Abstract:
A communication device for handling a device-to-device (D2D) communication comprises a storage unit for storing instructions and a processing means coupled to the storage unit. The storage unit is configured to execute the instructions stored in the storage unit. The instructions comprise receiving a barring in a signalling transmitted by a first base station; and bypassing the barring to initiate a procedure for the D2D communication to a second base station.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/012,993, filed on Jun. 17, 2014 and incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is related to a communication device and a method used in a wireless communication system, and more particularly, to a communication device and a method of handling a device-to-device communication in a wireless communication system. 
         [0004]    2. Description of the Prior Art 
         [0005]    A long-term evolution (LTE) system supporting the 3rd Generation Partnership Project (3GPP) Rel-8 standard and/or the 3GPP Rel-9 standard are developed by the 3GPP as a successor of a universal mobile telecommunications system (UMTS), for further enhancing performance of the UMTS to satisfy increasing needs of users. The LTE system includes a new radio interface and a new radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNBs) for communicating with multiple user equipments (UEs), and for communicating with a core network including a mobility management entity (MME), a serving gateway, etc., for Non-Access Stratum (NAS) control. 
         [0006]    A LTE-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system. The LTE-A system targets faster switching between power states, improves performance at the coverage edge of an eNB, and includes advanced techniques, such as carrier aggregation (CA), coordinated multipoint (CoMP) transmission/reception, uplink multiple-input multiple-output (UL-MIMO), etc. For a UE and an eNB to communicate with each other in the LTE-A system, the UE and the eNB must support standards developed for the LTE-A system, such as the 3GPP Rel-10 standard or later versions. 
         [0007]    Device-to-device (D2D) communication may be realized, after an initialization (e.g., connection establishment and/or peer discovery) is performed (e.g., assisted by an eNB). Then, two UEs may communicate (e.g., transmitting and/or receiving packets) with each other directly according to the D2D communication, and the eNB does not need to forward the packets transmitted between the communication devices. According to the D2D communication, the UEs may communicate with each other via UL resources (e.g., UL subframes configured by the eNB). In general, the D2D communication may also be seen as a D2D service (i.e., proximity service (ProSe)). In addition, a D2D subframe, D2D transmission, D2D communication and D2D discovery can be termed as a sidelink subframe, sidelink transmission, sidelink communication and sidelink discovery, respectively. 
         [0008]    However, there are some issues regarding the D2D communication in the prior art. In one example, the UEs (e.g., a first UE and a second UE) are out of coverage areas of eNBs, when the UEs communicate with each other according to the D2D communication, e.g., via a mode 2 resource allocation. When the first UE moves to a coverage area of an eNB, the first UE may initiate a tracking area update procedure to an evolved packet core (EPC) connected to the eNB. However, the first UE may not be able to initiate the tracking area update procedure, e.g., because an access barring for a mobile originated signaling is configured to the first UE, or a back-off timer is still running. The first UE cannot successfully register itself to a network (e.g., Mobility Management Entity (MME)) via the eNB, and consequently the first UE cannot be allocated with a mode 1 resource allocation. Hence, quality of the D2D communication cannot be improved. The abovementioned problem may also to the second UE, when the second UE enters a coverage area of an eNB. 
         [0009]    Thus, how to solve improve quality of the D2D communication when one or more communication operations of the UE are barred is an important problem to be solved. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention therefore provides a communication device and a method for handling a device-to-device communication to solve the abovementioned problem. 
         [0011]    A communication device for handling a device-to-device (D2D) communication comprises a storage unit for storing instructions and a processing means coupled to the storage unit. The storage unit is configured to execute the instructions stored in the storage unit. The instructions comprise receiving a barring in a signalling transmitted by a first base station; and bypassing the barring to initiate a procedure for the D2D communication to a second base station. 
         [0012]    A method for handling a device-to-device (D2D) communication for a communication device comprises receiving a barring in a signalling transmitted by a first base station; and bypassing the barring to initiate a procedure for the D2D communication to a second base station. 
         [0013]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic diagram of a wireless communication system according to an example of the present invention. 
           [0015]      FIG. 2  is a schematic diagram of a communication device according to an example of the present invention. 
           [0016]      FIG. 3  is a flowchart of a process according to an example of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  is a schematic diagram of a wireless communication system  10  according to an example of the present invention. The wireless communication system  10  is briefly composed of a network  100  and user equipments (UEs)  102  and  104 . In  FIG. 1 , the network  100  and the UEs  102  and  104  are simply utilized for illustrating the structure of the wireless communication system  10 . A UE may communicate with the network  100  according to a device-to-cellular (D2C) communication defined in a communication standard, e.g., the 3rd Generation Partnership Project (3GPP) standard. Practically, the network  100  can be a universal terrestrial radio access network (UTRAN) comprising at least one Node-B (NB) in a universal mobile telecommunications system (UMTS). In another example, the network  100  can be an evolved UTRAN (E-UTRAN) comprising at least one evolved NB (eNB) and/or at least one relay in along term evolution (LTE) system, a LTE-Advanced (LTE-A) system or an evolution of the LTE-A system. As an example, the network  100  includes an eNB  1002  connected to an evolved packet core (EPC)  1004  in  FIG. 1 . 
         [0018]    Furthermore, the network  100  can also include both the UTRAN/E-UTRAN and a core network, wherein the core network includes network entities such as Mobility Management Entity (MME), Serving Gateway (S-GW), Packet Data Network (PDN) Gateway (P-GW), Self-Organizing Networks (SON) server and/or Radio Network Controller (RNC), etc. In other words, after the network  100  receives information transmitted by a UE (e.g., the UE  102  and/or the UE  104 ), the information may be processed only by the UTRAN/E-UTRAN and decisions corresponding to the information are made at the UTRAN/E-UTRAN. Alternatively, the UTRAN/E-UTRAN may forward the information to the core network, and the decisions corresponding to the information are made at the core network after the core network processes the information. In addition, the information can be processed by both the UTRAN/E-UTRAN and the core network, and the decisions are made after coordination and/or cooperation are performed by the UTRAN/E-UTRAN and the core network. 
         [0019]    A UE (e.g., the UE  102  and/or the UE  104 ) can be a low cost device (e.g., machine type communication (MTC) device), a device-to-device (D2D) device, a mobile phone, a laptop, a tablet computer, an electronic book, a portable computer system, or combination thereof. In addition, for the D2C communication, the network  100  and the UE can be seen as a transmitter or a receiver according to direction (i.e., transmission direction), e.g., for an uplink (UL), the UE is the transmitter and the network  100  is the receiver, and for a downlink (DL), the network  100  is the transmitter and the UE is the receiver. 
         [0020]    In addition, the UEs  102  and  104  may communicate with each other directly, after an initialization (e.g., connection establishment and/or peer discovery) is performed. For example, the initialization may be assisted by the network  100 . That is, the UEs  102  and  104  may communicate (e.g., transmit and/or receive signals/packets) with each other according to a D2D communication defined in a communication standard, e.g., 3GPP standard. The UEs  102  and  104  may communicate with each other via UL resources (e.g., UL subframes or UL carriers) determined according to frequency-division duplexing (FDD) configuration and/or time-division duplexing (TDD) configurations. In one example, the UE  102  may communicate with the UE  104  and the network  100  simultaneously, i.e., both the D2D communication and the D2C communication are realized at the same time. 
         [0021]      FIG. 2  is a schematic diagram of a communication device  20  according to an example of the present invention. The communication device  20  may be used for realizing the network  100 , the UE  102  and/or the UE  104  shown in  FIG. 1 , but is not limited herein. The communication device  20  may include a processing means  200  such as a microprocessor or Application Specific Integrated Circuit (ASIC), a storage unit  210  and a communication interfacing unit  220 . The storage unit  210  may be any data storage device that may store a program code  214 , accessed and executed by the processing means  200 . Examples of the storage unit  210  include but are not limited to a subscriber identity module (SIM), read-only memory (ROM), flash memory, random-access memory (RAM), Compact Disc Read-Only Memory (CD-ROM), digital versatile disc-ROM (DVD-ROM), Blu-ray Disc-ROM (BD-ROM), magnetic tape, hard disk, optical data storage device, non-volatile storage unit, non-transitory computer-readable medium (e.g., tangible media), etc. The communication interfacing unit  220  is preferably a transceiver and is used to transmit and receive signals (e.g., data, signals, messages and/or packets) according to processing results of the processing means  200 . 
         [0022]      FIG. 3  is a flowchart of a process  30  according to an example of the present invention. The process  30  may be utilized in the UE  102  (or the UE  102 ) shown in  FIG. 1 , to handle a D2D communication. The process  30  may be compiled into the program code  214  and includes the following steps: 
         [0023]    Step  300 : Start. 
         [0024]    Step  302 : Receive a barring in a signalling transmitted by a first eNB. 
         [0025]    Step  304 : Bypass the barring to initiate a procedure for the D2D communication to a second eNB. 
         [0026]    Step  306 : End. 
         [0027]    According to the process  30 , the UE  102  may receive a barring in a signalling transmitted by a first eNB. The UE  100  may initiate to communicate with another UE (e.g., the UE  104 ) according to the D2D communication. Then, the UE  102  may bypass the barring to initiate a procedure for the D2D communication to a second eNB (e.g., the eNB  1002 ). That is, the UE  102  may be barred from performing one or more communication operations, e.g., transmissions and/or transmissions. According to the prior art, the UE  102  is not allowed to perform the procedure which in general includes one or more communication operations to the second eNB. In contrast, according to the process  30 , the UE  102  initiates the procedure regardless of the barring. That is, a priority of the procedure for the D2D communication is higher than a priority of the barring. Thus, throughout of the UE  102  can be improved after the initiating the procedure to the eNB  1002 . 
         [0028]    In one example, the UE  102  may be communicating with the UE  104  via a mode 2 resource allocation according to the D2D communication. Quality of communication via the mode 2 resource allocation is in general worse than quality of communication via a mode 1 resource allocation. However, the mode 1 resource allocation cannot be used by the UE  102  arbitrarily, but should be scheduled by the eNB  1002  to the UE  102  after a specific procedure is performed. According to the process  30 , the UE  102  may initiate the procedure for obtaining the mode 1 resource allocation (e.g., from the eNB  1002 ) for the D2D communication. In another example, the UE  102  may initiate the procedure for activating the D2D communication with the UE  104 . 
         [0029]    The signaling in the process  30  is not limited to any specific signaling. For example, the signalling may be a Non-Access Stratum (NAS) signalling or a radio resource control (RRC) signalling. That is, the UE  102  may be barred for one or more communications by the barring in the NAS signalling or the RRC signalling. In addition, the barring may be an access barring configured by ac-BarringForMO-Data, ac-BarringForMO-Signalling, waitTime or extendedWaitTime in the RRC signalling. In another example, the barring may be an access barring configured by a back-off timer in the NAS signalling. 
         [0030]    The procedure in the process  30  is not limited to any specific procedure. For example, the procedure may include an RRC procedure. Further, the RRC procedure may include an RRC establishment procedure. In one example, the procedure may include a NAS procedure. Further, the NAS procedure may include a service request procedure, an attach procedure, a tracking area update procedure or a new procedure dedicated for requesting the D2D communication. In other words, the UE  102  may perform any of the abovementioned procedures regardless of the barring, to obtain the mode 1 resource allocation for the D2D communication. 
         [0031]    In the process  30 , the UE  102  is in a coverage area of the first eNB. The UE  102  may leave the coverage area, e.g., after a certain time interval. Then, the UE  102  may go to a coverage area of the second eNB (e.g., the eNB  1002 ), and tries to initiate the procedure. That is, the UE  102  leaves the coverage area of the first eNB, and enters the coverage area of the second eNB (e.g., after a while). In short, the barring may be bypassed to initiate the procedure under a condition that the UE  102  enters a coverage area of the second BS. The UE may receive the barring from the second eNB. The first eNB and the second eNB in may be the same eNB or different eNBs. That is, the UE  102  may go back to the coverage area of the same eNB, or go to the coverage area of a different eNB. In the latter case, the UE  102  may perform a tracking area update procedure via the second eNB for the D2D communication with the UE  104 . 
         [0032]    In one example, the UE  102  may stop initiating another procedure for a non-D2D communication according to the barring. That is, the UE  102  violates the barring when the procedure is initiated for the D2D communication, and follows the barring when the procedure is not initiated for the D2D communication. The non-D2D communication may include communication such as voice call, short message service, or internet data call via which data traverse the network. In one example, the UE  102  may continue to communicate with the UE  104  according to the D2D communication under a condition that the procedure is initiated for the D2D communication. That is, the communication (i.e., D2D communication) between the UE  102  and the UE  104  is not stopped, when initiating the procedure. In another example, the UE  102  may stop communicating with the UE  104  according to the D2D communication under a condition that the procedure is initiated for the D2D communication. That is, the communication (i.e., D2D communication) between the UE  102  and the UE  104  is suspended, when initiating the procedure. After the procedure is completed, the communication between the UE  102  and the UE  104  may be resumed. 
         [0033]    Those skilled in the art should readily make combinations, modifications and/or alterations on the abovementioned description and examples. The abovementioned description, steps and/or processes including suggested steps can be realized by means that could be hardware, software, firmware (known as a combination of a hardware device and computer instructions and data that reside as read-only software on the hardware device), an electronic system, or combination thereof. An example of the means may be the communication device  20 . 
         [0034]    Examples of the hardware may include analog circuit(s), digital circuit (s) and/or mixed circuit (s). For example, the hardware may include ASIC(s), field programmable gate array(s) (FPGA(s)), programmable logic device(s), coupled hardware components or combination thereof. In another example, the hardware may include general-purpose processor(s), microprocessor(s), controller(s), digital signal processor(s) (DSP(s)) or combination thereof. 
         [0035]    Examples of the software may include set(s) of codes, set(s) of instructions and/or set(s) of functions retained (e.g., stored) in a storage unit, e.g., a computer-readable medium. The computer-readable medium may include SIM, ROM, flash memory, RAM, CD-ROM/DVD-ROM/BD-ROM, magnetic tape, hard disk, optical data storage device, non-volatile storage unit, or combination thereof. The computer-readable medium (e.g., storage unit) may be coupled to at least one processor internally (e.g., integrated) or externally (e.g., separated). The at least one processor which may include one or more modules may (e.g., be configured to) execute the software in the computer-readable medium. The set(s) of codes, the set(s) of instructions and/or the set(s) of functions may cause the at least one processor, the module(s), the hardware and/or the electronic system to perform the related steps. 
         [0036]    Examples of the electronic system may include a system on chip (SoC), system in package (SiP), a computer on module (CoM), a computer program product, an apparatus, a mobile phone, a laptop, a tablet computer, an electronic book or a portable computer system, and the communication device  20 . 
         [0037]    To sum up, the present invention provides a communication device and a method for improving quality of communications between UEs which are out of coverage areas of eNBs, when one of the UEs enters a coverage area of an eNB. According to the present invention, the UE can bypass a barring configured to the UE, to initiating a procedure for the D2D communication. Thus, a mode 1 resource allocation may be configured to the UE from the eNB, after the procedure is performed. 
         [0038]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.