Patent Publication Number: US-2010118755-A1

Title: Control apparatus, signal transmission method and computer program product for the control apparatus

Description:
This application claims the benefit of priority based on Taiwan Patent Application No. 097143394, filed on Nov. 10, 2008, the contents of which are incorporated herein by reference in their entirety. 
     CROSS-REFERENCES TO RELATED APPLICATIONS 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control apparatus, a signal transmission method and a computer program product for the control apparatus. More particularly, the present invention relates to a control apparatus capable of directly transmitting an Internet Group Management Protocol (IGMP) report, a signal transmission method and a computer program product for the control apparatus. 
     2. Descriptions of the Related Art 
     With the advancement of science and technology and the development of the IT industry, computers and networks have become indispensable to everyday life. For example, people have been accustomed to processing various data using the Internet on computers to search for information, shop and exchange data. Over recent years, wireless networks, which eliminate the need of physical network wiring and feature high mobility, have been set up. For example, the Worldwide Interoperability for Microwave Access (WiMAX) wireless network, which is currently experiencing the most rapid development, has already been able to support wireless Internet connection under high-speed mobile conditions and further support voice service. 
     In a wireless network, mobile phones or notebook type computers may be viewed as mobile apparatuses or mobile stations. When attempting to access a particular service (i.e., to browse a webpage) from the wireless network, the mobile station sends a request for establishing a wireless connection to the target webpage to the corresponding base station. Because data transmission between the mobile station and the base station does not occur continuously during webpage browsing, the mobile station may enter into an idle mode to save power when data transmission is not going on therebetween. 
     In addition, because the population of network users has rapidly increased, the usage of network bandwidth and addresses has also significantly increased. To solve this problem, wireless network service providers and wireless network equipment manufacturers have proposed the concept of “multicast”, which is intended to reduce the usage of the network bandwidth. For example, when a plurality of users connected to different base stations are attempting to access CTV (China Television Company) program data via the wireless network, the solution of the prior art transmits the CTV program data through unicast to each of the base stations through a one-to-one correspondence, which then forwards the data to each of the users respectively. However, with the multicast method, users who attempt to access the CTV program data via the wireless network will be viewed as a single group, of which members belonging to the same group are all allowed to receive data representing the group network address. Then, the CTV program data may be transmitted to the users through the multicast at the same time. Thus, through multicast, data can be transmitted to a plurality of users at the same time, resulting in a substantial decrease in the usage of the network bandwidth and addresses. 
     To deploy a wireless network provided with both a multicast function and an idle mode, an IGMP framework needs to be incorporated in the wireless network to provide the multicast function.  FIG. 1  illustrates a wireless network  1  incorporating the IGMP framework, which comprises a multicast system  11  and a plurality of mobile stations  13 ,  15 ,  17 ,  19 . The multicast system  11  is configured to store a multicast group list, which lists multicast groups currently existing in the wireless network  1 . For example, if there are two kinds of data that are being transmitted in the wireless network, such as the CTV program data (not shown) and CTS (China Television System) program data (not shown), the two multicast groups will be recorded in the multicast group list. That is, one of the multicast groups is set to an Internet Protocol (IP) address that transmits the CTV program data, while the other is set to another IP address that transmits the CTS program data. 
     According to the multicast group list, the multicast system  11  periodically broadcasts an IGMP query signal  110  incorporating the IP address that transmits the CTV program data and an IGMP query signal  112  incorporating the IP address that transmits the CTS program data. Upon receiving the IGMP query signal  110  and the IGMP query signal  112 , each of the mobile stations  13 ,  15 ,  17 ,  19  determines which multicast group it belongs to according to the IP addresses incorporated in the IGMP query signal  110  and the IGMP query signal  112 . More specifically, if the mobile stations  13 ,  15  only desire to receive the CTV program data, they may join the multicast group corresponding to the CTV program; on the other hand, if the mobile station  17  only desires to receive the CTS program data, it may join the multicast group corresponding to the CTS program. Furthermore, if the mobile station  19  desire to receive both the CTV program data and the CTS program data, it may join both multicast groups corresponding to the CTV and CTS programs. 
     When the mobile stations  13 ,  15 ,  17 ,  19  receive the IGMP query signal  110  and the IGMP query signal  112  respectively, the mobile stations  13 ,  15  return an IGMP report signal  130  and an IGMP report signal  150  respectively in response to the IGMP query signal  110  to inform the multicast system  11  that they still need to receive the CTV program data. The mobile station  17  then returns an IGMP report signal  170  in response to the IGMP query signal  112  to inform the multicast system  11  that it still needs to receive the CTS program data. The mobile station  19  then returns an IGMP report signal  190  and an IGMP report signal  192  in response to the IGMP query signal  110  and the IGMP query signal  120  respectively to inform the multicast system  11  that it still needs to receive both the CTV program data and the CTS program data. In this way, the multicast system  11  of the wireless network  1  is able to accomplish the multicast function successfully. 
     After receiving an IGMP query signal from the multicast system  11 , each of the mobile stations in the wireless network  1  must return an IGMP signal to the multicast system  11 . If the mobile station in the idle mode receives an IGMP query signal, it must exit the idle mode through a large amount of control signals and re-establish the data channel to return an IGMP report signal. If there is no additional data needed after returning the IGMP report signal, the mobile station will enter the idle mode once again through a large amount of control signals and delete the data channel. Therefore, in the case where the multicast system  11  transmits IGMP query signals periodically, the mobile station has to enter and exit the idle mode frequently. Consequently, the transmission of a large amount of control signals required for the mobile station to exit and enter the idle mode causes unnecessary waste of the wireless network bandwidth, and frequently entering/exiting the idle mode also leads to a substantial increase in the power consumption of the mobile station. 
       FIG. 2  illustrates a schematic view of signal transmission between the multicast system  11  and the mobile station  17 . The multicast system  11  comprises a base station  111 , an access network service (ASN) gateway  113 , a paging controller (PC)  115  and an authenticator  117 . When the mobile station  17  is in the idle mode, this means that it is unable to transmit or receive a signal except receiving a multicast signal but. The multicast group list of the multicast system  11  is stored in the ASN gateway  113 . Upon receiving the IGMP query signals  110 ,  112  transmitted by the ASN gateway  113  via the base station  11 , the mobile station  17  must exit the idle mode first and reestablish the data channel to return an IGMP report signal  170  to the ASN gateway  113  in response to the IGMP query signal  112 . 
     Accordingly, the mobile station  17  first transmits a correction request signal  210  to the base station  111  which, in response to the correction request signal  210 , transmits an idle mode exiting request signal  230  to inform the ASN gateway  113  that the mobile station  17  is going to exit the idle mode. Meanwhile, the ASN gateway  113  forwards the idle mode exiting request signal  230  to the paging controller  115 . In response to the idle mode exiting request signal  230 , a context exchange procedure  290  for the mobile station  17  is executed between the paging controller  115  and the authenticator  117 . 
     When the execution of the context exchange procedure  290  between the paging controller  115  and the authenticator  117  is completed, the paging controller  115  transmits an idle mode exiting response signal  270  to the ASN gateway  113  which then forwards the idle mode exiting response signal  270  to the base station  111 . Upon receiving the idle mode exiting response signal  270 , the base station  111  transmits a channel registration request signal  232  to the ASN gateway  113  and then receives a channel registration response signal  250  from the ASN gateway  113  to re-establish a data channel for the mobile station  17 . Once the data channel is established for the mobile station  17 , the base station  111  transmits a correction response signal  234  to the mobile station  17  immediately so that the mobile station  17  will exit the idle mode. Thereafter, the mobile station  17  transmits an IGMP report signal  170  to the ASN  113  via the base station  111 . As a result, after receiving the IGMP query signals  110 ,  112 , the mobile station  17  exits the idle mode and returns the IGMP signal  170  to the ASN gateway  113 . 
     To reduce bandwidth waste in the wireless network and power consumption of the mobile stations, two solutions of the prior art have been proposed. According to one of the solutions, each mobile station in the wireless network  1  has a delay-to-transmit time for transmitting the IGMP report signal to prevent simultaneous transmission of IGMP report signals from all mobile stations in a same group after receiving the IGMP query signals, which would otherwise cause traffic congestion and bandwidth waste in the wireless network. According to the other solution, once a single mobile station transmits an IGMP report signal in broadcast, the other mobile stations belonging to the same group will not need to transmit the respective IGMP report signal, thereby decreasing the number of control signal and the power consumption of the mobile stations that would otherwise increase due to the frequent exiting from idle mode. 
     The following example will be illustrated using mobile stations  13 ,  15 ,  19  that belong to the CTV program group in the wireless network  1 . Assuming that the mobile station  13  has a delay-to-transmit time of  1  second (s), the mobile station  15  has a delay-to-transmit time of 2 s while the mobile station  19  has a delay-to-transmit time of 3 s. After the mobile stations  13 ,  15 ,  19  receive the IGMP query signal  110  respectively, the mobile station  13  which has a delay-to-transmit time of 1 s broadcasts an IGMP report signal  130  first. Once the mobile stations  15 ,  19  receive the IGMP report signal  130 , it will be unnecessary for them to transmit their respective IGMP report signals  150  and  190 , thus reducing the probability for the mobile stations  15 ,  19  to exit the idle mode. However, this practice still fails to reduce the probability for the mobile station  13  to exit the idle mode. 
     In summary, when the multicast system  11  transmits IGMP query signals periodically, the mobile stations still have to enter and exit the idle mode frequently, which causes unnecessary bandwidth waste in the wireless network and substantial increase in power consumption of the mobile stations. Accordingly, it is important to provide, in a wireless network provided with both the multicast function and the idle mode, a solution that may prevent the mobile station from frequently exiting the idle mode to return an IGMP report signal after periodically receiving an IGMP query signal. 
     SUMMARY OF THE INVENTION 
     The objective of this invention is to provide a control apparatus, a signal transmission method and a computer program product for the control apparatus. The control apparatus is used in a wireless network comprising a gateway system and at least one mobile station. The control apparatus is configured to receive a multicast query signal corresponding to a multicast group of the at least one mobile station, and respond to a multicast report signal immediately in a multicast so that after receiving the multicast query signal, the at least one mobile station still remains in the idle mode instead of exiting idle mode to respond with a multicast report signal. 
     To this end, the control apparatus of this invention comprises a storage module, a receiving module and a determination module. The storage module is configured to store a multicast group list. The receiving module is configured to receive an idle mode entry signal, which comprises information of the at least one mobile station previously described. The determination module is configured to determine whether the multicast group list has the information of the at least one mobile station. If the multicast group list does not have the information of the at least one mobile station, the determination module adds the information of the at least one mobile station into the multicast group list. 
     The signal transmission method for the control apparatus of this invention comprises the following steps: receiving an idle mode entry signal, wherein the idle mode entry signal comprises information of the at least one mobile station; determining if the multicast group list has information of the at least one mobile station. If the multicast group list does not have the information of the at least one mobile station, then the information of the at least one mobile station is added into the multicast group list. 
     This invention also provides a computer program product stored in a computer readable medium for the control apparatus to perform the signal transmission method. 
     In summary, the control apparatus of this invention adds information from a multicast group with at least one mobile station into a multicast group list thereof and, after receiving a multicast query signal corresponding to the multicast group of the at least one mobile station, responds with a multicast report signal immediately in a multicast. As a result, after receiving the multicast query signal, the at least one mobile station may still remain in the idle mode instead of responding with a multicast report signal. This is effective to prevent the mobile station from overly frequently exiting/entering the idle mode to return the multicast report signal, which would otherwise cause increased power consumption of the mobile station and bandwidth waste in the wireless network. 
     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. 1  is a schematic view of a wireless network of the prior art that has an IGMP framework; 
         FIG. 2  is a schematic view illustrating signal transmission in the wireless network of the prior art that has an IGMP framework; 
         FIG. 3  is a schematic view of a wireless network according to a first embodiment of this invention; 
         FIG. 4  is a schematic view of a control apparatus according to the first embodiment; and 
         FIG. 5  is a flowchart of a second embodiment of this invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following description, this invention will be explained with reference to embodiments thereof. However, the description of these embodiments is only for purposes of illustration rather than limitations. It should be appreciated that in the following embodiments and the attached drawings, the elements not related directly to this invention are omitted from depiction and dimensional relationships among individual elements in the attached drawings are illustrated only for ease of understanding, and not limitation. 
     A first embodiment of this invention is depicted in  FIG. 3 , which is a schematic view illustrating the signal transmission in a wireless network  3  with an IGMP framework. The wireless network  3  comprises at least one mobile station  31 , a gateway system  33 ,  35  and a control apparatus  37 . In this embodiment, the wireless network  3  is a wireless network conforming to the IEEE. 802.16e standard. The control apparatus  37  is a paging controller conforming to the IEEE. 802.16e standard. The gateway system  33 ,  35  comprises a base station  33  and an ASN gateway  35 . In this embodiment, for purpose of simplicity, only one mobile station  31  is depicted in the wireless network  3 . However, in other embodiments, the wireless network  3  may comprise any number of mobile stations instead of being limited to the single mobile station  31  illustrated in this embodiment. 
     In the wireless network  3 , when the mobile station  31  is going to enter the idle mode, it transmits a correction request signal  310  to the base station  33 . From the correction request signal  310 , the base station  33  is formed that the mobile station  31  is going to enter the idle mode. Subsequently, in response to the correction request signal  310 , the base station  33  generates and transmits an idle mode entry signal  330  to the ASN gateway  35  which further forwards the idle mode entry signal  330  to the control apparatus  37 , so that the control apparatus  37  is informed that the mobile station  31  is going to enter the idle mode. 
     Upon receiving the idle mode entry signal  330 , the control apparatus  37  determines whether it has joined a multicast group corresponding to the mobile station  31  or not. If not, it generates and transmits a joining request signal  370  to the ASN gateway  35  in response to the idle mode entry signal  330 , so that the control apparatus  37  can join the multicast group corresponding to the mobile station  31 . Then, when the ASN gateway  35  multicasts a multicast query signal  350 , the multicast query signal  350  will be received by the mobile station  31  via the base station  33  and also by the control apparatus  37 . 
     While the mobile station  31  is still in the idle mode, the control apparatus  37 , in response to the multicast query signal  350 , broadcasts a multicast report signal  372  immediately without any waiting. The ASN gateway  35 , the base station  33  and the mobile station  31  will all receive the multicast report signal  372 . Upon receiving the multicast report signal  372 , the mobile station  31  cancels the operation of returning a multicast report signal to the ASN gateway  35 s. As a result, the mobile station  31  needs not exit the idle mode to return the multicast query signal  350  while the ASN gateway  35  can still receive the multicast report signal  372 . In the following descriptions, the method in which the control apparatus  37  generates and transmits the multicast report signal  372  corresponding to the mobile station  31  in response to the idle mode entry signal  330  will be described in detail. 
       FIG. 4  is a schematic view of the control apparatus  37 . The control apparatus  37  comprises a storage module  371 , a receiving module  373 , a determination module  375 , a processing module  377  and a transmission module  379 . The storage module  371  is configured to store a multicast group list  374 . The receiving module  373  is configured to receive the idle mode entry signal  330  which incorporates the information of the mobile station  31 , i.e., the multicast group  314  to which the mobile station  31  belongs and the address information  312  of the mobile station  31 . The ASN gateway  35  of the gateway system at least has a multicast group corresponding to the information of the mobile station  31 . The determination module  375  is configured according to both the multicast group list  374  and the information of the mobile station  31  incorporated in the idle mode entry signal  330  to determine (1) if the multicast group list  374  includes the multicast group  314  corresponding to the mobile station  31  and (2) if the multicast group list  374  includes the address information  312  corresponding to the mobile station  31 . 
     If the multicast group list  374  does not include the multicast group  314  corresponding to the mobile station  31  and the address information  312  corresponding to the mobile station  31 , the determination module  375  generates a determination result  376  to the processing module  377  which, in response to the determination result  376 , creates a multicast group  314  in the multicast group list  374 . Then, the determination module  375  adds the address information  312  corresponding to the mobile station  31  into the multicast group  314  in the multicast group list  374 . 
     For example, the multicast group list  374  stored in the storage module  371  may include two multicast groups; namely, a multicast group that receives the TTV (Taiwan Television) program data and a multicast group that receives the CTV program data with the mobile station  31  belonging to the multicast group  314  that receives the CTS program data. Accordingly, the determination module  375  determines that the multicast group list  374  does not include the multicast group  314  corresponding to the CTS program data according to the multicast group list  374  and the information of the mobile station  31 . Then, the processing module  377  creates the multicast group  314  corresponding to CTS in the multicast group list  374 , while the determination module  375  adds the address information  312  of the mobile station  31  into the multicast group  314  corresponding to CTS in the multicast group list  374 . 
     After the address information  312  of the mobile station  31  is added into the multicast group in the storage module  371  and in response to the idle mode entry signal  330 , the processing module  377  enables the transmission module  379  to transmit the joining request signal  370  to the ASN gateway  35  to join the multicast group corresponding to the information of the mobile station  31 . For example, if the address information  312  of the mobile station  31  is added into the multicast group  314  corresponding to the CTS program in the multicast group list  374 , the control apparatus  37  will be added into this multicast group  314  corresponding to the CTS program. 
     If the determination module  375  determines that the multicast group list  374  already includes the multicast group  314  corresponding to the mobile station  31  but the multicast group  314  has not included the address information  312  corresponding to the mobile station  31  yet, the determination module  375  adds the address information  312  corresponding to the mobile station  31  into the multicast group  314  in the multicast group list  374  directly. 
     More specifically, the multicast group list  374  stored in the storage module  371  already includes two multicast groups; namely, a multicast group that receives the TTV program data and a multicast group that receives the CTS program data. Because the mobile station  31  belongs to the multicast group  314  that receives the CTS program data, the determination module  375  determines that the multicast group list  374  already includes the multicast group  314  corresponding to the CTS program data in which the mobile station  31  can join according to the multicast group list  374  and the information of the mobile station  31 . Accordingly, the determination module  375  adds the address information  312  of the mobile station  31  into the multicast group  314  corresponding to the CTS in the multicast group list  374  directly. 
     After the above operations are completed, if the receiving module  373  of the control apparatus  37  receives a multicast query signal  350 , the processing module  377  enables the transmission module  379  to broadcast a multicast report signal  372  to the mobile station  31 , the ASN gateway  35  and the base station  33  immediately in response to the multicast query signal  350 . Upon receiving the multicast report signal  372 , the mobile station  31  ceases the procedure of transmitting a multicast report signal immediately to prevent the exiting from the idle mode. 
     In other words, because the control apparatus  37  can transmit a multicast report signal instead of the mobile station  31 , a mobile station in the idle mode needs not exit the idle mode to return the multicast report signal when it receives a multicast query signal. In this Way, this invention is effective in preventing the mobile station from overly frequently exiting/entering the idle mode to transmit the multicast report signal, which would otherwise cause an increased power consumption of the mobile station and bandwidth waste in the wireless network. 
       FIG. 5  depicts a second embodiment of this invention, which is a signal transmission method. The signal transmission method is adapted for a control apparatus, e.g., the control apparatus  37  described in the first embodiment. The control apparatus  37  is for use in a wireless network comprising a gateway system and at least one mobile station. The control apparatus is configured to store a multicast group list. More specifically, the signal transmission method described in the second embodiment may be executed by a computer program product. When the computer program product is loaded into the control apparatus  37  via a computer and a plurality of program instructions embodied thereon is executed, the signal transmission method of the second embodiment can be accomplished. This computer program product may be stored in a tangible machine-readable medium, such as an ROM, a flash memory, a floppy disk, a hard disk, a compact disk, a mobile disk, a magnetic tape, a database accessible to networks, or any other storage media with the same function and well known to those skilled in the art. 
     The signal transmission method of the second embodiment comprises the following steps. Initially, in Step  41 , an idle mode entry signal is received. The idle mode entry signal comprises information of the at least one mobile station, which in turn comprises a multicast group to which the at least one mobile station belongs and the address information. Then, in Step  42 , it is determined whether the multicast group list has the multicast group to which the at least one mobile station belongs. If not, a multicast group is built in the multicast group list in Step  43 . Next, in Step  44 , the address information of the at least one mobile station is added into the multicast group created in Step  43 . Subsequently, a joining request signal is transmitted to the gateway system in Step  45  to join the multicast group corresponding to the information of the at least one mobile station. 
     If it is determined in Step  42  that the multicast group list has already included the multicast group to which the at least one mobile station belongs, the process proceeds directly to Step  46  where the address information of the at least one mobile station is added into the multicast group list which the at least one mobile station belongs to the multicast group. 
     Subsequent to the above steps, a multicast query signal is received in Step  47 . Finally in Step  48 , the control apparatus transmits a multicast report signal to the gateway system in response to the multicast query signal if the multicast groups to be queried belong to the multicast group list. 
     In summary, the control apparatus of this invention can transmit a multicast report signal instead of the mobile station. Therefore, the mobile station in the idle mode needs not exit the idle mode to return a multicast report signal when it receives a multicast query signal. In this way, this invention is effective in preventing the mobile station from overly frequently exiting/entering the idle mode to transmit the multicast report signal, which would otherwise cause increased power consumption of the mobile station and bandwidth waste in the wireless network. 
     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.