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Westermo RM-240, Справочное руководство

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6193-5201

3.2 Selecting a Channel

The RM-240 conforms to the IEEE 802.11 Wireless LAN specification. The RM-240 sup-
ports 11 radio channels, each 5MHz wide, in the range 2412MHz to 2462MHz. Only one 
of these channels is used for a connection. The desired channel is selected and config-
ured at the Access Point, and is then used for all beacon transmissions and connections. 
Clients scan all 11 channels for a suitable Access Point and then adopt the same channel 
as the AP when a connection is established. Although each channel is only 5MHz wide, 
the radio transmission is a lot wider. Hence the channels overlap. The following diagram 
shows the RF energy distribution for a WiFi transmission:

Most of the energy is in a central 22 MHz wide “lobe”, centred around the channel fre-
quency, however there are also side-lobes extending either side.

If we ignore the side lobes and consider each WiFi message as a 22MHz wide transmis-
sion, then the following diagram represents how transmissions in each channel overlaps.

If there is more than one WiFi AP within the same wireless range, then it is important 
that the AP’s are on channels as far apart as possible. If there are only two AP’s, then set 
them to 1 and 11. If there are three, set them to 1, 6, 11.

It is also important that correct channel is selected for region. Channels 1 to 11 are 
approved for North America (FCC), Europe (ETSI), Canada (IC) and Australia (ACMA). 
Channels 10 and 11 are approved for use in Spain and France. Refer to the relevant regu-
latory authority for the region as to which radio channels are approved for use.

 

f-33  

 f-22 

f-11 

 f 

f+11 

f+22 

f+33

RF power distribution in a WiFi transmission with channel central frequency,

Содержание RM-240

Страница 1: ...Wireless Ethernet Radio Modem www westermo com Westermo Teleindustri AB 2007 Reference Guide 6193 5201 RM 240 ...

Страница 2: ...2 6193 5201 Thank you for your selection of the RM 240 Wireless Ethernet Modem We trust it will give you many years of valuable service ...

Страница 3: ...sure requirements in section 1 1310 of the FCC Rules antennas used with this device must be installed to provide a separation distance of at least 20 cm from all persons to satisfy RF exposure compliance DO NOT operate the transmitter when someone is within 20 cm of the antenna operate the transmitter unless all RF connectors are secure and any open connectors are properly terminated operate the e...

Страница 4: ...chnologies first 1 A radio license is not required in some countries provided the module is installed using the aerial and equipment configuration described in the RM 240 Installation Guide Check with your local distributor for further information on regulations 2 Operation is authorized by the radio frequency regulatory authority in your country on a non protection basis Although all care is take...

Страница 5: ...connec tions It is possible to use all three data connections concurrently allowing the RM 240 to act as a Device Server Wireless connections can be made between serial devices and Ethernet devices however approriate driver applications are required in the host devices to handle the different data format The RM 240 does provide connection funtionality between serial Modbus RTU devices and Ethernet...

Страница 6: ...eless links to the Client units and controls the wireless communications The first diagram shows two Ethernet devices being linked One RM 240 is configured as an Access Point and one as a Client in this example it doesn t mater which unit is the Access Point The second diagram shows an existing LAN being extended using RM 240 s In this example the Access Point should be configured at the LAN end a...

Страница 7: ...ng an existing Ethernet LAN For a Bridge the IP address for the wireless side is the same as the Ethernet side A Router connects devices on different LAN s The IP addresses for the Ethernet and wireless sides are dif ferent In the above example the wireless link is part of LAN A with the Client unit acting as a Router between LAN A and LAN B Alternately the Access Point could be configured as a Ro...

Страница 8: ...n will allow you to configure the units quickly First read Section 2 Installation The RM 240 requires an antenna and a power supply Power the RM 240 and make an Ethernet connection to your PC for further infor mation on how to do this refer to section 3 3 Set the RM 240 address settings as per section 3 4 Save the configuration the RM 240 is now ready to use Before installing the RM 240 bench test...

Страница 9: ... on the type and location of antennas the degree of radio interference and obstructions such as buildings or trees to the radio path The maximum range achievable depends on the regulated RF power permitted in your country and whether you use separate transmit and receive antennas With a single antenna 5 km 3 miles can be achieved in USA Canada and Australia 4W ERP and 1km in Europe 100mW ERP With ...

Страница 10: ...oving equipment in the area then the solution is to use two antennas Because the two connectors are separated the RF signal at each connector will be different in the presence of multi path fading The RM 240 unit will automatically select the higher RF signal Note that directional antennas are not normally used in plant and factory installations Line of sight installations In longer line of sight ...

Страница 11: ... lems with radio systems as it greatly increases the radio losses We recommend that the connection be taped firstly with a layer of PVC Tape then with a vulcanizing tape such as 3M 23 tape and finally with another layer of PVC UV Stabilized insulating tape The first layer of tape allows the joint to be easily inspected when trouble shooting as the vulcan izing seal can be easily removed Where ante...

Страница 12: ...xial cable however a cable must be used with the collinear antennas Collinear and dipole antennas should be mounted vertically preferably 30 cm 1 foot away from a wall or mast to obtain maximum range b b c bjb 8DA C 6G 6CI CC6 B6HI 6GI HI6 GDJC9 8DC9 I DCH 6G EDDG CHI6AA BDG I 6C CHI6AA 6 G 6A 67DK AD86A D7HIGJ8I DCH 6CI GB HJG 6GG HIDG DEI DC6A 8D6M 6A 867A L 6I GEGDD 8DCC 8IDGH L I B º I6E HIG H...

Страница 13: ...rtically mounted omni directional antenna then the Yagi elements should be vertical If the Yagi is transmitting to another Yagi then the elements at each end of the wireless link need to in the same plane horizontal or verti cal Directional radomes should be installed with the central beam horizontal and must be pointed exactly in the direction of transmission to benefit from the gain of the anten...

Страница 14: ... provide efficient surge protection for the module refer to the Installation Diagram 2 4 Serial Connections 2 4 1 RS 232 Serial Port The serial port is a 9 pin DB9 female and provides for connection to a host device as well as a PC terminal for configuration field test ing and for factory testing Communication is via stand ard RS232 signals The RM 240 is configured as DCE equipment with the pinout...

Страница 15: ...nits on the RS 485 cable may send data at any one time Thus communication protocols based on the RS 485 standard require some type of arbitration RS 485 is a balanced differential standard but it is recommended that shielded twisted pair cable be used to interconnect modules to reduce potential RFI It is important to maintain the polarity of the two RS 485 wires An RS 485 network should be wired a...

Страница 16: ...93 5201 HJEEAN GH 9 E HL I8 DG DHI DHI GB I GC I 9 D 9 6JAIH 9 E HL I8 GH XdccZXi dc jh c iZgb cVi c gZh hidg GH 100M RUN SETUP LINK MDI X ETHERNET DCE ON OFF RS 485 RMINATION RS 232 RS 485 COM T T DTO POWER ...

Страница 17: ...aintain reliable operation of driving relays The digital input is connected between the DIO terminal and common COM The I O circuit includes a LED indicator which is lit when the digital input is active that is when the input circuit is closed Provided the resistance of the switching device is less than 200 ohms the device will be able to activate the digital input The I O channel may also be used...

Страница 18: ...ed perhaps from an Access Point If the Client finds suitable Access Points during the scan it will then attempt to establish a link with the Access Point with the strongest radio signal Link Establishment When the Client wishes to establish a link with an Access Point it follows a two step process The first step is authentication During this step the Client and Access Point check if they can estab...

Страница 19: ...taining a link with the most suitable AP LED Indication The following table details the status of the indicating LEDs on the front panel under normal operating conditions LED Indicator Condition Meaning OK GREEN Normal Operation OK RED Supply voltage too low Radio RX GREEN flash Radio receiving data Radio RX RED flash Weak radio signal Radio TX Flash Radio Transmitting Radio LINK On On when a radi...

Страница 20: ... lobe centred around the channel fre quency however there are also side lobes extending either side If we ignore the side lobes and consider each WiFi message as a 22MHz wide transmis sion then the following diagram represents how transmissions in each channel overlaps If there is more than one WiFi AP within the same wireless range then it is important that the AP s are on channels as far apart a...

Страница 21: ...essed via the RS 232 serial port Accessing Configuration for the first time There are two methods for accessing the configuration inside a RM 240 The first method requires changing your computer settings so that the configuring PC is on the same network as the RM 240 with factory default settings This is the preferred method and is much less complicated than the second method You will need a strai...

Страница 22: ...network the gateway IP address and network mask a Switch Factory Default dip switch on RM 240 to SETUP position b Connect the RS232 port on the RM 240 to the RS232 port on the PC using a straight through serial cable c Open a terminal package such as Hyperterminal with 19 2 kbit s data rate 8 data bit 1 stop no parity and no flow control Make sure that no other programs have control of the serial ...

Страница 23: ...before connecting to an existing LAN consult the network administrator A system of RM 240 s must have at least one Access Point acting as a master to one or more Clients All RM 240 s to be configured as part of the same wireless network should be given the same System Address SSID and Radio Encryption settings For further information and examples on wireless network topologies refer section 1 1 ab...

Страница 24: ...e IP address of the RM 240 on its wired Ethernet port This should be set to the IP address you require Ethernet IP Subnet Mask The IP network mask of the RM 240 on its Ethernet port This should be set to the IP address you require Wireless IP Address The IP address of the RM 240 on the wireless port If the unit is configured as a bridge this address will be the same as the Ethernet IP address If c...

Страница 25: ...P keys must be entered as pairs of hexadecimal digits separated by colons Hexadecimal digits are in the range 0 9 and A F 64bit WEP requires 10 Hexadecimal digits and 128bit WEP requires 26 Hexadecimal digits For example 12 AB EF 00 56 for 64bit encryption and 12 AB EF 00 56 15 6B E4 30 C8 05 F0 8D for 128bit encryptionEncryption keys must not be all zeros i e 00 00 00 00 00 Passphrase When WPA En...

Страница 26: ...however by keeping a list of devices heard on each port the transparent bridge can decide which traffic must be forwarded between ports it will only transfer a message from the wired port to the wireless port if it is required A bridge will forward all Broadcast traffic between the wired and wireless ports If the wired network is busy with broadcast traffic the radio network on the RM 240 can be u...

Страница 27: ...ns that a RM 240 client station in 4 address mode can bridge any Ethernet traffic not just IP based traffic as with 3 address mode 4 address mode should also be used if the bridge Spanning Tree Protocol is required When a RM 240 client station uses 4 address mode any Access Point that it is to communicate with must also be configured for 4 address mode Router Operation A router joins separate Ethe...

Страница 28: ...e difference between the Basic Rate and the radio Data Rate is that it only applies to multicast radio transmissions and man agement frames The Basic Rate is generally set to a lower value than the Data Rate since multicast transmissions have no inherent error correction mechanism Select the Radio Menu to change the following configuration parameters If a change is made you need to select Save Cha...

Страница 29: ...SID by passively listening to beacon transmissions from the Access Point When disabled Access Points will not transmit the System Address openly in Beacon messages This is particularly useful in unencrypted radio networks Disallow Probe Requests without correct SSID This should be used to prevent unwanted users from detecting the radio network System Address SSID actively by sending a probe reques...

Страница 30: ...lly enabled to repair the network if another link is lost The Spanning Tree Algorithm maintains a single path between all nodes in a network by forming a tree like structure The Bridge Priority determines where the node sits in the tree A Bridge configured with the lowest priority 0 will become the root node in the network and will direct traffic between each of its branches The root node is typic...

Страница 31: ...ryption WEP keys should be the same for all Access Points that are to communicate with each other Each WDS interface can be either a bridge or router interface refer section 1 1 Network Topology for more information on bridge vs router If you need a simple repeater net work use a bridge interface A WDS bridge interface allows traffic to be bridged to another Access Point on the same IP network WDS...

Страница 32: ...hey were all on the same wired segment It can bee seen that there are redundant paths and also the possibility for loops to occur so that the bridge Spanning Tree Protocol should be enabled To illustrate the redundancy consider that if A needs to send data to D it has redundant paths through both B and C However due to the spanning tree pro tocol only one of B or C will relay the data with the oth...

Страница 33: ...ys broadcast in beacons whereas the SSID broadcast is configurable Unit B in the WDS router example above has three WDS links to units A C and D we show unit B s configuration below It can be seen that there are 3 entries in the WDS Connections list The first entry specifies a connection to the Access Point whose SSID is A and that it is to be a WDS router interface with Router IP address 169 254 ...

Страница 34: ...s unit B therefore we wish to have the WDS interface link to unit D bridged with the default interface Because we don t specify a router IP address for the third entry the RM 240 automatically bridges this interface with the default wire less interface The routing rule for directing traffic to unit A can be seen to specify 192 168 0 0 as the destination address the network address of unit A becaus...

Страница 35: ...D Specify the SSID of the Access Point s to establish a WDS link with Leave this field blank if you wish to nominate the Access Point by MAC address only however in that case the Access Point must not have SSID broadcast disabled MAC Address Specify the MAC address of an Access Point to estab lish a WDS link with Leave this field blank if you wish to connect to any Access Point with the nominated ...

Страница 36: ... as their default gateway i e they require no routing rules be configured However for the Access Point to be able to deliver traffic to LAN B and LAN C it needs to have routing rules configured that specify the respective RM 240 client routers as next hop routers i e gateways to networks B and C Note that devices on LAN A should specify the RM 240 Access Point as their default gateway An alternati...

Страница 37: ... lists one of MAC Addresses and another listing IP protocol details Each list may be set as either a blacklist to block traffic for listed devices and protocols or as a whitelist to allow traffic for listed devices and protocols The Filter operates on two rules listed below 1 A Blacklist has priority over a whitelist Traffic matching detail in a blacklist will be dis carded if it also appears in a...

Страница 38: ...ts configuration how ever will load up at IP address 192 168 0 1XX netmask 255 255 255 0 with the radio and filter disabled The XX in the IP address is the last two digits of the serial number Configuration webpages will still show the original configuration No changes are made to configuration until the user saves changes To resume normal operation set the dipswitch to RUN and cycle power MAC Add...

Страница 39: ...he sending device does not have a fixed IP to MAC Address translation table entry i e whenever the device may need to send an ARP request to determine the MAC address of a device with a known IP Address An ICMP filter is needed to allow disallow pings 3 13 Serial Port Configuration The RM 240 has an RS 232 and RS 485 port for serial communications These ports may be used for different purposes The...

Страница 40: ... PPP server is enabled This may also be used to con figure the module Settings whilst in SETUP mode are as follows username user password is user Serial baud rate 38 4 kbit s Hardware flow control Local address 192 168 123 123 Remote address 192 168 123 124 To configure Windows XP to establish a PPP connection to a RM 240 in SETUP mode follow these steps 1 On Network Connections in Windows XP sele...

Страница 41: ...e client When configured as Client the module will automatically attempt to connect to the specified remote server When configured as Multicast Group the module will broad cast data to all members of the same Multicast Group Some of the possible Serial Gateway topologies are illustrated below As can be seen it is possible for serial data from a RM 240 to be transferred to one or more RM 240 serial...

Страница 42: ...tes available range from 110 bit s to a maximum of 115 2 kbit s Data Bits Parity Stop Bits The data format desired Data formats of 8N1 7E1 7O1 7E2 7O2 are supported Character Timeout Enter the maximum delay in msec between received serial characters before packet is sent via network Server When configured as Server the module will wait for a connection to be initiated by a remote client Listen Por...

Страница 43: ...s the Modbus TCP queries received from the Master into Modbus RTU queries and forwards these over the RS232 port to the Slave When the serial response to the query arrives from the Slave it is converted to a Modbus TCP response and forwarded via the network to the Modbus TCP Master If no response was received seri ally by the RM 240 within the configured Response Timeout the RM 240 will initiate a...

Страница 44: ...provide a status output of the module communications If the RM 240 disassociates from another unit that is there is no wire less link you can configure the digital output to turn ON set or OFF drop 3 15 Module Information Configuration Module Information Webpage Fields This configuration page is primarily for information purposes With the exception of the password the information entered here is d...

Страница 45: ...ade If the remote module is config ured as a Router enter the wireless IP address of the router not the Ethernet address Care must be taken if modifying the configuration of a module remotely If the Radio Configuration is changed some changes made may cause loss of the radio link and therefore the network connection It is advisable to determine path of the links to the modules you wish to modify a...

Страница 46: ...mode Power up unit and wait for LINK led to cease flashing Adjust PC network settings Set Configuration PC network card with network setting of IP address 192 168 0 1 netmask 255 255 255 0 Open configuration webpage with Internet Explorer at address http 192 168 0 1XX where XX is the last two digits of the serial number When prompted for password enter default username user and password user Enter...

Страница 47: ...orer at address http 192 168 0 200 When prompted for password enter default username user and password user Enter Network and select Operating Mode as Access Point Select Device Mode as Bridge Change the IP address to 192 168 0 200 Enter a System Address SSID string Select the Radio Encryption required and enter the system keys Make a record of these Encryption keys and use these on all modules in...

Страница 48: ... cable between PC and RM 240 Ensure configuration PC and RM 240 are setup to communicate on the same network Set dipswitch to SETUP Power up unit and wait for LINK led to cease flashing Adjust PC network settings Set Configuration PC network card with network setting of IP address 192 168 0 1 net mask 255 255 255 0 Open configuration webpage with Internet Explorer at address http 192 168 0 1XX Whe...

Страница 49: ...ress to 169 254 102 53 network mask 255 255 255 0 Click on button Save to Flash and Reset Webpage will display that message indicating details are being written to flash Wait for RM 240 to reboot before removing power Extending range of a network with a Repeater hop Configure units as described in Section Extending a wired network Place the Access Point at the remote intermediate repeater location...

Страница 50: ...ates correct operation of the unit This LED turns red on failure as described above When the OK LED turns red shutdown state is indicated On processor failure or on failure during startup diagnostics the unit shuts down and remains in shutdown until the fault is rectified Boot Loader LED Indication during Startup Serial LAN LINK ACTIVE Comment Orange Orange Orange RED Initial Power Up bootload Ini...

Страница 51: ...transmissions that are being received As Beacon messages occur very frequently they have been filtered out from the Monitor Communications display for convenience Monitor communications lists the frame type of each transmission and various statistics of each transmission along with a timestamp Communications can only be monitored on one channel at a time the channel that is used for monitoring can...

Страница 52: ...u are trying to reach is actually operating If for example a user can t ping a host then the user will be unable to send files to that host Ping operates by sending a packet to a des ignated address and waiting for a response The basic operation of Ping can be performed by following these steps in any Windows operating system Click on the Start Menu and select Run Type in cmd and enter you should ...

Страница 53: ... and their usages available for use 4 4 3 ARP Displays and modifies the IP to Physical address translation tables used by Address Resolution Protocol ARP Once a remote computer has been pinged this can be used to see the IP address MAC address of the remote computer It will also show any other devices on the network that it may be connected to The command used is Arp a It shows the PC s direct IP ...

Страница 54: ...t IP 192 168 2 50 Gateway IP 192 168 0 1 Subnet Mask 255 255 255 0 Wireless IP 192 168 2 50 Subnet Mask 255 255 255 0 Access Point Router Settings Network B Settings Gateway IP 192 168 0 1 IP Address 192 168 2 201 Ethernet IP 192 168 0 191 Subnet Mask 255 255 255 0 Subnet Mask 255 255 255 0 Gateway IP 192 168 2 51 Wireless IP 192 168 2 051 Subnet Mask 255 255 255 0 In the Network A PC a routing ru...

Страница 55: ...t models available 100mW 20dBm or 300mW 25dBm Channels 11 x 5MHz First channel centre at 2 412 GHz Receiver sensitivity 8 FER 96dBm 1Mb s 91dBm 11Mb s Antenna Connector Female SMA coaxial Two connectors for signal diversity Wireless data rate con figurable 1 to 11Mb s Auto function determines fastest rate within user configured fade margin Serial Ports RS232 Port DB9 female DCE RTS CTS DTR DCD har...

Страница 56: ...4g_x x bin gz and firmware application file epm_E24g_x x bin gz using the Browse buttons in the FlashUpdate program 6 Connect PC to RM 240 RS 232 serial port with straight though serial cable 7 Select COM port connected to RM 240 in the FlashUpdate program 8 Connect PC to RM 240 Ethernet port with straight through Ethernet cable This will usually be a blue color 9 Switch dip switch on RM 240 to SE...

Страница 57: ...s crossover If an eight wire cable was being used for instance the signal would start on pin one at one end of the cable and end up on pin eight at the other end They cross over from one side to the other CSMA CA CSMA CA is a listen before talk method of minimizing but not eliminating collisions caused by simultaneous transmission by multiple radios IEEE 802 11 states collision avoidance meth od r...

Страница 58: ...ers like 107 22 55 26 Every website has its own specific IP address on the Internet DSL Various technology protocols for high speed data voice and video transmission over ordinary twisted pair copper POTS Plain Old Telephone Service telephone wires Encryption key An alphanumeric letters and or numbers series that enables data to be encrypted and then decrypted so it can be safely shared among memb...

Страница 59: ...nly mediates wireless network traffic in the immediate neighborhood but also provides communication with the wired network See Ad Hoc and AP I O The term used to describe any operation program or device that transfers data to or from a computer Internet appliance A computer that is intended primarily for Internet access is simple to set up and usually does not support installation of third party s...

Страница 60: ...ISDN uses standard POTS copper wiring to deliver voice data or video ISO Network Model A network model developed by the International Standards Organization ISO that consists of seven different levels or layers By standardizing these layers and the interfaces in between different portions of a given protocol can be modified or changed as technologies advance or systems requirements are altered The...

Страница 61: ...either works without wires Wi Fi or attaches to a network cable to provide two way communication between the computer and network devices such as a hub or switch Most office wired NICs operate at 10 Mbit s Ethernet 100 Mbit s Fast Ethernet or 10 100 Mbit s dual speed High speed Gigabit and 10 Gigabit NIC cards are also available See PC Card Proxy server Used in larger companies and organizations t...

Страница 62: ...he packets that a message is divided into for efficient routing through the Internet For example when a web page is down loaded from a web server the TCP program layer in that server divides the file into packets numbers the packets and then for wards them individually to the IP program layer Although each packet has the same destination IP address it may get routed differently through the network...

Страница 63: ...lso used to distinguish between phone based data networks and Wi Fi Phone networks are considered WANs and Wi Fi networks are considered Wireless Local Area Networks WLANs WEP Basic wireless security provided by Wi Fi In some instances WEP may be all a home or small business user needs to protect wireless data WEP is available in 40 bit also called 64 bit or in 108 bit also called 128 bit encrypti...

Страница 64: ...2 80 01 info westermo se Westermo OnTime AS Gladsvei 20 0489 Oslo Norway Phone 47 22 09 03 03 Fax 47 22 09 03 10 E mail contact ontimenet com Westermo Data Communications Ltd Talisman Business Centre Duncan Road Park Gate Southampton SO31 7GA Phone 44 0 1489 580 585 Fax 44 0 1489 580586 E Mail sales westermo co uk Westermo Data Communications GmbH Goethestraße 67 68753 Waghäusel Tel 49 0 7254 9540...

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