HK1237575B - Network-initiated discovery and path selection procedures for multi-hop underlay networks - Google Patents

Description

Network-initiated discovery and path selection procedures for multi-hop infrastructure networks

Priority Declaration

This application claims the benefit of priority to U.S. patent application serial number 14/729,511, filed on June 3, 2015, which claims the benefit of priority to U.S. provisional application serial number 62/097,456, filed on December 29, 2014, both of which are incorporated herein by reference in their entireties.

Technical Field

Embodiments relate to wireless communications. Some embodiments relate to user equipment (UE)-evolved Node B (eNodeB) signaling information.

Background Art

Wireless mobile devices or user equipment (UE) can communicate with each other using radio access technologies such as the 3GPP Long Term Evolution ("LTE") standard, 3GPP LTE Advanced Release 12 (March 2014) ("LTE-A standard"), the IEEE 802.16 standard, IEEE Std. 802.16-2009, published May 29, 2009 ("WiMAX"), and any other wireless protocols designated as 3G, 4G, 5G, and beyond. Technologies such as device-to-device (D2D), sensor networks, or the Internet of Things (IoT) (which describes uniquely identifiable embedded computing devices interconnected within an Internet infrastructure) can utilize user equipment (UE) that includes constrained coverage capabilities and, therefore, may limit connectivity to a corresponding eNodeB.

Summary of the Invention

According to one aspect of the present disclosure, a user equipment (UE) configured to operate as a relay node is provided, comprising: a receiver circuit configured to: receive a notification of a request to establish a multi-hop transmission path that communicatively couples a base station and an endpoint UE; and receive a first message including a first reference signal from a first network node; and a transmitting circuit configured to transmit a second message to a second UE, wherein the second message includes a second reference signal different from the first reference signal and measurement information of the transmission path from the first network node to the user equipment UE, for use by the second network node to determine whether to select the transmission path from the first network node to the user equipment UE as at least part of the multi-hop transmission path.

According to another aspect of the present disclosure, a processing circuit is provided for use by a user equipment UE, the processing circuit comprising: an operating mode circuit for configuring the user equipment UE to operate as a relay node, including in response to a notification of a request to establish a multi-hop transmission path that communicatively couples a base station and an endpoint UE; a signal processing circuit for determining measurement information of a transmission path from a first network node to the user equipment UE based at least in part on a first reference signal included in a first message received from the first network node; and a message generation circuit for generating a second message transmitted to a second UE, the second message including a second reference signal different from the first reference signal and the determined measurement information, for use by the second network node to determine whether to select the transmission path from the first network node to the user equipment UE as at least part of the multi-hop transmission path.

According to another aspect of the present disclosure, there is provided an apparatus for use by a relay user equipment (UE), the apparatus comprising: a device for receiving a first message from a network node, the network node comprising a base station or a second relay UE communicatively coupled to the base station, the first message comprising a first reference signal, the first reference signal comprising a predetermined signal value stored at both the relay user equipment UE and the network node; and a device for transmitting a second message to a third UE, the second message comprising: a second reference signal comprising a predetermined signal value stored at both the relay user equipment UE and the third UE; and measurement information of a transmission path from the base station to the relay user equipment UE, the measurement information comprising at least one of a signal power loss of the transmission path from the base station to the relay user equipment UE, and/or a network traffic load of the transmission path from the base station to the relay user equipment UE, wherein the measurement information of the transmission path from the base station to the relay user equipment UE is for use by the second network node to determine whether to select the transmission path from the base station to the relay user equipment UE as at least part of a multi-hop transmission path communicatively coupling the base station and an endpoint UE.

According to another aspect of the present disclosure, a user equipment UE is provided for selecting from multiple transmission paths leading to a base station, the user equipment comprising: a transceiver circuit configured to: receive a first message from a first relay UE, the first message comprising a first reference signal, and first transmission path information comprising path information of a first transmission path, the first transmission path comprising a path from the base station to the first relay UE; and transmit a path communication request for the selected transmission path to the base station; and a processing circuit configured to: determine direct transmission path information of a direct transmission path from the base station to the user equipment UE; and select from the direct transmission path or a multi-hop transmission path based at least in part on a comparison of the direct transmission path information with the first transmission path information, the multi-hop transmission path comprising a path for communicatively coupling the user equipment UE to the base station through one or more relay UEs including the first relay UE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 illustrates the architecture of a wireless network with various network components according to some embodiments.

FIG2 illustrates an architecture of components of an LTE network according to some embodiments.

3 is an illustration of a multi-hop transmission configuration according to some embodiments.

4 is a diagram of a communication process for establishing a multi-hop transmission path, according to some embodiments.

5A is a flow diagram of a process performed by a relay UE in establishing a multi-hop transmission path according to some embodiments.

FIG5B illustrates a discovery period in which a network node transmits a discovery signal according to some embodiments.

FIG6 is a flow diagram of a process for establishing a multi-hop transmission path for a terminal UE according to some embodiments.

FIG7 shows a block diagram of a user equipment and an eNodeB according to some embodiments.

8 is a block diagram illustrating machine components according to some exemplary embodiments that can read instructions from a machine-readable medium and perform any one or more of the methodologies discussed herein, in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

The following description and accompanying drawings fully illustrate specific embodiments so that those skilled in the art can practice them. Other embodiments may incorporate structural, logical, electrical, method and other changes. Parts and features of some embodiments may be included in or replaced by those of other embodiments.

Embodiments set forth in the claims encompass all available equivalents of those claims.

In some embodiments, the mobile device or other device described herein may be part of a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capabilities, a web tablet, a wireless phone, a smart phone, a wireless headset, a pager, a wearable mobile computing device (e.g., a mobile computing device included in a wearable housing), an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), or other devices that can wirelessly receive and/or transmit information. In some embodiments, the mobile device or other device may be a user equipment (UE) or evolved Node B (eNodeB) configured to operate according to a 3GPP standard (e.g., 3GPP Long Term Evolution ("LTE") Advanced Release 12 (March 2014) ("LTE-A standard"). In some embodiments, the mobile device or other device may be configured to operate according to other protocols or standards, including IEEE 802.11 or other IEEE and 3GPP standards. In some embodiments, a mobile device or other device may include one or more of the following: a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be a liquid crystal display (LCD) screen including a touch screen.

FIG1 illustrates the architecture of a wireless network with various network components according to some embodiments. System 100 is shown as including UE 102 and UE 104. UE 102 and UE 104 are shown as smartphones (i.e., handheld touch-screen mobile computing devices that can connect to one or more cellular networks), but may also include PDAs, pagers, laptop computers, desktop computers, etc.

UEs 102 and 104 are configured to access a radio access network (RAN) 106 via connections 120 and 122, respectively, each of which includes a physical communication interface or layer; in this example, connections 120 and 122 are shown as air interfaces for enabling communication coupling and can be consistent with a cellular communication protocol, such as a Global System for Mobile Communications (GSM) protocol, a Code Division Multiple Access (CDMA) network protocol, a Push-to-Talk (PTT) protocol, a PTT over a cellular network (POC) protocol, a Universal Mobile Telecommunications System (UMTS) protocol, a 3GPP LTE protocol, or the like.

The RAN 106 may include one or more access points that enable connections 120 and 122. These access points (described in further detail below) may be referred to as access nodes, base stations (BSs), NodeBs, eNodeBs, etc., and may include ground stations (i.e., terrestrial access points) or satellite access points that provide coverage within a geographic area (i.e., a cell). The RAN 106 is shown communicatively coupled to a core network 110. In addition to bridging circuit-switched calls between UE 102 and UE 104, the core network 110 may be used to enable packet-switched data exchanges with the internet 112. In some embodiments, the RAN 106 may include an evolved UMTS (Universal Mobile Telecommunications System) terrestrial radio access network (E-UTRAN), and the core network 110 may include an evolved packet core (EPC) network.

UE 104 is shown as being configured to access access point (AP) 108 via connection 124. Connection 124 may comprise a local wireless connection (such as a connection consistent with IEEE 802.11), where AP 108 would comprise a Wireless Fidelity (WiFi) router. In this example, AP 108 is shown as being connected to the Internet 112 and not to core network 110.

The Internet 112 is shown as being communicatively coupled to an application server 116. The application server 116 can be implemented as multiple structurally separate servers or can be included in a single server. The application server 116 is shown as being connected to the Internet 112 and the core network 110; in other embodiments, the core network 110 is connected to the application server 116 via the Internet 112. The application server 116 can also be configured to support one or more communication services (e.g., Voice over Internet Protocol (VoIP) sessions, PTT sessions, group communication sessions, social networking services, etc.) for UEs that can connect to the application server 116 via the core network 110 and/or the Internet 112.

Core network 110 is also shown as being communicatively coupled to an Internet Protocol (IP) Multimedia Subsystem (IMS) 114. IMS 114 comprises an integrated network of telecommunications operators that enables packet communications using IP, such as traditional telephony, fax, email, Internet access, VoIP, instant messaging (IM), video conferencing sessions, and video on demand (VoD).

FIG2 illustrates an architecture of components of an LTE network according to some embodiments. In this example, (sub)system 200 includes an Evolved Packet System (EPS) on an LTE network, and therefore includes an E-UTRAN 210 and an EPC network 220 communicatively coupled via an S1 interface 215. In this illustration, only a portion of the components of E-UTRAN 210 and EPC network 220 are shown. Some elements described below may be referred to as "modules" or "logic." As used herein, "module" or "logic" may describe hardware (such as circuitry), software (such as program drivers), or a combination thereof (such as a programmed microprocessor unit).

The E-UTRAN 210 includes eNodeBs 212 (which may operate as base stations) for communicating with one or more UEs (e.g., UE 102). The eNodeBs 212 are shown in this example to include macro eNodeBs and low power (LP) eNodeBs. Any eNodeB 212 may terminate the air interface protocol and may be the first point of contact for the UE 102. In some embodiments, any eNodeB 212 may perform various logical functions of the E-UTRAN 210, including, but not limited to, radio network controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. eNodeBs in EPS/LTE networks, such as eNodeB 212, do not utilize a separate controller (i.e., RNC) to communicate with the EPC network 220; in other embodiments utilizing other standardized protocols, the RAN may include an RNC to enable communication between the BS and the core network.

According to some embodiments, UE 102 may be configured to communicate with any eNodeB 212 using orthogonal frequency division multiplexing (OFDM) communication signals over a multi-carrier communication channel according to various communication techniques, such as orthogonal frequency division multiple access (OFDMA) communication techniques or single-carrier frequency division multiple access (SC-FDMA) communication techniques, although the scope of the embodiments is not limited in this respect. An OFDM signal may include multiple orthogonal subcarriers.

According to some embodiments, UE 102 may be configured to determine a synchronization reference time based on receiving one or more signals from any eNodeB 212. UE 102 may also be configured to support device-to-device (D2D) communications with other UEs using OFDMA, SC-FDMA, or other multiple access schemes.

The S1 interface 215 is an interface that separates the E-UTRAN 210 from the EPC network 220. It is divided into two parts: S1-U, which transmits service data between the eNodeB 212 and the Serving Gateway (S-GW) 224; and S1-MME, which serves as a signaling interface between the eNodeB 212 and the Mobility Management Entity (MME) 222. The X2 interface is an interface between eNodeBs 212. The X2 interface may include two parts (not shown): X2-C and X2-U. X2-C is a control plane interface between eNodeBs 212, while X2-U is a user plane interface between eNodeBs 212.

Low-power cells can be used in cellular networks to extend coverage to indoor areas where outdoor signals don't reach well, or to increase network capacity in areas with very dense phone usage, such as train stations. As used herein, the term "LP eNodeB" refers to any suitable relatively low-power eNodeB for implementing narrower cells (i.e., narrower than macrocells), such as femtocells, picocells, or microcells at the edge of the network. Mobile network operators typically provide femtocell eNodeBs to their residential or enterprise customers. Femtocells are typically the size of a residential gateway or smaller and are typically connected to the user's broadband line. Once plugged in, the femtocell connects to the mobile operator's mobile network and provides additional coverage to the residential femtocell, with a range of typically 30 to 50 meters. Therefore, an LP eNodeB can be a femtocell eNodeB because it is coupled through a packet data network gateway (PGW) 226. Similarly, picocells are wireless communication systems that typically cover small areas, such as inside buildings (offices, shopping malls, train stations, etc.), or more recently, on airplanes. Through its base station controller (BSC) functionality, a picocell eNodeB can typically connect to another eNodeB (such as a macro eNodeB) via an X2 link. Thus, a low-end eNodeB can be implemented as a picocell eNodeB, as it is coupled to the macro eNodeB via the X2 interface. A picocell eNodeB or other low-end eNodeB can incorporate some or all of the functionality of a macro eNodeB. In some cases, this may be referred to as an AP BS or enterprise femtocell.

In some embodiments, a downlink resource grid can be used for downlink transmissions from any eNodeB 212 to UE 102, while uplink transmissions from UE 102 to any eNodeB 212 can utilize similar techniques. The grid can be a time-frequency grid, referred to as a resource grid or time-frequency resource grid, which serves as the physical resources in the downlink in each time slot. This time-frequency plane representation is a convention in OFDM systems, making it intuitive for radio resource allocation. Each column and row of the resource grid corresponds to an OFDM symbol and an OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one time slot in a radio frame. The smallest time-frequency unit in the resource grid is denoted as a resource element. Each resource grid includes multiple resource blocks, which describe the mapping of certain physical channels to resource elements. Each resource block includes a collection of resource elements; in the frequency domain, this represents the minimum amount of resources that can currently be allocated. There are several different physical downlink channels that are transmitted using such resource blocks.

The physical downlink shared channel (PDSCH) carries user data and higher layer signaling to the UE 102. The physical downlink control channel (PDCCH) carries, among other things, information about the transmission format and resource allocation associated with the PDSCH channel. It also informs the UE 102 about the transmission format, resource allocation, and H-ARQ (Hybrid Automatic Repeat Request) associated with the uplink shared channel. Typically, downlink scheduling (allocation of control and shared channel resource blocks to UEs 102 within a cell) is performed at any eNodeB 212 based on channel quality information fed back from the UE 102 to any eNodeB 212, and downlink resource allocation information is then sent to the UE 102 on a control channel (PDCCH) intended for (allocated to) the UE.

PDCCH uses control channel elements (CCE) to transmit control information. Before being mapped to resource elements, the PDCCH complex symbols are first organized into quadruplets and then permuted using a sub-block interleaver for rate matching. One or more of these CCEs are used to transmit each PDCCH, where each CCE corresponds to nine sets of four physical resource elements called resource element groups (REGs). Four quadrature phase shift keying (QPSK) symbols are mapped to each REG. Depending on the size of the downlink control information (DCI) and the channel conditions, one or more CCEs can be used to transmit the PDCCH. Four or more different PDCCH formats can be defined in LTE, with different numbers of CCEs (e.g., aggregation levels, L=1, 2, 4, or 8).

The EPC network 220 includes an MME 222, an S-GW 224, and a PGW 226. The MME 222 is functionally similar to the control plane of a traditional Serving General Packet Radio Service (GPRS) Support Node (SGSN). The MME 222 manages mobility aspects of access, such as gateway selection and tracking area list management. The S-GW 224 terminates the interface toward the E-UTRAN 210 and routes packets between the E-UTRAN 210 and the EPC network 220. Furthermore, it can be the local mobility anchor point for inter-eNodeB handovers and can also provide an anchor point for inter-3GPP mobility. Other responsibilities include lawful interception, charging, and some policy enforcement.

The S-GW 224 and the MME 222 can be implemented in one physical node or in separate physical nodes. The PGW 226 terminates the SGi interface toward the packet data network (PDN). The PGW 226 routes packets between the EPC network 220 and external networks (e.g., the Internet) and can be a key node for policy enforcement and billing data collection. The PGW 226 and the S-GW 224 can be implemented in one physical node or in separate physical nodes.

Throughout its operation, the UE 102 performs cell selection upon power-up and cell reselection. The UE 102 searches for cells provided by the E-UTRAN 210 (e.g., macro cells or pico cells). During the cell reselection process, the UE 102 can measure the reference signal strength (e.g., reference signal received power/reference signal received quality (RSRP/RSRQ)) of each neighboring cell and select a cell based on this measurement (e.g., selecting the cell with the highest RSRP value). After the UE 102 selects a cell, it can verify the accessibility of the cell by reading the Master Information Block (MIB). If the UE 102 fails to read the MIB for the selected cell, it can discard the selected cell and repeat the above process until a suitable cell is found.

The radio resource control (RRC) state indicates whether the RRC layer of UE 102 is logically connected to the RRC layer of E-UTRAN 210. After UE 102 is communicatively coupled to a cell, its RRC state is RRC_IDLE. When UE 102 has data packets to transmit or receive, its RRC state changes to RRC_CONNECTED. While in the RRC_IDLE state, UE 102 can associate itself with different cells.

When there are a large number of wireless devices in the network, there may be scenarios where the terminal devices are not directly connected to one or more eNodeBs 212. For example, connectivity resources may be limited, or the devices may include coverage-constrained devices - for example, devices that operate primarily for machine-type communication (MTC) or machine-to-machine (M2M) communication (e.g., sensor devices, controller devices, etc.) may have limited coverage capabilities and processing capabilities (similarly, the devices may operate in a coverage-constrained mode to limit power/resource consumption). Multi-hop transmission paths may be used for uplink paths to/downlink paths from the eNodeB 212 to provide connectivity for such devices. In other instances, multi-hop transmission paths may be more efficient or have less network traffic load than direct UE-eNodeB paths, and therefore, multi-hop transmission paths are utilized.

FIG3 is a diagram of a multi-hop transmission configuration according to some embodiments. In this exemplary embodiment, an eNodeB 302 and a relay UE 304 and a UE 306 (in some form of eNodeB/relay UE combination) can be used to provide a multi-hop uplink and/or downlink transmission path to a terminal UE 310 (which may alternatively be referred to as an endpoint UE) that is outside the coverage area of the eNodeB 302. As shown in this diagram, multiple multi-hop transmission paths are included for communicatively coupling the eNodeB 302 to the terminal UE 310: a two-hop path utilizing only the relay UE 304, a two-hop path utilizing only the relay UE 306, and a three-hop path utilizing both the relay UE 304 and the UE 306 in any order. In other embodiments, more relay UEs can be utilized, thereby generating more possible multi-hop transmission paths.

The embodiments of the present disclosure describe processes involving discovery and establishing a multi-hop communication path applicable to (endpoint) UE. As discussed in further detail below, the network-initiated discovery and path selection process can utilize periodically transmitted reference signals and optional auxiliary information. Network nodes (such as eNodeB 302) and other nodes with relay capabilities (such as relay UE 304 and UE 306) can transmit periodic reference signals. Based on these transmitted reference signals and optional auxiliary information, relay UE 304/306, eNodeB 302 and/or terminal UE 310 in any combination can make a selection decision on the previous hop path for communication. Terminal UE 310 or eNodeB 302 can make a selection decision on the end-to-end path so as to provide coverage extension for terminal UE 310 using a multi-hop transmission path.

FIG4 is a diagram of a communication process for establishing a multi-hop transmission path according to some embodiments. The process and logic flow diagrams shown herein provide examples of sequences of various process actions. Although shown in a specific sequence or order, the order of the actions may be modified unless otherwise stated. Therefore, the described and illustrated embodiments should be understood as examples only, and the illustrated processes may be performed in a different order, and some actions may be performed in parallel. Additionally, one or more actions may be omitted in various embodiments; therefore, not all actions are performed in each implementation. Other process flows are possible.

In this embodiment, eNodeB 302 and relay UE 304 and UE 306 are shown transmitting reference signals and link selection assistance information. In this example, eNodeB 302 is shown performing a transmission 402 to relay UE 304 that includes a reference signal and, optionally, link selection information. The reference signal may include a pilot tone transmitted using a predetermined transmit power value, which may be predefined in a standard or known to relay UE 304 upon network entry or at a later time using other messaging (e.g., a dedicated RRC message or a broadcast SIB message). The reference signal may include a periodic signal transmitted by eNodeB 302 and relay UE 304 and UE 306. In some embodiments, the reference signal may be transmitted by a relay UE that is capable of acting as a relay UE (or, in some embodiments, optionally has this capability enabled). The transmitting relay UE may be identifiable from the reference signal. In some embodiments, this can be achieved by defining a specific sequence to be used as a reference signal for a specific relay UE, or the network can assign a specific identity sequence/signature to each relay UE for use with/as a reference signal. In other embodiments, if multiple or all relay UEs use the same or similar reference signal, the relay identity can be sent along with the assistance information described below. The transmission of the reference signal can optionally include link selection assistance information as described below.

In this example, the eNodeB 302 performs transmission 402 of a reference signal and assistance information to the relay UE 304. In some embodiments, the relay UE 304 can be "forced" to act as a relay UE (any appropriate network node can make this decision) via a signal from the eNodeB 302. The network can inform the UE of this forcing using dedicated signaling (e.g., an RRC message), using a multicast message to multiple UEs, a broadcast message (e.g., a SIB (System Information Broadcast) message), etc.

The relay UE 304 processes the information from the transmission 402 (as shown in operation 404) and performs a transmission 406 of a reference signal and assistance information to the relay UE 306. The direct UE-to-UE transmission may be performed, for example, using a D2D procedure. In other embodiments, the relay UE 304 and the UE 306 may function like a simplified version of an eNodeB and thereby utilize LTE downlink communication procedures (e.g., a PDCCH transmission procedure).

In some embodiments, the reference signal and/or assistance information from transmission 402 is also forwarded to relay UE 306. In some embodiments, a UE may determine not to act as a relay for various reasons—e.g., its remaining battery capacity is low, or its computing power is limited; in such cases, the UE may not perform operation 404. Relay UE 306 may perform similar operations (i.e., process the information from transmission 406 (as shown by operation 408), perform transmission 410 of the reference signal and assistance information to terminal UE 310).

The terminal UE 310 processes the received information (as shown in operation 412) and makes a link selection decision (as shown in block 414, although in some embodiments, other nodes make the link selection decision as described in further detail below). For example, the terminal UE 310 may select from: a two-hop path utilizing only the relay UE 304, a two-hop path utilizing only the relay UE 306, or a three-hop path utilizing both the relay UE 304 and the UE 306 in any order. The terminal UE 310 may perform a transmission 416 to inform the eNodeB 302 (directly or through one or more relay UEs) of the selected multi-hop path, and the eNodeB 302 may perform a transmission 418 to establish a data communication path between the eNodeB 302 and the terminal UE 310 using the selected link.

The operations of relay UE 304/306 and terminal UE 310 are described in more detail below. FIG5A is a flow diagram of a process performed by a relay UE when establishing a multi-hop transmission path according to some embodiments. Process 500 includes performing an operation at the relay UE to receive a message from a node including an eNodeB or another relay UE (e.g., block 502); this message includes a reference signal (which includes predetermined signal values stored at both the relay UE and the node) and may also include additional assistance information for the transmission path from the node to the relay UE.

This assistance information can be used to assist in making multi-hop path selection decisions; as described in further detail below, embodiments can perform multi-hop path selection at each relay node in a multi-hop path (referred to herein as a distributed decision), or at the path endpoints (referred to herein as a centralized or semi-centralized decision). The assistance information can represent any combination of metrics of interest, such as the current number of hops to the eNodeB, the potential channel capacity to the eNodeB, the load condition (i.e., the current or expected network traffic load), etc. This assistance information can be transmitted from the relay UE or from the eNodeB (although some metrics of interest (such as the current number of hops to the eNodeB) can be transmitted only by the relay UE). The relay UE can update its assistance information when new reference signals/assistance information is received from other nodes, or when its own parameters have changed (e.g., metrics of interest that are subject to runtime changes, such as load condition or remaining battery capacity).

In some embodiments, the link selection assistance information may be one or more value pairs indicating information type and value as shown in the following (exemplary) Table 1.

Table 1. Example of link selection assistance information

For the relay UE, an operation is performed to determine measurement information of the transmission path from the eNodeB to the relay UE based on the received message (as shown in block 504). This may include updating additional information received from (another) relay UE to include characteristics of the relay UE (e.g., updating the number of hops, path loss, etc.), and if the relay UE is the first hop in the (ultimate) multi-hop transmission path, it may include creating the above link selection assistance information.

Since the relay UE can receive messages from multiple nodes (for example, with reference to FIG3 , the relay UE 306 can receive reference signals from both the eNodeB 302 and the relay UE 304), an operation is performed to determine whether an additional message has been received (as shown in block 506). If an additional message is received, the previous operation is re-executed for each received message. Otherwise, an operation of transmitting a message including a reference signal to another UE (i.e., a relay UE or a terminal UE) may be performed (as shown in block 508). In some embodiments, this message may also include link selection assistance information from the previous hop and assistance information of the relay UE itself. In some embodiments, if multiple messages are received, thereby indicating to the relay UE that there are multiple multi-hop paths, the relay UE may select one of these paths and forward only the information of that path. This decision process is described in more detail below with reference to FIG6 .

When a relay UE performs the operations shown in block 508 of FIG. 5A , there is a possibility of a collision (i.e., two or more relays select the same starting offset or are within each other's reference signal transmission time). The relay UE can avoid collisions of its reference signals by using a listen-before-transmit strategy in order to reduce network interference. For example, if the relay UE determines that a reference signal is being transmitted by a different node at the same time as its scheduled reference signal transmission, or if the relay UE detects a significant increase in interference from a neighboring node, the relay UE can postpone the reference signal transmission. If two or more UEs transmit reference signals at the same time or within each other's transmission time, the reference signals may not be decoded by the intended recipient UE due to the collision. Therefore, the relays involved in the collision or the relays detecting a potential collision may select different random starting offsets for (re)transmitting their reference signals. In some embodiments, the UE may also repeat the reference signal multiple times within the discovery period of the same relay UE to reduce delays and/or improve the reliability of the discovery procedure.

The periodic discovery period of path discovery can be predefined, during which the eNodeB and/or relay UE transmits its reference signal and auxiliary information where applicable. Figure 5B shows a discovery period in which a network node transmits a discovery signal according to some embodiments. The discovery period 550 is shown as a predefined time frame in which the relay UE and the terminal UE can listen to the discovery reference signal. In this embodiment, the duration of the discovery period 550 is less than the time period of the interval between the start of the discovery period 550 and 560 (i.e., the time frame 559 between the discovery period 550 and the start of the discovery period 560), thereby providing a method for reducing power consumption and/or improving the battery life of the relay/terminal UE by limiting the amount of time in which the discovery signals 551-553 are transmitted or expected by the receiving UE in the discovery cycle time frame 559.

A predefined control channel may be used to transmit a reference signal transmitted from a relay UE/eNodeB. Each relay UE/eNodeB may transmit a discovery reference signal after a certain start offset time from the start boundary of the discovery period. In this example, a discovery reference transmission offset 555 for reference signal 551 is shown as included in discovery periods 550 and 560 (other embodiments may utilize more offset values).

In some embodiments, the eNodeB may transmit discovery reference transmission offsets 555, 556, and 557 (other embodiments may utilize more offset values) for reference signals 551, 552, and 553, respectively, to various relay UEs for periodic signaling; the eNodeB may also have an offset value to use for transmitting its discovery signal. In this embodiment, the relay UE may be registered/authenticated with the network before starting the discovery process. The eNodeB may ensure that the offsets for each relay UE are sufficiently far apart in time, or that the relay UEs are using different frequency channels, so that there are no conflicts during the transmission times of the reference signals and (optional) path selection assistance information.

In other embodiments, each relay UE may randomly select its own starting offset for its reference signal transmission. If a collision or potential collision with reference signal transmissions of other relay UEs is detected, the relay UE may randomly reselect another starting offset.

Figure 6 is a flow chart of a process for establishing a multi-hop transmission path for a terminal UE, according to some embodiments. In this embodiment, process 600 includes performing an operation in which the terminal UE receives a message from a relay UE (as shown in block 602); the received message includes a reference signal (which includes predetermined signal values stored at both the terminal UE and the relay UE), and transmission path information including path information for a multi-hop transmission path from an eNodeB to the relay UE. As described above, the multi-hop transmission path may include a multi-relay UE path, and the path information may include specific details about the path (e.g., number of nodes, path loss, etc.).

An operation of determining whether additional messages are received from other relay UEs is performed (as shown in block 604). When no messages remain, the terminal UE determines whether there are multiple paths to be selected based on the messages received from the relay UEs (as shown in block 606).

If there are multiple paths to select, one of the endpoint network nodes performs operations to select a transmission path, as shown in block 608. As described above, the relay UE may process and forward the assistance information in various implementations, and thus the path selection strategy of the terminal UE (or relay UE, if distributed decision making is implemented) may vary in different implementations.

The selected transmission path may include a multi-hop path or a direct path (if available). A multi-hop path may be selected even if a direct eNodeB-end UE path exists. For example, the network traffic load situation on the direct eNodeB-end UE path may be better/favorable than on the multi-hop transmission path, or the multi-hop path may be more power efficient; for example, the endpoint UE may have limited power resources, whereby connecting to a nearby relay UE with sufficient power resources will utilize less power for the endpoint UE.

In some embodiments, each UE (i.e., relay UE or terminal UE) selects only the node immediately preceding it. In other words, each UE selects the best previous node from its own perspective based on any applicable link selection criteria, such as the exemplary embodiments discussed below. In this way, the decision-making of end-to-end link selection is performed in a distributed manner. For these embodiments, the relay UE can broadcast auxiliary information about the relay-eNodeB link. These embodiments are scalable - that is, the number of broadcast signals/messages is independent of the number of terminal UEs.

In some embodiments, the relay UE forwards the assistance information to subsequent nodes until it reaches the terminal UE, where link selection is performed in a centralized manner. The forwarded information can be information about all links in the previous hop, or only about the eNodeB path to the transmitting relay UE.

In some embodiments of these embodiments utilizing a centralized decision-making process, the terminal UE then makes an end-to-end link selection decision based on available information. In other embodiments, the terminal UE uses a dedicated/control channel to feed this information back to the eNodeB, and the eNodeB subsequently makes a link selection decision. As discussed above, the information forwarded to the terminal UE by the relay UE can be information about all links in the previous hop, or only about the information of the eNodeB path to the transmitting relay UE. When forwarding information about all links, link adaptation/resource allocation can be optimized. The eNodeB can define a network cost (or utility) function and optimize so that path selection decisions are made to multiple UEs at the same time. However, this involves more messages and therefore has a higher overhead. In these embodiments, the number of messages is quadratic with the number of relays, and linear with the number of terminal UEs. When information only about the eNodeB path to the transmitting relay UE is forwarded to the terminal UE, the centralized decision involves lower complexity/overhead.

Thus, the link selection decision may be performed in a distributed, centralized, or semi-centralized (i.e., hybrid) manner. For these embodiments, the decision is based on the link selection criteria used. Some examples of such criteria are given below.

Hop count: Select the link with the lowest hop count between the eNodeB and the terminal UE

Reference Signal Strength (RSS): Select the link with the highest RSS

Potential channel capacity: Based on the available potential BW (bandwidth) (which is based on the load situation), the link with the highest potential channel capacity is selected. As an example,

in,

PathLoss _link =(RStxPower-RSrxPower) _link ........................(D)

Last hop-based path loss: select the link with the minimum path loss from the immediately preceding node

Load conditions, for example, select the least loaded path:

Multi-criteria, i.e. defining cost (or utility) functions of multiple criteria and optimizing them. For example,

in

Cost _link ＝w _1· hopCount _link +w _2. PathLoss _link +w _3· txLoad _link ......(H)

as well as

Due to the asymmetry in the uplink and downlink paths (e.g., due to its limited transmit power, the UE is in coverage in the downlink but out of coverage in the uplink), it is possible that different link selection criteria can be used for downlink and uplink path selection, thereby resulting in asymmetric paths in the uplink and downlink. As an example, the selected downlink path can be a direct path, while the uplink path can be a multi-hop transmission path.

An operation is performed to notify the eNodeB of a request to establish the selected transmission path (as shown in block 610). In embodiments where the terminal UE and/or relay UE selects a multi-hop transmission path, the terminal UE sends a path establishment request to establish a multi-hop link to the eNodeB; the terminal UE may send this information using the selected link. For embodiments where the eNodeB selects a multi-hop or direct transmission path, the eNodeB receives information for selecting the transmission path and subsequently establishes the path for the terminal eNodeB.

FIG7 shows a block diagram of a UE 700 and an eNodeB 750 according to some embodiments. It should be noted that in some embodiments, the eNodeB 750 may be a fixed (non-mobile) device. The UE 700 may include a physical layer circuit (PHY) 702 for transmitting and receiving signals to and from the eNodeB 750, other eNodeBs, other UEs, or other devices using one or more antennas 701, while the eNodeB 750 may include a physical layer circuit (PHY) 752 for transmitting and receiving signals to and from the UE 700, other eNodeBs, other UEs, or other devices using one or more antennas 751. The UE 700 may also include a medium access control layer (MAC) circuit 704 for controlling access to the wireless medium, while the eNodeB 750 may also include a MAC circuit 754 for controlling access to the wireless medium. The UE 700 may further include processing circuitry 706 and memory 708 arranged to perform the operations described herein, and the eNodeB 750 may further include processing circuitry 756 and memory 758 arranged to perform the operations described herein.

Antennas 701, 751 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas, or other types of antennas suitable for transmitting RF signals. In some multiple-input multiple-output (MIMO) implementations, antennas 701, 751 may be effectively separated to benefit from spatial diversity and the resulting different channel characteristics.

Although UE 700 and eNodeB 750 are each shown as having several independent functional elements, one or more functional elements may be combined and may be implemented by a combination of software-configured elements, such as processing elements including digital signal processors (DSPs) and/or other hardware elements. For example, some elements may include one or more of the following: a microprocessor, a DSP, a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a radio frequency integrated circuit (RFIC), and a combination of various hardware and circuits for performing at least the functions described herein. In some embodiments, a functional element may refer to one or more processes operating on one or more processing elements.

The embodiments may be implemented in one or a combination of hardware, firmware, and software. The embodiments may also be implemented as instructions stored on a computer-readable storage device, which can be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory mechanism for storing information in a machine (e.g., computer) readable form. For example, a computer-readable storage device may include: a read-only memory (ROM), a random access memory (RAM), a magnetic disk storage medium, an optical storage medium, a flash memory device, and other storage devices and media. Some embodiments may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

According to an embodiment, the UE 700 may operate according to the D2D communication mode. The UE 700 may include a hardware processing circuit 706 configured to determine a synchronization reference time based on receiving one or more signals from the eNodeB 750. The hardware processing circuit 706 may also be configured to: during the D2D communication session, transmit a multi-time transmission interval bundle group (MTBG) of data symbols during a first set of data transmission intervals (DTIs), and avoid transmitting data symbols during a second set of DTIs dedicated to the first set of DTIs. The start time of the DTI may be based at least in part on the synchronization reference time. The hardware processing circuit 706 may also be configured to: during an intra-network communication session dedicated to the D2D communication session, transmit data symbols according to a time transmission interval (TTI) reference time synchronized with the synchronization reference time. These embodiments are described in more detail below.

In some scenarios, a UE 700 operating in a cellular communication network may begin to experience performance degradation for various reasons. For example, the user load or throughput demand of the network may become high. As another example, the UE 700 may move toward or beyond the edge of a coverage cell. When operating in the network, the UE 700 may actually communicate with other UEs that are physically located very close to the UE 700, although the communication may be conducted through the network. In addition to or in lieu of communication through the network, it may be beneficial for the UE 700 (and other resources of the associated communication system) to conduct direct communication or D2D communication with one or more other UEs that may be within range of the UE 700. As an example, in the above-mentioned performance degradation scenario, D2D communication between the UE 700 and other UEs may enable the network to offload some network traffic, which may improve overall system performance.

Fig. 8 is a block diagram showing a machine component according to some exemplary embodiments, and according to various aspects of the present disclosure, the machine component can read instructions from a machine-readable medium and perform any one or more methods discussed herein. Specifically, Fig. 8 shows an exemplary computer system 800 (which can include any network element discussed above), in which software 824 for causing a machine to perform any one or more methods discussed herein can be executed. In an alternative embodiment, the machine operates as an independent device or can be connected (e.g., networked) to other machines. In a networked deployment, the machine can operate as a server or client machine in a server-client network environment or operate as a peer machine in a point-to-point (or distributed) network environment. The computer system 800 can be used as any one of the above-mentioned UE or eNodeB, and can be: a personal computer (PC), a wearable mobile computing device, a tablet PC, a set-top box (STB), a PDA, a cellular phone, a network appliance, a network router, a switch or a bridge, or any machine that can execute the instruction (in order or other) specifying the action to be taken by the machine. Further, while a single machine is illustrated, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein.

The exemplary computer system 800 may include a processor 802 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), or both), a main memory 804, and a static memory 806, which communicate with each other via a bus 808. The computer system 800 may also include a video display unit 810 (e.g., an LCD or a cathode ray tube (CRT)). The computer system 800 also includes an alphanumeric input device 812 (e.g., a keyboard), a user interface navigation (or cursor control) device 814 (e.g., a mouse), a storage device 816, a signal generating device 818 (e.g., a speaker), and a network interface device 820.

The storage device 816 includes a non-transitory machine-readable medium 822 on which is stored one or more data structures and software 824 embodying or utilized by any one or more of the methodologies or functionality described herein. The software 824, when executed by the computer system 800, may also reside completely or at least partially within the main memory 804 and/or within the processor 802, with the main memory 804 and the processor 802 also constituting the non-transitory machine-readable medium 822. The software 824 may also reside completely or at least partially within the static memory 806.

Although the non-transitory machine-readable medium 822 is shown as a single medium in the exemplary embodiment, the term "machine-readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated cache memory and server) that stores one or more software 824 or data structures. The term "machine-readable medium" may also be understood to include any tangible medium that is capable of storing, encoding, or transmitting instructions for execution by a machine and causing the machine to perform any one or more methods of the present embodiment, or capable of storing, encoding, or transmitting data structures utilized by such instructions or associated with such instruction sets. The term "machine-readable medium" should therefore be understood to include, but is not limited to, solid-state memory, optical media, and magnetic media. Specific examples of machine-readable media 822 include non-volatile memory, including, by way of example, semiconductor memory devices (e.g., erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and flash memory devices); magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and compact disk read-only memory (CD-ROM) and digital versatile disk (or digital video disk) read-only memory (DVD-ROM) disks.

The software 824 may also be sent or received over a communication network 826 using a transmission medium. The software 824 may be transmitted using a network interface device 820 and any of a number of well-known transmission protocols, such as the Hypertext Transfer Protocol (HTTP). Examples of communication networks include a local area network (LAN), a wide area network (WAN), the Internet, a mobile phone network, a plain old telephone service (POTS) network, and wireless data networks such as WiFi networks and WiMax networks. The term "transmission medium" may be understood to include any intangible medium capable of storing, encoding, or transmitting instructions for execution by a machine, including digital or analog communication signals or other intangible media to facilitate communication of such software 824.

The accompanying drawings and the above description provide examples of the present disclosure. Although depicted as multiple different functional items, it will be understood by those skilled in the art that one or more of such elements can be well combined into single-function elements. Alternatively, certain elements can be divided into multifunctional elements. Elements from one embodiment can be added to another embodiment. For example, the order of the processes described herein can be changed and are not limited to the manner described herein. In addition, the actions of any flowchart do not need to be performed in the order shown; all behaviors do not necessarily need to be performed. In addition, behaviors that do not depend on other behaviors can be performed in parallel with the other behaviors. However, the scope of the present disclosure is in no way limited by these specific examples. Whether or not explicitly given in the specification, many variations (such as differences in structure, size, and material use) are possible. The scope of the present disclosure is at least as broad as given in the following claims.

The Abstract is provided to comply with 37 C.F.R. §1.72(b), which requires an abstract that will allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it is not intended to limit or interpret the scope or meaning of the claims. The following claims are hereby incorporated into the Detailed Description, where each claim stands on its own as a separate embodiment.

Some embodiments describe a user equipment (UE) configured to operate as a relay node, comprising: a receiver circuit configured to receive a notification of a request to establish a multi-hop transmission path that communicatively couples an eNodeB and an endpoint UE, and to receive a first message including a first reference signal from a first network node; and a transmit circuit configured to transmit a second message to a second UE, the second message including a second reference signal different from the first reference signal, and measurement information of the transmission path from the first network node to the UE, for use by the second network node to determine whether to select the transmission path from the first network node to the UE as at least part of the multi-hop transmission path.

In some embodiments, the second message includes at least one of a physical downlink control channel (PDCCH) message or a device-to-device (D2D) connection request for D2D communication between the UE and a second UE, and the UE also includes a processing circuit configured to determine measurement information of a transmission path from the first network node to the UE based on the received first reference signal, the measurement information including signal power loss and/or network traffic load of the transmission path from the first network node to the UE.

In some embodiments, the receiver circuit is further configured to receive a third message from a third UE communicatively coupled to the eNodeB, the third message including a third reference signal different from the first and second reference signals, and the processing circuit is further configured to determine second measurement information of a transmission path from the third UE to the UE based on the third reference signal, the second measurement information including signal power loss and/or network traffic load of the transmission path from the third UE to the UE.

In some embodiments, the second network node includes an endpoint UE, and the second message further includes second determined measurement information for use by the endpoint UE to determine whether to select a transmission path from the third UE to the UE as at least part of a multi-hop transmission path. In some embodiments, the processing circuit is further configured to select the determined measurement information instead of the second determined measurement information for inclusion in the second message based at least in part on a comparison of signal power loss and/or network traffic load of the corresponding transmission paths.

In some embodiments, the first network node includes an intermediate relay UE that communicatively couples the eNodeB to the UE, and the first message also includes measurement information of a transmission path from the eNodeB to the intermediate relay UE, and the second message also includes a number of hops in the transmission path from the eNodeB to the UE.

In some embodiments, the first network node includes an eNodeB, and the measurement information of the transmission path from the eNodeB to the UE includes at least one of a signal power loss from the eNodeB to the UE and/or a network traffic load from the eNodeB to the UE. In some embodiments, the second message transmitted to the second UE also includes UE hardware information and/or UE power information.

In some embodiments, the receiver circuit is further configured to receive a transmit offset time value from the eNodeB to mitigate network transmit signal interference, and wherein the transmit circuit is further configured to transmit the second message after the transmit offset time value from the start of the transmit period. In some embodiments, the transmit circuit is further configured to transmit the second message after a randomly selected transmit offset time. In some embodiments, the transmit circuit is further configured to periodically transmit the second message after the randomly selected transmit offset time of each periodic transmission.

In some embodiments, the UE also includes one or more antennas used by the receiver circuitry to receive the first message and used by the transmit circuitry to transmit the second message.

Some embodiments describe processing circuitry comprising: an operating mode circuit for configuring a user equipment (UE) to operate as a relay node, including in response to a notification of a request to establish a multi-hop transmission path that communicatively couples an eNodeB and an endpoint UE; a signal processing circuit for determining measurement information of a transmission path from a first network node to the UE based at least in part on a first reference signal included in a first message received from the first network node; and a message generation circuit for generating a second message for transmission to a second UE, the second message including a second reference signal different from the first reference signal and the determined measurement, for use by the second network node in determining whether to select the transmission path from the first network node to the UE as at least part of the multi-hop transmission path.

In some embodiments, the second message includes at least one of a physical downlink control channel (PDCCH) message or a device-to-device (D2D) connection request for D2D communication between the UE and a second UE, and the determined measurement information includes a signal power loss and/or a network traffic load of a transmission path from the first network node to the UE. In some embodiments, the first network node includes an intermediate relay UE that communicatively couples an eNodeB to the UE, and the first message also includes measurement information of the transmission path from the eNodeB to the intermediate relay UE, and the second message also includes a number of hops in the transmission path from the eNodeB to the UE.

In some embodiments, the first network node comprises an eNodeB, and the determined measurement information of the transmission path from the eNodeB to the UE comprises at least one of signal power loss from the eNodeB to the UE and/or network traffic load from the eNodeB to the UE.

Some embodiments describe a non-transitory computer-readable storage medium storing instructions for execution by one or more processors of a relay user equipment (UE) to configure the relay UE to perform the following operations: receiving a first message from a network node, the network node including an eNodeB or a second relay UE communicatively coupled to the eNodeB, the first message including a first reference signal including a predetermined signal value stored at both the relay UE and the network node; and transmitting a second message to the UE, the second message including: a second reference signal including a predetermined signal value stored at both the relay UE and the UE; and measurement information of a transmission path from the eNodeB to the relay UE, including at least one of a signal power loss of the transmission path from the eNodeB to the relay UE, and/or a network traffic load of the transmission path from the eNodeB to the relay UE.

In some embodiments, the relay UE is further configured to receive a transmit offset time value from the eNodeB, and wherein the second message is transmitted after the transmit offset time value; or periodically transmit the second message after a randomly selected transmit offset time of each periodic transmission.

Some embodiments describe a user equipment (UE), which includes: a transceiver circuit configured to receive a first message from a first relay UE and transmit a path communication request for a selected transmission path to an eNodeB, the first message including a first reference signal and first transmission path information including path information of the first transmission path, the first transmission path including a path from the eNodeB to the first relay UE; and a processing circuit configured to determine direct transmission path information of a direct transmission path from the eNodeB to the UE, and select from a direct transmission path or a multi-hop transmission path based at least in part on a comparison of the direct transmission path information and the first transmission path information, the multi-hop transmission path including a path that communicatively couples the UE to the eNodeB through one or more relay UEs including the first relay UE.

In some embodiments, the transceiver circuit is further configured to receive a second message from a second relay UE, the second message including a second reference signal and second transmission path information including transmission path information of a second transmission path, the second transmission path including a path from the eNodeB to the second relay UE; and the processing circuit is further configured to select the first or second transmission path for the multi-hop transmission path communication request based at least in part on the first and second transmission path information.

In some embodiments, the first and second transmission path information each include a reference signal strength (RSS) of a transmission path from the eNodeB to the corresponding relay UE. In some embodiments, the first and second transmission path information each include at least one of: a number of hops of the transmission path from the eNodeB to the corresponding relay UE, a potential channel capacity of the transmission path from the eNodeB to the corresponding relay UE, a signal power loss of the transmission path from the eNodeB to the corresponding relay UE, and/or a network traffic load of the transmission path from the eNodeB to the corresponding relay UE, wherein the processing circuit is further configured to select a transmission path based on any combination of the first and second transmission path information.

In some embodiments, the first and second transmission path information each include multiple path data, which include two or more of the following: a reference signal strength (RSS) of the transmission path from the eNodeB to the corresponding relay UE, the number of hops of the transmission path from the eNodeB to the corresponding relay UE, the potential channel capacity of the transmission path from the eNodeB to the corresponding relay UE, the signal power loss of the transmission path from the eNodeB to the corresponding relay UE, and the network traffic load of the transmission path from the eNodeB to the corresponding relay UE, and the processing circuit is further configured to select the transmission path based on a weighted combination of the path data included in the first and second transmission path information.

In some embodiments, the first and second transmission path information each include a processing capability of a corresponding relay UE, and wherein the processing circuit is further configured to select the transmission path that utilizes the relay UE having a higher processing capability.

In some embodiments, the first and second transmission path information each include power source information of a corresponding relay UE, and wherein the processing circuit is further configured to select the transmission path utilizing the relay UE having a higher power source.

Claims (25)

1. A user equipment (UE) configured to operate as a relay node, comprising: The receiver circuit is configured as follows: Receive a notification requesting the establishment of a multi-hop transmission path between the communication-coupled base station and the endpoint UE; and Receive a first message including a first reference signal from the first network node; and A transmitting circuit is configured to transmit a second message to a second UE, the second message including a second reference signal different from the first reference signal and measurement information of the transmission path from the first network node to the UE, for the second network node to use to determine whether to select the transmission path from the first network node to the UE as at least part of the multi-hop transmission path, wherein each of the first reference signal and the second reference signal includes a pilot tone using a predetermined transmit power value, the predetermined transmit power value being indicated to the UE via either a dedicated radio resource control message or a broadcast system information block message. 2. The user equipment UE according to claim 1, wherein the second message includes at least one of a physical downlink control channel (PDCCH) message or a device-to-device (D2D) connection request for device-to-device (D2D) communication between the user equipment UE and the second UE, and the user equipment UE further includes: The processing circuit is configured to determine measurement information of the transmission path from the first network node to the user equipment UE based on a received first reference signal, the measurement information including signal power loss and/or network traffic load of the transmission path from the first network node to the user equipment UE. 3. The user equipment (UE) of claim 2, wherein the receiver circuitry is further configured to receive a third message from a third UE communicatively coupled to the base station, the third message including a third reference signal different from the first reference signal and the second reference signal; Furthermore, the processing circuit is configured to determine second measurement information of the transmission path from the third UE to the user equipment UE based on the third reference signal, the second measurement information including signal power loss and/or network traffic load of the transmission path from the third UE to the user equipment UE. 4. The User Equipment (UE) of claim 3, wherein the second network node includes the endpoint UE, and the second message further includes second measurement information for the endpoint UE to use in determining whether to select a transmission path from the third UE to the user equipment UE as at least a part of the multi-hop transmission path. 5. The user equipment (UE) according to claim 3, wherein the processing circuit is further configured to: The measurement information of the transmission path from the first network node to the user equipment (UE) is selected to be included in the second message, based at least in part on a comparison of the signal power loss and/or the network traffic load of the corresponding transmission path, instead of the second measurement information. 6. The User Equipment (UE) of claim 1, wherein the first network node includes an intermediate relay UE communicatively coupling the base station to the UE, and the first message further includes measurement information of the transmission path from the base station to the intermediate relay UE; Furthermore, the second message also includes the hop count of the transmission path from the base station to the user equipment (UE). 7. The User Equipment (UE) of claim 1, wherein the first network node includes the base station, and the measurement information of the transmission path from the base station to the UE includes at least one of signal power loss from the base station to the UE and/or network traffic load from the base station to the UE. 8. The user equipment (UE) according to claim 1, wherein the second message transmitted to the second UE further includes UE hardware information and/or UE power information. 9. The user equipment (UE) of claim 1, wherein the receiver circuit is further configured to receive a transmission offset time value from the base station to mitigate network transmission signal interference, and wherein the transmitting circuit is further configured to transmit the second message after the transmission offset time value from the start of the transmission cycle. 10. The user equipment (UE) of claim 1, wherein the transmitting circuit is further configured to transmit the second message after a randomly selected transmit offset time. 11. The user equipment (UE) of claim 10, wherein the transmitting circuit is further configured to periodically transmit the second message after a randomly selected transmit offset time in each periodic transmission. 12. The user equipment (UE) according to claim 1, further comprising: One or more antennas, which are used by the receiver circuit to receive the first message and by the transmitter circuit to transmit the second message. 13. A processing circuit for use by a user equipment (UE), the processing circuit comprising: An operating mode circuit for configuring the user equipment (UE) to operate as a relay node, including responding to a notification of receiving a request to establish a multi-hop transmission path between a communicatively coupled base station and an endpoint UE; A signal processing circuit, configured to determine measurement information of the transmission path from the first network node to the user equipment (UE) based at least in part on a first reference signal included in a first message received from the first network node; and A message generation circuit is configured to generate a second message to a second UE, the second message including a second reference signal and determined measurement information for use by a second network node to determine whether to select a transmission path from the first network node to the user equipment UE as at least a part of the multi-hop transmission path, wherein each of the first reference signal and the second reference signal includes a pilot tone using a predetermined transmit power value, the predetermined transmit power value being indicated to the UE via either a dedicated radio resource control message or a broadcast system information block message. 14. The processing circuitry of claim 13, wherein the second message includes at least one of a Physical Downlink Control Channel (PDCCH) message or a device-to-device (D2D) connection request for device-to-device (D2D) communication between the user equipment (UE) and the second UE, and the determined measurement information includes signal power loss and/or network traffic load of the transmission path from the first network node to the user equipment (UE). 15. The processing circuit of claim 13, wherein the first network node includes an intermediate relay UE communicatively coupling the base station to the user equipment UE, and the first message further includes measurement information of the transmission path from the base station to the intermediate relay UE; Furthermore, the second message also includes the hop count of the transmission path from the base station to the user equipment (UE). 16. The processing circuit of claim 13, wherein the first network node includes the base station, and the determined measurement information of the transmission path from the base station to the user equipment UE includes at least one of signal power loss from the base station to the user equipment UE and/or network traffic load from the base station to the user equipment UE. 17. An apparatus for use by a relay user equipment (UE), the apparatus comprising: A means for receiving a first message from a network node, the network node including a base station or a second relay UE communicatively coupled to the base station, the first message including a first reference signal, the first reference signal including predetermined signal values stored at both the relay UE and the network node; and A means for transmitting a second message to a third UE, the second message including: The second reference signal includes predetermined signal values stored at both the relay user equipment (UE) and the third UE; and Measurement information of the transmission path from the base station to the relay user equipment (UE), including at least one of the signal power loss of the transmission path from the base station to the relay UE and/or the network traffic load of the transmission path from the base station to the relay UE. The measurement information of the transmission path from the base station to the relay user equipment (UE) is used by a second network node to determine whether to select the transmission path from the base station to the relay UE as at least part of a multi-hop transmission path that communicatively couples the base station and the endpoint UE, wherein each of the first reference signal and the second reference signal includes a pilot tone using a predetermined transmit power value, which is indicated to the endpoint UE via either a dedicated radio resource control message or a broadcast system information block message. 18. The equipment according to claim 17, further comprising at least one of the following: A means for receiving a transmission offset time value from the base station, wherein the second message is transmitted after the transmission offset time value; or A means for periodically transmitting the second message after a randomly selected transmission offset time in each periodic transmission. 19. A user equipment (UE) for selecting from a plurality of transmission paths to a base station, the UE comprising: The transceiver circuit is configured as follows: A first message is received from a first relay UE, the first message including a first reference signal and first transmission path information including path information of a first transmission path, the first transmission path including a path from the base station to the first relay UE; and Transmitting a path communication request for the selected transmission path to the base station; and processing circuitry configured to: Determine the direct transmission path information of the direct transmission path from the base station to the user equipment (UE); and The selection is made, at least in part, from the direct transmission path or the multi-hop transmission path based on a comparison of the direct transmission path information with the first transmission path information. The multi-hop transmission path includes a path that communicatively couples the user equipment UE to the base station via one or more relay UEs including the first relay UE. The first reference signal includes a pilot tone using a predetermined transmit power value, which is indicated to the endpoint UE via either a dedicated radio resource control message or a broadcast system information block message. 20. The user equipment (UE) of claim 19, wherein the transceiver circuitry is further configured to: Receive a second message from the second relay UE, the second message including: Second reference signal; and The second transmission path information includes transmission path information of a second transmission path, wherein the second transmission path includes a path from the base station to the second relay UE; Furthermore, the processing circuitry is configured to select either the first transmission path or the second transmission path for the multi-hop transmission path communication request, at least in part, based on the first transmission path information and the second transmission path information. 21. The user equipment (UE) of claim 20, wherein the first and second transmission path information each includes a reference signal strength (RSS) of the transmission path from the base station to the corresponding relay UE. 22. The user equipment (UE) of claim 20, wherein the first and second transmission path information each comprise at least one of the following: The number of hops in the transmission path from the base station to the corresponding relay UE; Potential channel capacity of the transmission path from the base station to the corresponding relay UE; Signal power loss along the transmission path from the base station to the corresponding relay UE; and/or Network traffic load from the base station to the corresponding relay UE; The processing circuitry is also configured to select a transmission path based on any combination of the first and second transmission path information. 23. The user equipment (UE) of claim 22, wherein the first and second transmission path information each comprises a plurality of path data, the plurality of path data comprising two or more of the following: Reference signal strength (RSS) of the transmission path from the base station to the corresponding relay UE; The number of hops in the transmission path from the base station to the corresponding relay UE; Potential channel capacity of the transmission path from the base station to the corresponding relay UE; The signal power loss along the transmission path from the base station to the corresponding relay UE; and The network traffic load of the transmission path from the base station to the corresponding relay UE; Furthermore, the processing circuit is configured to select a transmission path based on a weighted combination of the path data included in the first and second transmission path information. 24. The user equipment (UE) of claim 20, wherein the first and second transmission path information each includes the processing capability of the respective relay UE, and wherein the processing circuitry is further configured to select a transmission path utilizing the relay UE with higher processing capability. 25. The user equipment (UE) of claim 20, wherein the first and second transmission path information each includes power information of the respective relay UE, and wherein the processing circuitry is further configured to select a transmission path utilizing the relay UE with higher power.