TW525065B - Intelligent roaming method applied in automatic guidance vehicle - Google Patents

Abstract

An intelligent roaming method applied in automatic guidance vehicle (AGV) connects the access point (AP) and station (STA) of wireless local area network (WLAN). By means of shortening the time for STA in searching next connected AP, the goal of fast roaming can be achieved. To save searching time, each AP will communicate with neighboring AP to complete the setup. Regardless of when to connect with AP, STA can acquire information of neighboring AP through the currently connected AP. In addition, STA keeps monitoring the signal strength of neighboring AP. During roaming period STA won't need to scan all Aps to select the best AP to connect with. (5.1) The diagram reprensenting the invention is figure 1. (5.2) The simple notation description of components in the diagram of representing the invention: 100 local area network, 101 basic services group, 102 basic services group, 103 workstation, 104 file server.

Description

525065-

.. No. 88Π8113 month

7U… a: Description of the Invention ΓΠ [Technical Field] The invention field of the present invention relates to a roaming algorithm for Wireless Local Area NetWork (WLAN). In particular, a connection method between a mobile station (m 0bi 1 e Stati ο η) and a radio local area network base station is applied to an automatic guidance vehicle (AGV) ° 'Background of the invention ~ [Prior art ] ^ According to the wireless network standard (IEEE 80 2. 1 1), a wireless LAN mobile station needs to be connected to a wireless base station to communicate with network system files, servers or other operations. Stations exchange information. This wireless base station connects a decentralized system (d i s t r i b u t e s s s t e m s) and a set of basic service areas. After a wireless base station is connected, a mobile station in a wireless local area network can communicate with a mobile station in another radio local area network at a longer distance through this radio base station. In addition, a radio base station also provides mobile stations in a wireless local area network through which the wireless base station can retrieve network resources in a distributed system. Figure 1 shows a typical hardware architecture of a wireless LAN system. Figure 1

5 ^ 3065 4 ~ Γη 88118113_ ^ Λ Β Revised_ As shown, the Ethernet local area network has two basic service sets (101 (BSSl) and 102CBSS2), and a workstation 103 and a file server (fne server) 104. Each basic service group contains one wireless base station and two wireless mobile stations. The basic service group BSS I includes a wireless base station AP1 and two wireless mobile stations STA1 and STA2. The basic service group BSS2 includes a wireless base station AP2 and two wireless mobile stations STA3 and STA4. 2. Each wireless mobile station itself must be connected with a wireless base station before it can communicate with the file server 104 or workstation 103 in B-Ethernet 1 QQ. 7 When a wireless local mobile station is turned on / This mobile station first looks for a wireless base station. After finding a wireless base station, the mobile station will register with the wireless base station. After completing the registration procedure, the mobile station can synchronize with < the wireless base station, after which the mobile station can transmit and receive data through the wireless base station. According to the wireless local area network standard (IEEE 802.1 1), the bandwidth of the operating frequency of the radio network is between 2 40 GHz and 2.50 GHz in 79 channels in the United States and Canada, as shown in Figure 2. Show. The wireless base station will be the time master to perform the time synchronization function (tlming ronization iunction (TSF)) to maintain the benchmark, and based on this benchmark, it will be the same as all wireless local area network mobile stations in the same basic service group. step. In order to synchronize with all wireless local area network mobile stations in the basic service group, for each channel, the wireless base station will periodically transmit the identification letter "Beacon". Each identification signal frame contains the wireless base station. Time b

^ 25065

The parameters of the step-by-step timer and the frequency hopping sequence The base station will call the identification interval in a fixed time interval 〇 (hopping sequence), transmitting / identification signal frame number frame interval (beacon this no The helmet that received the identification signal frame is included in the wireless base △ ψ ；: f & the local network mobile station will always use the platform to serve this 彳 + ^, do not know the number box, time information, this wireless Basic service ^ The basic service group of this mobile station ^ ^ ^ ^ ^ The time synchronization function of the station is bang. Fake ^ wireless & local network automatic time indication (time st ^ \ / different from the received identification signal The mobile station in the box will be ~ mp), the wireless local area network that received the identification signal box =, will set the internal (10cal) timer, and set the time to receive the time benefit =: when: in this service group When one of the wireless base stations is turned on, some of the wireless, local area networks are trespassing & ^ # —I Er Er Bei Zhu, and this Yuxun will be seeking this wireless base station = ㈣domain network Reference for mobile stations. The logo is used for traditional technology. The length of the frame interval (100 milliseconds) may make the wireless LAN mobile station seek wireless base stations for too long. A wireless LAN mobile station To communicate with a wireless base station, you must first register. According to the IEEE 802.1.11 standard, registration consists of two phases. The first phase is authentication (authenticati ο η). This procedure is used to identify whether the mobile station has Legal rights, capture control via a medium

525065 88118113_year month_____ V. Invent the medium access contral (MAC) layer to retrieve this wireless local area network. After the confirmation is passed, the mobile station needs to send a connection request signal frame to the wireless base station to connect with the wireless base station (c 〇nnecti 〇η 1 i nk), and then wait to receive a response frame from the wireless base station. , The box informs this connection status.

For a wireless local area network mobile station, the management structure of the secondary layer (S-u b-1 a y e r) from the search to the registration of a wireless base station is shown in Figure 3. According to the design of Figure 3, an i-line local network mobile station will perform three phases: the search (S ca η) phase, the authentication (authentication)? ^,., And the connection (ass ciati ο η) p. During the search phase, all IEEE 80 2 · 1 1 wireless LAN mobile stations start in the IDLE state (step 301). The channel hopping operation of the radio network is set by hardware 4. (Step 3 0 2). In order to find the wireless base station, the wireless local area network mobile station will search in each channel, and search for the identification signal frame sent from the wireless base, the base station (Step 3 0 3). Once found in The channel and the identification signal frame of the wireless base station are received, and the search phase is completed. Otherwise, the wireless LAN mobile station will search for the next channel and return to step 302. Set the next radio network After receiving the identification signal frame of the wireless base station, the wireless local area network mobile station sets its own channel jumping time and channel hopping according to the parameters of the identification signal frame of the wireless base station. Step (step 304) to obtain synchronization with the wireless base station. The remaining steps continue the confirmation phase and the connection phase

Page 8 525065 a! K repair-1 ^ 88118113 5th, invention correction section In the confirmation phase, IEEE 80 2 · 1 1 usually requires two-way confirmation. In step 305, the wireless LAN mobile station and the wireless base station exchange certain signal frames for confirmation. This stage can include three more steps: assertion of identity, challenge of assertion, and response to challenge. In the connection phase (step 306), the wireless LAN mobile station exchanges some connection signal frames with the wireless base station to complete the registration of the wireless base station. The communication link between the wireless local area network mobile station and the wireless base station is established. The wireless LAN mobile station can then start exchanging information boxes with the wireless base station (step 307). Because the wireless network today operates between 2.40 GHz and 2.50 GHz, frequency hopping. According to the Federal Communications Commission (FCC) regulations, the wireless LAN mobile station may be in 7 or 9 channels. Take a while to search for a wireless base station that may work on any channel. Each box for confirmation and connection must be sent out according to the standard of 802.1.1 (Carr i e r Sense Multiple Access with Collision Avoidance CSMA / CA). For a wireless local area network mobile station, the time it takes to complete all the processes of confirmation and connection varies greatly and can not be expected, especially when the information traffic of the wireless channel is busy. Therefore, for wireless local area network mobile stations that follow the IEEE80 2. 1 1 standard,

Page 9 525065, Dazheng Case No. 88118113_Year Month Revision_ V. It is unpredictable that all the time from issuing ^ (6) wireless base stations to completing registration. From the above-mentioned know-how, it can be seen that the shortcomings of the traditional acquisition technology are not enough for the connection efficiency between the wireless local area network mobile station and the wireless base station. Therefore, for wireless local area network mobile stations, there is an urgent need for more rapid connection technology to quickly capture a wireless local area network 0 through a wireless base station.

Problem description for this creation ^

Generally speaking, wireless LAN is used in the field of work. A vehicle passes multiple basic service groups (BSSs) along a pre-designed < good path. Existing roaming algorithms in NDC cannot support this application. Switching from the current base station to the next base station is similar to the application of a mobile phone without any delay. Due to the mobility of the Automatic Guidance Vehicle, this delay is key for waste applications. For example, the scan time of each channel is 200 seconds (minisec ο nds), so if there are 80 jumping channels, it takes an average of 8 seconds for an automated guided vehicle to communicate with The base stations in the basic service group establish a connection. This is a long time delay. Usually within this time interval, the automated guided vehicle has moved a long distance. As a result, many messages between the automated guided vehicle and other control units cannot be communicated. Automated guided vehicles will lose guidance and cause industrial safety issues in factories.

Page 10 525065, La Dazheng case number 88118113 _ year, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, month, year: Rev. _ _V. Invention Therefore, an intelligent roaming algorithm is needed to solve this problem. According to this roaming algorithm, it is hoped that the search time for jumping from one basic service group to another basic service group can be greatly reduced. [Summary of the Invention] The purpose of the present invention is to provide an intelligent roaming algorithm for automatic guidance vehicles (AGV) to support the processing of base stations in wireless local area network systems. The guided vehicle can roam on a predetermined path. The key to achieving fast roaming is to reduce the time for the mobile station to search for the next base station to roam to. To achieve the purpose of reducing the search time, each base station and the neighboring base stations need not be set in advance. During the connection, the mobile station can obtain the information of its neighboring base stations from the base station to which it is currently connected. In this way, the mobile station can continue to monitor the signal strength of nearby base stations. During roaming, the mobile station can select the best base station connection without searching all channels. [Embodiment] The detailed description of the preferred embodiment: 1. Introduction: First, the intelligent roaming algorithm of the wireless local area network work system will be described. And in the best embodiment details

Page il I ........ Dazheng Case No. 88118113_Year / Month / Year Revision_ 15th, Issue Date ¥ 1 > Day Pet > (8) The detailed settings will be explained later. Those skilled in the art should understand that the description in the text can only be used as an example, and the present invention can be understood by the description in the text. In addition, those skilled in the art can modify this embodiment within the scope and spirit of the invention as defined by the scope of the patent application. 2 · Purpose:-In a traditional system, a mobile station must search every channel (there are 79 channels in the Federal Communications Commission (FCC) adjustment zone), and find one that is most suitable for connecting with the mobile station during roaming. Base station. For some time-critical applications, too long a search time is not allowed. Therefore, an algorithm was developed to reduce roaming time to meet the requirements of this critical application. In addition to fast roaming, the design of the present invention allows a mobile station that is roaming to move freely in any direction when it leaves the coverage area of the connected base station. This design can make the system more flexible. In addition to roaming, the invention also improves the search algorithm after the mobile station is turned on. Applying the modified algorithm of the present invention, the mobile station can always find the best base station and connect with it after it is started. 3. Algorithm:

Page 12 525Q65 _-- i etc. Amendment

Case No. 88118113 Λ Yue Xiu "This section will briefly describe the intelligent roaming rendering method that can shorten the search time. The key to achieving fast roaming is to reduce the time it takes for the mobile station to search for the next base station to roam to. In order to reduce the search time, each base station is set in advance with neighboring base stations. During the connection period, the mobile station can obtain the information of the base stations adjacent to itself from the base station to which it is currently connected. In this way, the mobile station can continuously monitor the signal strength of base stations in its vicinity. During roaming, Xingwu Station can choose the best base station connection without searching all the channels of Brother. The intelligent roaming algorithm consists of five parts, which are explained as follows: 3.1 Synchronization This section explains how these 4 base stations are combined with the smart roaming function and how the base stations are connected via Ethernet. Timing Synchronization Function (TSF). Synchronize with other base stations. In addition, the present invention also includes a back up algorithm to solve the problem of disconnection when the time master (t i m i n g m a s t e r) is disconnected. (1) To achieve these functions, a base station must be set in advance by the network management system (NMS) as the timing master of the time synchronization function (TSF). With the master of time, this master base station will cycle through the Ethernet net work

Page 13 52506 ^ Case No. 88118113 January said the time of the modified transmission time synchronization function (TSF), and allows other base stations to update the time of the time synchronization function while maintaining synchronization with the master access point. (2) All other base stations, which we call slave access points (siave access point)-until the time of receiving the time synchronization function (TSF) sent by the master base station. After selecting the same time synchronization time (TSF) as the master base station, the slave base stations can start their basic service group. After that, when the slave base station receives the time of the high-step function (TSF) transmitted from the master control base station, the slave base stations need to dynamically adjust their internal timers to fly 10cal timer to maintain and Master control base station synchronization. Using this method, all base stations and mobile stations can synchronize their time with the time synchronization function (TSF). It is worth noting that according to the wireless LAN standard 8 〇 2 i 1 (IE £ E 8 0 2 · 11), the base station and the connected base station can periodically pass the wireless beacon frame. Make time synchronization work synchronized. (3) In addition to the main control base station, from now on we are called the first main control (γ imary-maSter) base station, and can also be set through the network management system (netw0r ^ ma = gement SyStem, NMS) Two main control (SecOnda port Ster) base stations. If the first main control base station is disconnected after the second main control base station has not been determined, the second main control base station will take over the first main main base station and periodically transmit its time synchronization two ("η ° time so that the time of the entire system can be synchronized.

Page 14 Correction

\ 4A Case No. 88Π8113 (11) Month and Day_Amendment 3.2 Neighboring APs This section describes the algorithm, including how each base station collects information about its neighboring base stations and how the mobile station Get this information. (1) Through a network management system (NetWOrk Management SyStem, NMS), each base station and neighboring base stations must be set in advance (2) all base stations existing in the same subnet (s U b-net), It is necessary to know the hopping pattern and hopping set (h 0 pping Set) of other base stations. In order to achieve this, each base station periodically transmits its own frequency hopping information to the Ethernet. (3) After opening and synchronizing, the base station will receive the frequency hopping data of the neighboring base station through the receiving transmission frame described in (2) above, and then store the received information into their database ( database). In this way, through the Ethernet exchange of information, each base station will hold the frequency hopping information of base stations in the same subnet and adjacent base stations. (4) In terms of connection, the mobile station will first request the base station currently connected to provide frequency hopping information of the neighboring base station, at any time as long as the base station receives an association-request from the mobile station, The base station must respond to the mobile station with the frequency hopping information of the base station adjacent to it in the association-response frame. Therefore, after the connection is completed, the mobile station will know

% lMll _ Case No. 88Π8113 (12) Amendment Frequency hopping information of the base station adjacent to the base station. 3 · 3 Detect the identification signals of neighboring base stations (sn i f f i n g t h e Beacon of neighboring APS) Referring to Figure 4, after connecting with the base station, the mobile station has obtained the frequency hopping information of the neighboring base station. Then the base station can continuously detect the target and identification signals of the base station adjacent to itself. The mobile station will also store the Received Signal Strength Indicator (RSSI) value converted from the collected identification signals into its own database. When the mobile station is roaming, this information will be referenced. It is worth noting that the received signal strength index (RSS I) value converted from the received identification signal can be regarded as the relative distance index value of the mobile station and the neighboring base station. If the received signal strength index value is large, it shows that the distance between the mobile station and the base station is short. Therefore, when roaming, the mobile station always selects and associates with the base station with the best received signal strength indicator (RSS I) value. The method of detection (S n i f f) will be described in detail below. (1) If the frequency hopping dwell (h 〇ppingd We e 1 1) time is set to a multiple of the mark to the frame interval (B eac ο ninterva 1), the base station will start at the beginning of each frequency hopping dwell Just transmit its identification signal box. Because each base station and mobile station have been synchronized and the mobile station has obtained the frequency hopping information after connecting with the neighboring base station, the mobile station can directly jump to the base station channel adjacent to the mobile station and stay for a short time Go and listen to the identification signal from the neighboring base station. If during this period

Case No. 88118113 _Ά Correction When the identification signal is received, the received signal strength indicator (RSSI) value in the identification signal will be stored in the database of the mobile station. Figure 4 shows how the mobile station hops between the currently connected base station and its neighboring base station at each frequency hopping start detection (Sn i f f) identification signal. (2) During the detection period, the base station and each associated mobile station cannot transmit data packets (P a c k e t s). Only the identification signal frame sent by the base station can be received in space during this period. "(3) At the beginning of each hopping channel, the mobile station will continue to detect the identification signal of the base station adjacent to itself. (B eac ο η). In addition, the sequence of detection (Sn i f f) will be performed successively between neighboring base stations. For example, if there are multiple adjacent base stations (Base Station 1, Base Station 2 and Base Station 3), the sniff will be Base Station 1—Base Station 2— ^ Base Station 3 then return to the original sequence of base station 1 to continue execution. (4) For each adjacent base station, the mobile station will save the last four received signal strength (RSSI) values collected by the identification signal. When the mobile station is roaming, the RSSI value is used as a reference. This means that the mobile station can obtain the signal strength of the neighboring base station in the instant of roaming. 3. 4 Roaming This section explains how a mobile station decides to roam to the best mobile station in a base station close to its own base station. It also describes the use of the mobile station when it cannot be connected to all adjacent base stations.

Page 17 525065 1 ~ £ I. The algorithm issued Poor case 5 Tiger 88118113

4)

(1) As in the algorithm described in the previous section, the mobile station will retain the received signal strength indicator (RSS I) results for the last four measurements. When roaming is started (that is, the quality of the received identification signal is lower than ^ You = Pro, value), the mobile station will first average the received signal strength of the last two detection identification signals of every _ adjacent $ Base ports Identification (RSSI) value. If the identification signal is not received for the last two attempts and the primary test, the mobile station will refer to the received signal strength (Rgs) value of the identification signals of the last third to fourth tests and will receive the average # Number intensity value. This is designed for situations where the Prudential Signal Box may be lost due to interference. The received signal strength values of all neighboring base stations are averaged at the mobile station, and the mobile station will arrange the average values in descending order and connect them in sequence. It is worth noting that the mobile station will consider the adjacent base and platform to be non-existent if no identification signal frame is received for the last four attempts to detect, and will not continue to connect. (2) If the mobile station cannot connect with all neighboring base stations, including the example of the missing identification signal frame of the last four detections, the mobile station will start scanning all channels to find the best connected base station. 〇 (3) Because the base station does not need to be scanned, the delay time for roaming is only for authentication, association, and s / w overhead. Note: The purpose of the smart roaming algorithm is to shorten the roaming time. There is no guarantee that data packets can be received during roaming.

525065

3.5 Searching for a base station at startup This section describes how the mobile station is starting up (b 00te has found the best connected base station. 6 UP) (1) When starting up, the mobile station will detect all jumps And, this kind of behavior is called "quote" in the wireless LAN standard 802.1.1. This scan (active scan). If one of the channels receives a probe request dynamically, the base station will immediately acknowledge the base station and a probe response frame (r e s ρ ο n s e f r a m e). Inspoke, after detecting all channels, compare the received signal strong sound = standard (RSSI) value of the probe response, the mobile station can choose the best, receive ^ 'intensity (RSSI) value and compare with this base Taiwan connection. 17 b (2) Therefore, when the trend station is detecting, the base station may jump around in the vicinity of the task. The mobile station needs to scan all the channels four times to determine all the base stations. The station can be completely detected in this area. Found. 4 · Synchronization time of the base station 4.1 ETHE-BEACON frame As described in Section 3.1, the main control base station needs to periodically transmit its time synchronization function (TSF) through the Ethernet. time. Therefore, a multicast box is defined as the time synchronization function (TSF) time of the transmitting master base station. In addition, this multiple transmission frame is hereinafter referred to as the Ethernet identification signal (ETHE-BEAC0N), which can be used to transmit

Page 19 525065 13 • Positive ^^ 88118113 Five (16) Λ_ Correction Jump information of the base station, this part will be mentioned in section 3.2. After the release of the basic service group (BSS), each base station will continuously transmit the Ethernet identification signal (ETHE-BEACON) to the Ethernet. Figure 5 shows the format of the Ethernet identification signal (ETHE-BEACON). In this format, the destination address (Destination, Address, DA) of the Ethernet identification signal (ETHE-BEACON) box is set to f, 03: 〇〇: 〇0: 0: 00: 0 7 π , Is the same as the setting of roaming noti fi ca ti on frame. The Source Address (SA) is the Ethernet Media Acquisition Control (MAC) address of the transmitting base station. The length of the Ethernet identification signal frame is one byte and its value is fixed at 72. The type is used to distinguish the form of the MAC box from other boxes on the network. Select the appropriate value for the Ethernet identification signal (1 2 3 4 in 16-bit) to avoid duplication with other media, access control (MAC) boxes. The user can specify the alias of the base station as a logical name through the settings of the network management system (NMS). Wireless LAN network domain name (ESS ID), wireless network base station name (BSS ID), hopping group and hopping pattern are parameters of wireless hopping information, in order to achieve the purpose of connection , These parameters will be referenced by the roaming mobile station. If the Ethernet identification signal (ETHE- beacon) is transmitted by the master base station, the time synchronization function (TSF) will include the time stamp of the time synchronization function of the master base station. Otherwise, the Ethernet sent from the slave base station

Page 20

Month correction ^ The time synchronization function (TSF) value of the ET HE-BE AC ON signal will be 0 4 · 2 and transmitted. When the master control base identifies the signal frame, it will be framed every 10 seconds. Once the network identification letter of the controlling base station is transmitted from the beginning of the network identification letter to the Send ETHE-BEACON station within 10 seconds, the Ethernet will be sent out immediately. Go to Ethernet. After that, the master base station will send an Ethernet identification signal (ETHE-BEACON). The slave base station receives the Ethernet number transmitted by the master and base station. The slave base station will delay the standby time and then turn on. The Ethernet identification signal is transmitted to the Ethernet. Just like the master action, when the slave base station sends out the first ethernet number (ETHE-BEA.C0N), the slave cemetery will also transmit the Ethernet identification signal (ETHE-BEACON) on 0 4 _ 3 Filtering the wireless LAN network domain name and neighboring base stations (ESSID filtering and neighboring APS) When the base station receives the Ethernet identification signal (ETHE-BEACON) box, it should filter out the wireless LAN network Signal box with different domain name (ESS ID). If the wireless LAN domain name (ESS ID) is the same, the contents of the Ethernet identification frame will be stored in the database. In the current design, a base station database can store up to 20 jump information. Regardless of the SrT mobile station requesting the connection, the base station needs to filter out the base stations close to itself from the database and send this information to the mobile station. In the current design, a base station can set up to 4 adjacent

Page 21 525065 Tiger 88118113 ___ Month Day Amendment _ 1 V. Invention Near base station. 4.4 Timed Timer and Back Up Master (Agingtimer and back upmaster) A timed timer is set to 60 seconds for each member in the database. When the base station receives the Ethernet identification signal (E T Η E-B E A C 0 N), the time control meter and timer will be reset. If the Ethernet identification signal (ETHE-BEACON) is not received before the time-controlled timer expires, the members of the database will be deleted. If the first master control base station fails, the second master control base station actively assumes the role of the master control base station and continuously uses the Ethernet identification signal (ETHE-BEACON> box to transmit its time synchronization function (TSF ) Time. If the second master and the second master base station fail at the same time, the mobile station in the minimum jump mode will actively assume the role of the master base station and will start transmitting its time synchronization function (TSF) time to maintain time synchronization Function synchronization. When the base station starts, if the first master control base station is disconnected and no longer transmits the Ethernet identification signal (ETHE-BEACON), the second master control base station will start after 15 seconds. Send the Ethernet identification signal (ETHE-BEACON) and add its own time synchronization function (TSF). 5. System configuration (System configuration) When the installed system has the function of intelligent roaming, this section states that you must pay attention to The main points.

Page 22 I Case No. 88118113 ¥ _η Revision 5.1 Set base station and roaming mobile station have the same wireless LAN network domain name (Set APS and roaming STAS to the Same ESSID) Set the same wireless LAN domain name (wireless zone 'domain name) so that roaming mobile stations can be associated with it. The smart roaming base station will filter the values of different wireless LAN and road network domain names in the Ethernet identification signal box. If the wireless LAN domain name of the mobile station is different from that of the base station, the mobile station cannot receive frequency hopping information from the base station nearby to it. 5.2 Assign a unique alias and frequency hopping sequence to each base station Before setting 4 neighbors of the base station, each base station must set a unique alias by the network management system (NMS). After setting the alias, the system administrator can start to set the neighbors of the base station. In addition, each base station must set a different frequency hopping sequence to avoid examples where more than one basic service group may have overlapping channels. Similarly, through the setting of the network management system, the setting of the frequency hopping sequence can be done better. 5.3 Set neighboring base stations based on geographic location Because roaming mobile stations need to select base stations based on the Received Signal Strength Index (RSSI), it means that when roaming mobile stations are adjacent to

Page 525065

JL Case No. 88118113 Amendment

Depending on the geographical location of the environment, the relative distance between base stations must be set as appropriate. As shown in Figure 6, there are four base stations (base stations i, hu 2, and ground σ 3 and base σ 4), which are installed around base station 0, part of the culvert = Fanyuan signal overlap, and base station 0 ( (AP0) The base station (αρι), base station 2UP2), base station 3 (AP3), and base station 4 (Αρ4) can be set as base stations adjacent to themselves. So-come, when the base station mobile station leaves the area covered by these letters, these neighboring base stations will be referred to by the roaming mobile station. ~ 5 · 4 Designating the master control base station To achieve synchronization, the system administrator must designate a base station as the first master control base station in the wireless local area network (ESS). In addition, in addition to the first main control base station, the system manager must also select another base station as the second main control base station to serve as a backup for the first main control base station. 5 · 5 Connect the base station to the same Ethernet subnet (◦ 〇nnecta PS to the Same Ethernet Subnet) Now that the Ethernet identification signal (ETHE-BEACON) frame will be transmitted by multiple transmission frames (mu 11 icastframe) When transmitting to Ethernet, the smart roaming base station should be able to connect with the Ethernet cable (Cab 1 e) and correctly receive multiple transmission frames from the same local area network domain (ESS doma i η).

Page 24 5 · 6 Set each base station to have the same frequency hopping dwell time, identification signal period and carrier setting (Carrier Set) Wireless frequency hopping information dwell time, identification signal period and frequency band setting are not included in Ethernet Road identification signal box. Therefore, each base station sets these data in the same ESS domain in order to ensure that the settings of these parameter values are the same. These parameter values are the same at the initial setting. In addition, in order to detect the identification signal of a neighboring base station at the beginning of each frequency hopping dwell time, the frequency hopping dwell time must be set to a multiple of the identification signal interval (b e a c ο n i n t e r v a 1 s). For example, the frequency hopping dwell time and the time for identifying the interval of the signal frame are set to 200 hp seconds and 100 hp seconds, respectively. With these values, the mobile station can successfully detect the identification signals of the base stations adjacent to it. 5 · 7 mobile stations must be started after the relevant information of the base station is established (Start APS in ahead of STAS) When the system starts, all base stations must be turned on before all mobile stations can be activated (note that 30 seconds before the start of the station). This is because the base station needs time to do hardware self-test, time synchronization function (TSF) synchronization, and collect information about the neighboring base stations. After doing these actions, the mobile station can start and then connect with the best base station and receive the willow y • Zheng fr r Case No. 88118113 Λ: _ said amendment (22) 5.8 The coverage of the base station is To provide a network connection for roaming mobile stations, adjacent base stations must be installed with overlapping coverage. The quality of the received identification signal (meaning the percentage of the signal quality between the base station and the mobile station) and the critical value of roaming (settable parameters) will determine the roaming coverage and roaming time. For example, if the quality of the identification signal of the roaming mobile station falls below the critical value, the mobile station will start roaming to the next base station. Therefore, if a higher threshold is set, the coverage range of the base station will be smaller, and the mobile station will switch base stations more frequently. Therefore, after the mobile station is connected to the base station, the identification signal quality of the adjacent base station can be accurately calculated in the next 4 seconds. Therefore, the system administrator can install a base station within the signal coverage area. This coverage area can support the mobile station's movement distance of at least 4 seconds. Figure 7 illustrates this situation. 6. Algorithm, description The algorithm of the present invention will be described briefly below. 6.1) Each base station must first set the relevant position with its neighboring base stations. For example, take base station 2 as a reference, and its settings are base station 3 in the west, base station 1 in the east, base station 4 in the north, and base station 5 in the south. When the base station is activated, in addition to its own frequency hopping information, it also needs to transmit an Ethernet identification signal (ET HE-BE A CON) frame including information about its proximity.

Page 26

6 · 2) When the mobile station is connected with the base station, the mobile station will download the frequency hopping information of the neighboring base station from the currently connected base station. 6 · 3) In other cases, the mobile station must scan the neighboring base stations and find the best base station and connect to it. The best connected base station is determined by the signal strength index (RSS I) value, and the signal strength index value is collected and collected by the base station identification signal frame. Since the mobile station already knows the peach frequency information of the neighboring base station after the connection, it will be shorter than the scanning time required for the mobile station to synchronize directly with the neighboring base station and listen to the identification signal frame. For example, if it is shown that the L a interval (Be aeon interval) is set to listen to 10 milliseconds (ms), then the time taken to scan 4 adjacent base stations is I, which is 4 5-5 0 ¾ seconds. This arrangement is ideal for mobile stations that can 祜 '^ 1 Shang Shi He Da roaming. ^ Direction 6 · 4) When activated, the mobile station needs to scan all hopping channels to receive the identification signal frames of all base stations (negative scanning). According to the received signal strength (Beacon), the received signal strength index (RSSI) value is compared, and the mobile station can select and connect to the base station with the best received signal & strength index value. If; j: ticket signal interval (B eac ο η I nterva I) is set to I 0 milliseconds (ms), the mobile station will take 2 4 0 0¾ seconds (80 channel scans 3 times to determine that all base stations have been Discover) to discover the best base stations. In the example of an Automatic Guidance Vehicle (AGV), an automatic guidance vehicle may

Page 27 5-25065, etc. Case No. 88118113 #: _η Correction (24) positions are activated. If this method is used, the mobile station can calculate the best base station and connect to it. 6.5) After the connection, the mobile station will download the frequency hopping information of the next adjacent base station depending on the connected base station. When all adjacent base stations are disconnected, the roaming mobile station will use the method mentioned in 6.4) to select an optimal base station to connect to.

P.28 _n Correction

Case No. 88Π8113-Belonging to the Schematic Illustration: Figure 1: illustrates the typical hardware architecture of a wireless LAN system. Figure 2: According to the wireless local area network standard (I E E E 80 2. 1 1), the frequency hopping bandwidth of radio signals in the 79 channels in the United States and Canada is between 2.04GHZ-2.50GHZ. Figure 3: For a wireless local area network mobile station, from the search to registration with a wireless base station and a wireless base station-traditional media capture r ', medium access control MAC (sub-1) ay er) management architecture. Figure 4: illustrates the detection procedure of the present invention. ~ Figure 5: Schematic illustration of the Ethernet identification signal (ETHE-BEACON) of the present invention ° Figure 6: Illustrates the geographical location of adjacent base stations of the present invention. Figure 7: Explains the covered garden of the base station of the present invention.

Schematic and number description 100 domain network 101 basic service group 102 basic service group 103 work station 104 file server 301 idle state 302 person rL

Page 30

Claims (1)

52S065- Year I. 3. / Case No. 88118113 Amendment-Six τ 肀 Please ¥ _ Scope 1. A connection between a mobile station (station, STA) and an access point (Access Point) in a wireless local area network with multiple base stations , A P) method, which is applied to an automated guided vehicle. The method includes the steps of: in advance, defining each base station and a neighboring base station in advance according to the related positions of the plurality of base stations mentioned previously; when the base station is When connecting, download the wireless frequency hopping tribute to the base station adjacent to the currently connected base station; and, when the roaming starts, select the best base station to connect with the mobile station. The method of use includes the steps: a. Determine whether the roaming direction is There are mobile stations; b. Assuming that there are base stations in the direction of roaming, a neighboring base station is selected as the best base station and connected to it so that the direction of roaming can continue; otherwise, C. scanning is adjacent The base station also selects one that has the highest received signal strength as the best base station. 2. The method described in the first item of the patent application, wherein when the base station selected in step b is disconnected or cannot be connected to it, use step C to select an optimal base station. 3. The method as described in the first item of the scope of patent application, wherein each base station continuously transmits the identification signal frame to the Ethernet in the wireless local area network, and the parameters of the wireless frequency hopping information of the identification signal frame include hopping. Frequency type and frequency hopping set0 Page 31 525065 pi Zheng, case number 88118113 _ year and month amend _ six ^ Shenzai Wai 4. A method for connecting a mobile station and a base station as described in the first item of the scope of patent application, wherein the received signal strength of the base station It is the value of the received signal strength indicator (RSS I) of the identification signal frame transmitted by the base station. 5. A method for connecting a mobile station and a base station as described in item 4 of the scope of the patent application, wherein after the mobile station downloads wireless frequency hopping information of a base station adjacent to the currently connected base station, the mobile station will hold and continue Detect the identification signal frame of the adjacent base station and store the received signal strength (RSSI) value of the received identification signal frame. 6. A method for connecting a mobile station and a base station as described in the fifth item of the patent application park, wherein the frequency hopping resident period is a multiple of the identification signal interval and the base station transmits it at the beginning of each frequency hopping resident period Identification signal box, the mobile station will synchronize and stay with each directly jumping base station, and listen to its identification signal box for a short time. 7. A method for connecting a mobile station and a base station as described in item 5 of the scope of the patent application, wherein the mobile station retains the received signal strength (RSS I )value.