Patent Publication Number: US-9894685-B2

Title: Licensed assisted access network system

Description:
PRIORITY 
     This application claims priority to U.S. Provisional Patent Application No. 62/109,017 filed on Jan. 28, 2015, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The present invention relates to a licensed assisted access network system. More particularly, in the licensed assisted access network architecture of the present invention, a mobile station assists a base station in communication scheduling. 
     BACKGROUND 
     In conventional 3 rd  Generation Partnership Project (3GPP) networks, telecommunication operators transmit data mainly through respective licensed bands; however, the efficiency of this kind of data transmission is limited by the bandwidth of the licensed bands. Accordingly, the licensed assisted access (LAA) technology has thus been developed. 
     Specifically, the LAA technology mainly uses licensed bands to transmit control messages and uses unlicensed bands to assist in transmitting network data. In this way, by using the unlicensed bands, the network data transmission efficiency can be effectively improved. The unlicensed band selection and the communication scheduling of the data transmission are all dominated by the base station; however, this technology has a drawback that the network resource use efficiency is low. 
     In detail, in the communication scheduling of the LAA technology, communication interference to the mobile station may be formed in a contention region when different base stations select a same unlicensed band. On the other hand, when different base stations select different unlicensed bands, the network resource cannot be reused in a contention free region. Furthermore, because the base station needs to be responsible for the band selection and the Listen Before Talk (LBT) procedure of all mobile stations, the load of the base station will become a bottleneck in performance as the number of the mobile stations increases. 
     Accordingly, an urgent need exists in the art to overcome the drawbacks of the aforesaid conventional LAA technology, improve the network resource use efficiency and meanwhile reduce the load of the base station. 
     SUMMARY 
     An objective of the present invention is to provide a licensed assisted access (LAA) network system. The disclosure includes an LAA network system comprising a mobile station and a first base station. In the LAA network system: (a) the mobile station determines a use status of an unlicensed band and generates first available unlicensed channel group information; (b) the mobile station transmits the first available unlicensed channel group information to the first base station; (c) the first base station selects a first unlicensed channel according to the first available unlicensed channel group information; and (d) the first base station initializes a communication schedule assessment procedure with the mobile station via the first unlicensed channel. 
     The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic view of an LAA network system according to a first embodiment of the present invention; 
         FIG. 1B  is a block diagram of a mobile station according to the first embodiment of the present invention; 
         FIG. 1C  is a block diagram of a first base station according to the first embodiment of the present invention; 
         FIG. 2A  to  FIG. 2B  are schematic views of an LAA network system according to a second embodiment of the present invention; 
         FIG. 3A  to  FIG. 3B  are schematic views of an LAA network system according to a third embodiment of the present invention; 
         FIG. 4A  to  FIG. 4C  are schematic views of an LAA network system according to a fourth embodiment of the present invention; 
         FIG. 5A  to  FIG. 5C  are schematic views of an LAA network system according to a fifth embodiment of the present invention; 
         FIG. 6  is a schematic view of an LAA network system according to a sixth embodiment of the present invention; 
         FIG. 7  is a flowchart diagram of a channel access method according to a seventh embodiment of the present invention; 
         FIG. 8  is a flowchart diagram of a channel access method according to an eighth embodiment of the present invention; 
         FIG. 9  is a flowchart diagram of a channel access method according to a ninth embodiment of the present invention; 
         FIG. 10  is a flowchart diagram of a channel access method according to a tenth embodiment of the present invention; 
         FIG. 11  is a flowchart diagram of a channel access method according to an eleventh embodiment of the present invention; 
         FIG. 12  is a flowchart diagram of a channel access method according to a twelfth embodiment of the present invention; 
         FIG. 13  is a flowchart diagram of a channel access method according to a thirteenth embodiment of the present invention; 
         FIG. 14  is a flowchart diagram of a channel access method according to a fourteenth embodiment of the present invention; 
         FIG. 15  is a flowchart diagram of a channel access method according to a fifteenth embodiment of the present invention; and 
         FIG. 16  is a flowchart diagram of a channel access method according to a sixteenth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, the present invention will be explained with reference to example embodiments thereof. However, these example embodiments are not intended to limit the present invention to any specific example, embodiment, environment, applications or implementations described in these example embodiments. Therefore, description of these example embodiments is only for purpose of illustration rather than to limit the present invention. In the following embodiments and the attached drawings, elements unrelated to the present invention are omitted from depiction; and dimensional relationships among individual elements in the attached drawings are illustrated only for ease of understanding, but not to limit the actual scale. 
     Please refer to  FIG. 1A  to  FIG. 1C  together, and  FIG. 1A  is a schematic view of a licensed assisted access (LAA) network system  1  according to a first embodiment of the present invention. The LAA network system  1  comprises a mobile station  11  and a first base station  13 .  FIG. 1B  is a block diagram of the mobile station  11  according to the present invention, and the mobile station  11  comprises a processor  111  and a transceiver  113 .  FIG. 1C  is a block diagram of the first base station  13  according to the present invention, and the first base station  13  comprises a processor  131  and a transceiver  133 . The interaction between the LAA network system  1  and the devices thereof will be further described hereinafter. 
     First, as shown in  FIG. 1A , the processor  111  of the mobile station  11  determines a use status (not shown) of an unlicensed band via the transceiver  113 , and accordingly generates first available unlicensed channel group information  110 . The first available unlicensed channel group information  110  records at least one idle and available unlicensed channel, and in this embodiment, the first available unlicensed channel group information  110  records a first unlicensed channel UCH 1 . 
     Next, the transceiver  113  of the mobile station  11  transmits the first available unlicensed channel group information  110  to the first base station  13 . In other words, the transceiver  133  of the first base station  13  receives the first available unlicensed channel group information  110  from the mobile station  11 . Thereafter, the processor  131  of the first base station  13  selects the first unlicensed channel UCH 1  according to the unlicensed channel information  110 . 
     Finally, the processor  131  of the first base station  13  initializes a communication schedule assessment procedure (not shown) with the mobile station  11  through the first unlicensed channel UCH 1  and via the transceiver  133 . In other words, the processor  111  of the mobile station  11  initializes a communication schedule assessment procedure with the first base station  13  through the first unlicensed channel UCH 1  and via the transceiver  113 . In this way, the mobile station assists in determining the unlicensed channel and reports the determination result to the base station so that the base station can more clearly learn the channel use demand of each mobile station to improve the network resource utilization ratio and meanwhile reduce the load of the base station. 
     It shall be particularly appreciated that, the aforesaid communication schedule assessment procedure may comprise steps including: (1) assessing whether the channel is available, and if it is determined that the channel is available after the assessment, then performing channel resource scheduling for the available channel and deciding that the scheduling succeeds; or (2) deciding that the schedule fails if it is determined that the channel is unavailable after the assessment. The technical meaning of the communication schedule assessment procedure in the present invention shall be readily appreciated by those skilled in the art according to the disclosure of the present invention, and thus will not be further described herein. 
     Please refer to  FIG. 2A  to  FIG. 2B , which are schematic views of an LAA network system  1  according to a second embodiment of the present invention. The architecture of the second embodiment is similar to that of the first embodiment, so elements labeled by the same reference numerals have the same functions and thus will not be further described herein. However, the second embodiment mainly describes in more detail the processing for the success or the failure of the communication schedule assessment procedure. 
     Further speaking, as shown in  FIG. 2A , after the mobile station  11  initializes the communication schedule assessment procedure with the first base station  13  through the first unlicensed channel UCH 1 , the processor  131  of the first base station  13  accordingly determines that the communication schedule assessment procedure succeeds after assessing that the first unlicensed channel UCH 1  is available (i.e., has not yet been occupied by other devices and is in a good channel status), and the first base station  13  directly transmits schedule information  130  to the mobile station  11  through the first unlicensed channel UCH 1  and via the transceiver  133 . In other words, the transceiver  113  of the mobile station  11  may receive the schedule information  130  from the first base station  13  through the first unlicensed channel UCH 1 . 
     On the other hand, as shown in  FIG. 2B , after the mobile station  11  initializes the communication schedule assessment procedure with the first base station  13  through the first unlicensed channel UCH 1 , the processor  111  of the mobile station  11  may again determine a use status of the unlicensed band after determining that the communication schedule assessment procedure fails and generate second available unlicensed channel group information  112 . The second available unlicensed channel group information  112  records a second unlicensed channel UCH 2 . 
     Next, similarly, the transceiver  113  of the mobile station  11  transmits the second available unlicensed channel group information  112  to the first base station  13 . In other words, the transceiver  133  of the first base station  13  receives the second available unlicensed channel group information  112  from the mobile station  11 . Thereafter, the processor  131  of the first base station  13  selects the second unlicensed channel UCH 2  according to the second available unlicensed channel group information  112 . 
     Finally, the processor  131  of the first base station  13  reinitializes a communication schedule assessment procedure with the mobile station  11  through the second unlicensed channel UCH 2  and via the transceiver  133 . In other words, the processor  111  of the mobile station  11  reinitializes a communication schedule assessment procedure with the first base station  13  through the second unlicensed channel UCH 2  and via the transceiver  113 . In this way, after the communication schedule assessment procedure fails, the communication schedule assessment procedure may still be reinitialized via the same steps between the mobile station and the first base station. 
     It shall be particularly appreciated that, the situation where the aforesaid communication schedule assessment procedure fails may be that the mobile station has not received a base station communication instruction within a particular time period or the mobile station directly receives a procedure failure instruction from the base station. The steps and processes thereof shall be readily appreciated by those skilled in the art according to the disclosure of the present invention, and thus will not be further described herein. Moreover, the schedule information may comprise relevant uplink or downlink transmission schedule information, which may also be appreciated by those skilled in the art and thus will not be further described herein. 
     Please refer to  FIG. 3A  to  FIG. 3B , which are schematic views of an LAA network system  1  according to a third embodiment of the present invention. The architecture of the third embodiment is similar to that of the aforesaid embodiments, so elements labeled by the same reference numerals have the same functions and thus will not be further described herein. However, the third embodiment mainly describes in more detail how the mobile station determines the use status of the unlicensed band. 
     Specifically, the mobile station may first receive the use information of unlicensed channels of other base stations from the other base stations, so the use status of the unlicensed channel within the communication coverage of the mobile station may be accordingly determined. As shown in  FIG. 3A , the mobile station  11  may receive relevant information of a licensed channel CH 1  from a second base station  15 , and thereby connect to the second base station  15  via the licensed channel CH 1 . Therefore, the transceiver  113  of the mobile station  11  may receive unlicensed channel schedule information  150  from the second base station  15  via the licensed channel CH 1 . The unlicensed channel schedule information  150  records the use status of the unlicensed channel within the communication coverage of the second base station  15 . 
     In this way, the processor  111  of the mobile station  11  can determine the use status of the unlicensed band according to the unlicensed channel schedule information  150  and thereby avoid the unlicensed channel used by the second base station  15  so as to generate the first available unlicensed channel group information  110 . 
     In another implementation, the processor  111  of the mobile station  11  receives at least one piece of channel reservation information CRI within the unlicensed band via the transceiver  113  as shown in  FIG. 3B . The at least one piece of channel reservation information may be the channel reservation information transmitted on a particular unlicensed channel by other base stations (other than the first base station) or mobile stations served by the other base stations to reserve the particular unlicensed channel. 
     In this way, the processor  111  of the mobile station  11  can learn which unlicensed channels have been reserved according to the at least one piece of channel reservation information CRI via the transceiver  113 , thereby generating the first available unlicensed channel group information  110 . 
     Please refer to  FIG. 4A  to  FIG. 4C , which are schematic views of an LAA network system  1  according to a fourth embodiment of the present invention. The architecture of the fourth embodiment is similar to that of the aforesaid embodiments, so elements labeled by the same reference numerals have the same functions and thus will not be further described herein. However, the fourth embodiment mainly describes in more detail how the mobile station transmits the unlicensed channel information to the base station and how the communication schedule assessment procedure is reinitialized after it fails. 
     Specifically, the mobile station may directly transmit the unlicensed channel information to the base station through the licensed channel. As shown in  FIG. 4A , the mobile station  11  communicates with the first base station  13  through a licensed channel CH 2 . Therefore, in the situation where the licensed channel CH 2  is highly independent, the transceiver  113  of the mobile station  11  may directly transmit the first available unlicensed channel group information  110  to the first base station  13  through the licensed channel CH 2 . In other words, the transceiver  133  of the first base station  13  receives the first available unlicensed channel group information  110  from the mobile station  11  through the licensed channel CH 2 . 
     As shown in  FIG. 4B , when the mobile station  11  communicates with the first base station  13  through the licensed channel CH 2 , the processor  131  of the first base station  13  transmits channel measurement request information  132  to the mobile station  11  through the licensed channel CH 2  and via the transceiver  133  after initializing the communication schedule assessment procedure and determining that the communication schedule assessment procedure fails. In other words, the transceiver  113  of the mobile station  11  receives the channel measurement request information  132  from the first base station  13 . 
     It shall be additionally appreciated that, in other implementations, the communication schedule assessment procedure may comprise the Listen Before Talk (LBT) assessment technology to assess whether the channel is available. If the LBT fails, then it means that the initialization of the communication schedule assessment procedure fails. The application of the LBT shall be readily appreciated by those skilled in the art according to the above disclosure of the present invention, and thus will not be further described herein. 
     Thereafter, similarly, the processor  111  of the mobile station  11  determines the use status of other unlicensed bands according to the channel measurement request information  132  and generates second available unlicensed channel group information  112 . The second available unlicensed channel group information  112  records the second unlicensed channel UCH 2 . 
     Next, similarly, the transceiver  113  of the mobile station  11  transmits the second available unlicensed channel group information  112  to the first base station  13 . In other words, the transceiver  133  of the first base station  13  receives the second available unlicensed channel group information  112  from the mobile station  11 . Thereafter, the processor  131  of the first base station  13  selects the second unlicensed channel UCH 2  according to the second available unlicensed channel group information  112 . 
     Finally, the processor  131  of the first base station  13  reinitializes a communication schedule assessment procedure with the mobile station  11  through the second unlicensed channel UCH 2  and via the transceiver  133 . In other words, the processor  111  of the mobile station  11  reinitializes a communication schedule assessment procedure with the first base station  13  through the second unlicensed channel UCH 2  and via the transceiver  113 . 
     In another implementation, the mobile station may determine on its own that the communication schedule fails and reinitialize the communication schedule assessment procedure. As shown in  FIG. 4C , the processor  111  of the mobile station  11  determines that no schedule information of the first base station  13  is received in the licensed channel CH 2  via the transceiver  113  during a time period (not shown), which means that the first base station  13  cannot use the first unlicensed channel UCH 1  for data transmission. 
     Accordingly, the processor  111  of the mobile station  11  can determine that the communication schedule fails and again determine the use status of the unlicensed band via the transceiver  113  to generate the second available unlicensed channel group information  112 . Next, the transceiver  113  of the mobile station  11  transmits the second available unlicensed channel group information  112  to the first base station  13 . In other words, the transceiver of the first base station  13  receives the second available unlicensed channel group information  112  from the mobile station  11 . 
     Next, the processor  131  of the first base station  13  can select the second unlicensed channel UCH 2  according to the second available unlicensed channel group information  112  and reinitialize the communication schedule assessment procedure with the mobile station  11  through the second unlicensed channel UCH 2  and via the transceiver  133 . In other words, the processor  111  of the mobile station  11  reinitializes the communication schedule assessment procedure with the first base station  13  through the second unlicensed channel UCH 2  and via the transceiver  113 . 
     Please refer to  FIG. 5A  to  FIG. 5C , which are schematic views of an LAA network system  1  according to a fifth embodiment of the present invention. The architecture of the fifth embodiment is similar to that of the aforesaid embodiments, so elements labeled by the same reference numerals have the same functions and thus will not be further described herein. However, the fifth embodiment mainly describes other implementations in more detail, e.g., how the mobile station transmits the unlicensed channel information to the base station and how the communication schedule assessment procedure is reinitialized after it fails. 
     Specifically, the available unlicensed channel information may comprise the channel reservation information, and the mobile station may continuously transmit the channel reservation information to the base station directly in the unlicensed channel. As shown in  FIG. 5A , the first available unlicensed channel group information  110  comprises channel reservation information  110   a , and the transceiver  113  of the mobile station  11  may continuously transmit the channel reservation information  110   a  to the first base station  13  directly in the first unlicensed channel UCH 1 . In other words, the transceiver  133  of the first base station  13  continuously receives the channel reservation information  110   a  from the mobile station  11  through the unlicensed channel UCH 1 . 
     In an implementation, as shown in  FIG. 5B , the transceiver  133  of the first base station  13  detects the channel reservation information  110   a  of the mobile station  11  in the first unlicensed channel UCH 1 , which means that the mobile station  11  has made reservation for the first unlicensed channel UCH 1 . Therefore, the processor  131  of the first base station  13  accordingly selects the first unlicensed channel UCH 1 . 
     Next, the processor  131  of the first base station  13  further determines whether a signal quality (not shown) of the channel reservation information  110   a  of the first unlicensed channel UCH 1  exceeds a threshold (not shown). If the determination result is no, then it means that the signal transmission between the mobile station  11  and the first base station  13  through the first unlicensed channel UCH 1  may be unstable, so the communication schedule assessment procedure is reinitialized in the way described in the previous embodiments. 
     On the other hand, if the signal quality of the channel reservation information  110   a  exceeds the threshold, then the first base station  13  may prepare to communicate with the mobile station  11 . Therefore, the transceiver  133  of the first base station  13  transmits a stop channel reservation notice  134  to the mobile station  11  and prepares to transmit schedule information  130  (e.g., the uplink or downlink schedule information) through the first unlicensed channel UCH 1 . 
     It shall be particularly appreciated that, the signal quality may be determined by the Signal Noise Ratio (SNR), the signal power or the like and the quality threshold may also be adjusted according to the network environment, and this shall be appreciated by those skilled in the art and thus will not be further described herein. 
     On the other hand, the transceiver  113  of the mobile station  11  stops transmitting the channel reservation information  110   a  to the first base station  13  after receiving the stop channel reservation notice  134  from the first base station  13 . Thereafter, the transceiver  113  of the mobile station  11  receives the schedule information  130  from the first base station  13  through the first unlicensed channel UCH 1 . 
     In another implementation, as shown in  FIG. 5C , the transceiver  133  of the first base station  13  similarly detects the channel reservation information  110   a  of the mobile station  11  in the first unlicensed channel UCH 1 , which means that the mobile station  11  has made reservation for the first unlicensed channel UCH 1 . Therefore, the processor  131  of the first base station  13  accordingly selects the first unlicensed channel UCH 1 . 
     Next, the processor  131  of the first base station  13  further determines whether the signal quality of the channel reservation information  110   a  of the first unlicensed channel UCH 1  exceeds a threshold. If the determination result is no, then it means that the signal transmission between the mobile station  11  and the first base station  13  through the first unlicensed channel UCH 1  may be unstable, so the communication schedule assessment procedure is reinitialized in the way described in the previous embodiments. 
     On the other hand, if the determination result is yes, then the first base station  13  may directly transmit the schedule information  130  to the mobile station  11  through the first unlicensed channel UCH 1  and via the transceiver  133  without first notifying the mobile station  11  with an additional notice message. The processor  111  of the mobile station  11  may directly stop transmitting the channel reservation information  110   a  from the time instant at which the transceiver  113  receives the schedule information  130 . 
     Please refer to  FIG. 6 , which is a schematic view of an LAA network system  1  according to a sixth embodiment of the present invention. The architecture of the sixth embodiment is similar to that of the aforesaid embodiments, so elements labeled by the same reference numerals have the same functions and thus will not be further described herein. However, the sixth embodiment mainly describes in more detail how the mobile station transmits the relevant information using both the unlicensed channel and the licensed channel. 
     Specifically, in the sixth embodiment, the first available unlicensed channel group information  110  comprises channel reservation information  110   b , and the transceiver  113  of the mobile station  11  continuously transmits the channel reservation information  110   b  in the first unlicensed channel UCH 1  mainly for notifying other devices that the first unlicensed channel UCH 1  has been reserved. On the other hand, the transceiver  113  of the mobile station  11  transmits the first available unlicensed channel group information  110  to the first base station  13  through the licensed channel CH 2 . 
     Next, after the mobile station  11  initializes the communication schedule assessment procedure with the first base station  13 , the processor  131  of the first base station  13  determines whether a signal quality (not shown) of the channel reservation information  110   b  of the first unlicensed channel UCH 1  exceeds a threshold according to the first available unlicensed channel group information  110 . If the determination result is no, then it means that the signal transmission between the mobile station  11  and the first base station  13  through the first unlicensed channel UCH 1  may be unstable, so the communication schedule assessment procedure is reinitialized in the way described in the previous embodiments. 
     On the other hand, if the signal quality of the channel reservation information  110   b  exceeds the threshold, then the first base station  13  may prepare to communicate with the mobile station  11 . In the case where the mobile station  11  continuously reserves the first unlicensed channel UCH 1  via the channel reservation information  110   b , the transceiver  133  of the first base station  13  may directly transmit the schedule information  130  to the mobile station  11  through the first unlicensed channel UCH 1 . 
     In more detail, in the sixth embodiment, the technology of transmitting the first available unlicensed channel group information  110  through the licensed channel CH 2  is mainly intended to directly allow the devices to select the channel according to the first available unlicensed channel group information  110  by virtue of the stability of the licensed channel CH 2 . Continuously transmitting the channel reservation information  110   b  in the first unlicensed channel UCH 1  is mainly intended to preoccupy the available channel and allow the base station to directly perform the channel assessment of the first unlicensed channel UCH 1  by using the channel reservation information  110   b.    
     It shall be particularly appreciated that, in the aforesaid embodiments, if the channel reservation information is uplink information when the channel reservation information is transmitted in the unlicensed channel, then the channel reservation information may also be directly used as the uplink channel scheduling request message and may carry relevant information such as a buffer status report. 
     Additionally, in the aforesaid embodiments, the channel reservation information may also be one of a channel reservation signal sequence and a channel reservation message packet. The channel reservation message packet is transmitted in the unlicensed channel or the licensed channel, and may carry the channel communication quality, the channel use status and the device-related information at the same time. 
     Besides reserving the channel by directly occupying the channel, the channel reservation signal sequence can also give corresponding information or allow other devices to assess the channel status via the patterns of different signal sequences. The relevant technical content and application shall be readily appreciated by those skilled in the art according to the above disclosure, and thus will not be further described herein. 
     A seventh embodiment of the present invention is a channel access method, referring to  FIG. 7  for a flowchart diagram of the method. The method of the seventh embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the seventh embodiment are as follows. 
     First, step  701  is executed to enable the mobile station to determine a use status of an unlicensed band and generate first available unlicensed channel group information. Step  702  is executed to enable the mobile station to transmit the first available unlicensed channel group information to the first base station. The first available unlicensed channel group information records an available status of a first unlicensed channel. 
     Next, step  703  is executed to enable the first base station to select a first unlicensed channel to communicate with the mobile station according to the first available unlicensed channel group information. Finally, step  704  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. 
     An eighth embodiment of the present invention is a channel access method, referring to  FIG. 8  for a flowchart diagram of the method. The method of the eighth embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the eighth embodiment are as follows. 
     First, step  801  is executed to enable the mobile station to determine a use status of an unlicensed band and generate first available unlicensed channel group information. Step  802  is executed to enable the mobile station to transmit the first available unlicensed channel group information to the first base station. The first available unlicensed channel group information records an available status of a first unlicensed channel. 
     Next, step  803  is executed to enable the first base station to select a first unlicensed channel to communicate with the mobile station according to the first available unlicensed channel group information. Thereafter, step  804  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. Step  805  is executed to enable the mobile station to determine that the communication schedule assessment procedure fails. Step  806  is executed to enable the mobile station to determine a use status of the unlicensed band according to the determination result of the step  805  and generate second available unlicensed channel group information. 
     Step  807  is executed to enable the mobile station to transmit the second available unlicensed channel group information to the first base station. Step  808  is executed to enable the first base station to select a second unlicensed channel according to the second available unlicensed channel group information. Finally, step  809  is executed to enable the first base station to reinitialize the communication schedule assessment procedure with the mobile station through the second unlicensed channel. 
     A ninth embodiment of the present invention is a channel access method, referring to  FIG. 9  for a flowchart diagram of the method. The method of the ninth embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the ninth embodiment are as follows. 
     First, step  901  is executed to enable the mobile station to determine a use status of an unlicensed band and generate first available unlicensed channel group information. Step  902  is executed to enable the mobile station to transmit the first available unlicensed channel group information to the first base station. The first available unlicensed channel group information records an available status of a first unlicensed channel. Step  903  is executed to enable the first base station to select a first unlicensed channel to communicate with the mobile station according to the first available unlicensed channel group information. 
     Next, step  904  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. Step  905  is executed to enable the first base station to assess that the first unlicensed channel is available. Step  906  is executed to enable the first base station to determine that the communication schedule assessment procedure succeeds. Finally, step  907  is executed to enable the first base station to transmit schedule information to the mobile station through the first unlicensed channel according to the result of the step  905 . 
     A tenth embodiment of the present invention is a channel access method, referring to  FIG. 10  for a flowchart diagram of the method. The method of the tenth embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the tenth embodiment are as follows. 
     First, step  1001  is executed to enable the mobile station to determine a use status of an unlicensed band and generate first available unlicensed channel group information. Step  1002  is executed to enable the mobile station to transmit the first available unlicensed channel group information to the first base station through a licensed channel. The first available unlicensed channel group information records an available status of a first unlicensed channel. 
     Next, step  1003  is executed to enable the first base station to select a first unlicensed channel to communicate with the mobile station according to the first available unlicensed channel group information. Step  1004  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. The communication schedule assessment procedure may comprise an LBT procedure to perform channel assessment and measurement. 
     Step  1005  is executed to enable the first base station to determine that the communication schedule assessment procedure fails (e.g., the LBT assessment result fails) and transmit channel measurement request information to the mobile station through the licensed channel. Step  1006  is executed to enable the mobile station to determine a use status of the unlicensed band according to the channel measurement request information and generate second available unlicensed channel group information. 
     Thereafter, step  1007  is executed to enable the mobile station to transmit the second available unlicensed channel group information to the first base station. Step  1008  is executed to enable the first base station to select a second unlicensed channel according to the second available unlicensed channel group information. Finally, step  1009  is executed to enable the first base station to reinitialize the communication schedule assessment procedure with the mobile station through the second unlicensed channel. 
     An eleventh embodiment of the present invention is a channel access method, referring to  FIG. 11  for a flowchart diagram of the method. The method of the eleventh embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the eleventh embodiment are as follows. 
     First, step  1101  is executed to enable the mobile station to determine a use status of an unlicensed band and generate first available unlicensed channel group information. Step  1102  is executed to enable the mobile station to transmit the first available unlicensed channel group information to the first base station through a licensed channel. The first available unlicensed channel group information records an available status of a first unlicensed channel. 
     Next, step  1103  is executed to enable the first base station to select a first unlicensed channel to communicate with the mobile station according to the first available unlicensed channel group information. Step  1104  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. Step  1105  is executed to enable the mobile station to determine that no schedule information of the first base station is received in the licensed channel during a time period. 
     Thereafter, step  1106  is executed to enable the mobile station to determine that the communication schedule fails according to the result of the step  1105 . Step  1107  is executed to enable the mobile station to determine a use status of the unlicensed band according to the result of the step  1106  and generate second available unlicensed channel group information. 
     Step  1108  is executed to enable the mobile station to transmit the second available unlicensed channel group information to the first base station. Step  1109  is executed to enable the first base station to select a second unlicensed channel according to the second available unlicensed channel group information. Finally, step  1110  is executed to enable the first base station to reinitialize the communication schedule assessment procedure with the mobile station through the second unlicensed channel. 
     A twelfth embodiment of the present invention is a channel access method, referring to  FIG. 12  for a flowchart diagram of the method. The method of the twelfth embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the twelfth embodiment are as follows. 
     First, step  1201  is executed to enable the mobile station to receive unlicensed channel schedule information from a second base station through a licensed channel. Step  1202  is executed to enable the mobile station to determine a use status of the unlicensed band according to the unlicensed channel schedule information and generate the first available unlicensed channel group information. 
     Step  1203  is executed to enable the mobile station to transmit the first available unlicensed channel group information to the first base station. The first available unlicensed channel group information records an available status of a first unlicensed channel. Step  1204  is executed to enable the first base station to select a first unlicensed channel to communicate with the mobile station according to the first available unlicensed channel group information. Finally, step  1205  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. 
     A thirteenth embodiment of the present invention is a channel access method, referring to  FIG. 13  for a flowchart diagram of the method. The method of the thirteenth embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the thirteenth embodiment are as follows. 
     First, step  1301  is executed to enable the mobile station to measure at least one piece of channel reservation information (CRI) of the unlicensed band. Step  1302  is executed to enable the mobile station to generate the first available unlicensed channel group information according to the at least one piece of channel reservation information. Step  1303  is executed to enable the mobile station to transmit the first available unlicensed channel group information to the first base station. The first available unlicensed channel group information records an available status of a first unlicensed channel. 
     Step  1304  is executed to enable the first base station to select a first unlicensed channel to communicate with the mobile station according to the first available unlicensed channel group information. Finally, step  1305  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. 
     A fourteenth embodiment of the present invention is a channel access method, referring to  FIG. 14  for a flowchart diagram of the method. The method of the fourteenth embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the fourteenth embodiment are as follows. 
     First, step  1401  is executed to enable the mobile station to determine a use status of an unlicensed band and generate first available unlicensed channel group information. The first available unlicensed channel group information records an available status of a first unlicensed channel. Step  1402  is executed to enable the mobile station to continuously transmit channel reservation information to the first base station through the first unlicensed channel. 
     Next, step  1403  is executed to enable the first base station to detect the channel reservation information in the first unlicensed channel. Step  1404  is executed to enable the first base station to select the first unlicensed channel to communicate with the mobile station according to the result of the step  1403 . Step  1405  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. 
     Thereafter, step  1406  is executed to enable the first base station to determine that a signal quality of the channel reservation information of the first unlicensed channel exceeds a threshold. Step  1407  is executed to enable the first base station to transmit a stop channel reservation notice to the mobile station and transmit schedule information to the mobile station through the first unlicensed channel according to the result of the step  1406 . Finally, step  1408  is executed to enable the mobile station to stop transmitting the channel reservation information to the first base station according to the stop channel reservation notice and receive the schedule information. 
     A fifteenth embodiment of the present invention is a channel access method, referring to  FIG. 15  for a flowchart diagram of the method. The method of the fifteenth embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the fifteenth embodiment are as follows. 
     First, step  1501  is executed to enable the mobile station to determine a use status of an unlicensed band and generate first available unlicensed channel group information. The first available unlicensed channel group information records an available status of a first unlicensed channel. Step  1502  is executed to enable the mobile station to continuously transmit channel reservation information to the first base station through the first unlicensed channel. 
     Next, step  1503  is executed to enable the first base station to detect the channel reservation information in the first unlicensed channel. Step  1504  is executed to enable the first base station to select the first unlicensed channel to communicate with the mobile station according to the result of the step  1503 . Step  1505  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. 
     Thereafter, step  1506  is executed to enable the first base station to determine that a signal quality of the channel reservation information of the first unlicensed channel exceeds a threshold. Step  1507  is executed to enable the first base station to transmit schedule information to the mobile station through the first unlicensed channel according to the result of the step  1506 . Finally, step  1508  is executed to enable the mobile station to stop transmitting the channel reservation information according to the schedule information. 
     A sixteenth embodiment of the present invention is a channel access method, referring to  FIG. 16  for a flowchart diagram of the method. The method of the sixteenth embodiment is for use in an LAA network system (e.g., the LAA network system  1  of the aforesaid embodiments) which comprises a mobile station and a first base station. Detailed steps of the sixteenth embodiment are as follows. 
     First, step  1601  is executed to enable the mobile station to determine a use status of an unlicensed band and generate first available unlicensed channel group information. The first available unlicensed channel group information comprises channel reservation information and records a use status of a first unlicensed channel. Step  1602   a  is executed to enable the mobile station to continuously transmit channel reservation information in the first unlicensed channel, and this step is mainly configured to preoccupy the available channel and may enable the base station to perform channel assessment of the first unlicensed channel directly using the channel reservation information. 
     Meanwhile, step  1602   b  is executed to enable the mobile station to transmit the first available unlicensed channel group information to the first base station through a licensed channel. Next, step  1603  is executed to enable the first base station to select the first unlicensed channel to communicate with the mobile station according to the first available unlicensed channel group information. Step  1604  is executed to enable the first base station to initialize a communication schedule assessment procedure with the mobile station via the first unlicensed channel. 
     Thereafter, step  1605  is executed to enable the first base station to determine that a signal quality of the channel reservation information of the first unlicensed channel exceeds a threshold according to the first available unlicensed channel group information. Finally, step  1606  is executed to enable the first base station to transmit schedule information to the mobile station through the first unlicensed channel according to the result of the step  1605 . 
     According to the above descriptions, in the channel access method for use in an LAA network system of the present invention, the unlicensed channel is mainly determined by the mobile station, and the determination result is reported to the base station through the unlicensed channel/the licensed channel so that the base station can more clearly learn the channel use demand of each mobile station to improve the network resource utilization ratio and meanwhile reduce the load of the base station. 
     The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.