Patent Publication Number: US-2004042424-A1

Title: Switch method and device thru MAC protocol for wireless network

Description:
[0001] The present invention is related to a switch method and device thru Media Access Control (MAC) Protocol for wireless network, and in particular to a switch device under the structure of infrastructure wireless local network, and let all mobile work stations inside of network can get the regulation and control thru said device, and transmitting data in different channels, and increasing the utilization of network bandwidth.  
       BACKGROUND OF THE INVENTION  
       [0002] The IEEE project 802 has formed a study group 802.11 to set up international wireless LAN standard. In an aspect of the operation mode of wireless local network are general separating two parts of Infrastructure Wireless Local Area Network (IWLAN) and Ad-Hoc Wireless Local Area Network (Ad-Hoc WLAN). The providing method and device of the present invention is just fit for said Infrastructure Wireless Local Area Network.  
       [0003] In the Infrastructure Wireless Local Area Network (IWLAN) as we know at present, the data transmission between mobile wireless work stations with internet, or with another wireless work stations in network is utilizing a access point AP which is by single channel mode operation mode to provide the function of transformation; In other word, all mobile wireless work stations are proceeding the job of hand-shaking, data exchanging and transformation by the firm common channel which is assigned by said access point (AP).  
       [0004] As shown in FIG. 1, the known method for data transmission of said Infrastructure Wireless Local Area Network (IWLAN) comprising the following steps:  
       [0005] STEP 1: At first, the Sender Work Station (STA-A) sends a control frame of Request-To-Send (RTS) to the Access Point (AP) to compete the channel using right;  
       [0006] STEP 2: As the access point (AP) receives the control frame of RTS correctly, than the access point responses a control frame of Clear To Send (CTS) to the Sender Work Station (STA-A) immediately, furthermore, asking the Sender Work Station (STA-A) send back a data frame to the access point (AP).  
       [0007] STEP 3: As the access point (AP) receives said data frame correctly, the access point (AP) responses a Acknowledgement (ACK) to the Sender Work Station (STA-A), to inform the correction of data transmission and to end the procedure of transmission; and  
       [0008] STEP 4: As the destination is a wired network ( 10 ), thus, the access point AP transforms the data to a wired network interface; On the contrary, the access point AP transforms the data from the Sender Work Station(STA-A) to inside of wireless work station(STA-B).  
       [0009] The Data-Link layer of local area network (LAN) is composed of Media Access Control (MAC) and Logical-Link Control (LLC) two parts. Wherein the Media Access Control (MAC) is the central part of the communication protocol of local area network, and it is charged by network interface card, and the logical-link control (LLC) is charged by LAN Driver.  
       [0010] According to IEEE 802.11, the transmission mode of Open System Interconnection (OSI) wherein the Physical Layer are general separating two parts of IEEE 802.11b and 802.11a; and the data rate of IEEE 802.11b is including 1, 2, 5.5 and 11 Mbps; and the bandwidth range of utilizing is from 2.4 GHz to 2.4835 GHz; furthermore, its bandwidth are separating 14 parts overlap communication channels, and causing it might be interfering among these channels, so, it could at most have three exclusive channels to be used simultaneously to avoid the problem of interference.  
       [0011] On the contrary, the data rate of IEEE 802.11a also include: the range of 6. 12. 18. 24. 36. 48 and 54 Mbps, and the using bandwidth include from 5.15 GHz to 5.35 GHz and 5.725 GHz to 5.825 GHz, wherein the using channels are more than 12 channels that we can use. But, under the specifications of prior art IEEE 802.11 wireless local area network, the infrastructure wireless local area network and Ad Hoc wireless local area network are all only can choose one firm unchanged channel for the purpose of data transmission, and others are idle, so, it causing the waste of wireless network channels, and this is a long-term exist defect.  
       [0012] This kind of bandwidth waste is always happened in the wireless network of middle or the small enterprises, but like this kind network applications are occupied very high proportions in the market of wireless local area network. Therefore, the object of the present invention is under the structure of unchanged prior art IEEE 802.11 wireless LAN specification, and at first, providing the method of communication protocol which we can double bandwidth of wireless channel among all wireless network work stations, saving data transmission time and producing more parallel transmission throughput.  
       SUMMARY OF THE INVENTION  
       [0013] The present invention is related to a switch method and device thru media access control (MAC) protocol for wireless network, including a wired network interface, a wireless network interface, a memory element and a operation unit, it is utilizing the wired network interface to exchange signal with a wired network, and in the mean time, utilizing the wireless network interface to exchange signal with outside another wireless network work stations by way of wireless communication, by this way, let the switch device becomes a access point (AP) between a wired network and a wireless network work station; the specialty is said memory element sets a Using Channel Situation Table and a Multi-channel Transmission Mode Situation Table, by this way to record transmission situation among all wireless network work stations and all using channel and channel released time, also providing related control packets of work stations to make a common channel switch to a assigned data channel to proceed data parallel transmission in setting time, by this device and channel switch method, we can carry out two kinds of wireless switch of communication protocol operations:  
       [0014] First Kind: it is a two sides hand-shaking protocol which is fit for between wireless network work stations and is proceeding under the circumstances of non-barrier and non-interference; and  
       [0015] Second Kind: it is a three sides hand-shaking protocol which is fit for over distance among those wireless network work stations (STAs) or is proceeding under the circumstances of barrier and interference.  
       [0016] For moving forward to illustrate the carry out methods, including the related objects, significances and benefits of the present invention, please refer to add on drawings and description as below. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017]FIG. 1 is a schematic diagram related prior art;  
     [0018]FIG. 2 is a switch device structure schematic diagram according to the present invention;  
     [0019]FIG. 3 is a two sides hand-shaking multi-channel transmission mode schematic diagram according to the present invention;  
     [0020]FIG. 4 is a three sides hand-shaking multi-channel transmission mode schematic diagram according to the present invention;  
     [0021]FIG. 5 is a two sides hand-shaking control frame transmission timing schematic diagram under non-barrier environment according to the present invention;  
     [0022]FIG. 6 is a three sides hand-shaking control frame transmission timing schematic diagram under barrier environment according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0023] Please refer to FIG. 2, the switch device  20  of media access control protocol of the present invention may be constructed by a computer or a single chip, as long as wherein is including a wired network interface device  21 , a wireless network interface device  22 , a memory device and a operation device. For the purpose is proceeding signal exchange with wired network  10  by said wired network interface device  21 , and in the mean time, using said wireless network interface device  22  exchanges signal with out side another wireless network work station by way of wireless communication, by this way, let the switch device  20  becomes a Access Point (AP) between a wired network and wireless network work stations.  
     [0024] The specialty of the present invention is setting a Using Channel Situation Table  2301  and a Multi-channel Transmission Mode Situation Table  2302  in said memory device  23 , by this way to record the transmission situation of all wireless network work stations and all using channel and channel release time, further more, providing the control packets to related work stations, then let proceeding data parallel transmission from a common channel switch to a assigned data channel in setting time.  
     [0025] First Embodiment:  
     [0026] As describe above, the device and method according to the present invention may be implemented under the conditions of non-barrier and non-interference among all wireless network work stations, and to proceed communication which is base on a two sides hand-shaking wireless switch MAC protocol of IEEE 802.11 Infrastructure Wireless Area Network (IWLAN). Please refer to FIG. 3 and FIG. 5, wherein the transmission steps of control frame are comprising:  
     [0027] Step a: utilizing a switch device  20  to construct a Intelligent Access Point (AP) among all wireless work stations;  
     [0028] Step b: setting an Using Channel Situation Table  2301  in a memory device  23  of said switch device  20  to record the idle time of all channels;  
     [0029] Step c: transmitting a Multi-channel Request-To-Send (M-RTS) control frame from the Sender Work Station (STA-A) to said switch device  20 ;  
     [0030] Step d: inquiring the idle time of all channels in the Using Channel Situation Table  2301  by an operation device  24  of the switch device  20 , and find out the earliest idle channel, after the switch device  20  has listened said M-RTS;  
     [0031] Step e: transmitting a Multi-channel Clear-To-Send (M-CTS) control frame from a wireless network interface device  22  of the switch device  20  to all work stations, and said M-CTS control frame, including an idle channel which is assigned by AP and a record of starting time; and  
     [0032] Step f: switching the data transmission channel to an assigned data channel to proceed a data parallel transmission in a setting time, as the Sender Work Station (STA-A) and the receiver work station (STA-B) received said M-CTS.  
     [0033] Preferably, in accordance with the present invention, let said switch device  20  became an Intelligent Access Point AP, and set a firm common channel for all wireless work stations to proceed competing and then to get the right of transmission; If the destination of data transmission is a work station in wireless network, then, the data transmission will use another data channel to release the resource of common channel. In the mean time, said common channel can provide another wireless work stations for the purpose of transmitting data to wired network  10 .  
     [0034] Further, preferably in accordance with the present invention, the Using Channel Situation Table  2301  is built-in said Intelligent Access Point(AP), and used to record the situations of channel using and channel release time among all work stations. Therefore the best channel and the suitable channel using time could be count out through inquiring table for every time we proceeding the choice of channel and time point.  
     [0035] Furthermore, preferably in accordance with the present invention, through the switch device  20  of wireless switching media access control (MAC), we can transmit and receive the data directly among wireless work stations, by this way we can avoid extra channel competition and collision, and saving the network channel resource.  
     [0036] Second Embodiment:  
     [0037] Under the circumstances of having barrier and interference, the present invention implements a three sides hand-shaking wireless switch MAC protocol. Please refer to FIG. 4 and FIG. 6, wherein the transmission steps of control frame may comprising:  
     [0038] Step a: constructing an Intelligent Access Point (AP) among all wireless work stations by using the switch device  20  of the present invention;  
     [0039] Step b: using the memory device  23  in said switch device  20  to construct a Multi-channel Transmission Mode Situation Table  2302  and a Using Channel Situation Table  2301  between any two wireless work station for recording the idle time of all channels;  
     [0040] Step c: transmitting a type  1  control frame of Multi-channel Request-To-Send (M-RTS 1 ) from said Sender Work Station (STA-A) to switch device  20  first; if the transmission quality has been recorded in the switch device&#39;s situation table between Sender Work Station (STA-A) and receiver work station (STA-B) is allowing to transmit directly, then transmitting a type  2  control frame of Multi-channel Request-To-Send (M-RTS 2 ) from said access point AP to Sender Work Station (STA-A) and receiver work station (STA-B); On the contrary, if the Multi-channel Transmission Situation Table  2302  of said switch device  20  records that it can not transmit by multi-channel, then sending back the standard CTS control frame to Sender Work Station (STA-A) immediately as soon as it receives the M-RTS 1  control frame, then sending the data to said switch device  20  directly, and go back the original transmission mode of IEEE;  
     [0041] Step d: when said receiver work station (STA-B) receives the type  2  Multi-channel Request-To-Send (M-RTS 2 ) control frame from said switch device  20 , then transmits a Multi-channel Clear-To-Send (M-CTS) control frame to said Sender Work Station (STA-A) to confirm, in the mean time, the switch device  20  also has listened said M-CTS control frame, and according to this to correct the Using Channel Situation Table  2301 ; but if said receiver work station (STA-B) only receives the type  2  Multi-channel Request-To-Send (M-RTS 2 ) control frame from said switch device  20 , and loss the M RTS 1  which is from said Sender Work Station (STA-A), and then send back the CTS to switch device  20  to inform the situation of hidden-node, and to record that situations to Multi-channel Transmission Mode Situation Table  2302 ; After, the access point AP which is constructed by switch device  20  send back CTS control frame to said Sender Work Station (STA-A) and request send the transmission data to access point AP directly, just as the original mode of IEEE;  
     [0042] Step e: when said Sender Work Station (STA-A) receives the M-CTS, it means that hand-shaking is working with said receiver work station (STA-B), and it will switch to another assigned data channel to transmit data in setting time.  
     [0043] Preferably, in accordance with the present invention, setting a all work station common channel in access point AP which is constructing by switch device  20 , and it is for the purpose of competing transmission right among wireless work stations in wireless network, then switch to another assigned data channel proceeding wireless data transmission in setting time, or it can take a firm single channel to be a control center of data transmission when it can not transmit between sender and receiver directly.  
     [0044] Further, preferably in accordance with the present invention, wherein if there are some barriers among all work stations, the M-RTS 1  is transmits from said Sender Work Station (STA-A) to switch device  20 , and comparing to the transmission mode table in memory device  23  by said operation device  24 , by this way, to decide whether it can be operated by multi-channel mode or not; if it can operate by multi-channel mode, then, in the same time, it send out the M-RTS 2  to all work stations by wireless network interface; otherwise, it send out the control frame of CTS which is setting originally by IEEE to said Sender Work Station (STA-A), and let it recover to traditional data transmission mode.  
     [0045] Furthermore, preferably in accordance with the present invention, wherein if there is a barrier exists between those two work stations, then let the receiver work station (STA-B) send out a standard control frame of CTS to switch device  20 , furthermore, sending back to the Sender Work Station (STA-A), at this moment, the Sender Work Station (STA-A) must back to the operation of single channel mode, and the data will transform to the receiver work station (STA-B) through the access point AP of switch device  20 .  
     [0046] Of course, if there are some conditions of un-transmitting directly has happened between those two work stations, we can also update the built-in transmission mode table of said Intelligent Access Point AP periodically, furthermore, retry the operation of multi-channel mode to upgrade the efficiency of network. Therefore, the method and device of the present invention is suitable for two sides hand-shaking wireless switch MAC communication mode of infrastructure wireless network of IEEE 802.11 (under the environments of non-barrier and non-interference), or the present invention is suitable for three sides hand-shaking wireless switch MAC communication mode of infrastructure wireless network of IEEE 802.11 (under the environments of barrier and interference).  
     [0047] Please refer to FIG. 4 and FIG. 5 at the same time, through these two drawings we can understand the method of wireless network inside multi-channel. transmission MAC protocol under the conditions of non-barrier, non-interference (using the method of two sides hand-shaking) and under the conditions of barrier interference (using the method of three sides hand-shaking) among Sender Work Station receiver work station and the Intelligent Access Point AP.  
     [0048] While the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.