Patent Publication Number: US-2015080040-A1

Title: Terminal device discovery method, device and system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Patent Application No. PCT/CN2013/070282, filed on Jan. 9, 2013, which claims priority to Chinese Patent Application No. 201210164361.0, filed on May 24, 2012, both of which are hereby incorporated by reference in their entireties. 
    
    
     FIELD 
     The present invention relates to the technical field of communication, in particular to a terminal device discovery method, device and system. 
     BACKGROUND 
     At present, it is a waste of radio resource to transmit information between two adjacent terminal devices in a network via an evolved NodeB (Evolved NodeB, eNodeB). For example, it may save a half of radio resource to transmit data directly between two adjacent devices than to transmit the data via a base station. The method for communicating directly between two adjacent devices is referred to as D2D (Device to Device, D2D). In D2D communication, two terminal devices adopt spectrum resources of radio communication network. With the development of smart phone, it is more common to transmit data between two adjacent user devices, such as sharing data or playing game by networking between two adjacent user devices. Therefore, it is getting more important for the public to communicate directly between two user devices. 
     The conventional method for establishing D2D network includes: in a case that a first terminal device and a second terminal device are to be connected in a D2D manner, the first terminal device may send a request to a network where the first terminal device resides. Multiple base stations of the network detect the second terminal device, and each base station sends a paging message to the second terminal device, where the paging message includes preamble distributed to the second terminal device by the base station, and the base station notifies the first terminal device of information of the preamble. The second terminal device sends the preamble via a random access channel of a cell network, after the first terminal device detects for the preamble sent by the second terminal device in the random access channel of the cell network. In a case that the preamble is detected, it may be determined whether the first terminal device and the second terminal device can be connected in a D2D manner. The first terminal device presets a threshold of signal intensity, and it may be determined that the first terminal device and the second terminal device can be connected in a D2D manner in a case that a signal intensity of the preamble is greater than the threshold of signal intensity, then the base station may send a command for D2D mode to the first terminal device and the second terminal device, in a way that a D2D network is established. 
     Each base station may send a paging message with preamble within its own area when detecting for the second terminal, thus the preamble may be wasted, and the wasted preamble may not be applied by other pagings within a certain period of time, thereby influencing the performance of the random access channels of other terminal devices of the base station. 
     SUMMARY 
     It is to provide a terminal device discovery method, device and system, which may save the resource of preamble when the base station searching for terminal device. 
     In view of this, the technical solution is described as follows. 
     A terminal device discovery method, including: 
     acquiring, by a first terminal device, information of synchronizing signals of one or more cells within a base station, where the base station is a base station where the first terminal device or a second terminal device resides; and 
     detecting, by the first terminal device, for a synchronizing signal sent by the second terminal device, based on the information of the synchronizing signals of the one or more cells and obtain an intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal, where the synchronizing signal sent by the second terminal device is one of the synchronizing signals of the one or more cells. 
     A terminal device discovery method, including: 
     acquiring, by a second terminal device, parameter information of sending a synchronizing signal, where the synchronizing signal is one of synchronizing signals of one or more cells within a base station, and the base station is a base station where a first terminal device or the second terminal device resides, where the parameter information includes information of sending a synchronizing signal; and 
     sending, by the second terminal device, the synchronizing signal based on the parameter information, where the synchronizing signal is detected by the first terminal device, and the an intensity of the synchronizing signal is obtained by the first terminal device. 
     A terminal device discovery method, including: 
     sending a message to a second terminal device, where the message is for instructing the second terminal device to send a synchronizing signal, where the synchronizing signal is one of synchronizing signals of one or more cells within a base station, and the base station is a base station where a first terminal device or the second terminal device resides; 
     sending the information of the synchronizing signals of the one or more cells within the base station to the first terminal device; and 
     receiving instruction information sent by the first terminal device, where the instruction information includes a determining result made by the first terminal device which indicates whether a D2D network connection can be established between the first terminal and the second terminal device based on the intensity of the synchronizing signal, or includes the intensity of the synchronizing signal received by the first terminal device from the second terminal device. 
     A first terminal device, including: 
     a first acquiring unit, configured to acquire information of synchronizing signals of one or more cells within a base station, where the base station is a base station where the first terminal device or a second terminal device resides; and 
     a first detecting unit, configured to detect for a synchronizing signal sent by the second terminal device, based on the information of the synchronizing signals of the one or more cells and obtain an intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal, where the synchronizing signal sent by the second terminal device is one of the synchronizing signals of the one or more cells. 
     A second terminal device, including: 
     a second acquiring unit, configured to acquire parameter information of sending a synchronizing signal, where the synchronizing signal is one of synchronizing signals of one or more cells within a base station, and the base station is a base station where a first terminal device or the second terminal device resides, where the parameter information includes information of sending the synchronizing signal; and 
     a second sending unit, configured to send the synchronizing signal based on the parameter information, where the synchronizing signal is detected by the first terminal device, and an intensity of the synchronizing signal is obtained by the first terminal device. 
     A base station, including: 
     a third sending unit, configured to send a message to a second terminal device, where the message is for instructing the second terminal device to send a synchronizing signal, where the synchronizing signal is one of synchronizing signals of one or more cells within the base station, and the base station is a base station where a first terminal device or the second terminal device resides; 
     a fourth sending unit, configured to send the information of the synchronizing signals of the one or more cells within the base station to the first terminal device; and 
     a second receiving unit, configured to receive instruction information sent by the first terminal device, where the instruction information includes a determining result made by the first terminal device which indicates whether a D2D network connection can be established between the first terminal device and the second terminal device based on an intensity of the synchronizing signal, or includes the intensity of the synchronizing signal received by the first terminal device from the second terminal device. 
     A terminal device discovery system, including a first terminal device, a second terminal device and a base station, where 
     the first terminal device is configured to acquire information of synchronizing signals of one or more cells within the base station where the first terminal device or the second terminal device resides, and detect a synchronizing signal sent by the second terminal device based on the information of the synchronizing signals of the one or more cells, and obtain an intensity of the synchronizing signal to discover the second terminal device through the synchronizing signal, where the synchronizing signal sent by the second terminal is one of the synchronizing signals of the one or more cells; 
     the second terminal device is configured to acquire parameter information of sending synchronizing signal, where the synchronizing signal is one of the synchronizing signals of the one or more cells within the base station, where the base station is a base station where the first terminal device or the second terminal device resides, where the parameter information includes information of sending the synchronizing signal; and send the synchronizing signal based on the parameter information, where the synchronizing signal is detected by the first terminal device, and the intensity of the synchronizing signal is obtained by the first terminal device; and 
     the base station is configured to send a message to the second terminal device to instruct the second terminal device to send the synchronizing signal, where the synchronizing signal is one of the synchronizing signals of the one or more cells within the base station, where the base station is a base station where the first terminal device or the second terminal device resides, and send the information of the synchronizing signal of the one or more cells within the base station and receive instruction information sent by the first terminal device, where the instruction information includes a determining result made by the first terminal device which indicates whether a D2D network connection can be established between the first terminal device and the second terminal device, or includes the intensity of the synchronizing signal received by the first terminal device from the second terminal device. 
     According to the terminal device discovery method, device and system, the first terminal device acquires the information of the synchronizing signals of one or more cells of within the base station where the first terminal device or the second terminal devices resides; the first terminal device detects a synchronizing signal sent by the second terminal device, based on the information of the synchronizing signals of the one or more cells and obtains an intensity of the synchronizing signal to discover the second terminal device via the synchronizing signal. In the embodiments of the invention, the synchronizing signal sent by the second terminal device is adopted to discover the second terminal device, and then a waste of preamble is avoided, thereby saving the resource of preamble when the base station searches for the terminal device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to clearly specify the technical solutions according to the embodiments of the invention and the conventional technologies, the drawings in the embodiments and the conventional technical solutions may be briefly described. Obviously, the following drawings are only a few of the embodiments of the invention, and those skilled in the art may obtain other drawings according to these drawings without creative work. 
         FIG. 1  is a flowchart showing a terminal device discovery method provided according to an embodiment of the invention; 
         FIG. 2  is a flowchart showing a terminal device discovery method provided according to an embodiment of the invention; 
         FIG. 3  is a flowchart showing a terminal device discovery method provided according to an embodiment of the invention; 
         FIG. 4  is a flowchart showing a terminal device discovery method provided according to another embodiment of the invention; 
         FIG. 5  is a flowchart showing a terminal device discovery method provided according to another embodiment of the invention; 
         FIG. 6  is a flowchart showing a terminal device discovery method provided according to yet another embodiment of the invention; 
         FIG. 7  is a flowchart showing a terminal device discovery method provided according to yet another embodiment of the invention; 
         FIG. 8  is a schematic structure diagram of a first terminal device provided according to an embodiment of the invention; 
         FIG. 9  is a schematic structure diagram of a first terminal device provided according to an embodiment of the invention; 
         FIG. 10  is a schematic structure diagram of a second terminal device provided according to an embodiment of the invention; 
         FIG. 11  is a schematic structure diagram of a second terminal device provided according to an embodiment of the invention; 
         FIG. 12  is a schematic structure diagram of a base station provided according to an embodiment of the invention; 
         FIG. 13  is a schematic structure diagram of a base station provided according to an embodiment of the invention; and 
         FIG. 14  is a schematic structure diagram of a terminal device discovery system provided according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     To make the solutions provided in the invention better understood by those skilled in the art, the technical solutions provided according to the embodiment of the invention may be described in details in conjunction with the drawings used in the embodiment of the invention. Obviously, the embodiments described in the following are only a few of the embodiments of the invention, other embodiments made by those skilled in the art without creatively work based on the embodiments of the invention, fall into the protection scope of the invention. 
     To clarify the advantages of the technical solution provided according to the embodiments of the invention, the invention may be described in detail in conjunction with drawings and embodiments. 
     A terminal device discovery method provided according to an embodiment of the invention is shown in  FIG. 1 . The method is described from a first terminal device side, and includes the steps from Step  101  and Step  102 . 
     Step  101  is to acquire, by a first terminal device, information of synchronizing signals of one or more cells within a base station. 
     The base station is a base station where the first terminal device or a second terminal device resides. 
     By acquiring synchronizing signal information of the base stations where the first terminal device and the second terminal device reside respectively, the first terminal device may learn the synchronizing signal information of the cells which may be sent by the second terminal device potentially, in a way that the synchronizing signal may be detected. 
     Step  102  is to detect, by the first terminal device, a synchronizing signal sent by the second terminal device, based on the information of the synchronizing signals of the one or more cells and obtain an intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal. 
     The synchronizing signal sent by the second terminal device is one of the synchronizing signals of the one or more cells. When the first terminal device performing a detection based on the information of the synchronizing signals, it is indicated that the first terminal device discovers the second terminal device in a case that the first terminal device detects the synchronizing signal successfully, i.e., the first terminal device obtains an intensity of the synchronizing signal sent by the first terminal device by the detection. 
     The synchronizing signal may be at least one of a primary synchronizing signal and a secondary synchronizing signal. 
     A terminal device discovery method provided according to an embodiment of the invention is shown in  FIG. 2 . The method is described from a second terminal device side, and includes the steps from Step  201  and Step  202 . 
     Step  201  is to acquire, by a second terminal device, parameter information of sending a synchronizing signal. 
     The synchronizing signal is one of synchronizing signals of one or more cells within a base station, and the base station is a base station where a first terminal device or the second terminal device resides. The parameter information includes information of sending the synchronizing signal. 
     Step  202  is to send, by the second terminal device, the synchronizing signal based on the parameter information, where the synchronizing signal is detected by the first terminal device and an intensity of the synchronizing signal is obtained by the first terminal device. 
     A terminal device discovery method provided according to an embodiment of the invention is shown in  FIG. 3 . The method described from a base station side, and includes the steps from Step  301  to Step  303 . 
     Step  301  is to send a message to a second terminal device, where the message is for instructing the second terminal device to send a synchronizing signal. 
     The synchronizing signal is one of synchronizing signals of one or more cells within the base station, and the base station is a base station where a first terminal device or the second terminal device resides. 
     The synchronizing signal may be at least one of a primary synchronizing signal and a secondary synchronizing signal. 
     Step  302  is to send information of the synchronizing signals of the one or more cells within the base station to the first terminal device. 
     Step  303  is to receive instruction information sent by the first terminal device. 
     The instruction information includes a determination result made by the first terminal device, which indicates whether a D2D network connection can be established between the first terminal device and the second terminal device, or includes information about the intensity of the synchronizing signal which is sent from the second terminal device to the first terminal device. 
     It may be noted that, the first and the second terminal devices may the same or not, and may be such cell phone, laptop, tablet PC, and the invention is not limited in this aspect. 
     According to the terminal device discovery method provided in the embodiments of the present invention, the first terminal device acquires the information of the synchronizing signals of one or more cells of within the base station where the first terminal device or the second terminal devices reside; the first terminal device detects a synchronizing signal sent by the second terminal device, based on the information of synchronizing signals of one or more cells and obtains the intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal. In the embodiments of the invention, the synchronizing signal sent by the second terminal device is adopted to discover the second terminal device, and then a waste of preamble is avoided, thereby saving the resource of preamble when the base station searches for the terminal device. 
     A terminal device discovery method is provided according to another embodiment of the invention is shown in  FIG. 4 , the method includes the steps from Step  401  to Step  412 . 
     In Step  401 , a first terminal device sends a request for connecting a second terminal device in a D2D manner, to a network where the first terminal device resides. 
     The request may include an identifier of the second terminal device. For example, in a case that the second terminal device is a cell phone, the identifier may be a phone number of the second terminal device, and the invention is not limited in this aspect. 
     The network where the first terminal device resides may include one or more base stations. 
     In Step  402 , one or more base stations in the network where the first terminal device resides send messages respectively to the second terminal device based on the identifier of the second terminal device. 
     The message may be a paging message, and the paging message is for instructing the second terminal device to send a synchronizing signal. The synchronizing signal is one of synchronizing signals of the one or more cells within the base station. The base station may be a base station where the first terminal device or the second terminal device resides. 
     The paging message includes parameter information of sending the synchronizing signal, where the parameter information includes information of sending the synchronizing signal and a location of time-frequency resource at which the synchronizing signal is sent. 
     In Step  403 , the second terminal device receives the message based on the identifier. 
     Once the second terminal device receives the message sent by the base station, and acquires the identifier, the second terminal device may match its own identifier with the identifier acquired. In a case that the two identifiers are the same, it is indicated that the message sent by the base station is used for paging the second terminal device. 
     In Step  404 , the second terminal device sends the synchronizing signal at the time-frequency resource of the cell where the first terminal device or the second terminal device runs. 
     The synchronizing signal may be at least one of a primary synchronizing signal and a secondary synchronizing signal. 
     In Step  405 , the first terminal device receives a broadcasting message or dedicated signalling sent by the base station, where the broadcasting message or the dedicated signalling includes information of synchronizing signals of one or more cells within the base station; or the first terminal device acquires information of synchronizing signals of a cell where the first terminal device or the second terminal device runs, and acquire the location of the time-frequency resource at which the second terminal device sends the synchronizing signal. 
     The cell where the first terminal device or the second terminal device runs is one of the one or more cells mentioned above. 
     The first terminal device may acquire the location of the time-frequency resource at which the second terminal device sends the synchronizing signal based on the identifier of the second terminal device. And the following Step  412  may make a reference to the method of acquiring the location of the time-frequency resource at which the second terminal device sends the synchronizing signal based on the identifier of the second terminal device. 
     In addition, the first terminal device may also receive a first message sent by the base station, where the first message includes the location of the time-frequency resource at which the second terminal device sends the synchronizing signal, and the invention is not limited in this aspect. 
     In Step  406 , the first terminal device detects for the synchronizing signal at the time-frequency resource, based on the information of synchronizing signal of the cell where the first terminal device or the second terminal device runs, and obtains the intensity of the synchronizing signal. Step  407  or Step  409  is performed. 
     The cell where the first terminal device or the second terminal device runs is one of the one or more cells mentioned above. 
     In Step  407 , the first terminal device determines that the first terminal device and the second terminal device run within a coverage area of a same base station or a same cell in a case that the intensity of the synchronizing signal is larger than a predetermined threshold value of signal intensity. 
     Generally, the two devices which are to be connected in a D2D manner may be closed to each other (within a coverage area of a same base station), and the signal intensity may be strong. Therefore, it may be determined based on the predetermined threshold of signal intensity whether the two devices run within a coverage area of a same cell or base station and then determined whether the two devices may be connected in a D2D manner. 
     In Step  408 , the first terminal device sends a request message to the base station where the first terminal device resides, where the request message includes a determining result which indicates whether the first terminal device and the second terminal device run within a coverage area of a same cell or a same base station. And then Step  411  may be performed. 
     In a case that the first terminal device detects the synchronizing signal sent by the second terminal device and learns that the intensity of the synchronizing signal is stronger than the predetermined threshold of signal intensity, it may be determined that the first terminal device and the second terminal device run within a coverage area of a same cell or a same base station. 
     In Step  409 , the first terminal device sends a request message to the base station where the first terminal device resides, where the request message includes information about the intensity of the synchronizing signal. 
     The information about the intensity of the synchronizing signal is for the base station to learn the intensity of the synchronizing signal. 
     In Step  410 , in a case that the base station determines that the intensity of the synchronizing signal is stronger than the predetermined threshold of signal intensity, it may be determined that the first terminal device and the second terminal device run within a coverage area of a same cell or a same base station. Then Step  411  may be performed. 
     In Step  411 , the base station sends a paging message to the first terminal device and the second terminal device, such that the first terminal device and the second terminal device establish a radio resource control connection based on the cell where the first terminal device or the second terminal device runs. 
     In addition, as shown in  FIG. 5 , the paging message in Step  402  may not include a location of time-frequency resource at which the second terminal device sends the synchronizing signal, i.e., the parameter information includes the information of sending the synchronizing signal, such as a command for instructing the second terminal device to send the synchronizing signal at the cell where the first terminal device or the second terminal device runs. The method may include Step  412  between Step  403  and Step  404 . 
     In Step  412 , the second terminal device acquires, based on the identifier, the location of the time-frequency resource at which the second terminal device sends the synchronizing signal. 
     For example, the location of the time-frequency resource at which the synchronizing signal is sent is obtained by performing mod N operation on the identifier, where N may be the number of the time-frequency resource for sending the synchronizing signal. The information of the location of the time-frequency resource at which the synchronizing signal may be sent in the network is broadcasted by base station or is preset. 
     For example, the identifier of the second terminal device is 123456789, the number of the time-frequency resource at which the synchronizing signal may be sent is 100, it may obtain 89 after performing mod 100 on 123456789, and then the serial number of the time-frequency resource for sending the synchronizing signal by the second terminal device is 89. 
     Besides the above method, the location of the time-frequency resource at which the second terminal device sends the synchronizing signal may be determined in other methods, and the invention is not limited in this aspect. 
     According to the terminal device discovery method provided in another embodiment of the present invention, the first terminal device acquires the information of the synchronizing signals of one or more cells of within base stations where the first terminal device or the second terminal device resides; the first terminal device detects a synchronizing signal sent by the second terminal device, based on the information of synchronizing signals of one or more cells and obtains the intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal. In the embodiments of the invention, the synchronizing signal sent by the second terminal device is adopted to discover the second terminal device, and then a waste of preamble is avoided, thereby saving the resource of preamble when the base station searches for the terminal device. 
       FIG. 6  shows a terminal device discovery method provided according to yet another embodiment of the invention, the method includes the steps from Step  501  to Step  515 . 
     In Step  501 , a second terminal device receives a message sent by a base station, where the message sent by the base station is for instructing the second terminal device to send a synchronizing signal, where the message includes parameter information of sending the synchronizing signal. 
     The synchronizing signal is one of synchronizing signal of one or more cells within the base station, and the base station is a base station where a first terminal device or the second terminal device resides. The parameter information includes information of sending the synchronizing signal. 
     The parameter information includes a transmitting period and/or a transmitting power of sending the synchronizing signal configured by the base station for the second terminal device. The second terminal device may send the synchronizing signal via the cell where the first terminal device or the second terminal device runs. 
     In Step  502 , the second terminal device sends the synchronizing signal periodically within a period of time based on the transmitting period and/or the transmitting power. 
     The synchronizing signal may be at least one of a primary synchronizing signal and a secondary synchronizing signal. 
     The second terminal device may send the synchronizing signal periodically within a period of time, for example, the synchronizing signal may be sent every minute or every  10  minutes and the invention is not limited in this aspect. 
     In Step  503 , the first terminal device acquires information of the synchronizing signals of the one or more cells within the base station. 
     The base station is a base station where the first terminal device or the second terminal device resides. 
     By acquiring synchronizing signal information of the base stations where the first terminal device and the second terminal device reside respectively, the first terminal device may learn the synchronizing signal information of the cells which may be sent by the second terminal device potentially, in a way that the synchronizing signal may be detected. 
     In Step  504 , in a case that the first terminal device is required to be connected to the second terminal device in a D2D manner, the first terminal device may detect the synchronizing signal sent by the second terminal device within ranges of synchronizing signal of the one or more cells and obtains the intensity of the synchronizing signal. And then Step  505  may be performed or Step  506  may be performed directly. 
     In Step  505 , the first determines, based the intensity of the synchronizing signal, whether the first terminal device and the second terminal devices run within a coverage area of a same base station or a same cell. And then Step  506  may be performed. 
     Step  407  shown in  FIG. 4  may make a reference for the determination, and detailed description thereof is omitted herein. 
     In Step  506 , the first terminal device sends a request message for connecting to the second terminal device in the D2D manner, to a network where the first terminal device resides. 
     The request message includes a determining result made by the first terminal device, which indicates whether a D2D network connection can be established between the first terminal device and the second terminal device, or includes the intensity of the synchronizing signal. 
     In Step  507 , the base station where the first terminal device resides determines, based on the intensity of the synchronizing signal, whether a D2D network connection can be established between the first terminal device and the second terminal device, or receives directly the determining result sent by the first terminal device. 
     In Step  508 , in a case that it is determined that the a D2D network connection can be established between the first terminal device and the second terminal device, the base station sends a paging message to the first terminal device and the second terminal device, such that the first terminal device and the second terminal device establish a radio resource control connection with the base station based on the cell where the first terminal device or the second terminal device runs. 
     In addition, for determining more accurately whether a D2D network connection can be established between the first terminal device and the second terminal device, a terminal device discovery method is provided according to another embodiment of the invention, as shown in  FIG. 7 . The Step  504  to Step  507  above may be realized by the following steps from Step  509  to Step  515  as follows. 
     In Step  509 , in a case that the first terminal device is required to be connected to the second terminal device in a D2D manner, the first terminal device may detect the synchronizing signal sent by the second terminal device within ranges of synchronizing signal of the one or more cells to detect the second terminal device. 
     In Step  510 , the first terminal device sends a request message for connecting to the second terminal device in the D2D manner, to a network where the first terminal device resides. 
     The request message indicates that the second terminal device is detected. 
     In Step  511 , the base station where the first terminal device resides sends a paging message to the second terminal device. 
     The paging message includes a preamble allocated to the second terminal device by the base station. 
     Specifically, because the second terminal device is already detected by the first terminal device, the base station only allocates one preamble rather than multiple preambles to the second terminal device. 
     In Step  512 , the base station where the first terminal device resides sends information of the preamble to the first terminal device. 
     Specifically, to facilitate the first terminal device in detecting the preamble sent by the second terminal device, the first terminal device needs to learn the information of the preamble, such as a serial number of the preamble. 
     In Step  513 , the second terminal device sends the preamble, to cause the first terminal device receives that preamble and acquires the signal intensity of the preamble. And then Step  514  or  515  may be performed. 
     In Step  514 , the first terminal device determines, based on the signal intensity of the preamble, whether a D2D network connection can be established between the first terminal device and the second terminal device, and sends a determining result to the base station where the first terminal device resides. And then Step  508  may be performed. 
     In Step  515 , the first terminal device sends the signal intensity of the preamble to the base station where the first terminal device resides, such that the base station determines, based on the intensity of the preamble, whether a D2D network connection can be established between the first terminal device and the second terminal device. And then Step  508  may be performed. 
     According to the terminal device discovery method provided in another embodiment of the present invention, the first terminal device acquires the information of the synchronizing signals of one or more cells of within base stations where the first terminal device or the second terminal devices resides; the first terminal device detects a synchronizing signal sent by the second terminal device, based on the information of synchronizing signals of one or more cells and obtains the intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal. In the embodiments of the invention, the synchronizing signal sent by the second terminal device is adopted to discover the second terminal device, and then a waste of preamble is avoided, thereby saving the resource of preamble when the base station searches for the terminal device. 
     As shown in  FIG. 8 , a first terminal device provided according to an embodiment of the invention, includes: 
     a first acquiring unit  61 , configured to acquire information of synchronizing signals of one or more cells within a base station, where the base station is a base station where the first terminal device or a second terminal device resides; 
     a first detecting unit  62 , configured to detect, by the first terminal device, a synchronizing signal sent by the second terminal device, based on the information of synchronizing signals of the one or more cells and obtain an intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal, where the synchronizing signal sent by the second terminal device is one of the synchronizing signals of the one or more cells. 
     Furthermore, as shown in  FIG. 9 , the first terminal device further includes: 
     a first determining unit  63 , configured to determine, based on the intensity of the synchronizing signal, whether a D2D network connection can be established between the first terminal device and the second terminal device; and 
     a first sending unit  64 , configured to send a determining result made by the first determining unit  63  or information about the intensity of the synchronizing signal to the base station. 
     Furthermore, as shown in  FIG. 9 , the first acquisition unit  61  is configured to: 
     receive a broadcasting message or dedicated signalling sent by the base station, where the broadcasting message or the dedicated signalling includes information of the synchronizing signals of the one or more cells within the base stations; or receive information of a synchronizing signal of a cell where the first terminal device or the second terminal device runs, where the cell where the first terminal device or the second terminal device runs is one of the one or more cells mentioned above. 
     Furthermore, as shown in  FIG. 9 , the first determining unit  63  is configured to: 
     determine that a D2D network connection can be established between the first terminal device and the second terminal devices in a case that the intensity of the synchronizing signal is greater than a predetermined threshold of signal intensity. 
     Furthermore, as shown in  FIG. 9 , the first detecting unit  62  includes: 
     a first time-frequency resource location acquiring module  621 , configured to acquire, based on the identifier of the second terminal device, a location of time-frequency resource at which the second terminal device sends the synchronizing signal; 
     a first receiving module  622 , configured to receive a first message sent by the base station, where the first message includes the location of the time-frequency resource at which the second terminal device sends the synchronizing signal; 
     a first detecting module  623 , configured to detect for the synchronizing signal and acquires the intensity of the synchronizing signal at the time-frequency resource, based on the information of the synchronizing signals of the cell where the first terminal device or the second terminal device runs, where the cell where the first terminal device or the second terminal device runs is one of the one or more cells mentioned above. 
     Furthermore, as shown in  FIG. 9 , the first determining unit  63  is configured to: 
     determine, based the acquired intensity of the synchronizing signal, whether the first terminal device and the second terminal device run in a coverage area of a same base station or a same cell. 
     Furthermore, as shown in  FIG. 9 , the first sending unit  64  is configured to: 
     send an instruction information indicating whether the first terminal device and the second terminal device run within a coverage area of a same base station or a same cell to the base station as a determining result. 
     Furthermore, as shown in  FIG. 9 , the first determining unit  63  is configured to: 
     determine that the first terminal device and the second terminal device run within a coverage area of a same base station or a same cell in a case that the synchronizing signal sent by the second terminal device is detected and the intensity of the synchronizing signal is larger than a predetermined threshold value of signal intensity. 
     Furthermore, as shown in  FIG. 9 , the first sending unit  64  is configured to: 
     send a request message for connecting to the second terminal device in a D2D manner to the base station. 
     The request message includes a determining result or the intensity of the synchronizing signal. 
     According to the first terminal device provided in the embodiments of the present invention, the first terminal device acquires the information of the synchronizing signals of one or more cells of within base stations where the first terminal device or the second terminal device resides; the first terminal device detects a synchronizing signal sent by the second terminal device, based on the information of synchronizing signals of one or more cells and obtains the intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal. In the embodiments of the invention, the synchronizing signal sent by the second terminal device is adopted to discover the second terminal device, and then a waste of preamble is avoided, thereby saving the resource of preamble when the base station searches for the terminal device. 
     As shown in  FIG. 10 , a second terminal device is provided according to an embodiment of the invention. The second terminal device includes: 
     a second acquiring unit  71 , configured to acquire parameter information of sending a synchronizing signal, where the synchronizing signal is one of synchronizing signals of one or more cells within a base station, and the base station is a base station where a first terminal device or the second terminal device resides, where the parameter information includes information of sending the synchronizing signal; and 
     a second sending unit  72 , configured to send the synchronizing signal based on the parameter information, where the synchronizing signal is detected by the first terminal device and the intensity of the synchronizing signal is obtained by the first terminal device. 
     Furthermore, as shown in  FIG. 11 , the second acquiring unit  71  includes: 
     a second receiving module  711 , configured to receive a message sent by the base station, where the message includes the parameter information of sending the synchronizing signal; 
     a first acquiring module  712 , configured to acquire the parameter information of sending the synchronizing signal based on an identifier of the second terminal device. 
     Furthermore, as shown in  FIG. 11 , the parameter information further includes information about a location of time-frequency resource, where the second sending unit  72  is configured to: 
     send the synchronizing signal at the time-frequency resource of the cell where the first terminal device or the second terminal device runs. 
       101281  Furthermore, as shown in  FIG. 11 , the parameter information further includes a transmitting period and/or a transmitting power of sending the synchronizing signal, and the second sending unit  72  is configured to: 
     send the synchronizing signal periodically within a period of time based on the transmitting period and/or the transmitting power. 
     Furthermore, the second terminal device shown in  FIG. 11  further includes: 
     a first receiving unit  73 , configured to receive a paging message sent by the base station, where the paging message is for notifying the second terminal device that the first terminal device and the second terminal device have a permission of being connected in a D2D manner; 
     a first connecting unit  74 , configured to establish a radio resource control connection with the base station based on the cell where the first terminal device or the second terminal device runs in a case that the paging message is received. 
     It may be noted that, the synchronizing signal may be at least one of a primary synchronizing signal and a secondary synchronizing signal. 
     According to the second terminal device provided in the embodiments of the present invention, the first terminal device acquires the information of the synchronizing signals of one or more cells of within base stations where the first terminal device or the second terminal device resides; the first terminal device detects a synchronizing signal sent by the second terminal device, based on the information of synchronizing signals of one or more cells and obtains the intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal. In the embodiments of the invention, the synchronizing signal sent by the second terminal device is adopted to discover the second terminal device, and then a waste of preamble is avoided, thereby saving the resource of preamble when the base station searches for the terminal device. 
     As shown in  FIG. 12 , a base station is provided according to an embodiment of the invention the base station includes: 
     a third sending unit  81 , configured to send a message to a second terminal device, where the message is for instructing the second terminal device to send a synchronizing signal, the synchronizing signal is one of synchronizing signals of one or more cells within the base station, and the base station is a base station where a first terminal device or the second terminal device resides; 
     a fourth sending unit  82 , configured to send, to the first terminal device, information of the synchronizing signals of the one or more cells within the base station; 
     a second receiving unit  83 , configured to receive instruction information sent by the first terminal device; the instruction information includes a determining result made by the first terminal device, which indicates whether a D2D network connection can be established between the first terminal device and the second terminal device, or includes information about the intensity of the synchronizing signal received by the first terminal device from the second terminal device. 
     Furthermore, as shown in  FIG. 13 , the instruction information is the information about the intensity of the synchronizing signal received by the first terminal device, the base station further includes: 
     a second determining unit  84 , configured to determine, based on the intensity of the synchronizing signal, whether a D2D network connection can be established between the first terminal device and the second terminal device. 
     Furthermore, as shown in  FIG. 13 , the fourth sending unit  82  is configured to: 
     send a broadcasting message or dedicated signalling to the first terminal device, where the broadcasting message or the dedicated signalling includes information of synchronizing signals of one or more cells within the base station. 
     Furthermore, as shown in  FIG. 13 , the third sending unit  81  is configured to: 
     send a message to the second terminal device, where the message parameter information of the synchronizing signal, where the synchronizing signal is one of sending the synchronizing signals of the one or more cells within the base station, and the base station is a base station where the first terminal or the second terminal device resides. 
     Furthermore, as shown in  FIG. 13 , the second determining unit  84  is configured to: 
     determine whether a D2D network connection can be established between the first terminal device and the second terminal device by determining whether the first terminal device and the second terminal device run with a coverage area of a same base station or a same cell. 
     According to the base station provided in the embodiments of the present invention, the first terminal device acquires the information of the synchronizing signals of one or more cells of within base stations where the first terminal device or the second terminal device resides; the first terminal device detects a synchronizing signal sent by the second terminal device, based on the information of synchronizing signals of one or more cells and obtains the intensity of the synchronizing signal, to discover the second terminal device via the synchronizing signal. In the embodiments of the invention, the synchronizing signal sent by the second terminal device is adopted to discover the second terminal device, and then a waste of preamble is avoided, thereby saving the resource of preamble when the base station searches for the terminal device. 
     As shown in  FIG. 14 , a terminal device discovery system is provided according to an embodiment of the invention. The system includes a first terminal device  91 , a second terminal device  92  and a base station  93 . 
     The first terminal device  91  is configured to acquire information of synchronizing signals of one or more cells within the base station  93  where the first terminal device  91  or the second terminal device  92  resides, and detect a synchronizing signal sent by the second terminal device  92  based on the information of synchronizing signals of one or more cells, and acquire an intensity of the synchronizing signal to discover the second terminal device  92  through the synchronizing signal, where the synchronizing signal sent by the second terminal  92  is one of the synchronizing signals of the one or more cells. 
     The second terminal device  92  is configured to acquire parameter information of sending the synchronizing signal, where the synchronizing signal is one of the synchronizing signals of the one or more cells within the base station  93 , where the base station  93  is a base station where the first terminal device  92  or the second terminal device  93  resides, where the parameter information includes the information of sending the synchronizing signal; send the synchronizing signal based on the parameter information, where the synchronizing signal is detected by the first terminal device  91 , and the intensity of the synchronizing signal is obtained by the first terminal device. 
     The base station  93  is configured to send a message to the second terminal device  92  to instruct the second terminal device  92  to send the synchronizing signal, where the synchronizing signal is one of the synchronizing signals of the one or more cells within the base station  93 , where the base station  93  is a base station where the first terminal device  92  or the second terminal device  93  resides; send the information of the synchronizing signals of the one or more cells within the base station  93  and receive instruction information sent by the first terminal device  91 , where the instruction information includes a determining result made by the first terminal device  91  which indicates whether a D2D network connection can be established between the first terminal device  91  and the second terminal device  92 , or includes the intensity of the synchronizing signal received by the first terminal device  91  from the second terminal device  92 . 
     The embodiment of the first terminal device, the second terminal device and the base station may make a reference for the implementation, and detailed description thereof is omitted herein. 
     By the terminal device discovery system provided according to the embodiments of the invention, the first terminal device acquires the information of the synchronizing signals of one or more cells of within base stations where the first terminal device or the second terminal devices resides; the first terminal device detects a synchronizing signal sent by the second terminal device, based on the information of synchronizing signals of one or more cells and obtains an intensity of the synchronizing signal in a way to discover the second terminal device via the synchronizing signal. In the embodiments of the invention, the synchronizing signal sent by the second terminal device is adopted to discover the second terminal device, and then a waste of preamble is avoided, thereby saving the resource of preamble when the base station searches for the terminal device. 
     By the foregoing description of the embodiments, those skilled in the art may understand clearly that the present invention may be implemented via software and necessary hardware platform, or via the hardware only; in most cases, the former is preferable. In view of this, all or part of the embodiments of the invention may be implemented by software product, where the software product may be stored in readable storage medium, such as ROM/RAM, disk or optical disk, and multiple instructions are included in the software product to enable a computer device (personal computer, server or network device) to implement the method provided according to each embodiment or certain part of the embodiment of the invention. 
     Several ways for implementing the invention are provided according to the above embodiments, which are described specifically and are not limited the scope of the invention. It is noted that some changes and modifications can be made by those skilled in the art with the principle of the invention, may fall into the protection scope of the invention.