CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Indian Provisional Patent Application Serial No. 201641025050 filed on Jul. 21, 2016, in the Indian Intellectual Property Office, and to Indian Complete Patent Application Serial No. 201641025050 filed on Jul. 3, 2017 in the Indian Intellectual Property Office, the entire disclosure of each of which is incorporated herein by reference.

1. TECHNICAL FIELD

The present invention generally relates to wireless communication and more particularly, to a system and method for discovering user equipment (UE) over side link relay in device to device (D2D) communication.

2. DISCUSSION OF THE RELATED ART

Long term evolution (LTE) side-link (Device to device communication, D2D), also called as ProSe (Proximity Service) Relay, is being studied and developed in 3GPP standard workgroups at present. It is aimed at equipping LTE to cater to critical communication services like public safety services like MC-PTT (Mission Critical Push to Talk) or GSCE (Group communication System Enablers) services as well as infotainment broadcast services like MBMS (Multimedia Broadcast Multicast services) providing audio/video streaming or text/data based services. It is directed to extend the coverage area e.g. serving UEs (User Equipment) that are located outside of network coverage, also called Remote UEs (These UEs may still be in coverage of networks other than ProSe networks being discussed). In general, these remote UEs are connected to the ProSe networks through another UE called Relay UE which is in coverage of ProSe network. Thereby, Relay UE provides an indirect link to the Remote UEs to the network. Relay UE may be connected to the network by at least one of the multitude of the air interface techniques like cellular LTE, Multicast-broadcast single-frequency network (MBSFN), wireless local area network (WLAN), etc. whereas, it communicates with the Remote UEs with side-link communication (i.e. D2D link).

Establishment and maintenance of side-link communication involves many procedures.FIG. 1is a schematic flow diagram illustrating Type-1 Discovery mechanism for ProSe Relay, according to an existing art. According to theFIG. 1, first of all Remote UE needs to discover the Relay UE which can provide its service of interest. For this purpose, a remote UE can monitor the periodical announcements being made by the Relay UE and accordingly get associated with the Relay UE based on the sufficient signal conditions of the link.

FIG. 2is a schematic flow diagram illustrating Type-2 Discovery Mechanism, according to an existing art. According to theFIG. 2, a Remote UE sends a solicitation messages and based on response of the Relay UE gets associated with it after determining signal conditions are adequate.

Once getting associated a Layer-2 Link is established between the Remote and Relay UE for one-to-one ProSe Direct Communication, wherein data transmissions and reception between Remote UE and Relay UE takes place. Also, at the same time Remote UE keeps monitoring the signal conditions of the link to ensure connectivity. In case of deterioration of the link, it may start searching for a different Relay; this process is called Relay reselection.

FIG. 3is a schematic flow diagram illustrating disconnect procedure, according to an existing art. According to theFIG. 3, after the necessary communications over the sidelink channel are completed the Remote UE or Relay UE can release the Layer-2 Link by sending the Disconnect Request Sidelink message.

Many potential issues are noticed with the existing system and procedures for LTE Side-link Relay communication. One of the problems being addressed in this invention is how to optimize the energy efficiency by reducing the power consumption at the prose Network-to-UE Relay (also called Relay) and Remote UEs. The power consumption depends on multiple factors—number of remote UEs being served, DRX cycle of the relay and remote UE and the delay tolerance of the services. The Relay UE's power consumption would increase as the number of remote UEs being served increases, the DRX cycle of the remote UEs hugely differs from each other and from the relay UE and if the delay tolerance of the service is very less, which in turn reduces the energy efficiency of the relay UE. Other aspects and issues involved for LTE side-link Relay communication is about how to aggregate service data pertaining to one or more Remote UEs and how to schedule transmissions with meeting the needed Quality of Service (QoS) for each of the service for each of the Remote UEs involved in Relay communication.

Further, discovery procedure for Relay Networks have been objective in defining procedures for finding Relay UE, but Remote UE discovery/identification is not properly addressed.

Currently, no procedure is present in 3GPP specs to handle congestion on Relay UE, which may get overloaded when catering multiple Remote UEs. Further, service Continuity aspects for remote UEs are not yet addressed in 3GPP specs.

Further, currently, the LTE side-link Relay communication is the 3GPP standard. It does not address the aspects and issues explained aforementioned and resultantly leads to sub-optimum performance of the Relay system including both Relay UE and Remote UEs.

Thus there is a need for a system and method for device to device (D2D) communication with the side-link relay to overcome the higher power consumption and optimize energy efficiency. Further, there is a need for a system and method for enhancing Remote UE identification and discovery procedures while specifying messages and their contents required for such an enhancement. Further, there is a need for a system and method with Congestion Handling Scheme for Relay systems.

Further, there is a need for a system and methods that uses specific procedures catering to the herein above mentioned issues using retry, redirection, load balancing, and the like. Further, there is need for solutions aiming at maintaining a seamless Relay services.

The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

SUMMARY

The various embodiments of the present invention disclose a system and method for discovering user equipment (UE) over side link relay in device to device (D2D) communication. According to an embodiment of the present invention, a method for discovering User Equipment (UE) over side link in device to device (D2D) communication, the method comprises steps of receiving, by a relay User Equipment (UE), a solicitation message from a remote User Equipment (UE), wherein the solicitation message comprises of one or more combination of information including an UE identity, QoS Requirements, DRX configuration signals, current transmission power (Tx Pwr), and transmitting, by the relay UE, a device discovery response along with a support status message to the remote UE based on the UE Id in the solicitation message.

In an embodiment of the present invention, the relay UE transmits the device discovery response based on at least one of, but not limited to, QoS/latency bounds supportable, checking if Energy consumption is within threshold for Relay UE if admitting the soliciting remote UE with its Tx_Pwr, number of currently serving remote UEs is under limit, remote UE device type, bandwidth, and the like, without departing from the scope of the invention.

According to an embodiment of the present invention, a method for discovering User Equipment (UE) over side link in device to device (D2D) communication, the method comprises steps of receiving, by a relay User Equipment (UE), a solicitation message from a remote User Equipment (UE), wherein the solicitation message comprises of an UE identity, QoS Requirement i.e. packet delay budget/latency bound, DRX configuration signals, current transmission power (Tx Pwr), determining, by the relay UE, a relay load status as overloaded or congested if the Remote UE is in coverage area and a Type 2 discovery method is used, and responding in Solicitation response message with an overload indication, if the relay load status is overloaded.

In an embodiment of the present invention, in a Type 2 Discovery, the Relay UE responds in Solicitation response message with an overload indication and/or back-off indication or back-off duration value. In an embodiment of the present invention, if the QoS requested by the remote UE is not supported by the Relay UE, the Relay UE indicates the support status as negative.

According to another embodiment of the present invention, a method for discovering User Equipment (UE) over side link in device to device (D2D) communication, the method comprises steps of checking, by a relay UE, the QoS (latency bounds) information in a solicitation message received from one or more remote UEs, scheduling one or more service and remote UE transmissions in priority order based on a latency requirements of the one or more remote UEs, preparing RX scheduling patterns based on the latency requirements, and assigning the RX scheduling patterns to the one or more remote UEs with aligning DRXs between relay and one or more remote UE(s).

According to another embodiment of the present invention, a method for enabling side link relay discovery in device to device (D2D) communication, the method comprises steps of receiving, by one or more relay User Equipment's (UE), a solicitation message transmitted by a remote User Equipment (UE), and transmitting, by the one or more relay UEs which are currently overloaded, a solicitation response message in Type 2 discovery, wherein the solicitation response message comprises of overload status indicating whether the relay UE is overloaded.

In an embodiment of the present invention, the method further comprises of receiving, by one or more remote User Equipment's (UE), an announcement message transmitted by a relay User Equipment (UE) in type 1 discovery, wherein the announcement message comprises of overload status indicating whether the relay UE is overloaded, ignoring, by one or more remote UEs, congestion status if the remote UE is already connected, obtaining, by the one or more remote UEs, PC5 measurements to check if relay reselection criteria meets, abandoning, by one or more remote UEs, selection or reselection of the relay UE if they are interested to connect or trying to connect, and abandoning, by one or more Remote UEs, PC5 measurements for the Relay UE to check for relay reselection criteria.

In another embodiment of the present invention, the method further comprises steps of transmitting, by the one or more Relay UEs, an overload indicator during a Master Information Block (MIB) broadcast indicating whether the UE relay is overloaded or not, and avoiding by the one or more out of coverage remote UEs, sending of the Solicitation Request message to the one or more relay UEs which are overloaded.

In another embodiment of the present invention, the method further comprises of backing off, by the one or more remote UEs, from sending the solicitation request message on receiving the overload indicator from the relay UEs, wherein the back-off duration is pre-provisioned to be selected from a predefined range.

According to an embodiment of the present invention, a method for enabling side link relay discovery in device to device (D2D) communication, the method comprises steps of receiving, by a relay User Equipment (UE), a DRX configuration request from a remote User Equipment (UE) over a PC-5 link, determining, by the relay UE, an optimal DRX configuration for the remote UE, and sending, by the relay UE, the DRX configuration to the remote UE over the PC5 link and ensures no data is transmitted to the remote UE during the DRX period.

In an embodiment of the present invention, the DRX configuration request comprises of, but not limited to, a state indicator, and DRX parameters, without departing from the scope of the invention. In another embodiment of the present invention, the remote UE applies both Unicast and side-link DRX configuration to determine an active DRX period.

In another embodiment of the present invention, the Relay UE determines optimal DRX configuration based on at least one of, but not limited to, alignment for DRX configuration used by the Remote UE and the Relay UE, services and their corresponding scheduling information, providing same DRX config as its own or a sub-set of it based on service needs, QoS/latency bounds of the service, the received configurations from the eNB, selected configuration from a pool of configurations, and the like, without departing from the scope of the invention.

According to another embodiment of the present invention, a method for enabling side link relay discovery in device to device (D2D) communication, the method comprises steps of receiving, by a relay User Equipment (UE), a data set from a network, performing, by the relay UE, data aggregation of transmission data, performing, by the relay UE, a data transmission to a remote UE according to the configured DRX, and receiving, by the relay UE, data transmitted by the remote UE according to the configured DRX.

In an embodiment of the present invention, the Relay UE utilizes the QoS (latency bounds) information received from the Remote UE in deciding how much aggregation and transmission delay can be incurred at Relay UE side and scheduling transmissions for the remote UEs.

According to another embodiment of the present invention, method of disconnecting

Comprises steps of sending, by a relay UE, a disconnection request to a remote UE along with a redirection information for switching of remote UE to another Relay User Equipment (UE), and receiving, by the relay UE, a disconnect response from the remote UE.

In an embodiment of the present invention, the relay UE acquires the redirection information that includes redirection information based on SIB19 which out of coverage Remote UEs can utilize.

According to another embodiment of the present invention, a Relay User Equipment (UE) for side-link communication comprising a Remote-Relay Controller (RR controller) adapted for providing RX patterns assignment to remote UE(s) with aligning DRXs between relay and remote UE(s), Traffic identification and differentiation, Service Data aggregation for remote UE(s), and QoS based scheduling transmission. Further, the relay UE comprises of a router module adapted to connect a cellular link to a side-link with a L3 forwarding based approach, a side-link stack adapted for enabling communication with one or more remote User Equipment's (UEs) connected to the relay UE, and an interface technique for connecting the relay UE to the cellular network, where the network interface comprises at least one of, but not limited to, a cellular Long-Term Evolution (LTE) network, Multicast-broadcast single-frequency network (MBSFN), wireless local area network (WLAN), and the like, without departing from the scope of the invention.

The foregoing has outlined, in general, the various aspects of the invention and is to serve as an aid to better understanding the more complete detailed description which is to follow. In reference to such, there is to be a clear understanding that the present invention is not limited to the method or application of use described and illustrated herein. It is intended that any other advantages and objects of the present invention that become apparent or obvious from the detailed description or illustrations contained herein are within the scope of the present invention.

