Abstract:
A method for improving transmission efficiency of wireless local area network (WLAN) comprises a WLAN neighbors establishing procedure and a high efficiency transmission mode establishing procedure. The WLAN neighbors establishing procedure establishes neighbors between stations of the WLAN. The high efficiency transmission mode establishing procedure causes the stations to disassociate with the access point in a power save mode and switch from an infrastructure mode to an ad-hoc mode for transmitting data. The present invention also discloses a corresponding system of improving transmission efficiency of WLAN.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a method and system for wireless local area network (WLAN) transmission and, more particularly, to a method and system for improving transmission efficiency of WLAN.  
           [0003]    2. Description of the Related Art  
           [0004]    In a typical wireless network environment, a communication device, such as a computer, needs only to be equipped with an antenna or a wireless network card for connecting to the Internet through a wireless access point (AP). Because of high scalability and easy administration, the WLAN costs little for increasing a number of APs for wireless communication without implementing and expanding cables. Therefore, the operating cost for the WLAN significantly lowers, especially in system installation and maintenance. Besides, the WLAN has more advantages than a wired network in both convenience of network installation and mobility of its use. Therefore, the WLAN technology is most suitable for places where are hard-to-wire and require no physical infrastructure of LAN, such as an exhibition field with temporary network installation, a historical building worth preserving, or an office or a house with decoration, etc.  
           [0005]    The current WLAN standard, such as IEEE 802.11, specifies two ways of configuring transmission structure: an ad-hoc mode as shown in FIG. 1 a , and an infrastructure mode as shown in FIG. 1 b . In the ad-hoc mode, a station (STA) communicates with other STAs using a wireless network card and forms a network. In this mode, however, the STAs are limited to communicate within the LAN and cannot be connected to the Internet. In order to connect to the Internet  107 , it is necessary to use the infrastructure mode. In this mode, the STAs  101 ,  102 , and  103  form a network with each other and are connected to a wired network  106  such as an Ethernet through an access point  104  (AP), and further connected to the Internet  107  through a gateway  105  on the wired network  106 . The AP  104  therefore functions as a bridge between the STAs and the main network. However, transmission efficiency in the infrastructure mode is reduced since the STAs  101 ,  102 , and  103  need the AP  104  as a bridge for connecting to the Internet  107  and communications between the STAs  101 ,  102 , and  103  are also transmitted through the AP  104 .  
           [0006]    In the ad-hoc mode, for example, the STA  101  transmits data directly to STA  102  (as shown in FIG. 1 a ). In the infrastructure mode, however, the STA  101  must transmit data to the AP  104  at first, and then from the AP  104  to the STA  102  (as shown in FIG. 1 b ). Therefore, for transmitting the same amount of data between the STAs, the infrastructure mode takes twice of the transmission time in the ad-hoc mode, causing the reduction of the transmission efficiency.  
           [0007]    Moreover, in the infrastructure mode, each station must wait for polling from the AP or compete for transmission priority in order to transmit data. Consequently, the STAs are in a waiting status most of the time. This is unfavorable for certain applications for the Internet services, such as real-time digital videos. To ensure an effective transmission of a real-time video, the best way is to transmit data in the ad-hoc mode. However, once the transmission mode is selected as the ad-hoc mode, the user must change the setting manually and the AP does not reserve the data transmitted from the Internet to the STAs since the STAs are disassociated with the AP. Also, the STAs cannot use services provided by the AP and lose the connection with the Internet. To sum up, the major challenge faced today is to keep the STAs connected with the Internet and achieve improved transmission efficiency among the STAs, thereby ensuring the transmission quality of real-time videos.  
         SUMMARY OF THE INVENTION  
         [0008]    In view of the above-mentioned problems, an object of this invention is to provide a method and system for improving transmission efficiency of WLAN, which allows stations of a WLAN to keep in connection with the Internet and to improve transmission efficiency between stations as well.  
           [0009]    Another object of this invention is to provide a method and system for improving transmission efficiency of WLAN, so that stations can automatically switch from an infrastructure mode to an ad-hoc mode for improving transmission efficiency and connecting to the Internet without manually setting a transmission mode.  
           [0010]    In order to achieve the above objects, the method and system for improving transmission efficiency of WLAN according to the invention include a first station and at least a second station. The first station can establish neighbors with the second station of a WLAN and transmit data directly in an ad-hoc mode. The WLAN neighbors establishing procedure includes broadcast a request of establishing neighbors from the first station, the request including a related information of the first station. After receiving the request, the second station sends back a reply of establishing neighbors including a related information of the second station. After receiving the reply of establishing neighbors, the first station retrieves the related information of the second station for recognizing currently active neighbors on the WLAN.  
           [0011]    In addition, an access point is used for establishing an infrastructure mode to transmit data between the stations and for providing connections to the Internet. When the first station needs to establish a connection with the second station in a high efficiency transmission mode, a request is sent to the second station for establishing a connection in the high efficiency transmission mode. After receiving a reply from the second station corresponding to the received request of establishing a high efficiency transmission mode, the first station scans for an available frequency f within a predetermined eligible frequency domain to avoid frequencies currently used by the AP and to generate a service set identifier d. The first station then notifies the AP for switching to a power save mode and also switching to an ad-hoc mode in order to establish connection with the second station in a high efficiency transmission mode by using the frequency f and the service set identifier d. The second station also notifies the AP for switching to a power save mode and switching to an ad-hoc mode in order to establish connection with the first station in a high efficiency transmission mode by using the frequency f and the service set identifier d. Once the connection is established, data can be transmitted between the stations. When the transmission is completed, both of the first and second stations send a request to the AP for association and switch back to the original transmission mode.  
           [0012]    According to the present invention, when the first station is connected to the second station in the high efficiency transmission mode, data is transmitted in the ad-hoc mode. As a result, the waiting time caused by polling from the AP or competing for transmission priority is prevented. Meanwhile, the frequency used in the high efficiency transmission mode is different from those used by the AP, thereby avoiding interference, effectively improving transmission efficiency, and increasing available bandwidth. Moreover, after the first and second stations are disassociated with the AP in the power save mode, the AP reserves the data transmitted to the first and second stations. When associated with the AP again, the first and second stations can retrieve from the AP those temporarily stored data including data from the Internet. Hence, the first and second stations can still keep the connection with the Internet and miss no information transmitted from the Internet. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The above-mentioned and other objects, features, and advantages of the present invention will become apparent with reference to the following descriptions and accompanying drawings, wherein:  
         [0014]    [0014]FIG. 1 a  is a schematic diagram showing a conventional WLAN in an ad-hoc mode;  
         [0015]    [0015]FIG. 1 b  is a schematic diagram showing a conventional WLAN in an infrastructure mode;  
         [0016]    [0016]FIG. 2 is a schematic diagram showing a system for improving transmission efficiency of WLAN in an embodiment of the invention;  
         [0017]    [0017]FIG. 3 is a flow diagram showing steps implemented by a first station in the method for establishing WLAN neighbors in an embodiment of the invention.  
         [0018]    [0018]FIG. 4 is a flow diagram showing steps implemented by a second station in the method for establishing WLAN neighbors in an embodiment of the invention;  
         [0019]    [0019]FIG. 5 is a flow diagram showing steps implemented by a first station in the method for establishing connections in high efficiency transmission mode in an embodiment of the invention; and  
         [0020]    [0020]FIG. 6 is a flow diagram showing steps implemented by a second station in the method for establishing connections in high efficiency transmission mode in an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    A method and system for improving transmission efficiency of WLAN according to embodiments of the invention will be described with reference to the accompanying drawings. In the accompanying drawings, similar elements will be denoted with similar reference symbols.  
         [0022]    Referring to FIG. 2, a system for improving transmission efficiency of WLAN includes a first station  201  and at least a second station  202 ,  203 . The first station  201  communicates with the second stations  202 ,  203  based on a conventional transmission standard for WLAN, such as the IEEE 802.11b standard, thereby forming a WLAN in the ad-hoc mode.  
         [0023]    In addition, the system further includes an AP  205 . The AP  205  communicates with the stations  201 ,  202 ,  203  based on the same communication standard of WLAN (IEEE 802.11b), thereby forming a WLAN in the infrastructure mode. In the infrastructure mode, all of the data transmitted between the stations must go through the AP  205  first. Besides, the AP  205  may be connected to a wired network  106 , such as an Ethernet. Therefore, through the AP  205 , the stations  210 ,  202 ,  203  located within the communication range of the AP  205  can get access to data on the wired network  106 . For instance, the server  206  shown in FIG. 2 can be a network server such as a file server, a mail server, or a web server. Through the AP  205 , each of the stations  201 ,  202 ,  203  can also be connected to the Internet  107  via the gateway  105  of the wired network  106 .  
         [0024]    The following description illustrates a method for improving transmission efficiency of WLAN, which is applied to the above-mentioned system. The method includes a procedure for establishing WLAN neighbors and a procedure for establishing a high efficiency transmission mode. The procedure for establishing WLAN neighbors is described in detail with reference to FIGS. 3 and 4. First, as shown in FIG. 3, the first station  201  packs its own related information such as a medium access control address (MAC address), an internet protocol address (IP address) and a hostname as a transmission packet of a lower level communication protocol, such as a medium access control packet (MAC packet), or as a transmission packet of a higher level communication protocol, such as an internet protocol packet (IP packet). Next, the first station  201  broadcasts a request of establishing WLAN neighbors (S 301 ) in compliance with the IEEE 802.11b standard. Thereafter, the first station  201  sets a timer  302  for counting a time of waiting for a reply of establishing neighbors  406  corresponding to the request of establishing neighbors  301 . If the counted time of waiting for a reply exceeds a predetermined waiting time limit, the operation of establishing WLAN neighbors is terminated.  
         [0025]    Because operations executed by the second station  202  and second station  203  are the same, only the second station  202  is described for illustration. Referring to FIG. 4, when the second station  202  receives a network packet  401  (S 401 ), the second station  202  determines whether the network packet  401  is a request of establishing neighbors  301  (S 402 ). If the network packet  401  is not a request of establishing neighbors  301 , the network packet  401  is processed according to the IEEE 802.11b standard (S 403 ). If the network packet  401  is a request of establishing neighbors  301 , the related information of the first station  201 , i.e. the MAC address, the IP address, and the hostname, is retrieved from the request of establishing neighbors  301  (S 404 ). Subsequently, the second station  202  retrieves its own related information, i.e. the MAC address, the IP address, and the hostname (S 405 ), and sends back a reply of establishing neighbors  406  corresponding to the request of establishing neighbors  301  (S 406 ). The reply of establishing neighbors  406  includes the related information of the first station  201  and the related information of the second station  202 .  
         [0026]    Referring back to FIG. 3, during the waiting for a reply of establishing neighbors  406  (S 303 ), the first station  201  receives and determines whether a reply of establishing neighbors  406  is new. If the reply of establishing neighbors  406  is not new, the first station keeps waiting until the predetermined waiting time limit is exceeded (S 303 ). If the reply of establishing neighbors  406  is new, the first station  201  then retrieves the related information of the second station  202 , i.e. the MAC address, the IP address, and the hostname, from the reply of establishing neighbors  406  (S 305 ). Finally, the first station  201  and the second station  202  are established as WLAN neighbors as requested (S 306 ).  
         [0027]    Referring to FIGS. 5 and 6, a procedure for establishing a high efficiency transmission mode is described. As shown in FIG. 5, the first station  201  selects at least a second station  202 ,  203  from the list of WLAN neighbors for receiving data (S 501 ). Because operations executed by the second station  202  and second station  203  are the same, only the second station  202  is described as an example. Next, the first station  201  sends a request of establishing a high efficiency transmission mode  502  to the second station  202  (S 502 ) and then waits for a corresponding reply (S 503 ). If a time of waiting for the reply exceeds the predetermined waiting time limit, the operation for establishing a high efficiency transmission mode is terminated.  
         [0028]    Referring to FIG. 6, after receiving the request of establishing a high efficiency transmission mode  502  (S 601 ), the second station  202  may request for an authentication information  602  from the first station  201  in order to determine whether to accept the request of establishing a high efficiency transmission mode (S 602 ). Examples of the authentication information  602  are a password or a key value for verifying identification and permission. If the authentication information  602  of the first station  201  is required, the second station  202  sends a request of an authentication information  603  to the first station  201  (S 603 ) and then waits for a corresponding reply (S 604 ). If a time of waiting for the reply exceeds the predetermined waiting time limit, the operation for establishing a high efficiency transmission mode is terminated. While the first station  201  is waiting for the reply of establishing a high efficiency transmission mode (S 503 ), because the reply received is a request of an authentication information  603  (S 504 ), as shown in FIG. 5, the step S 505  is performed for sending back a reply of requesting an authentication information  505 , including the authentication information  602  for passing the authentication of the second station  202 . After receiving the authentication information  602 , the second station  202  determines whether the authentication information  602  is correct (S 605 ). If the authentication information  602  is incorrect, then the step S 603  repeats to send a request of an authentication information  603  in order to request the first station  201  for the authentication information  602  again. The first station  201  executes the step S 505  again to send back a reply of requesting an authentication information  505 . If the authentication information  602  is correct, then the second station  202  sends back a reply of establishing a high efficiency transmission mode  606  for agreeing the establishment of the high efficiency transmission mode (S 606 ).  
         [0029]    After receiving the reply of establishing a high efficiency transmission mode  606 , the first station  201  scans for an available frequency f within a predetermined eligible frequency domain to avoid transmission collision and interference. The IEEE 802.11b specifies at least three frequency domains separated at least 20 MHz. Take the standard for North America as an example, the central frequencies of the three frequency domains might be 2412 MHz, 2437 MHz, and 2462 MHz respectively. The first station  201  scans through the three frequency domains, avoiding frequencies currently used by the AP  205  or frequencies having severe interference. This is to avoid transmission collisions or interference. Besides, the first station  201  randomly generates a service set identifier (SSID) d for verification when communicating with the second station  202 . The first station  201  notifies the second station  202  about the frequency f and the service set identifier d (S 506 ). Thereafter, the first station  201  reports to the AP  205  that the first station  201  is switched to a power save mode and the transmission mode is switched to the ad-hoc mode, using the frequency f and service set identifier d to establish connections with the second station  202  in the high efficiency transmission mode (S 507 ).  
         [0030]    Note that in such a simple environment of WLAN that the first station  201  and the second station  202  can trust each other, the authentication step can be omitted. For example, when the second station  202  receives a request of establishing a high efficiency transmission mode  502 , the step S 606  is performed to send back a reply of establishing a high efficiency transmission mode  606 . After the first station  201  receives the reply of establishing a high efficiency transmission mode  606 , the step S 506  is performed to scan for available a frequency f and to generate a service set identifier d, and to notify the second station  202 .  
         [0031]    After receiving the frequency f and the service set identifier d, the second station  202  retrieves the information (S 607 ). Thereafter, the second station  202  reports to the AP  205  that the second station  202  is switched to a power save mode and the transmission mode is switched to the ad-hoc mode, using the frequency f and the service set identifier d to wait for directly establishing a high efficiency transmission mode with the first station  201  to transmit information (S 608 ).  
         [0032]    While the first station  201  is trying to establish connections, a timer can be set for counting a time of waiting (S 508 ). If the establishment of connections fails, the operation of establishing a high efficiency transmission mode is terminated. If the connections are successfully established, the information is packed as a MAC packet and transmitted to the second station  202  in the ad-hoc mode (S 509 ). Correspondingly, after the high efficiency transmission mode is successfully established, the second station  202  waits to receive and process the information of the MAC packet (S 609 ). When the data transmission is completed, each of the first station  201  and the second station  202  files an application of association to the AP  205 . The transmission mode is then switched back to the infrastructure mode, using the original frequency domain to transmit data (S 510  and S 610 ). Since the stations are disassociated with the AP  205  in the power save mode during the establishment of the connections in the high efficiency transmission mode, the AP  205  reserves those data to be transmitted to the stations in the power save mode. After each of the first station  201  and the second station  202  returns to association, the data stored temporarily on the AP  205  is retrieved.  
         [0033]    Note that after the first station sends a request of establishing a high efficiency transmission mode to the second station, the first station must receive a reply from the second station. Thus, in order to establish a high efficiency transmission mode, the communication range is a coverage area where the first station can hear information replied by all of the second stations. For example, as shown in FIG. 2, assume that within a communication range  201 R of the first station  201 , the station  204  can hear, i.e. receive, a request of establishing a high efficiency transmission mode  502  from the first station  201 . However, if the station  204  is located in an environment having too much interference, then an effective communication range  204 R of the station  204  may be so small that the reply of establishing a high efficiency transmission mode  606  sent by the station  204  cannot be heard by the first station  201 . Consequently, the first station  201  cannot establish connections with the station  204  in the high efficiency transmission mode even though both of the first station  201  and the station  204  are located within a communication range  205 R of the common AP  205 .  
         [0034]    In addition, the security setting for data transmission in the high efficiency transmission mode complies with the setting of the original WLAN communication standard. For instance, a Wired Equivalent Privacy (WEP) method is utilized to encrypt transmission data. Because the stations belong to the domain of the same AP, the key used by the WEP method is the same and the verification is not necessary.  
         [0035]    According to the invention, the stations in a WLAN can transmit data in the ad-hoc mode in cooperation with the video streaming technology, thereby ensuring the quality of the video. Even if the data is transmitted between the stations in the infrastructure mode, when a larger bandwidth is required, the transmission mode can be automatically switched to the ad-hoc mode in order to establish a high efficiency transmission mode for transmitting data, thereby increasing the available bandwidth. Moreover, since the frequency used to transmit data between the stations is different to the one used by the AP, a possible interference is avoided. Besides, the data transmitted for those stations in the high efficiency transmission mode is temporarily stored in the AP since the stations are disassociated with the AP in the power save mode. These data include not only those transmitted in the WLAN but also those transmitted from the Internet. Therefore, when restoring to in association with the AP, the station can retrieve those data from the AP without losing the connection with the Internet.  
         [0036]    While the invention has been described by way of examples and in terms of preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications. For example, the IEEE 802.11b standard for WLAN is used for the description of the embodiment of the invention. Those skilled in the art may make alternations and modifications using IEEE 802.11a or other standards relating to IEEE 802.11×standard for WLAN. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications.