The first user equipment which supports relay communication of claim 5, wherein the second Layer 2 identity corresponds to a destination Layer 2 ID that identifies a destination of data sent in communication via the direct link.

8. The user equipment configured to support relay communication of claim 5, wherein the first user equipment, configured to perform relay communication, also is configured to provide end-to-end service between the first user equipment and a core network.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements and in which:

(2) FIG. 1 represents a conventional network according to the prior art;

(3) FIG. 2 represents a conventional radio interface protocol;

(4) FIG. 3 represents LTE/UMTS sub-layers of layers 2 and 3;

(5) FIG. 4 represents radio bearers used for communications;

(6) FIG. 5 illustrates the path of data during a relay;

(7) FIG. 6 is a flowchart representing the steps of a method for configuration of a relay according to an embodiment of the invention;

(8) FIG. 7 represents the data relaying according to an embodiment of the invention;

(9) FIG. 8A is a flowchart representing the configuration of a relay in a general case;

(10) FIG. 8B is a flowchart representing the configuration for NAS signalling of a relay in an above MAC case;

(11) FIG. 8C is a flowchart representing the configuration for NAS signalling of a relay in an above RLC case;

(12) FIG. 9A is a flowchart representing the configuration for data relaying of a relay in a general case;

(13) FIG. 9B is a flowchart representing the configuration for data relaying of a relay in an above MAC case;

(14) FIG. 9C is a flowchart representing the configuration for data relaying of a relay in an above RLC case;

(15) FIG. 10A is a flowchart representing data relaying in an above MAC case in the downlink direction;

(16) FIG. 10B is a flowchart representing data relaying in an above RLC case in the downlink direction;

(17) FIG. 11 is a flowchart representing data relaying in an above MAC case in the uplink direction.

DESCRIPTION OF EMBODIMENTS

(18) Referring to FIG. 4, a network node entity such as for example a base station (an evolved NodeB (eNB) for example in a LTE network) is establishing a bearer configuration for a user equipment UER to be used as a relay between the network node entity eNB and a target entity UET which can be a user equipment or a relay node (for example another UE relay, or a base station).

(19) When the target UET needs the relay of the relay UER, radio bearers (RB) have to be adapted in order to carry out control and transmit user data from the eNB to the UET (in the downlink case) or from the UET to the eNB (in the uplink case). In the following description, the downlink case will be described but the same reasoning can be symmetrically applied for the uplink case.

(20) In an embodiment, the relay is fulfilled by creating two radio bearers: one radio bearer between UET and UER and one radio bearer between UER and eNB. These bearers are relayed in UER. The relay can be processed in the Packet Data Convergence Protocol (PDCP) sub-layer (the higher sub-layer included in layer 2) or in the Radio Link Control (RLC) sub-layer.

(21) UER relays UET to eNB traffic either above the Media Access Control (MAC) sub-layer, or above the Radio Link Control (RLC) sub-layer (both of these sub-layers are included in so-called Layer 2 (L2)). The security of the traffic is ensured by the end to end PDCP layer between UET and eNB. Therefore, users cannot have access to the relayed data because these data do not reach layers 4 to 7 (application layers being easier to access).

(22) Usually (in the case of a mere communication between an eNB and a UER without relay), some messages are dedicated to establish the communication between the eNB and a user equipment. For example, Radio Resource Control (RRC) signaling messages are usually used for connection establishment and release or for radio bearer establishment/reconfiguration and release. Therefore, RRC signaling messages are inter alia used for the establishment and reconfiguration of radio bearers between an eNB and a UE.

(23) In an embodiment, RRC signaling messages are used to establish, configure or reconfigure radio bearers used for the relay. These radio bearers will carry the communication between the eNB and the UER and between the UER and the UET.

(24) As the UER is a not a dedicated device only used for relaying, RRC signaling messages have to be modified for the UER so that the UER can interpret that it will have to process as a relay for some radio bearers. Therefore, new information element has to be added in the RRC signaling messages. For example, the new information elements can be included in the eNB to UER RRC Connection Reconfiguration message.

(25) FIG. 4 highlights differences between the usual use of radio bearers without relay (UER<->network c-plane and u-plane in FIG. 4) and the use of radio bearers with the relay of UER (UET<->network c-plane & u-plane in FIG. 4).

(26) When the relay is processed, the radio bearer used between the eNB and the UER contains added information in order to perform the relay. As specified above, the establishment of the radio bearers can be processed by adding new information in the RRC signaling message. As the RRC handles the control plane signaling of Layer 3, the establishment of the radio bearers for the relay is processed by a layer 3 protocol. The establishment is processed at layer 3 but the relay of data is processed at layer 2, optionally above the MAC sub-layer or above the RLC sub-layer, according to two alternative implementations described below.

(27) FIG. 5 shows the path of data relayed through UET, UER and eNB layers. As previously described, the data are relayed above MAC or above RLC sub-layers (represented in dotted line in FIG. 5).

(28) Before any relaying, signaling information between UEs has to be set up so as data related to UET can be conveyed via a relay UER. For example, the signaling information can be related to a signaling radio bearer.

(29) In an embodiment, the configuration of the relay is processed in two steps. One step to configure the mapping for data relaying towards UET and one step to configure radio bearers used to carry those data.

(30) FIG. 6 represents the configuration process to initiate the relay. The mapping step and the radio bearer configuration step are not processed in a specific order: the mapping step can be processed before, after or in the same time as the radio bearer configuration step.

(31) The core network CN initiates the procedure by setting-up a bearer configuration for the eNB. This step fills the field eRAB setup request (eRAB for evolved radio bearer) which is sent to the eNB. For example eRAB setup request includes the eRAB identification and/or the Quality of Service (QoS).

(32) Then, the eNB generates control information needed to configure the relay at UER. This information includes mapping configuration information and radio bearer configuration information. For example: an identifier LC_ID for mapping a logical channel between UER and UET, a radio bearer configuration parameters set UER-UET RB config for a configuration of a radio bearer between UER and UET and a radio bearer configuration parameters set UER-eNB RB config for a configuration of a radio bearer between UER and eNB, can be generated.

(33) Then, those data are sent to UER.

(34) Then, UER performs the logical channel mapping and the radio bearer configuration. For example, an identifier LC_ID_R can be assigned to the logical channel between eNB and UER so as to designate the logical channel between UER and UET having the identifier LC_ID. These identifiers LC_ID_R and LC_ID are included in a RRC signaling message, providing thus information to perform the logical channels mapping. The UER-UET RB configuration and UER-eNB configuration parameters in the RRC signaling message further provide information for the radio bearers configuration.

(35) After the configuration, the data relaying can be performed through UER layer 2.

(36) It should be understood that the identifier LC_ID can designate the logical channel between UER and UET but the identifier LC_ID_R, when received at UER with data from eNB and intended to UET, is interpreted by UER as designating the logical channel between UER and UET, for forwarding the received data. Reversely, the identifier LC_ID_R can designate the logical channel between UER and eNB but the identifier LC_ID, when received at UER with data from UET and intended to eNB, is interpreted by UER as designating the logical channel between UER and eNB, for forwarding the received data.

(37) In brief, referring to FIG. 6, in a first step S1, the core network CN defines a setup of the radio bearers configuration and sends to the eNodeB (eNB) a request Req for a eRAB setup.

(38) Upon reception of the request Req, in a second step S2, the eNB generates: the identifiers LC_ID_R and LC_ID, for the logical channels mapping, the parameters set UER_UET RB config, for the configuration of the radio bearer between the target entity UET and the relay entity UER, and the parameters set UER_eNB RB config, for the configuration of the radio bearer between eNB and the relay entity UER.

(39) The identifier and the parameters sets are then sent to the relaying entity UER (arrow referenced Param in FIG. 6), for example in the content of a message such as an RRC Connection Reconfiguration message (RRC for Radio Resource Control). Advantageously, the kind of such a message already exists and the invention can be implemented without any need of deep modifications. In step S3, the relaying entity UER performs the mapping of a logical channel between the UER and the UET, this logical channel having an identifier LC_ID. Moreover, radio bearers are configured between the target entity and the relay entity (UER-UET RB), and between the eNodeB and the relay entity (UER-eNB RB).

(40) After this configuration, the system is designed so that data to be transferred between the eNB and the target UET are relayed through the relay UER as described hereafter and shown on FIG. 7.

(41) FIG. 7 depicts the data relaying. Layer 2 (L2) is subdivided in three sub-layers: respectively PDCP, RLC and MAC sub-layers.

(42) At each level, two entities (eNB and UER for example) interact by means of layer protocol (PDCP, RLC or MAC protocol) by transmitting Protocol Data Units (PDU). This transmission is an abstraction in fact (actually, data is encapsulated through lower layers to be physically transmitted through the physical layer, e.g. layer 1).

(43) In an embodiment, data is relayed above the MAC sub-layer. This means that MAC PDUs are forwarded at the RLC sub-layer level.

(44) In another embodiment, data is relayed above the RLC sub-layer. This means that RLC PDUs are forwarded at the PDCP sub-layer level. This embodiment is represented by dotted lines in FIG. 7.

(45) In both cases, data are mapped: thanks to the identifier LC_ID_R between UER and eNB, and thanks to the identifier LC_ID between UER and UET.

(46) As the configuration steps S1, S2, S3 provide the mapping configuration explained above, the relay entity UER is able to interpret that data identified by LC_ID_R are to be forwarded to the target entity UET (which can be a terminal in the network, or another relay node for hoping a communication through several relay nodes for example).

(47) In an embodiment, the UER is used for relaying of Non-Access Stratum (NAS) signaling with the UET. Non-Access Stratum signaling allows mobility of the UE through different nodes. In such an embodiment, the UET is signaled even if it is out of eNB range.

(48) As described above, relay can be done above MAC sub-layer or above RLC sub-layer. FIG. 8A globally depicts relay of NAS signaling and FIGS. 8B and 8C respectively describe the above MAC and above RLC case. These Figs. provide details for implementation of the present invention, particularly for implementation with respect to 3GPP LTE standard.

(49) In FIG. 8A, a Mobility Management Entity (MME), which can be part of the core network CN for LTE, sets up the bearer configuration. This set-up allows the transmission of NAS PDU (NAS is a layer 3 sub-layer). With such information, the UER provides the mapping configuration and the radio bearer configuration for the relay (CONFIG in FIG. 8A). This step allows adaptation of RRC Connection Reconfiguration for relay which includes new information element (NIE).

(50) FIGS. 8B and 8C point out differences between above MAC relaying and above RLC relaying. In the 3GPP LTE implementation, this difference is particularly visible in the (UER-UET) SRB(2) config field.

(51) In a further embodiment, relaying is performed because the UET has requested communication towards the network via the UER or because the UET, while communicating with the network, has moved out of coverage of the network. As described above, relaying can be done above the MAC sub-layer or above the RLC sub-layer. FIG. 9A globally shows the configuration procedure for the relay of data and FIGS. 9B and 9C respectively show the above MAC and the above RLC cases. These Figs. provide details for implementation of the present invention, particularly for implementation with respect to 3GPP LTE standard. FIGS. 9B and 9C point out differences between above MAC relaying and above RLC relaying. In the 3GPP LTE implementation, this difference is particularly visible in the (UER-UET) RB config field.

(52) FIGS. 10A and 10B respectively describe a possible implementation to perform data relaying in the above MAC case and in the above RLC case. A Service Data Unit (SDU) is a specific unit of data that has been passed down from an OSI layer to a lower layer, and which the lower layer has not been encapsulated yet into a protocol data unit (PDU). As MAC sub-layer is a lower sub-layer than RLC sub-layer, MAC PDU is included in RLC PDU. Flags are included in MAC PDU for the UER to relay data.

(53) In FIGS. 10A to 11, FLAG 2 is used to indicate to UER that MAC data contained in this MAC PDU are intended to the UET via relay. FLAG 1 is the usual flag used without relay so that the UET receives data contained in MAC PDU as if these data come directly from the eNB. As previously described, data are mapped thanks to FLAG 2 between the UER and the eNB and thanks to FLAG 1 between the UER and the UET. As the configuration steps provide the mapping configuration, the UER is able to interpret and simply forward data identified by FLAG 2. These Figs. provide details for implementation of the present invention, particularly for implementation with respect to 3GPP LTE standard. FIG. 11 provides details for implementation of the present invention in the uplink case, particularly for implementation with respect to 3GPP LTE standard.

(54) Therefore, in brief, the present invention proposes, in an embodiment, to provide the Radio Access Network (RAN) with a logical channel mapping configuration along with radio bearers configuration for data relaying towards a target entity UET with the use of a relay entity UER. In an embodiment, the invention provides additional information meaning that the radio bearers configuration is performed for relaying purpose (addition of an identifier LC_ID for example). Such information, at least, can be included in a pre-existing RRC Connection Reconfiguration message (RRC for Radio Resource Control).

(55) In an embodiment, the invention provides an above MAC (plain line of FIG. 7) or an above RLC (dashed line of FIG. 7) data relaying configuration, according to a choice of optimization which can be, for example, decided at first in the network. Of course, such a choice can depend also on the relay entity capacities and/or construction.

(56) Furthermore, if RAN does not provide any above RLC configuration, then the UER can perform above MAC data relaying. This choice of implementation in the UER can be dictated by the radio bearer quality of service.

(57) For the downlink direction, the relay entity UER forwards the data received on a logical channel flagged with a specific identifier (for example LC_ID as previously described) to a next hop logical channel as per a logical channel mapping configuration previously defined. Unless configured by the network as described above, above RLC or above MAC data relaying can be an option according to the UER capacities and/or construction, as indicated above. If UER performs above RLC data relaying, then PDCP data is conveyed from UER to a next hop UET (which can be a relay for a further target). If UER performs above MAC data relaying, then RLC data is conveyed to next hop UET.

(58) For the uplink direction, the UER transparently (i.e. without decoding) forwards the data received on the logical channel towards the network using the logical channel identified with a specific identifier (LC_ID for example) of the configured relay bearer as per the previously received logical channel mapping configuration.

(59) Of course, a same UE can relay several communications. Therefore, several identifiers LC_ID can be used to that end (with a logical channel for each UE target to be reached). Moreover, a same communication can be relayed by several UEs (generating several successive logical channels) and several identifiers LC_ID can be used to that end also.

(60) The present invention can also be embedded in a computer program product, which includes all the features enabling the implementation of the methods described herein, and which, when loaded in an information processing system (for example in a user equipment UER), causes the information processing system. Computer program means or computer program in the present context mean any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after the conversion to another language. Such a computer program can be stored on a computer or machine readable medium allowing data, instructions, messages or message packets, and other machine readable information to be read from the medium. The computer or machine readable medium may include non-volatile memory, such as ROM, Flash memory, Disk drive memory, CD-ROM, and other permanent storage. Additionally, a computer or machine readable medium may include, for example, volatile storage such as RAM, buffers, cache memory, and network circuits. Furthermore, the computer or machine readable medium may include computer or machine readable information in a transitory state medium such as a network link and/or a network interface, including a wired network or a wireless network, that allow a device to read such computer or machine readable information.

(61) Expressions such as comprise, include, incorporate, contain, is and have are to be construed in a non-exclusive manner when interpreting the description and its associated claims, namely construed to allow for other items or components which are not explicitly defined also to be present. Reference to the singular is also to be construed in be a reference to the plural and vice versa.

(62) While there has been illustrated and described what are presently considered to be the preferred embodiments of the present invention, it will be understood by those skilled in the art that various other modifications may be made, and equivalents may be substituted, without departing from the true scope of the present invention. Additionally, many modifications may be made to adapt a particular situation to the teachings of the present invention without departing from the central inventive concept described herein. Furthermore, an embodiment of the present invention may not include all of the features described above. Therefore, it is intended that the present invention not be limited to the particular embodiments disclosed, but that the invention include all embodiments falling within the scope of the invention as broadly defined above.

(63) A person skilled in the art will readily appreciate that various parameters disclosed in the description may be modified and that various embodiments disclosed and/or claimed may be combined without departing from the scope of the invention.

INCORPORATION BY REFERENCE

(64) This application is based upon and claims the benefit of priority from European Patent Application No. EP 12306301.8, filed on Oct. 19, 2012, the disclosure of which is incorporated herein in its entirety by reference.